5.2.4: Kidney structure

Question 1

What veins/arteries supply/drain the kidney with blood?

Answer 1

Each kidney is supplied with blood from a renal artery and is drained by a renal vein.

Question 2

What is the role of the kidney?

Answer 2

• Excretion.

- The kidneys remove waste products from the blood and produce urine.

Question 3

What happens to the urine once it is produced in the kidneys?

Answer 3

-The urine passes out of the kidney down the ureter to the bladder where it can be stored until it is released.

Question 4

The kidney consists of three regions surrounded by a tough capsule. Name these three regions.

Answer 4

• The outer region is called the cortex.
• The inner region is called the medulla.
• The centre is the pelvis, which leads into the ureter.

Question 5

What does the bulk of the kidney consist of?

Answer 5

-Tiny tubules called nephrons.

Each kidney contains about one million nephrons.

Question 6

Describe the structure of nephrons.

Answer 6

• Each nephron starts in the cortex at a cup-shaped structure called the Bowman’s capsule.
• The remainder of the nephron is a coiled loop down into the medulla and back into the cortex, before joining a collecting duct that passes down into the medulla.

Question 7

The renal artery splits to form many afferent arterioles, where do these lead to?
Then?

Answer 7

• A knot of capillaries called the glomerulus.
• Blood from the glomerulus continues to an efferent arteriole which carries the blood to more capillaries surrounding the rest of the tubule. These capillaries eventually flow together into the renal vein.

Question 8

What is each glomerulus is surrounded by?

Answer 8

The Bowman’s capsule.

Question 9

What is the process of ultrafiltration?

Answer 9

• Fluid from the blood is pushed into the Bowman’s capsule by the process of ultrafiltration.
• The filter is the barrier between the blood in the capillary and the lumen of the bowman’s capsule

Question 10

The barrier consists of three layers, all adapted to ultrafiltration. What are they?

Answer 10

• The endothelium of the capillary
• The basement membrane
• The epithelial cells of the Bowman’s capsule.

Question 11

How does the endothelium of the capillary act as a filter?

Answer 11

There are narrow gaps between the cells of the capillary wall.
-The cells of the endothelium also contain pores, called fenestrations. These gaps allow blood plasma and the substances dissolved in it to pass out of the capillary.

Question 12

How does the basement membrane act as a filter?

Answer 12

• This membrane consists of a fine mesh of collagen fibres and glycoproteins.
• This mesh acts as a filter to prevent the passage of molecules with a relative molecular mass of greater than 69,000.
• This means that most proteins (and all blood cells) are held in the capillaries of the glomerulus.

Question 13

what are the epithelial cells of the Bowman’s capsule called? and describe their structure.

Answer 13

• These cells, called podocytes have a specialised shape
• They have many finger-like projections, called major processes.
• On each major process are minor processes or foot processes that hold the cells away from the endothelium of the capillary.

Question 14

What do the projections on the podocytes ensure?

Answer 14

• These projections ensure that there are gaps between the cells.
• Fluid from the blood in the glomerulus can pass between these cells into the lumen of the Bowman’s capsule.

Question 15

The Bowman’s capsule leads to the rest of the tubule. What are the three parts called?

Answer 15

• Proximal convoluted tubule.
• loop of Henle.
• Distal convoluted tubule.

Question 16

Where does the fluid from many nephrons go?

Answer 16

-The fluid from many nephrons enter the collecting ducts, which pass down through the medulla to the pelvis at the centre of the kidney