The Renal System

Question 1

How much water does adipose tissue contain?

Answer 1

10-20%

Question 2

How much water does skeletal muscle contain?

Answer 2

75%

Question 3

What is Osmolarity?

Answer 3

The number of moles of solute dissolved in a volume of solution, measured as Osm/L

Question 4

What is osmolality?

Answer 4

Osmoles of solute dissolved per kg of solvent Osm/kg

Question 5

What is the functional unit of filtration?

Answer 5

The Nephron

Question 6

Describe the renal cortex

Answer 6

Peripheral tissue of the kidney, extending into the medullary regions

Contains blood vessels, glomeruli, proximal & distal convoluted tubules

Question 7

Describe the renal medulla

Answer 7

Formed from renal pyramids which consist of mainly loops of Henle and collecting ducts

Question 8

What size is a nephron?

Answer 8

30-55mm

Question 9

What are the 4 main regions of the nephron?

Answer 9

Bowman’s capsule, conntaining specialised vascular structures called glomerulus

Proximal convoluted tubule

Loop of Henle

Distal convoluted tubule, specialised structure called the juxtaglomerular apparatus. DCT then empties into the collecting duct then into papillae

Question 10

What is the function of the glomerulus?

Answer 10

To control the rate of urine production by regulating bloodflow both in and out of the Bowman’s capsule by altering the diameter of the afferent and efferent arterioles

Question 11

How does glomerular filtration rate increase/decrease

Answer 11

Vasoconstriction of the Afferent arteriole decreases GFR

Vasoconstriction of the efferent arteriole increases GFR

Question 12

Describe the structure of proximal convoluted tubule

Answer 12

around 14mm long and 60um in diameter

Walls consist of simple cuboidal epithelium

Luminal surfaces are covered with microvilli

Around 65% of trhe water in the flitrate is reabsorbbed

Majority of essential nutrients and electrolytes are reabsorbed

PCT terminates at the start of the loop of Henle

Question 13

What is the role of the proximal convoluted tubule

Answer 13

Regulates reabsorption of H2O, Na+, HCO30 and glucose into the peritubular capillary

Question 14

Describe the thick ascending limb of the loop of henle

Answer 14

Impermeable to water

Sodium, Potasium and Chloride ions are actively pimped out of the lumen, driven by a sodium-potassium ATPase pump in the basal membrane

Question 15

Describe the distal convoluted tubule

Answer 15

Shorter than PCT

Permeability is under the control of ADH, which increases permeability ot H2O

Question 16

Describe the DCT’s Na+/k+ exchanger

Answer 16

Na and Cl- transport is mediated by the Na+/K+ ATPase pumps in apical and basal membranes

An aldosterone-sensitive region of the DCT can be activated by low blood pressure which increases sodium ion reabsorption

Question 17

How is acid-base balance maintained by the DCT?

Answer 17

Secretion of H+ from blood and reabsorption of HCO3

Loss of H+ ions and retention of HCO3

Question 18

What is the role of the collecting duct in concentrated urine production?

Answer 18

Renin is released from JG cells when sodium ions rise, this converts angiotensinogen to angiotensin I AI

AI is converted by ACE to anginotensin II

This promotes release of ADH and aldosterone

ADH induces aquaporin membbrane expression and aldosterone increases reabsorption of NaCl and H2O

allows generation of urine at 1200mOsmol/L