Lecture 29: Renal

Question 1

Be able to describe the basic structure of the renal corpuscle, including the vascular supply.

Answer 1

Renal corpuscle(filter): glomerulus (fed by afferent goes to efferent), bowmans capsule ( double layered cup-shaped dilation of nephron; inner/outer layer=visceral/parietal), bowmans space is btw inner/ outer bowmans capsule.

Renal artery-> number of branches (interlobar arteries->arcuate arteries-> interlobular arteries->to afferent glomerular arteries->glomerulus

Efferent arterioles-> vasa recta/peritubular capillaries->interlobular veins->arcuate veins->interlobar veins->renal vein

Question 2

Describe the structure of the extraglomerular and intraglomerular mesangium

Answer 2

Mesangium: part of the glomerulus.

• Formed by mesangial cells embedded in mesangial matrix
• Interglomerular:located btw nearby capillaries in the glomerulus and cover endothelium not covered by podocytes.
• Extraglomerular: located btw afferent/efferent arterioles at the vascular pole and are asso. W/ juxtaglomerular apparatus.

Question 3

List the functions of the mesangium

Answer 3

Slide 19

• Contractile: uses cytoskelton contractile proteins to modify blood flow through glomerular capillaries.
• phagocytic: recycle worn out glomerular basal lamina.
• proliferative
• synthesize matrix and collagen.
• secrete prostaglandins and endothelins
• respond to ANGIOTENSIN II
• provide mechanical support and regulate blood flow

Question 4

List the components of the juxtaglomerular apparatus

Answer 4

Macula densa

Extraglomerular mesangial cells

Juxtaglomerular cells

Question 5

Describe the histology of and the functions of the macula densa, and the juxtaglomerular cells; indicate where each is found

Answer 5

Macula densa: “dense spot” elongated row of packed cells in convuluted tubule. Polarity reveresed. Signals renin release from JG cells. Involved in fluid-electrolyte balance.

Extraglomerular mesangial cells:

Juxtaglomerular cells: smooth muscle cells asso. W. macula densa and afferent arteriole. Secrete release of renin after signaled by macula densa.

Question 6

List in order the components of the renal tubule.

Answer 6

PCT
Descending limb of henle 
Loop of henle
Ascending limb of henle. 
Distal convoluted tubule-> continuous w/ collecting duct

Question 7

List and describe the histology of the components of the renal filtration barrier

Answer 7

Fenestrated endothelium of glomerular capillaries: leaky type of capillary

Fused basal laminae of endothelial cells and podocytes

Filtration slits: fenestrated endothelium (pores), basal lamina-typeIV collagen w/ selection capacity(water, glucose, ions pass; proteins shouldn’t. Negative charges shouldnt pass. Slits adjacent pedicels of podocytes. Foot like process of podocytes. Narrow slits btw them, anchored by alpha3ß1 integrin

Question 8

Describe the histology of the proximal convoluted tubule and the specifics of the cells that makeup the tubular wall

Answer 8

• Simple cuboidal epithelium made of truncated pyramidal cells.
• apical tight junctions and brush border.
• basolateral infoldings and interdigitations
• basal striations w/ abundant mito,.
• large-pale staining nuclei
• eosinophil if cytoplasm

Question 9

List the functions of the PCT:

Answer 9

Reabsorb most of filtrate including water

Removes essentially all the glucose and AAs from filtrate

Reabsorbs most of the Na+ and Cl- ions

Characterized by a complex set of transporters, co-transporters, channels, and exchangers.

Question 10

Be able to identify components of renal corpuscle and proximal convulted tubule on slides in class.

Answer 10

K

Question 11

Learn the structure of the nephron and compare the histological characteristics of each part of the nephron from slides presented in class and r/ the specialized structure of each part of the uriniferous tubule to its function.

Answer 11

Loop of henle:

• thick:simple low cuboidal, NO brush border and more basal vertical striations
• thin: simple squamous epithelium
• Function: establish the counter-current exchange system which creates the osmotic conditions necessary to pull water out of the distal convoluted tubule and collecting duct in the presence of ADH

DCT: simple cuboidal epithelium. Smaller cells, larger lumen than PCT. but NO brush border. Permeable to water ONLY WHEN ADH present

Collecting: simple cuboidal. principal cells(reabsorb Na+/water and secrete K+) and intercalated cells (secrete either H+ or HCO3)present here.

PCT-brush border