Embryology Week 2

Front 1

organogenesis

Back 1

formation of the organ systems

Front 2

embryo proper

Back 2

the three germ layers (ectoderm, mesoderm, and endoderm) that develop from the inner cell mass

Front 3

placenta & chorion

Back 3

develop from the trophoblasts & extra-embryonic membrane

Front 4

ectoderm

Back 4

develops into skin & CNS

Front 5

endoderm

Back 5

develops into lung & guts

Front 6

mesoderm

Back 6

develops into muscle, skeletal, renal, and reproductive systems

Front 7

gastrulation

Back 7

formation of the three germ layers

Front 8

primitive streak

Back 8

-a pit, node, and groove that form in the epiblast
-differentiate into the 3 germ layers

Front 9

definitive endoderm cells

Back 9

cells migrate into primitive groove & through epiblast to replace hypoblast with definitive endoderm cells

Front 10

formation of mesoderm

Back 10

-second wave of cells migrate through primitive groove & epiblast to form mesoderm

Front 11

ectoderm formation

Back 11

epiblast cells that are left behind after definitive ectoderm cells & mesoderm form --> ectoderm

Front 12

mesoderm position

Back 12

-mesoderm is positioned in all regions between epiblasts & endoblasts (except at the two poles where the mouth ad anus will form)

Front 13

mesoderm forms specialized regions from medial to lateral...

Back 13

-forms the Notochord medially --> will induce the formation of the CNS (brain & spinal chord)

Front 14

buccopharyngeal membrane

Back 14

-depression in epiblast that will form the mouth
-no mesoderm under this depression (just ectoderm & endoderm)

Front 15

coacal membrane

Back 15

-depression in epiblast that will form anus
-no mesoderm under this depression (just ectoderm & endoderm)

Front 16

neural plate

Back 16

-induced by notochord
-expands over the dorsal surface of the embryo

Front 17

mesoderm specializes into 3 subtypes

Back 17

-somites
-intermediate mesoderm (IM)
-lateral plate mesoderm (LPM)

Front 18

somites

Back 18

-form vertebrate & muscle

Front 19

intermediate mesoderm

Back 19

-forms kidneys & reproductive system

Front 20

lateral plate mesoderm

Back 20

-forms membrane lining of thorax & abdomin

Front 21

somatopleuric membrane

Back 21

-associated with the lateral plate mesoderm
-forms future body walla

Front 22

splanchnopleuric membrane

Back 22

-associated with the lateral plate membrane
-forms the circulatory system & future gut wall

Front 23

sclerotomes

Back 23

-cells from somites migrate towards neural tube to form vertebrate around central neural tube
-forms from somites leaving dermomyotomes for the formation of muscle & skin mesodermal structures

Front 24

dermomyotomes

Back 24

-what is left behind from somite cells
-will form connective tissue & muscle in trunk
-form back and peripheral body muscle (not limbs) and most of the dermis

Front 25

epimere

Back 25

-derivative of mytomes
-will form muscles in the back

Front 26

hypomere

Back 26

-derivative of myotomes
-will form muscles in the trunk

Front 27

molecular signals

Back 27

-molecular signals are known
-errors in signals will lead to birth defects

Front 28

cell & tissue differentiation

Back 28

-depends on local & distant signals, secreted growth factors, cell-cell contacts, and cell-extracellular matrix interactions
-there are signals the differentiate tissue into the right & left sides of the body =

Front 29

human signal pathways

Back 29

-pathways are seen across species lines
-may not be same molecule/hormone, but some signal plays a similar role in the pathway

Front 30

molecules secreted during development...

Back 30

-move through currents to get to specific locations
-even divide into tissues on right & left sides of body

Front 31

gatrulation

Back 31

invagination & ingress of cells to form a trilaminar emrbyo

Front 32

prechordal plate

Back 32

lies just between the primitive pit & buccopharyngeal membrane

Front 33

nucleus polposus

Back 33

-the notochord is thought to remain as the central portion of the vertebral discs called the nucleus polposus

Front 34

neurulation

Back 34

-transformation of the flat neural plate into a neural tube

Front 35

neuroectoderm

Back 35

the underlying prechordal plate mesoderm and cranial
portion of the notochord induces the dorsally positioned ectoderm to be transformed to a neuroectoderm

Front 36

closure of the neural tube

Back 36

-begins in the center and continues bi-directionally towards the cranial & caudal poles until the entire tube is closed

Front 37

anencephaly

Back 37

-neural tube does not close on the cranial end

Front 38

spina bifida

Back 38

-neural tube does not close on the caudal end

Front 39

neural crest cells

Back 39

-develop in the right and left lateral lips of the folding and fusing neuroplate
-appear as a mophological distinct that migrates out from the neuroectoderm

Front 40

migrating neuronal cells

Back 40

-migrating neural crest cells that move out from the neuralplate form a variety of structures

Front 41

cranial-caudal folding

Back 41

-head to tail folding
-results in the classic fetal position
-also repositions the thoracic & pelvic structures to a more ventral position

Front 42

lateral folding

Back 42

-ventral midline fusion of the lateral edges of the embryo causing the embryo to fold into a tube
-embryo becomes a tubular structure with yolk sac getting pinched off to form gut tube
-gut tube becomes surrounded by a cavity that has mesodermal lining made up of somatopleure & splanchnopleure

Front 43

somatopleure & splanchnopleure

Back 43

-continuously line adbominal cavity in adults to form the peritoneal lining
-also form the pleural lining of lungs

Front 44

lateral folding in the throacic region of the embryo

Back 44

-leads to the fusion of the two arterial tubes
-marks the initial phase of heart development

Front 45

diaphragm formation

Back 45

-thorax has to be divided into heart (pericardial) cavity & two pleural (lung) cavities
-open canal between future thorax & future abdomen needs to be closed off by diaphragm formation

Front 46

developmental defects

Back 46

-every system that develops is susceptible to developmental defects
-this affects where structures are positioned in the adult and has consequences on medical examinations, surgery, and overall health

Front 47

failure of the diaphragm to form properly

Back 47

-if diaphragm doesn’t form properly, there may be openings in it
-this can allow for abnormalities such as the intestines growing into the thoracic cavity