Module 8 Intro
1. Module 8 Intro
1.27. Page 3
Module 8—Circulation, Immunity, and Excretion
Watch and Listen
Fluid Exchange Across the Walls of Capillaries
You may want to read “Circulation and the Action of Capillaries” on pages 287 and 288 of the textbook and study “Figure 8.22” before you watch this animation.
Self-Check
SC 1. How would serious bleeding affect the movement of fluids in and out of the capilliary?
SC 2. Why does blood not flow constantly through the billion capillaries in your body?
SC 3. Where does the diffusion of materials take place in a capillary?
SC 4. Why is blood flow slower through capillaries?
SC 5. What determines the direction of diffusion?
SC 6. Based on what you know about the movement of fluids and materials, hypothesize why a child who has a lack of nutritious food will have a distended abdomen.
Self-Check Answers
SC 1. Bleeding would reduce the pressure and concentration gradients. Therefore, the diffusion of essential nutrients and gases would be inhibited. Cells would not exchange materials and then cease to function properly, leading to shock.
SC 2. Blood does not constantly flow to all capillaries because cells may not need to be serviced or blood may be needed elsewhere. For example, capillaries of the digestive system are open after you have eaten, but they are closed to certain muscle cells.
SC 3. The diffusion of materials takes place along the mid-section of a capillary.
SC 4. Blood flow is slower through capillaries to allow diffusion to take place.
SC 5. The direction of diffusion is determined by concentration and pressure gradients.
SC 6. A child lacking proper nutrition will have a distended abdomen because fluid has moved from high concentrations to low concentrations. Because there are no/few nutrients in the blood plasma of the capilliaries in the digestive system, the relative concentration of fluid is high. Fluid will leave the blood, causing tissues to swell.
Try This
TR 1. Capillary Fluid Exchange
You will now apply your knowledge of the capillary fluid exchange model to three new circumstances. In each situation the hydrostatic pressure or the osmotic pressure have changed from their normal levels. Decide what the net movement of the water will be, either outward or inward. Create a diagram or sketched summary of each situation.
Your illustration should start at the capillary level, with the hydrostatic pressures, osmotic pressures, and net movement of water represented by arrows. Each situation will present you with one question. Be sure to answer each question by describing the physiological changes that would occur in an individual with each of the three conditions as a result of this net movement of water.
Go to your Module 8: Lesson 4 Assignment to complete this activity.