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Oral Biology > QUIZ I General Embryology > Flashcards

QUIZ I General Embryology Flashcards

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1
Q

what is embryology?

A

the study of prenatal development

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2
Q

what is prenatal development?

A

begins with the start of pregnancy and continues until birth

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3
Q

what trimesters do the preimplantation, embryonic, and fetal periods make up?

A
  • preimplantation and embryonic periods - first trimester
  • fetal period - second and third trimesters
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4
Q

each craniofacial structure has what?

A

a primordium - the earliest indication of a tissue or an organ during prenatal development

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5
Q

what are the steps of development from the zygote to the fetus?

A

zygote → blastocyst → blastocyst to disc → disc to embryo → fetus

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6
Q

when do the major events of prenatal development occur?

A

first, second, third, and fourth weeks

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7
Q

describe the general steps of prenatal development

A
  • fertilization and formation of the zygote
  • mitosis leads to formation of the blastocyst, which forms a fluid filled vesicle and implants in the uterine wall
  • the blastocyst gives way to a disc and begins to differentiate into 3 distinct germ layers
  • these germ layers form the embryo and ultimately, fetus
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8
Q

describe factors driving development

A
  • growth factors and cell adhesion molecules act through signaling complexes which activate various transcription factors, affecting cellular changes
    • changes might be proliferation, differentiation, or apoptosis
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9
Q

growth factors driving development can act through which modes of action?

A

autocrine, paracrine, or endocrine

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10
Q

___ is a critical growth factor in craniofacial development

A

bone morphogenic protein (BMP)

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11
Q

at gastrulation, BMP switches between ___ vs ___ fate

A

epidermal vs. neural fate

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12
Q

what are the functions of BMP?

A
  • induction, formation, determination, and migration of neural crest cells
  • patterning and formation of facial primordia
  • craniofacial skeletogenesis (later roles in maintenance)
  • negative regulator of myogenesis (makes bone instead of muscles)
  • regulator of early tooth morphogenesis and differentiation
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13
Q

what are 4 types of genes involved in the control of embryonic formation?

A
  • HOX genes
  • Msx genes
  • DIx genes
  • Shh (sonic hedgehog) genes
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14
Q

what is the function of HOX genes?

A

function in patterning the body axis and determine where limbs and other body segments will grown in developing foetus

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15
Q

what is the function of Msx genes?

A

control cellular process of differentiation and proliferation during development

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16
Q

what is the function of DIx genes?

A
  • control development of ectodermal tissues derived from lateral border of the neural plate
    • control patterning of the branchial arch skeleton
    • also expressed in developing bone and regulate limb development
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17
Q

what is the function of Shh genes?

A

play an important role in early induction of facial primordium

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18
Q

what do homeobox genes code for?

A
  • transcription factors that begin to make cells pattern into one tissue/organ type or another
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19
Q

homeobox genes are involved in ___ ___ during embryonic development

A

bodily segmentation

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20
Q

homeobox genes are key regulators of what?

A

embryogenesis

help regulate which end is going to be which

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21
Q

what type of DNA sequence is the homeobox gene?

A

180 bp DNA sequence

homeodomain in protein

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22
Q

___ genes typically switch on cascades of other genes

A

homeobox

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23
Q

what type of cell adhesion molecules do neurectoderm and skin ectoderm progenitors express?

A
  • neurectoderm
    • N-CAM
  • skin ectoderm
    • L-CAM
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24
Q

____ is hugely important for positioning and differentiating

A

cell-cell contact

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25
Q

cell adhesion molecules are responsible for what?

A

specific cell aggregation and sorting

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26
Q

which cell adhesion molecules are calcium dependent? calcium independent?

A
  • calcium dependent
    • cadherins
  • calcium independent
    • CAM
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27
Q

describe the fertilization phase of the preimplantation period

A
  • first period of prenatal development; occurs during the first week after conception
  • ovum is penetrated by sperm
  • fusion of 2 haploid gametes gives the full diploid complement of 46 (zygote)
  • cell division (mitosis) occurs to form the blastocyst
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28
Q

many human disorders can be traced to changes in what?

A

structures or number of chromosomes

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29
Q

describe the cleavage phase of the preimplantation period

A
  • occurs after fertilization when the zygote undergoes mitosis (aka individual cell division or cleavage)
  • morula (solid ball) is formed after initial cleavage
  • zygote becomes blastocyst
  • further mitotis cleavages, with little to no differentiation involved
  • lasts until 3 distinct germ layers have formed
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30
Q

describe implantation

A
  • blastocyst stops traveling by the end of the first week
  • it implants in the endometrium
    • implantation
    • typically on the back wall
31
Q

list the summary of events during the first week after fertilization

A
  • rapid proliferation
  • migraiton of cells
  • realignment of cells
  • fluid filled cavity
  • embryoblast (inner cell mass)
    • forms the embryo proper
  • trophoblast
  • implantation/placenta
32
Q

when does the embryonic period occur?

A

beginning of week 2 to the end of week 8

33
Q

what occurs during the embryonic period?

A
  • important spatial and temporal events called patterning
    • includes formation of the pharyngeal arches, somite development, face development, palate and tongue formation, and other critical events
34
Q

describe patterning during the embryonic phase

A
  • key process in normal development
  • axial specification (which end is up)
  • segmentation (what forms between each end)
  • tissue and organ specialization and formation begins
  • development of dentition begins
    • regional development of incisors, canines, pre-molars, and molars
35
Q

what 5 steps are involved in the developmental process in the embryo?

A
  • induction
  • proliferation
  • differentiation
  • morphogenesis
  • maturation
36
Q

describe induction

A

when one group of cells tells another group of cells (competent cells) to do something

37
Q

describe proliferation

A

cell division, increase in number and accumulation of cell productions

38
Q

describe differentiation

A

development of specific structures and/or functions by individual cells or group of cells

39
Q

describe morphogenesis

A

cell migration, interactions and proliferations causing the development of specific structures

40
Q

describe maturation

A

attainment of adult size and function from proliferation, differentiation, and morphogenesis

41
Q

what is gastrulation?

A
  • the formation of the 3 germ layers
    • ectoderm, mesoderm, and endoderm
  • takes place around week 3
42
Q

what is the bilaminar germ disc?

A
  • after the blastocyst implants, the embryoblast differentiates into two layers
    • dorsal cells (epiblast layer)
    • ventral cells (hypoblast layer)
  • establishment of embryo axis (which direction will be which)
43
Q

describe the layers of the bilaminar germ disc

A
  • dorsal cells (epiblast layer)
    • reorganize to form amniotic cavity
    • superior, high columnar cells
  • ventral cells (hypoblast layer)
    • form the roof of the secondary yolk sac
    • inferior, small cuboidal cells
44
Q

what is the primitive streak?

A
  • after the formation of the bilaminar disc, the primitive streak forms
    • little groove formed by epiblast cells, which proliferate to bulge out to either side of the groove
    • defines the future bilateral symmetry along a rostral-caudal axis
      • prochordal plate forms at the rostral end, where the ectoderm curves around integrates with the endoderm
45
Q

describe the process of gastrulation

A
  • ectodermal cells invaginate at the primitive node, forming the primitive pit
  • cells migrate between ectoderm and endoderm
  • the notochord forms (vertebral precursor)
  • epiblast cells (future ectoderm) divide, migrate, and invaginate, spreading laterally between the two layers to form the mesoderm
  • mesoblast cells form true embryonic endoderm and mesoderm
46
Q

the notochord and mesoderm totally separate the ectoderm and endoderm everywhere except ___ and ___

A

prochordal plate and the cecal plate (the other end)

47
Q

describe formation of the mesoderm

A
  • medial epiblast cells lose their cell-cell adhesions, become motile, and invade inwards
  • these mesenchymal cells are interspersed in matrix and have no polarity
  • chane in cell attachment proteins from E to N cadherin
48
Q

the formation of the mesoderm is important in tooth development. why?

A

epithelial cells and mesenchymal cells have to talk to one another to make enamel (epithelial) and dentin/pulp (mesenchymal)

49
Q

describe the triploblastic embryo

A
  • after the mesoderm is formed, we have a disc with 3 layers and a cephalic end defined by the prochordal plate, and folding can occur
  • the head fold is going to form the oropharyngeal (buccopharyngeal) membrane at the prochordal plate end
    • no mesoderm between ectoderm and endoderm
  • location of the stomodeum (primitive mouth) will be here
50
Q

what do ectodermal cells give rise to?

A
  • nervous system
  • epidermis and its appendages (hair, nails, sebaceous glands, sweat glands)
  • epithelium lining the oral cavity, nasal cavities, and sinuses
  • part of the intraoral glands
  • tooth enamel
51
Q

what do endodermal cells give rise to?

A

epithelial lining of the respiratory and gastrointestinal tract and all associated organs

52
Q

what do mesodermal (mesenchymal) cells give rise to?

A
  • muscles and all the structures derived from the connective tissue
    • bone, cartilage, blood, dentin*, pulp*, cementum*, and the periodontal ligaments*
    • *neural crest
53
Q

after week 3, and gastrulation occurs, which 3 key events take place?

A
  1. differentiation of the nervous system
  2. formation/migration of the neural crest
  3. embryo folding: head fold, lateral folds, and tail fold
54
Q

describe embryonic folding

A
  • onset of folding is at 24 days
  • imagine a flat plate forming a tube (primitive nervous system) and moving that tube down inside a continually forming body of cells
55
Q

what is the neuroectoderm?

A

a specialized group of cells that differentiates from the ectoderm

56
Q

describe nervous system formation

A
  • formation of neuroectoderm
  • localized to the neural plate of the embryo from the cephalic end to the caudal end
    • neural plate - central band of cells that extends the length of the embryo
  • plate undergoes further growth and thickening, causing it to deepend and invaginate inward, forming the neural groove
57
Q

where does the neural tube closure occur?

A

neural fold fusion begins at the upper cervical levels and proceeds both rostrally and caudally

58
Q

neural tube closure is a critical point in development. what can result if neural tube closure is incomplete?

A

spina bifida

59
Q

what is the fate of paraxial mesoderm?

A

cartilage, segmented muscle

60
Q

what is the fate of intermediate mesoderm?

A

kidneys, gonads

61
Q

what is the fate of the lateral plate mesoderm?

A

heart, gut

62
Q

differentiated mesoderm gives rise to the ___ that are located on the sides of the developing central nervous system

A

somites

63
Q

describe formation of the “head”

A
  • neural tube expands to form the forebrain, midbrain, and hindbrain
  • hindbrain segments into rhombomeres which express Hox genes
  • branchial arches develop
64
Q

the neural crest develops from what, and during which week?

A

develops from the neuroectoderm during the 3rd week

65
Q

describe neural crest migration

A
  • after it is formed, it migrates away from the crests of the neural folds and disperses in mesenchyme
    • so, some cells in the mesenchyme are derived from the neuroectoderm
  • migrates widely and contributes to many structures
66
Q

sometimes, mesenchyme will be described as ___ because of its origins

A

ectomesenchyme

67
Q

where does dental pulp and dentin come from?

A

neural crest tissue

68
Q

what is treacher collins syndrome?

A
  • aka mandibulofacial dysostosis
  • failure of neural crest cells to migrate to the facial region
69
Q

in embryo folding, the head fold is critical to the formation of what?

A

the oral cavity

70
Q

embryo folding ultimately determines the final disposition of what?

A

ectoderm, mesoderm, and endoderm

71
Q

describe the development of the pharynx

A
  • stomodeum (primitive mouth) remains separate, but will ultimately break down to form the oral opening of the GI tract
  • the foregut gives rise to the primitive pharynx
  • the structure will ultimately form the oropharynx
72
Q

when does the fetal period occur?

A

week 9 (3rd month) to birth

73
Q

what occurs during the fetal period?

A
  • the basic tissues and structures are mainly formed
    • a matter of growth and continued specialization
  • maturation of existing structures occurs as the embryo enlarges, becoming a fetus
  • physiological process of maturation of the individual tissue types and organs
  • proliferation, differentiation, and morphogenesis

Oral Biology (19 decks)

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