3rd week of development (exam 2)

Question 1

What week of development is this?
-rapid development
-appearance of primitive streak
-development of notochord (develops into NS, 1st system developed)
-differentiation of 3 germ layers “germination”

Answer 1

3rd week of development

Question 2

The 3rd week of development coincides with the week after the 1st missed period, which is ____ weeks after the 1st day of the last normal menstrual period

Answer 2

5

Question 3

What is the 1st major event in 3rd week of development?

Answer 3

gastrulation

Question 4

How does gastrulation begin?

Answer 4

the formation of a longitudinal midline (groove) structure, called the primitive streak

Question 5

Where does the primitive streak begin and end?

Answer 5

starts in the epiblast as a small depression and then ends at the caudal end of the embryonic disc (embryo)

Question 6

What is gastrulation?

Answer 6

a formative process where the 3 germ layers (precursors of all embryonic tissues) and the axial orientation are established in embryo

Question 7

Gastrulation is the beginning of _________________ (development of body form) and is the most significant event occurring during the 3rd week. The embryo is referred to as a gastrula

Answer 7

morphogenesis

note: morphology is the study of shapes and structures

Question 8

The first morphological sign of gastrulation is the formation of the….

Answer 8

primitive streak

note: the primitive streak defines for the first time with all major body axes. These consist of the caudal (or head-tail) axis, and the dorsal-ventral (or back-belly) axis and the left-right axis

Question 9

On about day 15 of development, a thickening containing a midline groove forms along the midsagittal plane of the embryonic disc, which has now assumed as an….

Answer 9

oval shape

Question 10

The thickening of cells, called the _________________, elongates to occupy about 1/2 of the length of the embryonic disc, and the groove is called the _____________________ (indentation), becomes deeper and more defined

Answer 10

primitive streak, primitive groove

Question 11

The cranial end of the primitive streak is expanded into a structure called the _______________. It contains a depression called the _________________

Answer 11

primitive node, primitive pit

Question 12

The primitive streak forms at the caudal midline of the ________________. Thus, the cranial-caudal axis can be identified. Formation of the primitive streak also heralds the beginning of gastrulation

Answer 12

embryonic disc

Question 13

The primitive streak, occupies ______% of the length of the embryonic disc

Answer 13

50

Question 14

During gastrulation, epiblast cells move toward the primitive streak, enter the primitive streak, and then migrate away from the primitive streak as individual cells. This is called…..

Answer 14

ingression

Question 15

On day _____, epiblast cells lateral to the primitive streak begin to move into the primitive streak, where they undergo an epithelial-to-mesenchymal transition and loose cell contact

Answer 15

16

Question 16

During gastrulation, epiblast cells move toward the primitive streak, enter the primitive streak, and then migrate away from the primitive streak as individual cells. This is called ingression. On day 16, epiblast cells lateral to the primitive streak begin to move into the primitive streak, where they undergo an epithelial-to-mesenchymal transition and loose cell contact. The collective movement of cells through the primitive streak and into the interior of the embryo form the 3 primary germ layers constitutes…..

Answer 16

gastrulation

Question 17

The 1st ingressing epiblast cells invade the hypoblast and displace its cells so that the hypoblast eventually is completely replaced by a new layer of cells. This is called the…..

Answer 17

definitive endoderm (this happens medially to laterally)

Question 18

Some epiblast cells migrating through the primitive streak diverge into the space between epiblast and nascent definitive endoderm to form a 3rd germ layer - the …..

Answer 18

intraembryonic mesoderm

Question 19

Some epiblast cells migrating through the primitive streak diverge into the space between epiblast and nascent definitive endoderm to form a 3rd germ layer- the intraembryonic mesoderm (inside embryo). These cells migrate bilaterally from the primitive streak initially and form a loose mat of cells between epiblast and endoderm. The mat reorganizes to form 4 main subdivisions of intraembryonic mesoderm. What are these 4 subdivisions called?

Answer 19

1) cardiogenic mesoderm
2) paraxial mesoderm
3) intermediate mesoderm (also called nephrotome)
4) lateral plate mesoderm

Question 20

The 5th population of mesodermal cells migrate cranially from the primitive node at the midline to form a thick-walled midline tube called the….

Answer 20

notochordal process (will become notochord soon)

Question 21

During gastrulation, epiblast will replace hypoblast to become….

Test q

Answer 21

endoderm (and epiblast will also replace itself to become ectoderm)

Question 22

2 faint depressions form in the ectoderm: one at the cranial end of the embryo and the other at the caudal end behind the primitive streak. The ectoderm (top layer) in these areas fuses tightly with the underlying endoderm (bottom layer), excluding the mesoderm and forming bilaminar membranes. The cranial membrane is called the _________________ membrane, and the caudal membrane is the ____________ membrane.

test q!

Answer 22

oropharyngeal, cloacal

Question 23

The oropharyngeal and cloacal membranes later become the blind ends of the….

Answer 23

gut tube

Question 24

T/F: once formation of the definitive endoderm and intraembryonic mesoderm is complete, the epiblast cells no longer move

Answer 24

true!

Question 25

The remaining epiblast after forming the germ layers is now the _____________, which quickly differentiates into the central neural plate and the peripheral surface ectoderm

Answer 25

ectoderm

Question 26

Eventually, the process of gastrulation is complete. At that time- formation of the 3 definitive germ layers of the trilaminar embryonic disc- ectoderm, mesoderm, and endoderm will be complete throughout the length of the disc. ALL 3 germ layers derive from ___________ during gastrulation (referred as gastrula)

Answer 26

epiblast

Question 27

Morphogenetic changes (shape-generating events) occur in each of the germ layers to form the primitive organs rudiments. These are often referred to as...

Answer 27

ectodermal, mesodermal, and endodermal derivatives (will eventually become organs with other tissues- remember multiple tissues make an organ)

Question 28

Formation of the notochord begins with a cranial midline extension form the primitive node, a hollow tube- the...

Answer 28

notochordal process

Question 29

When the notochordal process is completely formed, several transformations take place to convert it from a hollow tube, to a flattened plate, to a....

Answer 29

solid rod

Question 30

The floor of the hollow tube fuses with the underlying endoderm and the 2 layers break down leaving a flattened notochordal _________

Answer 30

plate

Question 31

The floor of the hollow tube fuses with the underlying endoderm and the 2 layers break down leaving a flattened notochordal plate. The notochordal plate them completely detaches from the endoderm, its free ends fuse as it rolls into the containing space between the ectoderm and endoderm, changing into a solid rod called the....

Answer 31

notochord (notochord formation takes about 4-5 days)

Question 32

What is the major inductor of embryological development?

Answer 32

the notochord

Question 33

Later in development, rudiments of the vertebral bodies coalesce around the....

Answer 33

notochord

Question 34

The notochord forms the ______________ at the center of the vertebral discs. This is true in the embryo, fetus, and in young children, but is replaced in adults. The notochord plays many important inductive and patterning roles in early development

Answer 34

nucleus pulposus

Question 35

The developing notochord induces the overlying embryonic ectoderm to thicken and form the....

Answer 35

neural plate

Question 36

The paraxial mesoderm flanks the....

Answer 36

notochord

Question 37

In the future head region, the mesoderm forms bands of cells that remain ________________ as the head mesoderm

Answer 37

unsegmented/uniform

Question 38

The mesoderm becomes more dispersed with development to loosely fill the developing head as the head mesenchyme. The head mesenchyme is derived from both head mesoderm and....

Answer 38

ectodermal neural crest cells

Question 39

The head mesoderm eventually give rise to the....

Answer 39

striated muscles of the face, jaw, and throat

Question 40

The head mesoderm eventually give rise to the striated muscles of the face, jaw, and throat. These muscles differentiate within the segmental _________________________, which develop on either side of the pharynx

Answer 40

pharyngeal arches

Question 41

In the future trunk region, the paraxial mesoderm also forms bands of cells, these bands soon segment into ____________, block-like condensations of mesoderm

Answer 41

somites

Question 42

What is the hallmark of making vertebrae?

Answer 42

somites

Question 43

In addition to the notochord, some cells derived form the primitive node form the....

Answer 43

paraxial mesoderm

Question 44

In addition to the notochord, some cells derived form the primitive node form the paraxial mesoderm. Close to the primitive node, this cell population appears as a thick, longitudinal column of cells. Each column is continuous laterally with the _____________ mesoderm, which gradually thins into a layer of ___________ mesoderm

Answer 44

intermediate, lateral

Question 45

Toward the end of the 3rd week, the paraxial mesoderm differentiates, condenses, and begins to divide into paired cuboidal bodies, the somites, which form in a craniocaudal sequences. These blocks of mesoderm are located on....

Answer 45

each side of the developing neural tube

Question 46

The size and shape of the somites are determined by....

Answer 46

cell-cell interactions

Question 47

By the end of the 5th week, ___________ pairs of somites are present

Answer 47

42-44 (on L/R side)

Question 48

The first pair of somites forms/condenses on about day _____ at the head-trunk border. The remainder form in cranial-caudal progression at a rate of about ______ a day

Answer 48

20, 3-4 (pairs)

Question 49

What do somites give rise to?

Answer 49

-most of the axial skeleton including the vertebral column and part of the occipital bone of the skull -the voluntary musculature of the neck, body walls, and limbs -the dermis of the body

Question 50

T/F: formation and segregation of somites are of major importance in organization of the body structure

Answer 50

TRUE

Question 51

When somites first from mesoderm, they exist as a ______ of mesoderm

Answer 51

ball

Question 52

Cells in the ventral and medial walls of the somite lose their epithelial characteristics and move their position to surround the neural tube and notochord. Collectively, these cells form the ______________ that will differentiate into the vertebrae and ribs

Answer 52

sclerotome

Question 53

Cells at the dorsomedial and ventrolateral regions differentiate into muscle precursor cells- ?

Answer 53

myotome

Question 54

Cells that remain between sclerotome and myotome will form the....

Answer 54

dermatome

Question 55

In addition to the notochord and paraxial mesoderm, both of which form in the head and trunk, 2 other subdivisions of mesoderm form in the trunk only:

Answer 55

intermediate and lateral plate mesoderm

Question 56

The notochord forms and then what? List each mesoderm in order

Answer 56

-notochord -paraxial mesoderm -intermediate mesoderm -lateral plate mesoderm (splanchnic and somatic mesoderm) all of these are in a "line" above the endoderm from medially to laterally so notochord in center, paraxial on left/right of notochord, and so on

Question 57

Immediately lateral to somites is the intermediate mesoderm. This produces parts of what systems?

Answer 57

urinary and genital system

Question 58

Lateral to the intermediate mesoderm is a flattened sheet called the...

Answer 58

lateral plate mesoderm

Question 59

The lateral plate mesoderm splits into 2 layers. What are they?

Answer 59

1) ventral layer associated w/ the endoderm also known as splanchnic mesoderm which becomes visceral structures 2) dorsal layer associated with the ectoderm known as somatic mesoderm forms the inner lining of the body wall

Question 60

The splanchnic layer forms the __________, and the somatic layer forms part of the lining of the pericardial cavity

Answer 60

heart wall

Question 61

When does the CNS start to form?

Answer 61

week 3 of development

Question 62

The ectoderm just above the primitive node thickens to form a _______________. The ectodermal cells thicken to become neuroepithelial cells (________________). The neural plate forms first at the cranial end of the embryo and then differentiates in a cranial to caudal direction

Answer 62

neural plate, neuroectoderm

Question 63

The neuroectoderm of the neural plate gives rise to the....

Answer 63

CNS

Question 64

On approximately the 18th day of development, the neural plate invaginates along its central axis to form a longitudinal median neural groove. As the groove dips down/gets deeper, the side have neural folds. The folds are more prominent first at the cranial end. The neural folds move together and fuse, converting the neural plate into the....

Answer 64

neural tube

Question 65

What is A?

Answer 65

Question 66

What is B?

Answer 66

Question 67

What is C?

Answer 67

Question 68

What is D?

Answer 68

Question 69

What is E?

Answer 69

Question 70

What is F?

Answer 70

Question 71

What is A?

Answer 71

Question 72

What is B?

Answer 72

Question 73

What is C?

Answer 73

Question 74

What is D?

Answer 74

Question 75

What is E?

Answer 75