Urinary II

Question 1

Be able to label the nephron and give an overview of urine formation. Start with blood entering the afferent arteriole and finish with urine leaving the collecting duct. Include what is happening at each stage of the nephron. At times, the cardiovascular system should enter your explanation. This is really knowing the complete overview of glomerular filtration, tubular reabsorption, and tubular secretion.

Answer 1

Renal Corpuscle: where glomerular filtration takes place, 80% of plasma stays in blood stream while 20% goes into filtration and eventually only ends with <1% of plasma in urine.
PCT: >19% of plasma is reabsorbed, H2O, Na+, Cl-, K+, AA, urea, and glucose are reabsorbed while creatinine, H+, and drugs are secreted into the filtrate.
Loop of Henle: descending is permeable to water while and ascending is permeable to NA+, Cl-, and K+.
DCT: Na+, Cl-, Mg+, K+, Ca2+, and HCO3- is reabsorbed while H+, and K+ are secreted back into the filtrate.
Collecting duct: Na+, Cl-, urea, H2O are reabsorbed

Question 2

Know how substances move across a membrane. Primary and secondary active transport, diffusion, and ion channels. What are symporters? What are antiporters?

Answer 2

Symporters: move substances in same direction
Antiporters: move substances in opposite directions

Question 3

Know that most reabsorption occurs in the PCT and secretion is fine tuned in the DCT. Know what substances are located where in the process. For example, glucose is found in filtrate but not in urine.

Answer 3

Filtrate: water, Na+, Cl-, Ca2+, K+, AA, glucose
Urine: water, uric acid, ammonia, urea, H+, HPO42-, urobilin

Question 4

Know how the Loop of Henle functions.

Answer 4

• tubular fluid enters descending limb
• vasa recta capillaries surround loop of Henle
• as fluid moves through loop, control volume and osmoilarity-major players are Na+, Cl-, K+
• these control water
• loop fine tunes what is secreted and absorbed in terms of volume and osmoilarity
• this process is called countercurrent mechanism, 15% of reabsorption

Question 5

Be able to explain obligatory and facultative water reabsorption. What are the hormones that affect it?

Answer 5

obligatory: 90%, water follows solutes that are reabsorbed
facultative: 10%, regulated by ADH, adapts to water need, may have concentrated urine
ADH

Question 6

Explain the formation of concentrated urine.

Answer 6

• juxtamedullary nephrons w/ long loops
• osmotic gradient is created by countercurrent multiplier
• solutes pumped out of ascending limb but water stays in tubules
• medulla osmolarity increase
• in presence of ADH, collecting ducts become permeable to water
• movement of water also carries urea into medulla contributing to its osmolarity

Question 7

Be able to explain countercurrent exchange

Answer 7

loop and duct cells require nutrients and oxygen from blood supply, incoming and outgoing blood will have similar osmolarity, mainly at vasa recta WATCH VIDEOS

Question 8

Describe micturition

Answer 8

Urination
Parasympathetic NS-micturition center-nerves to bladder-1. relax internal sphincter 2. detrusor muscle contract and squish bladder wall 3. relax external sphincter

Question 9

Briefly explain the uses of two blood tests for kidney function

Answer 9

Plasma creatinine: form catabolism of creatinine phosphate in skeletal muscle, increase PC then poor renal function
BUN (blood urea nitrogen): measures blood nitrogen from catabolism of AA, kidney disease or obstruction has increase BUN, AA-nitrogen-urea