Embryology Flashcards

1
Q

gametogenesis types:

A

oogenesis (female)

  • 2 mil primary oocytes at birth
  • 40 000 oocytes by adolescence

spermatogenesis (males)
- after puberty

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2
Q

brief procedure of fertilisation:

A
  • 200-600 mil sperms in cervical os (uterus) after sex
  • sperms pass through female reproductive system
  • fusion of male and female gamete
  • occurs in uterine tube 12-24hrs (after ovulation)
  • secondary oocyte viable 24hrs
  • sperm 48hrs
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3
Q

oocyte linings:

A

corona radiata and zona pelucida

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4
Q

zygote

A

fertilised ovum

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5
Q

dizygotic twins vs monozygotic twins:

A

dizygotic:
2 secondary oocytes fertilised by 2 sperm

monozygotic:
1 egg, 2 sperm in same placenta but different amniotic sacs

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6
Q

how does conjoined twins occur:

A

cell separation not within 8 days after fertilisation, may be conjoined

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7
Q

list first week development:

A
  • fertilisation
  • cleavage
  • morula
  • formation of blastocyst
  • implantation
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8
Q

when does each occur: first-week development (5)

A
  • fertilisation (12-24 hrs) a.o
  • cleavage (30 hrs) a.f
  • morula (3-4 days) a.f
  • blastocyst (4.5-5 days) a.f
  • implantation (6 days) a.f

o-ovulation
f-fertilisation

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9
Q

fertilisation features/ location:

A

near/ in uterine tube

  • muscular uterine contractions help aid sperm
  • cervix open during ovulation
  • cilia push egg to uterus
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10
Q

define zygote:

A

fertilised ovum

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11
Q

cleavage features: define morula and name its membrane

A
  • mitotic cell division of zygote, divide every 6 ish hrs
  • solid cell mass (morula)
  • surrounded by zona pellucida
  • doesn’t grow in size
  • only increase SA
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12
Q

define/ formation of blastocyst features/ location:

A

day 4-5:

  • morula enter uterine cavity
  • uterine milk penetrate morula/ blastomeres and form fluid cavity (blastocyst cavity)
  • removes zona pellucida for embedding

hollow sac in cell mass

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13
Q

two layers of blastocyst and brief info:

A

trophoblast:
- squamous epithelial cells
- nourishes embryo

embryoblast: (inner cell mass)
- shifted to one side, forms the embryo

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14
Q

implantation: features/ location

A

blastocyst attaches to endometrium of uterus, implants onto posterior wall of uterus

endometrial lining (uterus mucous membrane) after implantation of blastocyst (Decidua)

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15
Q

list second week development:

A
  • trophoblast development

- bilaminar embryonic disc (embryoblast)

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16
Q

trophoblast differentiation:

A

2 layers:

  • syncytiotrophoblast
  • cytotrophoblast
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17
Q

syncytiotrophoblast features:

A
  • outer layer, no cell boundary
  • secretes enzymes, can deepen in endometrium,
  • produce HCG (pregnancy hormone)
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18
Q

placenta: function

A
  • organ of pregnancy (after 28wks)
  • exchange of nutrients and waste products btw mother/foetus
  • produces hormones to sustain pregnancy
  • develops from foetal and maternal sources
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19
Q

placenta: features

A

fetal surface:
- smooth with amnion membrane

maternal surface:
- bumpy surface where umbilical cord originates from

20
Q

Bilaminar embryonic disc development: features

A

embryoblast cells differentiate:
- epiblast (amnion develops)

  • hypoblast (yolk sac develops from migration of hypoblast cells)
21
Q

list third week development:

A
  • gastrulation
  • neuralation
  • somites
22
Q

gastrulation: features/ location

A

3rd wk: differentiates
bilaminar –> trilaminar embryonic disc of 3 germ layers: ectoderm (epiblast), mesoderm (new cells), endoderm (hypoblast)

  • thick structure forms near caudal end (primitive streak)
  • near cranial end: primitive node, primitive groove
  • epiblast cells migrate towards groove -> invaginate and push hypoblast = new endoderm layer
23
Q

neuralation: features

A

notochord: rod-like mesoderm cells

  • notochord induces ectoderm-> form neural plate
  • invagination (end of 3rd wk) = neural grooves and folds
  • fusion of neural folds = neural tube (-> brain and spinal cord)
24
Q

neuralation: neural crest cells

A
  • ‘disobedient’ cells which detach and migrate to help develop
  • head and neck structures
  • brain lining
  • medullar
25
Q

somites: features

A

mesoderm: adjacent to notochord/neural tube forms cube shaped structures

each somite has:

  • myotome
  • dermatome
  • sclerotome
26
Q

myotome somite develops into:

A

skeletal muscles of neck, trunk, limbs

27
Q

dermatome somite develops into:

A

connective tissue, including dermis of skin

28
Q

sclerotome somite develops into:

A

vertebrae and ribs

29
Q

development of cardiovascular system:

A

early development of this is necessary

  • heart tube (splanchnic (viscera) mesoderm = cell differentiation and angiogenesis (new blood vessels))
  • heart beat detected by end of 3rd wk
  • circulate nutrients/ oxygen around embryo
30
Q

list fourth week of development:

A
  • organogenesis
  • embryonic folding
  • pharyngeal arches
31
Q

organgenesis: features

A
  • embryo 3x size
  • major external/internal structures established, main body systems developing
  • minimal function though, except CVS
32
Q

embryonic folding: features

A

head fold:
- brings adult position of heart and mouth

tail fold:
- adult position of anus

lateral folds:
- bend/incorporate yolk sac into embryo as primitive gut, primordia (earliest organ stage) of GIT

33
Q

pharyngeal arches: features

A
  • 5 pairs of pharyngeal arches develop

- gives rise to specialised structures in head and neck -> skeletal component, muscle, nerve and blood vessels

34
Q

define zygote:

A

fertilised ovum

35
Q

define morula:

A

mass of 16-32 blastomeres

36
Q

define blastocyst:

A

appearance of cavity between blastomeres

37
Q

define embryo:

A

human during developmental period (6th day after fertilisation -> end of 8th week)

38
Q

define foetus:

A

human during developmental period (9th week -> end of 40th week)

39
Q

define neonatal period:

A

first 28 days after birth

40
Q

define teratology:

A

study of abnormal development

41
Q

causes of congenital malformations: and eg.

A

defects caused by:

  • genetic factors (chromosome abnormalities- Down Syndrome)
  • environmental factors (pollution, radiation, drugs, viruses)
42
Q

foetal alcohol syndrome:

A

microcephaly (small head), low nasal bridge, short nose, flat mid-face, thin upper lip, micrognathia (undersized jaw)

43
Q

stem cells: features

A

unspecialised cells, able to divide infinitely, gives rise to specialised cells

eg. blastocyst in embryo

44
Q

ectopic pregnancy: features

A

embryo attaches outside uterine cavity (eg. in fallopian tube) causing scarring, vaginal bleeding may lead to complications (death) if not treated

45
Q

NTDs: and eg

A

neural tube defects:

  • incomplete closing of neural tube, result in many defects
  • Spina bifida: spinal cord sticks out of back
  • anencephaly: absence of large portion of brain/ skull
46
Q

placental previa: features

A

placenta attaches inside the uterus but over/ near cervical opening, vaginal bleeding (no pain), foetal growth restriction
- usually Caesarean section