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Flashcards in General Embryology Deck (52):
1

what are the three periods of general embryology?

preimplantation
embryonic
fetal

2

fertilization causes the formation of what?

zygote

3

mitosis of the zygote leads to formation of what?

blastocyst

4

growth factors, and cell adhesion molecules act through what?

signaling complexes which activate various transcription factors, affecting cellular changes

5

what are some changes that may occur due to growth factor or cell adhesion molecules

proliferation, differentiation or apoptosis

6

what are the ways growth factors can act?

autocrine, paracrine, or endocrine
*mostly through paracrine

7

why is Bone Morphogenic Protein (BMP) important in craniofacial development?

induction, formation, determination and migration of neural crest cells
-patterning and formation of facial primordia
-negative regulator of myogenesis
-regulator of early tooth morphogenesis and differentiation
**at gastrulation, it switches between epidermal vs. neural fate

8

Homeobox genes code for what?

transcription factors that begin to make cells pattern into one tissue/organ type or another
*involved in segmentation

9

HOX genes

function in pattering the body axis(rostral caudal) and determine where limbs and other body segments will grow in developing fetus

10

Msx genes

control cellular process of differentiation and proliferation during development

11

Dlx genes

control development of ectodermal tissues derived from lateral border of neural plate
-distal proximal of pharyngeal arches

12

Shh (sonic hedgehog) genes

play important role in early induction of facial primordium

13

cell adhesion molecules are responsible for what?

specific cell aggregation and sorting
calcium dependent=cadherins
calcium independent=CAM

14

after initial cleavage of the zygote the solid ball of cells is known as what?

morula and then later becomes a blastocyst

15

by the end of the first week the blastocyst stops traveling and does what?

implants into the thickened uterine wall in a processes called implantation

16

what are the components of a blastocyst

outer most cells are trophoblast, inner ball of cells is the embryoblast, and then the yolk sack fills the rest of the space

17

the embryonic period begins and ends when?

starts at the end of the second week
ends at the end of week eight

18

what occurs during the embryonic period

spacial and temporal events called pattering

19

what are some of the pattering structures that will form during the embryonic period?

pharyngeal arches, somtie development, face development, palate and tongue

20

embryonic phase: patterning

-axial specification
-segmentation
-tissue and organ specialization and formation
-dentition development regionally

21

what is induction

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

22

Proliferation

cell division, increase in number and accumulation of cells products

23

differentiation

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

24

morphogenesis

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

25

maturation

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

26

what is gastrulation

the formation of the 3 germ layers
ectoderm
mesoderm
endoderm
*happens around week three

27

after the blastocyst implants, the embryoblast differentiates into two layers:

epiblast-form amniotic cavity
hypoblast-form roof of secondary yolk sac

28

what type of cells are the epiblast layer

columnar

29

what type of cells are the hypoblast layer

cuboidal

30

when does the primitive streak form?

after the bilaminar disk forms

31

what is the primitive streak

-a little groove formed by the epiblast cells
-defines the future bilateral symmetry along a rostral-caudal axis

32

what is the prochordal plate

forms at the rostral end and is where the ectoderm curves around and integrates with the endoderm

33

the ectodermal cells at the primitive streak invaginate at the primitive node forming what?

the primitive pit

34

what happens at the primitive pit?

ectodermal cells migrate between the ectoderm and endoderm to form the notochord and then move laterally to form the mesoderm

35

the notochord and mesoderm totally separate the ectoderm from the mesoderm everywhere but at two places, what are they?

the prochordal plate and the cecal plate

36

how do the ectodermal cells become mesoderm?

medial epiblast cells lose their cell-cell adhesion and become motile and invade inwards
-these mesenchymal cells are interspersed in matrix and have no polarity
- cell attachment proteins from E to N cadherin

37

head folding at the prochordal plate forms what?

oropharyngeal (buccopharyngeal) membrane
**remember no mesoderm between the two layers
this is the location of the stomodeum (primitive mouth)

38

what do the ectodermal cells give rise to?

-nervous system
-epidermis including (hair, nails, sebaceous and sweat glands)
-epithelium lining of oral, nasal, and sinus cavities
-part of intra oral glands
-enamel

39

what does the endoderm give rise to?

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

40

what does the mesoderm give rise to?

muscles, all CT derived tissues ( bone, cartilage, blood, dentin, pulp, cementum and PDL)

41

what are the three key things that happen after gastrulation(after week 3)?

1. differentiation of nervous system
2. Formation/migration of neural crest
3. Head, lateral , and tail folds

42

what is the neuroectoderm

specialized group of cells that differentiates from the ectoderm, localized to the neural plate that extends from the cephalic to the caudal end
*undergoes further growth in thickening, which causes and inward invagination forming the neural groove

43

once the neural groove forms what happens

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

44

paraxial mesoderm gives rise to?

cartilage, segmented muslce

45

intermediate mesoderm gives rise to?

kidneys, gonads

46

lateral plate mesoderm gives rise to?

heart and gut

47

differentiated mesoderm gives rise to?

somites, which are located on the sides of the developing CNS

48

once the neural tube forms it expands and forms what?

forebrain, midbrain, hindbrain
*hindbrain segments into rhombomeres which express Hox genes
*branchial arches develop

49

Neural crest formation and migration

develops from the neuroectoderm during week 3 and breaks away from the crests of the neural folds and disperses in mesenchyme

50

Treacher Collins syndrome

failure of neural crest cells to migrate to the facial region

51

how does the pharynx form

stomodeum remains separate, but will ultimately break down to form the oral opening of the GI
-foregut gives rise to primitive pharynx
-ultimately becomes oropharynx

52

fetal period

9th week to to birth
basic tissues and structures are mainly formed, growth and continued specialization
*as the embryo enlarges it becomes the fetus
**proliferation, differentiation and morphogenesis
-physiological process of maturation of the individual tissue types and organs