Embryology week 16 Flashcards
(51 cards)
1
Q
What is Gastrulation
A
- A formative process that establishes the three germ layers
2
Q
Name the 3 germ layers
A
- Ectoderm
-Mesoderm
-Endoderm
3
Q
What is the purpose of Gastrulation(2)
A
- It converts the bilaminar embryonic disc into a trilaminar embryonic disc
-And determines the axial orientation of the embryo
4
Q
What cellular changes are invloved in gastrulation
A
- Cell changes shape
-Rearrangement, movement and changes in adhesion
5
Q
What is the contributions of the Embryonic Mesoderm during gastrulation(2)
A
- Froms the skeletal muscle, blood cells and blood vessel linings
- Gives rise to smooth muscle of visceral organs
6
Q
What is the Primitive Streak and where does it form
A
- The first sign of gastrulation, forming on the epiblast of the bilaminar embryonic disc
7
Q
When does the primitive Streak appear
A
Third week
8
Q
What is the function of the Primitive streak
A
- It establishes the craniocaudial axis, cranial and caudal ends, dorsal and ventral surfaces and the right and left sides of the embryo
9
Q
What is the structures of the Primitive Streak and when do they form
A
- Primtive nodes forms at the cranial ends of ths streak
- Primitive goove and primitve pit form due to invagination of epiblastic cells
10
Q
What does the primitive streak form
A
mesenchymal cells
11
Q
What is the function of the mesenchymal cells in the primitive streak
A
- They form the three layers:
-Ectoderm
-Mesoderm
-Endoderm
12
Q
Explain how each of the germ layers are formed`
A
- The cells displace the hypoblast to form the endoderm
- Remaining epiblast cells from the embrynoic ectoderm
- Mesoderm is formed by epiblastic cells that migrate through through the primitive pit and lie between the epiblast layer
13
Q
When does the primitive streak disappear
A
- End of the fourth week
14
Q
What do remenants of the primitive streak give rise to
A
- Sacrococcygeal Teratoma
- Which causes benign tumours in newborns
15
Q
How is the notochordal process formed
A
- Some mesenchymal cells migrate through the primtive streak
- These cells move cranially from the primitive node and pit , forming the notochordal process
16
Q
What does the notochordal process develops
A
- Lumen, called the notochordal canal
17
Q
Explain the growth(extension) and interaction of the notochordal process with other structures.
A
- The notochordal process extends cranially between the ectoderm and endoderm until it reaches the prechordal plate.
18
Q
What is the prechordal plate
A
- Small circular area of columnar endodermal cells, where the ectoderm and endoderm are fused
19
Q
What is the function of the prechordal plate
A
- Gives rise to the endoderm
-Acts as a signaling center to regulate the development of cranial structures, including the forebrain and eyes
20
Q
When does the Allantois appear
A
- Around day 16
21
Q
Where does the Allantois extend into
A
-Connecting stalk
22
Q
How does the Allantois Mesoderm from blood vessels
A
- The allantois mesoderm expands beneath the chorion and forms theblood vessels that supply the placenta
23
Q
How does the Allantoic stalk form the umbilical arteries
A
- The blood vessels of the allantoic stalk develop into the umbilical arteries
24
Q
What does the allantoic diverticulum persists as
A
- Urachus
25
What does Neurulation involve
- It involves the formation of the neural plate, enural folds and the closur of the neural tubes
26
When is neurulation completed
- By the end of the fourth week
27
How is the neural plate formed
( starting w the notochord)
- The notochord induces the embryonic ectoderm to thicken , forming the neural plate
28
What day is the neural groove formed
-Day 18
29
How is the neural groove formed
(neural plate)
- The neural plate invagnates to form the neural groove which has neural folds on each side
30
when and how is the neural tubes formed
+ what does it develop into
(neural folds)
- End of the third week
- The neural folds fuse , forming the neural tube
- It develops into the brain vesicle and spinal cord
31
What is the neural crest formed by
Formed by the neural crest cells between the neural tube and surface ectoderm
32
What do the neural crest cells migrate and give rise to
- Meninges
-Melanocytes
-Adrenal medulla
-Sensory ganglia
-Autonomic ganglia
33
Name a severe neural tube defect
- Meroenecephaly
34
What are somites
Are paired cuboidal blocks od mesoderm
35
When does the formation of somites begin
- End of the 3rd week
36
Explain the initial formation of the Somities:
- Formation of somits
-How they appear
- Where they develop near
- The paraxial mesoderm differentiates and condenses to form somits,(blocks of mesoderms)
-Somits appear from head to tail( craniocaudal sequence)
- They develop near the head( occipital region)
37
What do Somites arise from
- Paraxial mesoderm
38
By the end of the 5 week how many somits are present
42-44 pairs
39
What is the function of somites
- Give rise to the axial skeleton( vertebrae, ribs skull)
- Form skeletal muscles
- Give rise to adjacent dermis of the skin
40
What does the intraembryonic coelom develop into and explain
- It develops into the lateral mesoderm and this divides into 2 layers:
- Somatic or parietal layer
-Splanchnic or visceral layer
41
In the intraembryonic coelom formation what does the lateral mesoderm divide into
- Somatic or parietal layer
-Splanchnic or visceral layer
42
What does the parietal layer from the lateral mesoderm in the intaembryonic coelom formation form
- Embryonic body wall-somatopleure
43
What does the visceral layer of the mesoderm from from the lateral mesoderm in the intraembryonic coelom formation
- Embryonic gut-Splanchopleure
44
What is Vasculogenesis
Formation of new vascular channels by angioblasts
45
What is Angiogenesis
- The formation of new vessels by budding and branching from preexisting vessles
46
When does blood formation-Hematogenesis start
5th week
47
Where does the heart and great vessles develop
-In the Cardiogenic area from the primordial heart tube
48
What days does the heart begin to beat
21-22nd day
49
How is the primordial cardiovascular system developed, starting from the tubular heart
- The tubular heat joins with the blood vessels in the embryo, connecting stalk, chorion and the umbilical vesicale to form a primordial cardiovascular system
50
What is the first organ system to reach the function state
- Cardiovascular system
51
when and how can the heart beat be detected
- By ultrasonography
- 5th week
