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module 102: T1 Human Body > principles of embryology > Flashcards

principles of embryology Flashcards

1
Q

What can birth defects be caused by?

A
  • genetic factors
  • environmental factors
  • multifactorial inheritance
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2
Q

What are the categories of birth defects?

A
  • malformations
  • disruption
  • deformation
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3
Q

What is a malformation? Give examples

A
  • intrinsically abnormal developmental process
  • e.g chromosomal abnormalities (trisomy 18)
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4
Q

What is disruption? Give example

A
  • extrinsic interference of the normal development process
  • e.g teratogenic drug
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5
Q

What is deformation? Give examples

A
  • abnormal form due to mechanical factors
  • e.g clubfoot (equinovarus foot)
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6
Q

When is the risk of birth defects highest?

A

around week 5

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7
Q

What are the developmental periods within the pre-natal period?

A
  • embryonic period (0 - 8 weeks)
  • foetal period (9 - 40 weeks)
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8
Q

What are the developmental periods within the post-natal period?

A
  • neonatal (0 - 4 weeks)
  • infancy (4 - 52 weeks)
  • childhood ( 2 yrs - puberty)
  • adolescence (11 yrs - 19)
  • adulthood (19+ yrs)
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9
Q

What are the 5 early events in embyrology?

A
  1. gametogenesis
  2. fertilisation
  3. cleavage
  4. gastrulation
  5. formation of the body plan
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10
Q

What is a gamete?

A

cell with 23 chromosomes (haploid)

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11
Q

What is gametogenesis?

A

the formation of gametes

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12
Q

What is spermatogenesis?

A

the formation of male gametes

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13
Q

When does spermatogenesis start and how does it vary through time?

A
  • starts at puberty
    continues through life
  • decreases with age
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14
Q

How long does each cycle take in spermatogenesis?

A

around 64 days

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15
Q

What is the typical production rate of sperm in spermatogenesis?

A

6.5 million sperm per gram of testicular tissue a day

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16
Q

What is oogenesis?

A

the formation of female gametes

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17
Q

When does oogenesis start and end?

A
  • starts in utero
  • ends at menopause
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18
Q

What happens by week 28-30 in utero (oogenesis)?

A

primary oocytes begin meiosis but arrest in development until puberty

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19
Q

When is the reproductive lifespan determined in females?

A

in fetal life

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20
Q

What is fertilisation? Where does it occur?

A
  • fusion of sperm and oocyte
  • occurs in the ampulla of the uterine tube
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21
Q

What does fertilisation form?

A

a zygote

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22
Q

Describe a zygote

A
  • diploid
  • single cell embryo
  • sex determination
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23
Q

What does fertilisation stimulate oocytes to do?

A

complete meiosis 2

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24
Q

What is cleavage?

A

repeated mitotic divisions of the zygote into blastomeres and then a blastocyte

25
Q

How is the morula formed?

A
  • rapid mitotic cell division with no increase in size
  • 16+ cell forms morula
26
Q

What is the zona pellucida?

A

gelatinous matrix around zygote, keeps cell nice and tight (keeps us safe)

27
Q

What is the trophoblast?

A

after many divisions, the outer layer in touch with the zona pellucida gets called the trophoblast

28
Q

What does the trophoblast do?

A
  • forms embryonic portion of the placenta
29
Q

Describe the trophoblast

A
  • lateral cell surface express tight junctions, gap junctions and desmosomes
  • basal Na/K ATPase pump
30
Q

What happens in ‘hatching’?

A

shedding of the zona pellucida allow future interaction with the endometrial lining of the uterus

31
Q

What are some assisted reproductive technologies?

A
  • in-vitro fertilisation (IVF)
  • intracytoplasmic sperm injections (ICSI)
  • gamete or zygote intrafallopian transfer (GIFT/ZIFT)
32
Q

What happens in in IVF?

A
  • trigger super ovulate (FSH, clomiphene citrate)
  • oocyte harvested and partnered with sperm in vitro
  • zygote cultured then implanted in uterine cavity
33
Q

List the components of a zygote at the beginning?

A
  • polar bodies
  • pronuclei
  • zona pellucida
  • oolemma
34
Q

List the components of a blastocyte?

A
  • zona pellucida
  • inner cell mass (embryoblast)
  • trophoblasts
  • blastocyst cavity
35
Q

What does the inner cell mass (embryblast) differentiate into during implantation?

A
  • epiblasts and hypoblasts
  • they form the bilaminar germ disc
36
Q

What do the trophoblasts differentiate into during implantation?

A
  • syncytiotrophoblast
  • cytotrophoblast
37
Q

What does the blastocyte do before implantation? When does it finally implant?

A
  • floats for around 72 hours before implantation
  • implants 6-8 days post ovulation
38
Q

What are the two steps that happen in the implanted embryo?

A
  • establish primordial uteroplacental circulation
  • formation of the chorionic cavity
39
Q

How does the implanted embryo establish uteroplacental circulation?

A
  • maternal capillaries become sinusoids
  • further invasion of syncytiotrophoblast ruptures capillaries and cells
  • lacunae flood with maternal blood and nutrients
40
Q

In the implanted embryo, how is the chorionic cavity formed?

A
  • extra-embryonic mesoderm fills space between primitive yolk sac/amniotic cavity and cytotrophoblast cells
  • large cavities form and become connected
41
Q

What is an extra-uterine (ectopic) pregnancy?

A

abnormal implantation of embryo

42
Q

What percentage of pregnancies are ectopic

A

2%

43
Q

What percentage of pregnancy related maternal mortality is due to ectopic pregnancy?

A

9%

44
Q

What is gastrulation and when does it occur?

A
  • movement of epiblast cells through the primitive streak to form 3 primary germ layers
45
Q

Which cells do the epiblasts replace to then form the endoderm?

A

hypoblasts

46
Q

What is the ectoderm made from?

A

what’s left of the epiblast layer

47
Q

What does the ectoderm go on to become?

A
  • epidermis of skin (hair, nails, associated glands)
  • nervous system
48
Q

What does the intraembryonic mesoderm become?

A

it divides into 3 layers

49
Q

Which 3 layers does the intraembryonic mesoderm become?

A
  • paraxial
  • intermediate
  • lateral plate
50
Q

What 2 layers does the lateral plate mesoderm divide into?

A
  • somatic layer (dorsal)
  • visceral layer (ventral)
51
Q

What does the paraxial mesoderm become?

A
  • axial skeleton (vertebrae)
  • voluntary (skeletal) muscle
  • part of dermis (back)
52
Q

What does paraxial mesoderm undergo further differentiation to become?

A

somites

53
Q

What do somites differentiate into?

A
  • dermomyotomes
  • sclerotomes
54
Q

What do dermomyotomes do?

A

they form connective tissue and skeletal muscle

55
Q

What do sclerotomes do?

A

they form bone and cartilage (vertebral arch)

56
Q

What does the intermediate mesoderm become?

A

urogenital systems
- kidneys, ureter, trigone of bladder
- gonads, uterus + uterine tubes, superior portion of vagina, ductus deferens

57
Q

What does the somatic part of the lateral plate mesoderm become?

A
  • most of dermis (not in central back)
  • lining of body walls
  • bones of limbs
58
Q

What does the visceral part of the lateral plate mesoderm become?

A
  • cardiovascular system
  • mesothelial covering of organs
  • smooth muscle
59
Q

What does the endoderm become?

A
  • lining of gut
  • lining of respiratory tract
  • lining of bladder and urethra

module 102: T1 Human Body (21 decks)

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