Respiratory system - Human

Respiratory system

The lungs and respiratory system allow us to breathe. They bring oxygen into our bodies (called inspiration, or inhalation) and send carbon dioxide out (called expiration, or exhalation).

This exchange of oxygen and carbon dioxide is called respiration.

Parts of Respiratory system 

The respiratory system includes the

nose, 

mouth, 

throat, 

voice box, 

windpipe, and 

lungs.

Air enters the respiratory system through the nose or the mouth. If it goes in the nostrils (also called nares), the air is warmed and humidified. Tiny hairs called cilia protect the nasal passageways and other parts of the respiratory tract, filtering out dust and other particles that enter the nose through the breathed air.

The two openings of the airway (the nasal cavity and the mouth) meet at the pharynx, or throat, at the back of the nose and mouth. The pharynx is part of the digestive system as well as the respiratory system because it carries both food and air.

At the bottom of the pharynx, this pathway divides in two, one for food — the esophagus, which leads to the stomach — and the other for air. The epiglottis, a small flap of tissue, covers the air-only passage when we swallow, keeping food and liquid from going into the lungs.

The larynx, or voice box, is the top part of the air-only pipe. This short tube contains a pair of vocal cords, which vibrate to make sounds.

The trachea, or windpipe, is the continuation of the airway below the larynx. The walls of the trachea are strengthened by stiff rings of cartilage to keep it open. The trachea is also lined with cilia, which sweep fluids and foreign particles out of the airway so that they stay out of the lungs.

At its bottom end, the trachea divides into left and right air tubes called bronchi, which connect to the lungs. Within the lungs, the bronchi branch into smaller bronchi and even smaller tubes called bronchioles. Bronchioles end in tiny air sacs called alveoli, where the exchange of oxygen and carbon dioxide actually takes place. Each person has hundreds of millions of alveoli in their lungs. This network of alveoli, bronchioles, and bronchi is known as the bronchial tree.

The lungs also contain elastic tissues that allow them to inflate and deflate without losing shape. They're covered by a thin lining called the pleura.

The chest cavity, or thorax, is the airtight box that houses the bronchial tree, lungs, heart, and other structures. The top and sides of the thorax are formed by the ribs and attached muscles, and the bottom is formed by a large muscle called the diaphragm. The chest walls form a protective cage around the lungs and other contents of the chest cavity.

The Gas-exchange Region

The gas-exchange region comprises three compartments: air, blood, and tissue. Whereas air and blood are continuously replenished, the function of the tissue compartment is twofold: it provides the stable supporting framework for the air and blood compartments, and it allows them to come into close contact with each other (thereby facilitating gas exchange) while keeping them strictly confined. 

The respiratory gases diffuse from air to blood, and vice versa, through the 140 square metres of internal surface area of the tissue compartment. 

The gas-exchange tissue proper is called the pulmonary parenchyma, while the supplying structures, conductive airways, lymphatics, and non-capillary blood vessels belong to the non-parenchyma.

The gas-exchange region begins with the alveoli of the first generation of respiratory bronchioles. Distally, the frequency of alveolar outpocketings increases rapidly, until after two to four generations of respiratory bronchioles, the whole wall is formed by alveoli. 

The airways are then called alveolar ducts and, in the last generation, alveolar sacs. 

Alveoli

On average, an adult human lung has about 480 million alveoli. They are polyhedral structures, with a diameter of about 250 to 300 μm (1 μm = 0.000039 inch), and open on one side, where they connect to the airway. 

The alveolar wall, called the interalveolar septum, is common to two adjacent alveoli. It contains a dense network of capillaries, the smallest of the blood vessels, and a skeleton of connective tissue fibers. 

The fiber system is interwoven with the capillaries and particularly reinforced at the alveolar entrance rings. The capillaries are lined by flat endothelial cells with thin cytoplasmic extensions. 

The interalveolar septum is covered on both sides by the alveolar epithelial cells. A thin, squamous cell type, the type I pneumocyte, covers between 92 and 95 percent of the gas-exchange surface; a second, more cuboidal cell type, the type II pneumocyte, covers the remaining surface. 

The type I cells form, together with the endothelial cells, the thin air–blood barrier for gas exchange; the type II cells are secretory cells. 

Type II pneumocytes produce a surface-tension-reducing material, the pulmonary surfactant, which spreads on the alveolar surface and prevents the tiny alveolar spaces from collapsing. 

Before it is released into the airspaces, pulmonary surfactant is stored in the type II cells in the form of lamellar bodies. 

These granules are the conspicuous ultrastructural features of this cell type. On top of the epithelium, alveolar macrophages creep around within the surfactant fluid. 

They are large cells, and their cell bodies abound in granules of various content, partly foreign material that may have reached the alveoli, or cell debris originating from cell damage or normal cell death. 

Ultimately, the alveolar macrophages are derived from the bone marrow, and their task is to keep the air–blood barrier clean and unobstructed. 

The tissue space between the endothelium of the capillaries and the epithelial lining is occupied by the interstitium. It contains connective tissue and interstitial fluid. 

The connective tissue comprises a system of fibers, amorphous ground substance, and cells (mainly fibroblasts), which seem to be endowed with contractile properties. The fibroblasts are thought to control capillary blood flow or, alternatively, to prevent the accumulation of extracellular fluid in the interalveolar septa. 

If for some reason the delicate fluid balance of the pulmonary tissues is impaired, an excess of fluid accumulates in the lung tissue and within the airspaces. 

This pathological condition is called pulmonary edema. As a consequence, the respiratory gasses must diffuse across longer distances, and proper functioning of the lung is severely jeopardized.

Control of Breathing

Breathing is an automatic and rhythmic act produced by networks of neurons in the hindbrain (the pons and medulla). The neural networks direct muscles that form the walls of the thorax and abdomen and produce pressure gradients that move air into and out of the lungs. 

The respiratory rhythm and the length of each phase of respiration are set by reciprocal stimulatory and inhibitory interconnection of these brain-stem neurons.

An important characteristic of the human respiratory system is its ability to adjust breathing patterns to changes in both the internal milieu and the external environment. 

Ventilation increases and decreases in proportion to swings in carbon dioxide production and oxygen consumption caused by changes in metabolic rate. 

The respiratory system is also able to compensate for disturbances that affect the mechanics of breathing, such as the airway narrowing that occurs in an asthmatic attack. 

Breathing also undergoes appropriate adjustments when the mechanical advantage of the respiratory muscles is altered by postural changes or by movement.

This flexibility in breathing patterns in large part arises from sensors distributed throughout the body that send signals to the respiratory neuronal networks in the brain. 

Chemoreceptors detect changes in blood oxygen levels and change the acidity of the blood and brain. 

Mechanoreceptors monitor the expansion of the lung, the size of the airway, the force of respiratory muscle contraction, and the extent of muscle shortening.

Although the diaphragm is the major muscle of breathing, its respiratory action is assisted and augmented by a complex assembly of other muscle groups. 

Intercostal muscles inserting on the ribs, the abdominal muscles, and muscles such as the scalene and sternocleidomastoid that attach both to the ribs and to the cervical spine at the base of the skull also play an important role in the exchange of air between the atmosphere and the lungs. 

In addition, laryngeal muscles and muscles in the oral and nasal pharynx adjust the resistance of movement of gasses through the upper airways during both inspiration and expiration. 

Although the use of these different muscle groups adds considerably to the flexibility of the breathing act, they also complicate the regulation of breathing. These same muscles are used to perform a number of other functions, such as speaking, chewing and swallowing, and maintaining posture. 

Perhaps because the “respiratory” muscles are employed in performing nonrespiratory functions, breathing can be influenced by higher brain centers and even controlled voluntarily to a substantial degree. 

An outstanding example of voluntary control is the ability to suspend breathing by holding one’s breath. 

Input into the respiratory control system from higher brain centers may help optimize breathing so that not only are metabolic demands satisfied by breathing but ventilation also is accomplished with minimal use of energy.

Central Organization of Respiratory Neurons

The respiratory rhythm is generated within the pons and medulla oblongata. Three main aggregations of neurons are involved: a group consisting mainly of inspiratory neurons in the dorsomedial medulla, a group made up of inspiratory and expiratory neurons in the ventrolateral medulla, and a group in the rostral pons consisting mostly of neurons that discharge in both inspiration and expiration. 

It is thought that the respiratory cycle of inspiration and expiration is generated by synaptic interactions within these groups of neurons.

The inspiratory and expiratory medullary neurons are connected to projections from higher brain centres and from chemoreceptors and mechanoreceptors; in turn they drive cranial motor neurons, which govern the activity of muscles in the upper airways and the activity of spinal motor neurons, which supply the diaphragm and other thoracic and abdominal muscles. 

The inspiratory and expiratory medullary neurons also receive input from nerve cells responsible for cardiovascular and temperature regulation, allowing the activity of these physiological systems to be coordinated with respiration.

Neurally, inspiration is characterized by an augmenting discharge of medullary neurons that terminates abruptly. After a gap of a few milliseconds, inspiratory activity is restarted, but at a much lower level, and gradually declines until the onset of expiratory neuron activity. 

Then the cycle begins again. The full development of this pattern depends on the interaction of several types of respiratory neurons: inspiratory, early inspiratory, off-switch, post-inspiratory, and expiratory.

Early inspiratory neurons trigger the augmenting discharge of inspiratory neurons. This increase in activity, which produces lung expansion, is caused by self-excitation of the inspiratory neurons and perhaps by the activity of an as yet undiscovered upstream pattern generator. 

Off-switch neurons in the medulla terminate inspiration, but pontine neurons and input from stretch receptors in the lung help control the length of inspiration. When the vagus nerves are sectioned or pontine centers are destroyed, breathing is characterized by prolonged inspiratory activity that may last for several minutes. This type of breathing, which occasionally occurs in persons with diseases of the brain stem, is called apneustic breathing.

Post-inspiratory neurons are responsible for the declining discharge of the inspiratory muscles that occurs at the beginning of expiration. Mechanically, this discharge aids in slowing expiratory flow rates and probably assists the efficiency of gas exchange. 

It is thought by some that these post-inspiratory neurons have inhibitory effects on both inspiratory and expiratory neurons and therefore play a significant role in determining the length of the respiratory cycle and the different phases of respiration.

As the activity of the post-inspiratory neurons subsides, expiratory neurons discharge and inspiratory neurons are strongly inhibited. There may be no peripheral manifestation of expiratory neuron discharge except for the absence of inspiratory muscle activity, although in upright humans the lower expiratory intercostal muscles and the abdominal muscles may be active even during quiet breathing. 

Moreover, as the demand to breathe increases (for example, with exercise), more expiratory intercostal and abdominal muscles contract. As expiration proceeds, the inhibition of the inspiratory muscles gradually diminishes and inspiratory neurons resume their activity.

Chemoreceptors 

One way in which breathing is controlled is through feedback by chemoreceptors. 

There are two kinds of respiratory chemoreceptors: arterial chemoreceptors, which monitor and respond to changes in the partial pressure of oxygen and carbon dioxide in the arterial blood, and central chemoreceptors in the brain, which respond to changes in the partial pressure of carbon dioxide in their immediate environment. 

Ventilation levels behave as if they were regulated to maintain a constant level of carbon dioxide partial pressure and to ensure adequate oxygen levels in the arterial blood. 

Increased activity of chemoreceptors caused by hypoxia or an increase in the partial pressure of carbon dioxide augments both the rate and depth of breathing, which restores partial pressures of oxygen and carbon dioxide to their usual levels. 

On the other hand, too much ventilation depresses the partial pressure of carbon dioxide, which leads to a reduction in chemoreceptor activity and a diminution of ventilation. 

During sleep and anesthesia, lowering carbon dioxide levels three to four millimeters of mercury below values occurring during wakefulness can cause a total cessation of breathing (apnea).

Peripheral chemoreceptors

Hypoxia, or the reduction of oxygen supply to tissues to below physiological levels (produced, for example, by a trip to high altitudes), stimulates the carotid and aortic bodies, the principal arterial chemoreceptors. 

The two carotid bodies are small organs located in the neck at the bifurcation of each of the two common carotid arteries into the internal and external carotid arteries. 

This organ is extraordinarily well perfused and responds to changes in the partial pressure of oxygen in the arterial blood flowing through it rather than to the oxygen content of that blood (the amount of oxygen chemically combined with hemoglobin). 

The sensory nerve from the carotid body increases its firing rate hyperbolically as the partial pressure of oxygen falls. In addition to responding to hypoxia, the carotid body increases its activity linearly as the partial pressure of carbon dioxide in arterial blood is raised. 

This arterial blood parameter rises and falls as air enters and leaves the lungs, and the carotid body senses these fluctuations, responding more to rapid than to slow changes in the partial pressure of carbon dioxide. 

Larger oscillations in the partial pressure of carbon dioxide occur with breathing as metabolic rate is increased. The amplitude of these fluctuations, as reflected in the size of carotid body signals, may be used by the brain to detect changes in the metabolic rate and to produce appropriate adjustment in ventilation.

The carotid body communicates with medullary respiratory neurons through sensory fibers that travel with the carotid sinus nerve, a branch of the glossopharyngeal nerve. Microscopically, the carotid body consists of two different types of cells. 

The type I cells are arranged in groups and are surrounded by type II cells. 

The type II cells are generally not thought to have a direct role in chemoreception. Fine sensory nerve fibers are found in juxtaposition to type I cells, which, unlike type II cells, contain electron-dense vesicles. Acetylcholine, catecholamines, and neuropeptides such as enkephalins, vasoactive intestinal polypeptide, and substance P, are located within the vesicles. It is thought that hypoxia and hypercapnia (excessive carbon dioxide in the blood) cause the release of one or more of these neuroactive substances from the type I cells, which then act on the sensory nerve. 

It is possible to interfere independently with the responses of the carotid body to carbon dioxide and oxygen, which suggests that the same mechanisms are not used to sense or transmit changes in oxygen or carbon dioxide. 

The aortic bodies located near the arch of the aorta also respond to acute changes in the partial pressure of oxygen, but less well than the carotid body responds to changes in the partial pressure of carbon dioxide. The aortic bodies are responsible for many of the cardiovascular effects of hypoxia.

Central chemoreceptors

Carbon dioxide is one of the most powerful stimulants of breathing. As the partial pressure of carbon dioxide in arterial blood rises, ventilation increases nearly linearly. 

Ventilation normally increases by two to four liters per minute with each one millimeter of mercury increase in the partial pressure of carbon dioxide. 

Carbon dioxide increases the acidity of the fluid surrounding the cells but also easily passes into cells and thus can make the interior of cells more acidic. 

It is not clear whether the receptors respond to the intracellular or extracellular effects of carbon dioxide or acidity.

Even if both the carotid and aortic bodies are removed, inhaling gasses that contain carbon dioxide stimulates breathing. This observation shows that there must be additional receptors that respond to changes in the partial pressure of carbon dioxide. 

Current thinking places these receptors near the undersurface (ventral part) of the medulla. However, microscopic examination has not conclusively identified specific chemoreceptor cells in this region. 

The same areas of the ventral medulla also contain vasomotor neurons that are concerned with the regulation of blood pressure. 

Some investigators suspect that respiratory responses produced at the ventral medullary surface are direct and are caused by interference with excitatory and inhibitory inputs to respiration from these vasomotor neurons. 

They further suspect that respiratory chemoreceptors that respond to carbon dioxide are more diffusely distributed in the brain.

Hematopoiesis

Hematopoiesis

Hematopoiesis is the production of all of the cellular components of blood and blood plasma. It occurs within the hematopoietic system, which includes organs and tissues such as the bone marrow, liver, and spleen.

Simply, hematopoiesis is the process through which the body manufactures blood cells. It begins early in the development of an embryoTrusted Source, well before birth, and continues for the life of an individual.

It’s easier to remember what hematopoiesis is when you consider its roots. Hematopoiesis is derived from two Greek words:

Haîma: Blood.

Poiēsis: To make something.

Put these words together, and you get hematopoiesis, the process of making blood. Hematopoiesis is also called hemopoiesis, hematogenesis and hemogenesis.

The blood is made up of more than 10 different cell types. Each of these cell types falls into one of three broad categories:

1. Red blood cells (erythrocytes): These transport oxygen and hemoglobin throughout the body.

2. White blood cells (leukocytes): These support the immune system. There are several different types of white blood cells:

a. Lymphocytes: Including T cells and B cells, which help fight some viruses and tumors.

b. Neutrophils: These help fight bacterial and fungal infections.

c. Eosinophils: These play a role in the inflammatory response, and help fight some parasites.

d. Basophils: These release the histamines necessary for the inflammatory response.

e. Macrophages: These engulf and digest debris, including bacteria.

3. Platelets (thrombocytes): These help the blood to clot.

Current research endorses a theory of hematopoiesis called the monophyletic theory. This theory says that one type of stem cell produces all types of blood cells.

Production place:

Hematopoiesis occurs in many places:

Hematopoiesis in the embryo:

Sometimes called primitive hematopoiesis Trusted Source, hematopoiesis in the embryo produces only red blood cells that can provide developing organs with oxygen. At this stage in development, the yolk sac, which nourishes the embryo until the placenta is fully developed, controls hematopoiesis.

As the embryo continues to develop, the hematopoiesis process moves to the liver, the spleen, and bone marrow, and begins producing other types of blood cells.

In adults, hematopoiesis of red blood cells and platelets occurs primarily in the bone marrow. In infants and children, it may also continue in the spleen and liver.

The lymph system, particularly the spleen, lymph nodes, and thymus, produces a type of white blood cell called lymphocytes. Tissue in the liver, spleen, lymph nodes and some other organs produce another type of white blood cells, called monocytes.

The process of hematopoiesis:

The rate of hematopoiesis depends on the body’s needs. The body continually manufactures new blood cells to replace old ones. About 1 percent of the body’s blood cells must be replaced every day.

White blood cells have the shortest life span, sometimes surviving just a few hours to a few days, while red blood cells can last up to 120 days or so.

The process of hematopoiesis begins with an unspecialized stem cell. This stem cell multiplies, and some of these new cells transform into precursor cells. These are cells that are destined to become a particular type of blood cell but are not yet fully developed. However, these immature cells soon divide and mature into blood components, such as red and white blood cells, or platelets.

Although researchers understand the basics of hematopoiesis, there is an on-ongoing scientific debate about how the stem cells that play a role in hematopoiesis are formed.

Hematopoiesis begins with an originator cell common to all blood cell types. It’s called a hematopoietic stem cell (HSC). An HSC develops into a precursor cell, or “blast” cell. A precursor cell is on track to become a specific type of blood cell, but it’s still in the early stages. A precursor cell goes through several cell divisions and changes before it becomes a fully mature blood cell.

The specific types of hematopoiesis include:

Erythropoiesis: Red blood cell production.

Leukopoiesis: White blood cell production.

Thrombopoiesis: Platelet production.

With each change, an originator cell becomes more specialized — less like a stem cell and more like a red blood cell, white blood cell or platelet.

Types:

Each type of blood cell follows a slightly different path of hematopoiesis. All begin as stem cells called multipotent hematopoietic stem cells (HSC). From there, hematopoiesis follows two distinct pathways.

Trilineage hematopoiesis refers to the production of three types of blood cells: platelets, red blood cells, and white blood cells. Each of these cells begins with the transformation of HSC into cells called common myeloid progenitors (CMP).

After that, the process varies slightly. At each stage of the process, the precursor cells become more organized:

Red blood cells and platelets

Red blood cells: CMP cells change five times before finally becoming red blood cells, also known as erythrocytes.

Platelets: CMP cells transform into three different cell types before becoming platelets.

White blood cells: 

There are several types of white blood cells, each following an individual path during hematopoiesis. All white blood cells initially transform from CMP cells into myeoblasts. After that, the process is as follows:

Before becoming a neutrophil, eosinophil, or basophil, a myeloblast goes through four further stages of development.

To become a macrophage, a myeloblast has to transform three more times.

A second pathway of hematopoiesis produces T and B cells.

T cells and B cells

To produce lymphocytes, MHCs transform into cells called common lymphoid progenitors, which then become lymphoblasts. Lymphoblasts differentiate into infection-fighting T cells and B cells. Some B cells differentiate into plasma cells after exposure to infection.

Hematopoietic Cytokines

Hematopoietic cytokines are a large family of extracellular ligands that stimulate hematopoietic cells to differentiate into eight principle types of blood cells. Numerous cytokines are involved in the regulation of hematopoiesis within a complex network of positive and negative regulators. Some cytokines have very narrow lineage specificities of their actions, while many others have rather broad and overlapping specificity ranges.

Listed within this section are the cytokines whose predominant action appears to be the stimulation or regulation of hematopoietic cells. This includes GM-CSF, G-CSF, M-CSF, interleukins, EPO and TPO. There are a number of other cytokines that exert profound effects on the formation and maturation of hematopoietic cells, which include stem cell factor (SCF), flt-3/flk-2 ligand (FL) and leukemia inhibitory factor (LIF). Other cytokines or ligands such as jagged-1, transforming growth factor-β (TGF-β) and tumor necrosis factor-α (TNF-α) also play significant roles in modulating hematopoiesis.

Impact on Health: 

Some blood disorders can affect healthy blood cells in the blood, even when hematopoiesis occurs.

For example, cancers of the white blood cells such as leukemia and lymphoma can alter the number of white blood cells in the bloodstream. Tumors in hematopoietic tissue that produces blood cells, such as bone marrow can affect blood cell counts.

The aging process can increase the amount of fat present in the bone marrow. This increase in fat can make it harder for the marrow to produce blood cells. If the body needs additional blood cells due to an illness, the bone marrow is unable to stay ahead of this demand. This can cause anemia, which occurs when the blood lacks hemoglobin from red blood cells.

Conclusion: 

Hematopoiesis is a constant process that produces a massive number of cells. Estimates vary, and the precise number of cells depends on individual needs. But in a typical day, the body might produce 200 billion red blood cells, 10 million white blood cells, and 400 billion platelets.

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Human Skeletal System

Human Skeletal system:

The skeletal system is the organ system that provides an internal framework for the human body. 

Why do you need a skeletal system? Try to imagine what you would look like without it. You would be a soft, wobbly pile of skin containing muscles and internal organs but no bones. You might look something like a very large slug. Not that you would be able to see yourself — folds of skin would droop down over your eyes and block your vision because of your lack of skull bones. You could push the skin out of the way if you could only move your arms, but you need bones for that as well.

Components of Skeletal system:

The skeletal system includes 206 bones. Bones are organs made of dense connective tissues, mainly the tough protein collagen. Bones contain blood vessels, nerves, and other tissues. 

Bones are hard and rigid due to deposits of calcium and other mineral salts within their living tissues. Locations, where two or more bones meet, are called joints. 

Many joints allow bones to move like levers. For example, your elbow is a joint that allows you to bend and straighten your arm.

Our bones are made up of a combination of hard minerals, such as calcium that make up about 70 per cent of the body. 

It's hard, smooth, and solid. Inside the cortical bone is a previous, spongy bone material called the trabecular or cancellous bone. 

This way our bones will not break so fluently. At the center of bones is a softer substance called gist.

Bone Attribute:

Bones are calcified connective tissue present in our body. It forms the maximum portion of the skeleton. Bones are dense, semirigid and porus. It consists of an organic matrix and various mineral components inside them. Bones are tough structures. 

Parts of the Skeletal System:

Aside from bones, it also consists of cartilage, tendons, ligaments, and joints. Let us discuss these components -

Bones: They are the most basic part of the skeletal system. Bones are made up of a special kind of tissue known as connective tissue which is made stronger with the help of a mineral called calcium. Inside the hard covering of the bone there is a soft sponge part. This part of the bone is lighter and allows for blood vessels to pass through. At the center of the bone lies the Bone Marrow.  

Bone marrow is a soft spongy substance mainly responsible for the production of blood cells. 

Ligaments: These are tough elastic bands of tissues that are responsible for attaching one bone to another and keeping them stable

Cartilage: Cartilage refers to a smooth protective covering found over joints. It and synovial fluid allows movement in the joints while protecting the bones from rubbing against one another and wearing down. It is also found between the ribs. 

Tendons: Tendons are rope-like structures that join bone to muscle. They also facilitate movement while holding the skeletal system together. They also prevent injury to the muscles by absorbing impact when performing strenuous activities such as jumping

Joints

Joints refer to the areas within the body where two bones meet or connect. They are essential for movement. Some joints allow for a wide range of motion while others allow more restricted or no movement at all. 

Based on the kind of movement they allow, there are three types of joints- 

Fibrous Joints: These allow no movement and are also called immovable joints. For example the ones present in the skull. 

Cartilaginous Joints- These allow for some movement, and thus are called Partially moveable joints. For example the spine

Synovial Joints- these joints have a wide range of motion and can be subdivided into subcategories based on the kind of movement they allow. These are also called movable joints. 

For example the shoulder (Ball and socket joints), the knee (Hinge joint), the neck (pivot joint), etc. They are also filled with a liquid known as the synovial fluid which lubricates the joints and makes movement easier and smoother. 

Axial and Appendicular Skeletons:

The skeleton is traditionally divided into two major parts: the axial skeleton and the appendicular skeleton.

The axial skeleton forms the axis of the body. It includes the skull, vertebral column (spine), and rib cage. The bones of the axial skeleton, along with ligaments and muscles, allow the human body to maintain its upright posture. The axial skeleton also transmits weight from the head, trunk, and upper extremities down the back to the lower extremities. In addition, the bones protect the brain and organs in the chest.

The appendicular skeleton forms the appendages and their attachments to the axial skeleton. It includes the bones of the arms and legs, hands and feet, and shoulder and pelvic girdles. The bones of the appendicular skeleton make possible locomotion and other movements of the appendages. They also protect the major organs of digestion, excretion, and reproduction.

Skull

The skull (also known as cranium) consists of 22 bones which can be subdivided into 8 cranial bones and 14 facial bones.

The main function of the bones of the skull along with the surrounded meninges, is to provide protection and structure.

Protection to the brain (cerebellum, cerebrum, brainstem) and orbits of the eyes. Structurally it provides an anchor for tendinous and muscular attachments of the muscles of the scalp and face. The skull also protects various nerves and vessels that feed and innervate the brain, facial muscles, and skin.

Ribs

There are two classifications of ribs – atypical and typical. The typical ribs have a generalized structure, while the atypical ribs have variations on this structure.

Typical Ribs

The typical rib consists of a head, neck and body:

The head is wedge shaped, and has two articular facets separated by a wedge of bone. One facet articulates with the numerically corresponding vertebra, and the other articulates with the vertebra above.

The neck contains no bony prominences, but simply connects the head with the body. Where the neck meets the body there is a roughed tubercle, with a facet for articulation with the transverse process of the corresponding vertebra.

The body, or shaft of the rib is flat and curved. The internal surface of the shaft has a groove for the neurovascular supply of the thorax, protecting the vessels and nerves from damage.

Atypical Ribs

Ribs 1, 2, 10 11 and 12 can be described as ‘atypical’ – they have features that are not common to all the ribs.

Rib 1 is shorter and wider than the other ribs. It only has one facet on its head for articulation with its corresponding vertebra (there isn’t a thoracic vertebra above it). The superior surface is marked by two grooves, which make way for the subclavian vessels.

Rib 2 is thinner and longer than rib 1, and has two articular facets on the head as normal. It has a roughened area on its upper surface, from which the serratus anterior muscle originates.

Rib 10 only has one facet – for articulation with its numerically corresponding vertebra.

Ribs 11 and 12 have no neck, and only contain one facet, which is for articulation with their corresponding vertebra.

Articulations

The majority of the ribs have an anterior and posterior articulation.

Posterior

All the twelve ribs articulate posteriorly with the vertebra of the spine. Each rib forms two joints:

Costotransverse joint – Between the tubercle of the rib, and the transverse costal facet of the corresponding vertebra.

Costovertebral joint – Between the head of the rib, superior costal facet of the corresponding vertebra, and the inferior costal facet of the vertebra above.

Anterior

The anterior attachment of the ribs vary:

Ribs 1-7 attach independently to the sternum.

Ribs 8 – 10 attach to the costal cartilages superior to them.

Ribs 11 and 12 do not have an anterior attachment and end in the abdominal musculature. Because of this, they are sometimes called ‘floating ribs’.

Vertebral Column

The vertebral column is a series of approximately 33 bones called vertebrae, which are separated by intervertebral discs.

The column can be divided into five different regions, with each region characterised by a different vertebral structure.

In this article, we shall look at the anatomy of the vertebral column – its function, structure, and clinical significance.

Structure of a Vertebrae

All vertebrae share a basic common structure. They each consist of an anterior vertebral body, and a posterior vertebral arch.

Vertebral Body

The vertebral body forms the anterior part of each vertebrae.

It is the weight-bearing component, and vertebrae in the lower portion of the column have larger bodies than those in the upper portion (to better support the increased weight).

The superior and inferior aspects of the vertebral body are lined with hyaline cartilage. Adjacent vertebral bodies are separated by a fibrocartilaginous intervertebral disc.

Vertebral Arch

The vertebral arch forms the lateral and posterior aspect of each vertebrae.

In combination with the vertebral body, the vertebral arch forms an enclosed hole – the vertebral foramen. The foramina of all the vertebrae line up to form the vertebral canal, which encloses the spinal cord.

The vertebral arches have several bony prominences, which act as attachment sites for muscles and ligaments:

Spinous processes – each vertebra has a single spinous process, centered posteriorly at the point of the arch.

Transverse processes – each vertebra has two transverse processes, which extend laterally and posteriorly from the vertebral body. In the thoracic vertebrae, the transverse processes articulate with the ribs.

Pedicles – connect the vertebral body to the transverse processes.

Lamina – connect the transverse and spinous processes.

Articular processes – form joints between one vertebra and its superior and inferior counterparts. The articular processes are located at the intersection of the laminae and pedicles.

Classifications of Vertebrae

Cervical Vertebrae

There are seven cervical vertebrae in the human body. They have three main distinguishing features:

Bifid spinous process – the spinous process bifurcates at its distal end.

Exceptions to this are C1 (no spinous process) and C7 (spinous process is longer than that of C2-C6 and may not bifurcate).

Transverse foramina – an opening in each transverse process, through which the vertebral arteries travel to the brain.

Triangular vertebral foramen

Two cervical vertebrae that are unique. C1 and C2 (called the atlas and axis respectively), are specialized to allow for the movement of the head.

Thoracic Vertebrae

The twelve thoracic vertebrae are medium-sized, and increase in size from superior to inferior. Their specialized function is to articulate with ribs, producing the bony thorax.

Each thoracic vertebra has two ‘demi facets,’ superiorly and inferiorly placed on either side of its vertebral body. The demi facets articulate with the heads of two different ribs.

On the transverse processes of the thoracic vertebrae, there is a costal facet for articulation with the shaft of a single rib. For example, the head of Rib 2 articulates with the inferior demi facet of thoracic vertebra 1 (T1) and the superior demi facet of T2, while the shaft of Rib 2 articulates with the costal facets of T2.

The spinous processes of thoracic vertebrae are oriented obliquely inferiorly and posteriorly. In contrast to the cervical vertebrae, the vertebral foramen of thoracic vertebrae is circular.

Lumbar Vertebrae

There are five lumbar vertebrae in most humans, which are the largest in the vertebral column. They are structurally specialised to support the weight of the torso.

Lumbar vertebrae have very large vertebral bodies, which are kidney shaped. They lack the characteristic features of other vertebrae, with no transverse foramina, costal facets, or bifid spinous processes.

However, like the cervical vertebrae, they have a triangular-shaped vertebral foramen. Their spinous processes are shorter than those of thoracic vertebrae and do not extend inferiorly below the level of the vertebral body.

Their size and orientation permits needle access to the spinal canal and spinal cord (which would not be possible between thoracic vertebrae). Examples include epidural anesthesia administration and lumbar puncture.

Sacrum and Coccyx

The sacrum is a collection of five fused vertebrae. It is described as an inverted triangle, with the apex pointing inferiorly. On the lateral walls of the sacrum are facets for articulation with the pelvis at the sacroiliac joints.

The coccyx is a small bone which articulates with the apex of the sacrum. It is recognised by its lack of vertebral arches. Due to the lack of vertebral arches, there is no vertebral canal.

Separation of S1 from the sacrum is termed “lumbarisation”, while fusion of L5 to the sacrum is termed “sacralisation”. These conditions are congenital abnormalities.

Hip Bones 

The left and right hip bones (innominate bones, pelvic bones) are two irregularly shaped bones that form part of the pelvic girdle – the bony structure that attaches the axial skeleton to the lower limbs.

The hip bones have three main articulations:

Sacroiliac joint – articulation with the sacrum.

Pubic symphysis – articulation between the left and right hip bones.

Hip joint – articulation with the head of femur.

The Ilium

The ilium is the widest and largest of the three parts of the hip bone, and is located superiorly. The body of the ilium forms the superior part of the acetabulum (acetabular roof). Immediately above the acetabulum, the ilium expands to form the wing (or ala).

The wing of the ilium has two surfaces:

Inner surface – has a concave shape, which produces the iliac fossa (site of origin of the iliacus muscle).

External surface (gluteal surface) – has a convex shape and provides attachments to the gluteal muscles.

The superior margin of the wing is thickened, forming the iliac crest. It extends from the anterior superior iliac spine (ASIS) to the posterior superior iliac spine (PSIS).

On the posterior aspect of the ilium there is an indentation known as the greater sciatic notch.

The Pubis

The pubis is the most anterior portion of the hip bone. It consists of a body, superior ramus and inferior ramus (ramus = branch).

Pubic body – located medially, it articulates with the opposite pubic body at the pubic symphysis. Its superior aspect is marked by a rounded thickening (the pubic crest), which extends laterally as the pubic tubercle.

Superior pubic ramus – extends laterally from the body to form part of the acetabulum.

Inferior pubic ramus – projects towards the ischium.

Together, the superior and inferior rami enclose part of the obturator foramen – through which the obturator nerve, artery and vein pass through to reach the lower limb.

The Ischium

The ischium forms the posteroinferior part of the hip bone. Much like the pubis, it is composed of a body, an inferior ramus and superior ramus.

The inferior ischial ramus combines with the inferior pubic ramus forming the ischiopubic ramus, which encloses part of the obturator foramen. The posterorinferior aspect of the ischium forms the ischial tuberosities and when sitting, it is these tuberosities on which our body weight falls.

Near the junction of the superior ramus and body is a posteromedial projection of bone; the ischial spine.

Two important ligaments attach to the ischium:

Sacrospinous ligament – runs from the ischial spine to the sacrum, thus creating the greater sciatic foramen through which lower limb neurovasculature (including the sciatic nerve) transcends.

Sacrotuberous ligament – runs from the sacrum to the ischial tuberosity, forming the lesser sciatic foramen.

Fore Limb 

Limbs are arms and legs in the human body. Forelimbs are the ones that are found in the front part of the body i.e arms. Hind limbs are those that are found in the back part of the body I.e legs.

Human arms have hands which are specialized organs allowing them to grasp and manipulate the objects. Fore limbs are shorter than the hind limbs. This is due to taller bones present in the hind limbs as compared to fore limbs.

Forelimb is located between the wrist and elbow.

The bones present in the forelimbs are — scapula, humerus, radius, ulna, carpals (8), metacarpals (5) and phalanges (14).

The humerus is a single bone present in the upper arm. Ulna and radius are two paired bones. Ulna lies medially and radius lies laterally.

Hind limb

The bones of the limb along with their respective girdles constitute the appendicular skeleton. The hind-limb contains the following bones :- Femur( the longest bone ), Tibia, Fibula, Tarsal, Metatarsal, Patella and Phalanges. Counting the number of bones, these are

Femur 1

Fibula 1

Tibia 1

Patella 1

Tarsals 7

Metatarsals 5

Phalanges 14

Thus, the Hind-limb of humans consists of a total of 30 bones.

Functions of Bones:

1. Bones support our bodies and help us to move.

2. Bones protect our internal organs like the heart, lungs, etc.

3. Some bones produce our red blood cells, white blood cells, and platelets.

4. Certain bones store fats present in our body and provide us when we need them.

5. Bones can also store important minerals for our bodies.

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Love & Chemistry - Neuroendocrine of Love

Love & Chemistry - Neuroendocrine of Love 

Love - Lust, Attraction & Attachment.

Introduction

Scientists in fields ranging from anthropology to neuroscience have been asking this same question (albeit less eloquently) for decades. It turns out the science behind love is both simpler and more complex than we might think.

Google the phrase “biology of love” and you’ll get answers that run the gamut of accuracy. Needless to say, the scientific basis of love is often sensationalized, and as with most science, we don’t know enough to draw firm conclusions about every piece of the puzzle. What we do know, however, is that much of love can be explained by chemistry. So, if there’s really a “formula” for love, what is it, and what does it mean?

Eclipse of the Brain

Think of the last time you ran into someone you find attractive. That may have stammered, your palms may have sweated; you may have said something incredibly asinine and tripped spectacularly while trying to saunter away.

And chances are, your heart was thudding in your chest. It’s no surprise that, for centuries, people thought love (and most other emotions, for that matter) arose from the heart. As it turns out, love is all about the brain – which, in turn, makes the rest of your body go haywire.

According to a team of scientists led by Dr. Helen Fisher at Rutgers, romantic love can be broken down into three categories: lust, attraction, and attachment. Each category is characterized by its own set of hormones stemming from the brain.

Chemicals

Lust

Lust is driven by the desire for sexual gratification. The evolutionary basis for this stems from our need to reproduce, a need shared among all living things. Through reproduction, organisms pass on their genes, and thus contribute to the perpetuation of their species.

The hypothalamus of the brain plays a big role in this, stimulating the production of the sex hormones testosterone and estrogen from the testes and ovaries. 

While these chemicals are often stereotyped as being “male” and “female,” respectively, both play a role in men and women. As it turns out, testosterone increases libido in just about everyone. 

The effects are less pronounced with estrogen, but some women report being more sexually motivated around the time they ovulate, when estrogen levels are highest.

Attraction

Meanwhile, attraction seems to be a distinct, though closely related, phenomenon. While we can certainly lust for someone we are attracted to, and vice versa, one can happen without the other. Attraction involves the brain pathways that control “reward” behavior, which partly explains why the first few weeks or months of a relationship can be so exhilarating and even all-consuming.

Dopamine

Dopamine, produced by the hypothalamus, is a particularly well-publicized player in the brain’s reward pathway – it’s released when we do things that feel good to us. In this case, these things include spending time with loved ones and having sex.

High levels of dopamine and a related hormone, norepinephrine, are released during attraction. These chemicals make us giddy, energetic, and euphoric, even leading to decreased appetite and insomnia – which means you actually can be so “in love” that you can’t eat and can’t sleep. 

In fact, norepinephrine, also known as noradrenalin, may sound familiar because it plays a large role in the fight or flight response, which kicks into high gear when we’re stressed and keeps us alert. 

Brain scans of people in love have actually shown that the primary “reward” centers of the brain, including the ventral tegmental area and the caudate nucleus, fire like crazy when people are shown a photo of someone they are intensely attracted to, compared to when they are shown someone they feel neutral towards (like an old high school acquaintance).

Finally, attraction seems to lead to a reduction in serotonin, a hormone that’s known to be involved in appetite and mood. Interestingly, people who suffer from obsessive-compulsive disorder also have low levels of serotonin, leading scientists to speculate that this is what underlies the overpowering infatuation that characterizes the beginning stages of love.

Attachment

Last but not least, attachment is the predominant factor in long-term relationships. While lust and attraction are pretty much exclusive to romantic entanglements, attachment mediates friendships, parent-infant bonding, social cordiality, and many other intimacies as well. The two primary hormones here appear to be oxytocin and vasopressin.

Oxytocin is often nicknamed “cuddle hormone” for this reason. Like dopamine, oxytocin is produced by the hypothalamus and released in large quantities during sex, breastfeeding, and childbirth. 

This may seem like a very strange assortment of activities – not all of which are necessarily enjoyable – but the common factor here is that all of these events are precursors to bonding. 

It also makes it pretty clear why having separate areas for attachment, lust, and attraction is important: we are attached to our immediate family, but those other emotions have no business there (and let’s just say people who have muddled this up don’t have the best track record).

Love Hurts 

This all paints quite the rosy picture of love: hormones are released, making us feel good, rewarded, and close to our romantic partners. But that can’t be the whole story: love is often accompanied by jealousy, erratic behavior, and irrationality, along with a host of other less-than-positive emotions and moods. It seems that our friendly cohort of hormones is also responsible for the downsides of love.

Dopamine, for instance, is the hormone responsible for the vast majority of the brain’s reward pathway – and that means controlling both the good and the bad. We experience surges of dopamine for our virtues and our vices. In fact, the dopamine pathway is particularly well studied when it comes to addiction. 

The same regions that light up when we’re feeling attraction light up when drug addicts take cocaine and when we binge eat sweets. For example, cocaine maintains dopamine signaling for much longer than usual, leading to a temporary “high.” 

In a way, attraction is much like an addiction to another human being. Similarly, the same brain regions light up when we become addicted to material goods as when we become emotionally dependent on our partners. And addicts going into withdrawal are not unlike love-struck people craving the company of someone they cannot see.

The story is somewhat similar for oxytocin: too much of a good thing can be bad. Recent studies on party drugs such as MDMA and GHB shows that oxytocin may be the hormone behind the feel-good, sociable effects these chemicals produce. 

These positive feelings are taken to an extreme in this case, causing the user to dissociate from his or her environment and act wildly and recklessly. Furthermore, oxytocin’s role as a “bonding” hormone appears to help reinforce the positive feelings we already feel towards the people we love. 

That is, as we become more attached to our families, friends, and significant others, oxytocin is working in the background, reminding us why we like these people and increasing our affection for them. 

While this may be a good thing for monogamy, such associations are not always positive. For example, oxytocin has also been suggested to play a role in ethnocentrism, increasing our love for people in our already-established cultural groups and making those unlike us seem more foreign. Thus, like dopamine, oxytocin can be a bit of a double-edged sword.

And finally, what would love be without embarrassment? Sexual arousal (but not necessarily attachment) appears to turn off regions in our brain that regulate critical thinking, self-awareness, and rational behavior, including parts of the prefrontal cortex. In short, love makes us dumb. 

Have you ever done something when you were in love that you later regretted? Maybe not. I’d ask a certain star-crossed Shakespearean couple, but it’s a little late for them.

Conclusion

So, in short, there is sort of a “formula” for love. However, it’s a work in progress, and there are many questions left unanswered. 

And, as we’ve realized by now, it’s not just the hormone side of the equation that’s complicated. Love can be both the best and worst thing for you – it can be the thing that gets us up in the morning, or what makes us never want to wake up again. I’m not sure I could define “love” for you if I kept you here for another ten thousand pages.

In the end, everyone is capable of defining love for themselves. And, for better or for worse, if it’s all hormones, maybe each of us can have “chemistry” with just about anyone. But whether or not it goes further is still up to the rest of you.

Biomimetics - A Lesson from the Nature

Biomimetics - A Lesson from the Nature 

Introduction

Biomimetics is the study of nature and natural phenomena to understand the principles of underlying mechanisms, to obtain ideas from nature, and to apply concepts that may benefit science, engineering, and medicine.

Examples of biomimetic studies include fluid-drag reduction swimsuits inspired by the structure of shark’s skin, velcro fasteners modeled on burrs, shape of airplanes developed from the look of birds, and stable building structures copied from the backbone of turban shells. 

If the history of planet Earth was compressed into 1 year, humans would appear in the last 15 minutes of it. Out of those 15 minutes, most recent industrial progress would occur within 1 minute. Despite this small proportion, the industrialization that took place in the last century is much greater than that from the start of mankind. Although the rapid rate of industrialization has helped to prolong life and overcome disease, it has also brought pollution and environmental destruction, which affect human survival itself. In this drift toward industrialization, men have made a continuous effort to create more products that can improve our lives. However, the survival of mankind faces the physical dilemma of living on limited resources. Solutions to the lack of resources and survival problems have not always been clear to us, although the answer can always be found within nature. An interesting method to solve these problems may lie in biomimetics, which uses nature as the ultimate model, standard, and advisor. In recent times, mankind has newly opened its eyes to biomimetic technology, and its efforts are being met with success. This review focuses on recognizing specific examples of biomimetics, their current use, and how they will continue to be used in the future.

Biomimetics: past, current, and future

Definition of biomimetics 

The term “biomimetics” originates from the Greek words “bios” (life) and “mimesis” (to imitate), yet its definition is not as simple as just those two words. More specifically, biomimetics is a creative form of technology that uses or imitates nature to improve human lives.

Concept of biomimetics 

Biomimetics is not a recent study or trend, but the idea of looking into nature for inspiration has been in practical use for a long time. It has been called by different names such as “intellectual structure” in Japan and “smart material” in the USA. Biomimetics is centered on the idea that there is no model better than nature for developing something new and has produced excellent results in productivity and function. This idea has also opened doors to realistic gains by eliminating waste and saving in research expenses.

Field of biomimetics

Humans have heavily impacted nature with industrialization and resource extraction; however, biomimetics can help to avoid this pattern. Biomimetics goes beyond simply using natural properties as the basis for innovation of new products. Such products can be designed to play a part in general industry as well as to provide human convenience in the fields of chemistry, biology, architecture, engineering, medicine, and biomedical engineering. Such a symbiotic relationship plays a critical role in the coexistence of humans with nature, and the extent of its application can be boundless. It is therefore critical to understand these areas and examples for each of them.

History of biomimetics

The history of biomimetics Found easily in everyday life and often used without our knowledge, biomimetics is a broad field with a long history. From knives and axes inspired by the dental structures of currently extinct animals to the strongest cutting-edge carbon nanomaterials, bioengineering has always evolved along with human history.

Leonardo da Vinci’s (1452–1519) work is a fundamental example of biomimicry. He designed a “flying machine” inspired by a bird. In the Far East, General Yi Sun-sin built the turtleship, a warship modeled after a turtle, to fight Japanese raiders during invasions. 

The Wright brothers (1867–1948) took note of the wings of eagles and made a powered airplane that succeeded in human flight for the first time in 1903. Over the next century, the airplane became faster, more stable, and more aerodynamic.

Schmitt was the first to coin the term biomimetics in 1957, and he announced a turning point for biology and technology.

Jack E Steele of NASA, who coined the word bionics in 1960, was also the first to use the word biomimetics in a paper in 1969, which led to the addition of the term to the dictionary in 1974. 

In 1997, Janine M Benyus published her book Biomimicry, which emphasizes that biomimicry is leading the path to a new age of technological development by taking lessons from nature as the groundwork for products, rather than just using it for raw materials.

Janine Benyus and others stepped further to organize a social enterprise called Biomimicry 3.8 to share ideas and concepts of biomimicry and biomimetics as well as to connect interdisciplinary researchers, scientists, artists, engineers, business leaders, and stakeholders.

Biomimicry taxonomy categorizing the research interests of biomimetics.

Research methods for biomimetics The basic research method for biomimetics has six steps, which can be used to apply biomimetics to design, product, service, and agriculture.

Like the sticky substance found in geckos’ feet, the functional possibilities of biologically inspired design should be researched rather than just applying the design as it is used by the organism. Although the discovery or fusion of innovative technology is crucial for increased profits, a simple creative design idea can provide greater convenience for human life.

The function of the organism, the principles under which that function is achieved, and the relationship between these two must be established. Knowledge and application of various materials need to be accumulated through research and database compilation. The relationship between structure and function usually comes from the surface structure, which can be observed by a scanning electron microscopy technique. These fine structures play an important role in the organism and are said to be the first step for biomimetics. The US researchers are using the Biomimicry Taxonomy as a practical database.

The greatest challenge faced by biomimetics is to determine how nano- and microstructures function in their relationship with the organism and the environment, especially if these have not been fully explored yet. Finding substantial examples through the integration of biology, natural history, and materials science is the next step in biomimetic research.

Identifying various functional and environmental adaptation mechanisms of organisms and their energy-minimizing design is the next research frontier. A successful example of this is the antireflective coating that was inspired by the 200 nm structures reflecting visible light rays from a moth’s eye. The nature of new biomimetic materials lies in discovering hierarchical structures and their corresponding functions to remodel them into something we can utilize.

The combination of newly discovered materials with biomimetics research will be a key to understanding their applications and limitations. The morphological and functional uses of the new material must first be understood along with the pros and cons of biomimetics, and the results from their combination have to be unraveled. Active research is being performed on these fronts, but making progress in these areas is realistically a difficult pursuit.

The determined biological material’s structure and the function become the source of innovation for the development of a new material while possibly providing links to other materials. The structure and function of already known materials go through tests and assessments that help them morph and evolve into new materials. By combining them with current advancements in medicine, chemistry, and nanotechnology, we may find novel utilities that may benefit human life.

Examples of biomimetics 

Due to the heterogeneous nature of the cellular microenvironments, biomimetic analytical platforms conveying complex environments in vivo models have been studied to probe the characteristics of cells and their microenvironments. By engineering the microenvironments (ie, microwells), researchers mimicked the cell-to-cell interactions in lymph nodes or other tissues where two types of cells dynamically communicate upon immunological cues. As the biomimetic microenvironments become more elaborated and sophisticated, researchers preparing biomimetic cellular environments will be enlightened and find solutions to the enigmatic relationships between cells and their adjacent microenvironment.

1. Sharkskin = Swimsuit

Sharkskin-inspired swimsuits received a lot of media attention during the 2008 Summer Olympics when the spotlight was shining on Michael Phelps.

Seen under an electron microscope, sharkskin is made up of countless overlapping scales called dermal denticles (or "little skin teeth"). The denticles have grooves running down their length in alignment with water flow. These grooves disrupt the formation of eddies, or turbulent swirls of slower water, making the water pass by faster. The rough shape also discourages parasitic growth such as algae and barnacles.

Scientists have been able to replicate dermal denticles in swimsuits (which are now banned in major competition) and the bottom of boats. When cargo ships can squeeze out even a single percent in efficiency, they burn less bunker oil and don't require cleaning chemicals for their hulls. Scientists are applying the technique to create surfaces in hospitals that resist bacteria growth — the bacteria can't catch hold on the rough surface.

2. Beaver = Wetsuit

Beavers have a thick layer of blubber that keeps them warm while they're diving and swimming in their water environments. But they have another trick up their sleeves for staying toasty. Their fur is so dense that it traps warm pockets of air in between the layers, keeping these aquatic mammals not only warm, but dry.

Engineers at the Massachusetts Institute of Technology thought surfers might appreciate that same ability, and they created a rubbery, fur-like pelts they say could make "bioinspired materials," such as wetsuits.

“We are particularly interested in wetsuits for surfing, where the athlete moves frequently between air and water environments,” says Anette (Peko) Hosoi, a professor of mechanical engineering and associate head of the department at MIT. “We can control the length, spacing, and arrangement of hairs, which allows us to design textures to match certain dive speeds and maximize the wetsuit's dry region.”

3. Burr = Velcro

Velcro The name Velcro, a common hook-and-loop fastener, comes from the French words for velvet, “velour,” and hook, “crochet”. In the early 1940s, Swiss engineer George de Mastral noticed the tendency of the fruit of the burr (Xanthium strumarium) to stick to dog’s hair and used a microscope to observe the hooks on the fruit which attach to animal hair. He discovered that an elliptical fruit with a length of 1 cm had densely packed hook-like projections. These latched onto peoples’ clothing or animals’ hair, allowing seeds to be dispersed widely. Inspired by this burr, de Mastral used nylon to create velcro fasteners. To enhance adhesive abilities, velcro consists of a strip with round loops and a strip with burr-like hooks. For its small surface area, velcro has exceptional adhesive strength and is used extensively as a simple and practical substitute for buttons or hooks in clothing and shoes.

4. Whale = Turbine

Whales have been swimming around the ocean for a long time, and evolution has crafted them into a super-efficient form of life. They are able to dive hundreds of feet below the surface and stay there for hours. They sustain their massive size by feeding on animals smaller than the eye can see, and they power their movement with über-efficient fins and a tail.

Scientists at Duke University, West Chester University and the U.S. Naval Academy discovered that the bumps at the front edge of a whale fin greatly increase its efficiency, reducing drag by 32 percent and increasing lift by 8 percent. Companies are applying the idea to wind turbine blades, cooling fans, airplane wings and propellers.

5. Aircraft

The emergence of airplanes realized the age-long dream of mankind to fly, but it was also a groundbreaking form of transportation. The basic structure of the wings of airplanes consists of a differing sized curved surface on the upper and lower part of the wing that creates hydrodynamic forces explained by the Bernoulli effect. Through this hydrodynamic structure, the velocity of the airstream is faster on the upper part of the wings and slower on the bottom part of the wings. The higher pressure from the bottom of the wings and the speed of the plane enables the 100 ton airplane to fly. This was the principle that led the Wright brothers to succeed in their first flight, but it was also the result of numerous years of biomimetic research on the structure and design of birds’ wings and their feathers. Beyond individual birds, a flock of wild geese fly in a V formation, creating an ascending air current allowing those flying behind to fly with less effort. AIRBUS, a French aviation company, uses these principles to design their planes. Furthermore, birds that fly short and long distances have different feathers and shapes. These insights have been used to design airplanes that have to travel shorter and longer distances in a different manner.

6. Automobiles

Over the most recent decade, automobile design has not only had an influence on the exterior of cars, but also had an influence on their function. The economizing and energy efficient aspects of biomimetics have been adopted in cars as demonstrated by DaimlerChrysler’s prototype bionic concept car 

The exterior of this car is based on the shape of the boxfish, making it stable and aerodynamic. The basic structure of this car consists of a large outward appearance and small wheels, and the design was evaluated through computer simulation to achieve a minimal stress concentration. This car has an average fuel efficiency of 70 mi/gal (23 km/L) and a maximum speed of 190 km/h, making it more fuel efficient than any existing car.

The front of the Japanese bullet train was inspired by a kingfisher’s beak, so that the sonic boom when the train exits a tunnel and air resistance can be minimized while acceleration and energy efficiency can be increased. This idea was taken from the observation that a kingfisher dives perpendicular to the surface of the water when hunting, causing minimal splashing. Since it simulated the rounded beak structure of the kingfisher, the Shinkansen also came to be known as the bullet train. Another example is SkinzWraps, a film inspired by the microprojections on shark skin to repel germs. The use of SkinzWraps in automobiles reduced car pollution and increased fuel efficiency by 18%–20%. It has also been applied to swimsuits, bringing better results for athletes.

7. Architecture

Biomimicry has the longest history of application in architecture. Previous biomimetic technologies are being used to this day and will be developed further. The most notable example of biomimetic architecture is the 6 m-tall termite’s nest in the African grasslands. These nests are built from soil, tree bark, sand, and termite saliva, yet they are firmer than concrete.

Biomimetics in biomedical engineering

With designs originating from organisms, biomimetics has facilitated and improved human life through many convenient products. In the future, biomimetics will have a greater impact through the combination of medicine, science, and biomedical engineering to treat diseases, physical disabilities, and wounds. Regenerative medicine and tissue engineering are particularly promising fields. Principles and functions of biomimetics that can be applied in biomedical engineering are derived from many sources, including how a lizard regenerates its tail and a buckhorn regenerates its horns every year, the adhesive, plegmatical, and regenerative properties of a spider web, and leukocyte adhesion/migration in inflammation.

An example would be a biocompatible medical bandage that can be made compatible with human tissue and integrated with a ubiquitous health care (U-health) system to get real time reports on the granular status of recovery or disease. A biocompatible, short-lived medical bandage or tape can be used to detect signals, allowing us to monitor heart attacks or myocardial infarction that cannot be monitored or detected using current medical devices. Such a bandage would also be compatible with our skin and result in fewer side effects and less irritation despite better attachment. Such function is derived from the foot hair of the gecko, as mentioned previously.

Next-generation biomimetics combines biology with other technology in solving problems. In particular, nanotechnology is becoming a key discipline that will be utilized to help understand the material and its structures along with accelerating development of secondary structure of proteins. Protein-functionalized nanoparticles, peptide-functionalized gold nanoparticles, and carbohydrate-functionalized nanoparticles are areas of nanotechnology that are finding biomimetic applications. Furthermore, biomimetic approaches may open up promising new fields. Various hybrid composites inspired by the nature have been fabricated and used as a template that can regulate biological processes in tissue engineering. Structural biomaterials such as bones or nacres are hierarchically constructed and organized. In order to elucidate the structural complexity of these biomaterials, studies have demonstrated the development of morphological structures of inorganic–organic hybrid materials to mimic biological and structural formations like sponge spicule formation or the nacre (brick-and-mortar) structure of mollusks.

Multifunctional fibrous scaffolds have been developed as native tissue architecture, which have high potential for bone regeneration. One group recently tested nanofibers as a scaffold made of poly D,L-lactide-co-trimethylene carbonate (PLMC). The biomimicking attributes of poly D,L-lactide-co-trimethylene carbonate nanofibers showed enhanced efficacies and efficiencies as scaffold materials for tissue repair and regeneration.

The integration of biomimetics in biomedical engineering is advancing technology in many ways. Painless syringe needles developed by Kansai University (Osaka, Japan) is one example of biomimetics meeting bioengineering to develop a new material to improve medical operations. This group modeled the structure of mosquito mouthparts that are able to extract blood from the host animal with the least amount of nerve irritation. Such needles are used to help diabetics or during surgery to help patients overcome fear of needles. They use a biodegradable polymer, polylactic acid, which makes the needles safer and more practical than traditional microsilicon needles. Such needles can be inserted at particular angles with certain sensitivity to result in painless insertion. Painless needles are a great example of significant contribution to advancement of biomimetics and biomedical engineering.

Conclusion

Biomimetics or biomimicry have been used and advanced even without formal research in many areas. Accumulating creative ideas as a foundation, mankind has accelerated the speed of development and evolution of civilization. However, such rapid industrialization has resulted in environmental pollution and a shortage of natural resources that is threatening the survival and future of humanity. As a result, it has become critical and urgent to find alternative methods to engineer materials, products, and services. Biomimetics is potentially the best method to help us cope with future development of civilization, environmental pollution, and resource shortage threats.