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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
Q

Which 2 cavities does the hypoblast contribute to the formation of?

A
  1. Yolk sac

2. Chorionic cavity

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26
Q

In the 2nd week of development, what 2 layers does the trophoblast differentiate into?

A
  1. Cytotrophoblast

2. Syncytiotrophoblast

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27
Q

What is histiotrophic nutrition?

A
  • Nutrition provided to embryo not from mother’s blood supply
  • Supplies embryo up to 12th week
28
Q

What is haemotrophic nutrition?

A
  • Nutrition provided to embryo by mother’s blood

- From 12th week onwards

29
Q

What are the 2 functions of the yolk sac?

A
  1. Provides nourishment at earliest development stages

2. Provides initial vitelline circulation via a primitive aorta

30
Q

At which week does the yolk sac cease its circulatory function?

A

Week 12

31
Q

In which stage of development is there the greatest risk of teratogenesis due to environmental exposure or drug therapy?

A

Embryonic period (start of wk 3- end of week 8)

32
Q

After the foetal period, most systems are less sensitive to teratogenesis by environmental exposure, except which system?

A

CNS

33
Q

What effects can teratogens have during exposure in the germinal stage?

A

Lethal

34
Q

During which embryological process are the 3 germ layers established?

A

Gastrulation

35
Q

During approximately which week does the primitive streak of the epiblast start to form?

A

Week 3

36
Q

Formation of which structure defines the presence of an individual?

A

Primitive streak

37
Q

Cells of which layer of the bilaminar embryonic disk move towards the primitive streak and invaginate it?

A

Cells of the epiblast

38
Q

On which surface of the epiblast does the primitive streak appear?

A

Dorsal

39
Q

What is the function of cells in the primitive pit?

A

Co-ordinate gastrulation

40
Q

Cells of the epiblast that displace the hypoblast form the ________.

A

Endoderm

41
Q

Cells of the epiblast that come to lie between the epiblast and endoderm form the ________.

A

Mesoderm

42
Q

Cells of the epiblast that remain there form the ________.

A

Ectoderm.

43
Q

The mesoderm spreads out except 2 regions cranially and caudally which become what respectively?

A
  • Cranial- future mouth- oropharyngeal membrane

- Caudally- future anus- cloacal membrane

44
Q

Why are the oropharyngeal and cloacal membrane avascular?

A

No mesoderm here, and mesoderm gives rise to CVS.

45
Q

Which structures are derived from ectoderm?

A

-Structures that maintain contact with environment e.g. nervous system, epidermis

46
Q

Which structures does mesoderm form?

A

Supporting structures e.g:

  • Muscle
  • Cartilage
  • Bone
  • CVS
47
Q

Which embryonic layer forms the epithelial lining of the GIT, the respiratory tract and the parenchyma of glands?

A

Endoderm

48
Q

What is situs inversus and how does it most commonly occur?

A
  • Complete mirror image viscera

- Immotile cilia=commonest cause

49
Q

How is left-right asymmetry of the body achieved?

A
  • 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
Q

What cells does the notochord form from?

A

Mesoderm

51
Q

What effect does the notochord have on overlying ectoderm?

A

Signals for it to become neuroectoderm and thicken, to form the neural plate

52
Q

How is the neural tube formed?

A

The edges of the neural plate elevated and curl towards each other

53
Q

Which structure eventually forms the CNS?

A

Neural tube

54
Q

Which structure(s) eventually form the peripheral NS?

A

Neural crests- extensions of the neural tube

55
Q

On which day do the first pair of somites appear, and where?

A

Day 20 in occipital region

56
Q

In what sequence do somites appear?

A

Craniocaudal

57
Q

At the end of segmentation, how many somites are there, and what is the significance of this?

A

31…form 31 pairs of spinal nerves.

58
Q

What are the somites below precursors for?

  1. Sclerotome
  2. Myotome
  3. Dermatome
A
  1. Bone
  2. Muscle
  3. Dermis
59
Q

What is the name of the mesoderm that forms either side of the axis (around the neural tube)?

A

Paraxial mesoderm

60
Q

What does segmentation achieve?

A
  • Organises mesoderm into repeating structures to form vertebrae ribs etc
  • Organised into physical and functional segments, which guides their innervation
61
Q

When does folding of the embryo occur?

A

In week 4

62
Q

What 2 types of folding occur?

A
  1. Cephalocaudal

2. Lateral

63
Q

What drives cephalocaudal folding?

A

Growth of the neural tube

64
Q

What drives lateral folding?

A

Growth of somites

65
Q

What 3 main things does embryo folding achieve?

A
  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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