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Flashcards in Lect 3 Deck (30):
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What occurs during the embryonic period?

Formation of germ layers and organogenesis

1

What events occur in week three?

Week three is the embryonic period.
-
1- gastrulation: forms trilaminar disc
2- neuralation : forms neural tube
3- body folding : embryonic disc folds into more complex shape

2

When does gastrulation, neuralation, and body folding end?

Begin week three! End in week 4!

3

Which cell types are used in gastrulation?

Epiblast

4

What does gastrulation form?

Three germ layers ( trilaminar disc) using epiblasts only!!
1- ectoderm : outer surface
2- mesoderm: migrating middle
3- endoderm: inner cell layer / displace hypoblast

5

Where is the site of epiblast invagination ( gastrulation) ?

Primitive node

6

What are the functions of the primitive node and primitive streak?

Epiblast invagination ; organise layers; determine body axes

7

Which element is the primary migration organiser? ( during gastrulation)

Primitive node

8

What is the function and future feature of the oropharyngeal membrane?

On cephalic end/ future mouth

9

What are the cell migration routes in the trilaminar disc?

Caudal to cephalic ( but get better in cephalic to caudal)

10

During gastrulation what happens to the epiblast?

Epithelial- mesenchymal transformation
Formation of undifferentiated migratory cells : mesenchymal cells

Epithelial : tightly adhered
Mesenchymal : loose, non adherent

11

Explain regression of the primitive streak?

Cephalic to caudal development. Migration is caudal to cephalic so the streak remains the same as the remainder of the organism grows. Tissue proliferation extends to the cephalic end. Matures in cephalic to caudal direction

12

What event contributes to CNS development?

Neuralation ( wk 3-4 )

13

Where is the notochord located?

The notochord ( used in neuralation) is found at the invagination of the primitive node pit ( going toward to oropharyngeal membrane) migrates along midline and stops at pre chordal plate

14

What cells surround the amniotic cavity in wk 3

Ectoderm

Endoderm surrounds the sYS

15

Notochord induces overlaying surface ectoderm to become...

Neuroectoderm

16

Neural folds develop into what structure?

Neural folds gradually creat neural grove and then the neural tube ( tube right above the notochord) tube is comprised of neuroectoderm

17

If the rostrum neuropore fails to close properly what can happen?

Anencephaly ( no head development )

18

What happens when the caudal neuropore fails to close?

Spina bifilar and spina bifilar cystica

19

What does endoderm give rise to?

Gametes, epithelial cell lining : - GI, Liver, pancreas, respiratory airways, and some urogenetal structures

20

Which germ layer produces - hair, nails, glands, epidermis, neural crest,

Ectoderm and the notochord induces neuroectoderm

21

What three diffrentiations of mesoderm are there?

Paraxial ( closest to neural tube) ; intermediate ( middle) ; and Lateral plate ( which yields 2 others - parietal on amniotic cavity side/ and visceral sYS side for organs )

22

Where do somites originate from?

Somites are from paraxial mesoderm, which is from mesoderm,which is from epiblast cells.

23

What do somites give rise to?

Sclerotome ( bone); myotome( muscle) and dermatome ( skin)
Develops cephalic to caudal

24

Which germ layer is responsible for urinary or reproductive issues?

Mesoderm- intermediate mesoderm!

25

What are the two types of body folding?

Lateral and cephalocaudial ( head to tail)

26

What drive body folding?

Later BF : driven by growth of somites
Caphalocaudal BF: driven by growth of neural tube

27

What does the gut tube from from?

Secondary yolk sac! And intraembryonic cavity ( during lateral folding)

28

How does the primitive mouth and heart get to the adult position?

During cephalocaudial body folding ( longitudinal growth of neural tube)

29

What happens at end of embryonic period?

Finish - gastrulation/ neuralation/ and body folding ( end of week 4)
Limbs elongate / rotate / face appears
Organogenesis

This period is greatest risk for brith defects