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Embryology Definitions


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Name the 3 periods of pre-natal development.
When does pre-implantation occur?
1st week
When is the embryonic period and what happens?
2nd week to the end of 8th week. Major development of body structure, cells change into tissues and organs (differentiate), and cells form systems (integrate)
What are the 3 embryonic layers and when are they formed?
Explain ectoderm
Outer layer that forms the brain, spinal cord, skin and appendages, enamel, and lining of oral cavity
Explain mesoderm.
Middle layer that forms bones, muscles, circ. system, kidneys, ducts, reproductive system, abdominal lining, dentin, pulp, cementum
Explain endoderm.
Inner layer that forms the digestive system lining, lining of lungs, parts of the urogenital system.
When does the 1st pair of brachial arches get formed?
week 4
What is the 1st brachial arch comprised of?
bones, muscles, nerves, lower lip, masticatory process, anterior of alveolar process
What is another name for the 2nd brachial arch?
What is the 2nd brachial arch, or hyoid, comprised of?
stapes of ear, styloid process (forms base of temporal), side and front of neck, muscles of facial expression (MOBZ)
The palate forms in 3 stages, what are they?
Primary palate
Secondary palate
When is the hard and soft palate differentiated?
week 5 to 8 (primary dentin has begun, number of teeth, and arrangement)
When is the fetal period and what happens?
week 9 to 38. Systems continue growth, fetus is less vulnerable to malformation
What is odontogenesis?
The life cycle of a tooth.
What are the 3 stages of odontogenesis?
1. Grow
2. Calcification
3. Eruption
Explain the bud stage of tooth growth.
-Tooth pattern is formed
-dental lamina makes curves in each arch for the buds of primary teeth
-by week 17 all 20 primary teeth are formed
Explain the cap stage of tooth growth.
Cells increase and grow to different steps and sizes depending on the tooth
Explain the bell stage of tooth growth.
Epithelial cells become ameoblasts
Peripheral cells become ________________.
Inner cells of the dental sac become _______________.
What is morphodifferentiation?
the process where the basic shape and size of each tooth is established.
What is calcification?
The hardening of material.
A _____ is the point where 2 developmental grooves cross over.
A _________ is the incomplete joining of the lobes during development.
What is eruption?
The movement of teeth into the functional position in the oral cavity.
All teeth (primary and permanent) erupt, but only the primary teeth ___________.
What teeth erupt at about
6 to 10 months?
Upper and lower centrals.
What teeth erupt at 7 to 10 months?
Lower laterals
What teeth erupt at 9 to 12 months?
Upper laterals
What teeth erupt at 12 to 18 months?
Upper and lower 1st molars.
What teeth erupt at 16 to 22 months?
Upper and lower canines.
What teeth erupt at 20 to 32 months?
Lower 2nd molars.
What teeth erupt at 24 to 32 months?
Upper 2nd molars.
What teeth exfoliate at 6 to 7 years?
Upper and lower centrals.
What teeth exfoliate at 7 to 8 years?
Upper and lower laterals.
What teeth exfoliate at 9 to 11 years?
Upper and lower 1st molars.
What teeth exfoliate at 9 to 12 years?
Lower canines.
What teeth exfoliate at 10 to 12 years?
Upper canines and upper and lower 2nd molars.
What teeth erupt at 6 to 7 years?
Upper and lower 1st molars and lower centrals.
What teeth erupt at 7 to 8 years?
Upper centrals and lower laterals.
What teeth erupt at 8 to 9 years?
Upper laterals.
What teeth erupt at 9 to 10 years?
Lower canines.
What teeth erupt at 10 to 12 years?
Upper and lower 1st and 2nd pre-molars.
What teeth erupts at 12 to 13 years?
Upper and lower 2nd molars and upper canines.
What teeth erupt at 17 to 21 years?
Upper and lower 3rd molars. (wisdom teeth)
What are succedaneous teeth?
Permanent teeth that replace the primary teeth.
What are the non-succedaneous teeth?
1st, 2nd, and 3rd upper and lower molars.
What is micrognathia?
An abnormally small jaw. (usually results in a Class 2 occlusion)
What is macrognathia?
An abnormally large jaw. (usually results in a Class 3 occlusion)
What is microdontia?
Abnormally small teeth.
What is macrodontia?
Abnormally large teeth.
What are supernumary teeth?
Teeth in excess of 32.
What is dens in dente?
"Tooth within a tooth" (a cluster of enamel and dentin in the pulp)
What are pegged-shaped associated with?
Also known as Hutchinson's Incisors. Associated with maternal syphillis.
What is fusion?
When the dentin and enamel of one tooth are joined with 2 or more = reduced number of teeth in the arch.
What is gemination?
When a tooth bud tries to divide and when it fails, the result is an incisal notch.
What is amelogenesis imperfecta?
Defects in the enamel formation formation (hereditary)
Define hypocalcification.
Incomplete hardering of the enamel.
Define attrition.
The normal wearing away of tooth structure. The first sign of attrition is the wearing of mamelons.
Define abrasion.
Abnormal wearing of teeth.
Define impaction.
Tooth remains unerupted.
-premature loss of baby teeth
-developing tooth shifts horizontally
-teeth shifts because of other tooth in space or lack of jaw space or large crowns.
Define bruxism.
Involuntary grinding or clenching of teeth.
What is erosion?
Wearing of lingual surfaces caused from stomach acids; usually seen in those with bulimia.
What can various head/neck infections be caused by?
Orofacial piercings.
Define exostoses.
Also known as tori or torus.
In plate - torus palatinus
Lower lingual - torus mandibularis (near the premolar/molar area)
Both are benign bony overgrowths.
Describe cleft lip.
When the maxillary and medial nasal processes do not fuse.
Describe cleft palate.
When the palatal shelves do not fuse with the primary plate (incisive papilla area)
Describe cleft uvula.
Covered with mucous membrane and looks like a bony projection in the center or middle of the hard palate.
Define ankylglossia.
"tongue-tie" A short lingual frenum is extended to the tip (apex) of the tongue.
Define glossitis.
General term for inflammation of the tongue.
Describe pernicious anemia.
The body is not able to absorb vitamin B12 (ie seafood, meats, milk)
S&S: anemia, pallor, fatigue, nausea, diahhrea, abdominal pain, loss of appetite.
Define fissured tongue.
Tongue appears to have deep grooves on dorsum. May be caused from vitamin deficiency or chronic trauma.
What is a geographic tongue?
Loss of filiform papillae. Results in smooth patches. More common in women.
Define black hairy tongue.
After antibiotics, papillae are elongated (due to oral flora imbalance)and become stained with food, tobacco, etc.
What is atrophic candidias?
After broad spectrum of antibiotics, mouth feels like its been burned; antifungal therapy should clear it in 14 days.
Define candidias (of soft tissue)
Most common oral-fungal infection. Initial clinical manifestation in pts with AIDS.
What is morphology?
The study of the shape and form of teeth.
Which tooth has the longest root?
Cuspids (also known as canines)
Name the 5 tooth surfaces.
Occlusal (incisal)vestibular, labial, facial), lingual, mesial, distal
Where is the greater palatine foramen?
On either side of the soft palate.
Where is the incisive foramen?
Under the incisive papilla.
What is histology?
The study of the structure and function of the teeth and oral tissue.
Describe the crown of the tooth.
Dentin and pulp covered by enamel.
Describe the root.
Has dentin and pulp covered by cementum.
What is the anatomic crown?
Part of the tooth that is covered by enamel.
What is the clinical crown?
Part of the tooth that is visible.
The root is usually embedded in the _________ ___________.
alveolar process
What is bifurcation and trifurcation?
Bifurcation is the division into 2 roots. Trifurcation is the division into 3 roots.
Define apex.
The tapered end of each root.
Where is the apical foramen?
At the opening of each root apex.
Define the periapical area.
Consists of anything surrounding the apex.
Name the tissues of the tooth.
Enamel, dentin, pulp, cementum
Describe enamel.
-makes up the anatomic crown
-hardest material in the body
-crushing strength of 100,000 psi.
-formed by ameloblasts
-96-99% inorganic, 1-4% organic
-composed of prisms (enamel rods)
Describe dentin.
-makes up bulk of tooth
-covered by enamel on the crown and cementum on the root.
-supports the enamel
-formed by odontoblasts
-contain dental tubules
-capable of continued growth and repair
What are the types of dentin?
Primary-formed before eruption
Secondary-formed after eruption and continues slowly
Tertiary-reparative, formed in response to irritation
Describe pulp.
-inner portion of the tooth pulp chamber
Define coronal pulp.
Pulp that is in the crown.
Define radicular pulp.
Pulp in the root portion. Made up of nerves and blood vessels.
What are fibroblasts?
Cells that form the pulpal tissue
Describe cementum.
-rigid (bone-like) connective tissue
-covers the root
-NOT shiny
-formed by cementoblasts
What is the difference between osteoclasts and osteoblasts?
Clasts resorb bone and blasts build bone.
What is the periodontium divided into?
Attached apparatus (cementum, alveolar process, and periodontal ligaments)
Gingival unit (lining mucosa, masticatory mucosa, and specialized mucosa)

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