Review of Embryology Flashcards

(58 cards)

1
Q

What is the first 8 weeks of human development called?

A

Embryonic period

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2
Q

What is the fetal period?

A

After the embryonic period

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3
Q

What happens during the fetal period?

A

Mainly growth and maturation of the developed systems

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4
Q

Where does fertilisation take place?

A

In the ampulla of the fallopian tube

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5
Q

What is the ampulla?

A

The curved end of the fallopian tube

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6
Q

What is the morula?

A

A cluster of cells that cannot grow/multiply any further due to restrictions imposed by the zona pellucida

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7
Q

When does the morula form?

A

At around 96 hours after fertilisation

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8
Q

How many cells form the morula?

A

16

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9
Q

What is the blastocyst?

A

The organisation of cells forming the morula forms the blastocyst by engendering

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10
Q

Describe the maturation of the blastocyst

A

The morular cells in contact with the zona pellucida join together, compact and flatten to become an epithelial layer = trophoblasts

The few inner cells develop into the inner cell mass = embryoblast

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11
Q

What does the trophoblast form?

A

Placenta and nutrients

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12
Q

What does the embryoblast form?

A

Bilaminar cell layer

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13
Q

What is blastulation?

A

Process that happens when blastocyst has fully formed and hatches from the zona pellucida

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14
Q

Described the bilaminar disc

A

There are two layers:

1) Hypoblast (below) - during implantation this forms the umbilical vessel next to the yolk sac
2) Epiblast (above) - during implantation this forms the amniotic cavity

This forms the bilaminar disc

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15
Q

What is the name of the point where the hypoblast and epiblast meet?

A

Embryonic plate

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16
Q

What is implantation?

A

The embryo comes into contact with the uterine mucosa after hatching

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17
Q

When does implantation take place?

A

Adhesion can only occur if the endometrium is in the secretory phase of the menstrual cycle.

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18
Q

What is the importance of the placenta?

A

It serves as the vascular connection between the embryo and the mother

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19
Q

What is gastrulation?

A

The stage of development following implantation

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20
Q

Which event starts the process of gastrulation?

A

The formation of the primitive streak following the proliferation of epiblast cells

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21
Q

What is the primitive streak?

A

Site where the epiblast cells start to migrate

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22
Q

What structure helps to give the primitive streak orientation?

A

Prechordal plate

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23
Q

What is the oropharyngeal membrane?

A

Membrane that gives rise to the opening of the mouth

Formed next to the prechordal plate

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24
Q

What is the cloacal membrane?

A

Membrane that gives rise to the opening of the anus

25
What is the primitive streak?
Linear structure that lies along the rostral-caudal axis formed by epiblast cell movement towards the midline
26
What are two important structures formed by the primitive streak?
The primitive node found in the cranial end of the primitive treak The primitive groove found in the center of the primitive streak
27
What is the function of the primitive node?
Becomes the primitive pit following epiblast cell migration Allows an entry point for the epiblast cells to migrate into the hypoblast layer
28
Describe the process that happens when the bilaminar embryonic disc form the trilaminar layers of the germline
1. The hypoblast layer becomes the endoderm layer as the epiblast cells replace the hypoblast cells 2. After the hypoblast cells become replaced by epiblast cells and form the endoderm, more epiblast cells move down, out and forward forming the mesoderm following differentiation 3. The epiblast is now called the ectoderm
29
What structure do each layer of the trilaminar disc form?
Ectoderm - forms the epidermis, CNS and neural crest cells Mesoderm - form the muskuloskeletal, cardiovascular and urogenital systems Endoderm - forms the lining of the GIT and respiratory tract
30
What is the process of neurulation?
The cells from the primitive pit form an elongated tube moving cranially towards the prechordal plate The tube is found underneath the ectoderm but above the endoderm This forms the notochord
31
What is an important feature about the notochord?
There is no mesoderm between the ectoderm and endoderm where the notochord is found
32
What are the two divisions of the ectoderm?
Neural ectoderm - contributes to future brain and nerve cord Non-neural ectoderm - contributes to the skin and placodes (hair follicles, nails)
33
What is the role of the notochord?
To induce change in the ectoderm above it The notochord produces growth factors that tell the ectodermal cells to proliferate, forming the neural plate
34
What are the divisions of the mesoderm?
Paraxial mesoderm (somite) Intermediate mesoderm Lateral plate mesoderm
35
Describe the formation of the neural tube
The neural plate involutes through the downwards pulling of the mesoderm The edges of the neural plate move towards one another 1. Edges = neural folds 2. Center tube = neural groove The ectodermal cells at the edges of the neural folds differentiate into neural crest cells
36
What are the 3 layers of the neural tube?
1. Marginal zone - forming neurons 2. Marginal zone - forming neuroblasts 3. Neuroepithelial zone - forming the spinal cord
37
Where are the 3 areas in development where there is no mesoderm?
Prechordal plate - oropharyngeal membrane Notochord Cloacal plate - cloacal membrane
38
What day is the neural tube formed?
21
39
What is important for the development of neuropores?
Folate
40
What happens if the embryo does not receive enough folate during development?
Failure to close the anterior neuropore at cranial end forms anencephaly Failure to close the posterior neuropore at caudal end leads to spina bifida
41
What 3 primary vesicles form during the vesiculation of the cranial neural tube?
Prosencephalon Mesencephalon Rhombencephalon
42
What vesicles do the primary vesicles form during their specialisation?
Prosencephalon splits into telencephalon and diencephalon Mesencephalon stays the same Rhombencephalon splints into Metencephalon and Myelencephalon
43
What structure does the telencephalon form?
Cerebrum
44
What structure does the diencephalon form?
Thalamus Subthalamus Hypothalamus Pineal gland
45
What structure does the mesencephalon form?
Midbrain
46
What structure does the metencephalon form?
Pons | Cerebellum
47
What structure does the myelencephalon form?
Medulla
48
Describe what happens to the caudal portion of the neural tube
The cells of the neuroepithelial zone move their way outwards into the marginal zone, forming structures towards the dorsal and ventral parts of the spinal cord The structures in the posterior area formed from the neural tube form the alar plate The structures in the anterior area from the neural tube form the basal plate
49
What does the alar plate form?
The posterior grey horn with sensory neurons
50
What does the basal plate form?
The anterior grey horn with motor neurons
51
What is the remnant of the neural tube in a mature body?
Spinal canal with cerebrospinal fluid
52
What do the neural crest cells differentiate into?
Melanocytes Enterochromaffin cells Enteric nervous system Dorsal root ganglion Pia mater and arachnoid mater Many skull bones Myelin of Schwann cells Parts of the heart
53
What does the mesoderm surrounding the notochord form?
Paraxial mesoderm Intermediate mesoderm Lateral plate mesoderm
54
What does the paraxial mesoderm give rise to?
Somites which divide into: 1. Sclerotome - vertebrak colum 2. Myotome - axial and limb musculature 3. Dermatome - dermis
55
What does the intermediate mesoderm give rise to?
Nephrotome making the kidneys and gonads
56
What does the lateral plate mesoderm giver rise to?
Splanchnic hypomere near the endoderm gives rise to the peritoneum and the gonads The Somatic hypomere near the ectoderm gives rise to the heart, vessels and mesenteries
57
What is the importance of somites?
Somites are the developmental basis of segmentation in vertebrates One somite will give rise to one of the repeating structures: 1. Sclerotome - develop into neural tube, notochord and vertebrae 2. Myotome - forms skeletal muscles of back and limbs, diaphragm 3. Dermatome - forms dermis Somite cells also contribute to tendon formation and endothelium of the aorta and intersegmental arteries
58
What structure divides the abdominothoracic cavity?
The diaphragm divides the abdominothoracic cavity into the superior thoracic and inferior abdominopelvic cavity