Chapter 20, Lesson 3: Capillaries and Fluid Exchange

Flashcards from Chapter 20, Lesson 3 of McGraw Hill Anatomy and Physiology, Tenth Edition, by Kenneth S. Saladin.

Capillary exchange

The two-way movement of fluid across capillary walls between the blood and tissues; done through either:

• diffusion

• transcytosis

• filtration

• reabsorption

Diffusion

The most important form of capillary exchange

• Glucose and oxygen diffuse out and carbon dioxide and wastes diffuse in the blood

Capillary diffusion requirements

The membrane must be permeable to the solute or passages must be available to pass through

• lipid-soluble substances can diffuse through membranes

• water-soluble membranes must go through pores

• larger particles are held back

Transcytosis

Vesicle-mediated transport via endo- and exo-cytosis across the capillary wall; very small fraction of solute exchange but crucial for fatty acids, albumin, and hormones like insulin

Filtration and reabsorption

Fluid filters out of arterial end of capillary and osmotically enters venous end in reabsorption, delivering cell materials while removing wastes; can vary like in kidneys (more filtration) vs lungs (more absorption to avoid fluids)

Edema

The accumulation of excess fluid in a tissue; fluid filters in faster than it is reabsorbed and can causae tissue death, suffocation, headaches, or circulatory shock