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You are reading an older version of this FlexBook® textbook: Human Biology Circulation Teacher's Guide Go to the latest version.

Key Ideas

  • Capillaries are thin and permeable blood vessels that allow for the exchange of nutrients, gases, and waste.
  • This exchange of nutrients, gases, and waste occurs through the process of diffusion.
  • The capillary network is extensive. No cell is more than two cells away from a capillary.


Students explored the structure and function of arteries and arterioles in Section 3. In this section they make a model of a capillary bed. Diffusion is extremely important to the function of capillary beds. Students explore how capillaries and capillary beds work-how the thin walls of the capillaries, the slow movement of the blood, and the process of diffusion allow gases, food nutrients, water, and wastes to pass back and forth between body cells and the bloodstream.



Undefined control sequence \checkmark make a model of a capillary bed.

Undefined control sequence \checkmark describe the characteristics of capillaries which allow for exchange of gases, nutrients, water, and wastes between body cells and the bloodstream.

Undefined control sequence \checkmark design an activity to illustrate the process of diffusion.


capillaries, diffusion, venule

Student Materials

Activity 4-1: Making a Capillary Bed Model

Activity Report

Construction or drawing paper; Scissors; Glue or clear tape; Marking pens; Materials to represent arteries, veins, capillaries and cells (Examples: string, yarn, thread, rope, and dried beans.)

Teacher Materials

Activity 4-1: Making a Capillary Bed Model

  • Activity Report Answer Key
  • Photos of capillaries
  • Diagrams or a model of the circulatory system

Advance Preparation

See Activity 4-1 in the Student Edition,

Display the models students constructed in Activity 1-1.

Check your local audiovisual service and the resource list included in this unit to select visuals of capillary circulation.

Gather materials students will use in constructing their models, such as rope, yarn, string, and thread.

Interdisciplinary Connections

Physical Education/Sports Capillary function is disrupted by bruised, broken capillaries. Students can investigate methods for applying first aid to bruises caused by sports injuries.

Social Studies Sickle-shaped red blood cells block capillaries, which slows blood flow and reduces the oxygen supply. The gene for sickle-cell anemia is more common in geographic areas where malaria is endemic. Students can investigate the geographic distribution of sickle-cell anemia its cause, the reasons for its prevalence in areas with malaria, and in Math, the statistical frequency of sickle-cell anemia, as well as its financial impact.

Enrichment Activities

Enrichment 4-1: Observing Goldfish Capillaries

Enrichment 4-2: Transport of Materials Exploring Diffusion

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