The Body systems

The fundamental unit of our body is the Cell. Several cells make up a tissue and several layers of tissue makes up an organ. A set of organs form a system.  In our body the following systems are present:-

1. Skeletal system - The skeletal system is the structure around which the body is built. It is made up largely of bones and cartilege.  Carilege is a flexible connective tissue found in various areas of the body. It is softer than bone but harder n less rigid than muscle.

2. Muscular system - This comprises of the muscles, tendons and sheaths around muscles.  Tendons are the connective tissue which connects muscles to bones.  Ligaments connect bones to bones while fasciae connect muscles to muscles.

3.  Nervous system - This is further subdivided into:-

(a)  Central nervous system comprising brain and spinal cord

(b)  Peripheral nervous system comprising all nerves outside  brain and spinal cord

(c) Autonomous nervous system which controls the automatic functions of the body.  This overlaps cental and peripheral nervous systems.

4.  Circulatory system - This consists of the heart and all the blood vessels(namely arteries, veins and capillaries). Arteries carry oxygenated blood away from the heart and to the organs. As the heart is pumping at high pressure arteries have thick walls.  This blood under high presuure from arteries enters the capillary bed in each organ (via arterioles). The capillaries are just one cell thick and this is where the actual transfer takes place.   As they are only one cell thick, they transfer nutrients and oxygen from the blood to the organs and collect co2 and water which are by products of combustion in the cell.  From the capillaries the impure blood (de-oxygenated) from the organs flows to the veins which is then carried to the heart.

5.  Endocrine system - The endocrine system secretes chemical messengers called hormones to exert its effects. These hormones are directly released into the blood.

6.  Respiratory system - This is concerned with breathing i.e the inhaling of oxygen and exhaling of co2&other gases.  This comprises primarily the lungs and other organs.

7. Digestive system - This is concerned with the ingestion, processing of food, absorption of nutrients and elimination of some types of waste. This involves the stomach, intestines, pancreas, liver, gall bladder etc.

8. Urinary system - The urinary system controls fluid and salt balance in the body and excretes waste.   Together with parts of digestive system and respiratory system, it form the excretory system of the body.

9.  Lymphatic system -  This system forms part of the circulatory system and is also the immune system of the body.

10. Reproductive system - Needless to say that this is an important system for the existence of the human race!!!

Lastly, with so many cells, tissues, organs and systems in the body, a constant internal environment is essential for all these components to function in an efficient manner.  This process is called homeostatis.  To maintain the same internal conditions various other parameters are changed.  The keys systems involved are the endocrine system and the autonomous nerveous system.  They maintain the body's temperature, salinity, sugar levels etc.  The required gland of the endocrine system produces hormones when required to stimulate an organ. these hormones in addition to stimulating that organ also produce secondary hormones as a result of that interaction. These secondary hormones act on the gland (of the endocrine system) and reduce the production.  This works as a sort of feed back mechanism akin to a float valve in a water tank.

Hope you have enjoyed this post about the various body systems. It is very important for us to understand this body of ours very well, as this is the only we ever are going to have!!!!

We will look at each system in detail at a later stage.