chapter 1 excretion system (liver and lung)

The excretory system is a passive biological system that removes excess, unnecessary or dangerous materials from an organism, so as to help maintain homeostasis within the organism and prevent damage to the body. It is responsible for the elimination of the waste products of metabolism as well as other liquid and gaseous wastes. As most healthy functioning organs produce metabolic and other wastes, the entire organism depends on the function of the system; however, only the organs specifically for the excretion process are considered a part of the excretory system.

a.    Various kinds of constituent organs of excretions system organs in human

The human excretion system is composed by excretory organs that involve liver , lungs , kidney , and skin. In the following it will be discussed one by one of those excretory organs.

1.    Liver

Liver is included into gland and the largest gland inside the body. Liver has reddish-brown color of weight in adult people  is about 2kg. liver is located inside abdominal cavitiy to the right , under diaphragm.

Liver is included into secretory organ and excretory organ. Liver is called secretory organ because the liver produces gall , while liver is called excretory organ because the gall discharged contains waste matters that come from broken red blood cell and destroyed in the lymph . the gall is discharged by liver is received in gallbladder and then is flown duodenum by gall duct.

Besides as excretory organ , liver also has the other function as follows.

a)    Destroying disease germs and neutralizing poison that enters into the body.

b)    Controlling sugar level in the blood. The surplus substance in the blood is charged to be glycogen and if blood is lacking of sugar substances , the glycogen is charged to be glucose and it is supplied to the bloog.

c)    As formation place of prothombin and fibrinogen.

d)    As place to charge provitamin A to be vitamin A. Provitamin A is obtained from vegetables and fruit that by liver is charged  to be vitamin A.

e)    As formation place of urea. Urea comes from ammonia. Ammonia (NH₃) is chemical compound of recombination surplus of protein. Ammonia has poisonous property so before discharged from the body it must be changed firstly urea.

2.    Lung

Lungs are main organ in respiratory system  because it function to take oxygen (see again the discussion of respiratory in class VIII ). Besides as respiratory organ , the lungs also has function as excretion organ.Respiratory process produces energy and by product of waste matter that is carbon dioxide (CO₂) and water vapor (H₂O). CO₂ and H₂O are released again through lung. So lung is also called as excretion organ because it release CO₂ and H₂O