W9 L1 - renal physiology

Question 1

function of the renal system and its components

Answer 1

• Filter blood and remove waste
• Make URINE
• Control red blood cell production
• Control blood pressure

Components:
1. Kidneys
2. Ureters (2)
3. Bladder
4. Urethra

Question 2

Kidney function

Answer 2

• Removal of waste products from blood
• Respond to hormones (ADH, PTH, aldosterone)
• Make hormones (Renin, vitamin D and erythropoietin)

Question 3

structures above the kidneys

Answer 3

adrenal glands

Question 4

Gross anatomy of Kidneys

Answer 4

Capsule – covers the whole kidney
Cortex – outer layer
Medulla – inner layer
Renal pelvis - drains to the ureter

Question 5

what are nephrons

Answer 5

Functional unit is a nephron of a nephron

Question 6

what’s histology

Answer 6

microscopic anatomy of biological tissues

Question 7

Functions of the renal capsule

Answer 7

Protection
Fibrous
Fat layer on top
Lowers the risk of trauma to the kidney (also ribs)

Question 8

passage of urine through kidney

Answer 8

renal pelvis to ureter to cladder

Question 9

which layers soes the nephron cross

Answer 9

Glomeruli and proximal tubule are in the cortex
Loop of Henle and collecting duct in the medulla

Question 10

Glomerulus

Answer 10

• Supplied by capillaries (high pressure)
• Contains a Bowmans capsule (hollow)
• Made of tubular epithelium
• Forces water, ions and small molecules into the Bowman capsule
• Molecular sieve: < 50kDa
• Approx 10% of renal blood plasma filtered (~120 mL/min)
• 1st stage of urine production
• Located in the cortex
• Contains all the glomeruli (plural)

Question 11

Proximal convoluted tubule (PCT)

Answer 11

• Columnar epithelium lining
• Microvilli
• High surface area
• Lots of mitochondria for energy
• Source of most re-absorption
  Passive and active reabsorption
  Approx. 60% of water reabsorption
  Na, K, Ca, phosphate
  Nutrients: glucose, amino acids
  Drugs (pharmacokinetics/ ADME)
• Site of tubular secretion
  H+ and NH+ (pH homeostasis)
  Waste products of metabolism
  Creatinine, indoxyl sulfate
  Drugs (pharmacokinetics/ ADME)
  Transporters (ABC & SLC)

Question 12

Biological mechanisms that occur in PCT

Answer 12

Passive permeability/diffusion across membrane
Transporters [SLC, ABC] (e.g., Na⁺/K⁺-ATPase)
Ion channels (e.g., K+)
Endocytosis (low molecular weight proteins; e.g. via megalin, cubulin

Question 13

Loop of Henle

Answer 13

• Medulla
• Creates an osmotic gradient
• Split into two sections
  Descending (water permeable) where reabsorption occurs and urea is secreted
  Ascending (water impermeable) limb where cells efflux Cl- and Na+ into blood for reabsorption of water

Question 14

Distal convoluted tubule (DCT)

Answer 14

• Cortex
• Hormone controlled
• Responds to parathyroid hormone (PTH)
  Re-absorbs calcium
• Responds to aldosterone
  Reabsorb Na+
  Secretes K+

Question 15

Collecting duct

Answer 15

• Medulla
• Concentrates urine
  reabsorbs water
  anti-diuretic hormone (ADH; vasopressin; AVP) can affect function by promoting water reabsorption
  ADH is inhibited by alcohol
• Medulla is salty (Na+ gradient)
  Water leaves by osmosis (passive)

Question 16

Renal physiological functions

Answer 16

• Removal of waste products from blood
  Without losing water and nutrients!
• Blood acid-base (pH) and osmolarity homeostasis
  Topic of separate lecture
• Respond to hormones (ADH, PTH, aldosterone)
• Make hormones (Renin, vitamin D and erythropoietin)

Question 17

Hormones produced by kidneys

Answer 17

Renin, Vitamin D-products, Erythropoietin and (prostaglandins)

Question 18

Renin

Answer 18

• Produced by the juxtaglomerular apparatus
• Released in response to low sodium
• Leads to formation of angiotensin II
  Acts on nephrons, Promote sodium retention (in blood)
  Potent vasoconstrictor, Regulation of blood pressure, Multiple organ involvement

Question 19

Erythropoietin

Answer 19

• Made by fibroblasts (interstitial space)
  In response to low oxygen concentrations (hypoxia) in blood
• Promotes red blood cell formation in bone marrow

Question 20

Vitamin D (steroid hormone)- products

Answer 20

• Metabolised in the kidney
• 1,25-dihydroxycholecalciferol
  Promotes Ca and K absorption from gut

Question 21

Renal drug Excretion

Answer 21

• Think of drugs as a waste/ toxic substance to be removed from body
• Same processes apply (Filtration/Reabsorption/Secretion)
• Lipophilic drugs typically are passively reabsorbed –> renal excretion is small

Question 22

diuretics

Answer 22

act on different sections of the nephron

Question 23

Ureters

Answer 23

• Tubes
  One from each kidney
• Transport urine
  from renal pelvis (kidney)
  to bladder
• Muscular tubes
  Peristalsis (urine bolus)
  Smooth muscle
  Lined with epithelium (transitional = stretch)

Question 24

Urinary bladder

Answer 24

• AKA bladder
• Receives urine via two ureters
• Hollow
• Smooth muscle
• Size depends on urine content