Weeks 3-8 Development

Question 1

when primary germ layers give rise to tissues and organs; at the end of this period, main organ systems established

Answer 1

organogenesis

Question 2

organogenesis is an ___ period that occurs from ____

Answer 2

embryonic; week 3-8

Question 3

neurulation is the process by which the ____ forms the ____

Answer 3

neural plate; neural tube

Question 4

neurulation occurs in the ____ via _____

Answer 4

ectoderm; notochordal induction

Question 5

neurulation completed by the end of ____

Answer 5

4th week

Question 6

four main events of neurulation

Answer 6

1. formation of neural plate
2. shaping of neural plate
3. invagination of neural plate
4. closure of neural groove

Question 7

during neurulation, notochord induces thickening in overlying ____ along midline of ____ forming _____ (these cells make up neuroectoderm)

Answer 7

ectoderm; embryo; neural plate

Question 8

laterally elevated edges

Answer 8

neural folds

Question 9

depressed midregion of neural plate

Answer 9

neural groove

Question 10

neural folds begin to move together and eventually fuse. this fusion begins in ____ and progresses both ___ and ____; this results in the formation of the _____

Answer 10

cervical region (5th somite); cranially; caudally; neural tube

Question 11

____ fuse at midline (progressing cranially and caudally), forming the ____, which separates from the _____

Answer 11

neural folds; neural tube; ectoderm

Question 12

neural groove will become the _____

Answer 12

neural canal

Question 13

until fusion is completed the cranial and caudal ____ allow the ____ to communicate with the _____

Answer 13

neuropores; neural tube; amniotic cavity

Question 14

closure of these neuropores indicates _____

Answer 14

the end of neurulation

Question 15

As neural folds fuse, cells at lateral border (crest) of neuroectoderm dissociate, called _____

Answer 15

neural crest cells

Question 16

neural crest cells undergo _____ transition and enter the underlying _____

Answer 16

epithelial to mesenchymal; mesoderm

Question 17

mesoderm near midline proliferate to form thickened _____

Answer 17

paraxial mesoderm

Question 18

more laterally, the mesoderm stays thin, known as _____

Answer 18

lateral plate mesoderm

Question 19

in between paraxial and lateral plate mesoderm is the ______

Answer 19

intermediate mesoderm

Question 20

intracellular cavities split lateral plate mesoderm into:

Answer 20

• somatic or parietal layer (lines the amnion)

- splanchnic or visceral layer (lines yolk sac)

Question 21

the cavity between the somatic/parietal layer and splanchnic/visceral layer is the _____; it is continuous with the _____ on each side of the embryo

Answer 21

intraembryonic cavity; extraembryonic cavity

Question 22

____ is the organization of the paraxial mesoderm which occurs at the beginning of week 3

Answer 22

somite

Question 23

at the beginning of week 3, the paraxial mesoderm starts to organize into segments which form ____ to ____ beginning in ____ region; organized pairs called ____

Answer 23

cranially; caudally; occipital; somites

Question 24

the paraxial mesoderm will give rise to most of the _____, _____and ____

Answer 24

axial skeleton; skeletal muscles; dermis of the back

Question 25

somites (in pairs)

Answer 25

- 4 occipital (will disappear) - 8 cervical - 12 thoracic - 5 sacral - 5 lumbar - 8-10 coccygeal (last 5-7 disappear)

Question 26

the ____ of the embryo can be determined by counting somites

Answer 26

age

Question 27

during somite differentiation, ____ cells undergo ____ and arrange in donut shape around _____

Answer 27

mesoderm; epithelization; small lumen

Question 28

during somite differentiation, cells in ventral and medial walls shift position to surround _____, forming the _____

Answer 28

neural tube; sclerotome

Question 29

during somite differentiation, cells between dorsomedial cells and ventrolateral cells form the _____

Answer 29

dermatome

Question 30

during somite differentiation, cells at dorsomedial and ventrolateral edges of upper region of somite form precursors for _____

Answer 30

muscle cells

Question 31

cells will become ____ and migrate beneath _____ and form the _____

Answer 31

mesenchymal; dermatome; myotome

Question 32

somite derivatives

Answer 32

- sclerotome: vertebrae and ribs - dermatome: dermis - myotome: muscles

Question 33

the outer lining of cells will become the ____

Answer 33

epidermis

Question 34

intermediate mesoderm derivatives:

Answer 34

differentiates into urogenital structures of urinary system and reproductive system

Question 35

lateral plate mesoderm derivatives: the _____ along with overlying ectoderm form lateral body wall folds that will help close _____

Answer 35

parietal mesoderm layer; ventral body wall

Question 36

mesoderm cells of _____ surrounding the intraembryonic cavity form ______, i.e. _____ that line ______ and secrete ____

Answer 36

parietal layer; mesothelial membranes; serous membranes; peritoneal, pleural, and pericardial cavities; serous fluid

Question 37

_____ together with overlying endoderm form walls of the _____

Answer 37

visceral mesoderm layer; gut tube

Question 38

mesoderm cells of visceral layer form thin _____ around each organ

Answer 38

serous membrane

Question 39

blood vessels arise from blood islands

Answer 39

vasculogenesis

Question 40

blood vessels sprouting from existing vessels

Answer 40

angiogenesis

Question 41

blood cells and blood vessels rise from ____, vasculogenesis is what is occurring in embryo

Answer 41

mesoderm

Question 42

blood islands begin to form in mesoderm surrounding wall of ____ during ____, then later in the _____ and other regions

Answer 42

yolk sac; week 3; lateral plate mesoderm

Question 43

endoderm derivatives will form the _____; lines the ____ of the embryo and forms the _____

Answer 43

gastrointestinal tract; ventral surface; roof of yolk sac

Question 44

body folding simultaneously occurs in both the ____ as well as the _____ and takes the embryo from a ____ to a _____

Answer 44

sagittal plane (i.e. cranial/caudal folds); horizontal plane (i.e. lateral folds); flat disc; cylinder

Question 45

in cranial folding, the _____ acts as a hinge and swings vertically

Answer 45

oropharyngeal membrane

Question 46

in cranial folding, part of yolk sac endoderm is incorporated into embryo as the ____ (proximal portion of GI tract)

Answer 46

foregut

Question 47

in cranial folding, the oropharyngeal membrane separates the ____ from the _____ (will rupture about day 26)

Answer 47

foregut; oral cavity

Question 48

in caudal folding, the ____ swings ventrally

Answer 48

cloacal membrane

Question 49

in caudal folding, portion of yolk sac endoderm is incorporated as the embryonic ____ (distal portion of GI tract)

Answer 49

hindgut

Question 50

in caudal folding, the _____ (future umbilical cord) is now attached to ____ aspect of embryo

Answer 50

connecting stalk; ventral

Question 51

in lateral folding, the ____ part of the yolk sac endoderm is incorporated as embryonic _____

Answer 51

dorsal; midgut

Question 52

at the end of the 4th week, lateral folds fuse, except at region of ______

Answer 52

connecting stalk

Question 53

In lateral folding, the ____ connection to the yolk sac constricts, leaving a narrower connection: ______

Answer 53

midgut; the omphaloenteric duct (vitelline duct)

Question 54

parietal and visceral layer of serous membranes continuous at _____

Answer 54

dorsal mesentery

Question 55

the dorsal mesentery suspends ____ from posterior body wall into _____

Answer 55

gut tube; peritoneal cavity

Question 56

the ventral mesentery is only the ____ to the upper part of the _____; it results from the thinning of _____

Answer 56

caudal foregut; duodenum; septum transversum

Question 57

mesenteries double layers of peritoneum which provides pathway for ___, ____ and ____

Answer 57

blood vessels; nerves; lymphatics

Question 58

the embryonic body cavity is comprised of:

Answer 58

- pericardial cavity - 2 pericardioperitoneal canals - peritoneal cavity

Question 59

what is the septum transversum?

Answer 59

mesoderm between the thoracic cavity and yolk sac

Question 60

the septum transversum does not separate ____ and ____ cavities completely because of two _____ canals

Answer 60

thoracic; abdominal; pericardioperitoneal

Question 61

as lung buds grow, they expand into ______

Answer 61

pericardioperitoneal canals

Question 62

______ grow in medially from the lateral walls of the pericardial cavity, dividing it into the definitive ____ and ____ cavities

Answer 62

pleuropericardial folds; pericardial (1) and pleural cavities (2)

Question 63

_____ develop from the dorsal body wall and fuse with the septum transversum, closing off the pericardioperitoneal canals on either side of the foregut during formation of the ____

Answer 63

pleuroperitoneal folds; diaphragm

Question 64

diaphragm components:

Answer 64

1. septum transversum 2. pleuroperitoneal membranes 3. mesentery of the esophagus 4. body wall mesoderm