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MCAT - biology > early developmental stages > Flashcards

early developmental stages Flashcards

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1
Q

where does fertilization occur?

A

ampulla - the widest part of the fallopian tube

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2
Q

why does the sperm release acrosomal enzymes when it binds to the secondary oocyte?

A

to penetrate the corona radiata and the zona pellucinda

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3
Q

the first sperm to come into direct contact with the secondary oocyte’s cell membrane forms a tube like structure known as the ____________

A

acrosomal apparatus

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4
Q

after penetration of the serm through the oocytes membrane, __________ is released

A

calcium ions

*this is known as the cortical reaction

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5
Q

calcium ions ____________ the membrane of the ovum

A

depolarize

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6
Q

what is the purpose of calcium ions depolarizing the ovums membrane?

A
  1. prevents fertilization by multiple sperm cells
  2. increases the metabolic rate of the newly formed diploid zygote
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7
Q

the newly depolarized and impenetrable membrane of the ovum is now called the _______________

A

fertilization membrane

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8
Q

two ways twins can form

A
  1. dizygotic (fraternal) twins
  2. monozygotic (identical) twins
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9
Q

_____________ twins form from fertilization of two different eggs released during one ovulatory cycle by two different sperm

A

dizygotic (fraternal) twins

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10
Q

T / F - dizygotic twins each develop their own placenta, chorion, and amnion

A

true

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11
Q

___________ twins form when a single zygote splits

A

monozygotic (identical) twins

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12
Q

what happens if the division of the zygote is incomplete in monozygotic twins?

A

conjoined twins

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13
Q

___________ twins share the same amnion and chorion

A

monochorionic / monoamniotic

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14
Q

__________ twins each have their own amnion, but share the same chorion

A

monochorionic / diamniotic

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15
Q

___________ twins each have their own amnions and chorions

A

dichorionic / diamniotic

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16
Q

after fertilization in the fallopian tubes, the zygote must travel to the uterus for __________

A

implantation

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17
Q

as it moves to the uterus for implantation, the zygote undergoes ___________

A

cleavage

*rapid mitotic cell divisions

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18
Q

the first cleavage a zygote goes through creates the ____________

A

embryo

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19
Q

T / F - the first cleavage creates a unicellular embryo

A

true

*unicellularity is one of the embryo’s defining features

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20
Q

T / F - as the embryo continues to go through mitosis, the total size decreases in the first few divisions

A

false

*the total size remains unchanged for the firsy few divisions

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21
Q

by dividing into progressively smaller cells, what does the embryo achieve?

A
  1. increases the nuclear to cytoplasmic ratio
  2. increases the surface area to volume ratio

*the cell achieves increased area for gas and nutrients exchange relative to overall volume

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22
Q

what are the two types of cleavage?

A
  1. indeterminate
  2. determinate
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23
Q

___________ cleavage results in cells that can still develop into complete organisms

A

indeterminate

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24
Q

____________ cleavage results in cells that are committed to differentiating into a certain type of cell

A

determinate

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25
Q

embryo –> ___________ –> __________

A

embryo –> morula –> blastula

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26
Q

_____________ is the fluid filled inner cavity of the blastula

A

blastocoel

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27
Q

_____________ is another name for the mammalian blastula

A

blastocyst

28
Q

what two cell groups make up the blastocyst?

A
  1. trophoblast
  2. inner cell mass
29
Q

what does the trophoblast become?

A

chorion and placenta

30
Q

what does the inner cell mass become?

A

the organism

31
Q

the blastula moves trough the fallopian tubes to the uterus where it burrows into the _____________

A

endometrium

32
Q

______________ is produced by trophoblastic cells and eventually gives rise to the placenta

A

chorion

33
Q

what is the purpose of chorionic villi?

A

microscopic finger like projections that penetrate the endometrium that support maternal - fetal gas exchange

34
Q

the umbilical cord consists of _____ veins and _________ arteries

A

2 arteries
1 vein

34
Q

the embryo is connected to the placenta by the ___________

A

umbilical cord

35
Q

explain the differences in the blood carried by the umbilical cord vein and arteries

A

vein = carries freshly oxygenated blood from the placenta to the embryo

arteries = carry deoxygenated blood and waste away from the embryo to the placenta to be exchnaged

36
Q

until the placenta is fully functional, the embryo is supported by the ________

A

yolk sac

37
Q

the yolk sac is also a site of early ___________ development

A

blood cell

38
Q

_____________ is an embryonic membrane that i involved in early fluid exchnage between the embryo and yolk sac

A

allantonis

39
Q

_________ is a thin, tough embryonic membrane that surrounds the allantonis and is filled with amniotic fluid

A

amnion

40
Q

what is the purpose of the amnion membrane?

A

to act as a shock absorber during maternal motion

41
Q

___________ is the generation of three distinct cell layers

A

gastrulation

42
Q

gastrulation begins with a small invagination in the blastula, that creates a tube through the middle, this new structure is called a __________

A

gastrula

43
Q

the membrane invagination into the blastocoel is called the ___________

A

archenteron

44
Q

the archenteron later develops into the ___________

A

gut

45
Q

the opening of the archenteron is called the ______________

A

blastopore

46
Q

in deuterostomes (humans), the blastopore develops into the ________

A

anus

47
Q

in protostomes (humans), the blastopore develops into the ________

A

mouth

48
Q

what are the primary germ layers and where are they located?

A
  1. ectoderm (outermost)
  2. mesoderm (middle)
  3. endoderm (innermost)
49
Q

what does the ectoderm give rise to?

A

“attractoderm” - things that attract use to others (cosmetic features, smarts)

epidermis
hair
nails
epithelia of nose, mouth, lower anal canal
lens of eye
nervous system
inner ear

50
Q

what does the mesoderm give rise to?

A

“meansoderm” - means of getting around (bones, muscle, circulatory system, gonads)

musculoskeletal system
circulatory system
excretory system
gonads
muscular tissue
connective tissue
adrenal cortex
notochord

51
Q

what does the endoderm give rise to?

A

“endernal organs” - linings of internal organs (digestive, respiratory)

52
Q

_____________ is when only the genes needs for that particular cell type are transcribed

A

selective transcription

53
Q

____________ is the ability of one group of cells to influence the fate of nearby cells

A

induction

54
Q

how is induction mediated?

A

inducers

*diffuse from the organizing cells to the responsive cells

55
Q

____________ is the development of the nervous system

A

neurulation

56
Q

a rod of mesodermal cells known as the _______ forms along the long axis of the organism like a primitive spine

A

notochord

57
Q

the notochord induces a group of overlying ectodermal cells to slide inward to form the ___________

A

neural folds

58
Q

the neural folds surround a ___________

A

neural groove

59
Q

the neural folds grow toward one another until they fuse into a ________

A

neural tube

60
Q

at the tip of each neural fold are _____________ that migrate outward to form the PNS

A

neural crest cells

61
Q

what tissues do neural crest cells develop into?

A

sensory ganglia
autonomic ganglia
adrenal medulla
schwann cells

62
Q

___________ are substances thet interfere with development, casuing defects or even death of the developing embryo

A

teratogens

63
Q

examples of teratogens?

A

alcohol
prescription drugs
viruses
bacteria
environmental chemicals

64
Q

how does hyperglycemia in a mother effect the embryo’s development?

A

overexposure to sugar can result in a fetus too large to be delivered

65
Q

how does maternal folic deficiency affect the embryonic development?

A

may prevent complete closer of the neural tube, resulting in spina bifida

66
Q
A

MCAT - biology (35 decks)

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