Connective Tissue, Specialized Tissue and Repair Biology 2121 Chapter 4

Characteristics of Connective Tissue General Characteristics Less cellular; nonliving part Vascular (exception is cartilage) Innervated Functions Protection and insulation (organs) Binds tissues – ligaments Transports vital substances (blood) Stored energy source (adipose tissue) Supports epithelial tissue Stem Cell – Mesenchyme All CT cells originate

CT Stem Cell Stem Cell – Mesenchyme All CT cells originate from this embryonic stem cell Each type of CT has a specific ‘main’ cell type Secretes the matrix Maintains the tissue

General Characteristics - Structure Less Cells- More Matrix Refers to the “non-cellular” part of connective tissue Fibers, water, organic molecules, acid 3. Other cell types May or may not be present Mast cells; macrophages; adipose cells; plasma cells

The Matrix Composed of ‘ground substance’ and ‘fibers’ Between cells and fibers Water Organic molecules – ‘Glycosaminoglycans’ (GAG’s) Protein core (proteoglycans) with GAGs attached Chondroitin sulfate; keratan sulfate; Hyaluraonic acid 2. Function of the Ground Substance Water storage; binds and supports cells; tissue development

Fibers 3. Fibers (a). Collagen – found in bone, cartilage, tendons, ligaments Fibrous Protein (b). Elastic – ‘elastin’ protein; stretch and contract; found in skin, BVs, lung tissue (c). Reticular – fine collagen bundles; thin; support spleen and lymph structures; forms part of basement membrane

Classification of Connective Tissue Connective Tissue Proper Main Cell Type: Fibroblasts Characteristics Examples – Loose CT 1. Areolar CT 2. Adipose 3. Reticular CT Dense CT 1. Regular Dense CT 2. Irregular Dense CT

Dense CT Dense CT 1. Regular Dense CT 2. Irregular Dense CT

Classification of Connective Tissue 2. Cartilage Main Cell Type: Chondrocytes Characteristics Examples: 1. Hyaline 2. Elastic 3. Fibrocartilage

Classification of Connective Tissue 3. Osseous Tissue Main Cell Type: Osteocytes Characteristics Example: 1. Compact Bone 2. Spongy Bone 4. Blood Cells: Erythrocytes, Leukocytes; Platelets Why is blood considered a connective tissue? Plasma

Specialized Tissue - Membranes Parts of the body are covered by ‘membranes’ which are composed of several different types of tissue Connective Tissue bound to Epithelial Tissue Examples: 1. Cutaneous membranes 2. Mucous membranes 3. Serous membranes

Specialized Tissue - Membranes Cutaneous Stratified squamous (keratin) + Dense Irregular CT “Dry Membrane” ; Skin Mucous Stratified squamous/simple columnar + Loose CT Moist; Lines body cavity; digestive and respiratory Serous Simple squamous + areolar loose CT Referred to as ‘mesothelia’ ‘closed’ ventral cavities Serous fluid (anti-frictional) Examples: Pleura, Pericardium, Peritoneum

Injury and Repair of Tissue Ability to Repair 1. Epithelium, bone, CT proper, dense irregular, blood regenerates well 2. Smooth muscle and dense regular regenerate moderately well 3. Skeletal muscle and cartilage repair but poorly 4. Cardiac and nervous tissue (none) Fibrous scar tissue Depends on: Supporting CT ability produce new cells Functioning organ and tissue ability to produce new cells

Tissue Repair Begins with Inflammation Granulation Fibrosis Capillaries dilate; tissue inflamed Dying cells/tissue release chemicals WBCs, macrophages, platelets enter Granulation New collagen develops; BVs branch to all parts of injured tissue Connective tissue grows – ‘granulation tissue’ across the wound SCAB and Tissue Regeneration Fibrosis