Exam 4

Question 1

What are the major functions of the kidney?

Answer 1

Filtration, reabsorption, secretion, and excretion of wastes; regulation of electrolytes, pH, blood pressure, and water balance.

Question 2

What is the U/P ratio?

Answer 2

The ratio of a solute’s concentration in urine vs. plasma; indicates whether the kidney is concentrating, diluting, or neither.

Question 3

What does filtration mean in kidney physiology?

Answer 3

Bulk movement of fluid and small solutes from glomerulus into Bowman’s capsule due to hydrostatic/oncotic pressure differences.

Question 4

What is secretion in the nephron?

Answer 4

Active transport of molecules from peritubular capillaries into the nephron after filtration.

Question 5

What is reabsorption?

Answer 5

Movement of molecules from filtrate back into blood; most occurs in the proximal tubule; highly energy-demanding.

Question 6

What are the two main kidney regions?

Answer 6

Cortex and medulla.

Question 7

What is the functional unit of the kidney?

Answer 7

The nephron.

Question 8

Order of filtrate flow through the nephron

Answer 8

Bowman’s capsule → Proximal tubule → Descending limb → Ascending limb → Distal tubule → Collecting duct → Ureter → Bladder.

Question 9

Difference between cortical and juxtamedullary nephrons

Answer 9

Cortical are short loops and common; juxtamedullary have long loops extending deep into medulla for concentration of urine.

Question 10

What is the filtration barrier composed of?

Answer 10

Fenestrated capillaries + basement membrane + podocyte filtration slits.

Question 11

What determines GFR?

Answer 11

Balance of hydrostatic & osmotic pressures + diameter of afferent/efferent arterioles.

Question 12

How does afferent arteriole dilation affect GFR?

Answer 12

Increases GFR by raising glomerular pressure.

Question 13

How does efferent arteriole constriction affect GFR?

Answer 13

Increases GFR (up to a point) by backing up pressure in glomerulus.

Question 14

Why is energy demand high in the proximal tubule?

Answer 14

Because most reabsorption is active transport.

Question 15

What happens to water in the proximal tubule?

Answer 15

Water follows solute reabsorption, maintaining isoosmotic filtrate.

Question 16

What is selective reabsorption?

Answer 16

The regulated recovery of ions or nutrients depending on body needs.

Question 17

Why is secretion important?

Answer 17

Eliminates drugs, toxins, excess ions not removed adequately by filtration.

Question 18

How is secretion similar to absorption?

Answer 18

Both require active transport; same per-molecule energy cost.

Question 19

What produces hypoosmotic urine?

Answer 19

Reabsorption of solutes without water in the distal tubule and collecting duct when ADH is absent.

Question 20

Why can’t water leave the distal tubule in hypoosmotic urine formation?

Answer 20

Distal tubule is water-impermeable without ADH.

Question 21

Animals without loops of Henle can produce what type of urine?

Answer 21

Only isoosmotic urine.

Question 22

What produces hyperosmotic urine?

Answer 22

Countercurrent multiplier in long juxtamedullary nephrons + ADH.

Question 23

What is the single effect?

Answer 23

Active transport of solutes out of ascending limb → increases osmolarity of interstitium & descending limb.

Question 24

What is the countercurrent multiplier?

Answer 24

Amplification of the single effect along the descending limb, creating a vertical osmotic gradient.

Question 25

Why does a longer loop of Henle increase urine concentration?

Answer 25

Allows a stronger medullary gradient → more water reabsorption → more concentrated urine.

Question 26

Is the ascending limb permeable to water?

Answer 26

No; it pumps out solutes and is water-impermeable.

Question 27

How does ADH affect kidney tubules?

Answer 27

Increases water permeability of distal tubule & collecting duct.

Question 28

What is the result of ADH presence on filtrate?

Answer 28

Filtrate becomes increasingly concentrated as it equilibrates with medullary interstitial fluid.

Question 29

What triggers ADH release?

Answer 29

High plasma osmolarity or low blood volume.

Question 30

What does aldosterone do?

Answer 30

Increases Na⁺ reabsorption; water follows → increases blood volume without changing osmolarity.

Question 31

What stimulates aldosterone release?

Answer 31

Angiotensin II via the renin-angiotensin-aldosterone system.

Question 32

What does ANP do?

Answer 32

Inhibits aldosterone, increases GFR, and reduces blood volume.

Question 33

What does renin do?

Answer 33

Starts the cascade producing angiotensin II → vasoconstriction, aldosterone release, thirst.

Question 34

How do kidneys prevent blood acidification?

Answer 34

By reabsorbing 100% of filtered bicarbonate.

Question 35

How is bicarbonate reabsorbed?

Answer 35

Filtered HCO₃⁻ combines with secreted H⁺ → CO₂ + H₂O, which diffuse in and reform HCO₃⁻ inside tubular cells.

Question 36

How does the kidney excrete excess H+?

Answer 36

By buffering it with urinary buffers such as HPO₄²⁻ (phosphate).

Question 37

What is metabolic acidosis?

Answer 37

Low HCO₃⁻ or gain of acid; kidneys compensate by increasing H⁺ secretion and generating new bicarbonate.

Question 38

What is respiratory acidosis?

Answer 38

High CO₂; kidneys increase H⁺ excretion and HCO₃⁻ retention.

Question 39

What hormone controls FSH and LH release?

Answer 39

GnRH from the hypothalamus.

Question 40

What do FSH and LH stimulate?

Answer 40

FSH: gamete/follicle growth. LH: sex steroid production and ovulation.

Question 41

What do sex steroids do?

Answer 41

Estrogen, progesterone, and testosterone regulate reproduction and feedback on the HPG axis.

Question 42

Where are sperm produced?

Answer 42

Seminiferous tubules.

Question 43

What do Sertoli cells do?

Answer 43

Support spermatogenesis; respond to FSH.

Question 44

What do Leydig cells do?

Answer 44

Produce testosterone in response to LH.

Question 45

What do ovaries produce?

Answer 45

Follicles containing granulosa & thecal cells.

Question 46

Role of granulosa cells

Answer 46

Convert androgens → estrogen; respond to FSH.

Question 47

Role of thecal cells

Answer 47

Produce androgens; respond to LH.

Question 48

When does the follicular phase occur?

Answer 48

From menstruation → ovulation.

Question 49

What does estrogen do early vs late in the follicular phase?

Answer 49

Early: negative feedback on pituitary. Late: positive feedback → LH surge.

Question 50

What triggers ovulation?

Answer 50

The LH surge.

Question 51

What happens to the endometrium in the follicular phase?

Answer 51

It sloughs then regrows.

Question 52

What forms after ovulation?

Answer 52

Corpus luteum.

Question 53

What does the corpus luteum secrete?

Answer 53

Estrogen and progesterone at high levels.

Question 54

How does the luteal phase end?

Answer 54

Corpus luteum degenerates after ~14 days unless rescued by hCG.

Question 55

Effect of luteal hormones on pituitary

Answer 55

Inhibit FSH and LH secretion.

Question 56

What does hCG do in early pregnancy?

Answer 56

Maintains corpus luteum so progesterone stays high and menstruation is prevented.

Question 57

What drives birth?

Answer 57

Oxytocin positive feedback on uterine contractions.

Question 58

What hormones regulate lactation?

Answer 58

Prolactin: milk production; Oxytocin: milk ejection.