Lecture 38

Question 1

What is percentage for total body water for females and males?

Why does it differ?

Answer 1

Males = 60%
Females = 55%
Total body water for a 70kg male = 42L
Total body water for a 70kg female = 38L

Question 2

How is body water distributed in ICF and ECF

Answer 2

ICF: is the amount of water present in cells = 2/3 of body water
Male = 28L, Female = 25L

ECF: is the amount of water outside the cells = 1/3 of body water
Male = 14L, Female = 13L

Question 3

The extracellular fluid can then be divided into what two volumes?

Answer 3

Interstitial fluid: this is the fluid that lies in between cells = 4/5 of ECF
Male = 11.2, Female = 10.5

Plasma: is the fluid present in blood = 1/5 of ECF is plasma
Male = 2.8, Female = 2.5

Question 4

Describe how total body water remains relatively constant?

• describe osmolarity
• why is osmolarity regulated?

Answer 4

Kept constant though the intake and loss of water; urine output is adjusted to maintain balance.

Osmolarity is the same in the ECF and ICF = 275-294mosmol/L
- regulate water to regulate osmolarity to regulate cell size

Question 5

What is the most prominent ion in the ECF and ICF?

Answer 5

ECF = Na+

ICF = K+

Question 6

ASH is a hormone released from the posterior pituitary gland. What are the two major stimuli for release?

What affect does ADH have?

Answer 6

1. Increased ECF osmolarity
2. Decreased blood volume

ADH inserts channel - aquaporins in the luminal membrane of the collecting duct which increases H2O reabsorption

Question 7

What happens when there is no ADH?

Answer 7

• collecting duct is relatively impermeable to water
• majority of water remains in CD and is not reabsorbed
• increased water loss in urine
• large volume of dilute urine

Question 8

What happens with ADH?

Answer 8

• collecting duct is more permeable to water
• water absorbed from CD down HOMG
• decreased water loss in urine
• small volume of concentrated siren