Histo Review From Exams 1 And 2

Front 1

What is a blastocyst composed of?

Back 1

inner cell mass and trophoblast

Front 2

What does the inner cell mass become?

Back 2

embryo

Front 3

What does the trophoblast become?

Back 3

placenta

Front 4

What does the prochordal plate consist of?

Back 4

epiblast and hypoblast (sometimes calls the embryonic ectoderm and embryonic endoderm). It is present in the head end of the embryonic disc

Front 5

After the head fold happens what does the prochordal plate become?

Back 5

the buccopharyngeal membrane

Front 6

What is the trilaminar disc made up of?

Back 6

Ectoderm, endoderm, and mesoderm. It is a product of gastrulation and the primitive streak is present.

Front 7

Where is the primitive streak found?

Back 7

In the trilaminar disc. In the epiblast layer.

Front 8

What does the mesenchyme from the primitive steak form?

Back 8

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.

Front 9

What is the notochord and what is it derived from?

Back 9

It is a cord of mesoderm along the midline between the primitive node and prochordal plate. Derived from the cells of the primitive node.

Front 10

What does the notochord become in a fully formed fetus?

Back 10

Most of it degenerates but some of it becomes the nucleus pulposas of the intervertebral discs.

Front 11

What signaling function does the notochord have?

Back 11

Sonic hedgehog signaling function inducing formation of the CNS.

Front 12

What does the ectoderm become?

Back 12

Enamel (oral epithelium, dental lamina, enamel organ), skin, CNS, nasal epithelium, hair, nails

Front 13

What are neural crest cells?

Back 13

A temporary group of cells derived from the ectoderm.

Front 14

What do cephalic neural crest cells give rise to?

Back 14

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,

Front 15

What is derived from the dental papilla?

Back 15

dentin and pulp

Front 16

What is derived from the dental follicle?

Back 16

alveolar bone, PDL, cementum

Front 17

What do the cephalic and trunk neural crest cells become?

Back 17

Peripheral neurons and ganglia, melanocytes, and Schwann cells.

Front 18

What does mesoderm become?

Back 18

muscles, bones (not including those derived from neural crest cells), kidneys, gonads, and spleen.

Front 19

What does endoderm become?

Back 19

thyroid, lungs, liver, linings of gut (including pharynx and pharyngeal pouches) and respiratory tract.

Front 20

Where does the anterior palate come from?

Back 20

ingrowth of intermaxillary segment

Front 21

Where does the posterior palate come from?

Back 21

Comes from ingrowth and fusion of lateral palatine processes of the maxillary prominences

Front 22

Where does the intermaxillary segment come from?

Back 22

Comes from fusion of medial nasal prominences , which come from frontonasal prominence. It does NOT come from an arch.

Front 23

Where does the medial nasal prominence come from?

Back 23

From the frontonasal prominence.

Front 24

In order for the palate to form what must happen to the lateral palatine processes?

Back 24

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.

Front 25

What has been shown to result in palatal malformations?

Back 25

Loss of expression of Msx-1

Front 26

What are derivatives of Meckel's cartilage?

Back 26

Malleus, incus, anterior ligament of the malleus, sphenomandibular ligament. NOT mandible or maxilla.

Front 27

The tongue is made from derivatives of which arches?

Back 27

1st, 2nd, 3rd and 4th

Front 28

What forms the epithelial covering of the tongue?

Back 28

dorsal surface of anterior part: lateral lingual swellings

dorsal surface of posterior part: hypobranchial eminence

Front 29

How is the tongue made?

Back 29

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.

Front 30

Where does the signal that initiates tooth development come from?

Back 30

oral epithelium (ectoderm)

Front 31

Where does the signal that directs tooth type come from?

Back 31

Ectomesenchyme

Front 32

What is Hertwig's epithelial rooth sheath

Back 32

An extension of the inner and outer enamel epithelium after the crown is formed. It is NOT present during the bell stage.

Front 33

What does the Hertwig's epithelial root sheath do?

Back 33

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.

Front 34

After Hertwig's epithelial root sheath break down, what does it leave?

Back 34

Epithelial cell rests of malassez in the PDL.

Front 35

Where do ameloblasts come from?

Back 35

Differentiate from the inner enamel epithelium of the enamel organ (ectoderm)

Front 36

During the secretory stage what is the level of mineralization of enamel?

Back 36

30%-It is immediately mineralized to this amount

Front 37

What is the enamel matrix made from?

Back 37

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.

Front 38

What is the composition of mature enamel?

Back 38

96% mineral (hydroxyapatite)

1-2% organic material (mostly TRAP)

2% water

Front 39

Where can you find rodless enamel?

Back 39

At the DEJ and surface of the tooth. It is thicker at the surface in primary teeth than secondary.

Front 40

What is the Tomes process associated with?

Back 40

The formation of structured enamel. It is present during the secretory stage. Gives the ameloblast a picket fence appearance under the microscope.

Front 41

How are crystals in the rod core oriented?

Back 41

Parallel to the long axis and tightly packed.

Front 42

Where is much of the organic material in the enamel found?

Back 42

In the rod sheath.

Front 43

What is the rate of formation of primary dentin?

Back 43

Primary dentin (mantle and circumpulpal dentin) is formed at a rate of 4 microns per day as root and crown are developing.

Front 44

When is secondary dentin formed?

Back 44

After teeth come into functional occlusion. It can be recognized by a bend in the tubules near the pulp chamber of a mature tooth.

Front 45

What is the level of mineralization of dentin?

Back 45

70% mineral (hydroxyapatite)

Front 46

What is intertubular dentin?

Back 46

It is the organic matrix of dentin that is located between the dentinal tubules. Mostly made up of type I collagen.

Front 47

How does mineralization occur in mantle and circumpulpal dentin?

Back 47

mantle: By matrix vesicles

-linear pattern of mineralization

circumpulpal: heterogenous nucleation

-globular pattern of mineralization may be seen

Front 48

What is interglobular dentin?

Back 48

Hypomineralized regions associated with the globular pattern

Front 49

Which dentin is hypermineralized and where is it located?

Back 49

Peritubular dentin: formed inside of the tubule. It does not have a collagen matrix.

Front 50

What type of nerve fibers are located in the pulp?

Back 50

Both afferent and sympathetic fibers

Front 51

What is dentinal sensitivity thought to be due to?

Back 51

Fluid movement through the tubules that stimulates the afferent nerve fibers in the plexus of Raschkow.

Front 52

What may be the role of pulp innervation?

Back 52

Pulpal homeostasis

Front 53

What is the mineralization of cementum and what is the bulk of the organic matrix made from?

Back 53

~50% hydroxapatite

-organic is mostly type I collagen

Front 54

Where do cementoblasts come from?

Back 54

From follicle after breakdown of HERS.

Front 55

What are the two histological types of cementum?

Back 55

-acellular cementum with extrinsic fibers from the PDL

-cellular cementum with intrinsic fibers from cementoblasts

Front 56

What is acellular cementum?

Back 56

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

-Has an attachment function

Front 57

What is cellular cementum?

Back 57

-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.

Front 58

what do principal PDL fiber bundles do?

Back 58

attach tooth to alveolar bone proper

Front 59

What are Sharpey's fibers?

Back 59

Where PDL fiber bundles are mineralized in cementum or bone.

Front 60

How are PDL fibers attached to teeth?

Back 60

Cementoblasts insert tufts of collagen into predentin. Then fibroblasts attach PDL fibers to this fibrous fringe.

Front 61

Why is Vitamin C important?

Back 61

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.

Front 62

How are PDL fibroblasts different from regular fibroblasts?

Back 62

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.