Chapter 7. Muscle Tissue

A. Introduction and Overview

Page 1

Muscle tissue is designed to create mechanical tension and, through the development of tension, movement. Somatically, muscle tissue is generally responsible for moving bones and other elements of the soma, such as the eyes. Viscerally, muscle is responsible for the contraction of the heart and the movements of the walls of hollow tubular organs, such as the digestive tract, blood vessels, and the bladder. In this lab session, we will microscopically study the three major types of muscle tissue: skeletal muscle, cardiac muscle and smooth muscle.

Histologically, muscle tissue is classified into two major groups: striated muscle and nonstriated (smooth) muscle. This classification scheme is based solely on the presence or absence of microscopic striations in the muscle cells; striated muscle tissue has alternating light and dark striations, nonstriated muscle does not.

Striated Muscle

Image:

Striated Muscle Tissue: Striated muscle tissue has alternating light and dark striations that run perpendicular to the long axis of the cells. The animal body has two basic types of striated muscle: skeletal muscle and cardiac muscle. Skeletal muscle is the muscle tissue of the body's soma. Its principle attachment site is bone, and it is primarily responsible for the movement and posture of the skeleton. Skeletal muscle also has a very limited distribution in viscera; it is found in the walls of the upper part of the digestive tract (pharynx, tongue, upper esophagus). Cardiac muscle is found only in the wall of the heart.

Smooth Muscle

Image:

Nonstriated Muscle: Nonstriated muscle tissue lacks the alternating light and dark striations found in striated muscle. Smooth muscle is distributed widely among tubular visceral organs, such as the digestive tract, blood vessels, internal genitalia and associated reproductive structure, the urinary bladder, etc.