This chapter focuses on the tissue, organ, and organ system

levels of biological organization (1.3).

You will also get a look at some of the variations on basic

cell structure (3.1–3.9) that occur in your body. The varia-

tions remind us that cells that perform specialized functions

must be built to carry out those tasks.

Key ConCepts

LinKs to earLier ConCepts

Types of Body Tissues

Epithelium, connective tissue, muscle

tissue, and nervous tissue are the

basic types of body tissues.

Sections 4.1–4.7

Top: Ed Reschke/Peter Arnold; Middle: © Cengage Learning; Bottom:

© Jupiterimages

Organs and Organ Systems

Combinations of tissues form

organs. The body’s organ systems

consist of interacting organs.

Sections 4.8–4.9

Homeostasis

A feedback mechanism works to

maintain homeostasis—stable oper-

ating conditions in the body.

Sections 4.10–4.11

Stem cells are the first to form in an embryo and

all of its tissues grow from them. This is why researchers like

Dr. Stephen Minger, below, began looking to embryonic stem

cells for growing replacements for damaged tissues and organs.

Dr. Minger’s research focus is the inherited lung disease cystic

fibrosis. Removing cells from an embryo may seriously harm

or destroy it, however. Far less controversial are the stem cells

present in umbilical cord blood, and in the bone marrow, skin,

and some other tissues of adults. They have shown promise

for regenerating tissues such as cartilage and cardiac muscle

damaged by a heart attack.

Thinking about stem cells turns our focus to the basic types

of cells and tissues that make up the body. Those topics in turn

launch our study of human anatomy and physiology. Anatomy

refers to the body’s parts and how they are put together.

Physiology refers to how body parts function.

67

4 Tissues, Organs, and Organ Systems

organ systeMs

4

homeostasis preview

In this chapter you will learn about a major mechanism of

homeostasis called negative feedback and see how it regulates

internal body temperature.

Volker Steger/Science Source

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