The maintenance of the internal environment of the body is called homeostasis.

How this works is when the internal environment is out of order whether the temperature is high or low or the osmotic pressure is high or low. In any matter that puts the body out of order a stimulus is created which is sensed by the sense organs also called the receptors. The receptors are found in the skin. The receptors then send information about the environment to the brain or spinal cord which will be discussed in future blogs. The spinal cord or brain send commands to certain organs. These organs secrete substances which normalizes the environment. These substances bring about an opposite reaction according to the change in environment which is why this action is called a negative feedback.

The change the negative feedback brings about normalizes the body.

For example when there is high water potential of blood the pituitary gland secretes less ADH. Thus less water is absorbed which normalizes the body.


The skin has 3 layers. The first being the epidermis layer which is further divided into 3 groups. The first being the cornified layer. This layer contains dead cells which are out of shape. This protects the body from injury and bacteria. The layer beneath the cornified layer is the granular layer where living cells are changing their shape and moving upwards.

The layer below that layer is called the Malphigean layer which has living cells in. These cells keep on dividiskinng and those cells are pushed upwards. The layer below this layer is called the Dermis. The Dermis is the second layer of the skin which has nerve endings, hair follicles, blood capillaries, and sweat glands in it. It is mainly fibers which are connected in a set pattern. The dermis is more visible on a finger thus this helps in finger prints.

The epidermis layer sinks to the dermis creating a hollow tube called hair follicle. The hair papilla then grows through the tube. The living cells divide and send this extra cells upwards. While cells move upwards they die and forms the hair on the skin. There are sebacious glands found alongside the hair follicles which produce lubricating liquid making the skin soft.

The skin also has sweat pores which sinks to the dermis forming a tube and is knotted tightly around the blood capillaries as the sweat glands. Through diffusion and osmosis the water and inorganic salts enter the sweat gland and then is secreted on the skin.

The nerve endings found on the dermis layer sense temperature and pressure and pain etc.

The Layer below the dermis is hypodermis the third layer in the skin which has adipose tissues in it. This layer only stores fats which helps in insulation of heat.


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