RENAL: Overview of the Structure and Function of Kidneys

Question 1

What are the functions of the kidneys?

Answer 1

• Make urine
  
  • Controls body fluid volume and chemical composition
    
    • Release major molecules, e.g. Vit D, EPO, Renin
    • Input from nerves and hormonal systems (sympathetic, ADH, ANP, aldosterone, PTH)

Question 2

What is the position of the cortex?

Answer 2

Outermost zone, contains glomeruli of nephrons

Question 3

What is the position of the medulla?

Answer 3

Innermost zone, hyperosmotic, contains loop of Henle, collecting ducts of nephrons, vasa recta

Question 4

Describe the function of the calyx

Answer 4

Drainage areas taking urine from collecting ducts to ureters

Question 5

Describe the nephrons

Answer 5

2 types:

• Cortical
• Juxtamedullary - longer loop of Henle, deep into medulla

Function of nephrons are:

• Overall function - regulation of H2O, substrate, electrolytes through filtration, reabsorption, secretion

Question 6

Describe renal circulation

Answer 6

• Afferent arteriole - Brings blood into glomerulus
• Efferent arteriole - Takes blood away from glomerulus to peritubular capillaries and vasa recta
• Vasa recta - Specialised capillaries at loop of Henle (Counter-current exchange)

Constriction/dilation of these vessels regulate glomerular filtration (GFR)

Question 7

Describe the structures of the juxtamedullary renal tubules and their functions

Answer 7

• Juxtaglomerula apparatus (JGA) - regulates GFR - Afferent arterioles (granular cells, Renin), efferent arterioles, macula densa (Na+/Cl-), sympathetic nerves
• Glomerulus - Filtration unit
• Thin descending loop of Henle - Permeable to H2O not Na+
• Thin ascending loop of Henle - Permeable to Na+ not H2O
• Thick ascending loop of Henle - Permeable to Na+/K+/2Cl-
• Distal tubule - Na+ reabsorption
• Collecting duct - H2O reabsorption, Na+ reabsorption, H+/HCO3- balance, urea reabsorption