Physiology Of Kidneys(physiology)

Question 1

List 5 functions of the kidneys

Answer 1

-Role in homeostasis
-Regulation of BP
-Haematopoietic function
-Excretion of waste
-Calcium homeostasis

Question 2

What are the two types of nephrons, state the differences.

Answer 2

•Cortical nephron:
-Has a short loop of henle.
-Glomeruli is in the outer cortex.

•Juxtamedullary nephron:
-Has a large glomeruli
-Has a long loop of henle
-Glomeruli is in the corticomedullary junction
-Has juxtaglomerular apparatus for renin secretion.

Question 3

What is the diff btwn the blood supply of cortical nephron and juxtamedullary nephron?

Answer 3

-Cortical:- has afferent and efferent arterioles as well as peritubular capillaries.
-Juxtamedullary- Has vasa recta in addition to those arteries of cortical nephron.

Question 4

In which blood vessels does blood flow from the renal arteries to renal veins

Answer 4

Renal arteries—Segmental arteries—Interlobar artery—Arcuate artery—Interlobar artery—Afferent arteriole—Glomerulus—Effrerent arteriole—Peritubular capillaries(cortical) /—Vasa recta(juxta)—Interlobar vein—Arcuate vein—Interlobar vein—Renal veins.

Question 5

What are the functions of a nephron(6)

Answer 5

•Production of filtrate.
•Excretion
•Reabsorption of water and ions.
•Reabsorption of all organic nutrients.
•Secretion of waste into tubular fluid.
•Modification of fluid volume and osmolarity.

Question 6

How much fluid is filtrated per day

Answer 6

180 litres

Question 7

The filtration membrane of the nephron consists of:(3)

Answer 7

-Capillary endothelial cells
-Basement membrane
-Tubular epithelial cells

Question 8

What perpetuates the glomerular filtration?

Answer 8

Glomerullar capillary pressure (hydrostatic pressure)

Question 9

How much of the plasma goes for glomerular filtration and how much is excreted?

Answer 9

-80%, less than 1%

Question 10

Why can’t proteins get filtered into the convoluted tubules?

Answer 10

Because the bowman’s capsule has negatively charge glycoproteins which repels with the plasma proteins.

Question 11

The basement membrane consist of three layers namely:

Answer 11

Lamina rara interna- fused to endothelium
Lamina densa
Lamina rara externa- fused to epithelium

Question 12

What is the function of lamina densa?

Answer 12

Counts the number of sodium ions moving past to the distal convoluted tubule.

Question 13

What cells are found in the epithelium of the filtration membrane, that is attached to the BM?

Answer 13

Podocytes

Question 14

What three types of pressure affects glomerular ultrafiltration? What role do each play?(3)

Answer 14

•Glomerular capillary pressure (pressure exerted by blood on glomerular capillaries)- promotes filtration
•Hydrostatic pressure in the bowman’s capsule (exerted by the filtrate)-opposes filtration
•Colloid osmotic pressure (Exerted by plasma proteins)- Against filtration

Question 15

What equation is used to calculate the net filtration pressure?

Answer 15

Net filtration pressure= Glomerular capillary pressure - Colloid osmotic pressure - Hydrostatic pressure

Question 16

What is meant by Glomerular Filtration Rate (GFR)?

Answer 16

Total quantity of ultrafiltrate formed in both kidneys per unit time.

Question 17

Two factors that influence the GFR

Answer 17

Net filtration pressure
Filtration coefficient

Question 18

Two ways in which renal blood flow (RBF) can be regulated

Answer 18

Autoregulation
Non-renal factors

Question 19

Explain the myogenic response theory of autoregulation

Answer 19

•Stretch of the afferent arteriole smooth muscle cell wall (e.g. high BP), this cause pressure gated ion channels to open, muscle depolarizes, voltage gated calcium channels open.
•Huge influx of calcium ions inside the cells.
•Muscle contraction and increased resistance, caused decrease in RBF and filtration pressure.
•Blood pressure decreases, relaxation of afferent arteriole, GRF also decreases.

Question 20

Explain the tubuloglomerular feedback theory of autoregulation of RBF

Answer 20

-GRF increases
-Flow through tubules increases.
-Flow past the macula densa increases.
-Paracrine from macula densa causes afferent arteriole to constrict.
-Increased resistance in afferent arteriole.
-Hydrostatic pressure decreases.
-GRF decreases.

Question 21

What are the non-renal factors affecting RBF?(2)

Answer 21

Hormones and autonomic neurons
Intergrated centers outside kidney can override local controls.

Question 22

What are the factors causing vasoconstriction, which can affect the RBF

Answer 22

•Sympathetic nerves and catecholamines
•Angiotensin 2, endothelins, thromboxane A2, ADH.

Question 23

Factors causing vasodilation which can affect the RBF

Answer 23

High GFR and naturesis.
Glococorticoids, prostaglandins, cAMP

Question 24

Factors affecting the filtration coefficient

Answer 24

•Hormones can act on podocytes
-Causes change in glomerular filtration slits.
- If wider slits, high surface area, high GFR.

•Contraction of mesangeal cells (in endothelial cells of glomeruli)
-Less sa for filtration, GFR decreases.

Question 25

What are the factors affecting GFR(8)

Answer 25

•Glomerular capillary pressure
•Hydrostatic pressure in bowman’s capsule
•Colloid osmotic pressure
•Constriction of afferent arteriole
•Constriction of efferent arteriole
•Myogenic response
•Tubuloglomerular response
•Renal blood flow

Question 26

What are the non-excretory functions of the kidneys?

Answer 26

Production of renin
Erythropoietin production
Activation of vit D3
Production, metabolism and fracture of internal prostaglandins.

Question 27

Which cells secretes renin in the kidneys?

Answer 27

Juxtaglomerular cells from the juxtaglomerular apparatus

Question 28

What function does renin do?

Answer 28

It is responsible for the conversion of angiotensinogen into angiotensin 1.

Question 29

How is angiotensin 2 formed?

Answer 29

Angiotensin 1 is converted into angiotensin 2 by the enzyme Angiotensin converting enzyme found in the lungs.

Question 30

How is the formation of angiitensin 2 pathway regulated?

Answer 30

Angiotensin converting enzyme (ACE) inhibitors inhibits the enzyme responsible for the conversion of angiotensin1 to angiotensin 2.
Angiotensin receptor blockers inhibits the binding if angiotensin 2 to receptor, inhibiting all the cascade of events that would have been caused by Angiotensin 2.

Question 31

What are the functions of angiotensin 2?

Answer 31

-Causes vasoconstriction (high Bp)
-Stimulates the adrenal cortex to produce aldosterone ( Na reabsorption and K excretion)
-Stimulates adrenalin and noradrenaline release.

Question 32

What stimulates the release of renin?

Answer 32

-Low Bp
-high sympathetic activity
-Extracellular fluid volume
-Low Na and Cl delivery to macula densa cells.