Renal Tubules

Question 1

Function of renal corpuscle

Answer 1

Regulate filtrate, filtrate making machine

Question 2

What within the filtrate should be completely reabsorbed?

Answer 2

**Should never be found in the urine

• Glucose, amino acids, bicarb

Question 3

What within the filtrate should be regulated?

Answer 3

**Partially reabsorbed

• Water, Na+, K+, Cl-

Question 4

What within the filtrate should be excreted as urine?

Answer 4

• Urea, creatinine, drugs

Question 5

Descending limb of LOH: permeability

Answer 5

Water permeable: releases water

Question 6

Ascending limb of LOH: permeability

Answer 6

Impermeable to water: releases ions but not water

Question 7

Collecting ducts: permeability

Answer 7

Sometimes permeable to water (in the presence of ADH)

Question 8

Afferent arterioles: nephrons

Answer 8

Arcuate arteries (run along border of medulla + cortex) and give rise to radial arteries

Radial arteries give rise to afferent arterioles which go to the nephrons

Question 9

Efferent arterioles: renal tubules

Answer 9

Spread over tubules to reabsorb the good stuff

Makes a capillary bed across DCT/PCT and LOH

Then goes into venous drainage

Vasta recta: tiny capillary beds that collects good stuff & gets rid of bad stuff (goes into arcuate vein)

Question 10

Ways to reabsorb solutes & water (x2)

Answer 10

Active transport: requires energy

Passive transport: concentration gradient (note: water always follows sodium)

Question 11

Where does most of the water reabsorption occur (obligatory)?

Answer 11

In the PCT and descending LOH (they’re water permeable)

Question 12

What is facultative water reabsorption and where does it occur?

Answer 12

Water reabsorption that increases/decreases depending on the amount required by the body

Controlled by ADH –> makes collecting ducts water permeable

During dehydration –> lots of ADH is put out

Question 13

What is the most active area for reabsorption?

Answer 13

PCT!

100% of solutes reabsorbed

65% of water reabsorbed by the end of the PCT

Question 14

Types of active transport (x2)

Answer 14

Primary active transport: uses ATP

Secondary active transport: uses energy of movement of ions down their conc. gradient for transport other solutes

Question 15

Types of active transport (x2)

Answer 15

Primary active transport: uses ATP

Secondary active transport: uses energy of movement of ions down their conc. gradient for transport other solutes

Question 16

Types of secondary active transport

Answer 16

Symporter: when the protein moves the ion & solute in the same direction

Antiporter: when the protein moves the ion & solute in opposite directions

Question 17

Maximum rate: transport proteins

Answer 17

Transport proteins can only bind + move solutes at a fixed rate

Saturation of this transport mechanism limits reabsorption of substances like glucose

Question 18

What does glycosuria mean?

Answer 18

Tm of active transporters has been reached (Na+-glucose symporter)

Question 19

How is the glucose symporter coupled to the Na+/K+ pump?

Answer 19

2 sodiums pull in 1 glucose

Sodium is moved into interstitial fluid via Na+/K+ pump

Glucose leaves cell –> interstitial fluid via glucose facilitated diffusion transporter

Question 20

What happens when the kidneys fail?

Answer 20

Salt & waste products (urea) build up & blood pH goes down

Massive edema results from salt retention

Acidemia results from the inability to excrete acids (H+)

Potassium levels get too high –> hyperkalemia + cardiac arrest
(K+ destabilizes cardiac rhythm)

Question 21

Treatments for kidney failure

Answer 21

Kidney dialysis: takes nasty stuff of blood out & puts it back in body

Peritoneal dialysis: port goes into peritoneal cavity & flushes in lots of fluid, salts & waste go there and then everything gets sucked out

Kidney transplant

Question 22

What does the detrusor muscle do?

Answer 22

Contracts to push urine out

Question 23

What is the trigone?

Answer 23

Area in-between 2 urethral openings, part of the bladder that doesn’t contract

Question 24

Deep transverse perineus

Answer 24

Has fibers that run up the urethra

Striated –> voluntary control

Question 25

What do the levator muscles do?

Answer 25

Lift up & down (faces & urinary content), keeps sphincter closed

Question 26

Micturition reflex

Answer 26

Stretch receptors in bladder get stimulated (sends messages to sacral portion of spinal cord, parasym)

Triggers an autonomic reflex which sends parasympathetic motor signals to the detrusor muscle (smooth muscle, not voluntary) and the internal urethral sphincter (in males, SM) relaxes

There is still the external sphincter –> conscious control, need to relax to pee

Question 27

Somatic nerves and micturition reflex

Answer 27

The somatic nerves holding the external sphincter closed are inhibited by the micturition reflex - pressure buildup is usually not enough to open the external sphincter