Prac 10 - Urinary System

Question 1

With the naked eye the human kidney can be seen to be divided into a pale coloured cortex and darker regions of medullary tissue. The kidney contains 10 to 15..

Answer 1

medullary pyramids (lobes) whose apices point towards the hilum of the kidney. Each pyramid is surrounded on three sides by cortex.

Question 2

The cortex contains

Answer 2

all of the glomeruli of the kidney and the convoluted (coiled) parts of the proximal and distal tubules. It also contains the first (proximal) parts of the collecting ducts.`

Question 3

The medullary pyramids contain the

Answer 3

straight portions of the proximal and distal tubules, the loops of Henle and the distal parts of the collecting ducts.

Question 4

The filtrate drains from each medullary pyramid by

Answer 4

up to 20 pores into a funnel-shaped calyx from where the urine is collected into the widened pelvic portion of the ureter for transport to the bladder.

Question 5

Normally the renal artery divides into.. and what arise fromthese

Answer 5

five or six main branches that give off arcuate arteries at the cortico-medullary junction. From these arise the interlobular arteries.

Question 6

The interlobular arteries penetrate the cortex at regular intervals dividing the cortex into lobules. They give off … that supply what

Answer 6

afferent arterioles that supply the glomeruli. Here the blood is filtered.

Question 7

The filtered blood leaves the glomeruli via and passes through where? what happens here

Answer 7

the efferent arterioles and passes through thin-walled vessels between the tubules. Here it acquires fluid and ions recovered by the nephrons before draining into arcuate veins for return to the systemic circulation.

Question 8

Near the cortico-medullary junction the arcuate arteries also give off what? and what do they do?

Answer 8

straight arterioles that penetrate deep into the medulla (vasa recta) before returning blood to the arcuate veins.

The precise relationships between the blood vessels and the tubules of the nephrons are fundamental to the process of filtration and the recovery of solutes.

Question 9

Blood entering the kidney passes first to the

Answer 9

glomeruli where it is filtered. The primary filtrate is then passed to the rest of the nephron for the selective re-absorption of certain solutes.

Question 10

A glomerulus consists of

Answer 10

a parallel array of fenestrated capillaries ensheathed by specialised endothelial cells called podocytes.

Question 11

what is the filtration barrier of the kidney

Answer 11

The basement membrane between the endothelial cells of the capillaries and the podocytes of the epithelium

Question 12

Where do important matrix-forming mesangial cells lie

Answer 12

Between the coiled loops of the glomerular tuft

Question 13

The wall of the afferent arteriole contains

Answer 13

specialized renin-producing cells.

Question 14

macula densa what is this

Answer 14

Alongside the glomerulus is a segment of distal tubule (from the same nephron) that has a specialized palisade of cells known as the macula densa.

Question 15

In histological sections, the glomerular tuft can be seen to arise from the … what is this

Answer 15

vascular pole, the point of entry into the glomerulus of the afferent arteriole and the point of exit of the efferent arteriole.

Question 16

The tuft consists of

Answer 16

capillary loops supported by podocytes. It is surrounded by the urinary space that separates it from the glomerular capsule (Bowman’s capsule).

Question 17

In the angle between the afferent and efferent arterioles lies

Answer 17

a returning distal loop of the same nephron. This often displays a compact palisade of cells known as the macula densa.

Question 18

At the heart of the filtration barrier lies a basement membrane.
This is synthesized and maintained jointly by

Answer 18

the endothelial cells of the capillaries and the epithelial cells (podocytes) that ensheath them.

Question 19

complex foot processes.

Answer 19

The endothelial cells are fenestrated and the podocytes ‘stand off’ from the membrane - in the filtration barrier
This arrangement creates physical pores between the cells guarded only by the filtration membrane.

Question 20

The charged nature of this membrane restricts the passage of some molecules but fundamentally whats able to pass through

Answer 20

water and solutes up to about 50,000 Daltons are able to pass to into the urinary space and constitute the primary filtrate.

Question 21

what is the mostly highly coiled segment

Answer 21

This is the first segment of the tubule of the nephron. It is the mostly highly coiled segment although a straight distal portion projects in some cases into the medulla.

Question 22

what do the cells of the proximal tubules look like

Answer 22

The cells have a prominent brush border and complex invaginations of their baso-lateral membrane.

Question 23

What happens at the proximal tubule

Answer 23

Extensive re-absorption of the filtrate takes place in this segment. Sodium is actively transported and glucose with it. Amino acids probably follow a similar route.
The cells take up proteins and polypeptides by endocytosis and the cells can often be seen to contain lyzosomes which help to break down these proteins before returning their constituents to the circulation.

Question 24

The thin loops vary in length, being longest and penetrating deeper into the medulla in those belonging to

Answer 24

nephrons whose glomeruli lie close to the cortico-medullary junction.

Question 25

The ascending portion of the thin limb does what

Answer 25

retains water although chloride and sodium are re-absorbed. This results in the production a dilute (hypotonic) filtrate (urine) but an interstitium that is hypertonic. Long straight capillaries known as vasa recta run alongside these tubules.