Overview
This lecture covers the structure, functions, classification, and cellular/matrix components of connective tissue, highlighting its diversity and key examples.
Functions of Connective Tissue
- Provides structural framework (e.g., bone, cartilage shape the body).
- Transports substances (e.g., blood carries materials throughout the body).
- Offers protection (bones and cartilage shield organs; immune cells fight infections).
- Supports, surrounds, and connects other tissues (e.g., tendons, ligaments).
- Insulates and stores energy (mainly through adipose/fat tissue).
General Characteristics
- All connective tissues originate from mesenchyme, an embryonic tissue.
- Each connective tissue includes specialized cells and a matrix.
- The matrix consists of ground substance and protein fibers.
- Cells are usually not tightly packed; matrix fills the space between.
Specialized Connective Tissue Cells
- Chondrocytes — cartilage cells.
- Osteocytes — bone cells.
- Adipocytes — fat (adipose tissue) cells.
- Lymphocytes — immune cells in lymph.
- Erythrocytes — red blood cells.
- Leukocytes — white blood cells.
- Platelets/Thrombocytes — aid blood clotting.
- Macrophages — phagocytic immune cells.
- Mast cells — immune cells producing histamine for inflammation.
- Fibroblasts — create fibers; Fibrocytes maintain fibers.
Matrix Components
- Ground substance can be fluid, gel, or solid.
- Major protein fibers:
- Collagen fibers — strong, thick, resist tension.
- Elastic fibers — stretch and recoil; found in tissues needing flexibility.
- Reticular fibers — thin, net-like, support organs.
Types of Connective Tissue
Connective Tissue Proper
-
Loose (Areolar, Adipose, Reticular):
- Areolar: cushioning, immune defense, binds skin layers.
- Adipose: stores fat, insulates, cushions organs.
- Reticular: supports blood cell-rich organs (liver, spleen, lymph nodes).
-
Dense (Regular, Irregular, Elastic):
- Dense regular: parallel fibers, strong in one direction (tendons, ligaments).
- Dense irregular: fibers in many directions, withstands multi-directional stress (dermis).
- Elastic: abundant elastic fibers, permits stretch (large arteries, vertebrae connections).
Fluid Connective Tissue
- Blood: transports, immune function, clotting (cells in plasma).
- Lymph: fluid balance, immunity, returns leaked fluids to blood.
Supporting Connective Tissue
- Cartilage:
- Hyaline: stiff, some flexibility; nose, trachea, rib ends.
- Elastic: very flexible; external ear, epiglottis.
- Fibrocartilage: resists compression; intervertebral discs, pubic symphysis, menisci.
- Bone: rigid, stores minerals, supports/protects organs, formed of compact (osteons) and spongy (trabeculae) structures.
Key Terms & Definitions
- Mesenchyme — embryonic connective tissue origin.
- Matrix — space-filling material of ground substance and fibers.
- Lacuna(e) — small spaces housing cells in cartilage and bone.
- Osteon — structural unit of compact bone.
- Trabeculae — branching networks in spongy bone.
Action Items / Next Steps
- Review lab slides to identify connective tissue types and structures.
- Prepare for next lecture on muscle and nervous tissue.