Anatomical Membranes Overview

Anatomical Membranes

• Sheets of flexible tissue covering or lining body portions, not biological or plasma membranes.
• Typically composed of an epithelial layer plus connective tissue.
• Types include mucous membranes, serous membranes, cutaneous membranes (skin), and synovial membranes (only connective tissue).

Mucous Membranes

• Epithelial layer varies; connective layer named lamina propria, made of areolar connective tissue.
• Lines body cavities open to the external environment, preventing fluid loss.
• Protect from external invaders and secrete enzymes aiding in digestion and absorption.
• Found in the digestive, respiratory, reproductive, and urinary tracts.

Serous Membranes

• Line cavities and organs not exposed to the environment.
• Comprised of areolar connective tissue covered by mesothelium.
• Mesothelium secretes serous fluid to lubricate organs and walls.
• Familiarity with specific serous membranes discussed in lecture.

Cutaneous Membranes

• Consist of skin; most superficial layer is the epidermis.
• Deep to the epidermis lies the dermis.
• Epidermis consists of keratinized stratified squamous epithelium.
• Dermis comprises dense irregular and areolar connective tissues.

Synovial Membranes

• Feature a unique "uncooked egg" appearance.
• Composed of layers of synoviocytes that secrete synovial fluid for joint lubrication and tissue nourishment.
• Beneath synoviocytes are layers of areolar and adipose connective tissues.

Summary of Anatomical Membranes

• Mucous membranes protect open body cavities from injury and fluid loss.
• Serous membranes lubricate internal body cavities and organs.
• Cutaneous membranes (skin) offer abrasion protection.
• Synovial membranes primarily lubricate joints and nourish cartilage.

Muscular and Nervous Tissues

• Contain excitable cells that detect stimuli and generate action potentials.
• Responses may lead to nerve impulses or neurotransmitter release.

Muscular Tissue

• Composed of muscle fibers (myocytes) that contract to move bones and generate heat.
• Three main types: skeletal, cardiac, and smooth.

Skeletal Muscle Tissue

• Long, multinucleate, striated fibers generating voluntary movement, maintaining posture, and producing heat.
• Attaches to bones via tendons.

Cardiac Muscle Tissue

• Features branched, striated fibers with a single nucleus.
• Cells connected through gap junctions for rapid electrical signal conduction.
• Functions under involuntary control, forming the myocardium (heart wall).

Smooth Muscle Tissue

• Composed of long, non-striated fibers with a single nucleus, featuring thickened middle regions.
• Cells form gap junctions to facilitate involuntary muscle contractions.
• Functions in peristalsis, constriction of airways, and contracting urinary bladder/gallbladder.

Nervous Tissue

• Comprised of two cell types:
  • Neurons: generate electrical signals/nerve impulses, consisting of a cell body, dendrites, and axon.
  • Neuroglia: support cells that do not generate electrical impulses; synthesize myelin to increase electrical transmission speed.

Summary

• Tissues consist of cells and extracellular matrix (ECM).
• Epithelial tissues cover and line surfaces, capable of secretion and nutrient absorption, and protection from injuries.
• Connective tissues link epithelial tissues to deeper tissues and provide structural support.
• Muscular tissue facilitates body movement and heat generation.
• Nervous tissue coordinates and regulates responses to stimuli.