Oral Biology Exam 1

What is growth?

increase in size or number, rate of growth varies

What is development?

increase in the degree of organization and/or functional complexity

continues throughout life

What period (weeks) are critical for the formation of the oral cavity and face?

4th-14th week of intrauterine life (embryo to fetus stages)

What does the maxillary process of the 4th week embryo turn into?

maxilla

what does meckel's cartilage form?

mandible

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

membranous ossification

What weeks are considered the proliferative period?

0-2 weeks --> cell division

What weeks are considered the embryonic period?

2nd to 8th weeks

What weeks are considered the fetal period?

8th week-birth

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

proliferative period (0-2 weeks)

What week do neural folds appear?

3rd week

Week the neural tube closes?

3rd week

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

3rd week

Which weeks are most critical for serious malformations and have a high susceptibility to environmental factors?

3th-8th week --> structures are developing

Which period has declining susceptibility to malformations?

8th week-birth

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 happens during the embryonic period?

development of tissues, organ systems

What week does the heart start to beat?

4th week

When does the face and oral structures form?

weeks 4-7

When does the fetal period begin

week 8

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

When does the mandibular processes fuse?

by end of 4th week

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

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

What does the stomodeum become?

oral cavity

When do the maxillary processes fuse with the intermaxillary segment?

by 10th week

When does the oral pit first appear?

4th 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

What happens when neural crest cells migrate to areas with high homeobox genes? low homeobox genes? (in terms of teeth)

high: supernumerary teeth
low: missing teeth

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 does the face look like during weeks 4-8?

add picture

What does the face look like during weeks 10-14?

add picture

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

What are the pharyngeal pouches?

grooves that separate arches within pharynx, match external grooves

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

What cranial nerve innervates the 1st pharyngeal arch? (mandibular arch)

trigeminal (V)

What cranial nerve innervates the 2nd pharyngeal arch?

facial nerve

What cranial nerve innervates the 3rd pharyngeal arch?

glossopharyngeal nerve

What cranial nerve innervates the 4th and 5th pharyngeal arch?

vagus nerve

What kind of vessel do the pharyngeal arches initially contain? (for their blood supply)

right and left aortic arch vessel

which arch vessel becomes the common carotid artery?

3rd arch

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 1st arch?

meckel's cartilage

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 groove become?

external auditory canal

What does the 1st pharyngeal groove + 1st pharyngeal pouch become?

tympanic membrane

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 endochondrial bone formation?

from cartilage precursor, conversion of cartilage to bone

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