Talk:Renal System Histology

Practical Overview

• Kidneys, ureters, urinar bladder, urethra

Kidneys

• elimination of foreign substances
• regulation of the amount of water in the body
• control of the concentration of most compounds in the extracellular fluid

filtration - glomeruli of the kidney

selective - resorption and excretion - tubular system of the kidney

Anatomy

• kidney bean shaped
• rich blood supply

Capsule outer layer - dense CT (fibroblasts and collagen inner layer - myofibroblasts

Cortex outer renal corpuscles medullary rays only straight tubules + straight collecting tubules 400-500 project medulla to cortex between medullary rays - convoluted tubules of nephrons

Medulla medullary pyramids (together with associated cortical region = renal lobe) base at cortioco-medullary border apex at renal papilla (surrounded by minor calyx) minor calyces converge to form major calyces then renal pelvis

Blood Supply

• renal artery
• interlobar arteries (across medulla thru renal columns)
• arcuate arteries (cortico-medullary junction)
• interlobular arteries
• afferent glomerular arterioles
• glomerular capillary network
• efferent glomerular arterioles

Vasa Recta

• descending arterioles (arteriole rectae) + ascending venules (venulae rectae)

Glomerulus

• glomerulus - round (~0.2 mm in diameter) blind beginning of the nephron
• vascular pole - invaginated by a tuft of capillaries
• urinary pole - substances leave the capillaries enter the renal tubule
• Bowman's capsule - anatomical glomerulus is enclosed by two layers of epithelium.
  • outer or parietal layer of Bowman's capsule form a simple squamous epithelium.
  • inner layer, podocytes in the visceral layer, are extremely complex in shape.
• Mesangial cells in the glomerulus form the connective tissue that gives structural support to podocytes and vessels (Podocytes, mesangial cells, glomerular capillaries)
• Juxtaglomerular cells - smooth muscle cells afferent glomerular arteriole (epithelial-like cells)
• Macular Densa
  • distal convoluted tubule near vascular pole (narrower and taller than rest of DCT)

Tubules

Proximal Convoluted Tubules

• brush border
• star-shaped
• larger outside diameter

Distal Convoluted Tubules

• clean lumen surface
• apical nuclei

Collecting Tubules

• larger lumen than DCT (about size of PCT)
• cuboidal cells and smaller than DCT

Renal Pyramids

• medullary straight tubules, ducts and vasa recta
• apical renal papilla - simple cuboidal/columnar epithelia
• calyx - lined by transitional epithelia

Note the urinary system transitional epithelium is also known as urothelium.

Ureters

• epithelium - transitional epithelia
• lamina propria - mainly of dense connective tissue, with many bundles of coarse collagenous fibres
• muscularis - consists of an inner longitudinal and outer circular layer of smooth muscle cells
  • In lower parts of the ureter and the bladder an additional outer longitudinal layer of muscles is added to the first two.

Bladder

• epithelium - transitional epithelia
  • apical plaques - thickened domain allows great changes in surface area.
• lamina propria - mainly of dense connective tissue, with many bundles of coarse collagenous fibres
• muscularis - consists of an inner longitudinal and outer circular layer of smooth muscle cells
  • In lower parts of the ureter and the bladder an additional outer longitudinal layer of muscles is added to the first two.

Urethra

• penile urethra within corpus spongisum
• pseudostratified columnar epithelia
• distal end - stratified squamous
• continuous with outer skin