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Respiratory HQ > Introduction to Embryology > Flashcards

Introduction to Embryology Flashcards

1
Q

Into what three phases can the development of the human be divided, and at what week numbers do they occur

A

Pre-embryonic (0-3 weeks)

Embryonic (4-8 weeks)

Foetal (9-40 weeks)

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2
Q

What are the names of the parent cells of a sperm and ovum respectively

A

Sperm = Spermatogonium

Ovum = Oogonium

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3
Q

What part of the sperm enters to egg to fertilise it and create a zygote

A

the pronucleus (only the part containing genetic material)

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4
Q

What is the next stage of development after multiple mitotic divisions occur in the zygote

A

Morula formation

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5
Q

What is a blastocyst and how is it formed

A
  • the next stage after the morula
  • blastocystic cavity forms with an inner cell mass and a outer lining of cells (trophoblast)
  • when the central core of cells in the morula can no longer get nutrition
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6
Q

How does the zygote/morula/blastocyst reach the uterine cavity (uterus)

A

using ciliated epithelium in the fallopian/uterine tube

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7
Q

Why may cilia function in the fallopian tube be abnormal, possibly leading to an ectopic pregnancy

A
  • infection
  • pelvic inflammatory disease
  • …
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8
Q

What happens during week 2 of the pre-embryonic phase

A
  • implantation occurs in the endometrium
  • placenta develops
  • cells from the inner cell mass of the blastocyst form a bilaminar disc
  • sacs/membranes/cord for conceptus nourishment begin to form
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9
Q

What is the chorion formed from

A

the trophoblast cells (outer cell mass of blastocyst)

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10
Q

What is the function of the chorion

A
  • implantation using chorionic villi
  • will form part of placenta
  • secretes human chorionic gonadotropin (hCG)
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11
Q

What is the function of hCG

A

tells the ovary to continue the production of oestrogen/progestrone to maintain the endometrium

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12
Q

What happens to the inner cell mass of the blastocyst

A

grows down into the blastocystic cavity and flattens to form a two-layered disc called the bilaminar disc

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13
Q

What two layers form the bilaminar disc and what two cavities do they create

A
  • made up of the epiblast (superior) and the hypoblast (inferior) layers
  • separates the amniotic cavity (superior) and the yolk sac (inferior)
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14
Q

What is the allantoic cavity

A

another cavity formed in the developing human that contains waste

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15
Q

What are the functions of the placenta

A
  • foetal nutrition
  • gas/waste transport
  • immune constituents
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16
Q

Describe the foetal side of the placenta

A
  • smooth

- has the foetal blood vessels and the end of the umbilical cord

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17
Q

Describe the maternal side of the placenta

A
  • rough (chorionic villi)

- has the maternal blood vessels

18
Q

How do fraternal/dizygotic twins come about

A
  • two separately fertilised zygotes
  • different genes
  • two placentae
19
Q

How do identical/monozygotic twins come about

A
  • one zygote that divides to give two embryos
  • same genes
  • share a placenta
20
Q

What happens in week 3 of the pre-embryonic phase

A
  • gastrulation
  • neurulation
  • somite development
21
Q

What is the primitive streak and how is it formed

A
  • invaginated cells

- formed in the midline of the epiblast by the invagination

22
Q

What is gastrulation

A

the formation of the three germ layers (ectoderm/mesoderm/endoderm)

23
Q

How does gastrulation occur

A
  • epiblast cells migrate into the space between the epiblast and hypoblast (mesoderm)
  • cells continue to displace the hypoblast (endoderm)
24
Q

What is the collective name for the three germ layers

A

the trilaminar disc

25
Q

What is neurulation

A

formation of the neural tube

26
Q

How does neurulation occur

A
  • cells sink from the primitive streak in the ectoderm sink down to form a solid tube in the mesoderm called the notochord
  • the notochord induces neural tube formation in the ectoderm
  • ectoderm thickens to form the neural plate
  • neural plate sinks down to form a neural tube
  • will become the brain and spinal cord
27
Q

What does the neural tube cause in the mesoderm

A
  • induces it to thicken

- separates into three parts

28
Q

Name the three parts of the mesoderm that are created via signals form the neural tube

A
  • paraxial mesoderm
  • intermediate plate mesoderm
  • lateral plate mesoderm
29
Q

Which part of the mesoderm forms the somites

A

the paraxial mesoderm

30
Q

What does the lateral plate mesoderm in turn divide into

A
  • somatic end (superior)

- splanchnic end (inferior)

31
Q

What is the name of the space in between the somatic and splanchnic ends of the lateral plate mesoderm

A

the intraembryonic coelom

32
Q

What happens during the embryonic phase of development

A
  • lateral folding (into a tube) completes
  • somites differentiate further
  • limb buds form
  • …
33
Q

What happens in the lateral folding of the embryo

A
  • the now very differentiated trilaminar disc becomes too heavy and begins to fold down
  • the endoderm (gut), somatic mesoderm and splanchnic mesoderm join at the distal end to form a long tube
34
Q

What folding is occurring at the same time as lateral folding

A

head and tail folding on the midsagittal sections

35
Q

How do the somites develop further

A

each one splits again to form;

  • a dermotome (will form the dermis of the skin)
  • a myotome (will form muscles)
  • a sclerotome (will form bones/vertebrae)
  • they all take their nervous innervations with them during lateral folding
36
Q

What is teratology

A

the study of when things go wrong during development

37
Q

What are teratogens

A

environmental factors that cause abnormal development

38
Q

What is the main cause of abnormal development

A

unknown

39
Q

During what stage in development is the unborn child most sensitive to teratogens

A

weeks 3-8

40
Q

How can malformations be diagnosed prenatally

A
  • blood
  • ultrasound
  • invasive testing of chorionic villi
41
Q

How can malformations be diagnosed postnatally

A
  • hip stability
  • testes descent
  • fingers and toes
  • hearing

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