1. Organ System:

(i) Many organs join together to form an organ system.

2. Digestive System:

(i) The process of conversion of complex food molecules such as carbohydrates, proteins and fats to simpler molecules like glucose, amino acids, fatty acids and glycerol, respectively is known as digestion. This is brought about by the digestive system.

(ii) The digestive system can be divided into the digestive tract and digestive glands.

(iii) Digestive tract is a coiled, muscular tube connecting the mouth to the anus. It is divided sequentially as mouth, buccal cavity, pharynx, oesophagus, stomach, small intestine, large intestine, rectum and anus.

(iv) There are three main digestive glands. They are salivary glands, pancreas and liver.

(v) Salivary glands secrete saliva which contains enzymes which break down starch into simple carbohydrate molecules.

(vi) Pancreas produces pancreatic juice which contains digestive enzymes for digesting fats, proteins and carbohydrates.

(vii) Liver produces bile for the digestion of fat.

3. Respiratory System:

(i) The respiratory system provides and removes carbon dioxide to and from the tissues. The three major respiratory organs are the airway, lungs and muscles of respiration.

(ii) Airway carries air between the lungs and its surroundings. It consists of the nasal cavity, pharynx, larynx, trachea, bronchi and lungs.

(iii) Lungs are paired, cone-shaped organs. They are protected by the ribcage.

(iv) Diaphragm and intercostal muscles are the muscles of respiration. They act as pumps and push the air in and out of the lungs while breathing.

4. Circulatory System:

(i) The system that circulates blood that carries oxygen and nutrients is called the circulatory system. It consists of the heart, blood and blood vessels.

(ii) The heart is a muscular organ that is covered with a double-walled membrane called pericardium and the space between the membranes is filled with pericardial fluid. This fluid protects the heart from shock.

(iii) The heart is divided into four chambers. Two upper chambers are called atria or auricles. Two lower chambers are called ventricles.

(iv) The upper and lower chambers of the heart are separated by a muscular wall known as auriculo-ventricular septum.

(v) The right side of the heart takes care of the deoxygenated blood and the left side of the heart takes care of the oxygenated blood.

(vi) The function of the blood is to transport nutrients, oxygen, wastes and hormones. The blood regulates water level and the body temperature.

(vii) Blood vessels consist of arteries and veins.

(viii) Arteries carry oxygenated blood except the pulmonary artery and veins carry deoxygenated blood except for the pulmonary vein.

5. Excretory System:

(i) The system that removes the waste from the body is the excretory system. It also regulates water and electrolyte balance.

(ii) Kidneys, lungs, liver and skin are the excretory organs. And kidneys, ureters and urinary bladder are the organs of the excretory system.

(iii) Kidneys are bean-shaped organs and are covered by a fibrous membrane called capsule.

(iv) The kidneys are made up of millions of nephrons. They are the structural and functional units of the kidneys.

(v) Ureters are the tubes that carry the urine from the kidneys to the urinary bladder.

(vi) Urinary bladder is a sac-like structure that acts as a storage organ of urine. And the urine is removed from the body through the urethra.

6. Nervous System:

(i) The integration of nerves and specialised cells called neurons forms the nervous system.

(ii) The nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS).

(iii) The central nervous system consists of the brain, the spinal cord and the nerves.

(iv) The brain is covered by three membranes called meninges. They are dura mater, arachnoid membrane and pia mater.

(v) The brain is protected by the skull and is divided into forebrain (cerebrum), midbrain (cerebellum) and hindbrain (medulla oblongata).

(vi) The forebrain contains the cerebrum, thalamus and hypothalamus. It is the largest part of the brain.

(vii) The forebrain is responsible for intelligence, imagination and reasoning.

(viii) The midbrain co-ordinates the movements of the muscles and helps to maintain the balance of the body.

(ix) The hindbrain comprises the pons and medulla oblongata. It is also called the brain stem.

(x) The hindbrain is also known as a vital knot because it controls breathing, heart beat and other involuntary muscles.

(xi) Spinal cord is a long tube-like structure which extends from the brain.

(xii) The peripheral nervous system consists of nerves extending from the spinal cord to all parts of the body. It is made up of the somatic nervous system and autonomous nervous system.

(xiii) Somatic nervous system carries sensations and messages between the brain and the organs.

(xiv) The autonomous nervous system controls the nerves of the inner organs of the body.

What is the length of the alimentary canal?

Important Questions on Organ Systems

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