Tissues and Membranes - 006

Major Tissue Types

  • Epithelial Tissue: Covers outer body surfaces, lines inner cavities, forms skin, and forms glands.

  • Connective Tissue: Supports, binds, and protects body structures; found in blood, bone, cartilage, and other tissues.

  • Nervous Tissue: Forms the brain, spinal cord, and nerves; conducts electrical signals and supports neural function.

  • Muscle Tissue: Composed of fibers that shorten to move body parts.

Epithelial Tissue

  • General Characteristics:

    • Forms continuous sheets with an unattached outer surface and an undersurface attached to a basement membrane.

    • Avascular; relies on underlying connective tissue for nourishment.

  • Functions: Protection, absorption, filtration, secretion, and transportation.

  • Classification by Cell Shape:

    • Squamous: Thin and flat (resembles fish scales).

    • Cuboidal: Cube-shaped (resembles dice).

    • Columnar: Tall and narrow (resembles columns).

  • Classification by Layers:

    • Simple: Single layer; enables rapid movement via diffusion or filtration.

    • Stratified: Multilayered; protects against everyday wear and tear.

    • Transitional: Multilayered structure where cells slide past one another to allow stretching.

    • Pseudostratified Columnar: Single layer appearing stratified; lines respiratory airways.

    • Glandular: Composed of cells specialized for secretion; divided into exocrine and endocrine glands.

Cell shapes and layer types in epithelial tissueTypes and locations of epithelial tissue in the human body

  • Specific Tissue Locations:

    • Simple Squamous: Air sacs in lungs

    • Simple Cuboidal: Ovary surface

    • Simple Columnar: Digestive tract

    • Stratified Squ amous: Mouth and skin

    • Pseudostratified Columnar: Respiratory airways

    • Transitional: Bladder

Connective Tissue

  • Locations: Found in blood, under skin, in bone, and surrounding organs.

  • Characteristics:

    • Most connective tissue features a rich blood supply and an abundant intercellular matrix.

    • Cartilage, tendons, and ligaments have a poor blood supply.

  • Types:

    • Loose connective tissue

    • Dense fibrous connective tissue

    • Cartilage

    • Bone

    • Blood and lymph

Nervous Tissuedv s

  • Location: Brain, spinal cord, and nerves.

  • Cell Types:

    • Neurons: Cells that transmit electrical signals between the brain and spinal cord. Composed of:

    • Dendrites: Receive signals.

    • Cell body: Contains main metabolic machinery.

    • Axon: Transmits electrical impulses away from cell body.

    • Neuroglia (Glia): Non-conductive cells that support, protect, and care for neurons.

Diagram of a neuron showing dendrites, cell body, and axonDiagram of neuroglia supporting neurons

Muscle Tissue

  • Structure: Made of specialized cells called fibers that contract/shorten to generate movement.

  • Types:

    • Skeletal: Voluntary muscle attached to skeleton.

    • Smooth: Involuntary muscle located in internal organ walls.

    • Cardiac: Involuntary muscle composing heart walls.

Tissue Repair

  • Regeneration: Replacement of damaged tissue with identical cells.

  • Fibrosis: Replacement of damaged tissue with fibrous connective tissue, forming scar tissue.

Steps in tissue repair process

Tissue Membranes

  • Epithelial Membranes:

    • Cutaneous: Skin; covers exterior body surface.

    • Mucous: Lines body cavities/passageways opening directly to the exterior.

    • Serous: Lines closed internal body cavities.

  • Connective Tissue Membranes:

    • Layers formed entirely from connective tissue.

    • Function to encapsulate organs, protect the central nervous system, and line moveable joints.