Exam #4: Overview of Renal Physiology Flashcards Preview

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Flashcards in Exam #4: Overview of Renal Physiology Deck (38):
1

What are the three main regions of the kidney?

1) Cortex
2) Medulla
3) Papilla

2

What is the cortex?

Outer region of the kidney, located under the capsule

3

What is the medulla?

Central region of the kidney; it is divided into an inner & an outer medulla

4

What is the papilla?

Innermost tip of the inner medulla that empties into the minor & major calyces (extensions of the ureter)

5

What is the functional unit of the kidney?

Nephron

6

How many nephrons are contained within each kidney?

~1,000,000

7

What are the two major constituents of the nephron?

1) Glomerulus
2) Renal tubule

8

What is the glomerulus?

- A glomerular capillary network the emerges from an afferent arteriole
- These capillaries are surrounded by Bowman's Capsule, creating Bowman's Space

9

Which direction is blood filtered in in the glomerulus?

Across glomerular capillaries into Bowman's Space

10

Beginning with Bowman's Space, what are the parts of the nephron?

1) Proximal convoluted tubule
2) Proximal straight tubule
3) Loop of Henle
4) Distal convoluted tubule
5) Collecting ducts

11

What are the three parts of the Loop of Henle?

1) Thin descending limb
2) Thin ascending limb
3) Thick ascending limb

12

What is unique about the structure of the proximal convoluted tubule? How do these structural changes impact its function?

- Extensive development of microvilli, called a "brush border" on the luminal side
- Provides a large surface area of reabsorption

13

What are the two different types of nephrons?

1) Superficial cortical nephrons=
- Glomeruli in outer cortex
- Short Loops of Henle that descend only into the outer medulla

2) Juxtamedullary nephrons
- Glomeruli near corticomedullary border
- Large glomeruli
- Longer Loops of Henle that descend into the inner medulla & papilla

14

Which type of nephron functions in the concentration of urine?

Juxtamedullary nephrons

15

Describe the blood supply to the kidney.

- Renal arteries branch off the abdominal aorta
- Branches into
1) Interlobar arteries
2) Arcuate arteries
3) Cortical radial arteries
- Afferent arterioles

*The afferent arterioles deliver blood to the glomerular capillaries, across which ultrafiltration occurs

16

Describe how blood leaves the kidney.

- Blood leaves the glomerulus via the efferent arterioles
- Efferent arterioles deliver blood to a 2nd capillary network, "peritubular capillaries"
- Blood from the peritubular capillaries flows from into the small vein
- Small vein drains into the renal vein

17

What is the function of the peritubular capillaries?

Solutes & water are reabsorbed into the peritubular capillaries

18

How does the blood supply of superficial cortical nephrons differ from juxtamedullary nephrons?

- Superficial cortical= peritubular capillaries branch off efferent arterioles & deliver nutrients to epithelial cells
- Juxtamedullary= peritubular capillaries contain vasa recta that serve as osmotic exchangers for concentrated urine

19

What is unique about the structure of the proximal convoluted tubule? How do these structural changes impact its function?

- Extensive development of microvilli, called a "brush border" on the luminal side
- Provides a large surface area of reabsorption

20

What are the two different types of nephrons?

1) Superficial cortical nephrons=
- Glomeruli in outer cortex
- Short Loops of Henle that descend only into the outer medulla

2) Juxtamedullary nephrons
- Glomeruli near corticomedullary border
- Large glomeruli
- Longer Loops of Henle that descend into the inner medulla & papilla

21

Which type of nephron functions in the concentration of urine?

Juxtamedullary nephrons

22

Describe the blood supply to the kidney.

- Renal arteries branch off the abdominal aorta
- Branches into
1) Interlobar arteries
2) Arcuate arteries
3) Cortical radial arteries
- Afferent arterioles

*The afferent arterioles deliver blood to the glomerular capillaries, across which ultrafiltration occurs

23

Describe how blood leaves the kidney.

- Blood leaves the glomerulus via the efferent arterioles
- Efferent arterioles deliver blood to a 2nd capillary network, "peritubular capillaries"
- Blood from the peritubular capillaries flows from into the small vein
- Small vein drains into the renal vein

24

What is the function of the peritubular capillaries?

Solutes & water are reabsorbed into the peritubular capillaries

25

How does the blood supply of superficial cortical nephrons differ from juxtamedullary nephrons?

- Superficial cortical= peritubular capillaries branch off efferent arterioles & deliver nutrients to epithelial cells
- Juxtamedullary= peritubular capillaries contain vasa recta that serve as osmotic exchangers for concentrated urine

26

List the functions of the kidney.

1) Regulation of water & electrolyte balance
2) Regulation of arterial blood pressure
3) Excretion of metabolic waste
4) Excretion of foreign substances
5) Acid-base regulation
6) Regulation of RBC production
7) Last step of Vitamin D production
8) Gluconeogenesis (most happens in the liver, but the kidney does some during the long fast)

27

What is the lumen of the nephron?

The space inside of the nephron is the "lumen"

28

What is the luminal side of a tubular cell? What is the apical side of a tubular cell?

The cell surface touching the tubular lumen is the apical/ luminal side of the cell

29

What is the basolateral side of a tubular cell?

The cell surface facing the interstitial fluid is the basolateral side

30

What is the function of the Proximal Convoluted Tubule?

ISOSOMOTIC REABSORPTION OF SOLUTE & WATER

Water Reabsorption
Na+, K+ & Cl- reabsorption
Glucose reabsorption
Protein reabsorption
Secretion of organic anions, cations (esp. H+), and drugs

*Note that since water & solute are reabsorbed in the proximal convoluted tubule, this is referred to as "isosmotic"
**Proximal convoluted tubule= isosmotic reabsorption

31

What is the function of the Loop of Henle?

The Loop of Henle is responsible for counter current multiplication, which is necessary for concentration & dilution of urine

*Note that the Thick Ascending Limb is referred to as the "Diluting segment;" REABSORPTION OF NaCl WITHOUT WATER i.e. NaCl is pumped out but water does NOT follow b/c the segment is impermeable to water

32

What is the function of the Distal Convoluted Tubule?

- Similar to thick ascending limb of henle; REABSORPTION OF NaCl WITHOUT WATER
- DILUTION OF TUBULAR FLUID
- Contains "principal cells" with receptors for aldosterone; reabsorbs Na+ & secretes K+
- Intercalated cells reabsorb K+ & secrete H+

33

What is the function of the Collecting Ducts?

- Respond to ADH-->concentration/ dilution of urine

Cortical portion= aldosterone receptors (principal cells)
Medullary portion= urea uniporters

34

How is protein reabsorbed in the proximal tubule?

- Peptides & small proteins are filtered across glomerular capillaries into Bowman's Space; these proteins must be reabsorbed or proteinuria will result
- Small proteins are broken into amino acids, di, or tripeptides WITHIN the LUMEN of the PROXIMAL TUBULE, by peptidases on the apical membrane
- Larger proteins are taken up by endocytotic vesicles, broken down by lysosomes, and resultant amino acids leave across the basolateral membrane

35

Where does ADH act in the kidney?

ADH acts on the entire collecting duct

36

How does ADH control water concentration in urine?

1) Osmolarity of blood is measured by osmoreceptors in the hypothalamus
2) Osmoreceptors shrink when ECF is more concentrated than ICF i.e. high osmolarity in ECF
3) Signal sent to nuceli in hypothalamus to synthesize ADH
4) Posterior pituitary releases ADH
5) ADH acts on the collecting duct to produce more concentrated urine

37

Where is the Macula densa located?

Distal end of the thicken ascending Loop of Henle

38

What is the function of the Macula densa?

The macula densa controls vasodilation and vasoconstriction of the afferent arteriole as part of a mechanism for maintaining relatively constant GFR and renal blood flow despite changes in systemic arterial blood pressure

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