Urinary Tract Anatomy and Histology

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22 Questions

What is the main function of the proximal convoluted tubules in the nephron?

Reabsorption of glucose and amino acids

What is the characteristic of the cells lining the proximal convoluted tubules?

Triangular with non-clear boundaries

What is the primary function of the distal convoluted tubules?

Reabsorption of water and sodium

What is the structure that connects the proximal convoluted tubules and distal convoluted tubules?

Loop of Henle

What is the characteristic of the lumen in the proximal convoluted tubules?

Narrow lumen

What is the main difference between the proximal convoluted tubules and distal convoluted tubules?

Convolutions of the tubules

What is the function of the basal infoldings in the proximal convoluted tubules?

Increase surface area for reabsorption

What is the characteristic of the cells lining the distal convoluted tubules?

Cubical with clear boundaries

What is the function of the longitudinal folds in the mucosa of the urinary tract?

To allow distension during the passage of small stones

What type of epithelium lines the mucosa of the urinary bladder?

Transitional epithelium

What is the name of the muscle layer in the urinary bladder wall?

Detrusor muscle

What happens to the umbrella cells in the mucosa of the urinary bladder when it is full?

They become flat

What is the outermost layer of the urinary bladder wall?

Adventitia

What is the function of the internal sphincter in the urinary bladder?

To prevent the backflow of urine

What type of epithelium lines the thin descending part of the nephron?

Simple squamous

Which part of the nephron is responsible for the concentration and formation of hypertonic urine?

Thick ascending part

What is the function of the juxtaglomerular cells?

Secrete renin

How many nephrons does each collecting tubule receive?

5-10

What type of epithelium lines the small collecting tubules?

Simple cuboidal

What is the juxtaglomerular apparatus composed of?

Juxtaglomerular cells, macula densa, and extraglomerular mesangial cells

What is the function of the macula densa?

Osmoreceptors

What type of epithelium lines the ureter?

Transitional

Study Notes

Urinary System

  • The urinary system consists of uriniferous tubules, which include nephrons and collecting tubules.

Nephrons

  • Nephrons are composed of proximal convoluted tubules and distal convoluted tubules.

Proximal Convoluted Tubules

  • Length: 15 mm, more convoluted
  • Diameter: 60 µm
  • Lined with 3-4 cells with non-clear boundaries, deeply acidophilic and granular, with basal striations and apical brush border
  • Numerous apical microvilli and pits and vesicles containing reabsorbed proteins
  • Basal infoldings with numerous mitochondria
  • Function: reabsorption of H2O and Na, active absorption of glucose and amino acids

Distal Convoluted Tubules

  • Length: 5 mm, less convoluted
  • Diameter: 40 µm
  • Lined with 5-8 cells with clear boundaries, less acidophilic and less granular, with central nucleus
  • Few microvilli and mitochondria
  • Function: reabsorption of H2O (ADH), reabsorption of Na (aldosterone), and secretion of ammonia

Renal Tubules

  • The renal tubules include the loop of Henle, which connects the proximal convoluted tubules and distal convoluted tubules.

Loop of Henle

  • U-shaped, formed of thick descending, thin descending, thin ascending, and thick ascending parts
  • Function: concentration and formation of hypertonic urine

Collecting Tubules

  • Each collecting tubule receives 5-10 nephrons
  • Small collecting tubules are lined with simple cuboidal epithelium
  • Large collecting ducts (Ducts of Bellini) are lined with simple columnar epithelium

Juxtaglomerular Apparatus

  • Definition: complex structure at the vascular pole of some renal corpuscles
  • Composed of juxtaglomerular cells, macula densa, and extraglomerular mesangial cells (Lacis cells)
  • Function: secretion of renin, osmoreception, and support

Urinary Passages

  • Ureter: wall formed of mucosa, musculosa, and adventitia
  • Mucosa: transitional epithelium and C.T corium, forms longitudinal folds to allow distension
  • Musculosa: upper 2/3 has 2 layers, lower 1/3 has 3 layers
  • Adventitia: loose CT rich in BV, nerves, and lymph vessels

Urinary Bladder

  • Wall formed of mucosa, musculosa, and adventitia
  • Mucosa: transitional epithelium (urothelium) on C.T corium, with umbrella cells
  • Musculosa: detrusor muscle, formed of 3 poorly delineated layers, thickened at the bladder neck to form the internal sphincter
  • Adventitia: loose C.T, superior part covered by peritoneum

This quiz covers the anatomy of the urinary tract, including the renal cortex and medulla, and the histological structure of nephrons and collecting tubules. It also explores the ultrastructure of podocytes and their role in forming the renal blood barrier.

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