Gross Anatomy of the Nephrons

What are the main functions of the nephrons

• filtration, selective reabsorption, secretion, urine formation

What are the types of nephrons

• cortical

• juxtamedullary

What is the FUNCTION of the cortical nephron?

• filtration and reabsorption

Describe the cortical nephron

• 85% of all nephrons

• located in renal cortex

• SHORT LOOPS OF HENLE

• surrounded by perpitubular capillaries

Describe the Juxtamedullary Nephrons

• 15% of all nephrons 

• situated near corticomedullary junction 

• LONG LOOPS OF HENLE

• associated with vasa recta network

What is the function of the Juxtamedullary Nephrons

• establishing the osmotic gradient

• necessary for urine concentration 

Renal Corpuscle function

• Initial filtering component of the nephron 

What are features of the Renal Corpuscle

• glomerulus

• Bowman’s Capsule

What is the Glomerulus

• tuft of fenestrated capillaries 

• supplied by afferent arteriole

• drained by efferent arteriole 

What is the function of the glomerulus

• specialized for ultrafiltration 

• driven by hydrostatic pressure 

What is the Bowmans Capsule

• double layer cup like structure that surrounds the glomerulus 

• has 3 layers

Parietal Layer of the Bowmans Capsule

• simple squamous epithelium

• forms capsule wall

Visceral Layer of Bowmans Capsule

• podocytes that cover glomerular capilaries

Capsular Space

• between layers

• collects the filtrate 

What are the Tubular Components of the Nephron

• proximal convoluted tubule

• loop of henle

• distal convoluted tubule

• collecting duct

Proximal Convoluted Tubule

• located in the cortex

• lined by cuboidal epithelium 

• has dense microvilli 

Loop of Henle

• U shaped segment that dips into the medulla 

Loop of Henle- Descending Limb

• permeable to water

• not permeable to solutes 

• concentrates tubular fluid 

Loop of Henle- Ascending Limb

• impermeable to water 

• actively transports Na+, K+, Cl-

• dilutes tubular fluid 

Distal Convoluted Tubule

• located in cortex

• shorter and lacks brush boarder

Distal Convoluted Tubule Function

• fine tunes electrolyte balance 

• regulated by hormones 

What hormones regulate the distal convoluted tubule?

• Aldosterone 

• parathyroid hormone 

How does Aldosterone affect the distal convoluted tubule

• increases Na+ reabsorption and K+ secretion 

How does Parathyroid hormone affect the distal convoluted tubule

• increases Ca2+ reabsorption 

Collecting Duct

• final site of urine concentration 

• receives filtrate from DCTs

• under hormonal control

What hormones regulate the collecting duct 

• ADH

• Aldosterone

ADH

• increases water reabsorption 

Aldosterone

• enhances Na+ reabsorption and K + secretion 

What are the capillary networks in the nephrons

• peritubular capillaries

• vasa recta 

Peritubular Capillaries 

• derived from efferent arterioles of cortical nephrons

• surround the PCT and DCT

Vasa Recta

• specialized straight capillaries arising from efferent arterioles of juxtamedullary nephrons

Renal Corpuscle Histology 

• lined by podocytes and simple squamous epithelium 

Proximal Convoluted Tubule Histology 

• cuboidal epithelium 

• dense brush boarder 

Loop of Henle Thick Ascending Limb Histology

• cuboidal cells

• no brush border

Loop of Henle thin descending and ascending limbs

• simple squamous epithelium 

What are glomerular capillaries surrounded by?

• mesangial cells

Distal Convoluted Tubule Histology

• cuboidal epithelium

• NO brush border

• macula densa cells

Collecting Duct Histology 

• cuboidal then columnar epithelium 

• 2 main cell types

  • principal cells

  • intercalated cells 

What is the function of Intercalated cells

• regulate acid base balance

What is the function of principal cells in the collecting duct 

• regulate water and sodium 

What is the Glomerular filtration barrier

• allows passage of water and small solutes 

• resiricts proteins and cells

What are the layers of the glomerular filtration barrier 

• fenestrated epithelium of glomerular capillaries

• Glomerular Basement membrane 

• podocyte visceral epithelium 

Fenestrated epithelium of glomerular capillaries

• restricts blood cells

• allows plasma solutes

Glomerular Basement membrane 

• rich in negatively charged glycoproteins

• restricts passageway of large proteins

Podocyte Visceral epithelium 

• slit bridges by a slit diaphragm are crucial for size/ charge selective filtration