Introduction to Muscle Tissue

The three types of muscle tissue share the following common characteristics:

  • Contractility – muscles cells shorten to create tension, allowing for movement
  • Excitability – muscle cells can be stimulated (excited) and respond by generating tension
  • Extensibility – muscle cells can stretch beyond resting length without tearing
  • Elasticity – muscle cells can recoil back to their original length after stretching

This chapter will introduce the three types of muscle tissue: skeletal, cardiac, and smooth muscle.

Skeletal Muscle Tissue

Skeletal muscle tissue is responsible for moving our skeleton, supporting our joints, and helping us express emotions through facial expression. Skeletal muscle cells are incredibly long cells, so long that they are referred to as muscle fibers. Skeletal muscle tissue is made of elongated (long) cylindrical-shaped cells. Each cell contains many nuclei, so they are called multinucleated (Figures 1 and 2). The nuclei are peripherally-located, which means they are pushed against the inside of the plasma membrane. Skeletal muscle tissue is striated, a term that refers to its perpendicular “striped” appearance (the sarcomere is cool and we will learn more about it later!).  Contraction of skeletal muscle tissue is under voluntary control, meaning that you have conscious control over your skeletal muscle movements.

Table 1: Skeletal muscle

Tissue Type Skeletal Muscle
General Description Very long cells that are multinucleated and have visible striations
Location Skeletal muscles of the body
Function Move skeleton and support joints
Voluntary or Involuntary? Voluntary
Helpful Hints Look for the striations and multiple nuclei pushed against the cell membrane

Figure 1: Skeletal muscle (longitudinal section) with and without illustration overlay

Figure 2: Skeletal muscle (longitudinal and cross section) with and without illustration overlay

Check out our YouTube video to help you understand skeletal muscle:

YouTube Video – Skeletal Muscle Tissue

We will discuss skeletal muscle in greater detail in a later chapter: Skeletal Muscle Tissue and the Neuromuscular Junction

Cardiac Muscle Tissue

Cardiac muscle tissue is found in our heart, and is responsible for the pumping movement of blood throughout our body. Cardiac muscle cells are branched, and connected to each other through unique connections called intercalated discs, which contain gap junctions and desmosomes (Figures 3 and 4). Typically, cardiac muscle cells have one larger, centrally-located nucleus (uninucleated). Cardiac muscle tissue is also striated, which refers to the perpendicular “striped” appearance. Contraction of cardiac muscle tissue is involuntary, meaning that you cannot consciously control contraction of your heart.

Table 2: Cardiac muscle

Tissue Type Cardiac Muscle
General Description Shorted branched cells with one nuclei and have visible striations, cells connected by intercalated discs
Locations Heart
Functions Pump blood through the body
Voluntary or Involuntary Involuntary
Helpful Hints Look for the striations and the intercalated discs

Figure 3: Cardiac muscle (version A) with and without illustration overlay

Figure 4: Cardiac muscle (version B) with and without illustration overlay

Check out our YouTube video to help you understand cardiac muscle:

YouTube Video – Cardiac Muscle Tissue

Smooth Muscle Tissue

Smooth muscle tissue is found in the walls of our hollow organs: blood vessels, trachea/bronchi, intestines, urinary bladder and ureters, uterus, etc. Contraction of smooth muscle tissue squeezes these hollow organs to decrease the diameter of the inside space. In a blood vessel, smooth muscle contraction causes the blood vessel lumen (inside space) to become more narrow, which can decrease blood flow. In your intestines, smooth muscle contraction causes food to mix, and move through your digestive system. In the urinary bladder, smooth muscle contraction causes urine to flow more quickly.

Smooth muscle cells are smooth, which means they are not striated (Figure 5). Smooth muscle cells are uninucleated, small cells that have tapered ends (imagine a feather pillow, which is bulged in the center and skinny on the ends). Contraction of smooth muscle tissue is involuntary, meaning you cannot consciously control its contraction.

Table 3: Smooth muscle

Tissue Type Smooth Muscle
General Description Short cells with one nuclei and tapered at the ends, no striations
Locations Walls of our hollow organs and blood vessels
Functions Allows for movement of substances such as food and blood through the organs/body
Voluntary or Involuntary? Involuntary
Helpful Hints Students often confuse this tissue with dense regular connective tissue, the smooth muscle will have more nuclei located in the center of the cells

Figure 5: Smooth muscle with and without illustration overlay

Check out our YouTube video to help you understand smooth muscle:

YouTube Video – Smooth Muscle Tissue

Chapter Illustrations By:

Georgios Kallifatidis, Ph.D.

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Anatomy and Physiology I: An Interactive Histology Atlas Copyright © 2024 by Karen Wiles; Christina Wilson; Juan Manuel Ramiro-Diaz; Georgios Kallifatidis; and Soma Mukhopadhyay is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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