Skeletal Muscle Cells Overview

Skeletal Muscle

• Skeletal muscle fibers maintain a constant number throughout life; they do not undergo mitosis due to their structure.
• Individual skeletal muscle fibers can increase or decrease in size but not in number.
• Skeletal muscle cells are long, multinucleated, and organized into bundles surrounded by connective tissue.
• Under light microscopy, skeletal muscle appears striated with peripheral nuclei.

Cardiac Muscle

• Cardiac muscle forms the walls of the heart and consists of cardiomyocytes.
• Cardiomyocytes are smaller than skeletal muscle fibers and contain a single, centrally located nucleus.
• Specialized junctions called intercalated discs connect cardiomyocytes, featuring desmosomes and gap junctions.
• Cardiac muscle is under involuntary control and pumps blood throughout the body.

Smooth Muscle

• Smooth muscle tissue facilitates involuntary movements in internal organs (digestive, urinary, reproductive systems) as well as airways and arteries.
• Smooth muscle cells are football-shaped, possess a single nucleus, and lack visible striations.

Nervous Tissue

• Nervous tissue comprises the brain, spinal cord, and peripheral nerves and exhibits excitability.
• Two primary types of cells in nervous tissue: neurons (signal transmitters) and glial cells (supportive cells).
• Neurons communicate via electrochemical impulses known as action potentials, triggering the release of signaling molecules.

Neuron Structure

• Neurons consist of three main parts:
  • Cell body: Contains organelles and nucleus.
  • Dendrites: Short branches that receive signals from other cells.
  • Axon: A long projection that transmits signals to other cells.

Tissue Membranes

• Membranes may refer to cell membranes or tissue membranes, which are thin sheets of cells that cover various body structures.
• Four types of tissue membranes: mucous, serous, cutaneous, and synovial.

Mucous Membranes

• Composed of connective and epithelial tissues, mucous membranes line cavities and passageways that open to the outside environment, such as the digestive and respiratory tracts.

Serous Membranes

• Serous membranes line internal cavities that do not open to the exterior, secreting serous fluid for lubrication to reduce friction between organs.

Cutaneous Membrane

• The skin is the cutaneous membrane, a stratified squamous epithelium over connective tissue, providing a barrier against environmental factors.

Synovial Membranes

• Synovial membranes are connective tissues that line the cavities of movable joints, releasing synovial fluid for lubrication and nourishment of cartilage.

Inflammation

• Inflammation is the body's initial response to injury, with acute inflammation resolving over time through healing.
• Chronic inflammation can adversely affect homeostasis, with arthritis and tuberculosis as examples.
• The suffix "-itis" indicates inflammation of a specific organ or type.