Urinary System Part 2

Question 1

What are the three processes involved in urine formation and adjustment of blood composition?

Answer 1

• Glomerular filtration
• tubular reabsorption
• Tubular secretion

Question 2

Glomerular filtration

Answer 2

produces cell and protein-free filtrate

Question 3

Tubular Reabsorption

Answer 3

selectively returns 99% of substances from filtrate to blood

Question 4

Tubular Secretion

Answer 4

selectively moves substances from blood to filtrate

Question 5

What is the first step of urine formation?

Answer 5

Filtration

Question 6

What are the layers of the filtration barrier?

Answer 6

• capillary endothelium
• basement membrane
• podocytes of glomerular capsule

Question 7

Capillary endothelium (filtration)

Answer 7

• fenestrated; very permeable
• allows passage of anything smaller than a cell

Question 8

Basement membrane (filtration)

Answer 8

• not as permeable
• blocks all but small proteins

Question 9

Podocytes of glomerular capsule (filtration)

Answer 9

creates filtration slits for flow into capsular space

Question 10

Glomerular filtration is a ________ _____. This means that there is no ________ _________ required

Answer 10

passive process,
no metabolic energy

Question 11

In glomerular filtration what molecules are able to pass?

Answer 11

allows molecules smaller than 3 nanometers to pass
water, glucose, amino acids, nitrogenous wastes

Question 12

What happens to the plasma proteins in the blood during glomerular filtration?

Answer 12

• plasma proteins remain in the blood
• prevents a loss of all water to capsular space
• proteins in filtrate may indicate filtration membrane problem

Question 13

Pressures that affect filtration: outward pressures

Answer 13

• forces that promote filtrate formation
• hydrostatic pressure in glomerular capillaries is essential glomerular blood pressure
• chief force pushing water and solutes out of the blood

Question 14

Pressures that affect filtration: inward pressures

Answer 14

• forces inhibiting filtrate formation
• hydrostatic pressure in capsular space: filtrate pressure in capsule
• osmotic pressure in capillaries: pull of proteins in blood

Question 15

What is the golerular filtration rate equal to?

Answer 15

the total volume of filtrate formed by all of the glomeruli of both kidneys each minute

Question 16

The magnitude of NFP is directly proportional to ___

Answer 16

GFR (glomerular filtration rate)

Question 17

Net filtration pressure (NFP)

Answer 17

sum of forces, pressure responsible for filtrate formation

Question 18

Glomerular filtration rate (GFR)

Answer 18

volume of filtrate formed per minute by both kidneys
primary pressure is glomerular hydrostatic pressure

Question 19

Constant glomerular filtration rate is important as it allows the kidneys to make and filtrate and maintain……

Answer 19

extracellular homeostasis.

Question 20

How does glomerular filtration rate affect systemic blood pressure?

Answer 20

• increased GFR causes increased urine output, lowers blood volume, and thus blood pressure

Question 21

What is the goal of extrinsic controls?

Answer 21

to maintain systemic blood pressure
- nervous system and endocrine mechanisms are main extrinsic controls that override intrinsic controls

Question 22

Intrinsic autoregulatory controls of glomerular filtration?

Answer 22

• maintinas the GFR when arterial blood pressure is 80-180 mmHg

Question 23

what are the two types of renal autoregulation of glomerular filtration?

Answer 23

1. Myogenic mechanism
2. tubuloglomerular feedback mechanism

Question 24

What is the Myogenic Mechanism?

Answer 24

• Afferent arteriole smooth muscle contracts when stretched
• the increased blood pressure causes muscle contraction and constriction of afferent arterioles –>restricts blood flow into glomerulus (decrease hydrostatic pressure) —> decreased BP causes dialtion of afferent arterioles
• both help maintain normal GFR despite normal fluctuations in blood pressure

Question 25

Tubuloglomerular feedback mechanism

Answer 25

- flow-dependent mechanism directed by macula densa cells (respond to filtrate's NaCl concentration) - if GR increases, filtrate flow rate increases causing high NaCl levels in filtrate (constriction of afferent arteriole, which lowers NFP and GFR, allowing more time for NaCl reabsorption). - opposite mechanism for decreased GFR

Question 26

Juxtaglomerular complex (JCG)

Answer 26

- each nephron has one - involves modified portions of distal portion of ascending limb of nephron loop - important in regulating GFR and blood pressure

Question 27

What are the 2 cell populations seen in JGC?

Answer 27

- macula densa - granular cells

Question 28

Macula Densa

Answer 28

- tall closely packed cells of ascending limb - contain chemoreceptors that sense NaCl content of filtrate

Question 29

Granular cells (JG cells)

Answer 29

- enlarged smooth muscle cells of arteriole - act as mechanoreceptors to sense blood pressure in afferent arteriole - contain secretory granules that contain enzyme renin

Question 30

Extrinsic controls: Neural and Hormonal Mechanisms

Answer 30

- regulate GFR to maintain systemic blood pressure - override renal intrinsic controls if blood volume and pressure need to be increased

Question 31

How do the extrinsic controls of GFR preserve blood volume and pressure?

Answer 31

- through the sympathetic nervous system - norepinephrine is released by sympathetic nervous system and epinephrine is released by the adrenal medulla causing: - sytemic vasoconstriction (increasing BP) - afferent arteriole contriction, decrease GFR, less urine - blood volume and pressure increases

Question 32

What are the sympathetic effects?

Answer 32

- constricts afferent arteriole - helps maintain BP and shunts blood to heart and muscles

Question 33

What is the main mechanism for increasing blood pressure?

Answer 33

the renin-angiotensin-aldosterone mechanism

Question 34

What are the three pathways to renin release by granular cells of afferent arterioles when blood pressure drops significantly?

Answer 34

1. Direct stimulation of granular cells by sympathetic nervous system 2. Stimulation by activated macula densa cells when filtrate NaCl concentration is low 3. Reduced stretch of afferent arteriole

Question 35

Study the renin-angiotensine-aldosterone system

Question 36

Proximal convolute tubule (PCT) mainly functions in__________. (Renal Tubule)

Answer 36

reabsorption

Question 37

What are the cells of the Proximal convoluted tubule?

Answer 37

cuboidal cells with dense microvilli that form brush border (increase surface area).

Question 38

Nephron loop allows us to produce a _________ ________.

Answer 38

hypertonic urine (aka the loop of Henle)

Question 39

Describe the major aspects of the nephron loop

Answer 39

- U shaped structure - descending limb: permeable to water - ascending limb: impremeable to water, actively transports (pumps) solute into interstitial fluid

Question 40

The nephron loop produces high osmolarity of the _______ ______ deep in the medulla that is 4X that of cortex and plasma.

Answer 40

interstitial fluid

Question 41

What does the distal convoluted tubule (DCT) mainly function in?

Answer 41

secretion

Question 42

what are the cells found in the distal convoluted tubule?

Answer 42

- cuboidal cells with very few microvilli - confined to cortex

Question 43

What are the collecting ducts?

Answer 43

- recieve filtrate from many nephrons - run through the medullar pyramids and igve them their striped appreaance - ducts fuse together to deliver urine into minor calyces and toward major calyces - maintain water and Na+ balance - ADH works here