histo-connective tissue

Major constituent is __________– protein fibers, ground substance, tissue fluid

Origin

• __________

• ……………. cells migrate and surround and invade developing cells to become __________ cells

__________ cells

- Oval nucleus, prominent nucleoli, fine chromatin, sparse

cytoplasm –extends as thin processes away from the

nucleus

- Point of origin of all connective tissue cells, and blood and blood vessels

- 3 Classes of components (CONNECTIVE TISSUE):

1.

2.

3.

______ SUBSTANCE

- Viscous, colorless, transparent, and homogenous

- Fills space in between cells and fibers

- Acts as a lubricant

- Barrier to foreign particles

- Difficult to examine in fresh and fixed samples due to high water content. The sample tend to become dehydrated so the ground substance is no longer visible.

GROUND SUBSTANCE

- 3 classes of components:

1.

2.

3.

Multiadhesive Glycoproteins

• Structural glycoproteins (3):

a.

b.

c.

(CONNECTIVE TISSUE) FIBERS

3 main types of fibers:

1.

2.

3.

(Types of) Collagen Fibers

1. ______ (types ___, ___, ___)

2. ______(type ___)

3. ______(type ___)

(2) Structure(s) of Collagen:

1.

2.

(6) CELLS OF CONNECTIVE TISSUE

A.

B.

C.

D.

E.

F.

TYPES OF CONNECTIVE TISSUES

A.

B.

C.

D.

E.

one of GROUND SUBSTANCE component:

???

• Also called ____

• Linear polysaccharides

• Repeating disaccharide units made up of ____ and a

____

o ……….: glucosamine or galactosamine

o ……….: Glucuronic or iduronic acid

• Largest, almost unique, most ubiquitous - heparan sulfate

(100s-1000s kDa)

• Intensely _____ and act as polyanions (hydroxyl,

carboxyl, and sulfate groups)

• Binds a great number of cations (sodium), intensely

hydrated structures (hydrated because Na attracts water)

one of GROUND SUBSTANCE component:

???

• Composed of a protein core to which various numbers

and combinations of GAGs are covalently attached

• Carbohydrate portion constitutes 80-90% of the weight

• ……. bind to collagen owing to electrostatic

interaction between their acid groups and the basic

amino acid residues of collagen

• Synthesis of protein moiety begins in the ______

• Glycosylation initiated in the ______ and completed in the

______ where sulfation also occurs

one of GROUND SUBSTANCE component:

???

• Have multiple binding sites for cell surface receptors

(integrins) and other matrix macromolecules

• Very large molecules with branched oligosaccharide

chains

• Important roles for the adhesion of cells to their

substrates

• Structural glycoproteins (of Multiadhesive Glycoproteins):

???

- (MW 235 - 270 kDa), dimeric

- Synthesized by fibroblasts and epithelial cells

- Has binding sites for cells, collagen, and

glycosaminoglycans

- Helps mediate normal cell adhesion and migration

• Structural glycoproteins (of Multiadhesive Glycoproteins):

???

- Large (200-400 kDa), trimeric, cross-shaped glycoprotein

- Detected in the basal laminae

- Partially responsible for the adhesion of

epithelial cells to basal lamina

• Structural glycoproteins (of Multiadhesive Glycoproteins):

???

- Act as matrix receptors for specific sequences on laminin, fibronectin, some collagens, and certain other ECM proteins

- Bind their ECM ligands with relatively low affinity, allowing cells to explore their environment without losing attachment to it or becoming glued to it.

- Heterodimers of two transmembrane

Connective tissue fiber:

???

- Constitute a family of proteins selected during evolution for their ability to form various extracellular fibers, sheets, and networks, all of which extremely strong and resistant to normal shearing and tearing forces.

- Most abundant protein in the human body (30% dry weight)

- ____ types have been described but the most important, best studied, and most common types are types __, __, __, __, __, __, __, __, __

Categories of Collagen:

______ Collagen (types __, __, __)

- Have subunits that aggregate to form large fibrils clearly

visible in the electron or light microscope

- Collagen type __, the most abundant and widely distributed collagen, forms large, eosinophilic bundles usually called ______ .

- Densely fill the connective tissue, forming structures such

as tendons, organ capsules, and dermis

Categories of Collagen:

_______ collagens (type __)

- Subunits produced by epithelial cells and are the major

structural proteins of external laminae and the basal

lamina in all epithelia

Categories of Collagen:

_____________ (type __)

- Short collagens that link fibrillar collagens to one another

(forming larger fibers) and to other components of the

ECM

Synthesis of collagen is very widespread among many cells though originally thought to be restricted to fibroblasts, chondroblasts, osteoblasts, and odontoblasts

- Principal amino acids composing collagen:

• _______ (33.5%)

• _______ (12%)

• _______ (10%)

- Amount of collagen in a tissue can be determined by measuring the _______ content

- 2 amino acids characteristic of collagen protein: _______ and _______

• Not incorporated in the protein itself but results

from the hydroxylation of the _______ and _______ in

the nascent collagen polypeptide in the RER during

synthesis

Structure of Collagen:

???

- Protein unit that polymerizes to form collagen fibrils

- Elongated (280 nm in length and 1.5 nm in width)

- Consists of 3-unit polypeptide chains intertwined in a

triple helix

- Difference of chemical structures of these polypeptide

chains account for the different types of collagens

- …………. molecules aggregate into microfibrillar

subunits packed together to form _______

- Aggregation and packing are achieved by hydrogen and

hydrophobic interactions

- Structure is reinforced by covalent cross-links, catalyzed

by _______

Structure of Collagen:

???

- Thin and elongated structures

- Variable diameter (20 to 90 nm)

- Traverse striations (periodicity of 64 nm)

• Determined by the overlapping arrangement of subunit tropocollagen molecules.

• Dark band retain more stain due to more free chemical groups

- In types __ and __ – fibrils associate to form fibers

• Type __

Fibers can associate to form bundles

• Type __

Can occur as fibrils that does not form fibers

• Type __

Does not form fibrils or fibers but occur as unpolymerized or sparsely polymerized procollagen molecules

- Type __, __, and forms fibrils that are called ______

collagens

- Type __ and __ do not form fibrils

(just read)

Collagen Synthesis

1. Polypeptide alpha chains are assembled on the polyribosomes in RER and injected into the cisternae.

• These have typically has long central domains rich in

proline and lysine; in type I collagen every 3rd amino acid is glycine.

2. Hydroxylation of proline and lysine occurs.

• Hydroxylation begins after the peptide chain has reached a certain minimum length and is still bound to the ribosomes.

• Enzymes: Peptidyl proline hydroxylase and peptidyl

lysine hydroxylase

3. Glycosylation of hydroxylysine

• Different collagen – different amounts of carbohydrate

(galactose or glycosylgalactose linked to hydroxylysine)

4. Alpha chain is synthesized with registration peptides (NH- and COOH- terminal ends) assemble to form the procollagen which is transported into the extracellular environment.

• Registration peptides ensure proper positioning of the

alpha chains, makes the procollagen soluble and prevents premature assembly and precipitation in the cell.

5. Registration peptides are removed by procollagen peptidases to turn procollagen into tropocollagen.

6. Fibrils aggregate to spontaneously form fibers.

7. Fibrillar structures are reinforced by covalent crosslinks,

catalyzed by lysyl oxidases.

Degradation (of collagen) is achieved by __________

Connective tissue fiber:

_________ Fibers

• Most abundant fibers in connective tissues

• Causes tissue to become _______ (color)

• _______ (birefringent or not?)

• Inelastic and have a tensile strength greater than steel

• Consist of closely packed thick fibrils (75 nm thick)

• Can be organized in parallel array forming bundles

• Better studied in spread preparations and appear as

elongated and tortous cylindric structures – indefinite

length; diameter of 1-20 μm

• _____philic

Color: Stain

- Pink: _____

- Blue: _____

- Green: _____

- Red: _____

- Extremely thin (0.5 to 2 μm)

Connective tissue fiber:

_________ Fibers

- Extremely thin (0.5 to 2 μm)

- Extensive network in some organs

- Non-visible in ______ preparations

- Stained black by ______ (agyrophilic).

- PAS (______) positive

- Staining due to high content of glycoproteins

- Have 6-12% hexoses compared to 1% in collagen

- Composed mainly of type ______ collagen

- Formed by loosely packed, thin (45nm) fibrils bound together by small interfibrillar bridges (proteoglycans and glycoproteins)

- ______ birefringence

- Abundant in smooth muscle, endoneurium and the framework of hematopoietic cells (bone marrow), spleen, and lymph nodes

- Constitute a network around cells of parenchymal organs

- Abundance of reticular fibers in embryogenesis, inflammatory processes, wound healing but is replaced eventually by regular collagen fibers

- Create a flexible network in organs subjected to increase volume

Connective tissue fiber:

________ Fibers

- Thinner than type I collagen fibers and form sparse networks interspersed with collagen bundles.

- Have rubberlike properties to be stretched or distended and return to their original shape.

- ________- elastin occurs in fenestrated sheets; in wall of large blood vessels especially arteries.

Elastic Fibers….

- Darkly stain in orcein and aldehyde fuchsin; poorly stain in ________.

- Fibers branch and unite with one another into an irregular network

- Characteristic ________ color in fresh samples

- Capable of stretching to 150% of their length and yields very easily to traction but readily returns into original shape when relaxed

- Methods to demonstrate

• ________: Purple

• ________: Black

• ________: Dark blue

Elastic Fibers….

- 2 components:

• Amorphous central region containing elastin

• Sheath of 14 nm tubular microfibrils

- Development:

• _____appear first

• _______ fills the space in tube

Elastic Fibers….

-???

• Secreted as proelastin (MW 70,000) which polymerizes to form elastin

• Produced by fibroblasts in skin, tendon, smooth muscle

• Resistant to boiling, extraction with dilute acids and alkali and not digested by trypsin

• Has a tertiary and quaternary structure, stabilized by

hydrophobic interactions between the nonpolar peptide

chains

- Amino acid composition resembles collagen but has greater quantity of valine and alanine

- Two unusual amino acids: ___ and ____, (formed by covalent reactions among 4 lysine residues) thus crosslinks elastin and is thought to give its elastic properties

- Occurs in a nonfibrillar form as fenestrated membranes in some walls of blood vessels

CELLS OF CONNECTIVE TISSUE:

???

- Most commonly found cells in connective tissue.

- Synthesizes fibers and amorphous intercellular substrate.

- 2 different morphologic types

1. Younger, more actively synthesizing cell (_______)

• Abundant and irregularly shaped cytoplasm;

nucleus is ovoid, large and pale staining, with fine

chromatin, prominent nucleolus; cytoplasm rich in

RER, well developed Golgi complex

2. Mature, quiescent (_______)

• Found in the already formed tissue

• Smaller cell, spindle shaped, fewer processes;

nucleus is smaller, darker; acidophilic cytoplasm;

less well-developed RER and Golgi complex

- When actively stimulated, mature cells may revert to younger, active form (i.e., wound healing)

- Synthesize collagen reticular and elastic fibers,

glycosaminoglycans, and glycoproteins

- …….. rarely undergo division

- Mitoses are only observed when the organism requires additional fibroblasts (tissue damage)

- Targets of growth factors that influence cell growth and

differentiation.

- _________: wound healing, have well-developed contractile function and are enriched with a form of actin.

CELLS OF CONNECTIVE TISSUE:

???

- Phagocytic capacity

- Derive mainly from precursor cells that produce monocytes –transported where they mature into …………

- Can proliferate locally to produce more cells

- Ingestion of particles and their digestion by the lysosome

- Referred by pathologists as “________”.

- 10-30 um in diameter and ________”-shaped nucleus.

CELLS OF CONNECTIVE TISSUE:

???

- Oval to round connective tissue cell (20-30 μm)

- Cytoplasm filled with basophilic granules

- Nucleus is small spherical and centrally situated

- Metachromatic

- Release _________

- Two populations:

1. ____________: Proteoglycan is heparin

2. ___________: Proteoglycan is chondroitin sulfate

- Contain specific receptor for IgE,

CELLS OF CONNECTIVE TISSUE:

???

- Large ovoid cells, with a basophilic cytoplasm, rich RER

- Nucleus is spherical and eccentrically placed with compact coarse heterochromatin

- Responsible for the synthesis of antibodies

CELLS OF CONNECTIVE TISSUE:

???

- Specialized for storage of neutral fats or heat production

CELLS OF CONNECTIVE TISSUE:

???

- Derived from circulating blood cells and they leave blood by migrating between the endothelial cells of venules to enter connective tissue.

- This process increases during inflammation in response to injury and foreign substances, including pathogenic bacteria or irritating chemical substances.

- Most …….. function only for few hours or days and then undergo apoptosis.

TYPES OF CONNECTIVE TISSUES

???

- Areolar tissue

- More abundant type

- Fills space between fibers and muscle sheaths

- Supports epithelial tissue

- Composed of all main components of connective tissue proper, most abundant cell is the fibroblast and macrophages

TYPES OF CONNECTIVE TISSUES

???

- Same component as loose but with a clear predominance of collagen fibers

- Fewer cells – Fibroblasts most common

- Less flexible and resistant to stress

- Can be:

• ________

- Without definite orientation

• ________

- 3D network and provide resistance to stress from all

directions (tendons)

TYPES OF CONNECTIVE TISSUES

??

- Composed of thick, parallel elastic fibers

- With a surrounding small amount of loose connective

tissue, flattened fibrocytes

- Occurs in the yellow ligament of the vertebral column and in the suspensory ligament of the penis

TYPES OF CONNECTIVE TISSUES

????

- Specialized loose connective tissue variation, provides the architectural framework of the myeloid and lymphoid

hematopoietic cells

- ____________ – fibroblasts specialized in the production of reticular fiber constituents

TYPES OF CONNECTIVE TISSUES

???

- Abundance of amorphous ground substance composed chiefly of hyaluronic acid

- Jelly like tissue containing collagen fibers and few elastic or reticular fibers

- Mainly fibroblasts

- Principal component of the umbilical cord, also found in the pulp of young teeth