Week 7

Question 1

Key functions of kidney

Answer 1

Removal of waste products
Regulation of fluid and electrolyte levels
Regulation of pH
Maintaining blood pressure
Maintaining blood osmolarity
Production of hormones and renin
Gluconeogenesis

Question 2

Kidney structure

Answer 2

Around 10-12cm long, 5-7cm wide and 3cm thick
Dent on medial side known as hilum
Renal cortex: outer region of kidney and contains nephrons
Renal medulla: inner region containing renal pyramids separated by renal columns

Question 3

How many nephrons in each kidney?

Answer 3

1-1.25 million

Question 4

Basic Nephron Structure

Answer 4

Blood flows into the renal corpuscle from the afferent arteriole, plasma is filtered, the filtrate flows into the proximal tubule, loop of henle, distal tubule and collecting duct

Question 5

Cortical nephrons

Answer 5

80-85% of all nephrons
Renal corpuscle located in cortex, with renal papilla going through the pyramid

Question 6

Juxtamedullary nephrons

Answer 6

Renal corpuscle located nearer medulla
Flow: Bowman’s capsule, descending limb,ascending limb (thin then thick), distal convoluted.

Question 7

Glomerulus

Answer 7

Fenestrated capillaries
Receive blood from afferent arteriole

Question 8

Bowman’s capsule

Answer 8

Inner visceral layer consists of specialised cells called podocytes
Pedicels extend from podocytes and form filtration slits around the capillaries
Outer parietal layer constructed from squamous epithelial cells

Question 9

Renal tubule

Answer 9

Surrounded by peritubular capillaries

Question 10

Proximal tubule

Answer 10

Greatest reabsorption due to simple cuboidal epithelium and microvilli
100% of glucose and amino acids reabsorbed

Question 11

Nephrons loop - cell types

Answer 11

Descending - simple squamous
Thin ascending - Simple squamous
Thick ascending - cuboidal or low columnar
Reabsorption 20% of water in descending limb, 25% sodium and chloride thick ascending

Question 12

Distal tubule

Answer 12

Main role is regulating fluid composition

Question 13

The ureters

Answer 13

3 layers:
Inner mucosa: transitional epithelium
Muscularis: Circular and longitudinal muscle
Adventitia: loose connective tissue

Question 14

Glomerular filtration

Answer 14

Afferent arterioles feed blood into the renal corpuscle. It then goes through the filtration membrane

Question 15

What is the filtration membrane made up of?

Answer 15

Fenestrated capillaries
Podocytes

Question 16

Factors that drive net filtration

Answer 16

Glomerular blood hydrostatic pressure
Capsular hydrostatic pressure
Blood colloid osmotic pressure

Question 17

Glomerular blood hydrostatic pressure

Answer 17

Forces fluid out of the glomerular capillaries

Question 18

Capsular hydrostatic pressure

Answer 18

Hydrostatic pressure within the glomerular capsule
Resists fluid exiting the glomerular capillaries

Question 19

Blood colloid osmotic pressure

Answer 19

Osmotic pressure of blood solutes
Opposes fluid loss into the capsular space

Question 20

Glomerular filtration rate

Answer 20

The amount of filtrate produced in both kidneys
It is maintained around 105-125ml/min

Question 21

Renal autoregulation

Answer 21

Myogenic mechanism: uses changes to the vascular tone of either the afferent or efferent arteriole to maintain the desired blood flow
Tubuloglomerular feedback mechanism uses alterations to the vasodilator, nitric oxide

Question 22

Tubuloglomerular feedback mechanism

Answer 22

Macula densa cells detect an increase in tubular fluid ion and water flow in the kidney tubules
They act to inhibit the release of nitric oxide from the juxtaglomerular apparatus. Results in vasoconstriction of the afferent arteriole

Question 23

Neural regulation

Answer 23

Sympathetic division of ANS acts on Alpha 1 receptors in the smooth muscle of afferent and efferent arterioles
Norepinephrine induces vasoconstriction, which reduces GFR

Question 24

Hormonal regulation of GFR

Answer 24

Atrial natriuretic peptide- increases the glomerular capillary surface area by relaxing glomerular mesangial cells (increasing GFR)
Angiotensin II - powerful vasoconstrictor (decrease GFR)

Question 25

Glomerular diseases

Answer 25

Can cause oedema due to loss of albumin through filtration slits- reducing blood volume

Question 26

Tubular reabsorption

Answer 26

99% will be reabsorbed through the renal tubules and into peritubular capillaries and vasa recta.
Once reabsorbed into peritubular capillaries, blood flows into interlobular veins and then through the renal vein

Question 27

Paracellular reabsorption

Answer 27

Paracellular reabsorption is a process that occurs primarily in the kidneys, particularly in the renal tubules, where substances move between adjacent cells (rather than through them) to reabsorb water, ions, and other solutes back into the bloodstream. Occurs through tight junctions and occurs in the PCT and loop of henle

Question 28

Transcellular reabsoprtion

Answer 28

Involves substances passing through the cell membrane via specific transport proteins. This process can be active (requiring energy) or passive (driven by concentration gradients).

Question 29

Reabsorption in PT

Answer 29

65% water
100% of glucose and amino acids
65% of NA and K
50% cl
85% HCO3
50% urea

Question 30

Nephrons loop reabsorption

Answer 30

15% water
20-30% Na and K
35% of Cl
15% HCO3

Question 31

Distal tubule (early)

Answer 31

10% water
5% Na
5% cl

Question 32

Late distal tubule

Answer 32

Principle cells: Na and K
Intercalated cells: secretes H, Secretes or reabsorbs HCO3

Question 33

Where does most secretion take place and what part fine-tunes blood solute concentration

Answer 33

Proximal tubule
Distal tubule and collecting duct