chapter 24 - urinary system

Question 1

homeostatic regulatory systems involving kidneys

Answer 1

• regulates blood volume and pressure by adjusting volume of water lost in urine + releasing erythropoietin and renin
• regulates plasma ion concentrations of Na+ K+ Cl- (controlling qualities lost in urine) and Ca2+ levels (through synthesis of calcitriol)
• helps stabilize blood pH by controlling loss of H+ ions and bicarbonate ions in urine and excretion of nonvolatile acids

Question 2

cortical nephrons

Answer 2

85% of all nephrons
Located mostly within superficial cortex
Nephron (henele) loop is short, descends little into medulla
Efferent arteriole delivers blood to a network of peritubular capillaries

Question 3

juxtamedullary nephrons

Answer 3

15% of nephrons
Contribute to kidney’s ability to concentrate urine
Nephron loops extend deep into medulla
Peritubular capillaries connect to vasa recta

Question 4

how many nephrons are in each kidney?

Answer 4

~1,000,000 per kidney

Question 5

layers of filtration membrane

Answer 5

Fenestrated endothelium of the capillary (~60-100 nm)
Basement membrane (~20 nm)
Slit diaphragm between foot processes (or pedicels) of the podocytes (~6-9 nm)->This and basement membrane hold back MOST proteins (ex albumin) but allow passage of water, ions, glucose, amino acids, urea, etc

Question 6

juxtaglomerular complex function

Answer 6

regulates blood pressure

Question 7

cells in juxtaglomerular complex

Answer 7

granular cells –> secrete renin in response to failing blood pressure in aferent arteriole

macula densa -> monitor solute concentrate in filtrate by signaling granular cells to secrete renin

mesangial cells –> contractile cels that regulate intraglomerular capillary blood flow

extraglomerular mesangial cells –> interact w/ macula densa +granular cels to help regulate glomerular filtration rate (GFR)

Question 8

peritubular capillaries

Answer 8

reclaims filtrate and helps concentrate urine

Question 9

vasa recta

Answer 9

helps concentrate urine

Question 10

what are the parts of the urine transport system?

Answer 10

ureter, urinary bladder, urethra

Question 11

ureter

Answer 11

Pair of muscular tubes that connect renal pelvis to urinary bladder
Contractions occur every ~30 seconds to force urine toward bladder
Ureteral openings are slit-like rather than rounded to help prevent backflow when urinary bladder contracts

Question 12

urinary bladder

Answer 12

Hollow, muscular organ
Wall folded into rugae (wrinkles) when empty
Function: temporary reservoir for urine storage (up to ~1L)

Question 13

urinary bladder wall layers

Answer 13

Mucosa - transitional epithelium

Muscularis - 3 layers of smooth muscle = detrusor muscle (longitudinal-circular-longitudinal)
Causes expulsion of urine from bladder
Thickened around urethral opening to create internal urethral sphincter (controls involuntary urine release)

Adventitia - fibrous, anchors bladder to pelvic floor

Question 14

urethra

Answer 14

From neck of urinary bladder to exterior
Lined with stratified squamous epithelium
Passes through band of skeletal muscle that forms external urethral sphincter
Relaxation results in micturition

Question 15

urethral sphincters

Answer 15

internal and external urethral sphincters

Question 16

differences in external urethral sphincter by gender

Answer 16

Females -> ~3-4 cm
Males -> 20 cm in length
Prostatic urethra → passes through the prostate gland
Intermediate part of urethra → through the urogenital diaphragm
Spongy (penile) urethra → passes through the length of the penis

Question 17

steps of micturition reflex

Answer 17

Visceral afferent impulses from stretch receptors in the bladder wall are carried to the spinal cord and then, via ascending tracts, to the pontine micturition center
Integration in the pontine micturition center initiates the micturition response. Descending pathways carry impulses to motor neurons in the spinal cord
Parasympathetic efferents stimulate the contraction of the detrusor and open the internal urethral sphincter
Sympathetic efferents to the bladder are inhibited
Somatic motor efferents to the external urethral sphincter are inhibited; the sphincter relaxes. Urine passes through the urethra; the bladder is emptied

Question 18

steps of urination

Answer 18

see diagram

Question 19

external urethral sphincter

Answer 19

voluntary striated muscles that RELAXES during urination, which relaxes internal urethral sphincter and opening –> causes nicturition

Question 20

Urinary Tract Infections

Answer 20

more common in females; burning sensation during micturition

Question 21

renal calculi

Answer 21

kidney stones

Question 22

bladder cancer

Answer 22

3% of cancers; more common in men

Question 23

kidney cancer

Answer 23

typically in epithelial cels of kidney tubules

Question 24

effects of aging

Answer 24

declined kidney and bladder function

Nephrons decrease in size and number
Tubules are less efficient at secretion and reabsorption
Filtration declines
Recognition of desire to urinate is delayed; can lead to incontinence
Loss of muscle tone in the bladder; can lead to incontinence