General Embryology

Question 1

what are the three periods of general embryology?

Answer 1

preimplantation
embryonic
fetal

Question 2

fertilization causes the formation of what?

Answer 2

zygote

Question 3

mitosis of the zygote leads to formation of what?

Answer 3

blastocyst

Question 4

growth factors, and cell adhesion molecules act through what?

Answer 4

signaling complexes which activate various transcription factors, affecting cellular changes

Question 5

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

Answer 5

proliferation, differentiation or apoptosis

Question 6

what are the ways growth factors can act?

Answer 6

autocrine, paracrine, or endocrine

*mostly through paracrine

Question 7

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

Answer 7

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

Question 8

Homeobox genes code for what?

Answer 8

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

Question 9

HOX genes

Answer 9

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

Question 10

Msx genes

Answer 10

control cellular process of differentiation and proliferation during development

Question 11

Dlx genes

Answer 11

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

Question 12

Shh (sonic hedgehog) genes

Answer 12

play important role in early induction of facial primordium

Question 13

cell adhesion molecules are responsible for what?

Answer 13

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

Question 14

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

Answer 14

morula and then later becomes a blastocyst

Question 15

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

Answer 15

implants into the thickened uterine wall in a processes called implantation

Question 16

what are the components of a blastocyst

Answer 16

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

Question 17

the embryonic period begins and ends when?

Answer 17

starts at the end of the second week

ends at the end of week eight

Question 18

what occurs during the embryonic period

Answer 18

spacial and temporal events called pattering

Question 19

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

Answer 19

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

Question 20

embryonic phase: patterning

Answer 20

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

Question 21

what is induction

Answer 21

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

Question 22

Proliferation

Answer 22

cell division, increase in number and accumulation of cells products

Question 23

differentiation

Answer 23

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

Question 24

morphogenesis

Answer 24

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

Question 25

maturation

Answer 25

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

Question 26

what is gastrulation

Answer 26

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

Question 27

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

Answer 27

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

Question 28

what type of cells are the epiblast layer

Answer 28

columnar

Question 29

what type of cells are the hypoblast layer

Answer 29

cuboidal

Question 30

when does the primitive streak form?

Answer 30

after the bilaminar disk forms

Question 31

what is the primitive streak

Answer 31

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

Question 32

what is the prochordal plate

Answer 32

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

Question 33

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

Answer 33

the primitive pit

Question 34

what happens at the primitive pit?

Answer 34

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

Question 35

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

Answer 35

the prochordal plate and the cecal plate

Question 36

how do the ectodermal cells become mesoderm?

Answer 36

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

Question 37

head folding at the prochordal plate forms what?

Answer 37

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

Question 38

what do the ectodermal cells give rise to?

Answer 38

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

Question 39

what does the endoderm give rise to?

Answer 39

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

Question 40

what does the mesoderm give rise to?

Answer 40

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

Question 41

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

Answer 41

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

Question 42

what is the neuroectoderm

Answer 42

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

Question 43

once the neural groove forms what happens

Answer 43

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

Question 44

paraxial mesoderm gives rise to?

Answer 44

cartilage, segmented muslce

Question 45

intermediate mesoderm gives rise to?

Answer 45

kidneys, gonads

Question 46

lateral plate mesoderm gives rise to?

Answer 46

heart and gut

Question 47

differentiated mesoderm gives rise to?

Answer 47

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

Question 48

once the neural tube forms it expands and forms what?

Answer 48

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

Question 49

Neural crest formation and migration

Answer 49

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

Question 50

Treacher Collins syndrome

Answer 50

failure of neural crest cells to migrate to the facial region

Question 51

how does the pharynx form

Answer 51

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

Question 52

fetal period

Answer 52

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