Chapter 19 - Urinary System

Question 1

Functions

Answer 1

• filters metabolic wastes and toxins from plasma
• metabolizes drugs and toxins
• regulates electrolyte comp. and volume in plasma
• helps maintain blood pH and HCO3
• produces urine
• synthesizes hormones renin and EPO

Question 2

Renin

Answer 2

hormone that helps regulate blood volume and BP
- constricts arterioles, stimulating aldosterone and ADH secretion

Question 3

Erythropoietin

Answer 3

hormone that controls RBC formation and maturation

Question 4

Nephron

Answer 4

• microscopic functional unit of the kidney
• renal corpuscle
• renal tubule

Question 5

Renal corpuscle

Answer 5

• glomerulus
• Bowman’s capsule (visceral and parietal layers)
• macula densa
• juxtaglomerular cells

Question 6

Renal tubule

Answer 6

• PCT
• loop of henle
• DCT
• sensory cells - point where the DCT makes contact w/ the macula densa

Question 7

What is the order of function of the nephron?

Answer 7

1- blood enters glomerular capillaries from aff. arteriole; exits via eff. arteriole

2- filtrate enters Bowman’s space

3- PCT

4- Loop of henle

5- DCT
- most salts, water and nutrients are reabsorbed; additional waste products/drugs/toxins are secreted

6- collecting tubule, collecting duct

7- renal pelvis

Question 8

Renal corpuscle

Answer 8

• filtration barrier
• capillary endothelial cells and visceral layer of bowman’s capsule and basal lamina - fenestrated capillaries
• podocytes have feet that envelop the capillaries
• glomerular filtration rate is about 120 mL/min
  -fenestrated capillaries

Question 9

PCT

Answer 9

• receive filtrate from Bowman’s space
• cuboidal epithelium w/ brush border and mitochondria
• majority of water and electrolytes reabsorbed here
• main site for reabsorption for nearly all organic nutrients like glucose and amino acids
• active transport couples to Na-K ATPase

Question 10

Loop of henle

Answer 10

• U shaped part of renal tubule that extends into medulla
• reabsorbs 15-25% of H2O and salts - continues to absorb more water to maintain fluid homeostasis

Question 11

Thin descending limb of loop of henle

Answer 11

• simple squamous epi
• permeable to H2O but not to salts
• H2O drawn out by osmosis due to hypertonic environment in medulla

Question 12

Thick ascending limb of loop of henle

Answer 12

• simple cuboidal epithelium, lacking microvilli
• impermeable to H2O but reabsorbs salts
• responsible for hypertonic environment in medulla

Question 13

DCT

Answer 13

• simple cuboidal epi, mainly mitochondria but no microvilli
• reabsorbs 5-15% of H2O and salts - final adjustment of K, H in tubular fluid
• principal site of active drug secretion, critical for drug elimination
• site of aldosterone action

Question 14

Aldosterone action in DCT

Answer 14

• increases Na reabsorption and K secretion
• aids in NaCl retention

Question 15

Juxtaglomerular apparatus

Answer 15

• group of cells adjacent to the glomerulus
• macula densa senses Na in filtrate
• if Na is low, JG cells secrete renin into aff. arteriole
• results in increase of BP and blood volume
• secrete EPO

Question 16

Macula densa of juxtaglomerular app.

Answer 16

• specialized cells in DCT, adjacent to aff. arteriole
• sense Na in DCT filtrate

Question 17

Juxtaglomerular cells of juxtaglomerular app.

Answer 17

• smooth muscle in aff. artiole tunic media, adjacent to macula densa

Question 18

Collecting tubules and ducts

Answer 18

• conducts filtrate from end of nephron to renal papilla/minor calyces
• cuboidal cells, gradually becoming columnar as diameter of duct increases
• last point of salt and H2O reabsorption
• site of ADH action

Question 19

ADH action in collecting tubules and ducts

Answer 19

• ADH increases H2O permeability of tubules/ducts
• allows formation of hypertonic urine
• if ADH is low, urine will be dilute

Question 20

Ureter

Answer 20

• conducts urine from renal pelvis to urinary bladder
• transitional epith
• CT
• smooth muscle
• external CT
• distal portion is stratified squamous
• ureters, urinary bladder

Question 21

Urinalysis

Answer 21

• med lab tests to measure concentration of various metabolites, glucose, blood, protein in urine
• proteinuria - elevated protein, indicates problem with glomerular filtration barrier
• hematuria - presence of RBCs, infection or problem with filtration barrier

Question 22

Blood urea nitrogen

Answer 22

• concentration of urea in blood is an indicator of renal function
• urea is a product of protein catabolism
• urea itself is not toxic, but other nitrogenous wastes are and elevated levels cause cognitive impairment

Question 23

Serum creatinine

Answer 23

• product of creatine-P breakdown in muscle
• elevated levels indicate renal failure

Question 24

Hyperglycemia

Answer 24

• caused by lack of insule - insufficient secretion or insulin resistance

Question 25

What does prolonged hyperglycemia cause?

Answer 25

- reduces glucose reabsorption by PCT -> high osmolarity filtrate -> reduced H2O reabsorption -> polyuria

Question 26

What are the chronic complications of hyperglycemia?

Answer 26

- diabetic retinopathy - diabetic neuropathy - proteinuria is an early sign

Question 27

What structure is shown here? What does each letter indicate?

Answer 27

L1 - renal corpuscle L2 - glomerulus L3 - capsular space R1 - PCT R2 - DCT R3 - Loop of Henle R4 - Thin descending limb R5 - Thick ascending limb R6 - Renal tubule