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Anatomy > Embryonic Development > Flashcards

Embryonic Development Flashcards

1
Q

Where does fertilization occur?

A

Ampulla of the uterine (fallopian) tube

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2
Q

How is genetic sex determined?

A

1- Oocyte carrying X chromosome
2- Sperm may carry X or Y chromosome
3- XX: female
4- XY: male

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3
Q

What processes occur during the first week of development?

A

Ovulation to implantation
1- Ovulation of haploid oocyte
2- Sperm penetrates oocyte wall
3- Fertilised oocyte implants on uterine wall

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4
Q

What is the acrosome reaction?

A

1- Process sperm must go through to penetrate the female egg
2- Sperm penetrates corona radiata and zona pellucida by releasing enzymes
3- Sperm fuses with egg and releases its contents
4- Female pronucleus and male pronucleus fuse

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5
Q

What types of RNA does the egg cytoplasm contain?

A

1- Mitochondrial DNA

2- Maternal mRNA

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6
Q

When does the first mitosis begin?

A

After fertilisation

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7
Q

When is cleavage initiated?

A

Within 36 hours of fertilisation

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8
Q

What is a morula?

A

1- Early stage embryo, 3-4 days post fertilisation
2- 16+ cells
3- Solid ball of cells with inner and outer layers
4- Travels along fallopian tube and arrives at uterus 30-40 cells, 3-4 days post fertilisation
5- Zona pellucida intact until time for implantation
6- Outer cells divide to become trophectoderm
7- Some inner cells are trapped and become inner cell mass

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9
Q

Why must the zona pellucida disappear?

A

For implantation on uterine wall

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10
Q

Up to what stage are cells totipotent?

A

Blastocyst stage

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11
Q

What is a blastocyst?

A

1- Early embryo
2- 4-5 days post fertilisation
3- Contain trophectoderm which is outer layer of trophoblast cells
4- Contain inner cell mass which are inner layer of cells
5- Still free and unattached in the uterus

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12
Q

Which cells are removed for genetic testing in the early embryo?

A

5-6 days trophectoderm

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13
Q

When does the embryo bind to the uterus wall?

A

5.5 to 6 days post fertilisation

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14
Q

What part of the embryo binds to the uterus wall?

A

Embryonic pole

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15
Q

How does the embryo bind to the uterus wall?

A

1- Via the embryonic pole
2- MUC-1, anti-adhesion molecule, is suppressed or down regulated
3- This allows the binding of embryo selectins to glyco-components on uterus epithelial cells
4- Integrins, laminin and fibronectin are involved in initial penetration

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16
Q

What three proteins are involved in initial penetration of the embryo to the wall?

A

1- Integrins
2- Laminin
3- Fibronectin

17
Q

When does implantation of the blastocyst start?

A

6-7 days

18
Q

How does the blastocyst implant into the uterine wall?

A

1- Trophoblast becomes ‘invasive’
2- Syncytiotrophoblast and cytotrophoblast help penetrate uterus epithelium
3- Syncytiotrophoblast invade via metalloproteases

19
Q

On day eight, what two layers form in the embryo?

A

1- Epiblast

2- Hypoblast

20
Q

When does the amniotic cavity begin to form?

A

8 days post fertilisation

21
Q

Where does the amniotic cavity begin to form?

A

Within the epiblast

22
Q

On day eight, what do hypoblast cells begin to do?

A

They begin to flow or migrate outwards to coat the blastocyst cavity

23
Q

On day nine,where are hypoblasts found?

A

1- Coating the blastocyst cavity

2- Form primary yolk sac

24
Q

What happens on day nine?

A

1- Hypoblast cells coat blastocyst cavity, forming the primary yolk sac
2- Spaces develop within the syncytiotrophoblast to form trophoblastic lacunae
3- Amniotic cavity has formed within the epiblast
4- Extraembryonic mesoderm begins to form deep to the trophoblast

25
Q

What happens on days eleven and twelve?

A

1- Embryonic disc at bottom of amniotic cavity has two layers
2- Blastocyst burrows completely into endometrium
3- Primitive placental circulation is established by syncytiotrophoblasts eroding through the walls of large maternal capillaries leading to blood bleeding into the trophoblastic lacunae
4- Chorionic cavity forms

26
Q

How is primitive placental circulation established?

A

1- Syncytiotrophoblasts (SCT)
2- SCTs burrow through walls of large maternal capillaries
3- Leads to blood flowing into trophoblastic lacunae

27
Q

When can breakthrough bleeding happen?

A

When primitive placental circulation is established by SCTs

28
Q

What features are established by the end of the second week?

A

1- Two layers, the syncytiotrophoblast and cytotrophoblast form in the trophoblast
2- Epiblast/ectoderm and hypoblast/endoderm form in the inner cell mass
3- Amniotic and chorionic cavities form

29
Q

What is pre-eclampsia?

A 
1- Condition 20 weeks into pregnancy
2- Hypertension
3- Proteinuria
4- Due to poor cytotrophoblast invasion into the spiral arteries, which then keep their muscular walls
5- This leads to hypertension
30
Q

What is ectopic implantation?

A

Implantation of blastocyst outside uterus

31
Q

What is the most common site of ectopic implantation?

A

Ampulla

32
Q

What increases the risk of ectopics?

A

Inflammatory disease of pelvis

33
Q

What are the main causes of congenital malformations?

A

1- Genetic
2- Environmental (least common)
3- Multifactorial or unknown (most common)

34
Q

What are the possible environmental causes of congenital malformations?

A

1- Drugs or chemicals e.g. nicotine, alcohol, chemotherapy
2- Infectious agents e.g. rubella, toxoplasma
3- Ionizing radiation

35
Q

What is foetal alcohol syndrome?

A

1- Disorder spectrum
2- Non-hereditary mental retardation and neurological deficit
3- Due to ingestion of alcohol during pregnancy

36
Q

What consequences does the ingestion of alcohol during pregnancy have?

A 
1- Foetal alcohol syndrome
2- Mental retardation and neurological deficit
3- Cleft lip/palate
4- Small jaw
5- Wide-set eyes
6- Dental abnormalities
7- Digit abnormalities
8- Small head
9- Short stature
10- CNS damage
37
Q

What protects against alcohol damage in the first two weeks?

A

Stemness of cells

38
Q

What damage may be caused by ingestion of alcohol during the 3-6 week period?

A

1- Implantation failure
2- Neurological defects
3- Minor developmental defects in face related to damage on neural crest cells

39
Q

What damage may be caused by ingestion of alcohol during the 6-7 week period?

A

Defects in corpus callosum which is a major hemisphere connection

Anatomy (20 decks)

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