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Respiratory > Embryology 1 & 2 > Flashcards

Embryology 1 & 2 Flashcards

1
Q

What are the phases of development of the human?

before birth

A

Pre-embryonic (0-3 weeks)

Embryonic (4-8 weeks)

Foetal (9-40 weeks)

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2
Q

Spermatogenesis is the process of sperm formation

From what cells do sperm form from?

A

Spermatogonium

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3
Q

What is the process of egg formation?

A

Oogenesis

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4
Q

Describe the process of egg formation

A

Oogonium cell in ovaries

Undergoes meiosis

Forms 1 ovum and 3 polar bodies

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5
Q

What is the collective term for the sites of gamete formation?

(testes and ovaries)

A

Gonads

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6
Q

Describe the process of fertilisation

A

Several sperms surround ovum in uterine/fallopian tube, only 1 penetrates

Pronucleus of sperm fuses with pronucleus of ovum

This produces diploid cell - zygote

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7
Q

From a zygote, what is the next stage of development?

A

Morula

Zygote divides by mitosis several times to form a solid ball of cells, a morula

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8
Q

“The morula will develop into a ______”

A

Blastocyst

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9
Q

Describe the structure of a Blastocyst

A

Trophoblast - outer lining of cells

Inner cell mass - accumulation of cells at one side

Blastocyst cavity - hollows it out

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10
Q

Why is it necessary for the morula to develop into a blastocyst?

A

As the morula becomes larger, it becomes difficult to get nutrients to cells in the middle

Forming the cavity and inner cell mass allows nutrients to reach these cells - allowing further growth

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11
Q

Once a zygote is formed, it begins to divide (morula, blastocysts etc)

What else happens?

A

It moves from the uterine tube to the uterine cavity

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12
Q

What facilitates movement through the uterine tubes?

A

Cilia

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13
Q

How long does it take for a zygote to first divide?

A

36 hours

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14
Q

After the first division of a zygote, how does the time taken for successive divisions change?

A

Successive divisions are faster

1: 36 hours
2: 24 hours
3: 12 hours

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15
Q

What happens in the 2nd week of the pre-embryonic phase?

3

A

Implantation of blastocyst into endometrium

Formation of bilaminar disc

Sacs, membranes and cord used for nourishment, form

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16
Q

“In order for implantation to take place, the _______ must develop into _______”

A

Trophoblast

(must develop into)]

Chorion

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17
Q

How does chorion form, and what does it do?

A

Trophoblast divides to form 2 layers

Ultimately develops into chorion

Chorionic villi form - these are finger like processes that implant and eventually form part of the placenta

It also releases HCG

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18
Q

What is HCG?

A

Human chorionic gonadotropin

It is secreted to maintain the endometrium, which is normally shed

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19
Q

What is the muscle that surrounds the uterine cavity?

A

Myometrium

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20
Q

After implantation, what name is given to the endometrium?

A

Decidua

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21
Q

What is the decidua basalis?

A

Part of the endometrium (decidua) that is ‘deep’ to the implanted conceptus

This is where the interface between maternal blood vessels and the placenta will be

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22
Q

After implantation, what happens to the inner cell mass of the blastocyst?

A

They form a 2-layered flat disc called the bilaminar disc:

  • Epiblast (faces the endometrium)
  • Hypoblast (faces away)

This splits the blastocyst cavity:

  • Amniotic sac (epiblast)
  • Yolk sac (hypoblast)
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23
Q

Once implanted, what are the sources of nutrition for the embryo?

A

Yolk sac

Maternal nutrition via placenta

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24
Q

“Waste products from embryonic development are secreted into the _______”

A

Allantoic sac

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25
Q

What sac is the embryo contained in?

A

Amniotic cavity

26
Q

What cavity encases the amniotic cavity, the yolk sac, the allantoic sac and the umbilical cord?

A

Chorionic cavity

27
Q

The placenta has 2 faces

What is the structure of the foetal face?

A

Smooth

Contains foetal blood vessels

Start of the umbilical cord

28
Q

How is the maternal face of the placenta different from the foetal face?

A

Maternal face is rough, and contains maternal blood vessels instead of foetal blood vessels

29
Q

What causes the development of fraternal/dizygotic twins?

A

2 ovum are released, and fuse with 2 sperm

Thus 2 zygotes are formed

2 placentas

30
Q

What causes identical/monozygotic twins to develop?

A

1 ovum and 1 sperm fuse

Zygote splits to form 2 embryos

Shared placenta and may share same amniotic and chorionic sac

31
Q

Summarise what happens in the 3rd week of gestation

A

Gastrulation (formation of germ layers)

Neuralation (formation of neural tube)

Development of somites

Early development of cardiovascular system

32
Q

What happens to the bilaminar disc before gastrulation can happen?

A

Epiblast and hypoblast must separate

Primitive streak must form

This forms in the midline of the epiblast through the dipping of the cells

33
Q

What information does the direction of the primitive streak tell us?

A

Axis of the embryo

34
Q

Describe the process of gastrulation

A

Epiblast cells migrate into the space between epiblast and hypoblast layers

These cells then displace the hypoblast

Trilaminar disc is then formed and cells have become specialised

35
Q

What are the layers that make up the trilaminar disc?

A

Ectoderm
Mesoderm
Endoderm

36
Q

From which layer of cells does the notochord form?

Which part of this layer does it form from?

A

Ectoderm

Forms from the primitive streak

37
Q

What is the notochord?

A

Solid tube of cells

38
Q

What is the function of the notochord?

A

It induces the ectodermal cells in the primitive streak to form the neural plate, which then separates and sinks down to form the neural tube

39
Q

Describe what happens after the neural tube is formed?

A

NT induces the mesoderm to thicken and separate into 3 parts:
Paraxial
Intermediate plate
Lateral plate

40
Q

“The lateral plate mesoderm splits to form a ________ and a ________”

A

Somatic mesoderm and a splanchnic mesoderm

41
Q

What is the name given to the space between the somatic mesoderm and the splanchnic mesoderm?

A

Intraembryonic coelom

42
Q

What do the somites form from?

A

Paraxial mesoderm

43
Q

What forms from the intermediate plate mesoderm?

A

Urogenital system (kidneys and repro)

44
Q

What forms from the lateral plate mesoderm?

A

Body cavity and coverings

45
Q

What is the appearance of the somites compared to the paraxial mesoderm?

A

The PM segments to form the somites

They look like a row of teeth

46
Q

When is the organogenetic period?

A

4th - 8th week

47
Q

How many somites are formed from the paraxial mesoderm?

A

43 pairs

These differentiate further

48
Q

What happens in the organogenetic period?

A

Lateral folding completes

Forebrain, midbrain, hindbrain and spinal cord develop

Heart starts to beat on day 24

Gut formation from endoderm

Urogenital system forms

Body cavities form

Somites form and differentiate

Limb buds form

Neck develops - pharyngeal arches

49
Q

What do the somites develop into?

A

Dermatome
Myotome
Sclerotome

50
Q

What do dermatomes form?

A

Dermis of skin

51
Q

What do myotomes form?

A

Muscles

52
Q

What do sclerotomes form?

A

Bones (inc. vertebrae)

53
Q

What is a teratogen?

A

Environmental factor that causes abnormal development

54
Q

German measles is an example of a teratogen

What is it’s effect?

A

It can cause congenital rubella

55
Q

Give a famous teratogen and it’s effect

A

Thalidomide

Causes malformation of limbs

56
Q

What environmental agents can harm a baby’s development?

A

Alcohol
Tobacco
Other drugs
Radiation

Infectious agents

57
Q

What are the ToRCH agents and why are they significant?

A

Toxoplasma, Rubella, Cytomegalovirus, Herpes

These can be transferred through the placenta and affect the baby’s development

58
Q

Give examples of genetic factors that could affect the development of a baby

A

Too many/few chromosomes

Structural changes/mutations of chromosomes

59
Q

When is the risk of teratogenesis greatest?

A

weeks 3 - 8

60
Q

When is the risk of death highest?

A

Weeks 1 - 2

Low teratogen risk though

61
Q

What are the methods of diagnosing malformations prenatally?

A

Blood - AFP

Ultrasound scan

Invasive tests such as chorionic villus sampling and amniocentesis

62
Q

What are the methods of diagnosing malformations post-natally?

A

Hip stability

Testes (descent)

Fingers and toes

Hearing

Respiratory (32 decks)

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