Cells and tissues pt 2

Cell Function and Membrane Structure

• Cell Membrane Overview

  • Composed of a double layer of phospholipids.

  • Phospholipid Structure

    • Fatty tails on the inside (hydrophobic).

    • Charged heads on the outside (hydrophilic).

• Substance Movement

  • Diffusion: Movement from high concentration to low concentration without energy.

    • Example: Oxygen can easily move through cell membrane due to size.

    • Simple Diffusion: Molecules like CO2 moving out of the cell.

  • Facilitated Diffusion: Required for larger molecules to pass through.

    • Utilizes special passages without using energy.

  • Osmosis: Movement of water through aquaporins.

    • Water moves from high concentration of water (low solutes) to low concentration of water (high solutes).

• Active Transport

  • Requires energy to move substances against the concentration gradient.

  • Example: Nerve cells need energy (ATP) to transport substances out against the gradient.

• Exocytosis and Endocytosis: Mechanisms to get rid of or take in large substances.

Tissue Types Overview

• Tissues: Groups of similar cells performing similar functions.

• Four primary types: Epithelial, Connective, Muscle, Nervous.

Epithelial Tissue

• General Characteristics

  • Lines surfaces and cavities, covering both internal and external surfaces.

  • Avascular (no blood supply), relies on adjacent connective tissue for nutrients.

• Function: Protect, absorb, filter, and secrete.

• Classifications: Based on layering and cell shape.

  • Layers:

    • Simple (one layer).

    • Stratified (multiple layers).

    • Pseudostratified (looks layered but isn’t).

  • Shapes:

    • Squamous (flat).

    • Cuboidal (cube-like).

    • Columnar (tall).

• Examples:

  • Simple Squamous Epithelium: Found in alveoli and blood vessels; facilitates diffusion.

  • Stratified Squamous Epithelium: Found in skin and esophagus; provides protection.

  • Simple Cuboidal Epithelium: Found in glands like salivary glands.

  • Columnar Epithelium: Lines the digestive tract; contains mucus-secreting cells.

• Glandular Epithelium: Forms glands to secrete hormones and other substances.

  • Types:

    • Endocrine: Secretes directly into the bloodstream (e.g., thyroid).

    • Exocrine: Secretes into ducts (e.g., sweat glands).

Connective Tissue

• Definition: Composed of cells and intercellular material (matrix), can be solid or liquid.

• Functions: Binds tissues, supports, provides protection.

• Types of Connective Tissue:

  • Dense Connective Tissue: Includes tendons (muscle to bone) and ligaments (bone to bone).

  • Cartilage: Connective tissue found in joints, trachea, and ear; provides flexible support.

  • Bone: A type of dense connective tissue, providing structural support.

  • Adipose Tissue: Stores fat, provides insulation and padding.

  • Blood: Considered a connective tissue, serves to transport nutrients and waste.

Muscle Tissue

• Types of Muscle Tissue:

  • Skeletal Muscle: Striated, voluntary control; involved in movement.

  • Cardiac Muscle: Striated, involuntary control; makes up the heart.

  • Smooth Muscle: Non-striated, involuntary; found in walls of hollow organs such as the digestive tract.

• Muscle Functions: Movement, contraction, support and control of organ systems.

Nervous Tissue

• Composition: Neurons and glial cells; responsible for signaling within the body.

• Functions: Transmits signals for coordination and response from stimuli.