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Organ systems

Organ of the body

There are almost 78 organs in a human body which vary according to their sizes, functions or actions. An organ is a collection of millions of cells which group together to perform single functions in a our body. The cells in these body organs are highly specialized and form for all the necessary actions for some specific time.

Brain

Made up of about 100 billion neurons and contributing nearly 2% of body-weight, brain is the supreme structural and functional unit and control center of the body and the superior-most region of CNS (Central Nervous System). Broadly speaking, major part of the brain is comprised of the hemispheres (left & right) of cerebral cortex. Cerebellum, the horizontally furrowed structure of brain’s rear part, is located behind brainstem that is attached to cerebrum.

Primary components and associated structures of brain work in coordination with one another and execute a number of vital functions, viz. growth, maintenance, reproduction, sexual maturity, alarming and responding to environmental hazards, and personal & behavioral developments.

Thyroid

Thyroid gland lies in the anterior part of our neck, immediately below the larynx and overlying the trachea (windpipe). A normal thyroid gland weighs between 25 and 40 gm. This butterfly shaped gland is highly vascular so it receives one of the highest rates of blood flow per gram of tissue. Thyroid gland moves with the larynx in swallowing and speaking - this feature helps a healthcare professional to differentiate swellings in the glands from those in the adjacent structures.

Skin

It is the largest organ of our body which consists of several tissues including sweat glands, hair follicles, and Meissner's corpuscles. Our skin not only provides protection to the internal body parts, but also gives us our sense of touch.

Heart

It is a muscular pump which contracts at regular intervals in order to squeeze the blood through it into the blood vessels. There are four chambers in the heart. The right chambers contain unclean, that is deoxygenated, blood. On the other hand, the left chambers contain clean, that is oxygenated, blood.

Lungs

Lungs are the major organ of our respiratory system, helping us obtain oxygen and get rid of carbon dioxide. Our chest cavity houses a pair of lungs which open to the external environment through the nose and mouth. A cylindrical tube, called trachea, is the main link between the lungs and the nose and mouth. When we breathe in, air travels through the trachea to our lungs.

Pancreas

Pancreas is one of the extrinsic glands of the digestive system. It has mixed endocrine and exocrine functions, and is present outside the wall of the digestive tract.

Liver

Although skin is considered to be the largest organ of the human body, liver is known to be the largest internal organ and the largest gland in the human body.

Spleen

Spleen is the largest lymphatic organ in the human body. Lymphatic or lymphoid organs are the major parts of the immune system of our body. Function of the immune system is to protect the host (i.e. human body) from the invasion of foreign organisms. Immune system helps the body to distinguish its own tissues from external substances such as bacteria, viruses and toxins. Thus dysfunction or deficiency of components of the immune system can lead to various diseases ranging from arthritis, HIV and cancer.

Prostate

Prostate is known as the largest accessory gland of the male reproductive system. The gland resembles the shape of an inverted cone or a pyramid. In normal adult it weighs about 20 gm. It synthesizes an alkaline fluid that provides about 30% of the volume of seminal fluid. The nature of the prostatic secretion is watery, opalescent fluid which contains calcium, acid phophatase, citric acid, lipids and proteins.

Kidney

There are two bean shaped kidneys in the human body. A normal kidney is about 2.5 cm thick, 10 cm long and 5 cm wide. They are reddish-brown in color and each weighs approximately 130 gm in adults. Both kidneys receive blood from the renal artery; in a resting adult approximately 1.2 to 1.4 Litres of blood flows through both kidneys in one minute which means every 4 to 5 minutes all the circulating blood in the body passes through the kidneys. Kidneys help remove excess salt, water and waste products from the bloodstream. Like other endocrine organs, kidneys also secrete important hormones such as rennin and erythropoietin into the circulation. These hormones play significant roles in the production of blood cell and in the regulation of blood pressure.

Stomach

Stomach carries out the physical and chemical digestion of food. When the muscles contract and relax periodically, food is physically digested. The other stomach function, i.e. the chemical digestion of food, is aided by enzymes secreted by glands found in the walls of stomach.

Bladder

Placed on the pelvic floor, it is an important organ of your excretory system that serves as a temporary storage point for the urinary fluid before it is eliminated through urethra.

Organ systems

The human body is made up of 11 organ systems that work with one another (interdependantly). These systems include the integumentary system, skeletal system, muscular system, lymphatic system, respiratory system, digestive system, nervous system, endocrine system, cardiovascular system, urinary system, and reproductive systems. We will briefly discuss the major functions of each organ system below.

Integumentary system – (skin, hair, nails) Forms the external body covering and protects deeper tissues from injury. Houses cutaneous receptors, sweat glands, oil glands, and synthesizes vitamin D.

Skeletal system – (bones, joints) Supports and protects the body’s organs. Provides a framework muscles use (movement). Bones also store minerals and create blood cells.

Muscular system – (skeletal muscles) Maintains posture and produces movement (locomotion). Produces heat.

Lymphatic system – (red bone marrow, thymus, lymphatic vessels, thoracic duct, spleen, lymph nodes) Houses white blood cells (lymphocytes) involved in immunity. Returns leaked fluid from blood vessels to the blood and disposes debris within the lymphatic stream.

Respiratory system – (nasal cavity, pharynx, larynx, trachea, bronchus, lung) Removes carbon dioxide and continually supplies blood with oxygen. Gaseous exchanges occur in the respiratory system (lungs).

Digestive system – (oral cavity, esophagus, liver, stomach, small intestine, large intestine, rectum, anus) Breaks down food to be absorbed and eliminates indigestible waste.

Nervous system – (brain, spinal cord, nerves) Control system of the body, responds to internal and external changes, activates muscles and glands.

Endocrine system – (pineal gland, pituitary gland, thyroid gland, thymus, adrenal gland, pancreas, ovary, testis) Glands from the endocrine system secrete hormones that regulate many processes like growth, metabolism, and reproduction.

Cardiovascular system – (heart, blood vessels) The heart pumps blood and blood vessels transport it. Blood carries oxygen, carbon dioxide, nutrients, waste and more throughout the body.

Urinary system – (kidney, ureter, urinary bladder, urethra) Eliminates nitrogenous wastes from the body. Regulates acid-base, electrolyte and WATER balance of blood.

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