8-4 Functional Anatomy of the Kidney

Question 1

What are 6 physiological functions of kidneys?

Answer 1

• Regulate body fluid solute balance (osmolality)
• Regulate vascular and extracellular fluid volume (Na+)
• Maintenance/regulation of blood pressure (renin, angiotensin)
• Regulate acid-base balance (H+ concentration)
• Eliminate metabolic wastes, foreign chemicals
• Hormone production (erythropoietin, vitamin D)

Question 2

Renal microcirculation is somewhat unusual - it contains 4 things in series. What are they?

Answer 2

Afferent arteriole

glomerular capillaries

efferent arteriole

peritubular capillaries/capillar bed

Question 3

What are the relative hydrostatic pressures in each capillary network?

Answer 3

First capillary network (glomerular capillaries): high hydrostatic pressure; large fluid volume filtered into Bowman’s capsule

Second capillary network (peritubular capillaries): low hydrostatic pressure; large amounts of water and solute are reabsorbed

Question 4

What is the path of the renal blood supply?

Answer 4

Renal aa –> segmental aa –> interlobular –> arcuate –>

cortical radiate –> afferent arterioles –> glomerular capillaries –>

efferent arterioles –> peritubular capillaries

Question 5

Why are the majority of nephrons cortical? What do the juxtamedullary nephrons do?

Answer 5

Juxtamedullary nephrons create hyperosmotic intersitium for concentration of urine

Cortical nephrons do the majority of filtration

Question 6

How does damage to the glomerular arterioles affect other, related vascular structures?

Answer 6

Damage to glomerular arterioles harms the tubule downstream, the efferent arteriole and the peritubular capillary bed

Question 7

Where is renin secreted from in the kidney?

Answer 7

myoepithelial cells lining the interlobular aa

Question 8

What does a renal corpuscle include?

Answer 8

Bowman’s capsule and glomerulus

Question 9

The filtration apparatus between capillary lumen and Bowman’s space includes what 3 layers?

Answer 9

1. Fenestrated capillary endothelium: highly permeable to water, dissolved solutes
2. Glomerular basement membrane: collagen, proteoglycans contain anionic (negative) charges
3. Podocyte epithelium: slit pores between podocytes restrict large molecules

Question 10

The basement membrane is made up of what 3 layers? What do the layers filter?

Answer 10

(Vascular side)

lamina rara interna - charge barrier

lamina densa - size barrier

lamina rara externa - charge barrier

Question 11

What are the 3 major components of the basement membrane? What layers are things concentrated in, and why?

Answer 11

BM made up of Type IV collagen, laminin, and negatively charged heparan sulfate

Negatively charged heparan sulfate is concentrated in lamina rara externa and interna in order to maintain charge barrier

Question 12

What features of the BM keeps albumin in the capillary lumen?

Answer 12

Albumin is anionic, and will be repelled by the negatively charged heparan sulfate in lamina rara interna and externa

Slit diaphragm also helps to keep albumin in

Question 13

What is in slit diaphragms to keep large molecules in the capillary lumen?

Answer 13

Nephrin molecules stretch between podocytes, across the slit diaphragm

• anchored by Podocin, CD2AP and actin filaments

Question 14

What gives rise to nephrotic syndrome?

Answer 14

Mutations in genes encoding nephrin molecules