Oral Biology Exam 1

What is growth?

increase in size or number, rate of growth varies

How do meckel's cartilage and the maxillary process develop?

membranous ossification

What period is the growing embryo least susceptive to environmental factors and acquired defect formation?

proliferative period (0-2 weeks)

What week do the primary brain vesicles form (forebrain, midbrain, hindbrain, cerebral hemispheres)?

3rd week

What are the three phases of the proliferative period?

1. fertilization
2. implantation
3. embryonic disk formation

What is present in week 1 of development?

bilaminar disc from cells of zygote, ectoderm, endoderm (2 layers)

What does the endoderm form?

GI tract epithelium and associated glands

what does the ectoderm form?

nervous system, skin, tooth enamel, glands

What are the phases of week 2 development?

gastrulation, formation of mesoderm, trilaminar disc, becomes embryo after week 2

What does the mesoderm form?

muscles, CT derivatives (bone, cartilage, blood, dentin, pulp, cementum, PDL)

What week does the heart start to beat?

4th week

When does the face and oral structures form?

weeks 4-7

When does the face begin to appear more human?

week 8-14

What is happening during week 3?

neurolation (CNS) --> formation of neural tube --> differentiation of neural crest cells --> migrate laterally and ventrally towards area of future face

What does the neural tube become?

brain and spinal cord

When do the cranial nerves begin development and growth into tissues?

weeks 4-5

What happens in fetal alcohol syndrome?

effects stage 1 (initial organization of germ layers)

first three ventricles of brain fail to separate

olfactory placodes too close together (deficient median nasal prominence)

vary from total absence of nose to mid face deficiency

What does the foregut - upper part become?

digestive tube from throat to duodenum

What does the midgut - middle part become?

small intestine, cecum, ascending colon, most of transverse colon

what does the hindgut become?

sigmoid colon, rectum

What is present during the 4th week in terms of facial development?

frontal prominence (forehead), maxillary processes, stomodeum (oral cavity), mandibular processes, nasal pits

When do the maxillary processes fuse with the intermaxillary segment?

by 10th week

What is the oral pit?

pit between brain and heart

When does the oropharyngeal membrane rupture?

5th week --> due to apoptosis

What is the oropharyngeal membrane? (what does it form)

forms opening to oral cavity to tubular foregut becoming theroropharynx

ectodermal lining of oral mucosa

What is the mandibular arch doing during the 5th week?

growing laterally to oral pit --> develops into maxillary process (cheeks) and mandible

What happens during weeks 5-6?

facial processes continue to migrate, development of nose and nostrils, eyes and external ears become more evident, mandible begins ossification during late 6th week

What do neural crest cells do?

contribute to oral-facial structures, tooth and periodontium formation

Where do neural crest cells migrate to?

epithelial areas with specific homeobox genes in high concentration

What happens during the fetal period?

tissues enlarge, differentiate, function

What happens during weeks 10-14 in terms of the face?

it is getting narrower

When do most major malformations of the craniofacial complex originate? (when what is growing?)

during transformation of the brachial apparatus into its adult derivative (pharyngeal arches development)

Where are the pharyngeal arches located?

bars of tissue at the lateral aspect of the future neck

What does a pharyngeal arch contain?

bar of cartilage, artery, cranial nerve, and mesodermal tissue

What are pharyngeal grooves or clefts?

vertical grooves separating each arch eternally (develop in 5th week)

When do the pharyngeal grooves appear?

during 5th week

features of the 1st pharyngeal arch? (what is it called?, what does it form?, what is it covered by?)

mandibular arch

forms bony mandible, muscles of mastication, nerves and blood supply

covered by ectoderm externally and internally

features of the 2nd pharyngeal arch? (what is it called?, what does it form?, what is it covered by?)

"hyoid" arch

forms facial muscles and vessels, hyoid bone

covered by ectoderm externally and internal anterior area

Features of the 3rd, 4th, and 5th pharyngeal arches?

paired bilateral bars divided before they reach midline by the presence of bulging heart

form hyoid bone, thyroid, and cricoid cartilages

When do pharyngeal arches 2-5 develop?

between weeks 4-7

which arch vessel becomes the dorsal aorta?

4th arch vessel

What are the 1st arch muscles? when do they appear?

appear in 5th week

masseter, medial and lateral pterygoid, temporalis (muscles of mastication)

When do the 2nd arch muscles appear? what are the muscles?

by 10th week

muscles of facial expression

What are the 4th arch muscles?

pharyngeal constrictor muscles in neck enclosing pharynx

What cartilage is located in the 2nd arch?

reichert's cartilage

stapes, styloid process, lesser horn of hyoid

What cartilage is located in the 3rd arch?

greater horn and lower part of hyoid

What cartilage is located in the 4th arch?

contributes to hyoid cartilage

What cartilage is located in the 5th arch?

no adult cartilage derivatives

What cartilage is located in the 6th arch?

laryngeal cartilage

What does the 1st pharyngeal pouch become?

middle ear and Eustachian tube

What does the 2nd pharyngeal pouch become?

palatine tonsils

What does the 3rd pharyngeal pouch become?

inferior parathyroid and thymus glands

What does the 4th pharyngeal pouch become?

superior parathyroid glands

What does the 5th pharyngeal pouch become?

ultimobranchial body --> fuses with thyroid gland, provides parafollicular cells to thyroid

What are pharyngeal grooves 2-5 covered by after the 5th week?

arches 2 and 5

What do accessory pouches form?

cysts

What three things lead to the tongue formation? what week?

5th week

lateral lingual swellings, tubercular impar, copula (fuse together)

Where does the thyroid gland start and where does it end up during development?

starts at the foramen caecum and ends near the tracheal rings

What are thryoglossbal cysts or fistulas? (what are they made of)

leftover bits of thyroid gland during migration

What is intramembranous bone formation?

bone formation from undifferentiated mesenchymal cells

form directly from CT and not from cartilage precursor

When does the first evidence of cartilage conversion to bone occur?

week 8

When is peak cartilage development occurring?

3rd month Interutero

When is there in-growth of vascular elements?

4th month interutero

When is the first evidence of bone formation in the mandible?

week 6

When do centers of ossification appear in calvarial and facial regions?

week 8 --> in areas where mild tension forces are present

Which bones are formed by intramembranous ossification?

upper cranial vault and facial bones

Which bones are formed by endochondrial ossification?

bones of cranial base and portions of the temporal and occipital bone

Where do the maxillary bones grow?

medially into the palate

Where does the mandible grow?

laterally to the 1st arch cartilage

How is the palate formed?

formed by movement of maxillary bones and medial nasal processes

When does the palate start to fuse?

8th week

When does the palate fuse with the nasal septum?

12th week

What is hemifacial microsomia? (what causes it?, where is it found? what does it lead to?)

lack of tissue on affected side of face

usually in area of ramus and ear

early loss of neural crest cells

cleft lip/palate, renal abnormalities

What is a harelip?

midline cleft of maxilla

How do mandibular clefts form? (and when?)

during 4th week

rare -> due to pressure from heart beating before mandible's midline fusion

How does cleft lip form?

Failure of fusion of maxillary and medial nasal processes --> nasal fin connection had bad migration of CT to fill area --> tissue stretched and breaks down resulting in separation

How does a unilateral cleft lip form?

lack of CT migration between one maxillary process and the fused medial nasal process

How does a bilateral cleft lip form?

lack of CT migration between both maxillary processes and the fused medial nasal processes

usually includes outward protrusion of midline of lip and primary palate

What is a globulomaxillary cyst?

cyst that lies between the primary palate and palatal shelves --> between maxillary lateral and canine

--> during fusion of shelves, CT replaces epithelium but if some become trapped they become epithelial rests, rest cells may clump up and form cyst (becomes fluid filled)

What are the types of cleft palates?

complete (soft and hard palate), incomplete (hole in roof of mouth)

What is usually split if a cleft palate occurs?

the uvula

what is a unilateral cleft palate?

when only one of the two palatal processes fuse with the nasal septum --> opening from oral cavity into one side of nasal cavity

what is a bilateral cleft palate?

neither palatal processes fuse with opposing processes or nasal septum

opening from the oral cavity to both sides of nasal cavity

V shaped cleft, widening at posterior end

When does a palatal cleft occur during development?

between weeks 7-11

when does the "zipper" close between the maxillary processes and the primary palate?

from week 7/8 to week 11

When is surgery done to fix cleft lips?

within 2-3 months after birth

How is the cleft palate fixed?

with a palatal obturator --> prosthetic device that covers the gap temporarly

surgery between 9 to 18 months (Latham appliance, screw daily)

What is the order of development of different tooth parts (dentin, root, enamel)

dentin --> enamel --> root

T/F The development process is different for all teeth

false --> the development process is the same

What surface of the tooth forms first?

incisal/occlusal

When does root formation begin and end?

begins: with eruption of tooth
ends: apical closure

What cells are involved in tooth development?

oral ectodermal cells, underlying mesenchymal cells, (+neural crest cells --> stimulate mesenchymal cells)

What are the stages of crown formation and mineralization?

bud stage, cap stage, bell stage

What happens during the bell phase of tooth development?

differentiation of odontoblasts and ameloblasts

dentinogenesis: dentin formation
amelogenesis: enamel formation

What happens during root formation and mineralization?

form dentin, cementum, alveolar bone, PDL

Which week does the first sign of tooth development and dental lamina formation occur?

6th week

What is the dental lamina?

primary epithelial band

continuous band of thickened oral epithelium (ectoderm)

epithelial extensions into underlying mesenchyme

where does the dental lamina develop?

at site of developing dental arches of the maxilla and mandible

What does the primary epithelial band subdivide into?

dental lamina --> dentition
vestibular lamina --> vestibule (forms right after dental lamina)

Which way does the primary epithelial band spread?

anterior to posterior