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Ellie's Body Logistics > Sesh 12: Embryology > Flashcards

Sesh 12: Embryology Flashcards

1
Q

_______ sweep the ovum into the fallopian tube during ovulation.

A

Fimbrae

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2
Q

Why do more sperm travel towards the fallopian tube containing the ovum?

A

This tube releases more heat- sperm heat sensor recognise and move towards via thermotaxis

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3
Q

In which region of the Fallopian tube does fertilisation normally occur?

A

Ampullary region

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4
Q

Sperm must be introduced into the female reproductive tract how long before ovulation?

A

Within 5 days before

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5
Q

Which hormone stimulates sperm capacitation?

A

Progesterone

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6
Q

What is sperm capacitation?

A
  • Sperm are activated inside Fallopian tubes due to chemicals in female reproductive tract
  • Become hyperactive-swim harder and faster
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7
Q

Which cells form the blood-testis barrier in males?

A

Sertoli cells

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8
Q

How can autoimmune orchitis be caused?

A
  • Following removal of inguinal hernia

- Breaches blood-testis barrier, leading to autoantibodies against sperm

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9
Q

Why aren’t sperm rejected by the female?

A

Semen contains immunosuppressants

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10
Q

Why do foetal antigens not evoke an immune response in the mother?

A

Mother’s cell-mediated immunity is suppressed

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11
Q

Define gestational age and its relationship to embryonic age.

A
  • Time since last menstruation

- = embryonic age + 2 wks

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12
Q

What is embryonic age?

A

Time since fertilisation

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13
Q

What is the time from fertilisation til the end of the 2nd week called?

A

Germinal stage

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14
Q

Define the embryonic period.

A

Time from start of 3rd week to end of week 8.

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15
Q

What is the foetal period?

A

Start of week 9 to birth at 38 weeks (embryonic age)

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16
Q

What are the 2 functions of the zona pellucida?

A
  1. Restrict growth, so cells get smaller, as has limited nutrient supply.
  2. Prevents blastocyst adhering to oviduct.
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17
Q

What is the process of the blastocyst losing the zona pellucida called?

A

Hatching

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18
Q

After early cleavage, the zygote becomes a ______.

A

Morula

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19
Q

Approximately what day post-fertilisation does implantation occur?

A

Day 6

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20
Q

Where does implantation most commonly occur?

A

Superior posterior uterine wall- endometrium

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21
Q

What is an ectopic pregnancy?

A

Implantation outside normal area of uterine wall

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22
Q

Where is the most common site of implantation of an ectopic pregnancy?

A

The fallopian tube

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23
Q

If the blastocyst implants in the lower uterus segment, what can occur?

A

Placenta previa- can cause excessive bleeding so need C section

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24
Q

What 2 layers make up the bilaminar embryonic disk?

A
  1. Hypoblast

2. Epiblast

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25
Which 2 cavities does the hypoblast contribute to the formation of?
1. Yolk sac | 2. Chorionic cavity
26
In the 2nd week of development, what 2 layers does the trophoblast differentiate into?
1. Cytotrophoblast | 2. Syncytiotrophoblast
27
What is histiotrophic nutrition?
- Nutrition provided to embryo not from mother's blood supply - Supplies embryo up to 12th week
28
What is haemotrophic nutrition?
- Nutrition provided to embryo by mother's blood | - From 12th week onwards
29
What are the 2 functions of the yolk sac?
1. Provides nourishment at earliest development stages | 2. Provides initial vitelline circulation via a primitive aorta
30
At which week does the yolk sac cease its circulatory function?
Week 12
31
In which stage of development is there the greatest risk of teratogenesis due to environmental exposure or drug therapy?
Embryonic period (start of wk 3- end of week 8)
32
After the foetal period, most systems are less sensitive to teratogenesis by environmental exposure, except which system?
CNS
33
What effects can teratogens have during exposure in the germinal stage?
Lethal
34
During which embryological process are the 3 germ layers established?
Gastrulation
35
During approximately which week does the primitive streak of the epiblast start to form?
Week 3
36
Formation of which structure defines the presence of an individual?
Primitive streak
37
Cells of which layer of the bilaminar embryonic disk move towards the primitive streak and invaginate it?
Cells of the epiblast
38
On which surface of the epiblast does the primitive streak appear?
Dorsal
39
What is the function of cells in the primitive pit?
Co-ordinate gastrulation
40
Cells of the epiblast that displace the hypoblast form the ________.
Endoderm
41
Cells of the epiblast that come to lie between the epiblast and endoderm form the ________.
Mesoderm
42
Cells of the epiblast that remain there form the ________.
Ectoderm.
43
The mesoderm spreads out except 2 regions cranially and caudally which become what respectively?
- Cranial- future mouth- oropharyngeal membrane | - Caudally- future anus- cloacal membrane
44
Why are the oropharyngeal and cloacal membrane avascular?
No mesoderm here, and mesoderm gives rise to CVS.
45
Which structures are derived from ectoderm?
-Structures that maintain contact with environment e.g. nervous system, epidermis
46
Which structures does mesoderm form?
Supporting structures e.g: - Muscle - Cartilage - Bone - CVS
47
Which embryonic layer forms the epithelial lining of the GIT, the respiratory tract and the parenchyma of glands?
Endoderm
48
What is situs inversus and how does it most commonly occur?
- Complete mirror image viscera | - Immotile cilia=commonest cause
49
How is left-right asymmetry of the body achieved?
- During gastrulation - Ciliated cells at the primitive node beat in a characteristic pattern - Causes leftward flow of signalling molecules - Initiates side-specific signalling cascades
50
What cells does the notochord form from?
Mesoderm
51
What effect does the notochord have on overlying ectoderm?
Signals for it to become neuroectoderm and thicken, to form the neural plate
52
How is the neural tube formed?
The edges of the neural plate elevated and curl towards each other
53
Which structure eventually forms the CNS?
Neural tube
54
Which structure(s) eventually form the peripheral NS?
Neural crests- extensions of the neural tube
55
On which day do the first pair of somites appear, and where?
Day 20 in occipital region
56
In what sequence do somites appear?
Craniocaudal
57
At the end of segmentation, how many somites are there, and what is the significance of this?
31...form 31 pairs of spinal nerves.
58
What are the somites below precursors for? 1. Sclerotome 2. Myotome 3. Dermatome
1. Bone 2. Muscle 3. Dermis
59
What is the name of the mesoderm that forms either side of the axis (around the neural tube)?
Paraxial mesoderm
60
What does segmentation achieve?
- Organises mesoderm into repeating structures to form vertebrae ribs etc - Organised into physical and functional segments, which guides their innervation
61
When does folding of the embryo occur?
In week 4
62
What 2 types of folding occur?
1. Cephalocaudal | 2. Lateral
63
What drives cephalocaudal folding?
Growth of the neural tube
64
What drives lateral folding?
Growth of somites
65
What 3 main things does embryo folding achieve?
1. Creates a ventral body wall 2. Suspends embryo within amniotic sac 3. Pulls connecting stalk ventrally

Ellie's Body Logistics (13 decks)

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