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Systems: Respiratory AB > 1/2. Embryology > Flashcards

1/2. Embryology Flashcards

(78 cards)

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1
Q

What is embryology?

A

The study of embryos

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2
Q

What are the 3 stages of the development of a human?

A
  • Pre-embryonic phase 0-3 weeks
  • Embryonic phase 4-8 weeks
  • Foetal phase 9-40 weeks
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3
Q

What are the parent cells called that produce sperm and ova?

A
  • Spermatogonium

- Oogonium

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4
Q

What is the processes that produce sperm and ova called?

A
  • Spermatogenesis

- Oogenesis

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5
Q

What is the end product of meiosis?

A

-4 unique sperm
OR
-1 ovum and 3 polar bodies

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6
Q

What happens during fertilisation

A
  • Several sperm surround the ovum, only one penetrates.

- Pro nucleus of sperm enters and fuses with the pro nucleus of ovum to give a diploid cell called the zygote

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7
Q

What happens during week 1 of pre-embryonic phase.

A
  • Zygote is formed; divides to form a blastocyst

- Moves through uterine tube to reach uterine cavity

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8
Q

What is the zygote?

A
  • 1st cell in the body

- Diploid

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9
Q

Why are zygotes genetically unique?

A

It has 23 of the mothers and 23 of the fathers chromosomes

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10
Q

Where do the mitochondria cell organelles come from?

A

The mother

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11
Q

What happens to the zygote?

A

Cell divides by mitosis to form a solid ball of cells called the morula

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12
Q

What is an example of a mitochondrial inherited disease?

A

Lebers hereditary Optic Neuropathy which causes blindness

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13
Q

Why does a morula develop into a blastocyst?

A
  • As the number and size of cells increases, getting nutrition to the central core of cells starts to become difficult.
  • Therefore a cavity develops called the blastocystic cavity
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14
Q

What does a blastocyst look like?

A
  • Cavity- blastocystic cavity
  • Cells accumulate at one end to form an inner cell mass
  • The outer lining is called the trophoblast
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15
Q

Endometrium

A

Lining of the womb

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16
Q

What aids in the movement of the zygote to uterus?

A

Uterine tubes have ciliated epithelium to help the ovum move through the reproductive system

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17
Q

How long does the first cell division take?

A

36 hours

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18
Q

What happens to the time of cell divisions?

A

Take less time with each successive division

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19
Q

What happens around day 5/6 of the pre-embryonic stage?

A

The blastula has formed and has reached the uterine cavity ready to implant

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20
Q

When might an ectopic pregnancy occur?

A

If the cilia function is abnormal

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21
Q

What happens during week 2 of the pre-embryonic phase?

A
  • Implantation occurs in the uterine endometrial layer and placenta begins to develop
  • Cells that later form the embryo form a bilaminar disc
  • Sacs, membranes and cord to nourish the human conceptus start to form
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22
Q

What does the trophoblast ultimately form?

A

Chorion and develops finger like processes: chorionic villi

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23
Q

What does the chorion do?

A
  • Implantation process
  • Forms part of the placenta in due course
  • Secretes human Chorionic gonadotropin (HCG)
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24
Q

What does HCG do?

A

Sends signal to the ovary to keep producing oestrogen and progesterone to ensure the endometrium is not shed

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25
What is used to detect pregnancy?
HCG
26
What happens at around 7 days?
The blastocyst begins to burrow into the uterin wall
27
What plays an important role in burrowing?
The chorion
28
Decidua basalis
Part of the endometrium deep to the implanted conceptus
29
What happens to maternal blood and urine levels of HCG?
They increase till around 12 weeks gestation
30
What happens to the inner cell mass?
The cells of the inner cell mass form a 2-layered flat disc called the bilaminar disc
31
What 2 cavities form?
- Amniotic cavity | - Yolk sac
32
What are the main functions of the placenta?
- Foetal nutrition - Transport of waste and gases - Immune
33
Describe the foetal part and surface of the placenta.
Smooth with foetal blood vessels and end of umbilical cord
34
Describe the maternal part of the placenta.
Decidua basalis of endometrium. Rough and has maternal blood vessels
35
When does the placenta mature?
Matures by 18-20 weeks
36
How much does the placenta weigh?
1/6 of the foetus
37
How do fraternal/dizygotic twins occur?
- 2 ova release, 2 sperms which leads to 2 separate zygotes - Different genetic makeups, 2 plancentae - Can run in families
38
How do identical/monozygotic twins occur?
- 1 ovum, 1 sperm, 1 zygote initially which divides into 2 and each cell develops into a different embryo - Same genetic make up share 1 placenta (might/might not share amniotic and chorionic sac)
39
Summarise the progress of the conceptus up till the end of week 2.
- Fertilisation - Zygote - Morula - Blastocyst with inner cell mass - Bilaminar disc with amniotic cavity above and yolk sac below
40
Summarise where everything takes place up until week 2.
- Morula reaches uterine cavity - Blastocyst implants - Outer cells form chorionic villi which help implantation - Decidua basalis forms - Placental formation begins
41
What occurs during week 3 of the pre-embryonic stage?
- Formation of germ layers - Formation of neural tube - Development of somites - Early development of CVS
42
Gastrulation
Formation of germ layers
43
Neurulation
Formation of neural tubes
44
Primitive streak
Depression formed in the midline of the epiblast by the dipping in of cells
45
What is formed alongside the primitive streak?
The axis of the embryo
46
How are germ layers formed?
- Epiblast cells migrate into space between epiblast and hypoblast layers - Cells then displace hypoblast
47
What are the 3 germ layers formed?
- Ectoderm - Mesoderm - Endoderm
48
What do the 3 germ layers form?
Trilaminar disc
49
When do cells become specialised?
When the germ layers are formed
50
Notochord
Solid tube of cells
51
How is the notochord formed?
Cells from the primitive streak sink down and the notochord is formed at the mesoderm
52
What does the notochord do?
Induces ectodermal cells in the midline to form a neural tube
53
How is the neural tube formed?
Neural plate sinks down
54
What does the neural tube do?
Induces the mesoderm to thicken
55
Once thickened what happens to the mesoderm?
It separates into 3 parts
56
What 3 parts does the mesoderm separate into?
- Paraxial mesoderm - Intermediate mesoderm - Lateral plate mesoderm
57
What happens to the lateral plate mesoderm?
It splits to form a somatic and splanchnic mesoderm
58
What is the space between the somatic and splanchnic mesoderm called?
Intraembryonic coelm
59
What divides to form somites?
Paraxial mesoderm
60
What becomes the urogenital system?
Intermediate plate mesoderm
61
What becomes the body cavity and coverings?
Lateral plate mesoderm
62
What occurs during weeks 4-8, embryonic stage?
-Folding into a tube completes -Neural tube development -Heart starts to beat on day 24 -Gut formation from endoderm -Urogenital system formation from intermediate mesoderm -Body cavities from lateral plate mesoderm -43 pairs of somites form in the paraxial mesoderm and differentiate further Limb buds form -Neck development- pharyngeal arches
63
What are the 3 sections that each somite divides into?
- Dermatome - Myotome - Sclerotome
64
What do the dermatomes develop into?
Dermis of skin
65
What do the myotomes develop into?
Muscles
66
What do the sclerotomes develop into?
Bones including vertebrae
67
Teratology
Study of when things go wrong during development
68
Teratogens
Environmental factors that cause abnormal development
69
What are examples of things that can go wrong during pregnancy?
- Congenital rubella syndrome casued by contraction of German measles when pregnant - Malformed limbs due to maternal use of Thalidomide
70
What are the causes of abnormal development?
- Unknown aetiology 60% - Multifactorial 20% - Environmental 10% - Genetic 10%
71
What environmental factors are there?
- Drugs- prescription/other - Alcohol - Tobacco - Infectious agents: ToRCH can transfer through placenta and affect developing embryo - Others, e.g radiation
72
What does ToRCH stand for?
- Toxoplasma - Rubella - Cytomegalovirus - Herpes
73
What genetic factors are there?
- Too many/too few chromosomes (Turner's syndrome- 24 chromosomes single X ) (Down's syndrome- 24 chromosomes- trisomy 21) - Structural changes- deletions of genes, segments of chromosomes
74
What can cause problems related to genetic factors?
- Increased maternal age | - Damage from environmental factors such as radiation
75
How do the risks of teratogenesis differ with time?
- Weeks 1-2: high risk of death, low risk from teratogens - Weeks 3-8: period of greatest sensitivity to teratogens - Weeks 9-38: decreasing sensitivity to teratogens
76
What does the risk posed by a teratogen depend on?
- Exposure during critical periods of development - Dosage of drug/chemical/ factor - Genetic constitution of embryo i.e some more susceptible than others at equivalent doses
77
How can malformations be diagnosed prenatal?
- Blood- AFP - Ultrasound scan- 12 week anomaly scan - Invasive tests- chorionic villus sampling and amniocentesis
78
How can malformations be diagnosed postnatal?
- Hip stability - Testes descent - Fingers and toes - Hearing

Systems: Respiratory AB (39 decks)

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