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Organ Systems in Human Body

Updated on September 2, 2011

Names Of Organ Systems in Human Body:-

1:- Circulatory System

2:- Lymphatic System

3:- Digestive System

4:- Endocrine System

5:- Integumentary System

6:- Muscular System

7:- Nervous System

8:- Reproductive System

9:- Respiratory System

10:- Skeletal System

11:- Urinary System


Circulatory System

The circulatory system is made up of the vessels and the muscles that help and control the flow of the blood around the body. This process is called circulation. The main parts of the system are the heart, arteries, capillaries and veins.

As blood begins to circulate, it leaves the heart from the left ventricle and goes into the aorta. The aorta is the largest artery in the body. The blood leaving the aorta is full of oxygen. This is important for the cells in the brain and the body to do their work. The oxygen rich blood travels throughout the body in its system of arteries into the smallest arterioles.

On its way back to the heart, the blood travels through a system of veins. As it reaches the lungs, the carbon dioxide (a waste product) is removed from the blood and replace with fresh oxygen that we have inhaled through the lungs


Lymphatic System

The lymphatic system and the cardiovascular system are closely related structures that are joined by a capillary system. The is important to the body's defense mechanisms. It filters out organisms that cause disease, produces certain white blood cells and generates antibodies. It is also important for the distribution of fluids and nutrients in the body, because it drains excess fluids and protein so that tissues do not swell up. "Lymph" is a milky body fluid that contains a type of white blood cells, called "lymphocytes," along with proteins and fats. Lymph seeps outside the blood vessels in spaces of body tissues and is stored in the "lymphatic" system to flow back into the bloodstream. Through the flow of blood in and out of arteries, and into the veins, and through the lymph nodes and into the lymph, the body is able to eliminate the products of cellular breakdown and bacterial invasion. Two very large areas are of significance in this system - the right lymphatic duct which drains lymph fluid from the upper right quarter of the body above the diaphragm and down the midline, and the thoracic duct, a structure roughly sixteen inches long located in the mediastinum of the pleural cavity which drains the rest of the body. It is through the actions of this system including the spleen, the thymus, lymph nodes and lymph ducts that our body is able to fight infection and to ward off invasion from foreign invaders. Lymph plays an important role in the immune system and in absorbing fats from the intestines. The lymphatic vessels are present wherever there are blood vessels and transport excess fluid to the end vessels without the assistance of any "pumping" action. There are more than 100 tiny, oval structures (called lymph nodes). These are mainly in the neck, groin and armpits, but are scattered all along the lymph vessels. They act as barriers to infection by filtering out and destroying toxins and germs. The largest body of lymphoid tissue in the human body is the spleen.


Digestive System

Your digestive system consists of organs that break down food into components that your body uses for energy and for building and repairing cells and tissues.

Food passes down the throat, down through a muscular tube called the esophagus, and into the stomach, where food continues to be broken down. The partially digested food passes into a short tube called the duodenum (first part of the small intestine). The jejunum and ileum are also part of the small intestine. The liver, the gallbladder, and the pancreas produce enzymes and substances that help with digestion in the small intestine.

The last section of the digestive tract is the large intestine, which includes the cecum, colon, and rectum. The appendix is a branch off the large intestine; it has no known function. Indigestible remains of food are expelled through the anus.


Endocrine System

In physiology, the endocrine system is a system of glands, each of which secretes a type of hormone directly into the bloodstream to regulate the body. The endocrine system is in contrast to the exocrine system, which secretes its chemicals using ducts. It derives from the Greek words endo meaning inside, within, and crinis for secrete. The endocrine system is an information signal system like the nervous system, yet its effects and mechanism are classifiably different. The endocrine system's effects are slow to initiate, and prolonged in their response, lasting for hours to weeks. The nervous system sends information very quickly, and responses are generally short lived. Hormones are substances (chemical mediators) released from endocrine tissue into the bloodstream where they travel to target tissue and generate a response. Hormones regulate various human functions, including Metabolism, growth and development, tissue function, and mood. The field of study dealing with the endocrine system and its disorders is endocrinology, a branch of internal medicine.

Features of endocrine glands are, in general, their ductless nature, their vascularity, and usually the presence of intracellular vacuoles or granules storing their hormones. In contrast, exocrine glands, such as salivary glands, sweat glands, and glands within the gastrointestinal tract, tend to be much less vascular and have ducts or a hollow lumen.

In addition to the specialised endocrine organs mentioned above, many other organs that are part of other body systems, such as the kidney, liver, heart and gonads, have secondary endocrine functions. For example the kidney secretes endocrine hormones such as erythropoietin and renin.

The endocrine system is made up of a series of glands that produce chemicals called hormones. A number of glands that signal each other in sequence is usually referred to as an axis, for example, the hypothalamic-pituitary-adrenal axis.


Integumentary System

The integumantary system contains the largest organ in the human body, the skin. It is also comprised of such extensions of the skin as hair and fingernails. The skin, however, is the most important of these. The skin protects and cushions the body's delicate organs. It also provides the body a physical barrier to keep out foreign materials and to prevent the body from drying out. The skin is made of three separate layers, each with its own particular function.

The Epidermis

The epidermis, as its name suggests, is the outermost layer of the skin. It is comprised of four separate layers of epithelial tissue. The outermost layer of the epidermis is the stratum corneum. It is approximately 20-30 cells thick. The cells here are completely keratinized and dead, and this is what gives the skin its waterproof quality. The next two layers, the stratum granulosum and the stratum lucidum, are siimilar in that they represent an intermediate stage of keratinization. The cell here are not fully keratinized yet, but as the growth of the skin pushes them outward, they will increasingly move towards that state. The deepest layer of the epidermis is the stratum germinativum. The cells here are mitotically active-- that is, they are alive and reproducing. This is where the growth of skin takes place.

The Dermis

The dermis is the second layer of skin, directly beneath the epidermis. Unlike the epidermis, the dermis has its own blood supply. Because of the presence of this blood supply, more complex structures are able to exist here. Sweat glands are present to collect water and various wastes from the bloodstream, and excrete them through pores in the epidermis. The dermis is also the site of hair roots, and it is here where the growth of hair takes place. By the time hair reaches the environment outside of the skin, it is completely dead. The dermis also contains dense connective tissue, made of collagen fibers, which gives the skin much of its elasticity and strength.

The Subcutaneous Layer

Beneath the dermis lies the final layer of skin, the subcutaneous layer. The most notable structures here are the large groupings of adipose tissue. The main function of the subcutaneous layer is therefore to provide a cushion for the delicate organs lying beneath the skin. It also functions to insulate the body to maintain body temperature.


Muscular System

Muscles maintain our posture, allow us to move, breath, circulate our blood and even close our eyes.

Muscle structure

There are three different types of muscle;

Cardiac muscle

Cardiac muscle is the muscle found in the walls of the heart. It contracts to force the blood around the body. Cardiac muscle contracts without stimulation, however, the strength and rate of the contraction is modified by the autonomic nervous system. Cardiac muscle does not tire. The cardiac muscle fibres are short with a single central nucleus; they are striated. The cells join directly together and are connected by connective tissue.

Smooth muscle

Smooth muscle is found in the walls of the internal organs, the walls of blood vessels and the intrinsic (internal) muscles of the eye. Smooth muscle contracts without stimulation, however, the strength and rate of the contraction is modified by the autonomic nervous system. Smooth muscle does not tire. Smooth muscle cells are spindle shaped and contain a single nucleus; they are unstriated. They have no sheath but are connected by connective tissue.

Skeletal muscle

Skeletal or 'voluntary' muscle is the muscle that moves our bodies and is attached to the skeleton or connective tissue via tendons. It is under voluntary control but can tire quickly. The origin of a muscle is normally the end attached to the less movable bone. The insertion of a muscle is usually the end that is attached to the most movable bone. Between the origin and insertion of a muscle is the muscle belly. Muscles can have multiple origins, insertions and bellies.

Skeletal muscle is able to contract, respond to stimulation from the nervous system and hormones, stretch beyond its normal resting length and recoil back to its original resting length. It is composed of long thin cylindrical cells known as muscle fibres. These cells contain multiple nuclei near the surface of the cell and two types of myofilaments; actin and myosin. The actin and myosin filaments are organized in units called sarcomeres which are joined end to end to form a myofibril. The arrangement of the myofilaments inside the myofibrils are the reason that muscle cells appear striped under magnification.

Each muscle cell/fibre is surrounded by an external lamina called a sarcolemma. Groups of muscle fibres are surrounded by a loose connective tissue called endomysium, this contains capillaries which supply the muscle cells with blood. The cells with their surrounding endomysium are bundled together into fasciculae and surrounded by a strong connective tissue called perimysium. A muscle is made up of many fasciculae bound together by a dense connective tissue called epimysium


Nervous System

Nervous system

The Human Nervous System.

Latin systema nervosum

Neuroscience portal

The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous system of vertebrates (such as humans) contains the brain, spinal cord, and retina. The peripheral nervous system consists of sensory neurons, clusters of neurons called ganglia, and nerves connecting them to each other and to the central nervous system. These regions are all interconnected by means of complex neural pathways. The enteric nervous system, a subsystem of the peripheral nervous system, has the capacity, even when severed from the rest of the nervous system through its primary connection by the vagus nerve, to function independently in controlling the gastrointestinal system.

Neurons send signals to other cells as electrochemical waves travelling along thin fibers called axons, which cause chemicals called neurotransmitters to be released at junctions called synapses. A cell that receives a synaptic signal may be excited, inhibited, or otherwise modulated. Sensory neurons are activated by physical stimuli impinging on them, and send signals that inform the central nervous system of the state of the body and the external environment. Motor neurons, situated either in the central nervous system or in peripheral ganglia, connect the nervous system to muscles or other effector organs. Central neurons, which in vertebrates greatly outnumber the other types, make all of their input and output connections with other neurons. The interactions of all these types of neurons form neural circuits that generate an organism's perception of the world and determine its behavior. Along with neurons, the nervous system contains other specialized cells called glial cells (or simply glia), which provide structural and metabolic support.

Nervous systems are found in most multicellular animals, but vary greatly in complexity.Sponges have no nervous system, although they have homologs of many genes that play crucial roles in nervous system function, and are capable of several whole-body responses, including a primitive form of locomotion. Placozoans and mesozoans—other simple animals that are not classified as part of the subkingdom Eumetazoa—also have no nervous system. In Radiata (radially symmetric animals such as jellyfish) the nervous system consists of a simple nerve net. Bilateria, which include the great majority of vertebrates and invertebrates, all have a nervous system containing a brain, one central cord (or two running in parallel), and peripheral nerves. The size of the bilaterian nervous system ranges from a few hundred cells in the simplest worms, to on the order of 100 billion cells in humans. Neuroscience is the study of the nervous system.


Respiratory System

The function of the human respiratory system is to transport air into the lungs and to facilitate the diffusion of Oxygen into the blood stream. Its also receives waste Carbon Dioxide from the blood and exhales it.

The respiratory system consists of the following parts, divided into the upper and lower respiratory tracts:

Parts of the Upper Respiratory Tract

Mouth, nose & nasal cavity: The function of this part of the system is to warm, filter and moisten the incoming air

Pharynx: Here the throat divides into the trachea (wind pipe) and oesophagus (food pipe). There is also a small flap of cartilage called the epiglottis which prevents food from entering the trachea

Larynx: This is also known as the voice box as it is where sound is generated. It also helps protect the trachea by producing a strong cough reflex if any solid objects pass the epiglottis.


Skeletal System

Our skeleton is tough and flexible. It supports weight and protects our internal organs. Bone tissue stores minerals, such as calcium, and it is constantly renewed, which is how our bones are able to heal.

Bones are cleverly designed to allow movement at the joints and provide great stability. The bones provide a light but strong framework for the bodies soft tissues.

The number of bones in the human body actually varies from person to person but the average number is 206.

There are two sections of the body, the central bones which include the skull, ribs, spine and sternum. The arms, legs, shoulder blades, collar bone and pelvis make up the appendicular skeleton.


Urinary System

The principal function of the urinary system is to maintain the volume and composition of body fluids within normal limits. One aspect of this function is to rid the body of waste products that accumulate as a result of cellular metabolism. Other aspects of its function include regulating the concentrations of various electrolytes in the body fluids and maintaining normal pH of the blood.

In addition to maintaining fluid homeostasis in the body, the urinary system controls red blood cell production by secreting the hormone erythropoietin. The urinary system also plays a role in maintaining normal blood pressure by secreting the enzyme renin.

The urinary system consists of the kidneys, ureters, urinary bladder, and urethra. The kidneys form the urine and account for the other functions attributed to the urinary system. The ureters carry the urine away from kidneys to the urinary bladder, which is a temporary reservoir for the urine. The urethra is a tubular structure that carries the urine from the urinary bladder to the outside.

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