Connective Tissue - Most abundant in the human body. - Embryonic is mesenchyme, not yet specialized -Four general types of tissue: Connective tissue proper,

Connective Tissue

- Most abundant in the human body.- Embryonic is mesenchyme, not yet specialized-Four general types of tissue: Connective tissue proper, cartilage, osseous, vascular1. Connective tissue proper – fluid

intercellular material and fibroblasts as the most abundant cell type (fibers, syrupy ground substance and cells. (Four types)

a. Loose areolar tissue – indicates many air spaces, widespread (mucous membranes, around blood vessels and nerves: subcutaneous)Composed of a variety of fibers, cells, and hyaluronic acid as intercellular material.

i. Fibers

Collagenous (white) -

Tough, resistant to pulling, made of collagen

Elastic (yellow) -

Smaller, provides strength (skin, blood vessels, lungs)Reticular -Thin, immature collagen

fibers, coated with glycoprotein, supports the walls of blood vessels, nerve cells, smooth, framework of spleen and lymph nodes – prevents collapse, yet flexible

ii. Cells *Fibroblasts – repair cells, responsible for constantly replacing damaged cells. AGING – when repair cannot keep up with damage*Macrophages – large, function to engulf bacteria and cellular debris by phagocytosis. (Security guards – survey and destroy, cannot take care of all invaders)

*Plasma Cells – blood, lymphatic system, provide immunity by secreting antibodies

*Melanocytes – pigmented cells below the deepest layer of skin, produce melanin (pigment that protects against sun damage) We all have about the same #, but some are large and produce more melanin, freckles, moles

*Mast Cells – produce heparin (anticoagulant) and histamine (dilates small blood vessels during inflammation/allergic reaction – give antihistamines so vessels do not dilate)

b. Adipose Tissue -Composed of adipocytes (look like cobblestones or signet ring in shape)

– fat storage which is necessary for hormone production, energy reserve, insulation, protects internal organs

- Subcutaneous in location

c. Dense (collagenous) tissue – more numerous cells and thicker fibers, closely packed, decreased intercellular substance*Located in muscle (stretch), ligaments (stability), tendons (somewhere between – Achilles’ )

d. Elastic tissue – little different from above, freely branching fibers, stretch and snap back like a rubber band, allows for elasticity*Located in muscles, ligaments and tendons

2. Cartilage “soft bone”-No blood vessels or nerves except in the perichondrium (tissue around the cartilage) if damaged, doctors will go in and fix because it doesn’t repair well on its own. OSTEOARTHRITIS – excessive damage to

the cartilage, calcifies

a. Characteristics:

Dense network of collagen and chondroitin sulfate, resilient and strong

b. Three types*hyaline – (gristle) bluish-white in color, shiny, most abundant type, embryonic skeleton is exclusively composed of , clavicle is the only completely formed bone at birth – WHY?

*fibrocartilage – found in the matirx of bone to give strength and stability, bundle of collagen fibers, between vertebrae*elastic – threadlike network for flexibility

3. Osseous tissue (bone) – skeletal systemBasic unit is the OSTEON,

composed of:a. Lamellae – concentric rings of hard matrix (calcium)b. Lacunae – spaces between lamellae, have Haversian canals which contain nerves and blood vessels

4. Vascular tissue (blood) a. Plasma – mostly water with dissolved substances such as nutrients, wastes, enzymes, hormones, respiratory gases ( O2, CO2)b. Cells, etc.*Erythrocytes - RBCs

*Leucocytes – WBCs – phagocytosis, immunity, allergic reactions. High leucocyte # = infection, leukemia (radiate to destroy bone marrow, replace)*Platelets - clotting

Other Tissues1. Muscle – highly specialized for contractiona.Smooth

*walls of internal organs (hollow), blood vessels, stomach, intestine, gall bladder, urinary bladder*non-striated, involuntary (some

control- swallowing, etc)

b. Cardiac*bulk of heart*involuntary, one nucleus per cell, striated, intercalated disks, not as dense

c. Skeletal *striated, voluntary, fibers are cylindrical (fiber = cell), multiple nuclei

2. Neural tissue – one of the most specialized, largest cell in the body (1 m)a. Neurons – action cells, no mitotic devices, pick up stimulus and converts to impulse (to other nerves, glands, muscles) *Dendrites – branches, stimulus gatherer, takes impulse to cell body, increase connections through stimuli*Axons – long, single, conduct impulses away from cell body

b. Neuroglia – cells that protect and support neurons

* Do not conduct

*Common sites of tumors (gliomas)

3. Membranesa. Mucous – line cavities that open to the outside

b. Serous – line cavities that do not open to the outside, cover organs, produce serous fluid

c. Synovial – line freely moving joints, not open to the outside