The nephron flashcards

The nephron

  1. describe the anatomy of the nephron

  2. describe the specialisation of each part of the nephron

TWO TYPES OF NEPHRON- both types produce urine

(1) cortical nephrons

short loop of henle

80-85% of nephrons

(2) juxtamedullary nephrons

long loop of henle extends into medulla

responsible for the medullary osmotic gradient

THE RENAL CORPUSCLE

  • blood enter through the renal artery flows via afferent arterioles into compact clusters of capillaries (glomerulus)

  • approx. 20% of plasma flowing through each glomerulus leaks out into the bowman’s space

  • remainder of blood exits via efferent arterioles

  • BOWMANS CAPSULE

~ invaginated sphere that forms two layer

~ parietal layer (outer)

~ visceral layer (inner)

~ its role is to produce filtrate

  • GLOMERULAR CAPILLARY

~ fenestrated endothelium that forms fenestrae (pores) of 70-100nm

~ glomerular basement membrane - mesh of extracellular proteins

~ visceral epithelial cells (podocytes) form the filtration slit diaphragm

  • PROXIMAL CONVOLUTED TUBULE

~ cuboidal epithelial cells

~ covered with microvilli

~ brush border that allow reabsorption of filrate components (70% water and sodium, 100% glucose)

~ rich in mitochondria

~ tight junctions allow paracellular transport

  • LOOP OF HENLE

~ descending limb has a similar epithelium like the PCT

~ both thin ascending and descending loop of henle are lined by simple squamous epithelium

~ thick ascending limb is lined by a cuboidal epithelium similar to DCT

  • DISTAL CONVOLUTED TUBULE

~ simple cuboidal epithelium

~ no brush border

~ high proportion of mitochondria (fewer than PCT)

~ tight junctions

  • COLLECTING DUCT

~ simple cuboidal epithelium

~ collecting ducts merge and become larger as they descend through the medulla

THE JUXTAGLOMERULAR APPARATUS

  • regulates blood pressure and the filtration rate of the glomerulus

(1) macula densa

~ densely packed group of modified epithelial cells in the DCT

~ detect and regulate sodium ions concentration

(2) juxtaglomerular cell (granular cells)

~ derived from the smooth muscle cells of the afferent arteriole

~ JG cells secrete renin which regulate blood pressure in the arteriole via the renin-angiotenisn-aldosterone system

SUMMARY

  • the nephron is divided into renal corpuscle and renal tubules

  • the renal tubules can further divide into specialised regions that have specialised epithelia