5.2.4 kidney structure

Question 1

nephron

Answer 1

functional unit of kidney

Question 2

ultrafiltration

Answer 2

filtration of blood at molecular level under pressure

Question 3

how is the blood supplied/removed from the kidney

Answer 3

• blood supplied by renal artery
• blood drained by renal vein

Question 4

3 regions of kidney

Answer 4

1. outer region = cortex
2. inner region = medulla
3. centre = pelvis - leads to ureter

Question 5

fine structure of kidney

Answer 5

• tiny tubules = nephrons
• each kidney has ~1 million nephrons
• each nephron begins in cortex at cup-shaped structure = bowman’s capsule
• remainder of nephron is coiled tubule passing through cortex
• forms loop into medulla (loop of henle) & passes back into cortex
• joins collecting duct which passes back down into medulla

Question 6

blood supply to kidney

Answer 6

• renal artery splits forming many arterioles
• each arteriole leads to knot of capillaries = glomerulus
• blood from glomerulus continues into efferent arteriole -> carries blood to more capillaries surrounding rest of tubule (nephron)
• capillaries eventually flow together into renal vein

Question 7

what is each glomerulus surrounded by

Answer 7

= bowman’s capsule
- fluid from blood pushed into bowman’s capsule by ultrafiltration

Question 8

how is blood filtered between the bowman’s capsule & glomerulus (capillaries)

Answer 8

barrier between blood in capillary & lumen of bowman’s capsule

Question 9

name the 3 layers - barrier between capillaries & bowman’s capsule

Answer 9

1. endothelium of capillary
2. basement membrane
3. epithelial cells of bowman’s capsule

Question 10

describe layer 1: endothelium of capillary

Answer 10

• narrow gaps between cells of endothelium of capillary wall
• cells of endothelium contain pores = fenestrations
• gaps allow blood plasma & substances dissolved to pass out of capillary

Question 11

describe layer 2: the basement membrane

Answer 11

• consists of fine mesh of collagen fibres & glycoproteins
• acts as filter to prevent passage of molecules with relative molecular mass exceeding 69,000
• means most proteins (& all blood cells) held in capillaries of glomerulus

Question 12

describe layer 3: epithelial cells of bowman’s capsule

Answer 12

= podocytes
- specialised shape
- many finger-like projections = major processes
- on each major process are minor processes/foot processes which hold cells away from endothelium of capillary
- ensure gaps between cells
- fluid from blood in glomerulus can pass between cells into lumen of bowman’s capsule

Question 13

the bowman’s capsule leads into the rest of the tubule (nephron)
name the 3 parts of the nephron

Answer 13

• proximal convoluted tubule
• loop of Henle
• distal convoluted tubule

Question 14

where does the fluid from many nephrons go

Answer 14

• enters collecting ducts
• these pass down through medulla to pelvis at centre of kidney