BIO 252 Anatomy and Physiology Module 7 Study Guide
A&P 7 – The Urinary System
7.1 – Microanatomy of the Kidney: The Nephron
Introduction to the Urinary System
● The kidney is a regulator of blood plasma makeup
○ Removal of wastes
○ Regulate pH
○ Regulate BP
○ Maintain solute concentration
○ Control over RBC production → produces EPO to stimulate RBC production
○ Activates vitamin D (converts calcidiol → calcitriol)
Nephron
● Functional unit of the kidney
● Kidneys filter ~180 L of plasma per day; <1% becomes urine
● Each kidney contains ~1 million nephrons
● 2 types
○ Juxtamedullary
■ Long loops into medulla
■ Concentrate urine
○ Cortical
■ Loops stay mostly in cortex
■ Solute reabsorption
Nephron Structure
, 1. Renal Corpuscle
○ Includes glomerulus (fenestrated capillaries) + Bowman’s capsule ○ Filtration membrane
has 3 layers:
■ Fenestrated endothelium– allows small solutes through
■ Basement membrane– negatively charged; blocks proteins
■ Podocytes– form filtration slits; prevent large molecules from passing
2. Renal Tubule
○ Proximal Convoluted Tubule (PCT)
■ Simple cuboidal cells with microvilli (brush border)
■ Reabsorbs ~65% of filtrate (Na+, glucose, amino acids, bicarbonate)
■ Secretes drugs, H+, NH4+
○ Loop of Henle (Nephron Loop)
■ Descending limb– permeable to water
■ Ascending limb– pumps out Na+, K+, Cl-; impermeable to water
○ Distal Convoluted Tubule (DCT)
■ Hormone-regulated reabsorption of water, Na+, Ca2+
■ Fewer microvilli than PCT
3. Collecting System
○ Not technically part of the nephron
○ Contains principal cells and intercalated cells
○ Responds to ADH by inserting aquaporin-2 channels to reabsorb water
○ Collects filtrate → precapillary duct → calyces → renal pelvis → ureter
Nephron Functions ●
Primary functions:
○ Balance plasma set points ○
Excrete potential toxins in
urine
● These primary functions are accomplished by:
○ Filtration
○ Reabsorption
○ Secretion
● Secondary functions of the nephron:
○ Blood pressure control
■ Production of renin
○ RBC production
■ Via EPO
○ Calcium absorption
■ Conversion of calcidiol into calcitriol
Nephron– Filtration
● Glomerulus filters blood
● Allows water, small solutes to enter Bowman’s capsule
A&P 7 – The Urinary System
7.1 – Microanatomy of the Kidney: The Nephron
Introduction to the Urinary System
● The kidney is a regulator of blood plasma makeup
○ Removal of wastes
○ Regulate pH
○ Regulate BP
○ Maintain solute concentration
○ Control over RBC production → produces EPO to stimulate RBC production
○ Activates vitamin D (converts calcidiol → calcitriol)
Nephron
● Functional unit of the kidney
● Kidneys filter ~180 L of plasma per day; <1% becomes urine
● Each kidney contains ~1 million nephrons
● 2 types
○ Juxtamedullary
■ Long loops into medulla
■ Concentrate urine
○ Cortical
■ Loops stay mostly in cortex
■ Solute reabsorption
Nephron Structure
, 1. Renal Corpuscle
○ Includes glomerulus (fenestrated capillaries) + Bowman’s capsule ○ Filtration membrane
has 3 layers:
■ Fenestrated endothelium– allows small solutes through
■ Basement membrane– negatively charged; blocks proteins
■ Podocytes– form filtration slits; prevent large molecules from passing
2. Renal Tubule
○ Proximal Convoluted Tubule (PCT)
■ Simple cuboidal cells with microvilli (brush border)
■ Reabsorbs ~65% of filtrate (Na+, glucose, amino acids, bicarbonate)
■ Secretes drugs, H+, NH4+
○ Loop of Henle (Nephron Loop)
■ Descending limb– permeable to water
■ Ascending limb– pumps out Na+, K+, Cl-; impermeable to water
○ Distal Convoluted Tubule (DCT)
■ Hormone-regulated reabsorption of water, Na+, Ca2+
■ Fewer microvilli than PCT
3. Collecting System
○ Not technically part of the nephron
○ Contains principal cells and intercalated cells
○ Responds to ADH by inserting aquaporin-2 channels to reabsorb water
○ Collects filtrate → precapillary duct → calyces → renal pelvis → ureter
Nephron Functions ●
Primary functions:
○ Balance plasma set points ○
Excrete potential toxins in
urine
● These primary functions are accomplished by:
○ Filtration
○ Reabsorption
○ Secretion
● Secondary functions of the nephron:
○ Blood pressure control
■ Production of renin
○ RBC production
■ Via EPO
○ Calcium absorption
■ Conversion of calcidiol into calcitriol
Nephron– Filtration
● Glomerulus filters blood
● Allows water, small solutes to enter Bowman’s capsule
