Lecture #30: Renal Histology

Question 1

What is the functional unit of the kidney?

Answer 1

Nephron

Question 2

Approximately how many nephrons are there per kidney?

Answer 2

1 million

Question 3

What are the two different types of nephrons?

Answer 3

> Cortical Nephron

> Juxtamedullary Nephron

Question 4

What do the glomeruli of cortical nephrons empty into?

Answer 4

Peritubular capillary networks that surround the proximal and distal convoluted tubules of their own nephrons and those of surrounding nephrons.

Question 5

What do the glomeruli from juxtamedullary nephrons empty into?

Answer 5

Vasa recta consisting of long, straight arterioles and venules that run parallel to the loops of Henle and collecting ducts.

Question 6

True or False:

Juxtamedullary nephrons have long loops of Henle that extend deeply into the medulla.

Answer 6

True

Question 7

True or False:

Cortical nephrons have long loops of Henle that do not extend deeply into the medulla.

Answer 7

False -> Cortical nephrons have SHORT loops of Henle that do not extend deeply into the medulla.

Question 8

True or False:

The renal corpuscles of both juxtamedullary and cortical nephrons are located in the cortex of the kidney.

Answer 8

True

*but the juxtamedullary nephrons are in the cortex next to the cortical-medullary junction (hence the name).

Question 9

Starting at the renal artery and ending at the renal vein, list out the sequence of vessels in which blood flow through the kidney.

Answer 9

renal artery ->
interlobar arteries ->
arcuate arteries ->
interlobular arteries ->
afferent arterioles -> Glomeruli -> efferent arterioles ->
vasa recta or peritubular capillaries ->

interlobular veins ->
arcuate veins ->
interlobar veins ->
renal vein

Question 10

What are the two different routes that an efferent arteriole can feed into?

Answer 10

> a capillary loop, the vasa recta

> a capillary network, the peritubular capillaries

Question 11

What are juxtaglomerular cells? Also, what do they secrete?

Answer 11

Circular smooth muscle cells located at the vascular pole.

They secrete renin (hypertensive factor)

Question 12

What makes up the glomerulus?

Answer 12

Afferent arteriole
Glomerular formation of capillaries
Efferent arteriole

Question 13

What are the 2 layers of the Bowman’s capsule?

Answer 13

1) Parietal layer

2) Visceral layer

Question 14

What epithelium lines the parietal layer, and what epithelium is this continuous with?

Answer 14

Parietal layer is the outer layer of the Bowman’s capsule and is simple squamous epithelium.

The squamous epithelium is continuous with the simple cuboidal epithelium of the proximal convoluted tubule.

Question 15

What is the visceral layer of the Bowman’s capsule?

Answer 15

This is the inner layer of podocytes in contact with the endothelium of the glomerular capillaries.

Question 16

Is the visceral layer or the parietal layer the outer layer of the Bowman’s capsule?

Answer 16

Parietal Layer is the outer layer.

Question 17

True or False:

The visceral layer is the inner layer of the Bowman’s capsule of podocytes in contact with the endothelium of the glomerular capillaries.

Answer 17

True

Question 18

Where is the Bowman’s space located?

Answer 18

Bowman’s space is located between the parietal and visceral layers and is continuous with the lumen of the proximal convoluted tubule.

Question 19

What is the difference between the function of the renal corpuscle and the rest of the nephron, including the convoluted portions and the loop of Henle, as well as the collecting tubules?

Answer 19

Renal Corpuscle -> involved in producing a filtrate of blood.

The Rest -> involved in modifying the filtrate.

Question 20

What 3 processes are involved in the formation of urine?

Answer 20

Filtration (occurring in renal corpuscle)

Reabsorption (occurring in renal tubule)

Secretion (occurring in renal tubule)

Question 21

True or False:

The mesangium is part of the glomerulus.

Answer 21

True

Question 22

Where are intraglomerular mesangial cells located?

Answer 22

Between nearby capillaries in the glomerulus and cover endothelium not covered by podocytes.

Question 23

Where are extraglomerular mesangial cells located?

Answer 23

Between the afferent and efferent arterioles at the vascular pole and are associated with the juxtaglomerular apparatus.

Question 24

True or False:

The mesangium is formed by mesangial cells embedded in a mesangial matrix.

Answer 24

True

Question 25

What are the characteristics and functions of mesangial cells?

Answer 25

> contractile: utilize cytoskeletal contractile proteins to modify blood flow through glomerular capillaries

> phagocytic: take up worn out glomerular basal lamina for recycling and also phagocytose immunoglobulins trapped in the basal lamina

> proliferative

> synthesize matrix and collagen

> secrete prostaglandins and endothelins

> respond to angiotensin II

> provide mechanical support and regulate blood flow

Question 26

Look at figure 14-6 and figure 14-9 in the lecture.

Answer 26

Specifically at the macula densa and mesangial structures.

Question 27

What does the urinary system consist of?

Answer 27

> 2 Kidneys
2 Ureters
Urinary Bladder
Urethra

Question 28

What makes up the juxtaglomerular apparatus?

Answer 28

> macula densa

> extraglomerular mesangial cells

> juxtaglomerular cells

Question 29

What is the macula densa formed by?

Answer 29

Formed by elongated, densely packed cells in the wall of the convoluted tubule.

• polarity of these cells is reversed.

Question 30

Made does the macula densa function to do?

Answer 30

> responds to changes in sodium and chloride concentration in the urine or hypotenssin.

> signals renin release from juxtaglomerular cells

> involved in regulation of fluid-electrolyte balance and blood pressure regulation.

Question 31

What are juxtaglomerular cells? Also, what do they secrete, what are they stimulated by, and what are they innervated by?

Answer 31

Modified smooth muscle cells associated with macula densa and afferent arterioles.

Secrete -> renin
Stimulated by -> macula densa
Innervated by -> sympathetic nerve endings, which increase renin release.

Question 32

What are the components of the renal filtration barrier?

Answer 32

> fenestrated endothelium of glomerular capillaries

> fused basal laminae of endothelial cells and podocytes

> filtration slits

Question 33

What is the selectivity of the renal filtration barrier?

Answer 33

> water, glucose, and most ions pass through filter into Bowman’s space

> proteins are typically excluded from passing across the filter

> molecules with a large negative charge are excluded

Question 34

What are the filtration slits of the renal filtration barrier?

Answer 34

> fenestrated endothelium of capillaries
basal lamina:
- contains type IV collagen, fibronectin, laminin, heparin sulfate
filtration slits created by adjacent pedicels of podocytes:
- covered by filtration slit diaphragm
- pedicels are attached to basal lamina via alpha3beta1 integrins

Question 35

What are the functions of the proximal convoluted tubule?

Answer 35

> reabsorbs most of the filtrate, including water

> removes essentially all the glucose and amino acids from the filtrate

> reabsorbs most of the sodium and chloride ions

> characterized by a complex set of transporters, co-transporters, channels, and exchangers

Question 36

Describe the histology of the proximal convoluted tubule and the specifics of the cells that make up the tubular wall.

Answer 36

> extends from the urinary pole of the renal corpuscle to the beginning of the loop of Henle.

> Characteristics:
- simple cuboidal epithelium made up of truncated pyramidal cells

  - apical (facing lumen of tubule) tight junctions and brush border
 - basolateral infoldings and interdigitations
 - basal striations with abundant mitochondria (for active transport across basal membrane) 
 - large, pale-staining nuclei 
 - eosinophilic cytoplasm