The human body can be broken down into a number of systems for example: brain and nervous system, circulatory system, reproductive system, the skin and skeleton. Listed below are the major organs in each system.
adipose tissue. A form of connective tissue in which the constituent cells are modified to enable them to contain droplets of oil. (Fat).
alimentary canal. The food processing tube running from mouth to anus, about 9m long.
alveolus. Sac in lungs absorbing oxygen from the air into the blood.
anus. Excretory opening at end of alimentary canal.
aorta. The largest artery in the human body. It carries blood from the heart to the arms, legs and head.
artery. Blood vessel taking oxygenated blood from the heart to the rest of the body.
bladder. A sack in the abdomen which collects urine from the kidneys.
blood. The main circulatory fluid: red and white blood cells transported in plasma.
bowel. The division of the alimentary canal below the stomach, that is the intestines.
bones. A matrix of collagen fibres providing support for other tissues. The hollow centre is filled with marrow, the source of blood cells.
brain & nervous system. The nervous system is co-ordinated by the brain. All 13 000 million nerves originate in the brain, form the spinal column and branch off to the organs and tissues they control.
bronchi. The bronchial tubes (bronchi) are a division of the trachea which branch repeatedly into small bronchioles within the lungs.
caecum. First part of the large intestine.
cerebellum. Part of the brain at the back of the head that controls the muscles and postural equilibrium.
cerebrum. Each of the two halves of the upper brain that occupies the whole of the dome of the cranium.
colon. Central and major part of the large intestine.
diaphragm. A large transverse muscle at the base of the thorax, used in respiration to draw air into the lungs.
duodenum. First part of the small intestine.
epidermis. Layers of continually shedded skin cells.
epithelium. A basic type of tissue. It comprises the external surface of the skin, the internal surfaces of the digestive, respiratory and urogenital systems and others.
fallopian tubes. Two tubes that carry eggs from the ovary to the uterus. Eggs are fertilised in the Fallopian tubes by sperm, and then moved to the uterus.
follicle. A small group of cells that surrounds and nourishes a structure such as a hair or a cell such as an egg.
fontanelle. A membrane covered vault in the skull. It normally closes during infancy.
ganglion. An enlargment somewhere in the course of a nerve, and containing nerve cells in addition to nerve filaments.
gastric juice. Clear, colourless fluid secreted by the mucous membrane of the stomach, and is the chief agent in digestion.
glands. Organs which produce substances (such as blood) for use within the body. Endocrine glands produce secretions at a distance from the tissues which they affect. Exocrine glands carry secretions through ducts to the site where they are required.
haemoglobin. The protein that carries oxygen in the blood.
heart. Muscular organ in chest that pumps blood to the lungs, tissues and other organs.
hormone. A product of the endocrine glands.
hypothalamus. Part of the brain that controls which regulates rhythmic activity, physiological stability, body temperature and the pituitary gland.
ileum. Last part of the small intestine.
intestine. The digestive tract. The small intestine (duodenum, jejunum and ileum) and large intestine (caecum, colon and rectum). The intestine breaks up digested food into those molecules required by the body.
involuntary muscles. Those muscles we cannot control.
jejenum. Central part of the small intestine.
joint. A structure where two bones meet.
jugular vein. Vein returning blood from the head to the heart.
lachrymal gland. Exocrine gland beneath the upper eye lid which secretes tears
larynx. A cavity at the top of the trachea containing the vocal cords.
leucocyte. Colourless corpuscles; white blood cells.
ligament. Fibrous band supporting bones and joints.
lymphatic system. System of tubes and glands that collect and filter waste fluid from the cells before returning it to the blood system.
muscles. Fibrous organs used to support the skeleton, provide movement or power the body's life support systems.
nerve. Cord like structure built from a number of neurones along which nerve impulses are conveyed to different parts of the body.
neurone. Nerve cell, many centimetres long with a microscopic diameter.
organ. General name for any part of the body that has a specific purpose.
parathyroid glands. Two small glands in the neck concerned with the use of calcium in the body.
parotid gland. Salivary gland.
penis. Male reproductive organ.
placenta. Organ connecting a foetus to the uterine wall. It is the organ by means of which the nutritive, respiratory and excretory functions of the foetus are carried on.
pineal gland. Gland at the base of the brain controlling melatonin levels.
pituitary gland. Master endocrine gland at the base of the brain controlling the other endocrine glands.
plasma. Clear fluid in the circulatory system that transports blood cells.
rectum. Last part of the the large intestine where waste material is stored prior to excretion.
saliva. A secretion from the salivary glands in the oral cavity. It contains mucus to lubricate food and enzymes.
sclerous tissue. The stiffening which is essential for the formation of the general framework of the body. There are two types: cartilage and bone.
sebaceous glands. Ducts in the skin which secrete oil to lubricate the skin and hair.
skeleton. System of bones providing support for the body. Many of the bones are hinged (jointed) allowing the skeleton to move.
skeletal muscles. Those muscles that we can control.
skin. Dermoid Tissue, is composed of two layers, the cuticle, epidermis or epithelium and the corium or dermis.
spleen. Organ that regulates the number of red blood cells.
spleen. Organ in abdomen producing white and destroying red blood cells.
subcutaneous layer. Layer of fatty tissue below the dermis.
stomach. First part of the digestive tract where food is broken down by powerful acids into smaller components.
thalamus. Small part of brain, used in mechanism of sensation.
tonsils. A pair of small organs on either side of the root of the tongue that protect the throat from infection.
trachea. Wind pipe.
thymus gland. Gland in the chest that disappears in adulthood. It is involved with immunity.
thyroid gland. Endocrine gland in neck producing thyroxin regulating the metabolism.
urethra. A canal which that channels urine from the bladder out of the body.
vagina. Female reproductive organ.
vein. Blood vessel returning deoxygenated blood to the heart.
ventricle. Chambers within the heart which force blood along the arteries.
womb. Female reproductive organ where the foetus gestates (develops). The uterus.
An adult human is made up from about 45 litres of water, 13 kg of carbon, enough phosphorous for 2200 matches, a spoonful of sulphur and enough iron for a 25 mm nail.
There are 10 000 million nerves controlled by the brain. An adult heart beats between 60-80 times a minute pumping 5.5 litres of blood around 10 000 km of blood vessels. The lungs draw about half a litre of air 14-16 times a minute. There are about 650 muscles in a human body. 250ml of fluid is lost every day through the feet. The alimentary tract is about 9m long. An adult skeleton contains 206 bones: 22 in the skull with 27 in each hand, 26 in each foot, 24 ribs, 32 teeth, 27 vertebrae and about 100 joints.
The amount of energy an adult requires just to stay alive will power a 75 watt light bulb.