Functions of urinary system:
🔸Formation, storage and excretion of urine
🔸Removing of waste product from blood.
🔸Blood volume regulation
🔸Endocrine function
🔸Renin secretion
🔸Erythropoetin secretion
🔸Vit D synthesis
Kidney
Kidney proper (parenchyma)
1. Cortex
Cortical arch
Renal column
Medulla = Renal pyramid
Renal sinus
Lobe of kidney:
One pyramid + cortical arch + half of renal column from each side.
Renal cortex consists of
Renal corpuscle
PCT
DCT
Collecting tubules
Collecting ducts
Extensive vascular supply
Filtration membrane
Endothelial cells (fenestration)-70-90nm
Basement membrane (type IV collagen)
Pedicles of podocytes (filtration slits)- 20-30nm
🔸Nephrotic Syndrome: abnormalities in the structure of glomerular basement membrane increasing its permeability.
It is diagnosed by urine test and blood test
🔸Protenuria (≥3.5 g/day)
🔸Hypoalbuminea (≤30 g/dl)
🔸Oedema
🔸Dyslipidemia (increased LDL)
PCT
Location: cortex
Simple cuboidal epithelium with brush border (formed by microvilli).
Basal striation (by mitochondria)
Irregular lumen
Loop of Henle
Location: medulla (forms medullary rays)
Simple squamous epithelium (thin part)
Simple cuboidal epithelium (thick part)
Medullary rays
Collecting duct
Loop of Henle
DCT
Location: cortex
Simple cuboidal epithelium with very few microvilli.
Size of cell is smaller than that of PCT
Perfectly round lumen.
PTH dependent Calcium reabsorption occurs in DCT
Collecting duct
Lined by
Principle cells (pale)
(Aquaporin-2)
2. Intercalated cells (dark)
Acidification of urine
Ureter, urinary bladder and urethra.
Except for urethra, general arrangement is –
Mucosal epithelium (Transitional epithelium)
Lamina propria
Muscle layer (inner longitudinal, outer circular)
(3rd layer of longitudinal muscle is found in distal ureter and bladder.)
d. Adventitia or Serosa layer
Urethra
Prostatic – transitional epithelium
Membranous- pseudostratified columnar
Spongy-pseudostratified + stratified squamous
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