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oral biology > Early embryology > Flashcards

Early embryology Flashcards

1
Q

Zona pellucida:

A

thick basement membrane-like structure immediately surrounding ovum after its release

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2
Q

Results of fertilization

A 
o	2nd meiotic division completed
o	Restores diploid number
o	Variation of species
o	Sex determination
o	Initiation of cleavage
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3
Q

Cleavage

A

1st stage of rapid cell division after fertilization

- Results in compaction since cells divide and do not grow, but become progressively smaller

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4
Q

Trophoblast

A

involved in implantation, it is the ring around the blastocyst; becomes the fetal part of the placenta

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5
Q

Embryoblast

A

-part of blastocyst that will become the amnion, embryo and yolk sack

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6
Q

Hypoblast-

A

endodermal layer of the embryoblast

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7
Q

Epiblast-

A

ectodermal layer of embryoblast

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8
Q

Cytotrophoblast-

A

outermost ring of that differentiates from the trophoblast of the embryoblast after initial implantation

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9
Q

Syncytiotrophoblast

A
  • differentiates from the trophoblast and invades endometrium and uterus
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10
Q

Implantation-

A

occurs approximately 6-8 days after ovulation; superior, posterior wall of uterus is ideal location

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11
Q

Placenta/plakuos

A
  • Multifunctional, temporary organ
  • Nutrient, gas exchange
  • Protection
  • Hormones (endocrine)
  • Umbilical cord attaches embryo/fetus to placenta
  • Complete separation of fetal and maternal blood
  • Highly vascular structure with maternal blood bathing the fetal villi
  • Development progesses until approx. the 7th month
  • Full term – consists of chorionic villi from embryo and decidua basalis from mother
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12
Q

Decidua

A

– the uterine lining during pregnancy formed due to progesterone

  • decidual change in the endometrium
  • forms highly characteristic cells
  • Becomes the maternal part of the placenta
  • This plus the trophoblast becomes the placenta
  • Has 3 parts: basalis, capsularis, and parietalis
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13
Q

Decidua basalis

A
  • majority of placenta

- At base of placenta/trophoblast

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14
Q

Decidua Capsularis

A
  • capsule around embryo: will eventually disappear
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15
Q

Decidua Parietalis

A

-forms the rest of the uterus

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16
Q

Bilaminar disc-

A

14 day embryo before gastrulation; consists of endoderm and ectoderm and has the primitive streak that starts with the primitive node

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17
Q

Trilaminar disc

A

-after gastrulation, the embryo has 3 layers, the ecto, meso and endoderm
- 3 areas do not form trilaminar membrane:
o Oropharyngeal or buccopharyngeal membrane
o Cloacal membrane
o Notochordal process

18
Q

Primitive streak, node

A
  • node is first indication of primitive streak-invagination of the bilaminar disc; these are cells that congregate on the central dorsal aspect of the embryo ectoderm; ectodermal cells migrate into the primitive streak through the bilaminr disc to form the mesoderm
19
Q

Neural plate-

A
  • Formation (neurulation) induced by notochord that forms during gastrulation
  • formed from neuroectoderm
    o thickening of ectoderm over notochord=neural plate
  • folds over to form neural tube that becomes sealed neural tube
    o begins closing during 3rd week
    o complete closing of cranial neuropore on day 26 and caudal neuropore on day 28
  • forms brain and spinal cord and PNS (formed from ECTODERM)
20
Q

Neural crest-

A
  • group of cells that separate from the neural plate
  • form much of head and neck musculature and bones by migrating to the arches
  • also forms peripheral neural ganglia, melanocytes in skin and part of the adrenal gland
  • smooth muscle cells, osteoblasts/clasts, adipocytes, chondrocytes, schwann cells and neurons
21
Q

Notochord

A
  • Forms during gastrulation
  • Adds rigidity to embryo
  • Induces formation of the nueral tube
  • Disappears except for remnants in the nucleus pulposus of intervertebral discs
22
Q

Folding (lateral and cranio-caudal)

A
  • Lateral
    o Folding of nueral plate to form neural tube
    o Amniotic cavity folds around embryo and yolk sack forming gut
  • Cranio-caudal
    o Cranial and caudal portions of embryo fold inward forming a C shaped embryo
23
Q

Anterior neuropore-

A

at the caudal region of the neural tube- closes on day 26

24
Q

Posterior neuropore

A
  • posterior of the neural tube- closes on day 28
25
Q

Holoprosencephaly-

A

caused by halted formation of anterior neuropore

26
Q

Stomodeum-

A

future oral cavity/primitive mouth- location of buccopharyngeal membrane

27
Q

Buccopharyngeal membrane-

A

at the stomodeum- only 2 layers, no mesoderm-ruptures to form oral cavity

28
Q

Cloacal membrane-

A

membrane at the caudal portion of gut- only 2 layers, no mesoderm- ruptures to form anus

29
Q

Dichorionic/diamniotic

A

Cleavage of morula at days 1-2

30
Q

Monochorionic/diamniotic

A

Cleavage of blastocyst at days 4-8

31
Q

Monochorionic/monoamniotic

A

Cleavage of implanted blastocysts at days 8-12

-Creates mirror image twins

32
Q

Conjoined twins

A

Cleaved after formation of embryonic disc from days 12-15

-Names after area attached (pagos-fixed)

33
Q

Down syndrome-trisomy 21

A
  • Slanted palpebral fissures, epicanthal folds, flat nasal bridge
  • Protruding tongue
  • Mental deficiency
  • CHD
  • Simian crease
  • macroglossia
  • slanted palpebral fissures,
  • epicanthal folds,
  • flat nasal bridge,
  • Protruding tongue ,
  • Most common chromosomal abnormality in children
  • 1-2/1000 live births
  • 80% of cases due to maternal non-disjunction and Robertsonian Translocation
  • Risk of non-disjunction increases with maternal age
34
Q

Edward syndrome-trisomy 18

A
  • Micrognathia
  • Clenched fists
  • Rocker bottom feet
  • Short sternum
  • Narrow pelvis
  • VSD
  • Mental deficiency
  • Growth retardation
  • 1/7000 live births
  • Death by 2 weeks of age
  • Robertsonian Translocation
35
Q

-Patau syndrome – trisomy 13

A
  • Mental deficiency
  • Growth retardation
  • Bilateral cleft lip/palate
  • Malformed ears
  • CNS malformations
  • Omphalocele – intestines coming out of abdomen
    -1/29,000 live births
    -Death typically before 1 yr of age
    -Robertsonian Translocation
    and nondisjunction
    -Bilateral cleft lip/palate
  • Malformed ears
  • CNS malformations
  • Omphalocele
36
Q

Ectoderm

A 
-	Gives rise to:
o	Epidermis and its derived structures: hair, nails & sweat glands
o	Nervous tissue – brain and SC
o	Lining of mouth
o	Tooth structures
37
Q

Endoderm

A
  • Gives rise to:
    o Lining of pharynx
    o Respiratory tract
    o GI tract
38
Q

Mesoderm

A 
-	Gives rise to:
o	Most of muscles
o	Bones
o	Connective tissues
o	Blood vessels
o	Heart
o	blood
39
Q

Teratogen- factors

A
  • Heredity – abnormal genes (e.g. trisomies)
  • Chemicals and drugs (e.g. thalidomide)
  • Alcohol
  • Abnormally high hormone levels
  • Vitamins (A)
  • Irradiation (e.g. X-Rays, fallout etc.)
40
Q

Thalidomide

A
  • claimed to cure “anxiety, insomnia, gastritis, and tension”.[3] Afterwards it was used against nausea and to alleviate morning sickness in pregnant women.
  • Caused limb deformities

oral biology (4 decks)

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