Renal Physiology for Dummies
Step by Step
Step 1: Filtration
- In glomerulus within renal corpuscle
- Blood enters through afferent arteriole
- Filtered through 3 layers
o Leaky capillary wall (epithelium)
o Basement membrane
o Podocytes with “foot slits”
- Small things get pushed into Bowman’s capsule
o Water
o Ions
o Glucose
- Large things stay in the blood
o Proteins
o Cells
- Factors affecting filtration
o Pressure in glomerular capillaries: increased pressure = increased filtration
o Protein levels: more albumin = decreased filtration
o Constriction/dilation of arterioles
§ Constricted afferent arterioles = decreased GFR
§ Constricted efferent arterioles = increased GFR
Step 2: Reabsorption
- Mostly in proximal tubule
- Body reabsorbs what it needs
o Glucose
o Salt
o Water
- Diffusion and active transport
- Na+ is main driver à pumped out and water follows it
- Proximal tubule: reabsorbs ~65% of water, Na+, glucose, and amino acids
- Loop of henle
, o Descending: water ONLY
o Ascending: Na+ and Cl- (no water)
- Distal tubule and collecting duct: fine tuning
- Factors affecting reabsorption
o Transporters (transport max: diabetes)
o Hormones: aldosterone (saves Na+) and ADH (saves water by adding aquaporins)
Step 3: Secretion
- In proximal tubule and cortical collecting duct
- Stuff that didn’t get filtered gets actively secreted into tubule from blood
o Drugs
o H+
o K+
- Factors affecting secretion
o Body’s needs
o Aldosterone
Step 4: Excretion
- After collecting ducts
- Leftover fluid (urine) drains
- Renal pelvis à ureter à bladder à urethra
Concurrent System
- How kidney concentrated pee
- In loop of henle
o Juxtamedullary nephrons
o Ascending limb pumps out NaCl (water stays)
o Descending limb lets water out (NaCl stays)
o Creates salty medulla that pulls water out later in collecting duct
Step by Step
Step 1: Filtration
- In glomerulus within renal corpuscle
- Blood enters through afferent arteriole
- Filtered through 3 layers
o Leaky capillary wall (epithelium)
o Basement membrane
o Podocytes with “foot slits”
- Small things get pushed into Bowman’s capsule
o Water
o Ions
o Glucose
- Large things stay in the blood
o Proteins
o Cells
- Factors affecting filtration
o Pressure in glomerular capillaries: increased pressure = increased filtration
o Protein levels: more albumin = decreased filtration
o Constriction/dilation of arterioles
§ Constricted afferent arterioles = decreased GFR
§ Constricted efferent arterioles = increased GFR
Step 2: Reabsorption
- Mostly in proximal tubule
- Body reabsorbs what it needs
o Glucose
o Salt
o Water
- Diffusion and active transport
- Na+ is main driver à pumped out and water follows it
- Proximal tubule: reabsorbs ~65% of water, Na+, glucose, and amino acids
- Loop of henle
, o Descending: water ONLY
o Ascending: Na+ and Cl- (no water)
- Distal tubule and collecting duct: fine tuning
- Factors affecting reabsorption
o Transporters (transport max: diabetes)
o Hormones: aldosterone (saves Na+) and ADH (saves water by adding aquaporins)
Step 3: Secretion
- In proximal tubule and cortical collecting duct
- Stuff that didn’t get filtered gets actively secreted into tubule from blood
o Drugs
o H+
o K+
- Factors affecting secretion
o Body’s needs
o Aldosterone
Step 4: Excretion
- After collecting ducts
- Leftover fluid (urine) drains
- Renal pelvis à ureter à bladder à urethra
Concurrent System
- How kidney concentrated pee
- In loop of henle
o Juxtamedullary nephrons
o Ascending limb pumps out NaCl (water stays)
o Descending limb lets water out (NaCl stays)
o Creates salty medulla that pulls water out later in collecting duct
