Chapter 23 - Chapter23LectureOutline Introduction

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 23 Lecture Outline Introduction How Does Gravity Affect Blood Circulation? A. Most animals have a circulatory system for the internal transport of gases, nutrients, and waste. B. Gravity has had major effects in shaping the evolution of circulatory systems in terrestrial organisms as different as corn snakes and giraffes. 1. Strong hearts are able to pump against the force of gravity, even in tall animals. 2. Muscles used in normal activities contract around veins and force blood back to the heart through one-way valves. 3. In the corn snake, veins have no valves, but tail vessels constrict during a climb, and a snake will wriggle after a climb to increase circulation. Module 23.1 The circulatory system connects with all body tissues. Review: Chemical exchange between an animal and its environment (Module 20.11). A. Diffusion is inadequate for transporting chemicals over distances greater than a few cell widths. A circulatory system is used to transport material over long distances and bring those needed materials close enough for diffusion to work. B. Capillaries are the smallest vessels and form an intricate network of vessels among the cells of every tissue (Figures 23.1A and 23.12A). C. The various components of blood, particularly red blood cells, come in close enough contact with associated cells that materials can diffuse between them, via the interstitial fluid (Figure 23.1B). D. In most tissues, O 2 and nutrients diffuse from blood to tissue, and CO 2 and metabolic wastes diffuse from tissue to blood. E. The circulatory system also functions in homeostasis by exchanging molecules with the interstitial fluid and by moving the blood through organs such as the liver and kidneys, where the blood’s contents are regulated. I. Mechanisms of Internal Transport Module 23.2 Several types of internal transport have evolved in animals. A. The body plan of the hydra and other cnidarians does not require a circulatory system (Module 21.3). The body wall and gastrovascular cavity are only two to three cells thick; therefore, diffusion can transport molecules directly to the cells. In jellyfish, the gastrovascular cavity is intricately branched, radiating from the mouth to a circular canal (Figure 23.2A). B. Many invertebrates (including arthropods and molluscs) have open circulatory systems. Blood  is pumped by one or more hearts through open-ended vessels and flows out among the cells. There is no separate interstitial fluid. Pores in the hearts function as valves, opening when the hearts relax to pull in blood from the tissues (Figure 23.2B).
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
C. Other invertebrates and all vertebrates have closed circulatory systems (also called a cardiovascular system ). Blood is confined to vessels, which keeps it distinct from the interstitial fluid (Figure 23.2C). D.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/10/2011 for the course BIOL 10 taught by Professor Kite during the Spring '11 term at Laney College.

Page1 / 9

Chapter 23 - Chapter23LectureOutline Introduction

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online