Overview
This lecture covers the characteristics, functions, and subtypes of connective tissues, including connective tissue proper, supportive tissues (cartilage and bone), and fluid connective tissues (blood and lymph).
Characteristics and Functions of Connective Tissue
- Connective tissues consist of fewer cells and a prominent non-living matrix containing protein fibers (collagen, elastic, reticular).
- Matrix consistency varies: liquid (blood), gel (cartilage), or solid (bone).
- Connective tissues bind, support, transport, protect, insulate, and play immune roles.
- Vascularity varies among types; some are vascular, others avascular.
Connective Tissue Proper
- Subdivided into loose (areolar, adipose, reticular) and dense (regular, irregular, elastic) types.
- Loose connective tissues have more matrix and fewer fibers; dense have tightly packed fibers.
- Common cell types: fibroblasts (make fibers), macrophages (clean up debris), mast cells (immune response), lymphocytes (immune cells).
Loose Connective Tissue
- Adipose: Fat storage, insulation, protection, mainly adipocytes, highly vascular, low matrix.
- Areolar (Fascia): Anchors epithelia, stretchy, soaks up fluid (edema), contains all three fiber types, highly vascular.
- Reticular: Fine meshwork, supports immune organs (lymph nodes, spleen, bone marrow), many reticular fibers and immune cells.
Dense Connective Tissue
- Dense Regular: Fibers in one direction, tensile strength (tendons, ligaments), mostly collagen, avascular.
- Dense Irregular: Fibers in multiple directions, found in dermis, strong in many directions, vascular.
- Elastic: Mainly elastic fibers, found in lungs and large arteries, avascular.
Supportive Connective Tissue
Bone (Osseous Tissue)
- Provides support and protection, solid mineralized matrix, mostly collagen fibers.
- Bone cells: osteocytes (mature cells), osteoblasts (build bone), osteoclasts (break down bone).
- Two types: compact (cortical) and spongy (cancellous/trabecular); marrow in spongy bone produces blood cells.
Cartilage
- Gel-like matrix, firm yet flexible; avascular.
- Hyaline Cartilage: Reduces friction at joints, ends of bones, nose, trachea.
- Fibrocartilage: Shock absorber, intervertebral discs, meniscus, pubic symphysis.
- Elastic Cartilage: Stretchy, in ear, epiglottis, eustachian tubes.
Fluid Connective Tissue
Blood
- Liquid matrix (plasma), transports gases, nutrients, wastes, immune function, regulates pH and temp.
- Cells: erythrocytes (RBCs), leukocytes (WBCs), thrombocytes (platelets).
- Fibers present but only form visible mesh when clotting.
Lymph
- Fluid in lymphatic vessels, mostly white blood cells, removes excess tissue fluid, returns it to blood.
- No red blood cells or platelets; dissolved fibers.
Key Terms & Definitions
- Matrix — Non-living material that surrounds cells in connective tissue.
- Collagen fibers — Strong, rope-like protein fibers for strength.
- Elastic fibers — Stretchy, rubber-band-like protein fibers.
- Reticular fibers — Fine, mesh-like protein fibers for filtering and support.
- Fibroblast — Cell that makes protein fibers.
- Adipocyte — Fat cell.
- Osteocyte — Mature bone cell.
- Chondrocyte — Cartilage cell.
- Avascular — Lacking blood vessels.
- Vascular — Contains blood vessels.
- Areolar tissue — Connective tissue that anchors epithelia and absorbs fluid.
- Hyaline cartilage — Smooth, friction-reducing cartilage at joints.
- Erythrocyte — Red blood cell; Leukocyte — White blood cell; Thrombocyte — Platelet.
Action Items / Next Steps
- Create a concept map of connective tissue subtypes and characteristics.
- Review and reorganize notes and charts for understanding.
- Learn and memorize cell and tissue type root words.