Renal structure and function Flashcards
How many nephrons are in the human kidney?
1.5 million
What does the nephron control? (3)
Glomerular filtration
Tubular reabsorption and secretion
Urine formation
What are the 2 components in the kidney?
Vascular and tubular
What are the 3 levels of the kidney?
Cortex
Outer medulla
Inner medulla
What are 3 vital parts of the nephron pathway?
Glomerulus
Macula densa
Collecting duct
What is the order of structures in a nephron as the blood flows? (7)
- Ultrafiltration in the Bowman’s capsule
- Proximal convoluted tubule
- Thin descending limb (Loop of Henle)
- Thin ascending limb (Loop of Henle)
- Thick ascending limb
- Distal convoluted tubule
- Collecting duct (descending)
What are the names of the 2 arteries that enter the kidney and what lies between them?
Efferent (takes away)
Granular cells, macula densa cells (ascending loop of Henle limb)
Afferent
What do the 2 arteries feed into?
Glomerulus within the Bowman’s capsule
What tube leads out of the Bowman’s capsule?
Proximal tubule
What blood does the afferent arteriole deliver?
O2 rich blood to be filtered
What is glomerular filtration rate dependent upon? (5)
Capillary permeability Hydrostatic pressure in capillaries Hydrostatic pressure in tubules Osmotic pressure of plasma in glomerular capillaries Osmotic pressure of tubular filtrate
What is the order, hydrostatic movement and osmotic movement during glomerular filtration? (4)
- Hydrostatic pressure: Bowman’s capsule, movement IN
- Hydrostatic pressure: capillary, movement OUT
- Colloid osmotic pressure: Bowman’s capsule, movement OUT
- Colloid osmotic pressure: capillary, movement IN
What are the effects of afferent constriction? (4)
Increased resistance
Reduced capillary pressure
GFR decreases
Bottleneck effect
What are the effects off efferent constriction? (3)
Increased pressure in capillary
Pressure rises
GFR increases
What are the key factors of the proximal convoluted tubule? (2)
- Filtrate (isosmotic - same no. of solutes as capillary side)
- 70% of filtrate is reabsorbed back into the body
What is the rate of GFR per day? (2)
180L per day
3L plasma in the body - very efficient
What are the key functions of the PCT? (4)
- Fluid entering the PCT has similar composition to plasma
- Active reabsorption of Na+ (water follows sodium)
- Reabsorption of glucose and bicarbonate
- Some ions and molecules are secreted into the tubular filtrate
What happens in the loop of Henle? (8)
- Filtrate is isosmotic from PCT
- Water moves out as you go down
- NO active ion transport
- Filtrate becomes hyper-osmotic
- Filtrate rises up the ascending limb
- Active reabsorption of Na+
- Impermeable to water
- filtrate becomes hypo-osmotic
When does the loop of Henle move from the cortex into the medulla?
Cortex - 300mosm/kg
Medulla - 600-1200mmosm/kg
What is the countercurrent multiplier?
Facilitates the reabsorption of water from the collecting ducts toward the hyper-osmotic interstitium
What is the role of the distal convoluted tubule? (3)
- Active reabsorption of Na+
- Secretion of K+ and H+ ions
- Stimulated by the actions of aldosterone
What is the role of the collecting duct?
> Urea is free to move out of collecting duct in the presence of ADH
ADH opens aquaporins, thereby increasing reabsorption of water and concentrating urine
What specific ion do we need from our diet as we struggle to reabsorb it?
Potassium
