Sistema Urinário

Functions
• Contributes to the maintenance of the homeostasis (regulatory function)
• Balance of water and electrolytes

Constitution

Kidney
• Covered by a capsule of dense connective tissue
• The morphofunctional unit of the kidneys is the nephron
• Presents a cortical and medullar zone

Cortical
• Corpuscle of Malpighi
• Proximal and distal convoluted tubule
• Medullary arrays and vessels

Medullar
• Loop of Henle
• Collecting Tubules: Reunite forming larger and larger tubes that direct themselves towards the renal papilla
- Tubes with a smaller diameter have simple cuboidal epithelium
- Larger tubes have columnar cells

Néfron

I- Renal Corpuscle (or of Malpighi)
• Bowman’s Capsule
• Has two sheets:
- Parietal: Simple squamuous epithelium
- Visceral: Podocytes with projections over the membrane of the capillaries (Modified epithelium)

II- Malpighi’s Glomerulus
• Formed by fenestrated capillaries
• Derived from the afferent arteriole
• Coil themselves and reunite to form the efferent arteriole
• We find:
- Over the membrane of the capillaries, the podocytes
- Between the basal membrane and the capillaries, the mesangial cells

III- Proximal Convoluted Tubule
• Walls formed by simple cuboidal epithelium
• Cells with acidophilic cytoplasm
• In the apical portion, they possess numerous microvilli that form the brush border
• In the basal portion it presents cytoplasmic expansions

IV- Loop of Henle
• Thin descending limb: Simple squamous epithelium
• Thick ascending limb: Simple cuboidal epithelium

V- Distal convoluted tubule
• Last segment of the nephron
• Wall composed of simple cuboidal epithelium
• Small and scattered microvilli
• Pale acidophil cytoplasm
• Does not present a brush border in its apical portion