Homeostasis and Excretion Flashcards
Describe the structure of the urinary system
Each kidney is supplied with blood through a short renal artery. This leads from the aorta so the blood is under high pressure. Inside each kidney the blood is filtered and the cleaned blood pass out though each renal vein.
The urine passes out of the kindness through the ureters and is stored in the bladder. When the bladder is full, the sphincters on the wall of the urethra relaxes to release urine out of the body and contracts to close the urethra to hold back urine.
Describe the structure of a nephron
BOWMAN’S CAPSULE
Collects Glomerular Filtrate and Allows it to Enter Tubules
GLOMERULUS
Filters Blood and Produces Glomerular Filtrate
CONVOLUTED TUBULES
Where Glomerular Filtrate will Flow through and Needed Substances are Reabsorbed Back into the Blood
LOOP OF HENLE
Maintains Water Concentrations in the Body by Filtering Out Salts
COLLECTING DUCT
Reabsorbs Water Back into the Blood Depending on Levels of ADH Produced and Collects Urine
Describe ultrafiltration
The pressure of the blood in the arteriole leading to the glomerulus is very high. This forces fluid from the blood through the walls of the capillaries and the Bowmans capsule, into the space in the middle of the capsule. Blood in the glomerulus and the space in the capsule are separated by the capillary wall and the wall of the capsule, between them is the basement membrane.
These layers act like a filter allowing small molecules to pass through but holding back large molecules and blood cells. The fluid that enters the capsule space is the glomerular filtrate.
Where is glucose and water reabsorbed?
Glucose: proximal convoluted tubule
Water: collecting duct
Describe the role of ADH
The loss of water means that the concentration of the blood starts to increases. They is detected by special cells in the hypothalamus. These cells are sensitive to the solute concentration of the blood and cause the pituitary gland to release more ADH. ADH travels in the bloodstream to the kidney. At the kidney tubules, it causes the collecting duct to become more permeable to water so more water is reabsorbed back into the blood. This makes the urine more concentrated so that the body loses less water and the blood becomes more dilute.
