Lecture 8: Prenatal Development, Development Orofacial Structures

pre-implantation, embryonic, fetal

what are the 3 periods of prenatal development?

pre-implantation - 1st trimester, embryonic period - 1st trimester, fetal period - 2nd & 3rd trimester

what are the trimesters for each prenatal development period?

preimplantation period

1st week after conception; zygote develops into a blastocyte; takes one week to occur

ectopic pregnancy

what can go wrong during preimplantation period?

embryonic period

beginning of 2nd week to end of 8th week; developmental processes occur

induction

action of one group of cells on another

proliferation

controlled cellular growth and accumulation of byproducts - interstitial growth/appositional

diferentiation

change in identical embryonic cells to become distinct (structurally and functionally) to perform specialized functions - effects cells, tissue types, organs and systems

morphogenesis

the process of development of specific tissue structure or shape; complexity of structure and function of cells increases

maturation

attainment of adult function and size of tissues and organs due to processes of proliferation, differentiation and morphogenesis

bilaminar embryonic disc

developed from blastocyst, appears as a 3-D flattened, circular plate of bilayered cells; contains superior epiblast layer and inferior hypoblast layer; will develop into embryo later

primitive streak

forms during the beginning of the 3rd week within bilaminar disc; cells from epiblast layer will move toward the hypoblast layer

trilaminar embryonic disc

what is it called the embryonic disc called now that three layers are present?

endoderm layers

digestive system; liver; pancreas; lungs (inner layers)

mesoderm layer

circulatory system; lungs (epithelial layers); skeletal system; muscular system

ectoderm layer

hair; nails; skin; nervous system

ectoderm

epithelium of outer body, columnar; nervous system; epithelium lining - oral and nasal cavity

enamel

what does ectoderm form?

mesoderm

migrating cells from epiblast layer; kidneys, skeletal system, muscles, blood/lymph cells

dentin, cementum, pulp, pdl, alveolar process

what does mesoderm form?

endoderm

hypoblast layer, cuboidal; epithelial lining of GI tract

4-12 weeks

how long for development of face?

mandibular

what does 1st arch produce?

hyoid

what does 2nd arch produce?

glossopharyngeal, stylopharyngeal

what does 3rd arch produce?

stomodeum

primitive mouth

6 brachial arches

how many brachial arches form below stomodeum?

1st brachial arch

mandibular arch; buddings on both ends of this form 2 maxillary processes while the remaining becomes the mandibular process

frontonasal process

invaginations of this divide into the medial nasal process and R/L lateral nasal processes

ala of nose

what does lateral nasal processes become?

globular process and center of upper lip

whaat does medial nasal process become?

upper lip

what does R/L maxillary processes become?

meckel’s cartilage - important in formation of mandible

what does 1st brachial arch contain?

1st brachial arch

trigenial nerve V; muscles of mastication; meckel’s cartilage

2nd brachial arch

facial nerve VII; muscles of facial expression; Reichert’s cartilage

ectodermal dysplasia

abnormal development of one or more structures from ectoderm; may be partial/complete anodontia

rubella

causes cataracts, deafness or damage to heart or brain in the unborn infant

fetal alcohol syndrome

crowding of teeth, mouth breathing, anterior open-bite

syphilis

produces defects in the incisors and molars (mulberry molar)

tetracycline stain

intrinsic yellow-brown stain, chemically bound to dentin and becomes transparent in the enamel; can occur in primary/permanent teeth

5th week

when does palate development start?

2 maxillary processes, globular process

what are the 3 sources that the palate arises from?

intermaxillary segment

internal wedge-shaped mass that extends inferiorly and deep to the nasal pits on the inside of the stomodeum

week 5-6

when does primary palate formation occur?

primary palate formation

intermaxillary segment forms from fusing 2 medial nasal processes; develops into floor of the nasal cavity and nasal septum; also gives rise which will form premaxilla - anterior 1/3 of hard palate

secondary palate

produces posterior 2/3 of the hard palate, soft palate uvula, nasal septum

secondary palate formation

primary palate and secondary palate fuse roof of the mouth - forms “y” shape; fusion gives rise to medial palatine raphe and deeper median palatine suture

week 12

when does complete formation of palate occur?

week 4

when does development of the nose occur?

medial nasla processes

these processes fuse together externally to form middle part of nose, tubercle of upper lip, philtrum

lateral nasal processes

form ala of the nose

lateral nasal, maxillary and medial nasla processes

which processes form the nares?

cleft lip

partial or complete failure of fusion of 1 or both maxillary processes with the medial nasal processes; rare in the mandible; left side is most common

cleft palate

failure of lateral palatine processes to fuse with each other or with the premaxilla; exposes nasal cavity to the oral environment; high hereditary influences

week 4

when does tongue begin to develop?

body of tongue

develops from the 1st branchial arch

base/root of tongue

develops from 2nd, 3rd and 4th branchial arch

tuberculum impar

swelling begins

lateral lingual swellings

develops on each side of the tuberculum impar

medial lingual sulcus

line of demarcation of fusion of the two lateral swellings

copula

behind fused anterior swellings; will form the base of the tongue (posterior 1/3)

week 8

when does complete development of tongue occur?

5-12 week

duration of palatal development

5-12 week

duration of nasal septum development

4-8 week

duration of tongue development

macrostomia

extremely large mouth opening resulting from a failure of fusion of the maxillary process and mandibular arch at corners of the mouth

microstomia

extremely small mouth opening resulting of the merging of the maxillary process and mandibular arch at the corners of the mouth