Homeostasis: Excretory System (HY)

Question 1

what are the structures and pathway of the excretory system?

Answer 1

right/left kidneys –> right/left ureter –> bladder –> urethra

Question 2

the renal artery, renal vein, and ureter enter and exit through what structure in the kidney?

Answer 2

renal hilum, a deep slit on surface

Question 3

what is the cortex and medulla of a kidney?

Answer 3

cortex is the outermost layer of kidney and medulla sits within cortex

Question 4

what is the pathway for the renal portal system consisting of two capillary beds?

Answer 4

renal artery passes through medulla and enters cortex as afferent arterioles –> glomerulus (first capillary bed) –> efferent arteriole –> vasa recta (second capillary bed) around loop of Henle

Question 5

what is the role of the glomerulus?

Answer 5

filter waste products from blood

Question 6

what is Bowman’s capsule?

Answer 6

cuplike structure that surrounds glomerulus

Question 7

From Bowman’s capsule, what is the pathway leading to the renal pelvis (widest part of ureter connected to kidney)?

Answer 7

bowman’s capsule –> proximal convoluted tubule –> descending limb of Loop of Henle –> ascending limb of Loop of Henle –> distal convoluted tubule –> collecting duct –> renal pelvis and ureter

Question 8

when bladder is full of urine, what is the process the leads to urination?

Answer 8

1. stretch receptors convey to nervous system that bladder is full
2. parasympathetic nervous system contract detrusor muscle lining the bladder
3. micturition reflex: detrusor contraction leads to internal urethral sphincter relaxation (consists of smooth muscle so involuntary)
4. individual chooses through somatic nervous system whether to relax external urethral sphincter (consists of skeletal muscle so voluntary)

Question 9

what is primary function of the kidney?

Answer 9

regulate blood volume and osmolarity

Question 10

what three processes does the kidney do to regulate blood volume and osmolarity?

Answer 10

1. filtration
2. secretion
3. reabsorption

Question 11

What are Starling forces between blood in capillaries and Bowman’s space (inside Bowman’s capsule)?

Answer 11

Not actually forces, but the pressure differential between hydrostatic pressure and oncotic pressure

higher hydrostatic pressure in glomerulus (blood) than in bowman’s space –> push blood into nephron
higher osmolarity in blood than bowman’s space –> oncotic pressure resisting push of blood into nephron
NET: push blood into nephron

Question 12

What is the filtrate in context of kidney osmoregulation?

Answer 12

filtrate is the blood-like substance pushed into bowman’s space, doesn’t contain cells or proteins

Question 13

what does it mean for one solution to be isotonic to another?

Answer 13

both solutions have same osmotic pressure

Question 14

what does nephron secretion entail?

Answer 14

secreting acid, bases, ions and salts, and urea into the proximal/distal convoluted tubules using passive and active transport

also:
- can also secrete waste too large to pass through glomerulus pores
- can eliminate metabolites of medications from blood when in excess

Question 15

How does a diet heavy in meat lead to a large amount of urea in urine?

Answer 15

heavy meat –> high protein –> lots of nitrogen –> ammonia as byproduct of metabolism –> liver converts ammonia to neutral urea –> urea travels to kidney where nephron secretes it

Question 16

what does nephron reabsorption entail?

Answer 16

compounds that are filtered are secreted can be reabsorped into blood (glucose, vitamins, and amino acids)

Question 17

when filtrate enters the proximal convoluted tubule, what is secreted and what is absorbed?

Answer 17

secreted: H+, urea, ammonia, K+
reabsorbed: glucose, amino acids, vitamins, some salts (sodium chloride), water

Question 18

when molecules are reabsorbed into the interstitium, connective tissue surrounding nephron, how are they picked up by blood?

Answer 18

picked up by vasa recta

Question 19

the descending limb of Henle is only permeable to what?

Answer 19

water

Question 20

Why does the kidney alter the osmolarity of the intersitium, especially deeper in medulla?

Answer 20

inner medulla has high osmolarity when water needs to be conserved
it is isotonic with blood (low osmolarity) when trying to excrete water

Question 21

what is the countercurrent multiplier system?

Answer 21

it is a system formed by the loop of Henle and vasa recta because flow of filtrate and blood are opposite one another. As a result, filtrate is constantly exposed to hypertonic blood, allowing maximal reabsorption of water.

if flow was in same direction, equilibrium would be reached, limiting water reabsorption.

Question 22

the ascending loop of Henle is only permeable to what?

Answer 22

only permeable to salts

impermeable to water

Question 23

as you go deeper into the medulla, what happens to the interstitial fluid?

Answer 23

the salt concentration of the interstitial fluid increases (osmolarity increases)

therefore, more water reabsorbed deeper into medulla, and more salt reabsorbed higher in the medulla

Question 24

what is the diluting segment and where is it located?

Answer 24

the diluting segment is located on the ascending limb of the loop of henle at the transition between the inner and outer medulla.

cells lining the loop of Henle become larger in this segment due to more mitochondria –> more ATP production to drive sodium and chloride active transport reabsorption

Question 25

what is the only portion of the nephron that can create urine more dilute than the blood (ie. hypertonic blood)? this occurs during overhydration

Answer 25

diluting segment

Question 26

how does the volume of filtrate change through the loop of henle?

Answer 26

large DECREASE in volume due to reabsorption of water

Question 27

what occurs in the distal convoluted tubule?

Answer 27

1. reabsorption of sodium (osmotically active) due to aldosterone –> reabsorption of water
2. secretion of waste products

Question 28

what occurs in the collecting duct?

Answer 28

reabsorption of water
amount of water varies and is regulated by antidiuretic hormones (ADH) and aldosterone (sodium reabsorption –> water reabsorption)

Question 29

what are the two hormones that regulate blood pressure?

Answer 29

antidiuretic hormone/ADH (water reabsorption)

aldosterone (sodium reabsorption –> water reabsorption)

Question 30

what is the effect of aldosterone on reabsorption, blood pressure, blood osmolarity, and secretion?

Answer 30

reabsorption: increases reabsorption of sodium and water
blood pressure: increases blood volume and pressure
blood osmolarity: doesn’t change osmolarity
secretion: increases secretion of K+ and H+

Question 31

what is the effect of antidiuretic hormone (ADH) on reabsorption, blood pressure, and blood osmolarity?

Answer 31

reabsorption: increases reabsorption of water
blood pressure: increases blood pressure
blood osmolarity: decreases blood osmolarity

Question 32

How does the cardiovascular system help maintain blood pressure through vasoconstriction/vasodilation with respect to aldosterone release?

Answer 32

afferent arteriole constriction –> lower blood pressure reaching glomuerlus, which is near juxtaglomerular cells -> release of renin ————> aldosterone release –> water reabsorption

Question 33

what do juxtaglomerular cells do in the kidney?

Answer 33

release renin in response to low blood pressure

Question 34

what’s the difference between osmotic pressure and oncotic pressure?

Answer 34

osmotic pressure: sucking pressure that draws in water due to all dissolved solutes
oncotic pressure: sucking pressure draws in water due only to dissolved proteins

Question 35

how does the excretory system regulate blood pH through the bicarbonate buffer system?

Answer 35

low pH: excrete more H+, reabsorb more bicarbonate –> increase pH
high pH: reabsorb more H+, excrete more bicarboante –> decrease pH