Human Excretion System

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Tool excretion in human excretory system include: liver, lungs, skin, kidney, and colon. Each tool 's function is to secrete substances excretion of metabolic waste that different, except for the water which can be excreted through all means of excretion.

1. Liver

Liver or liver is the largest gland in the body, located in the abdominal cavity of the right side, right under the diaphragm. The liver has several functions, among others:

1. Neutralizing toxins so it does not harm the body, then the toxins excreted through the urine.
2. Changing the glucose into glycogen to regulate blood sugar levels.
3. As a means of issuing excretion of bile and urine color. Each day, the liver produces bile reaches ½ liters.
4. The synthesis of several substances. The liver produces arginase enzyme that converts arginine into ornifin and urea. Ornifin formed can increase NH3 and CO2 are toxic.
5. The liver produces bile which is derived from the hemoglobin of red blood cells that have been old. bile stored in the gall bladder and a green liquid and taste bitter. Bile contains cholesterol, bile salts, mineral salts, and the pigment bilirubin and biliverdin. Bile serves to digest fat so easily absorbed by the body, helps power the absorption of fat in the intestine, activates the enzyme lipase, and changing the substance into a water insoluble substance which is soluble in water.
6. Be remodel the red blood cells that are old . Hemoglobin in the blood is broken down into iron, globin, and heme. Globin iron and reused to produce new red blood cells. Meanwhile, overhauled heme to bilirubin and biliverdin blue green. The dye is oxidized bile in the gut into urobilin which gives a yellowish color in the stool and urine.

2. Lung

The lungs are one of the organs of excretion from the body. Humans have a pair of lungs, the left lung and right. The lung has a primary function as a respiratory closely related to the excretory system. By breathing, you take O2 from the air and release CO2 and H2O. The rest of metabolism in tissues such as carbon dioxide and water are transported by the blood to the lungs to be excreted by diffusion in the alveoli. In many alveolar capillaries that have a layer of cells so that the process can run well.

3. Skin

Leather is one of the tools necessary excretion body to excrete water, salts, and urea from the body in the form of sweat. Excretion through the skin highly correlated with temperature and the activities carried out by humans. The skin that serves as a means of excretion is the sweat glands (glands sudorifera) located in the dermis layer. Human skin consists of two parts, namely the epidermis and dermis.

a. The epidermis

The epidermis is composed of two layers, namely the stratum corneum (horny layer) and a layer of Malpighi. Stratum corneum is the layer of dead skin that may flake off and are replaced by new cells. Meanwhile, Malpighi layer consists of layers of spinosum and germ. Spinosum layer serves to hold the friction from the outside. Germ layer contains cells that actively divide, replacing a layer of cells in the stratum corneum. Malpighi layer can give color to the skin because it contains the pigment melanin. If too much melanin pigment, the color of one's skin becomes dark.

b. dermis

In the dermis there are blood vessels, hair follicles, nerve endings, sweat glands, and sebaceous glands. Sweat glands become active when the temperature is hot. This causes the sweat to the surface of the skin by means of evaporation. This resulted in the evaporation temperature of the skin surface down. Conversely, when the ambient temperature is low (cold), and inactive sweat glands in the skin capillaries constrict. In this condition, the blood does not waste water and metabolic waste that causes evaporation is greatly reduced. This causes the body temperature and the body does not experience cold. Sweating is controlled by the hypothalamus. Below are the actual dermis connective tissue under the skin that has no clear boundaries. In this layer there is fat that serves as a food reserve. Fat serves to hold body heat and protect the body against the outside.

4. Kidneys

Renal excretion is the primary tool in humans. Kidney function to excrete metabolic waste substances containing nitrogen, such as urea, and ammonia. In addition, the kidneys also function to secrete substances that excessive amounts, like vitamin C is too much in the body, maintaining the extracellular osmotic pressure, and maintain the balance of acids and bases.

a. Kidney structure

Human kidney has a length of about 10 cm and forms such as red beans, numbered pair, and is located on the left and right of the spine. Type metanefros the human kidney is not segmented and have many glomeruli. Kidneys are the skin of the kidney, kidney marrow, and kidney cavity.

1. Skin the kidney (cortex). In the skin there are many kidney Malpighi bodies totaling ± 1 million. Agency consists of glomerular Malpighi.
2. Kidney marrow (medulla). Kidney marrow bodies form a cone-shaped and contains a lot of channels that collect urine called convoluted tubules.
3. Cavity kidney (renal pelvis). In this cavity empties into the collecting duct. Of the cavity, urinary tract out of the ureter to the bladder (bladder). From the bladder, urine exits the body through the urethra.

b. Formation of Urine in Kidney

The process of formation of urine in the kidneys through three stages as follows:

1) Filtration (filtering)Blood filtration occurs at the glomerulus, the blood capillary coiled inside the Bowman's capsule. In glomerular endothelial cells are thus facilitate the screening process. In addition, the binding also occurs in glomerular blood cells, platelets, and most of the plasma proteins that did not participate were excluded. The results of the infiltration process in the form of primary urine (glomerular filtrate) is compositionally similar to the blood, but does not contain protein. In the primary urine can be found amino acids, glucose, sodium, potassium, ions, and other salts.

2) Reabsorption (reabsorption)
The process of reabsorption occurs in the vessels (tubules) proximal. This process occurs after the primary results of the infiltration of urine flow in the vessels (tubules) proximal. The ingredients are absorbed in the process of reabsorption are materials that are still useful, such as glucose, amino acids, and a large number of inorganic ions. In addition, the water contained in the primary urine is also experiencing reabsorption by osmosis, while the other ingredients reabsorption take place in active transport.

The process of water absorption also occurs in the distal tubule. Then, the materials that have been reabsorbed by the proximal tubule is returned to the blood through the capillaries that surround the tubules. This reabsorption process also occurs in the loop of Henle, especially sodium ions. The result of the process of reabsorption is secondary urine composition constituent substances which are very different from the primary urine. In the secondary urine was not found substances that are still needed by the body and urine levels higher than in the primary urine.

3) Augmentation (Addition)Urine subsequent secondary distal convoluted tubule entry into and collecting ducts. This happens in the process of adding channels substances that do not benefit the rest of the body. Then, the actual urine get into the bladder (urinary bladder) through the ureter. Furthermore, the urine will be excreted from the body through the urethra. Urine contains urea, urine acid, ammonia, and disassembly of protein remnants. In addition, substances containing excessive in the blood, such as vitamin C, drugs, and hormones and salts. Advertisement