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Anatomy Exam 1 > Embryology/Limb dev > Flashcards

Embryology/Limb dev Flashcards

1
Q

what are the 2 important sites of the sperm?

A

acrosome, w enzymes for the acrosomal reaction

tail, movement

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2
Q

what happens to the chromosome number during gametogenesis?

A

the chromosome number is reduced by 1/2, and the shape of the cells is altered (each cell contains haploid number)

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3
Q

definition of fertilization

A

fusion of pronucleus of the sperm with the pronucleus of the ovum to form the zygote

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4
Q

where does fertilization occur?

A

the ampulla of the uterine tube

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5
Q

what are the four phases of fertilization?

A

1) capacitation and acrosomal reaction
2) penetration
3) zona reaction

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6
Q

what happens during the acrosomal reaction?

A

the sperm penetrates the corona radiata, and upon binding to the zona pellucida, enzymes in the acrosome of the sperm degrade the layer after a rise in Ca

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7
Q

what happens after the acrosomal reaction occurs? what is the exception?

A

the oocyte will block other sperm from entering (blocking of polyspermy), except for in the case of twins
- this occurs via the cortical reaction, which causes the zona pellucida to harden

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8
Q

what are the results of fertilization?

A

1) restoration of normal diploid number of chromosomes

2) chromosomal sex determination of embryo

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9
Q

what occurs during the cleavage stage?

A

after fertilization occurs (zygote), lots of CD occurs giving lots of blastomeres –> morula
- early blastocyst forms when the morula hollows out, fills w fluid, and zona pellucida degenerates

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10
Q

what is the initiating factor for implantation during cleavage?

A

the degradation of the zona pellucida (that was still present at the morula)

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11
Q

what happens as the early blastocyst starts to form?

A

cells start to rearrange, going to one side: site of the inner cell mass, which will be the future embryo

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12
Q

what defines an implanting blastocyst?

A

it consists of a spherical lining of cells (trophoblast) around the inner cell mass that give fingerlike projections to help the embryo/inner cell mass to be implanted

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13
Q

what are the 2 layers of the trophoblast?

A

1) cyto - well-defined cell boundary. appears early, disappears w time
2) synchtio - ill-defined, continuous, secretes HCG

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14
Q

what happens if the zona pellucida disappears ebfore early blastocyst formation?

A

the zygote will implant in the fallopian tubes - ectopic pregnancy

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15
Q

what is the site of implantation?

A

in the posterior superior wall of the uterus

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16
Q

where is the most common site of an ectopic pregnancy?

A

sometimes in the ovary, but tubal most common

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17
Q

what are the symptoms of an ectopic pregnancy?

A

uterine bleeding, sudden onset of abdominal pain (appendicitis), missed period, positive HCG test

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18
Q

HCG

A

a glycoprotein produced by synctio, can be assayed in maternal blood and urine

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19
Q

what may low HCG levels indicate?

A

spontaneous abortion, ectopic

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20
Q

what may high HCG levels indicate?

A

multiple pregnancy, trophoblastic diseases

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21
Q

what is meant by “period of 2” in the 2nd week of dev?

A

embryoblast –> epi and hypoblast (bilaminar disc)
trophoblast –> cyto and synctio
2 cavities –> amniotic cavity and yolk sac

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22
Q

what happens during the invasion of the blastocyst?

A

fix the position of the blastocyst in the uterus at this stage, using chorionic villi to position the embryo

23
Q

what is the role of the trophoblast when the embryo needs to be implanted?

A

trophoblast will extend fingerlike projections, chorionic villi, to the endometrium

24
Q

compare the number of types of chorionic villi at the 3rd week and then at the beginning of the 4th week

A

3rd week: 3 types of chorionic villi (cyto, synctio, endothelium)
4th week: only have 2 layers left (no cyto anymore)

25
Q

decidua basalis

A

part of the embryo that attaches to the uterus, the maternal part of the placenta

26
Q

during EARLY pregnancy, how many layers are in the placental barrier, and what are they?

A

4:
1) synctio
2) ctyo
3) connective tissue
4) fetal endothelium

27
Q

during LATE pregnancy, how many layers are present in the placental barrier, and why are these layers needed?

A

2
1) synctio: secrete HCG, continuation of placenta
2) fetal endothelium: for exchange of O2
(these are the only 2 that are continuous)

28
Q

what are the maternal and fetal components of the placenta?

A

maternal: decidua basalis
fetal: chorionic villi

29
Q

what is the function of the placenta?

A
  • gas exchange (O2 and CO2)
  • nutrients: glucose, fatty acids, AAs, electrolytes
  • hormonal and immunologic exchange
30
Q

where is everything exchanged btw fetus and mother?

A

arteries from the endometrium come into the INTERVILLOUS SPACE around villi, which is where all exchange occurs

31
Q

why is week 3 of dev known as the period of 3?

A
  • primitive streak and notochord formation
  • gastrulation of epiblast (trilaminar germ disc): exto, endo, mesoderm
  • neurulation: neural plate, groove, tube
  • mesoderm differentation: 3 types of mesoderm
32
Q

what happens during gastrulation?

A

epiblast gets rid of the hypoblast, which becomes the endoderm.
- epiblast will change to ectoderm. layer btw the 2 is mesoderm
- all 3 layers come out of the epiblast as it “updates” the embryo via the neural groove
“epiblast gives renovation”

33
Q

why is the mesoderm important during gastrulation?

A

starts to specify the embryo’s shape (cranial and caudal ends)
- starts to form a midline of the embryo, primitive streak where the mesoderm originates and spreads btw ecto and endo

34
Q

formation of notochord

A

some of the mesoderm will form the notochord, will become the intervertebral discs

35
Q

what are the 3 layers of the mesoderm?

A

somite
intermediate
lateral plate

36
Q

neural tube formation

A

the neural groove folds around the thick ectoderm, will fuse together to form the neural tube (future SC and brain)

37
Q

steps of neurulation

A 
neural plate
neural groove
neural crest
neural folds
neural tube
38
Q

what are the results of folding following gastrulation?

A

endoderm becomes enclosed inside the embryo, forming the gut tube
ectoderm covers the embryo from outside, and amniotic sac to expand to surround the embryo
- the oral mem and cloacal mem become ventral
- pericardium and septum transversum (future diaphragm) become ventral

39
Q

the ectoderm germ layer will give rise to …

A
  • epidermis, hair, nails, glands of skin
  • brain, SC
  • neural crest/derivatives (cranial, spinal, sympathetic ganglia, associated nerves, adrenal medulla, pigment cells of skin)
40
Q

the endoderm germ layer will give rise to …

A

epithelial lining and glands of digestive and resp tracts

41
Q

mesoderm germ layer will give rise to …

A
  • notochord (intervertebral discs)
  • somite (sclerotome - vertebrae and ribs, dermatome - dermis of dorsal body region, myotome - trunk and limb musculature)
  • intermediate (kidneys, gonads)
  • lateral plate (somatic and sphlanchic, connective tissues of limbs (bones, joints, ligaments), wall of digestive and respiratory tracts (except epithelial lining), heart, blood vessels
42
Q

describe the general stages of limb development

A
  • 4 limb buds develop from ventrolateral body wall
  • circular groove appears separating a hand plate from upper limb, foot plate from lower
  • digital rays –> notches –> webbed fingers –> separated digits
  • a second groove appears
43
Q

limb rotation (degrees)

A

upper limb - 90 degrees laterally

lower limb - 90 degrees medially

44
Q

flexors/extensors are posterior/anterior? in the upper vs lower limb

A

upper: flexors (anterior) extensors (posterior)

opposite for lower limb

45
Q

what are the medial and lateral bones of the upper and lower limbs?

A

upper:
radius (lateral) ulna (medial)
fibia (lateral) tibia (medial)

46
Q

what are the bones of the upper/lower limb used for rotation, which direction do they point

A

upper: thumb (lateral) elbow (backwards)
lower: big toe (medial) knee joint (forwards)

47
Q

amelia

A

absence of entire limb

48
Q

meromelia

A

absence of part of limb

49
Q

polydactyly

A

extra digit

50
Q

syndactyly

A

fusion of digits

51
Q

during the later stages of pregnancy, maternal blood is separated from fetal blood by the …

A

synctio and fetal epithelium (placental barrier)

52
Q

what must degenerate for blastocyst implantation to occur?

A

zona pellucida

53
Q

US of 20 y/o pregnant woman in the 20th week of pregnancy revealed abnormal limb dev of her fetus, showing one arm to be shorter than the other. what condition is likely described?

A

meromelia

Anatomy Exam 1 (8 decks)

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