Unit D

Module 9 ~ Lesson 3

Muscle Tissue

There are three types of muscles in your body: striated, non-striated, and cardiac. Food moves through intestines and blood moves through blood vessels via the contractions of smooth or non-striated muscle. The heart, a continually working muscle, beats because of specialized cardiac muscle. Muscles that facilitate movement, like your biceps or abdominals, are skeletal or striated muscles.

One of the major differences between smooth (or non-striated muscles) and cardiac or striated (skeletal) muscles is how they contract. Smooth muscles are said to constrict or dilate, while cardiac and striated (skeletal) muscles contract (shorten) or relax (lengthen). Constriction and dilation are still contractions, but of hollow organs such as your intestines.

Striated Muscle. Nephron / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)


Smooth Muscle. Alexander G. Cheroske / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)



Read the introduction, "Movement and Muscle Tissue" and "The Cooperation of Skeletal Muscles" on pages 330 and 333 of your textbook.

et al, Inquiry into Biology (Toronto: McGraw-Hill Ryerson, 2007), p. 335. Reproduced by permission.

Muscle Function and Structure

Whatever the type and function, all muscle tissues are specialized so that they are capable of shortening and producing a motion. In addition, because of the sizable energy requirement for muscle contraction, a significant amount of heat is released during this process. As a result of these two characteristics—the ability to contract and generate heat as a by-product of their metabolism—muscles serve a number of functions. These functions include

    support and movement
  • the propulsion of blood through vessels
  • the movement of food or body secretions through tracts
  • thermoregulation, or the ability to regulate body temperature
If examined closely with a microscope, muscle would display groups of 
muscle fibre bundles. These bundles are clustered further and wrapped in a layer of connective tissue and supplied with nerves and blood vessels. Muscles cells have specialized contractile proteins: actin and myosin.