Muscle Tissue Types: Cardiac Muscle and Smooth Muscle

Cardiac Muscle

• Description:
  • Consists of branching, striated cells.
  • Cells are generally uninucleate (containing a single central nucleus).
  • Individual cells connect at specialized intercellular junctions known as intercalated discs.
• Function:
  • Propels blood into the vascular circulation through coordinated contractions.
  • Operates under involuntary control.
• Location:
  • Located specifically in the walls of the heart.
• Histological Visual Characteristics:
  • Photomicrograph magnification: $475\times$.
  • Visible structures include distinct striations, branching cell architectures, central nuclei, and dark cross-bands representing intercalated discs.

Smooth Muscle

• Description:
  • Cells are characteristically spindle-shaped, tapering at both ends.
  • Cells possess central nuclei.
  • Lacks visible striations.
  • Cells are arranged tightly together to form contiguous sheets.
• Function:
  • Propels substances or objects along internal passageways.
  • Examples of propelled items include foodstuffs, urine, and a baby.
  • Operates under involuntary control.
• Location:
  • Found mostly in the walls of hollow internal organs.
• Histological Visual Characteristics:
  • Photomicrograph magnification: $465\times$.
  • Sample source: Sheet of smooth muscle tissue from the digestive tract.
  • Visible structures include individual smooth muscle cells and elongated central nuclei.

Histology Study Resources and Figure Reference

• Figure Reference:
  • Figure 4.12 (continued) — Tissue: The Living Fabric (Chapter 4, Page 139).
• Practice Resources:
  • Practice Histology questions can be accessed via: MasteringA&P > Study Area > Lab Tools > PAL.