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62 Cards in this Set

  • Front
  • Back
What is a blastocyst composed of?
inner cell mass and trophoblast
What does the inner cell mass become?
What does the trophoblast become?
What does the prochordal plate consist of?
epiblast and hypoblast (sometimes calls the embryonic ectoderm and embryonic endoderm). It is present in the head end of the embryonic disc
After the head fold happens what does the prochordal plate become?
the buccopharyngeal membrane
What is the trilaminar disc made up of?
Ectoderm, endoderm, and mesoderm. It is a product of gastrulation and the primitive streak is present.
Where is the primitive streak found?
In the trilaminar disc. In the epiblast layer.
What does the mesenchyme from the primitive steak form?
Forms all three germ layers; does not migrate between the two layers of the prochordal plate; extends from tail end of embryonic disc toward head end.
What is the notochord and what is it derived from?
It is a cord of mesoderm along the midline between the primitive node and prochordal plate. Derived from the cells of the primitive node.
What does the notochord become in a fully formed fetus?
Most of it degenerates but some of it becomes the nucleus pulposas of the intervertebral discs.
What signaling function does the notochord have?
Sonic hedgehog signaling function inducing formation of the CNS.
What does the ectoderm become?
Enamel (oral epithelium, dental lamina, enamel organ), skin, CNS, nasal epithelium, hair, nails
What are neural crest cells?
A temporary group of cells derived from the ectoderm.
What do cephalic neural crest cells give rise to?
The ectomesenchyme which becomes cartilage and bones of face and head including Meckel's cartilage, mandible, maxilla, and those parts of the tooth and tooth socket derived from dental papilla (dentin and pulp) and dental follicle (alveolar bone, PDL, cementum). But NOT muscles, ameloblast or enamel,
What is derived from the dental papilla?
dentin and pulp

What is derived from the dental follicle?
alveolar bone, PDL, cementum
What do the cephalic and trunk neural crest cells become?
Peripheral neurons and ganglia, melanocytes, and Schwann cells.
What does mesoderm become?
muscles, bones (not including those derived from neural crest cells), kidneys, gonads, and spleen.
What does endoderm become?
thyroid, lungs, liver, linings of gut (including pharynx and pharyngeal pouches) and respiratory tract.
Where does the anterior palate come from?
ingrowth of intermaxillary segment
Where does the posterior palate come from?
Comes from ingrowth and fusion of lateral palatine processes of the maxillary prominences
Where does the intermaxillary segment come from?
Comes from fusion of medial nasal prominences , which come from frontonasal prominence. It does NOT come from an arch.
Where does the medial nasal prominence come from?
From the frontonasal prominence.
In order for the palate to form what must happen to the lateral palatine processes?
Lateral palatine processes (palatal shelves) must elevate, extend to the midline and fuse with each other. This requires: adequate numbers of palatal Neural Crest Cells as well as breakdown of the surface epithelium of the fusing edges of the palatal shelves.
What has been shown to result in palatal malformations?
Loss of expression of Msx-1
What are derivatives of Meckel's cartilage?
Malleus, incus, anterior ligament of the malleus, sphenomandibular ligament. NOT mandible or maxilla.
The tongue is made from derivatives of which arches?
1st, 2nd, 3rd and 4th
What forms the epithelial covering of the tongue?

dorsal surface of anterior part: lateral lingual swellings

dorsal surface of posterior part: hypobranchial eminence

How is the tongue made?
lateral lingual swellings (from 1st arch) form epithelial coverings of dorsal surface of anterior part of adult tongue; hypobranchial eminence ( 3rd & 4th arches) forms epithelial coverings of dorsal surface of posterior part of adult tongue. Tuberculum impar (first swelling to appear, from 1st arch) & copula (2nd arch) are overgrown so don’t form part of epithelial coverings of adult tongue.
Where does the signal that initiates tooth development come from?
oral epithelium (ectoderm)
Where does the signal that directs tooth type come from?
What is Hertwig's epithelial rooth sheath
An extension of the inner and outer enamel epithelium after the crown is formed. It is NOT present during the bell stage.
What does the Hertwig's epithelial root sheath do?
Induces differentiation of root papilla cells to become odontoblasts. The root sheath itself does not secret dentin or any components of the root. But some HERS cells might undergo epithelial mesenchymal transformation to become cementoblasts.
After Hertwig's epithelial root sheath break down, what does it leave?
Epithelial cell rests of malassez in the PDL.
Where do ameloblasts come from?
Differentiate from the inner enamel epithelium of the enamel organ (ectoderm)
During the secretory stage what is the level of mineralization of enamel?
30%-It is immediately mineralized to this amount
What is the enamel matrix made from?
Mostly amelogenins. they do not form an interwoven matrix though, they are thought to form nanospheres that regulate crystal growth. The enamel matrix does NOT contain collagen.
What is the composition of mature enamel?

96% mineral (hydroxyapatite)

1-2% organic material (mostly TRAP)

2% water

Where can you find rodless enamel?
At the DEJ and surface of the tooth. It is thicker at the surface in primary teeth than secondary.
What is the Tomes process associated with?
The formation of structured enamel. It is present during the secretory stage. Gives the ameloblast a picket fence appearance under the microscope.
How are crystals in the rod core oriented?
Parallel to the long axis and tightly packed.
Where is much of the organic material in the enamel found?
In the rod sheath.
What is the rate of formation of primary dentin?
Primary dentin (mantle and circumpulpal dentin) is formed at a rate of 4 microns per day as root and crown are developing.
When is secondary dentin formed?
After teeth come into functional occlusion. It can be recognized by a bend in the tubules near the pulp chamber of a mature tooth.
What is the level of mineralization of dentin?
70% mineral (hydroxyapatite)
What is intertubular dentin?
It is the organic matrix of dentin that is located between the dentinal tubules. Mostly made up of type I collagen.
How does mineralization occur in mantle and circumpulpal dentin?

mantle: By matrix vesicles

-linear pattern of mineralization

circumpulpal: heterogenous nucleation

-globular pattern of mineralization may be seen

What is interglobular dentin?
Hypomineralized regions associated with the globular pattern
Which dentin is hypermineralized and where is it located?
Peritubular dentin: formed inside of the tubule. It does not have a collagen matrix.
What type of nerve fibers are located in the pulp?
Both afferent and sympathetic fibers
What is dentinal sensitivity thought to be due to?
Fluid movement through the tubules that stimulates the afferent nerve fibers in the plexus of Raschkow.
What may be the role of pulp innervation?
Pulpal homeostasis
What is the mineralization of cementum and what is the bulk of the organic matrix made from?

~50% hydroxapatite

-organic is mostly type I collagen

Where do cementoblasts come from?
From follicle after breakdown of HERS.
What are the two histological types of cementum?

-acellular cementum with extrinsic fibers from the PDL

-cellular cementum with intrinsic fibers from cementoblasts

What is acellular cementum?

-Primary cementum formed initially on coronal 2/3 of root and on entire root of incisors and canines.

-Has an attachment function

What is cellular cementum?

-Type of secondary cementum formed after tooth erupts on apical 1/3rd of root on molars, premolars, and furcation regions.

-Has a reparative and compensatory function.

what do principal PDL fiber bundles do?
attach tooth to alveolar bone proper
What are Sharpey's fibers?
Where PDL fiber bundles are mineralized in cementum or bone.
How are PDL fibers attached to teeth?
Cementoblasts insert tufts of collagen into predentin. Then fibroblasts attach PDL fibers to this fibrous fringe.
Why is Vitamin C important?
It is required to make but not to degrade collagen. When a person has scurvy the PDL fibroblasts degrade the collagen but do not make new collagen.
How are PDL fibroblasts different from regular fibroblasts?
Motile with well developed cytoskeleton and myofibroblastic like. They are stimulated by mechanical stress to produce collagen. They form contacts with each other and the fiber bundles . Make and degrade collagen.