Genitourinary System

1
Genitourinary System
2
Functions of the Kidney

• Excretion
• Removal from the body of the waste products of
  metabolic pathways
• Osmoregulation
• Is the control of the water balance of the blood,
  tissue, or cytoplasm of a living organism.

3
Kidney Structure
4
Nephron the functional unit of the kidney
5
Ultrafiltration in the glomerulus
6
Ultrafiltration specifics

• Production of filtrate from blood
• 20 of blood plasma passes through walls of
  glomerulus higher than any other cap. bed.
• Why?
• 1. bp is very high due to diameter differences of
  the efferent and afferent arterioles
• 2. glomerular capillaries are fenestrated
• Pores large all substances can pass through
• But basement membrane acts as a filter

7

• The Urinary System
• Plasma, Filtrate, and Urine ComparisonsTable. Aver
  age Composition of Blood Plasma, Glomerular
  Filtrate, and Urine 
•   Blood Plasma Glomerular Filtrate Urine
• Substance  (total amount) (amount per day)
  (amount per day)
• Water 3 L 180 L 1-2 L
• Urea 4.8 g 53 g 25.0 g
• Chloride 10.7 g 639 g 6.3 g
• Sodium 9.7 g 580 g 4.6 g
• Potassium 0.5 g 30 g
  2.0 g
• Creatinine 0.03 g 1.6 g 1.6 g
• Uric acid 0.15 g 8.5 g 0.8 g
• Protein 200.0 g 2.0 g 0.1 g
• Bicarbonate 4.6 g 275.0 g 0.0
  g
• Glucose 3.0 g 180.0 g 0.0 g

8
Selective Reabsorption in the PCT

• Filtrate at this point contains waste and
  substances the body needs
• PCT consists of a single layer of cuboidal
  epithelial cells with microvilli increased SA

9
PCT contd

• IMPs all cell over surfaces for AT
• Mitochondria in large numbers producing ATP to
  drive AT

10
Whats Re-absorbed?

• 100 of glucose
• 80 of mineral ions (including Na)
• AT of solutes makes cell hypertonic
• which cause water to follow.
• 80 of water is re-absorbed 20 of water remains
  in the renal tubule and heads towards the LOH

11
Role of the LOH

• Descending and acsending limbs differ in
  permeability.
• Major role?
• To create an area of high solute conc. in the
  medulla (hypertonic interstitial fluid)

12
Osmoregulation in the CD

• Water conc. in blood too low
• ADH release from pituitary gland in brain
• Increase in aquaporin production in CD cells
• CD passes through zone of high solute conc
  created earlier by the LOH
• Hypertonic urine is produced

13

• If water conc in blood is too high (hypotonic
  blood)
• ADH is not secreted
• Aquaporins are broken down
• CD becomes less permeable to water
• Dilute, hypotonic urine is produced