dental embryology, histology, and anatomy exam 1

histology

• is the study of the microscopic structure and function of cells and associated tissue

• also known as microanatomy

millimeter

• used for extremely large body cells, the gingival sulcus, and periodontal pocket depth

• mm

• 0.1 cm

centimeter

• used for pathologic lesions (measuring tissue abnormalities)

• cm

• ~0.4 in

cell

• the smallest living unit of organization

• capable of performing any necessary functions without the aid of other cells

tissue

• cells with similar characteristics of form and function are grouped together to form __

organ

• various tissue types are then bonded together to form __, a somewhat independent body part that performs a specific function or functions

system

• organs can function together globally as a __

exocytosis

• performed by cells

• active transport of material from a vesicle within the cell out into the extracellular environment

endocytosis

• The uptake of materials from the extracellular environment into the cell

• invagination of the cell membrane

• take the form of phagocytosis

phagocytosis

• The engulfing and then digesting of solid waste and foreign material by the cell through the enzymatic breakdown of the material

cell membrane

• “gatekeeper”

• surrounds cell

cytoplasm

• includes the semifluid part contained within the cell membrane boundary

• skeletal system of support or cytoskeleton

vacuoles

• The cytoplasm contains not only a number of structures but also spaces or cavities referred to as __

organelles

• active specialized structures within cells

• allow each cell to function according to its genetic code

  • nucleus

  • mitrochondria

  • ribosomes

  • endoplasmic reticulum

  • golgi complex

  • lysosomes

  • cytoskeleton

nucleus

• largest, densest, and most conspicuous organelle in the cell when it is viewed microscopically

• stores DNA; controls cell divisions

  • The chief nucleic acid in the nucleoplasm is DNA in the form of chromatin (stipples)

  • It contains nucleoplasm and is surrounded by a nuclear envelope

chromosomes

• chromatin condenses into microscopically visible, discrete, rod-like __

• has a centromere

• becomes two filmentous or threadlike chromatids

centromere

• a clear, constricted area near the middle of the chromosome

chromatid

• daughter chromosomes joined by a centromere during cell division

nuceloplasm

• fluid part within the nucleus that contains important molecules used in the construction of ribosomes, nucleic acids, and other nuclear materials

nuclear envelope

• a membrane similar to the cell membrane

• double layered

• may be pierced by nuclear pores (avenues of communication)

nucleolus

• a prominent, rounded nuclear organelle that is centrally placed in the nuceloplasm when the cell is examined microscopically

mitochondria

• The most numerous organelles in the cell

• associated with energy conversion and a major source of adenosine triphosphate (ATP)

ribosomes

• tiny sphere-shaped organelles

• are produced in the nucleolus from rRNA and protein molecules

• are assembled in the cytoplasm

• mobile “protein factories”

endoplasmic reticulum

• rough ER (ribosomes on surface)

• smooth ER (no ribosomes)

• more concentrated in cells inner region as compared to peripheral region

• consists of parallel membrane-bound channels

• like a “highway” system for the cell, transport system for proteins and lipids

golgi complex

• once ER has modified the new protein, it is then transferred to the __ for subsequent segregation, packaging, and transport of protein compounds

• “distribution center” for the cell

• modifies, packages, and transports proteins

lysosomes

• Organelles produced by the Golgi complex and function in both intracellular and extracellular digestion by the cell

• perform phagocytosis

• digests waste and pathogens

centrosome

• is a dense, somewhat oval-shaped organelle that contains a pair of cylindrical structures known as the centrioles

• plays a significant roles in forming the miotic spindle apparatus during cell division

• two centrioles within a __

cystoskeleton

• the interior of the cell is neither liquid nor gel in nature but somewhat between the two, and has a three dimensional system of support known as the __

• maintains cell shape and assists in movement

intermediate filaments

• various types of thicker, threadlike microscopic structures within the cell

• An example is the tonofilaments, or a type of __ __ that forms keratin, which is found in calloused-type of epithelium located in the oral cavity on the attached gingiva as well as the dorsal surface of the tongue

tonofilaments

• have a major role in intercellular junctions

mitosis

• complex process involving many of the organelles of cell

• process starts from one parent cell that produces two genetically identical daughter cells

• produces body cells

interphase

• DNA is replicated during this stage of mitosis

• cell’s “living” time

• has three phases, G1 (initial resting phase), S (synthesis of DNA by duplication), and G2 (second resting phase)

prophase

• chromatin condenses into chromosomes

• replicated centrioles migrate to opposite poles

• nuclear membrane and nucleolus disintegrate

metaphase

• chromosomes align in center

• chromosomes move so that their centromeres are aligned in equatorial plane

• miotic spindle forms

anaphase

• chromosomes are pulled apart

• centromeres split and each chromosome separates into two chromatids

• chromatids migrate to opposite poles by miotic spindle

telophase

• two new nuclei form

• division into two daughter cells occurs

• nuclear membrane reappears

desmosome

• intercellular junction between cells

• cell to cell adhesion, such as tissue to tissue

• seen during repair after an injury to skin or oral mucosa

• disc shaped “spot weld”

• connects adjacent cells

hemidesmosome

• intercellular junction that involves the attachment of a cell to an adjacent noncellular surface

• cell to matrix adhesion

• ex: gingiva to tooth

meiosis

• two cell divisions that produce four non-identical daughter cells

• produces sex cells

cell

• smallest living unit of organization in the body

• each cell can perform any necessary functions without the aid of other cells

tissue types are categorized into __ basic histologic types

• 4

• epithelial, connective, muscle, and nerve tissue

regeneration

• it is the natural renewal of tissue and organ

• produced by the growth and differentiation of new cells and intercellular substances

• occurs through growth from the same type of tissue that has been destroyed or from its precursor

turnover time

• time it takes for the newly divided cells to be completely replaced throughout the tissue

• varies for each of the basic tissue types in the orofacial region

epithelium

• tissue that covers and lines both external and internal body surfaces, including vessels and small cavities

• avascular (NO BLOOD)

  1. protection: inner structures from physical, chemical, and pathogenic attack

  2. epithelial barrier: prevent dehydration and heat loss

  3. tissue absorption, secretion, sensory, and other specialized functions

• can be formed from any of the three embryonic cell layers

both the epithelium of the skin and the oral mucosa are ___ origin

• ectodermal origin

  • epidermis, neurons, pigment cells (melanocytes)

lining of the respiratory and digestive tract are of __ origin

• endodermal origin

• ex: lung cell, thyroid cell, pancreatic cell

linings of the urinary tract are derived from __

• mesoderm

  • cardiac muscle, red blood cells, smooth muscle, skeletal muscle, and tubule cell of kidney

epithelium histology

• avascular

• little or no intercellular substance or tissue fluid

• highly regenerative (rapid turnover) because its deeper germinal cells are capable or reproduction by mitosis

• undergoes cellular differentiation from deeper germinal layers to surface to be shed (skin shedding at top growing from bottom)

epithelium junctions

• joined by intercellular junctions to one another (tissue to tissue) in the form of desmosomes

• Noncellular surfaces are joined by hemidesmosomes

  • ex: basement membrane and junctional epithelium of the gingival sulcular region that is attached to the tooth surface

basement membrane

a __ __ is located between most epithelium and deeper connective tissue, in skin and oral mucosa

epithelium classification

• simple - one layer of epithelial cells

• stratified - two layers of epithelial cells

• squamous - flattened cells with cell height much less than width

• cuboidal- cube-shaped cells with approximately equal cell height and cell width

• columnar- rectangular cells in which cell height exceeds cell width

simple squamous epithelium

• consists of flattened platelike epithelial cells or squames

• lines blood and lymphatic vessels, heart, and serous cavities, as well as interfaces in the lungs and kidneys, referred to as endothelium

• blood vessels

simple cuboidal epithelium

• cube-shaped cells

• line the ducts of various glands, salivary, kidney, etc

• salivary glands

simple columnar

• rectangular, column shape

• lining of other salivary gland ducts as well as the inner enamel epithelium of the maturing tooth germ, whose cells become enamel-forming ameloblasts

• inner enamel epithelium

psuedostratified columnar epithelium

• appearance of false layers due to cells nuclei appearing at different levels

• may have cilia or be non-ciliated at the tissue surface such as upper respiratory tract, nasal cavity, and paranasal sinuses

• respiratory tract

stratified epithelium

• two or more layers of cells, with only the deepest level lining up to contact the basement membrane

• Most epithelium in the body consists of stratified squamous epithelium

  • includes the superficial layer of both skin and oral mucosa

interdigitation

• interlocking

• interlocking of outer epithelium with the deeper connective tissue occurs with the epithelial tissue forming rete ridges or rete pegs

in the mouth, the epithelium of attached gingiva exhibit __ __

• rete ridges or pegs

• basement membrane still lies inbetween

• the sulcular and junctional epithelia do not, nor does scar tissue

keratin

• tough, fibrous, opaque, and waterproof protein that is impervious to pathogenic invasion and resistant to friction

• produced during the maturation of the keratinocyte epithelial cells as they migrate from near the basement membrane to the surface of keratinized tissue

stratified squamous epithelium can be __ or __

keratinized or nonkeratinized

basement membrane

• a thin, acellular structure always located between any form of epithelium and the underlying connective tissue of oral mucosa and has two layers

  • the basal lamina

    • consists of lamina lucida (loose in between space)

    • consists of lamina densa (dense layer)

  • reticular lamina (consists of anchoring collagen fibers and reticular fibers)

basal lamina

• one of the two layers found in the basement membrane

• produced by epithelium

• consists of lamina lucida and lamina densa

reticular lamina

• the deepest layer of the basement membrane

• consists of collagen fibers and reticular fibers produced and secreted by the underlying connective tissue

connective tissue

• derived from somites during prenatal development (differentiated mesoderm)

• most abundant tissue in the body

• compared to epithelium, fewer cells spaced farther apart

• composed of intercellular substances and fibers

• support, attachment, packing, insulation, storage, transport, repair, defense

• vascular (minus cartilage)

fibroblasts

• most common connective tissue cell

• flat and elongated spindle-shaped cells with cytoplasmic processes at each end

• synthesize certain types of protein fibers and intercellular substance to sustain connective tissue

collagen fibers

• main connective tissue fiber

• composed of the protein collagen

• provide strength for connective tissue

• form collagen bundles —> collagen fiber—> collagen fibrils—> collagen microfibrils

• most connective tissue (minus blood) contains some collagen fibers

Tissues containing a large amount of collagen fibers are called __ __ __

• collagenous connective tissue

type 1 collagen

• most common type of collagen protein and the strongest

• found in teeth, lamina propria of oral mucosa, skin, dermis, bone, tendons, and virtually all other types of connective tissue

• fibroblasts, osteoblasts, and odontoblasts are responsible for the synthesis of collagen 1

Be So Totally Cool, Read Big Books mnemonic for collagen fiber classifications

• type 1: Bone, Skin, Tendon

• type 2: Cartilage

• type 3: Reticulum and Blood

• type 4: Basement membrane

Type 2 Collagen fiber

• in hyaline and elastic cartilage

• found in cartilage and joints

type 3 collagen fiber

• in granulation tissue

• found in blood vessels, skin, wound healing

• main component of reticular fibers but also found in artery walls, skin, intestines, uterus

type 4 collagen fiber

• in basal laminae of basement membrane, eye lens, filtration system of capillaries, kidneys nephron glomeruli

• basement membrane

elastic fibers

• another type of connective tissue fiber

• provide flexibility

• composed of microfilaments so they can stretch and then return to original shape after contraction (elastic type tissue)

• This tissue has the ability to stretch and then return to its original shape after contraction or extension

• certain regions of oral cavity such as soft palate to allow tissue movement

reticular fibers

• can be found in an evolving embryonic tissue and rarely in adult body

• form a delicate network

• composed of protein reticulin and are very fine hairlike fibers that branch, forming a network

soft connective tissue

• tissue found in the deeper layers of both the skin and oral mucosa, such as a connective tissue proper

firm connective tissue

• consists of different types of cartilage

rigid hard connective tissue

• form of connective tissue consists of bone

fluid connective tissue

• consists of blood with all its components and lymph

connective tissue proper location

• both loose and dense types of connective tissue are found togetehr in two adjoining layers as the __ __ __

• found deep to epithelium and basement membrane within the deeper layers of both the skin and oral mucosa

• in the skin is dermis found deep to epidermis

loose connective tissue

• fewer fibers, more ground substance

• superficial layer of both dermis of skin and lamina propria of the oral mucosa is composed of __ __ __

• layer of __ __ __ in both the dermis and lamina propria of oral mucosa is considered the papillary layer

• forms the connective tissue papillae, which is the other part of the interdigitated tissue with the epithelial rete ridges that connects the two tissues

1. areolar

2. adipose *

3. reticular *

dense connective tissue

• deep to loose connective tissue

• more fibers, less ground substance. deep to loose connective tissue

• is both the dermis and the lamina propria is also considere the dense or reticular layer

1. regular

2. irregular

3. elastic *

supporting connective tissue

cartilage and bone

cartilage

• semisolid matrix

• firm but flexible nonmineralized connective tissue in the body

• avascular, heals slowly

  1. hyaline

  2. fibrocartilage

  3. elastic

bone

• solid matrix

• highly vascularized (contains red blood cells) so repairs quickly

• intramembranous ossification

• endochondral ossification

  1. spongy (cancellous)

  2. compact

fluid connective tissue

• blood

• carry oxygen, nutrients, and waste

• RBCS

• WBCS

  • neutrophils

  • lymphocytes

epidermis

• the outermost layer of skin

• provides a waterproof barrier and creates skin tone (melanocytes)

• consists of keratinized epithelium

• high turnover rate

dermis

• beneath the epidermis

• made up of loose (papillary layer) connective tissue and dense connective tissue

  • contains hair follicles

  • sweat glands

subcutaneous tissue (hypodermis)

• made of fat

lamina propria

• in oral mucosa, the deeper connective tissue proper is consider the _ __ and the even deeper connective tissue sometimes present is the submucosa, like the hypodermis in the skin

papillary layer

• superficial layer

• forms connective tissue papillae, which are interdigitated with the epithelial rete ridges

• the “loose” connective tissue layer superficial to dense connective tissue

connective tissue proper turnover, regeneration, and repair

1. First formation of a hemostatic plug (stops bleeding)

2. inflammation to remove dead and damaged tissue

3. formation of granulation tissue (appears red)

4. migration and proliferation of fibroblasts ( appear pale and firm due to increased fiber and lower blood vessels)

5. tissue remodeling and wound contraction

6. increased scars= fibrosis

collagen fibers aging process

• begin to fall apart, elastic fibers stiffen and thicken, wrinkling the skin

oil glands aging process

• cease production

melanin aging process

• production decreases, leading to a more pallid color and gray hairs

keratin cell aging process

• cease production and already produced __ becomes thin and stiff

adipose connective tissue

• specialized connective tissue

• fatty tissue found beneath the skin, around organs, and various joints, and in regions of the oral cavity

• tightly packed with little or no matrix

• after fibroblasts, the predominant type of cell found in this tissue is the adipocyte which stores fat intracellularly

elastic connective tissue

• specialized connective tissue

• has many elastic fibers in its matrix, which combine strength with elasticity, such as in the tissue of vocal cords

reticular connective tissue

• specialized connective tissue

• is a delicate network of interwoven reticular fibers forming a supportive framework for blood vessels and internal organs

cartilage

• firm but flexible nonmineralized connective tissue in the body

• forms most of the temporary skeleton of the embryo then structural support for soft tissue after birth

• present at articular surfaces of most freely moveable joints

cartilage properties

• composed of cells and matrix

• its matrix is composed of fibers, mostly collagen, and intercellular substance

• matrix is similar to soft connective tissue composition except firmer

• the connective tissue surrounding most cartilage is the perichondrium in which it receieves its nutrients from