Renal: structure, function, glomerular filtration

Question 1

describe the course of nephron

Answer 1

renal corpuscle > proximal tube > thin descending LH > thin ascending LH > thick ascending LH > distal convoluted tubule > connecting tubule > cortical collecting duct > medullary collecting duct > papillary duct

Question 2

what are the 2 types of nephrons?

Answer 2

1. cortical (85%)

2. juxtamedullary (15%)

Question 3

what are sturctural differences of nephrons?

Answer 3

cortical – short LH & thick ascending LH mostly in the cortex

juxtamedullary – long LH & mainly in the medulla

Question 4

what is the functional role of cortical and juxtamedullary?

Answer 4

cortical - tubular reasorption (removal of solutes and H2O

juxtamed - maintain osmotic gradient in medulla

Question 5

trace blood flow through renal artery

Answer 5

renal artery > interlobar a.a. > arcuate a.a. > interlobular a.a. > afferent arterioles > glomeruli > efferent arteriols > peritubular capillarties or vesa recta

Question 6

how many capillary beds are associated with renal vasculature?

Answer 6

cortical - perttubular nephrons (90% of blood flow)

juxtamed - vesa recta (10% of blood flow)

Question 7

major functions of kidney

Answer 7

• Regulate the volume of body water
• Regulate the balance of inorganic ions
• Regulate body pH
• Excrete metabolic waste products & foreign substances
• Produce hormones and enzymes
• Help regulate blood pressure

Question 8

what is approx. osmolartiy of body fluids?

Answer 8

300 mOsm

Question 9

what are the inorganic ions in osmolarity?

Answer 9

Na
K
Cl
H
HCO3

Question 10

what metabolic waste is is excreted from by the kidney?

Answer 10

urea - nitrogen metab
uric acid - nucleic acid metab.
creatinine - creatinine phosphate
urobilinogen - Hb breakdown

Question 11

what hormones are produced by the kidneys?

Answer 11

erythropoietin (EPO)
Vitamin D3 (Calcitrol)

Question 12

what enzyme is produced in the kidney?

Answer 12

Renin

Question 13

what is EPO? when is produced?

Answer 13

a. protein that stimulates erythrocyte (RBC) production

b. when renal O2 pressure is low

Question 14

what is calcitrol? what’s its function?

Answer 14

a. steroid

b. increase Ca and PO4 (phosphate) uptake in intestine

Question 15

what is renin? What’s its function?

Answer 15

a. enzyme
b. hydrolyzes angiotensinogen to angiotensin 1 (Ang I). Ang I is converted to Ang II by angiotensin converting enzyme (ACE)
c. Renin increases arterial B/P

Question 16

what is angiotensin?

Answer 16

peptide hormone that causes vasoconstriction

Question 17

what causes H2O retention in kidney?

Answer 17

low MAP or blood volume > ADH/Vasopressin secretion > H2O retention

Question 18

what causes an increase in MAP (in reference to kidneys)

Answer 18

low MAP or blood volume > Renin secrection > angiotensinogen conversion to Ang I > Ang I converted to Ang II (by ACE) > Vasoconstriction

Question 19

What causes Na retention in the kidney?

Answer 19

low MAP or blood volume > Renin secrection > angiotensinogen conversion to Ang I > Ang I converted to Ang II (by ACE) > aldosterone secrection > Na retention

Question 20

How is water ingestion triggered ?

Answer 20

thirst mechanism triggered by Ang II

Question 21

what structures make up the juxtaglomerular apparatus (JGA)? what arteriole is it associated with?

Answer 21

a. juxtaglomerular cells and macula densa of distal tubule

b. afferent arterial

Question 22

What structures compose the renal corpuscle?

Answer 22

bowman’s capsule (2 layers – parietal & visceral (podocyte - foot prosesses)
glomerular capillary

Question 23

What 3 glomerular filtration barriers?

Answer 23

1. endothelial cells
2. basil lamina
3. epithelial cells (podocytes)

Question 24

What is true of endothelial cells?

Answer 24

1. they are fenestrated
2. plasm fluides freely permeate
3. composed of pores
4. part of the capillary lumen

Question 25

what is true of the basil lamina?

Answer 25

1. negatively charged 2. repels negativly charged proteins 3. extracellular matrix 4. located between endothelial and epithelial cells

Question 26

what is true of epithelial cells?

Answer 26

1. a.k.a. podocytes 2. octopus like structures 3. compose filtration slits 4. part of the lumen of bowan's capsule

Question 27

how does glomerular filtration occur?

Answer 27

occurs due to the difference between a blood pressure in the capillaries and a pressure in Bowman’s space.

Question 28

which force favors filtration? opposes it?

Answer 28

a. favors - glomerular capillary pressure (Pgc) in mmHg | b. opposes - fluid pressure in Bowmans space (Pbs) and oncotic pressure ( ) (in mmHg)

Question 29

what causes oncotic pressure?

Answer 29

large proteins in the plasma | oncotic pressue is higher than the pressure in bowmans space

Question 30

calculate net glomerular filtration pressure

Answer 30

cut and paste pic

Question 31

what is renal blood flow rate?

Answer 31

1 L/min | 20% of resting CO

Question 32

what is renal plasma flow rate?

Answer 32

625 mL/min (approx. 900 L/day)

Question 33

how much of the plasma gets filtered in Bowman's capsule? what is this known as?

Answer 33

a. approx. 180 L/day @ 125 mL/min (20% of renal plasma flow) the rest passes through glomerular capillaries into efferent arterioles b. GRR - glomerular filtration rate

Question 34

What is true of plasma filtration?

Answer 34

1. 99% of filtered plasma is reabsorbed 2. reabsorb approx 178-179 L/day 3. excrete approx 1-2 L/day 4. Plasma vol = 3 L 5. filtered approx 60 times/day

Question 35

How is GFR controlled?

Answer 35

constriction of dilation of afferent or efferent arterioles

Question 36

how is the pressure between the arteries and capillaries in bowman's space decreased ?

Answer 36

1. constriction of afferent arteriole (increase resistance) OR dilation of efferent arteriole 2. decreases glomerular capillary pressure (Gcp) 3. decreases GFR

Question 37

How is the pressue between the arteries and capillaries in bowman's space increased?

Answer 37

1. Constriction of efferent arteriole OR dilation of afferent? 2. increases (Gcp) "dam's it up" 3. increases GFR

Question 38

how to remember how GFR is decreased

Answer 38

``` "C.A.D.E. decreases GFR" Constricted Afferent arterioles or Dilated Efferent arterioles ``` NOTE: increase GFR is C.E.D.A

Question 39

what are extrarenal requlators of afferent and efferent arterioles ?

Answer 39

neural inputs | hormones

Question 40

what are the intrarenal regulators of afferent and efferent arterioles?

Answer 40

a.k.a autoregulation (independent of neural and homonal input

Question 41

What are the mechanisms of intrarenal regulation?

Answer 41

myogenic | tubuloglomerular feedback

Question 42

Describe the myogenic mechanism

Answer 42

Smooth muscles of afferent arterioles are stretched in response to high blood pressure → Stretch-activated ion channels are activated, leading to muscle contraction → reduces the volume of blood → reduces Pgc. Conversely, muscle relax → raise Pgc

Question 43

Describe the tubuloglomerular feedback mechanism

Answer 43

Macula densa cells sense changes in luminal salt load → release paracrines → alter smooth muscle contraction in afferent arterioles → adjust Pgc

Question 44

what cells receive the neuronal and hormonal inputs ?

Answer 44

mesangial cells (smooth muscle cells that surround the glomerular capillaries constriction of cells reduce surface area of capillaries