Overview
This lecture covers the four main types of human tissues—epithelial, connective, muscular, and nervous—explaining their structures, functions, and significance in the body.
Introduction to Tissues
- Tissues are groups of connected cells working together to perform specific functions.
- There are four main tissue types: epithelial, connective, muscle, and nervous.
- The structure and type of tissue determines its function within organs and organ systems.
Epithelial Tissue
- Epithelial tissue lines inner and outer body surfaces, forming coverings and linings like skin and digestive tract.
- Functions include protection, secretion (e.g., hormones, mucus), and absorption (e.g., nutrients).
- Characterized by a free surface (exposed) and a basement membrane (anchoring layer).
- Classified by cell shape: squamous (flat), cuboidal (cube-shaped), columnar (tall).
- Classified by layering: simple (single layer), stratified (multiple layers), pseudostratified, and transitional (stretchable).
- Histology is the study of the microscopic structure of tissues.
Connective Tissue
- Connective tissue supports and binds other tissues and organs.
- Made of living cells in a non-living extracellular matrix (can be solid, liquid, or fibrous).
- Types:
- Fibrous (flexible matrix of protein fibers; forms tendons, ligaments, membranes).
- Supportive (solid matrix; includes bone and cartilage).
- Fluid (liquid matrix; includes blood and lymph).
Fibrous Connective Tissue
- Loose fibrous tissue is flexible and surrounds blood vessels/organs, storing fat (adipose) or forming lymph organs (reticular).
- Dense fibrous tissue provides strong support in tendons and ligaments.
Supportive Connective Tissue
- Cartilage: strong but flexible tissue formed by chondrocytes, found in joints, nose, ears.
- Bone: rigid, strong tissue formed by osteocytes, provides structural support and houses marrow.
Fluid Connective Tissue
- Blood: contains red blood cells (oxygen transport), white blood cells (immunity), and platelets (clotting).
- Lymph: fluid with white blood cells, involved in immune response.
Muscular Tissue
- Muscle tissue contracts to enable body movement and organ function.
- Types:
- Skeletal (voluntary movement, striated, multinucleated).
- Smooth (involuntary, non-striated, single nucleus, lines hollow organs, moves substances via peristalsis).
- Cardiac (involuntary, striated, single nucleus, found only in the heart, contains intercalated discs for synchronized contraction).
Nervous Tissue
- Nervous tissue conducts nerve impulses for communication and control.
- Made of neurons (signal transmission) and neuroglia (support and maintenance).
- Neuron structure: dendrites (receive signals), cell body, axon (transmits signals), myelin sheath (insulation), axon terminals.
Key Terms & Definitions
- Tissue — Group of similar cells plus extracellular matrix performing a specific function.
- Epithelial tissue — Linings/coverings of body surfaces and organs; shapes: squamous, cuboidal, columnar.
- Histology — Study of microscopic anatomy of tissues.
- Connective tissue — Supports, connects or separates tissues/organs; includes bone, blood, cartilage.
- Extracellular matrix — Non-cellular material separating connective tissue cells.
- Fibroblast — Cell that produces connective tissue fibers.
- Osteocyte — Mature bone cell embedded in bone matrix.
- Chondrocyte — Cell that produces cartilage matrix.
- Lacunae — Small spaces housing osteocytes/chondrocytes.
- Muscular tissue — Tissue specialized for contraction and movement.
- Peristalsis — Wave-like muscle contractions in digestive tract and other tubes.
- Intercalated discs — Junctions between cardiac muscle cells for communication.
- Nervous tissue — Specialized for electrical impulse conduction; includes neurons and neuroglia.
Action Items / Next Steps
- Review examples of each tissue type in the body.
- Practice identifying tissue types by shape and layering.
- Answer review questions about tissue functions, locations, and special cell types.