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Respiratory BJ > Embryology > Flashcards

Embryology Flashcards

1
Q

When is the Pre-embryonic Phase?

A

0-3 Weeks

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2
Q

When is the embryonic phase?

A

4-8 weeks

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3
Q

When is the foetal phase?

A

9-40 weeks

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4
Q

What do we call the parent cells of meiosis?

A
  • Spermatogonium

- Oogonium

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5
Q

What happens to the cells produced as a result of oogenesis?

A

3 of them degenerate to polar bodies and only one forms an active gamete

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6
Q

What section of the sperm enters the ovum?

A

Only the DNA (pronucleus), it leaves the rest of its cell behind.

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7
Q

What 2 processes occur during week 1?

A

1 - The zygote is formed and eventually divides to form a blastocyst
2 - The pre-embryo moves through the fallopian tube to the uterine cavity

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8
Q

What does a zygote become after dividing?

A

A solid ball of cells called a Morula

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9
Q

What happens to the morula as the number/size of cells increases?

A

It has trouble getting nutrition to the central cells.

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10
Q

How does the morula respond to difficulty getting nutrition to its internal cells?

A

It forms a blastocyst:
1 - Some cells form an outer lining called a trophoblast
2 - others form an Inner Cell Mass in one corner of the blastocyte
3 - This produced a blastocystic cavity inside.

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11
Q

Whats different about each consecutive cell division?

A

Theyre faster, almost as if the cell is learning how to do them

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12
Q

Where does fertilisation occur?

A

In the Fallopian Tube

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13
Q

How does the pre-embryo move through the fallopian tube?

A

Using ciliated epithelium much like the muco-ciliary escalator of the airway

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14
Q

What hapens when the ciliated epithelium of the fallopian tube fails?

A

Etopic Pregnancy occurs, i.e. the pregnancy occurs somewhere other than the uterus, most often the fallopian tube

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15
Q

What 3 things occur during week 2?

A

1 - Implantation & placenta develops
2 - Bilaminar disc forms
3 - Sacs, membranes and cord to nourish the conceptus form

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16
Q

What happens to the trophoblast prior to implantation?

A

The trophoblast divides into 2 layers collectively called the Chorion

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17
Q

What are the 3 functions of the chorian?

A
  • Uses its villi in the implantation process
  • Eventually forms part of the placenta
  • Secretes HCG
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18
Q

What is the function of Human Chorionic Gonadotropin?

A

HCG is secreted by the chorian.
It stimulates the ovary to continue producing the hormones that maintain the endometrium (effectively preventing the monthly ritual of vaginal blood letting)

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19
Q

What do clinicians use HCG for?

A

Detecting pregnancy

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20
Q

When/how does implantation begin?

A

~7 days the blastocyte begins burrowing into the uterine wall (endometrium) using the Chorion

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21
Q

What do we call the part of the endometrium deep to the implanted conceptus?

A

The decidua Basalis

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22
Q

How do HCG levels change over time?

A

Maternal HCG levels increase till ~12 weeks.

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23
Q

What is the muscular wall surroundin the endometrium called?

A

The Myometrium

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24
Q

What happens to the Inner Cell Mass once implanted?

A

The inner cell mass forms a bilaminar disc within the conceptus

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25
Q

What are the layers of cavity & cells formed by the inner cell mass?

A

Inner cell mass forms a bilaminar disc.

Uterus -> endometrium direction:
Yolk Sac -> Hypoblast -> Epiblast -> Amniotic Cavity

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26
Q

What is the function of the allantoic cavity?

A

It holds the embryos waste. So it grows as the yolk empties.

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27
Q

What are the functions of the placenta?

A
  • Foetal Nutrition
  • Waste/gas Transport
  • Immunity
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28
Q

Describe the 2 surfaces of the placenta

A

The inner foetal surface is smooth with foetal blood vessels

The outer maternal surface is the decidua basalis of the endometrium. Its rough with maternal blood vessels.

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29
Q

How do fraternal (Dizygotic) twins develop?

A

2 Ova are released and 2 sperm get to them resulting in 2 seperate zygotes.
Therefore they have different genetic makeups & form 2 placentae.

30
Q

How do identical/monozygotic twins develop?

A

1 ovum -> 1 zygote
It divides in 2 & then each cell develops into seperate embryos.
Share genetic makeup & 1 placenta.

31
Q

What things happen during week 3?

A
  • Gastrulation
  • Neurulation
  • Somite development
  • Early cardiovascular development
32
Q

What are gastrulation & neurulation?

A 
Gastrulation = Germ layer formation
Neurulation = Neural tube formation
33
Q

What is the primitive streak & how does it form?

A

The primitive streak is a dip in the midline of the epiblast that forms by invagination of the cells.

34
Q

What do we learn once the primitive streak has formed?

A

The axis of the embryo. Helps us identify the ‘head’ & ‘tail’ ends.

35
Q

How do the 3 germ layers form?

A

Cells from the primitive streak migrate into the space between the layers and then displace the hypoblast.

36
Q

How do the 3 germ layers relate to the original bilaminar disc?

A

The ectoderm replaces the epiblast
The mesoderm sits between the 2
The endoderm replaces the hypoblast

37
Q

What do we call the 3 germ layers together?

A

A trilaminar disc

38
Q

In what way are the germ layer cells specilaised?

A

They are now destined to form certian structures

39
Q

Where is the notochord located?

A

Between the mesoderm & endoderm

40
Q

How does the notochord form?

A

Cells from the primitive streak sink down and form a solid tube along the layer

41
Q

What does the notochord do?

A

Induces ectoderm cells in the midline to form a neural plate

42
Q

What happens to the neural plate?

A

It sinks to between the ectoderm & mesoderm and forms a neural tube

43
Q

What does the neural tube do to the mesoderm?

A

It induces the mesoderm to thicken and split into 3 sections on either side of the tube

44
Q

What are the 3 sections of mesoderm?

A

Paraxial Mesoderm
Intermediate Plate Mesoderm
Lateral Plate Mesoderm

45
Q

What happens to the lateral plate mesoderm after separating from the rest of the mesoderm?

A

It splits into 2, remaining connected at the medial end.

It forms the somatic mesoderm & splanchnic mesoderm

46
Q

What do we call the space between the somatic & splanchnic mesoderm?

A

The intraembryonic coelom

47
Q

What is the intermediate plate mesoderm destined to become?

A

The urogenital system. i.e. the kidneys & reproductive systems

48
Q

What happens to the paraxial mesoderm after separating from the rest of the mesoderm?

A

It separates further into somites.

49
Q

What comes of a somite?

A

Each somite divides into 3 parts which will become:
1 - A dermatome of skin (dermis)
2 - A myotome of muscle
3 - A sclerotome of bones

50
Q

Why does each somite develop to form a specific dermatome?

A

Because they are ordered and so each relates to a specific vertebra & spinal nerve.

51
Q

What happens to the lateral mesoderm in the 4th-8th weeks?

A

The lateral mesoderm becomes heavy and begins to fold inwards, eventually forming a ring with the opposite lateral mesoderm.

52
Q

What is the result of lateral folding of the embryo

A

The embryo now forms a ring, this produces the foetal position we all know and love so much

53
Q

What happens to the endoderm due to lateral folding?

A

It forms a tube at the centre of the embryo which will eventually form the respiratory system & Gut.

54
Q

which section of the lateral mesoderm will be “inside” and which “outside” after lateral folding?

A

The splanchnic mesoderm will be ‘inside’ bordering the endoderm.
The somatic mesoderm will be ‘outside’ bordering the ectoderm.

55
Q

What section of skin does the ectoderm form?

A

The epidermis of the skin

The neural Tube

56
Q

What body parts are evenutally formed by the lateral plate mesoderm?

A

The peritoneum
Pleura
Body Cavities.

57
Q

Define Teratology?

A

The study of congenital abnormalities & abnormal formations

58
Q

What is a teratogen?

A

An environmental factor that causes abnormal development (teratogenesis)

59
Q

Give some examples of teratogens:

A

German measles contracted while pregnant -> Congenital Rubella Syndrome
Use of thalidomide while pregnant -> Malformed Limbs

60
Q

What causes most abnormal development:

A

In most cases we don’t know but many are:

  • Environmental
  • Genetic
  • Multifactorial
61
Q

What are some types of teratogen?

A

Drugs (Inc. Alcohol/Tobacco)
Infectious agents (ToRCH)
Radiation

62
Q

What does ToRCH stand for?

A 
Toxoplasma
Rubella
Cytomegalovirus
Herpes
All infectious agents that can transfer through placenta and affect the embryo
63
Q

What genetic factors can cause teratogenesis?

A

Abnormal chromosome no.

Structural changes to chromosomes

64
Q

What can cause genetic problems leading to abnormal development?

A
  • Increased maternal Age

- DNA damage due to enviromental factors (e.g. radiation)

65
Q

How does the risk of teratogenesis vary over the pregnancy?

A

Weeks 1-3: A high risk of death if exposed to teratogens
Weeks 4-8: Highest sensitivity to teratogens
Weeks 9-38: Decreasing sensitivity

66
Q

What factors influence the risk posed by a teratogen?

A

The Dosage
The genetics of the embryo, some are more/less susceptible
The period of development

67
Q

What kind of prenatal tests can be done to diagnose an abnormality?

A

Blood Tests
Ultrasound scans
Chorionic Villus Sampling
Amniocentesis

68
Q

Why dont we do chorionic villus sampling & amniocentesis often?

A

Very invasive & therefore dangerous

69
Q

What do we look for on a prenatal blood test?

A

The mothers alpha-foetal protein level

70
Q

What is tested postnatally to check for abnormal growth?

A

The babies hip stability
The descent of the testes
Fingers/Toes
Hearing

Respiratory BJ (31 decks)

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