Embryology: Week Three Development

Front 1

What process(es) tend(s) to dominate weeks 3-8 of embryogenesis? (Hint: this is the stage when the embryo is most susceptible to teratogens)

Back 1

Organogeesis

Front 2

Week three post-fertilization is how many weeks following LNMP?

Back 2

5 weeks post LNMP

Front 3

Name the process whereby the bilaminar embryonic disc is converted into a trilaminar disc.

Back 3

Gastrulation

Front 4

What structure results from the proliferation and migration of epiblastic cells along the medial plane of the dorsal aspect of the embryo? (Hint: This structure identifies the embryo’s craniocaudal axis, dorsal and ventral surfaces, and right and left sides).

Back 4

primitive streak

Front 5

True or false: The structure described in the previous question grows in a cranial to caudal direction.

Back 5

FALSE

Front 6

What is the anatomic starting point for growth of the notochord?

Back 6

primitive node at the anterior end of the primitive streak

Front 7

Cells from a structure derived from the epiblast migrate into the primitive groove to form a mesenchymal layer between the epiblast and hypoblast layers. Name this layer.

Back 7

intraembryonic mesoderm: develops into the lateral intermediate and proximal mesoderm

Front 8

Name another layer deposited superficially to the hypoblast layer and deep to the mesenchymal layer.

Back 8

the endoderm is deposited displacing the hypoblast layer

Front 9

Identify the layer that remains adjacent to the amnion.

Back 9

ectoderm

Front 10

What sorts of connective tissue develop from the mesenchymal layer?

Back 10

connective tisues, muscles, bone

Front 11

Sacrococcygeal teratoma

Back 11

results from persistence of primitive streak that normally degenerates

Front 12

True or False: The notochordal process grows in a caudal to cranial direction.

Back 12

true the notochordal process grows from the caudal to cranial direction stemming from the primitive node

Front 13

Name the membrane that forms at the prechordal plate that separates the foregut from the stomodeum.

Back 13

oropharyngeal membrane

Front 14

Cells from what structure migrate cranially on each side of the notochordal process to form cardiogenic mesoderm in the cardiogenic area at the end of week 3?

Back 14

cells from the primitive streak migrate cranially to create the cardiogenic area of mesoderm

Front 15

Name the two sites of the trilaminar embryo that remain bilaminar. (Hint: one becomes the mouth, the other one becomes the anus).

Back 15

oropharyngeal membrane and ccloacal membrane

Front 16

osseous

Back 16

bone

Front 17

The notochord is the future site of what osseous structure?

Back 17

vertebral column

Front 18

Fill in the blanks in the steps of notochord development:

Front 19

Primitive pit extends into elongating notochordal process, forming _________________.

Back 19

notochordal process

Front 20

Floor of notochordal process fuses with underlying _________________.

Back 20

endoderm

Front 21

Fused regions undergo ______________________ resulting in formation of openings in floor of notochordal process, bringing notochordal canal in communication with ________________.

Back 21

appotosis/ yolk sac

Front 22

Openings become confluent and notochordal canal disappears; remains of notochordal process form grooved plate called _____________________.

Back 22

notochrodal plate

Front 23

Small passage, ________________ temporarily connects amniotic cavity and yolk sac; this obliterates when development of notochord is complete.

Back 23

notochrodic cannal

Front 24

At cranial end, notochordal cells proliferate and notochordal plate infolds to form _______________________.

Back 24

notochord

Front 25

Notochord becomes detached from _______________, which again becomes continuous layer, roof of ____________________.

Back 25

endoderm is the roof of the secondary yolk sac at this point

Front 26

What critical structure is induced to develop by the notochord?

Back 26

nueral plate

Front 27

What anatomic structure in the adult is derived in part from the notochord?

Back 27

inner portion of the intervertebral disc--nuvlrud pulposus

Front 28

Name the process whereby the neural plate, crests, folds and tube are formed.

Back 28

neuralation

Front 29

True or False: the endoderm of the neural plate gives rise to the CNS.

Back 29

the neural plate in on the ectoderm--FALSE

Front 30

Name the structure formed by invagination of the neural plate. (Hint: this structure is the first sign of brain development).

Back 30

CNS, retina pineal body posterior part of pituitary gland

Front 31

Name the structure that results from migration and fusion of neural folds above the notochord. (Hint: this structure separates from the overlying neurectoderm, and forms neuropores at its rostral and caudal ends during the end of the fourth week).

Back 31

Neural tube

Front 32

Name a clinical condition that results from failure of neuropores to close.

Back 32

spina bifita

Front 33

As neural folds fuse, some neuroectodermal cells lose their attachments to neighboring cells and form a structure that soon separates into right and left parts that migrate to sides of the neural tube. What is this structure called? What tissue arises from this structure?

Back 33

neural crest cells --> adrenal medula, bones and muscules of the face, melanocytes

Front 34

Starting in the medial plane and moving laterally, name the three layers of intraembryonic mesoderm that form on either side of the neural tube.

Back 34

bulbar and conal ridges in heart sensory ganglia and nerves

Front 35

True or False: The intraembryonic mesoderm is continuous with the extraembryonic mesoderm covering the yolk sac and amnion.

Back 35

TRUE

Front 36

Which mesoderm layer differentiates into somites?

Back 36

paraxial

Front 37

What do somites become?

Back 37

axial skeletal system, skeletal muscle, dermis begins at end of week 3 and complete at end of week 5 begins to develop cranially

Front 38

Which mesoderm layer develops coelomic spaces that coalesce to form intraembryonic coelom.

Back 38

lateral mesoderm

Front 39

True or false: intraembryonic coelom does not split the lateral mesoderm.

Back 39

False, the intraembryonic coelom is formed by bubbles in the cranial poriton of the lateral mesoderfusing and becoming continuous with the extra embryonic ceolom

Front 40

Name the two layers of mesoderm that develop from the lateral mesoderm.

Back 40

the embryonic splanchinic/ viseral mesoderm and the embryonic somatic/ perietal mesoderm <--- theses layers are continuous with their respective extra-embryonic mesoderm layers

Front 41

Which layer of mesoderm is continuous with the aspect of extraembryonic mesoderm covering the amnion? (Hint: Forms the embryonic body wall)

Back 41

the somatic/ parietal mesoderm

Front 42

Which layer of mesoderm is continuous with the aspect of extraembryonic mesoderm covering the yolk sac? (Hint: Forms the embryonic gut wall)

Back 42

embryonic splanchinic or viseral mesoderm

Front 43

Name the space between the somatopleure and splanchnopleure.

Back 43

somatopleure= somatic covering of the coleom Splanchnopleure= splanchnic covering of the organs of the coleom Coleom forms three cavities the pericardial cavity, pluera cavity and the peritoneal cavity

Front 44

What 3 body cavities develop from the intraembryonic coelom during the second month?

Back 44

pleural cavity peritoneal cavity and the pericardial cavity

Front 45

What structure appears early as diverticulum from the caudal wall of the yolk sac and extends into the connecting stalk? (Hint: it is involved in early blood formation and development of urinary bladder)

Back 45

allantois- involved with early blood supply and development of the bladder, gives rise to the urachus--> median umblical ligament

Front 46

The blood vessels of the alantois become the blood vessels of what critical prenatal organ?

Back 46

umbilical cord

Front 47

What is the urachus?

Back 47

urachus is a part of the early bladder which forms when the alantoisis contrsticts--> shrivels after birth becoming ht emedian umbilical ligament

Front 48

The urachus persists after birth to become a ligament. Name the ligament.

Back 48

median umbilical ligament

Front 49

Angiogenesis begins at the start of the third week. Where does it begin?

Back 49

Early blood development occurs in the yolk sac and the alantois intraembryonic hemematopoisis begins in the liver at 6 wk

Front 50

Do initial hematogenesis and angiogenesis begin intraembryonically, or extraembryonically?

Back 50

extraembryonically

Front 51

What must happen to endothelial heart tubes in order for a primitive heart tube to be formed?

Back 51

the endothelial heart tubes migrate ventrally and medially and fuse to form on heart tube

Front 52

True or False: The heart is the first functioning organ in the embryo.

Back 52

True-- the heart begins to beat at three weeks embryonic or five weeks gestationally

Front 53

True or False: The heart starts at the cranial end of the embryo.

Back 53

true-- before head tail folding the heart is located in the cardiogenic region which is cranial to the orophryangeal membrane

Front 54

True or False: The heart starts to beat at the beginning of gestational week five.

Back 54

fasle the heart begins to beat at week six

Front 55

True or False: Primary villi grow into the core of secondary chorionic villi and cover the entire surface of the chorionic sac.

Back 55

False-- secondary vili grow into the core of primary vili covering the surface of the chorioinic sac. Primary vili formed during week two as projections of the cytotrophoblast intot he syncocytotrophoblast

Front 56

True or False: Some mesenchymal cells from villi differentiate into blood capillaries that fuse to form aterio-capillary-venous networks called stem villi.

Back 56

True they are also called 3* villi

Front 57

True or False: Another term for stem villi is “tertiary chorionic villi”.

Back 57

TRUE-- Stem villi are mesenchymal cells which have formed a netweork which fuses to become the atrio-capilary-vnous networks

Front 58

True or False: Stem villi become connected to heart tubes via vessels that develop outside of the chorion.

Back 58

TRUE

Front 59

True or False: By the end of gestational week five, embryonic blood begins to flow through this network.

Back 59

False, when the heart begins to beat during week 3, the embyronic blood begins to flow through the network

Front 60

True or False: Oxygen and nutrients in maternal blood in the intervillious space diffuse through walls of villi and enter the embryo’s blood.

Back 60

TRUE

Front 61

True or False: Waste is removed in the same direction as oxygen and nutrient diffusion from mother to embryo.

Back 61

False-- oxygen and nutrients enter the embryo throught he intravilliious space while waste leaves the embryo

Front 62

True or False: Cytotrophoblasts from the chorionic villi extend through the syncytiotrophoblast to form a cytotrophoblastic shell which attaches the chorionic sac to the perimetrium.

Back 62

Almost true the cytrotrophoblast from the chornionic vili extends through the synctrophoblast where it forms the cytotrophoblastic shell which attaches to the endometrium