Kidney (renal) is the main excretory organ in human. The organ is located in the left and right sides of waist. There are two kidneys and they are covered by protection membrane composed of fat.
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 sweat.
Kidney (renal) is the main excretory organ in human. The organ is located in the left and right sides of waist. There are two kidneys and they are covered by protection membrane composed of fat. The kidneys excrete nitrogenous waste from blood which is urea or (NH2)2CO3 regulate the balance of water and salt in blood, and discharge foreign substances, drugs, and poisonous matters.
Structure Of Kidneys
Each Kidney is composed of several part as follows.
- Cortex is the outer layer containing Malphigian body, proximal tubules, and distal tubules.
- Medula is the component of kidney that consists of collecting tubules and Henle’s loop. It ends in papilla of kidney funnel (real pelvis).
Nephron is the smallest structural and functional unit of kidney. It is composed of several components, which are as follows.
- Malphigian body comprises of bowman’s capsule and glomerulus. Glomerulus is the arteriole capillaries tuft enclosed by the bowman’s capsule.
- Contortus tubules consists of proximal contortus tubules, henle’s loop, distal contortus tubules, and collecting tubules.
Process Of Urine Formation in Kidney The process of urine formation is conducted through several phases, which are filtration, absorption, and augmentation.
Filtration is the blood filtration process occurring in glomerulus reside Malphigian body. Water, nitrogenous waste, glucose, and mineral salt in blood flow through capillary wall from glomerulus, go into bowman’s capsule, then the primary urine is formed (glomerular filtrate). Primary urine contains water, sugar, amino acid, salts, urea, and uric acid.
Reabsortion is the process to reabsorb the substances that still remain in blood after having filtration. The primary urine which leaves bowman’s capsule flows into tubules through capillary vessel and undergoes reabsortion. In the proximal contortus tubules, primary urine undergoes reabsortion which is the reabsortion of water, sugar (up to 80%), amino acid, salt, Na, Cl, PO43-, K+, Ca2+, HCO3, ceratine, and ascorbic acid. The result is secondary urine (tubular filtrate).
Augmentation is the process of adding K+, NH3, and H+ ions in the secondary urine reside distal contortus tubules. The result is urine that will be put in the collecting tubules.
Then, the urine is flown through renal pelvis, ureter, and stored in urinary bladder (vesica urinary). The urinary bladder can collect approximately 600 ml of urine. The urethra is a tube which connects the urinary bladder to the ouside of the body.
The amount of water in distal tubules is controlled by ADH (antidiuretic or vasopresin) hormone. When ADH is present in high concentration, the urine produced is in small volume and concentrated; when the concentration is low, it produces a large volume of dilute urine.
The excretion process of urine through urethra is called urination. Normal urine usually contains water, ammonia, urea, and urobillin pigment. The normal volume of urine of a adult per day is 1-2 liters. The amount of urine is influenced by diuretic substances (coffee, tea, and alcohol), temperature, the amount of drinking water, and emotion.