Module 3.4 - Oxygen Exchange in Tissue Caps

Question 1

Capillaries are present throughout tissues in roughly ______ distribution

Answer 1

Even

Question 2

How wide are capillaries?

Answer 2

As wide as an RBC (central region of capillary)

Question 3

Krogh cylinder model of the capillary bed

Answer 3

Capillaries lie adjacent and diagnolar from each other, with an area of influence around each of them which is the distance through which O2 can diffuse

Question 4

Rc, Rw and RT

Answer 4

Rc = radius from middle of central region to capillary wall

Rw = radius from middle of central region to outside cap wall

RT = radius from middle of central region to tissue

Question 5

T/F: In the Krogh cylinder model, we assume all capillaries are NOT equidistant from each other to obtain the most accurate expressions

Answer 5

F: Assume equidistance to make math easier. This is an average basis, and an assumption not far off from the real thing

Question 6

Assumptions applied to model flux of O2 from Rc to RT (5)

Answer 6

1. Tissue consumption of O2 follows 0 order kinetics (not dependent on [O2])
2. Axial diffusion is negligible compared to radial diffusion
3. No O2 flux in tissue at RT
4. No O2 consumption by endothelial cells
5. Radial symmetry, so flux is the same in the opposite direction

Question 7

Why is there a curve in the concentration gradient of O2 in the tissue?

Answer 7

Due to parabolic nature and ln shift (functions) of the Krogh model

Question 8

What happens to O2 consumption/release in arteriole and venule end of capillary during exercise?

Answer 8

Art. end consumes more O2 than usual, venous end consumes even less (releases more)