BL - Embryology Flashcards

1
Q

What are the tubes called that connect the ovaries with the uterus?

A

Fallopian tubes

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2
Q

Briefly explain the process of oogenesis.

A
  • oogonium splits into another oogonium and a primary oocyte
  • primary oocyte splits into 1st polar body and secondary oocyte
  • 1st polar body splits to form two more polar bodies (polar body still undergoes mitosis despite having no role)
  • secondary oocyte splits to form secondary polar body and ovum
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3
Q

Where does fertilisation take place usually?

A

The ampullary region of the Fallopian tube

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4
Q

True or false - sperm must be introduced into the female reproductive tract within five days before ovulation?

A

True. Sperm are viable for five days, but secondary oocytes are only viable for 12-24 hours.

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5
Q

What is capacitation?

A

When the tail of the sperm moves faster causing the plasma membrane to alter.

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6
Q

Why is semen not rejected by the body?

A

The body only develops antigens for semen if it is exposed to the blood supply. This means that there are no antibodies for its antigens.

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7
Q

What is the difference between embryonic age and gestational age?

A

Embryonic age is time since fertilisation, while gestational age is time since last menstruation.

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8
Q

What is the “germinal stage”?

A

Time from fertilisation to the end of the second week.

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9
Q

What is the “embryonic period”?

A

Time from third week to end of eighth week

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10
Q

What is the “foetal period”?

A

Beginning of ninth week to birth at 38 weeks.

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11
Q

What is the zona pellucida?

A

A ‘shell’ that surrounds the egg, preventing it from adhering to the oviduct. It must be lost before the blastocyst can implant.

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12
Q

What does the fertilised egg form when it reaches the 16-celled stage?

A

A morula

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13
Q

What forms after the morula?

A

Blastocyst

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14
Q

Where does implantation usually occur?

A

The posterior wall of the upper part of the body of the uterus.

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15
Q

What is an ectopic pregnancy?

A

This occurs when the blastocyst implants in the wrong place, eg the fallopian tube.

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16
Q

What is placenta praevia?

A

This occurs when the placenta forms very close to (or even occluding) the vaginal opening.

17
Q

Why is the second week of development known as the “week of twos”?

A
  • the trophoblast differentiates into two layers
  • the embryoblast forms two layers
  • the hypoblast contributes to the formation of two cavities
18
Q

During which stage of development is the foetus at greatest risk of congenital malformation due to environmental exposure?

A

The embryonic period

19
Q

What appears in the dorsal surface of the epiblast at three weeks?

A

The primitive streak

20
Q

What are the two layers of the “bilaminar disk”?

A
  • epiblast

- hypoblast

21
Q

What are the three layers of the “trilaminar disk”?

A
  • ectoderm
  • mesoderm
  • endoderm
22
Q

What do the two holes in the mesoderm go on to form?

A

The mouth and anus

23
Q

What does the ectoderm form?

A

Organs and structures that maintain contact with outside world, eg nervous system, epidermis

24
Q

What does the mesoderm go on to form?

A

Supporting tissues, eg muscle, cartilage, bone

25
Q

What does the endoderm go on to form?

A

Internal structures eg epithelial lining of GI tract

26
Q

What is situs inversus?

A

Complete mirror image viscera

27
Q

How does the embryonic disk signal which side is left and which is right?

A

Action of ciliated cells at the node results in left-ward flow of signalling molecules. This causes side-specific signalling cascades to be initiated.

28
Q

What is gastrulation?

A

The process of the bilaminar disk being converted to a trilaminar disk. Occurs in third week of development.

29
Q

What is the notochord?

A

A solid rod of cells that runs down the midline, which directs conversion of overlying ectoderm to neurectoderm (beginning of central nervous system).

30
Q

How does the ectoderm over the notochord form the neural tube?

A
  • notochord signals cause overlying ectoderm to thicken
  • neural plate edges elevate out of the plane of the disk and curl towards each other
  • this creates neural tube
31
Q

What are the four different sections of the mesoderm?

A

Paraxial, intermediate, somatic, splanchnic

32
Q

What are somites?

A

Organisation of the parasail mesoderm into segments. The first pair appear at day 20 in the occipital region. There will be 31 in total

33
Q

How do somites form myoterm?

A
  • somites appear as regular block of mesoderm cells around small cavity
  • followed by organised degeneration where ventral wall of somite breaks down and forms sclerotome
  • organisation of dorsal portion forms combined dermomyotome
  • myotome proliferates and migrates, dermatome disperses
34
Q

What are the three somite derivatives?

A
  • DERMATOME (“skin section”, dermis)
  • MYOTOME (“muscle section”, muscles)
  • SCLEROTOME (“hard tissue section”, bones)
35
Q

What are the functions of segmentation?

A
  • Organisation of mesoderm into somites forms repeating structures:
    Vertebrae, ribs, intercostal muscles, spinal cord segments
  • It also guides innervation
36
Q

What is achieved by folding of the trilaminar disk?

A
  • creates a ventral body wall
  • pulls amniotic membrane around the disk (leading to embryo being suspended within amniotic sac)
  • pulls connecting stalk ventrally