Renal practical

Question 1

What are the divisions of the suprarenal cortex of the adrenal gland?

Answer 1

it is divided into an outer zona glomerulosa, a zona fasciculata and an inner zona reticularis

Question 2

Describe the appearance of the zona glomerulosa

Answer 2

The zona glomerulosa is clearly defined, with the cells arranged in ovoid clusters and curved columns that are continuous with the cellular cords in the zona fasciculata

Question 3

Describe the appearance of the zona fasicularis.

Answer 3

The cell cords of zona fasciculata run radially towards the medulla showing few branches. Clear sinusoidal spaces between the cords can be seen. Note the vacuolate cytoplasm of the relatively large polyhedral cells in the fascicular zone where cytoplasmic lipid droplets have been dissolved away during histological preparation. This rather typical appearance in standard preparations has resulted in the name spongiocytes being given to the cells.

Question 4

Describe the appearance of the zona reticularis.

Answer 4

The zona reticularis of the cortex is the zone nearest the medulla and can be seen to be made up of a meshwork of cell cords. The cells are smaller, more rounded and more numerous than in the fascicular zone.

Question 5

What are the EM characteristics of steroid secreting adrenal cortical cells are.

Answer 5

Cells of the adrenal cortex have features common to all cells that synthesise and secrete steroid hormones. The three most prominent components of the cytoplasm are:

1. An abundance of smooth endoplasmic reticulum: store enzymes necessary for the synthesis of steroid hormones are stored here.
2. Mitochondria that have peculiarly tubular cristae
3. Lipid droplets

Question 6

What are the main secretory products of each layer of the adrenal gland?

Answer 6

• Zona glomerulus: aldosterone
• Zona fasicularis: cortisol
• Zona reticularis: androgens

Question 7

What do medullary cells of the adrenal gland secrete?

Answer 7

Adrenalin and noradrenalin

Question 8

Describe the appearance of the medulla of the adrenal gland.

Answer 8

The suprarenal medulla comprises large, sometimes ovoid, cells that form irregular clumps and cords surrounding capillary vessels and small veins. The medullary cells (chromaffin cells) contain numerous cytoplasmic granules. The brown coloration represents the secretory product of these cells.

Question 9

What is the embryological origin of the adrenal medulla cells?

Answer 9

Neural crest.

Question 10

The adrenal medulla often considered as a specialised form of which specific component of the nervous system?

Answer 10

Sympathetic nervous system.

Question 11

What type of cells make up the parietal layer of the Bowman’s capsule?

Answer 11

Note the parietal layer of Bowman’s capsule is simple squamous epithelium.

Question 12

What type of cells make up the visceral layer of the Bowman’s capsule?

Answer 12

The visceral layer of Bowman’s capsule comprises specialised podocytes.

Question 13

Define the urinary pole.

Answer 13

where the squamous parietal layer of Bowman’s capsule joins with the cuboidal epithelium of the proximal convoluted tubule.

Question 14

Define the vascular pole.

Answer 14

where the capillary tuft is joined to the afferent and efferent arterioles. From the vascular pole, a central conical-shaped supporting structure, the mesangium, penetrates between capillary loops.

Question 15

What is the function of mesangial cells?

Answer 15

Mesangial cells phagocytose parts of the basal lamina and clear large protein molecules retained during filtration.

Question 16

Define the juxtaglomerular apparatus.

Answer 16

Where a distal convoluted tubule with a dense accumulation of cells - the macula densa - contacts an afferent arteriole whose wall has specialised cells - juxtaglomerular cells

Question 17

What is the function of the juxtaglomerular apparatus?

Answer 17

The juxtaglomerular apparatus consists of a number of cells which collectively monitor blood pressure, and activate the RAS if blood pressure falls.

Question 18

What are mesangial cells? Are there more than one type and do they play a role in the juxtaglomerular apparatus? Do they have any other function?

Answer 18

Mesangial cells are modified smooth muscle cells – there are two types: extraglomerular mesangial cells (Lacis cells) and glomerular mesangial cells.

The Lacis cells act as a conduit between the macula dense and juxtaglomerular cells and between the macula densa and mesangial cells of the conduit.

The intraglomerular mesangial cells are thought to change the size o fthe lumen of the glomerular capillaries by contraction and relaxation.

Question 19

Describe the histological function of the PCT

Answer 19

Surround the renal corpuscle. They comprise a simple cuboidal epithelium and are often appear to be filled with debris. Their cells have a brush border and a markedly acidophilic cytoplasm. They may also show basal striations.

Question 20

What do these basal striations represent in the PCT?

Answer 20

Basal infoldings of the membrane, which contain mitochondria.

Question 21

What is the difference histologically between PCT and DCT?

Answer 21

DCTs are smaller in diameter than those of the PCT. Their cells are “shorter”, with less acidophilic cytoplasm and nuclei that appear to border the lumen. A true brush border is absent. Unlike the PCT, the DCT lumen is usually obvious.

Question 22

Describe the histology of the thin loop portion of of LoH

Answer 22

This tubule is lined with a simple squamous epithelium supported by delicate connective tissue and therefore can easily be mistaken for a blood capillary. The nuclei of the epithelial cells bulge into the lumen.

Question 23

Describe the histology of collecting tubules.

Answer 23

Collecting tubules are lined by a simple cuboidal epithelium. This can grade from cuboidal to columnar as we pass down the duct from cortex to the papilla. Large collecting tubules in the papillary region are called straight renal tubules or Ducts of Bellini. In H&E stained sections, the cell borders are distinct. The cytoplasm is clear and bulges into the lumen, forming a scalloped apical margin. The nuclei tend to stain more darkly than those of surrounding tubules

Question 24

Which portions of the nephron are located in the cortex?

Answer 24

Corticular labyrinths (renal corpuscles, convoluted portions of the nephron – both proximal and distal, peritubular cpaillaries, interlobular arteries and veins), medullary rays

Question 25

Which portions of the nephron are located in the medullary rays?

Answer 25

LoH, collecting tubules and ducts.

Question 26

Which portions of the nephron are located in the medulla?

Answer 26

Collecting tubules and ducts, loops of Henle and vasa recta.

Question 27

How does the length of the loop of nephrons relate to the position of the corpuscle in the cortex - i.e. what are the structural differences between cortical and juxtamedullary nephrons?

Answer 27

Cortical nephrons have a short loop of Henle that may not even penetrate into the medulla. They are involved in the production of bulk urine volume. Their glomerulus is located just below the capsular zone of the kidney. Juxtamedullary nephrons have a long LoH that extends deep into the medulla. They are responsible for maintaining the correct osmolarity of urine. Their glomerulus is located deeper in the medullary cortex – near the border of the medulla.

Question 28

How do the layers of the muscularis of the ureter change from proximally to distally?

Answer 28

It is only in the distal 1/3 of the ureter that the outer longitudinal layer of the muscularis is present.

Question 29

What epithelial tissue is present in the bladder?

Answer 29

Transitional epithelium.

Question 30

Describe the histology of the bladder.

Answer 30

The mucosa of the bladder comprises transitional epithelium and its supporting connective tissue.

The muscle coat is arranged in a number of layers (inner longitudinal, middle circular and outer longitudinal). This formation allows stretching of the bladder wall.

Outside the muscle layer is the serosa, a layer of simple squamous epithelium (mesothelium) supported by a small amount of connective tissue. The serosa only covers the upper surface of the bladder and the tissue block may not come from this part of the bladder.

Elsewhere the outer layer of the wall consists of a fibrous adventitia.

Question 31

Describe the changes in epithelium that occur in the urethra.

Answer 31

Initially it has a lining epithelium of transitional (urinary) epithelium that changes to a stratified columnar and eventually a stratified squamous.

Question 32

Describe the microscopic features of the urethral glands.

Answer 32

Urethral glands (of Littre) form deep branching tubules, epithelial invaginations and lacunae. These glands, which open into the urethra, often contain clear cells that give a positive staining for mucus.