Macula Densa Quiz and Flashcards: Juxtaglomerular Apparatus

What is the main function of the connecting tubule in the nephron?

Which part of the nephron merges to form the papillary duct?

Which type of epithelium is characteristic of the collecting ducts?

What is the average diameter of the collecting ducts in the medulla?

What happens to the secretion of renin by JG cells when blood pressure returns to normal?

What is the role of the interstitial tissue in the kidney?

Which structure in the kidney forms an osmolarity gradient?

What is the point of contact between a nephron's distal tubule and the vascular pole of its glomerulus called?

How does decreased arterial pressure affect the release of renin?

In what region do the smooth muscle cells of the afferent arteriole convert from a contractile to a secretory morphology?

What is the function of angiotensin II in the body?

Which cells are adjacent to the macula densa, the afferent arteriole, and the efferent arteriole in the kidney?

Which area in the kidney has very high interstitial osmolarity?

How does aldosterone impact tubular reabsorption in the kidney?

What is the final site of water reabsorption from the filtrate in the kidney?

How does the specialized nature of interstitial tissue support kidney function?

Which type of cells are mainly composed of pale-staining principal cells with few organelles, sparse microvilli, and distinct cell boundaries in the collecting tubules and ducts?

What is the primary effect of renin on angiotensinogen?

The Interstitium and Epithelium

The interstitium has a slightly fibrous nature and contains sparse myofibroblast-like cells in a matrix rich in hydrophilic hyaluronate.
The simple squamous epithelium of the thin limbs is slightly thicker than that of the nearby vasa recta capillaries.

Juxtaglomerular Apparatus

The Juxtaglomerular Apparatus (JGA) forms at the point of contact between a nephron's distal tubule and the vascular pole of its glomerulus.
The JGA consists of macula densa, juxtaglomerular granule cells, and lacis cells.
The macula densa is a thickened region of the distal tubule with columnar cells.
Juxtaglomerular granule cells are smooth muscle cells of the afferent arteriole's tunica media that are converted to a secretory morphology.
Lacis cells are extraglomerular mesangial cells adjacent to the macula densa, afferent arteriole, and efferent arteriole.

Renin Release and Blood Pressure Regulation

Decreased arterial pressure leads to increased autonomic stimulation to the JGA, causing the release of renin.
Renin cleaves angiotensinogen into angiotensin I, which is then converted to angiotensin II by angiotensin-converting enzyme (ACE) on lung capillaries.
Angiotensin II is a potent vasoconstrictor that raises systemic blood pressure and stimulates the adrenals to secrete aldosterone.

Collecting Ducts

The connecting tubule extends from each nephron and several join together to form collecting ducts of simple cuboidal epithelium.
In the medulla, collecting ducts merge further to form larger and straighter ducts with increasingly columnar cells.
Collecting ducts are composed mainly of pale-staining principal cells with few organelles, sparse microvilli, and unusually distinct cell boundaries.
Medullary collecting ducts are the final site of water reabsorption from the filtrate.