Histological Structure of Renal System - Lecture 4

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Which of the following cells are specialized myoepithelial cells with a secretory phenotype?

Juxtaglomerular (JG) cells

Which of the following statements about the macula densa cells is correct?

They are tall columnar cells with deeply stained, closely packed nuclei.

Where are the extraglomerular mesangial cells located?

Between the macula densa, glomerulus, and afferent arteriole

Which of the following is NOT a function of the juxtaglomerular apparatus (JGA)?

Regulating tubular reabsorption of glucose

Which component of the nephron is NOT listed in the given text?

Ducts of Bellini

Which cells are responsible for the release of renin, the initial enzyme in the renin-angiotensin-aldosterone system?

Juxtaglomerular (JG) cells

Which structure serves as a local baroreceptor in the afferent arteriole, possibly involved in the release of renin?

Juxtaglomerular (JG) cells

Which cells are responsible for monitoring the luminal concentrations of Na+ and Cl- in the nephron?

Macula densa cells

Which of the following statements about the extraglomerular mesangial cells is correct?

They occupy the area between the macula densa, glomerulus, and afferent arteriole.

Which of the following structures is NOT involved in the autoregulation of glomerular filtration rate (GFR)?

Podocytes

Study Notes

Renal System

  • The renal tubular system is divided into several functional units: proximal convoluted tubule (PCT), loop of Henle, distal convoluted tubule (DCT), collecting tubules, and collecting ducts.

Proximal Convoluted Tubules (PCT)

  • Start at the tubular pole of the renal corpuscle where the simple squamous epithelium of the capsule's parietal layer is continuous with the simple cuboidal epithelium of PCT.
  • Luminal border consists of countless microvilli, with many pinocytotic vesicles below, indicating active endocytosis and pinocytosis.
  • Interdigitations with neighboring cells are present laterally, and long invaginations of the basal cell membrane outline regions with mitochondria, supplying ATP locally for membrane proteins involved in active transport.
  • Functions: reabsorption and secretion, hydroxylation of vitamin D, and release to capillaries.

Distal Convoluted Tubules (DCT)

  • Simple cuboidal cells, smaller than PCT cells, with no brush border and more empty lumens.
  • Cytoplasm is less granular and less acidophilic, with less basal striations.
  • Nuclei are rounded and slightly apical, with more distinguishable cell borders.
  • Lumen is wider than PCT.

Loop of Henle

  • U-shaped structure with a thin descending limb and a thin ascending limb, both composed of simple squamous epithelia.
  • Thick descending part resembles PCT, while thick ascending part resembles DCT.
  • Thin segments have squamous cells with few organelles, indicating a primarily passive role in transport.

Collecting Tubules and Collecting Ducts

  • Collecting tubules lined by low cuboidal cells, merging to form collecting ducts of simple cuboidal epithelium.
  • Medullary collecting ducts are the final site of water reabsorption from the filtrate.

Juxtaglomerular Apparatus (JGA)

  • Formed by modifications in the afferent arteriole (juxtaglomerular granular cells) and the distal convoluted tubule (macula densa cells).
  • Functions: autoregulation of glomerular filtration rate (GFR) and controlling blood pressure via the renin-angiotensin-aldosterone system.

Learn about the histological structure of the proximal convoluted tubules, loop of Henle, collecting tubules, and collecting ducts in the renal system. Identify the type of lining epithelium and functions of each component.

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