CASE 6

Question 1

Nephrons

Answer 1

• water and solutes move from plasma in nephrons that make up most of the kidney
• modify the composition of fluid

Question 2

ureter

Answer 2

modified fluid leaves kidney and passes into the ureter

- there are two ureters, one from each kidney leading to the urinary bladder

Question 3

retroperitoneal

Answer 3

• below the diaphragm and outside the abdominal cavity sandwiched between the membranous peritoneum, which lines the abdomen

Question 4

renal arteries

Answer 4

branch off the abdominal aorta, supply blood to kidneys

Question 5

renal veins

Answer 5

carry blood from kidneys to vena cava inferior

- kidneys receive 20-25% of cardiac output, a lot

Question 6

layers of kidney

Answer 6

1. cortex: outer layer

2. medulla: inner layer

Question 7

renal hilum

Answer 7

central ‘gap’ where its vessels, nerves and urether pass

Question 8

blood flow kidney

Answer 8

1. enters the kidney through renal artery to cortex
2. from afferent arteriole (smaller diameter than efferent –> higher pressure –> more filtration) to glomerulus
3. blood leaves glomerulus through efferent arteriole
4. flows into a second set of capillaries, peritubular capillaries.
5. vasa recta
6. out of kidney through renal vein

Question 9

vasa recta

Answer 9

in juxtamedullary nephrons, the long peritubular capillaries that dip into the medulla (vein going upward from the loop of Henle)

Question 10

renal fascia

Answer 10

• layer of connective tissue encapsulating the kidneys
• separates the renal capsule from overlying pararenal fat
• deeper layers below are called renal capsule and parenchyma (functional tissue of kidney)

Question 11

Bownman’s capsule

Answer 11

• surround the glomerulus

- combination of glomerulus and bowman = renal corpuscule

Question 12

flow nephron

Answer 12

1. bownman’s capsule
2. proximal tubule
3. loop of Henle
   - thin descending limb (impermeable to salt, but permeable to water)
   - ascending limb (impermeable to water, permeable to salts)
4. distal tubule (final control of pH and salts)
5. collecting duct from cortex through medulla and drain into renal pelvis (fluid is now called urine flows into urether)

Question 13

juxtaglomerular apparatus

Answer 13

part where the nephron twists and folds back on itself so that the final part of the loop of Henle passes between the afferent and efferent arterioles.
- regulates the function of each nephron
3 cell types:
1. macula dens (sensitive to concentration of NaCl)
2. granular cells (secrete renin)
3. extraglomerular mesangial cells

Question 14

2 types of nephrons

Answer 14

1. cortical nephrons

2. juxtamedullary nephrons

Question 15

cortical nephrons

Answer 15

-located in cortex and are 85% of all nephrons

Question 16

juxtamedullary nephrons

Answer 16

• located deep in cortex, near medulla.
• long loops of Henle
• produces very concentrated urine, when body needs to save water it uses juxtamedullary nephrons

Question 17

sphincter

Answer 17

• circular muscle that normally maintain constriction of a natural body passage or hole and which relaxes by normal conditions

Question 18

histology of urinary tract

Answer 18

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Question 19

histology of nephron

Answer 19

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Question 20

vascularization of the kidney

Answer 20

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Question 21

filtration

Answer 21

movement of fluid from blood into lumen of the nephron. Only takes place in renal corpuscule

Question 22

reabsorption

Answer 22

process of moving substances in the filtrate back into the blood flowing through peritubular capillaries

Question 23

secretion

Answer 23

removes selected molecules from the blood and adds them to the filtrate in the tubule lumen. Secretion is more selective than filtration, it uses membranes and transport proteins

Question 24

primary function of proximal tubule

Answer 24

reabsorption of isosmotic fluid. filtrate leaving the proximal tubule has the same osmolarity as filtrate that entered

Question 25

primary function loop of henle

Answer 25

primary site creating dilute urine. more solute is reabsorbed than water, filtrate becomes hypoosomotic relative to the plasma.

Question 26

primary function distal tubule and collecting duct

Answer 26

fine regulation of salt and water balance takes place under control of several hormones.

Question 27

Secretion

Answer 27

plasma to tubule lumen

Question 28

excretion

Answer 28

out of the body

Question 29

filtration fraction

Answer 29

the percentage of total plasma volume that filters into the tubule

Question 30

substances leaving plasma have 3 filtration barriers

Answer 30

1. glomerular capillary endothelium 2. a basal lamina 3. the epithelium of Bowman's capsule

Question 31

the glomerular capillary endothelium

Answer 31

- fenestrated capillaries with large pores that allow most components of the plasma to filter through the endothelium. - pores are small enough to prevent blood from leaving capillary

Question 32

a basal lamina

Answer 32

- acellular layer of extracellular matrix - consists of negatively charged glycoproteins, collagen and other proteins - acts as a ruwe zeef

Question 33

the epithelium of Bowman's capsule

Answer 33

- consists of specialized cells: podocytes (located on top of capillaries) - have long cytoplasmic extensions called foot processes that extend from the main cell body - foot processes wrap around the glomerular capillaries and croos with one another, leaving filtration slits

Question 34

glycosaminoglycans

Answer 34

long unbranched polysaccharides consisting of a repeating disaccharide unit. - highly polar and attract water

Question 35

starling forces

Answer 35

- govern the passive exchange of water between the capillary and interstitial fluid 3 starling forces: 1. capillary hydrostatic pressure (Ph) 2. glomerular colloid osmotic pressure (pi) 3. bowman's capsule pressure (Pfluid)

Question 36

capillary hydrostatic pressure

Answer 36

- caused by blood flowing through the glomerular capillaries. - forces fluid through the leaky endothelium - higher at arterial end than venous end

Question 37

glomerular colloid osmotic pressure

Answer 37

- favors fluid movement back into capillaries - constant throughout the whole capillary - arterial end: capillary hydrostatic pressure is higher than colloid osmotic pressure --> filtration takes place - other way around in venous end

Question 38

Bowman's capsule pressure

Answer 38

- opposes fluid movement into capsule | - presence of fluid creates hydrostatic fluid pressure. Fluid movement back into capillaries

Question 39

glomerular filtration rate (GFR)

Answer 39

volume of fluid that filters into the Bowman's capsule per unit time - determined by the net filtration pressure and filtration coefficient

Question 40

GFR as subject to autoregulation

Answer 40

- control process in which the kidney maintains a constant GFR. 1. myogenic response 2. tubuglomerular feedback

Question 41

myogenic response

Answer 41

- ability of vascular smooth muscle to respond to pressure changes - affects afferent arterioles - smooth muscle in arteriole wall stretch --> ion channels and muscle cells depolarize -> opens voltage gated Ca2+ channels --> vascular smooth muscle contracts --> increases resistance --> blood flow diminishes --> decreases filtration pressure in glomerulus

Question 42

tubuglomerular feedback

Answer 42

- paracrine signaling mechanism through which changes in fluid flow through the loop of Henle influence GFR. - modified portion of tubule epithelium is macula densa --> nacl delivery across macula densa increases (as a result of increased GFR) --> send a paracrine signal to neighboring afferent arteriole --> constricts (increasing resistance and decreasing GFR) - the wall of afferent arteriole has juxtaglomerular cells which secrete renin.

Question 43

macula densa sends 2 signals

Answer 43

- can result in dilation in afferent and constriction of efferent --> higher hydrostatic pressure --> increase GFR - can also regulate production of renin which leads to vasoconstriction of efferent arteriole