Excretory System (Kidney)

Question 1

basic anatomy of the kidney

Answer 1

kidney’s functional unit is the nephron

nephron empties into renal pelvis

renal pelvis narrows to form ureter

ureter empties into the bladder

from bladder exits through the urethra to exit body

Question 2

the hilum consists of…

Answer 2

renal artery, renal vein, and ureter

Question 3

portal system of kidney

Answer 3

• renal artery branches out
• pass through the medulla and enter the cortex as afferent arterioles
• highly convoluted capillary tufts derived from afferent arterioles known as glomeruli, and after blood passes through they exit through efferent arterioles to form a second capillary bed which surround the LOH known as vasa recta

Question 4

nephron structure

Answer 4

• around glomerulus is bowman’s capsule
• leads to:

PCT: secrete- AT ~> H+, K+, NH3, urea
reabsorb- AT ~> Na+, aa, gluc, vitamins
diffusion ~> Cl-, H2O

desc limb of LOH: reabsorb- diffusion~> H2O

bottom of LOH: urea reabsorb from CD enters and is once again secreted, circulation

asc limb of LOH: reabsorb- diffusion AND THEN AT~> Cl-, Na+

DCT: secrete- AT ~> H+, K+, NH3
reabsorb- AT ~> NaCl
diffusion ~> H2O

collecting duct: reabsorb ~> H2O

Question 5

countercurrent multiplier system

Answer 5

• flow of filtrate through LOH is opposite direction of blood flow through vasa recta
• filtrate constantly exposed to hypertonic blood which allows maximal reabsorption of water

Question 6

diluting segment

Answer 6

inner to outer medulla LOH becomes thicker

Question 7

at the beginning of LOH…

Answer 7

• filtrate is isotonic to interstitium
• from beginning to end, slight degree of dilution
• by end of LOH volume of filtrate significantly reduced, meaning water reabsorbed

Question 8

bladder structure

Answer 8

• detrusor muscle, parasympathetic activity causes contraction
• internal urethral sphincter, smooth muscle, contracted in normal state, involuntary control
• external urethral sphincter, skeletal muscle, voluntary control

Question 9

urination

Answer 9

• stretch receptors let us know bladder is full, parasympathetic neurons fire
• micturition reflex: detrusor muscle contracts, internal sphincter relaxes
• abdominal assistance

Question 10

starling forces between the bowman’s capsule and glomerulus

Answer 10

• hydrostatic pressure in glomerulus significantly higher that bowman’s capsule, fluid move into nephron
• osmolarity of blood higher than bowman’s capsule, pressure opposing movement of fluid into nephron
• hydrostatic pressure much higher than oncotic pressure so net flow is still from blood into nephron

Question 11

blood pressure management

Answer 11

• aldosterone: steroid hormone, secreted by adrenal cortex in response to dec BP, RAA system, reabsorb Na+ & H2O DCT and CD, inc K+ and H+ secretion
• ADH: peptide hormone, synthesized by hypothalamus and released by post pituitary in response to high blood osmolarity, alters permeability of CD, cell junctions of duct leaky, inc concentration of interstitium then causes reabsorption of water from tubule
• construction of afferent arteriole leads to secondary renin release to raise BP

Question 12

RAA system

Answer 12

• dec BP
• stimulate renin release from juxtaglomerular cells in kidney
• renin cleaves angiotensinogen to form angiotensin I
• metabolized by angiotensin-converting enzyme in lungs to form angiotensin II to promote aldosterone release from adrenal cortex

Question 13

acid-base buffer system

Answer 13

kidneys able to determine how much H+ or bicarbonate to excrete or resorb in response to blood pH