Urinary System

Question 1

What is a meant by a lobe of the kidney?

Answer 1

A kidney LOBE (not lobule) consists of a medullary pyramid, cortex and half of the renal columns on either side.

Question 2

If you looked at a medullary ray under the microscope, what would be the dominant feature?

Answer 2

A medullary ray contains collecting tubules.

Question 3

What does the cortical labyrinth consist of?

Answer 3

The cortical labyrinth consists of renal corpuscles and convoluted tubules.

Question 4

Follow the course of blood through the kidney from the renal artery to the renal vein.

Answer 4

Renal artery -> Segmental arteries -> interlobar arteries -> arcuate arteries -> interlobular arteries -> afferent arterioles -> glomerular capillaries -> efferent arterioles -> cortical capillary plexus.

From there blood can drain to the interlobular veins or the vasa recta

Question 5

Where does the capillary plexus in the cortical labyrinth come from?

Answer 5

The capillary plexus around the convoluted tubules arises comes from efferent arterioles.

Question 6

What is unusual about the embryonic development of the nephron and the collecting ducts?

Answer 6

The components of the nephron and the collecting ducts have different embryonic origins and must connect during embryogenesis.

Question 7

Which tubules in the cortex are located in the center of a lobule of the kidney?

Answer 7

Collecting ducts are located in the center of the kidney lobule since the lobule is defined as all of the uriniferous tubules draining into a collecting duct.

Question 8

Where are renal corpuscles located in the cortex?

Answer 8

85% of renal corpuscles are in the upper cortex, while 15% are juxtamedullary.

Question 9

What is a uriniferous tubule?

Answer 9

A uriniferous tubule is nephron plus the collecting tubule.

Question 10

What is a nephron?

Answer 10

A The juxtamedullary renal corpuscles have longer loops of Henle, extending deeper into the renal medulla. is the kidney structure from the renal corpuscle through the distal convoluted tubule (but not the collecting tubule or duct).

Question 11

What is different between the uriniferous tubules of juxtamedullary renal corpuscles?

Answer 11

The juxtamedullary renal corpuscles have longer loops of Henle, extending deeper into the renal medulla.

Question 12

What is the barrier between the blood and the urinary space (Bowman’s space) in the renal corpuscle?

Answer 12

The barrier consists of fenestrated endothelium, a basement membrane, and podocytes with filtration slits between pedicles.

Question 13

What is the site of filtration?

Answer 13

Glomerulus and capsule site

Question 14

What is the structure of the visceral layer of Bowman’s membrane? The parietal?

Answer 14

The visceral layer consists of podocytes; the parietal layer consists of simple squamous cells.

Question 15

What is the function of mesangial cells?

Answer 15

Mesangial cells clean deposited proteins off of the basement membrane of the glomeruli. Also have contractile ability to regulate glomerular blood flow

Question 16

What is unusual about the basement membrane of the glomerulus?

Answer 16

The basement membrane has charged proteins and proteoglycans to filter big proteins.

Question 17

What is the progression of filtrate through the uriniferous tubules?

Answer 17

Filtrate progress through proximal convoluted tubules, thick descending limbs (of Henle), thin descending limb, thin ascending limb, thick ascending limb and the distal convoluted tubule. This ends in a collecting tubule that connects to a collecting duct.

Question 18

What is the structure of the wall of the distal convoluted tubules?

Answer 18

The DCT consists of simple cuboidal epithelium without a brush border.

Question 19

On H&E stain, how can you distinguish PCT from DCT?

Answer 19

The cells of the PCT are redder (more eosinophilic) and taller than the cuboidal cells of the DCT. Also the cells of the PCT have microvilli.

Question 20

What is the structure of proximal convoluted tubules?

Answer 20

The PCT consists of simple cuboidal epithelium with a brush border.

Question 21

A renal lobule is defined by:

Answer 21

All of the nephrons that drain into a collecting duct

Question 22

What is the structure of descending and ascending thin limbs (of Henle)?

Answer 22

They are comprised of simple squamous epithelium.

Question 23

Why are the thin decending and ascending limbs adjacent to one another.0?

Answer 23

This allows countercurrent exchange of sodium to prevent dilution of the sodium concentration in the renal medulla.

Question 24

What is the function of the thick limb of Henle?

Answer 24

It is impermeable to water but pumps sodium to produce a high sodium concentration in the renal medulla.

Question 25

What is the structure of the collecting ducts?

Answer 25

Collecting ducts are lined by cuboidal epithelium with prominent infoldings of lateral cell borders.

Question 26

What hormone has the most powerful influence on collecting ducts?

Answer 26

Collecting ducts are affected by anti-diuretic hormone (ADH) that allows water to escape from the collecting duct into the medulla of the kidney, where it is picked up by the vasa rectae.

Question 27

What are the components of the juxtaglomerular apparatus?

Answer 27

The JGA consists of several compnents. The macula densa, which is a specialization of the DCT that detects Na+ and fluid levels. Juxtaglomerular cells (JG) are modified smooth muscle cells that secrete renin. Extraglomerular mesangial cells have a function that is not well understood.

Question 28

What do JG cells secrete and how do they affect the body?

Answer 28

JG cells secrete rennin, which converts angiotensinogen to angiotensin I. This, in turn, is converted to angiotensin II by angiotensin converting enzyme. Angiotensin II has effects on blood vessel contraction and on secretion of aldosterone from the adrenal cortex. This hormone, in turn, causes blood volume elevation by fluid retention at the DCT.

Question 29

What is the pathway for urine from the medullary pyramid outward?

Answer 29

Collecting ducts open onto the renal papilla, which empties urine into the minor calyx, to the major calyx, to the renal pelvis, to the ureter, to the urinary bladder and finally out the urethra.

Question 30

What is the epithelium that lines the lower urinary tract?

Answer 30

It is transitional epithelium (urothelium), which changes shape (flattens) when the system is distended. These cells have prominent terminal bars.

Question 31

What are the layers of the ureter?

Answer 31

The mucosa is on a thick lamina propria. It has no submucosa. There is a thick muscularis, but layers are not distinct. There is an adventitia outside.

Question 32

What is the structure of the urinary bladder?

Answer 32

It has a lining of transitional epithelium on a lamina propria. There is no submucosa but a thick smooth muscle layer. Outside is an adventitia.