6: Homeostasis - The Kidneys Flashcards
(28 cards)
Kidney’s function?
Excrete waste products, regulate water potential of the blood
What is a glomerulus?
a bundle of capillaries looped inside a hollow call called a Bowman’s capsule
Plural of glomerulus?
Glomeruli
Where does ultrafiltration take place?
Inside a Bowman’s capsule
What arteriole takes blood into the glomerulus?
the afferent arteriole (arrive)
What arteriole takes filtered blood away from the glomerulus?
the efferent arteriole (exits)
How does ultrafiltration occur?
The efferent arteriole is smaller in diameter than the afferent so the blood in the glomerulus is under high pressure, forces liquid and small molecules out of the blood in the capillaries and into the Bowman’s capsule
What three layers does the filtrate have to pass through to get into the Bowman’s capsule and enter the nephron tubules?
The capillary endothelium, the basement membrane, the epithelium of the Bowman’s capsule
What are the substances that enter the Bowman’s capsule called?
The glomerular filtrate
Where does selective reabsorption occur?
the proximal convoluted tubule, the loop of Henle, the distal convoluted tubule
Feature of the proximal convoluted tubule?
epithelium has microvilli to provide a large surface area for the reabsorption of useful materials from the glomerular filtrate into the blood
How are useful solutes reabsorbed along the PCT?
Active transport and facilitated diffusion
What is urine made of?
Water, dissolved salts, urea, hormones, excess vitamins
What does urine not usually contain?
Proteins, blood, cells, glucose
What is osmoregulation?
The regulation of the water potential of the blood and urine by the kidneys
Where is the loop of Henle found in the kidney?
The medulla
Where are the PCT and DCT found in the kidney?
The cortex
Selective reabsorption step 1?
The ascending limb
Near the top of the ascending limb of the loop of Henle, sodium ions are pumped out into the medulla by active transport. Low water potential in the medulla.
Feature of the ascending limb?
Impermeable to water
Selective reabsorption step 2?
The descending limb
Water moves out of the descending limb due to the lower water potential in the medulla by osmosis. Filtrate more concentrated. Water reabsorbed into the blood through the capillary network
Selective reabsorption step 3?
Bottom of the ascending limb
Near the bottom of the ascending limb, sodium ions diffuse out into the medulla. Ascending limb impermeable to water so water remains in the tubule
Selective reabsorption step 4?
DCT
Water moves out of the distal convoluted tubule by osmosis and is reabsorbed into the blood
Selective reabsorption step 5?
Collecting duct
Ion concentration in medulla high - water moves out of collecting duct by osmosis and reabsorbed into the blood through the capillary network
How is the volume of water reabsorbed controlled?
By changing the permeability of the DCT and the collecting duct
