Topic 9.9 Osmoregulation and temperature regulation Flashcards
Name structures in the gross structure of the mammalian urinary system
- Kidney
- Renal vein
- Renal artery
- Ureter
- Urethra
- Bladder
Describe the gross structure of a mammalian kidney
Fibrous capsule: protects kidney.
Cortex: outer region consists of Bowman’s capsules, convoluted tubules, blood vessels.
Medulla: inner region consists of collecting ducts, loops of henle, blood vessels.
Name structures in a nephron
- Afferent arteriole
- Efferent arteriole
- Glomerilus
- Bowman’s capsule
- Proximal convoluted tubule
- Loop of Henle
- Distal convoluted tubule
- Collecting duct
What are the “outer” and “inner” parts of the kidney
Outer = Cortex
Inner = Medulla
Describe the blood vessels associated with a nephron
Wide afferent arteriole from renal artery enters renal capsule and forms glomerilus: branched knot of capilliaries which combine to form narrow efferent arteriole.
Efferent arteriole branches to form capillary network that surrounds tubules.
Describe the sections of a nephron
Bowmans capsule at the start of nephron: cup shaped, surrounds glomerilus, inner layer of podocytes.
Proximal convoluted tubule (PCT): series of loops surrounded by capilliaries, walls made of epithelial cells wwith microvilli.
Loop of Henle: hairpin loop extends from cortex into medulla.
Distal convoluted tubule: similar to PCT but fewer capillaries.
Collecting duct: DCT from several nephrons empty into collecting duct, which leads into pelvis of kidney.
How is urea produced?
- Hepatocytes deaminate excess amino acids to form ammonia.
- Orthinine cylcle in liver cells converts ammonia to urea, which is less toxic.
Deamination:
(amino acid)-NH2 + O2 -> Keto acid + NH3
Ornathine cylce - ammonia is very toxic so is converted into less toxic urea by ornathine cycle
2NH3 + CO2 -> Ornathine cycle -> Urea
How is urea removed from the blood stream?
Ultrafiltration on Bowman’s capsule.
High hydrostatic preasure in glomerilus forces small molecules (urea, water, glucose, mineral ions) out of the capillary fenestration against the osmotic gradient.
Basement membrane acts as a filter. Blood cells and large molecules e.g. proteins remain in capillary.
How are cells of the Bowman’s capsule adapted for ultrafiltration?
- Fenestrations between epithelial cells of capillaries.
- Fluid can pass between and under folded membrane of podocytes
State what happens during selective reabsorbtion and where it occurs
Useful molecules from glomerular filtrate e.g. glucose are reabsorbed into blood.
Occurs in proximal convoluted tubule.
Outline the processes involved in selective reabsorption
Glucose from glomerular filtrate –(co-transport with Na+ ions)–> cells lining convoluted tubule –(active transport)–> intercellular spaces –(diffusion)–> blood capillary lining tubule
How are cells in the proximal convoluted tubule adapted for selective reabsorbtion?
- Microvilli: large surface area for co-transporter proteins
- Many mitochondria: ATP for active transport of glucose into intercellular spaces
- Folded basal membrane: large surface area
What happens in the loop of Henle?
- Active transport of Na+ and Cl- out of ascending limb.
- Water potential of interstitial fluid decreases.
- Osmosis of water out of descending limb. (ascending limb is impermeable to water)
- Water potential of filtrate decreases going down descending limb: lowest in medullary region, highest at top of ascending limb.
Explain the role of the distal convoluted tubule
Reabsorbtion:
a) of water via osmosis
b) of ions via active transport
Permeability of walls is determined by action of hormones.
Explain the role of the collecting duct
Reabsorbtion of water from filtrate into interstitial fluid via osmosis through aquaporins.
