HUBS192 Lecture 29 - Urinary System II, The Nephron

Question 1

approximately how many nephrons per kidney?

Answer 1

approx. 1 million per kidney

Question 2

what does the juxtamedullary nephron describe?

Answer 2

describes where the renal corpuscle and the glomerulus meet where they are located

Question 3

what are the 2 types of nephrons?

Answer 3

1) cortical nephrons

2) juxtamedullary nephrons

Question 4

where are cortical nephrons located?

Answer 4

lie mainly in the cortex with some parts in the medulla

Question 5

how many percent does the cortical nephrons make up of the nephrons in the body?

Answer 5

85%

Question 6

where is the renal corpuscle of juxtamedullary nephrons located?

Answer 6

renal corpuscle right at the border between the medulla and the cortex above it

Question 7

where are juxtamedullary nephrons located?

Answer 7

extend deep into the medulla

Question 8

what are juxtamedullary nephrons important for?

Answer 8

important for the formation of concentrated urine

Question 9

what are the 3 functions of the nephron?

Answer 9

1) selectively filter blood
2) return to blood anything to be kept/wanted
3) carry waste away for storage & explusion

Question 10

what 3 parts are each nephron comprised of?

Answer 10

1) a glomerular capsule
2) renal tubules
3) a collecting duct

Question 11

what 2 capillaries are each nephron associated with?

Answer 11

1) a glomerulus (glomerular capillaries)

2) peritubular capillaries

Question 12

what are glomerular capillaries?

Answer 12

thin walled single layer of fenestrated endothelial cells

Question 13

how is blood fed and drained through fenestrated endothelial cells?

Answer 13

fed by afferent arterioles and drained by efferent arterioles

Question 14

what is tightly regulated at the glomerular capillaries?

Answer 14

blood pressure is tightly regulated

Question 15

what are the glomerular capillaries specialised for?

Answer 15

specialised for filtration

Question 16

why are peritubular capillaries called peritubular capillaries?

Answer 16

because they wrap around renal tubules

Question 17

what are peritubular capillaries specialised for?

Answer 17

specialised for absorption

Question 18

what do peritubular capillaries carry?

Answer 18

carries filtered blood from the efferent arterioles

Question 19

what do peritubular capillaries receive?

Answer 19

receives reabsorbed filtrate from the nephron

Question 20

where can the peritubular capillaries secrete into?

Answer 20

secrete into the nephron

Question 21

what are vasa recta?

Answer 21

extensions that follow loops deep into the medulla and are only found in juxtamedullary nephrons

Question 22

where are vasa recta only found with?

Answer 22

only found with juxtamedullary nephrons

Question 23

what is the glomerulus?

Answer 23

bundle of glomerular capillaries

Question 24

what is the glomerulus capsule enclosed by?

Answer 24

enclosed by the glomerular capsule

Question 25

what is the renal corpuscle the site of?

Answer 25

site of the filtration barrier

Question 26

what is the first part of the nephron?

Answer 26

the glomerular capsule

Question 27

why is the outer parietal layer of the glomerular capsule made up of simple squamous cells?

Answer 27

to stop whatever is filtered from leaking back out

Question 28

what is filtrate?

Answer 28

what is taken out of the blood that may become urine before it travels down the nephron tubes

Question 29

what are the 3 layers of the glomerular capsule from outer to inner?

Answer 29

1) outer parietal layer composed of simple squamous cells 2) capsular space which receives filtrate 3) inner visceral layer composed of podocytes

Question 30

what is the outer parietal layer of the glomerular capsule made up of?

Answer 30

simple squamous cells

Question 31

what is the inner visceral layer of the glomerular capsule made up of?

Answer 31

podocytes

Question 32

what does the capsular space receive?

Answer 32

receives filtrate

Question 33

what are filtration slits?

Answer 33

gaps formed between the pedicels

Question 34

how do podocytes wraps around capillaries?

Answer 34

by interdigitating and surrounding the glomerular capillaries

Question 35

what is the function of pedicels?

Answer 35

pedicels interdigitate and sit over the fenestrations making filtration more selective

Question 36

what are pedicels?

Answer 36

branches that have formed intertwining foot processes

Question 37

what forms between pedicels?

Answer 37

filtration slits

Question 38

how does blood pass through the filtration slits?

Answer 38

filtered blood (filtrate) goes through the filtration slits and passes into the capsular space

Question 39

what is the main function of the filtration barrier?

Answer 39

restrict what passes through mainly based on size | -mostly proteins and RBC's are too large to be filtered into the nephron

Question 40

what is the filtration barrier?

Answer 40

blood-urine barrier or glomerular capsular membrane

Question 41

where does the filtration barrier lie between?

Answer 41

lies between the blood and the capsular space

Question 42

what does the filtration barrier allow?

Answer 42

allows the free passage of water and small molecules

Question 43

what are the 3 layers of the filtration barrier?

Answer 43

1) fenestrated endothelium of the glomerular capillary 2) fused basement membrane 3) filtration slits between the pedicels of the podocytes

Question 44

what happens after filtration?

Answer 44

- not everything that is filtered is excreted - some filtrate is absorbed - some of what wasn't filtered is secreted into

Question 45

what is urine in terms of filtration?

Answer 45

urine = filtered - reabsorbed + secreted

Question 46

what is the proximal convoluted tubule (PCT)?

Answer 46

the bulk reabsorption site

Question 47

where is the proximal convoluted tubule (PCT) located?

Answer 47

located in the cortex surrounded by peritubular capillaries

Question 48

what are the 5 components that make up the structure of the proximal convoluted tubule (PCT)?

Answer 48

- cuboidal epithelial cells - dense microvilli (brush border) on the luminal membrane - highly folded basolateral membrane - many mitochondria for active transport - leaky epithelium

Question 49

where does the nephron loop always loop down into?

Answer 49

loops down into the medulla

Question 50

what is the relationship between length of the nephron loop and urine?

Answer 50

length is important in the production of dilute/concentrated urine

Question 51

what is the nephron loop surrounded by?

Answer 51

surrounded by vasa recta (juxtamedullary nephrons only)

Question 52

what are the 4 parts of the structure of the nephron loop?

Answer 52

1) thick descending limb - like the proximal convoluted tube 2) thin descending limb - composed of simple squamous epithelium 3) thin ascending limb - composed of simple squamous epithelium 4) thick ascending limb - like the distal convoluted tube

Question 53

what are the thin descending limb and the thin ascending limb made up of?

Answer 53

simple squamous epithelium

Question 54

what is the relationship between different areas of the nephron loop and permeability?

Answer 54

different areas have different permeabilises to water and sodium

Question 55

what is the function of the distal convoluted tube (DCT)?

Answer 55

fine tuning

Question 56

what is the distal convoluted tube (DCT) composed of?

Answer 56

cuboidal epithelium but thinner layer than in the proximal convoluted tube (PCT)

Question 57

what are the 3 structures that make up the distal convoluted tube (DCT)?

Answer 57

1) no bush order because of few microvilli 2) fewer mitochondria 3) reabsorption regulated mailing by aldosterone

Question 58

what occurs at the collecting duct?

Answer 58

receive filtrate from several distal convoluted tubes (DCTs) that drain into one collecting duct which empty at a papilla

Question 59

what is the function of a collecting duct?

Answer 59

fine tuning

Question 60

what 3 structures is the collecting duct made up of?

Answer 60

1) wall of simple cuboidal epithelium 2) principal cells for absorption 3) intercalated cells for acid/base balance

Question 61

what is the function of principal cells?

Answer 61

reabsorption

Question 62

what is the function of intercalated cells?

Answer 62

acid/base balance

Question 63

what is reabsorption regulated by in the collecting duct?

Answer 63

regulated by antidiuretic hormone (ADH) and aldosterone

Question 64

what is the juxtaglomerular apparatus (JGA)?

Answer 64

specialised zone in every nephron

Question 65

where is the juxtaglomerular apparatus (JGA) located?

Answer 65

located where the distal convoluted tube (DCT) lies against the afferent arteriole

Question 66

what are the macula densa cells

Answer 66

chemoreceptors in the distal convoluted tube (DCT) that detect sodium levels

Question 67

what are juxtaglomerular cells?

Answer 67

mechanoreceptors in the afferent arteriole that detect blood pressure through stretch

Question 68

what are mechanoreceptors?

Answer 68

stretch receptors that detect blood pressure

Question 69

what is the function of the juxtaglomerular apparatus (JGA)?

Answer 69

controls glomerular filtration rate ensuring that system is working at full capacity and stabilises blood pressure

Question 70

what term is used when passing through the nephron?

Answer 70

filtrate

Question 71

what term is used when passing through the kidney?

Answer 71

urine

Question 72

what are the cells that form the visceral layer of the glomerular capsule called?

Answer 72

podocytes

Question 73

what are the cells of the juxtaglomerular apparatus (JGA) on the afferent arteriole called?

Answer 73

juxtaglomerular

Question 74

what type of epithelial cells would you find in nephron loop?

Answer 74

cuboidal with microvilli brush border at part closest to the proximal convoluted tube (PCT), simple squamous, cuboidal with few microvilli at part closest to distal convoluted tube (DCT)

Question 75

what are the 2 capillary beds associated with the nephron?

Answer 75

glomerular and peritubular

Question 76

which type of nephron is important for the production of concentrated urine?

Answer 76

juxtamedullary