1. Cells
2. Ground substance
3. Extracellular Matrix (ECM)

• Most common cell in conn tiss
• Function: synthesize fibers and ground substance
• active: fibroblasts
• inactive: fibrocytes (shrivel up)
• wound healing: myofibroblasts

• One large fat droplet (WHITE fat)
• Organelles pushed to periphery of cell
• Major enery source - triglycerides
• Highly vascularized (hypertension in obese patients)

• Many lipid droplets floating in cell (BROWN fat)
• central nuclei
• Rich in mitochondria
• Brown appearance from cytochrome oxidase
• Function: heat production (strategic placement in neonates)

• Histiocytes: macrophage formed in conn tiss
• Function: phagocytosis of antigens through presentation of Ag on MHC to T-Cells
• Langhans cell: Mac will combine with 100s of other Macs to form multinucleate L cell if very large antigen
• Stain with immunohistochemistry because of acid phosphatase

• Contains cytoplasmic granules (vasoactive mediators)
• Histamine - vasodilation
• Heparin - anticoagulant
• Chemotactic mediators - attract other lymphocytes
• Leukotrienes released from cell membrane - vasoactive
• Never present in CNS because causes edema

Exhibited uniquely by Mast Cells

Stain with toluidine blue and turns purple red instead

• Very small, minimal cytoplasm
• B & T-cells

• Developed from B-cells
• once activated secretes only ONE class of immunoglobin
• signature clockface nucleus

• Eosinophilic - stains PINK with H&E
• Function: phagocytosis of Ab-Ag complexes (can kill parasitic worms)
• Signature disk-like granulocyte in cytoplasm

Type I Collagen

Eosinophilic

Banded fibers

Type III Collagen

Short thin and branching

Acts like a scaffold to accomodate volume changes

Argyrophilic and PAS+

Fibrillin & Elastin

Stain specially with elastic stain (Orcein)

• Procollagen assembled inside cell (RER-Golgi)
• Hydryoxylysine and cofactor Ascorbate (Vit C) required to hydroxylate lysine and proline
• Transported outside cell to "cove" and assembled into organized banded fibers

• Proelastin assembled internally
• Microfibril associated externally and creates elastic fibers - randomly arranged
• w/o M, forms in sheets (lamina) instead

1. Glue - binds cells to fibers
2. Lubricant - ease of motion (cell migration)
3. Barrier - physical prevention of bact and microorg
4. Tissue tensile strength