1. mesodermal
2. mechanical support and protection
3. nourishme/physiological support
4. maintenance of body homeostasis>> energy storage.
5. facilitation of immune response
6. facilitation of development, growth, repair.

1. cells: fibroblast, adipocytes, lymphocytes, plasma cells, mast cells, macrophages, neutrophiles, eosinophils, osteopcytes (bone), chondrocytes (cartilage)
2. extracellular matrix: ground stubstance, tissue fluid, extracellular fiber (collagen, elastin, recticular fibers)

by function (type) and arrangement (appearance)

type, density, arragement of cells, fibers composition and character of ground substance.

connective tissue proper: common variety (garden variety)

1. loose connective tissue
2. dense connective tissue: irregular vs regular

Specialized connective tissue: has one specific fx, find in specific area. (adipose, bone, blood, cartilage, hemopoietic tissue, lympathic).

embryonic connective Tissue: mesenchyme (bone and cartilage form), mucous (Wharton's jelly>>embryonic stem cells)

fluffy because contain a lot ground substance (large glycoprotein-jelly like), and no connective tissue.

1. abundant. underneath epothelia lining or organ
2. characteristic: few loosely arranged fibers, alot ground substance a cells.

intestinal loose connective tissue

loose for flexibility, cushioning, avoid trauma, enlargement of vili, diffusion facilitated

characters:

• abundant in collagen fibers
• sparse in cells (mostly fibroblasts)
• not much fround substance
• less vascular but greater strength/more ridges

two types:

dense irregular

dense regular

LCT: loose connective tissue-for absorption and cushioning

DCT: dense connective tissue- for support

AT: adipose tissue

Ep: Epithelium

Characters:

1. lots of collagen, irrecularly orientated-> distensibility
2. little fround substance, few cells.
3. primary cell type=fibroblast
4. prevalence: fibrous covering of bone, cartilage heart, brain, spinal cord, nerve, skeletal muscles, reticular layer of dermis, capsules, septa, traveculae of glands and organs>>has distensibility fromvarious angle.

characteristics:

1. most similar to dense irregular connective tissue.
2. parallel closely packed fibers (collagen, nicely packed)
3. scanty fibroblase in parallel rows (tendinocytes in tendons)

ex.:

tendons:   muscle-bone

ligament:  bone-bone

aponeuroses (flat tendons): muscle-muscle or muscle-bone

endotendineum: wrap around tendon, provide a little more room for stuff.

tendon is organized in bundle, each bundle is a tendon fascicle.

dense regular connective tissue has no room for nerve and vessle.

irregular connective tissue give room for nerve and vessle.

Principle fiber types:

1. collagen
2. reticular
3. elastic

• most abudant ~90% of al fiber associated with C.T.
• flexible, strong, but Not elastic (cannot bend a tendon).
• fibrillar, fibril-associated, seet forming (~ 28 different types)
• Light microscopic (LM) appearance: wavy, variable with and length, stain pinkish with eosin
• Electron microscopical (EM) appearance:bundles of thread-like fibrils.

molecular structure:

• one collagen molecule--tropocollagen
• stacked head to tail--collagen fibrils
• adjacent rows covalently linked--->strength

composition:

• abundance of glycine, proline, hydroxyproline, hydroxylysine (alpha chain)
• redundant sequences
• different in amino acid composition>>> structure and function. 28 different type>> fibril, sheets, crosslinker

amino acid>>tropocollagen>>fibrils (hydroxy-linkage of adjacent strand by hydroxylase)>>fibers.

collagen fibrils may be mineralized into bone.

Vitamin C-deficiency

Proline >X> Hydroxyproline

enzyme that hydroxylase proline and lysince is defected>>cant connect two tropocollagen

teeth fall off since it is held up by collagen.

treatment: drink juice, eat fruit

Characteristics:

• narrow, mesh-like arrangement
• do not form bundes
• do not stain well with H & E.
• mainly type III collagen (sometimes type IV)

FX:

framework for organs and soft tissue

predominance:

• boundary between epithelium and connective tissue
• stroma of organs and soft tissues>> compressibility>>prevent collapsing
• adjacent to adipocytes, small blood vessels, muscle cells. mesh-like structure help with anchoring and supporting.

Elastic Fibers

Characteristics:

• elasticity and molecular memory
• highly branched
• mixed with collagen limits distensibility, prevent snapping

composition: coiled elastin and microfibrils.

Predominance:

• vertebral ligaments
• neck ligament
• larynx-make of elastic fiver hence can be calcify. also this is a sound producing organ hence need elasticity. Old people has calcified larynx>>raspy voice
• blood vessels (tunica intima and media)
• aortic elastic fiber- elaticity to maintain blood pressure. ncrease size when blood pressure is high then recoil when blood pressure level off.

Origin

fibroblast and smooth muscle cells

chracteristics: clear, viscous matrix around cell and fibers, provide space

Function:

provide space

Main components:

• water: to support diffusion of gas and other molecules
• proteoglycans (large "sugar protein")

-protein core & long -chain polysaccharides

 (gag)

-hyaluronic acid (HA) (gag in cartilage)

-Charge (COOH-, SO4-)...

collectively causing increase water absorption.

abundant in Loose connective Tissue

Fixed Type:

• fibroblast and Myofibroblast
• macrophages (fixed or wandering)
• Mast cell
• adipose cells
• undifferentiate mesenchymal cells (to generate and replace cells)

Wandering type:

• lymphocytes
• plasma cells (antibody)
• Basophils, eosinophiles, neutrophils, monocytes (lympathic immune cells)

-principle cell of connective tissue

• secretion of fibers and extracellular matrix
• renewal & regeneration

characteristic and function

• similar to smooth muscle (vimentin)
• wound healing

origin and differentiation:

• Bone marrow: monoblast>>blood monocytes>>histiocytes (derivative of bone marrow cell/hemapoetic cell)

characteristic and Fx

• macrophages
• dentritic cells
• langhans cell>>phagocytosis, antigen presentation

LM Appearance:

• ovoid
• kidney shaped nucleus
• fusion: Langhans giant cells (polynucleated)

LM appearance:

• large ovoid, spherical nucleus (often obscured), storage vesicles
• histamine, heparin & other inflammatory mediators
• cell surface displays microvilli>> responsible for allergy, hypersensitivity

Location:

• near small blood vessels, capsules or organs. never in CNS
• hypersensitivity, anaphylaxis, allergic reaction

ubiquitous in loose connective tissue

LM appearance:

• signet ring (white fat): has enormous central vacuoles, nucleus is pushed up to the side. White fat cells are metabolically inactive. we do not want
• small droplet (brown fat): filled with mitochondria, the cell is very active. We have brown fat in carotid arter to warm blood for the brain.

function: energy storage cushion

• may further differentiate (fibroblast, smooth muscle cell, macrophages. mostly found around blood vessel.
• pericyte provides structural support for small blood vessle, to prevent collapse when blood pressure is low.

• immune cells.
• agrnulocytes: smooth inside, small, round, deeply staining nucleus, and thin cytoplasm.
• most abundant in lamina propria-respiratory and GI tracts

Types:

• T cell (modulate immune response)
• B cells (antibody production)
• NK- cell (natural killer cells- phagocytosis)

Nk-cell finds targer, release enzyme that puncture cancer cell and start degrading it

other agranulocytes:

monocytes (in interstitial fluid)>> blood stream>> macrophages (when enter blood stream)

-phagocytosis, antigen presentation

Leukocytes>> granulocytes:

• Basophils: inflammation
• Eosinophils:  infection, parasitic invasion
• Neutrophils: principle in inflammation