microscopic anatomy of the periodontium chpt 2

what is a cell

the smallest structural unit of living matter capable of functioning independently

group together to make tissues

4 types of tissues

• epithelial tissue

• nervous tissue

• muscle tissue

• connective tissue

ectoderm

enamel

mesoderm

connective tissue, muscle, bone, blood

endoderm

bronchi, alveoli, ducts from gallbladder and pancreas

extracellular matrix

• a mesh like material that surrounds the cells

• structural and biomechanical scaffold for the cells

• holds cells together, provides framework for movement and interaction

• consists of ground substance and fibers

• basal lamina

• rigid

ground substance

gel-like and fills space between cells

fibers

are collagen, elastin and reticular fibers

why is the extracellular matrix rigid?

is undergoes mineralization by the deposition of calcium and phosphate

microscopic anatomy on epithelial tissue

• makes up the outer surface of the body

  • skin and mucosa of mouth are made up of stratified squamous epithelium

• lines body cavities

composition of epithelial tissue

• cells are plentiful

• closely packed cells

• bound together in sheets

• extracellular matrix is sparse and a minor component

• basal lamina supports epithelium

what is keratin

a tough fibrous structural protein that occurs in the outer layer of the skin and the oral epithelium

what is keratinization

process by which epithelial cells on the surface of the skin become stronger and water proof

keratinized epithelial cells

• have no nuclei

• form a rough, resistant layer on the surface of the skin

• most heavily keratinized epithelium is on palms of hands and soles of feet

• what applies to hands and mouth applies to rest of the body

• if white tissues are in mouth, its due to trauma

non-keratinized epithelial cells

• have a nuclei

• act as a cushion against stress and wear

• are softer and more flexible

• found in areas such as the mucosal lining of the cheeks

• allows for speech, chewing and facial expressions

characteristics of epithelial tissues

• they do not have a blood supply, they are avascular

• receive oxygen and nourishment from blood vessels in the underlying connective tissue via diffusion

what is connective tissue?

• it fills spaces between tissues and organs

• it supports and binds other tissues

• its cells are separated by abundant extracellular substance

• it has sparse cells

• it has lots of extracellular matrix

specialized forms of connective tissue

• cementum

• dentin

• alveolar bone

• pulp

enamel is not

connective tissue, it is epithelial tissue

cells in connective tissue

• fibroblasts

• macrophages and neutrophils

• lymphocytes

fibroblasts in connective tissue

• are the fiber builders

• form the extracellular matrix

• secrete ECM into the intracellular spaces

macrophages and neutrophils in connective tissue

• phagocytes or “cell eaters”

• destroy

• devour dyign cells and microorganisms that invade body

lymphocytes in connective tissue

play a major role in the immune response

most important cell in connective tissue

fibroblasts

what type of cell makes fibrin, collagen and elastin

fibroblasts (important in aging)

fibroblasts cannot form collagen without

vitamin c

fibroclasts

produce collagenase, which breaks down tissue and bone (breaks down what fibroblasts build)

cycle of fibroblasts

build - destroy - rebuild

basal lamina

• thin layer secreted by epithelial cells

• not visible under light microscope

• can be seen on electron microscope

• can be wavy or smooth

• aids in attachment of epithelial cells to adjacent structures

if basal lamina is wavy

it has deep extensions of epithelial ridges of epithelium that reach down into connective tissue

if basal lamina is not wavy

can become wavy if bacteria invade

rete pegs

epithelial ridges

what is a

basal lamina

what is b

basement membrane

characteristics of epithelial-connective tissue boundary

wavy, uneven pattern that increases surface area, resists mechanical forces, and increases area to receive nourishment from connective tissue

epithelial ridges at epithelial-connective border

reach down into connective tissue

connective tissue papilla at epithelial-connective border

fingerlike extensions that project up and interlock with epithelium

if tissues in the mouth are sloughing the cause is

loss of hemidesmosomes

squamous cell carcinoma in SITU

• did not breach basement membrane

• caught before invaded connective tissue and spread

• easiest to treat

• different from squamous cell which is very invasive

• basal cell carcinoma is rarely invasive

what are epithelial cell junctions

• cellular structures that mechanically attach a cell and its cytoskeleton to neighboring cells or basal lamina

• help withstand mechanical forces and form a protective barrier

2 types of epithelial cell junctions

• desmosome

• hemodesmosome

hemidesmosomes

connect living to non-living (basal lamina is non-living)

• cell - to - basal lamina connection

• important form of cell junction found in the gingival epithelium

• represents ½ a desmosome

desmosomes

connect living to living (similar to velcro)

• cell to cell connection

• important form of cell junction found in gingival epithelium

what is gingival epithelium

• specialized stratified squamous epithelium

• functions well in a wet environment

• 3 anatomical areas

  • oral epithelium

  • sulcular epithelium

  • junctional epithelium

oral epithelium

• covers free and attached gingiva

• faces the oral cavity

sulcular epithelium

• lines the sulcus

• faces the tooth surface without being in contact with the tooth surface

• not keratinized

junctional epithelium

• base of sulcus

• attaches gingiva to tooth or cementum

• super thin and easy to break

layers of oral epithelium

• basal cell layer

• prickle cell layer

• granular cell layer

• keratinized cell layer

basal cell layer of oral epithelium

cube-shaped cells

prickle cell layer of oral epithelium

spine-like cells with large intracellular spaces

granular cell layer of oral epithelium

flattened cells and increased intracellular keratin

keratinized cell layer of oral epithelium

flattened cells with extensive intracellular keratin

sulcular epithelium - lining of the gingival sulcus

• thin, nonkeratinized epithelium

• has 3 cellular layers

  • basal

  • prickle

  • superficial

• permeable, allowing fluid to flow from gingival connective tissue into the sulcus

• fluid is known as gingival crevicular fluid

• fluid flow is slight in health and increases in state of disease

• sulcular epithelium

junctional epithelium

• forms base of sulcus and joins gingiva to tooth surface

• surrounds cervix of tooth

• easiest point of entry for bacteria

• base of sulcus made up of coronal-most cells of junctional epithelium

• in health, JE attaches to tooth slightly above CEJ

• thin, nonkeratinized

• sulcular and junctional areas provide easiest entry for bacteria to inve connective tissue

• 2 layers

  • basal

  • prickle

• thicker at coronal zone and thin at apical zone

• smooth tissue interface

why is junctional epithelium important?

• the teeth create a break in the epithelial covering

• this break creates an opening for microorganisms to enter the body

• body tries to seal opening by attaching epithelium to the tooth

• this junction or “connection” is called the junctional epithelium

• JE provides a protective barrier between plaque biofilm and connective tissue

• epithelial cells defend periodontium from infection bu signaling the immune response

components of the junctional epithelium

• layers of closely packed epithelial cells

• desmosomes and hemidesmosomes

• sparse ECM

internal basal lamina

thin, between JE and tooth surface

external basal lamina

thin, between JE and gingival connective tissue

hemidesmosomes enable

cells to attach to the internal basal lamina and surface of the tooth

attachment of the hemidesmosomes and the internal basal lamina is not static

cells can move along the tooth surface

components of gingival connective tissue

• provides solidity to gingiva

• attaches gums to cementum of the root and alveolar bone

• few cells

• abundance of ECM

• 3 types of cells

gingival connective tissue has 3 types of cells

• fibroblasts (macrophages)

• mast cells (neutrophils)

• immune cells (lymphocytes)

in the gingival connective tissue the fibroblasts

produce (build) fibers

ECM is composed of

• collagen fibers

• fibroblasts

• vessels

• nerves

what is the matrix mainly produced by?

fibroblasts

what cells are embedded in the matrix

connective tissue cells

ECM is essential for

maintenance of normal function of connective tissue

ECM is responsible for

transportation of water, nutrients, metabolites, oxygen, etc.

collagen fibers in ECM form

dense network of strong, rope-like cables that secure and hold connective tissues together

collagen fibers in ECM enable

gingiva to form a rigid cuff around the tooth

monocytes turn into macrophages

once they go into tissue from blood

macrophages eat

bacteria, dead tissue, and spent RNA

longer life expectancy than neutrophils

macrophages

neutrophils

make up 70% of white blood cells

macrophages and neutrophils

neutro. are like EMS 1st responders

macro. follow 2 days later

then neutro. dies and pus is created

what are supragingival fiber bundles

a network of rope-like collagen fiber bundles

supragingival fiber bundles are located

coronal to the crest of the alveolar bone

embedded in the gel-like ECM

supragingival fiber bundles functions

• strengthen and reinforce attachment to JE to tooth

• brace free gingiva against tooth

• provide rigidity to free gingiva needed for chewing

• unite free gingiva with cementum and alveolar bone

• connect adjacent teeth to one another

fiber bundles are classified

based upon orientation, sites of insertion and structures that they connect

course of gingival fiber bundles

1. dentogingival

   • coronal

   • horizontal

   • apical

2. alveologingival

3. interpapillary

4. transgingival

5. circular, semicircular

6. transseptal

7. periosteogingival

8. intercircular

9. intergingival

principal fiber groups

• dentogingival

• alveogingival

• dentoperiostal

• transseptal

secondary fiber groups

• periosteogingival

• interpapillary

• transgingival

• intercircular

• semicircular

• intergingival

alveogingival fiber group

extend from periosteum of alveolar crest into gingival connective tissue

circular fiber group

circle tooth like a ring; not attached to cementum

dentogingival fiber group

embedded in the cementum near CEJ; fan out; attach gingiva to teeth

peristeogingival fiber group

extend from periosteum of alveolar bone; attach gingiva to bone

intergingival fiber group

extend mesiodistally along entire arch and around last molars; link adjacent teeth into a dental arch unit

intercircular fiber group

encircle several teeth; link adjacent teeth in dental arch

interpapillary fiber group

located in papilla above transseptal fiber bundles; connect oral and vestibular interdental papilla

transgingival fiber group

extend from cementum near CEJ; run horizontally between teeth

transseptal fiber group

pass from cementum of 1 tooth, over crest of alveolar bone, cementum of adjacent teeth; secure ligaments of teeth

• last to be destroyed

PDL

• thin sheet of fibrous connective tissue

• surrounds roots of teeth

• adjoins the root cementum with the socket wall via bundles of collagen fibers

• thickness of space approx. 0.05 - 0.25 mm

• thickness depends of age of patient and function of tooth

• very sensory, can detect biting on thinnest things

cells in the PDL are mainly

fibroblasts with some cementoblasts and osteoblasts

most important function of the PDL

supportive- to anchor the tooth to the socket and to separate the tooth from the socket wall

sensory function of the PDL

supplied with nerve fibers that transmit pressure and pain

nutritive function of the PDL

supplied with blood vessels that provide nutrients to cementum and bone

formative function of PDL

contains cementoblasts that produce cementum throughout life of tooth; osteoblasts maintain bone of socket

resorptive function of PDL

cells can induce rapid bone resorption in response to severe pressure

5 fiber groups of the PDL

1. alveolar crest

2. horizontal

3. oblique

4. apical

5. interradicular

alveolar crest fiber group of PDL

extend for cervical cementum to alveolar crest; run downward; resists horizontal movement of tooth and prevents tooth displacement