CHAPTER 20 URINARY SYSTEM

A. The urinary system, made of kidneys, tubular ureters, a urinary bladder & a tubular urethra is vital to life.
B. It functions to remove substances from blood by forming urine that is excreted.
C. It also helps regulate some metabolic processes.
D. Metabolic processes such as blood pressure, RBC production, & absorption of calcium.

I. Kidneys: where are they, what is their structure, & what do they do?

A. Location Fig. 20.1

1. Each is located in a depression high on posterior wall of _________________________________

2. Upper border: at level of ___________________________________________ vertebra

3. Lower border: at level of ____________________________________________ vertebra

4. Left kidney usually __________________ centimeters _______________________ than right one

5. ____________________________________________ ************


B. Structure Fig. 20.4a, Fig. 20.4b, Fig. 20.4c, Fig. 20.5
1. Reddish brown, ___________________________________ with smooth surface
2. 12 cm long, 6 cm wide, 3 cm thick

3. Lateral surface is ______________________, medial surface ________________________

4. Medial surface contains depression leading into hollow chamber: ____________________
5. Entrance to sinus: hilum - passage for blood vessels, nerves, lymphatics, ureter FIG. 20.1

6. Superior end of ureter: ______________________________ with major & minor calyces

7. Renal ____________________________________________ project into renal sinus

8. Renal ________________________: contains cone shaped masses of tissue (renal pyramids)

9. _________________: granular shell around medulla; forms renal columns; contains nephrons


C. Function: Regulate volume, composition & pH of body fluids

1. Remove ________________________________________ from blood; excrete these wastes

2. Control rate of RBC formation: hormone - ______________________________________

3. Regulate blood pressure: enzyme - ____________________________________________

4. Regulate absorption of calcium ions: ____________________________________________

II. Renal vessels Fig. 20.6
 
III. Nephron: functional unit of kidney; 1 million in each kidney; Nephrons are made of Fig. 20.9

A. _______________: a _______________ unit made of a mass of blood capillaries (glomerulus)

1. with a surrounding thin walled sac (___________________________________)

B. Glomerular capsule: ___________________________ at end of tubule;
1. receives fluid from glomerulus; made of 2 layers Fig. 20.15

2. Visceral layer: covers the glomerulus; cells are highly modified epithelial cells:________________

a. Extensions from body of podocyte: ____________________; clefts between extensions: slit pores

3. Parietal layer: continuous with visceral layer & wall of tubule; made of squamous epithelial cells

C. Tubule: proximal convoluted tubule, nephron loop (Loop of Henle)
D. made of descending limb & ascending limb; distal convoluted tubule;

E. ______________________________ : convoluted tubules merge in the cortex to form ducts;
F. ducts become larger as they join other ducts; empty into a minor calyx through opening in a renal papilla
G. See Fig. 20.9 & Fig. 20.10
H. Two types of nephrons: cortical nephrons & juxtamedullary nephrons Fig. 20.12, Fig.20.13

1. Cortical nephrons: have corpusles in the renal _______ & _______ that do not reach the renal medulla

2. Juxtamedullary nephrons: corpusles close to ______________________

3. & nephron loops extend ___________________into medulla.

4. 20% of nephrons. Important in regulating ______________________ Fig. 20.12

IV. Juxtaglomerular Apparatus Fig. 20.11a, Fig. 20.11b

A. Distal convoluted tubule passes between afferent & efferent arterioles; makes contact

B. Point of contact: epithelial cells of DCT are narrow densely packed; form the __________________.

C. Large, vascular ___________________________________ cells are in wall of afferent arteriole
D. near attachment to glomerulus;called juxtaglomerular cells
E. Macula densa + juxtaglomerular cells == juxtaglomerular apparatus

V. Blood supply of nephron

A. See Fig. 20.14

VI. Formation of Urine

A. Processes involved in urine formation

1. Glomerular filtration: ___________________ move from glomerular capillaries into renal tubules

2. Tubular reabsorption: some chemicals move ____________________________________________

3. Tubular secretion: some chemicals move from ______________________________ capillaries into renal tubules

4.URINARY EXCRETION == glomerular filtration, + tubular secretion, - tubular reabsorption

B. Glomerular filtration

1. ____________ + small dissolved molecules & _________ are filtered out of plasma at the _________

a. Small holes (____________________________) allow molecules to leave glomerulus Fig. 20.15

2. These substances enter the ____________________________________________

3. Glomerular filtrate is almost the same as tissue fluid in other parts of body.

4. Glomerular filtrate == water + solutes (as in blood plasma � large proteins)

5. Glomerular filtrate contains Chart 20.1
1. Water
2. Glucose
3. Amino acids
4. Urea
5. Uric acid
6. Creatine
7. Creatinine
8. Sodium
9. Chloride
10. Potassium
11. Calcium
12. Bicarbonate
13. Phosphate
14. Sulfate

C. Why do the substances go through the walls of the glomerular capillary? Fig.20.15, Fig. 20.16, Fig. 20.17

1. ____________________________________: hydrostatic pressure of blood inside

2. ____________________________________ of the blood plasma in the glomerulus
(higher than that of the filtrate because of plasma proteins)

3. ______________________________________ pressure inside glomerular capsule

4. Plasma proteins cause the osmotic pressure of plasma to be higher than that of the glomerular filtrate.
a. This draws water back into glomerular capillaries.

D. Net pressure forcing substances out of glomerulus == filtration pressure
1. Filtration pressure =
a.glomerular capillary hydrostatic pressure minus
b.capsular hydrostatic pressure plus glomerular capillary osmotic pressure

E. Glomerular Filtration Rate: GFR �how much is filtered per minute DEPENDS ON

1. Glomerular hydrostatic pressure: depends on _________________of the afferent & efferent vessels

a. Sympathetic impulses may constrict afferent arterioles -----à blood flow _____, filtration rate ____

b. When efferent arteriole constricts --------à blood backs up into glomerulus ---à filtration rate ____

c. When efferent arteriole dilates ----------à blood flows out of glomerulus ----à filtration rate _____

2. Osmotic pressure of glomerular plasma influences filtration pressure & rate of filtration

a. Proteins remaining in plasma _____ osmotic pressure in glomerulus ---à filtration can _____

b. Decrease in plasma proteins concentration -------à increase filtration rate

3. Hydrostatic pressure in glomerular capsule
a. Obstructions (stones, enlarged prostate)

b.----à fluids back up into renal tubules ---à pressure _____ ---à filtration _________


4. GFR for adults == ___liters (45 gallons) in 24 hours; thus all plasma is filtered thru glomeruli 60 x day

F. Regulation of filtration rate

1. _________________________________: keeps GFR constant

2. __________________________ nervous system fibers stimulate vascular smooth muscle of arterioles

a. When blood pressure & volume ___ ---à

b. vasoconstriction of afferent art ---à

c.GFR ___ ---à H₂O conserved

d. __________________________--à vasodilation of afferent art. --à ______ in GFR -à

e. H₂O ___________ through urine

3. Renin-angiotensin system Fig. 20.18***************

a. Regulates renal _________________ excretion

b. Renin (enzyme) secreted by juxtaglomerular cells of afferent arterioles

c. Blood pressure ____ -------à

d.sympathetic nerves & renal baroreceptors in afferent arteriole ----à stim secretion of renin

e. Decrease in _______________________ stimulate secretion of renin

f. ACE from lungs

g. Renin + angiotensinogen ------à angiotensin I --------------------------------à angiotensin II

h. ----à vasoconstriction, ____ aldosterone secretion, _____ ADH secretion, ______ thirst

1.) Angiotensin II ------à vasoconstriction of afferent & efferent arterioles: autoregulation
2.) Angiotensin II -----à stim prod of aldosterone
3.) ----à stim ___ reabsorption in distal tubules --à H₂O reabsorption

4. Atrial natriuretic peptide (ANP)

a. ANP secretion __________ when atria of heart stretches due to incr. blood volume

b. Stim. sodium excretion by _______ GFR

G. Tubular reabsorption Fig 20.19, Fig 20.20

1. Substances in tubular fluid ---à transported through epithelium ---à into interstitial fluid
2. ---à diffuse into blood in capillaries

3. Most occurs in _____________________________convoluted tubule: why? Cells with microvilli

4.form a brush border == ________ surface area
5. DRAW:
 

 
 
 
 
 
6. Proximal convoluted tubules:

a.Glucose reabsorbed by ______________________________;

b.Water reabsorbed by ___________
c.Amino acids reabsorbed (only a few found in urine);

d. albumin (small plasma protein) reabsorbed by _______________ through brush border;
e. creatine; lactic acid, citric acid, uric acid & ascorbic acid; phosphate,
f. sulfate, calcium, potassium, & sodium ions all reabsorbed by active transport.

7.Note: 70% of the filtered ions are reabsorbed in proximal convoluted tubule.
8. Distal convoluted tubules: distal tubule & collecting duct are impermeable to water.
9. Na⁺ is reabsorbed by active transport as fluid moves through loop; Na⁺ & Cl^- absorbed in DCT
10. &collecting duct because of aldosterone's influence.
11. Almost all Na⁺ & 97-99% water is reabsorbed.
12. Very small changes in tubular reaborption of water & sodium = huge changes in urinary excretion

VII. Regulation of Urine Concentration & Volume

A. Fluid reaching DCT is _________________ to surroundings (changes occurring through the loop).

B. Interstitial fluid surrounding ducts is _______________________________.

C. DCT & duct are __________________________________ to water.

D. Therefore, water accumulates inside tubule & may be excreted as dilute urine;

E. however, ____________ (from posterior lobe of pituitary)

F. causes increase in permeabilility of epithelial cell linings of DCT

G. & collecting duct. Water moves out by osmosis into hypertonic medulla. Fig. 20.21

H. Countercurrent mechanism Fig. 20.24 & Fig. 20.25 ******

I. Countercurrent mechanism of vasa recta Fig. 20.26 *****

VIII. Urea & uric acid excretion

A. Urea: a by-product of __________________ catabolism in liver (amt depends on protein in diet)

1. Enters tubule by filtration
2. 50% reabsorbed passively by diffusion

B. Uric acid: a by-product from metabolism of organic bases in nucleic acids;
1. secreted into tubule;
2. reabsorbed by active transport.

IX. Tubular secretion Fig. 20.21, Fig. 20.22

A. Epithelium of PCT actively secretes penicillin & histamine into fluid

B. _________ actively secreted by tubule: urine is acidic
C. Some K⁺ secreted by DCT & collecting duct

X. What does urine contain?

A. Page 818

XI. Review Fig. 20.28, Fig.20.29

A. the anatomy of the ureters Fig. 20.32a, Fig. 20.32b
B. & bladder (esp. its position in the male & female �see page 869),
C. & urethra.

XII. What is the micturition reflex? dialysis, peritoneum