Kamis, 14 Maret 2013

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Excretory System In Human

Every living organism always produces waste resulted from metabolic process that must be discharged. The accumulating metabolic waste is harmful to our body because it can poison the tissues and cells.

a. Liver

Excretory System In Human
In human body, there occurs three excretory processes, which are as follows.

  1. Defecation is the process to discharge the digestive residue or fesces.
  2. Secretion is the process to discharge metabolic product which still can be used (enzyme or hormone) by body.
  3. Excretion is the process to discharge metabolic waste that is no longer used by body in the form of urine, sweat, or CO2

b. lung as excretory organs.

Human excretory system comprises of lungs, liver, skin, and kidney. Lung is the excretory organ of metabolic waste in the form of CO2 and H2O (water vapor) gases. The intestine discharges inorganic salts and some of decomposition products, including ammonia during digestive process.

Liver as excretion gland produces bile which secretes excretion substances, such as cholesterol, bilirubin pigmen (green-blue), and billiverdin (yellow gold). Bilirubin will be oxidized into urobiline (yellow brown) which functions to give color to feces and urine.

Excretory Organ

The Excretory organs that will be discussed in this chapter are skin and kidney. You have been learned the other organs, such as liver, intestine, and lungs in the previous chapter.


Skin plays role as a sense of touch and excretory organ. Skin is considered as excretory organ because it produces sweat

Structure Of Skin
Human Skin is composed of two main parts, namely epidermis and dermis (corium). Epidermis layers consist of stratum corneum, stratum granulosum, stralum spinosum, and stratum germinativum. 

Stratum of granulosum and germanativum are known as Malphigian layers which has the function to replace the flaking off corneal layer. Dermis layers consist of glandula sudorifera (sweat gland), sebaceous gland (lipid gland), hair root, nerve, blood, vessel, and erector muscle of hair.

Skin Function

Human Skin has several function, some of which are as follows.

  1. Controlling body temperature because the sweat produced can absorb body heat.
  2. Protecting body from physical damage, light, evaporation, germs, and drought.
  3. Receiving stimulation of touch, pressure, and outside temperature.

Process of Sweat Excretion
Sweat Consist of water or water vapor. The excretion of sweat from the skin in the form of water vapor is called perspiration. The components of sweat are water, salt solutes, and urea.

Sweat is secreted by the sweat glands whose activity is regulated by temperature controlling center of center nerve system (brain cell) in hypothalamus. The sweat glands absorb water and mineral salt from blood, which are then excreted through skin in the form of sweat.


Emotional stress due to lying can increase sweat excretion in palm. The sweat accelerates electric current which can be detected by electrode as shown in the picture above.

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