Overview
This lecture covers the major types of connective tissues, their structures, cell types, functions, and introduces muscle and nervous tissue.
General Structure of Connective Tissue
- All connective tissues have ground substance (protein-rich) and fibers (collagen, elastin, reticular).
- The ground substance and fibers together form the extracellular matrix.
- Different proportions of fibers determine tissue structure and function.
- Collagen provides strength, elastic fibers give elasticity, reticular fibers form meshworks.
- Major cell: fibroblast (produces fibers/ground substance); also present: immune cells (lymphocytes, macrophages, neutrophils), mast cells (allergic responses), adipocytes (fat storage/cushioning).
Connective Tissue Proper
- Connective tissue proper divides into loose and dense types.
- Loose connective tissue proper: areolar (cushions, found everywhere), adipose (fat storage, subcutaneous/abdominal), reticular (mesh in lymphoid organs).
- Dense connective tissue proper: regular (parallel collagen in tendons/ligaments), irregular (random collagen in joint capsules, dermis), elastic (elastic fibers in bronchi/arteries).
Cartilage
- Cartilage cells: chondroblasts/chondrocytes in lacunae.
- Hyaline cartilage: most abundant, covers bones at joints, forms embryonic skeleton, ribs, trachea.
- Elastic cartilage: found in ear, epiglottis, some larynx.
- Fibrocartilage: thick collagen, withstands pressure, found in intervertebral discs, knee menisci, pubic symphysis.
Bone and Blood
- Bone: connective tissue with calcified matrix, osteocytes in lacunae, supports, protects, stores minerals, houses marrow.
- Blood: connective tissue with cells in plasma, connects organs by transport.
Muscle Tissue Types
- Skeletal muscle: voluntary, striated, multinucleated, fast contractions.
- Cardiac muscle: involuntary, striated, branched, single nucleus, slow contraction, heart only.
- Smooth muscle: involuntary, non-striated, single nucleus, slow contraction, found in walls of organs/tubes.
Nervous Tissue
- Two main cell types: neurons (signal transmission) and glial cells (support, nourish, protect neurons).
- Found in brain, spinal cord, nerves.
- Neurons have dendrites (receive signals) and axons (send signals).
Key Terms & Definitions
- Fibroblast — main cell producing fibers and ground substance in connective tissue.
- Adipocyte — fat cell, stores energy and provides cushioning.
- Chondroblast/Chondrocyte — cartilage cells producing/maintaining extracellular matrix.
- Osteocyte — bone cell located in lacunae.
- Extracellular Matrix — combination of fibers and ground substance in connective tissue.
- Lacunae — small cavities in cartilage/bone housing cells.
- Areolar Tissue — loose connective tissue cushioning organs.
- Reticular Tissue — connective tissue with meshwork supporting lymphoid organs.
Action Items / Next Steps
- Practice drawing/classifying types of connective tissue and their subtypes.
- Review micrographs of connective tissues to identify features.
- Prepare for next class focusing on epithelial or nervous tissues.
- Keep lecture overview structure for study reference.