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mcat biology > Embryogenesis and Development > Flashcards

Embryogenesis and Development Flashcards

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1
Q

Fertilization

A
  • Occurs in widest portion of Fallopian tube (ampulla)
    • Penetrate corona radiata ( Hyaluronidase)
    • Penetrate zona pellucida ( acrisie) (zona lysin)
    • Release of cortical granules into perivitelline space.
    • Release of calcium; depolarization (fast block to polyspermy) and increased metabolic rate of zygote.
    • Fertilization membrane (FM): result from fusion of vitelline membrane with cortical granules
      - Process of slow block to polyspermy
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2
Q

Twins

A

Dizygotic

monozygotic

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3
Q

Monozygotic

A
  • Inner cell mass of a zygote splits into two.

- Conjoined twins may occur

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4
Q

Cleavage

A
  • Begins during travel to uterus after fertilization
    • Overall size remains the same
    • Types:
      • Indeterminate: results in cells that can still develop into complete organism
      • Determinate: results in cells with fates that are determined. Committed to differentiation
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5
Q

Blastulation

A

morula undergoes blastulation to form blastula (blastocyst in mammals)

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6
Q

Blastocoel

A

fluid filled cavity

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7
Q

Trophoblast

A
  • surround blastocoel

- give rise to chorion which becomes placenta

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8
Q

Inner cell mass

A
  • Gives rise to organism and three germ layers.
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9
Q

Chorion

A
  • Develop into placenta

- protective membrane around amnion

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10
Q

Chorionic villi

A
  • penetrate the endometrium

- support meternal-fetal gas exchange

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11
Q
  • Umbilical cord
A
  • Formed from remnants of yolk sac and allantois
    - Vein carries oxygenated blood to embryo
    - Arteries deoxygenated blood and waste to placenta
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12
Q
  • Yolk sac
A
  • supports embryo before placenta does

- Site of blood cell development

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13
Q
  • Allantois
A
  • Fluid exchange b/w embryo and yolk sac

- removal of embryonic waste

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14
Q
  • Amnion
A
  • surrounding membrane filled with fluid
    - Shock absorber
    - Buffer against mechanical injury
    - Accommodates growth
    - Allows normal movements
    - Protects fetus from adhesions
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15
Q
  • Gastrulation
A
  • the generation of three distinct cell layers.
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16
Q
  • Gastrulation steps
A
  • nvagination of blastula membrane; eliminating blastocoel
    - archenteron (future gut) forms
    - blastopore opening (future anus in deutoerostomes or future mouth in protostomes) forms
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17
Q
  • Primary germ layers
A
  • established by cell migration into blastocoel
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18
Q

germ layers types

A
  • Ectoderm
    - Mesoderm
    - Endoderm
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19
Q

Ectoderm

A
  • outermost layer
    - gives rise to integuments (skin, hair, nails), nervous system, adrenal medula ( b/c it contains nervous tissue.)
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20
Q

Mesoderm

A
  • middle layer
    - gives rise to musculoskeletal, circulatory, digestive, respiratory and excretory system, gonads, adrenal cortex, immune system,
    
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21
Q

Endoderm

A
  • innermost layer
    - gives rise to epithelal linings of digestive and respiratory tracts, and accessory organs (liver, pancreas, lungs, bladder) within these systems
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22
Q

Differentiaton

A
  • progressive specialization of structure and function

- A result of selective gene transcription

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23
Q

induction

A

the ability of one group of cells to influence the fate of other nearby cells. An effect one (inductor) has upon another (responder) such that the development course of the responding tissue is qualitatively changed from what it would have been in the absence of the inductor.

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24
Q
  • Neuralation
A
  • development of nervous system from ectoderm
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25
Q
  • Neurolation steps
A
  • notochord (mesoderm cells) forms
    - notochord induces neural fold of ectodermal cells
    - neural fold intersect to form neural tube ( future CNS)
    - Neural crest cells found near neural tube migrate outword ( future PNS)
    - More ectodermal cells migrate over and cover the tube and crest cells.
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26
Q
  • Problems in early development
A
  • highly sensitive time
    • highly variable
    • somewhat unpredictable
    • Teratogens may interfere with development causing defects or death
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27
Q

Teratogens are Influeced by

A
  • genetics
    - exposure time
    - route taken
    - rate of transmission
    - identity
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28
Q

Types of Teratogens

A
  • alcohol
    - drugs
    - bacteria
    - viruses
    - chemicals
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29
Q

folic acid deficiency during pregnancy yields_____

A

child with spina bifida

30
Q
  • cell specialization
A

cells needs specific organization for proper function

    - i.e pancreatic cells for endocrine hormones vs digestive enzymes.
31
Q

Pathway to specialization

A

specification → determination → differentiation

32
Q

specification

A

reversibly designated to a type

33
Q

determination

A

irreverssible commitment of cells

34
Q

pathways to determination

A
  • presence of specific mRNA, protein and extracellular morphogens
35
Q

differentiation

A

assume the structure, function, and biochemistry of a cell

36
Q

stem cells

A
  • undifferentiated
    - give rise to other cells
    - found in embryonic and adult tissues
    - level of potencies (highest to lowest) (Totipotent, pluripotent, multipotent)
37
Q

Totipotent

A
  • form into ANY cell

- Found b/w fertilization and blastulation

38
Q

Pluripotent

A
  • form any cell except placental structures

- Found starting at 3 germ layer differentiation

39
Q

Multipotent

A
  • form any cell within a particular group

- i.e Hematopoietic stem cells ( blood cells only)

40
Q
  • Problems with embryonic stem cell therapy
A
  • genetic difference yielding Immunological rejection

- cancerous

41
Q
  • solution by adult stem cell
A
  • multipotent at best
    - inducable by transciption factors
    - unrejectable
42
Q
  • cell-cell communication via
A
  • autocrine: upon itself
    - paracrine: within local area (i.e neurons)
    - juxtacrine: directly to adjacent cell that is in contact
    - endocrine: hormones diffusing through blood
43
Q
  • inducers (growth hormones)
A
  • function on specific cell types
    - exhibit reciprical development
    - ultimate differentiation of one leads to development of another
    - morphogens are secreted simultaneously → diffuse through the organism → form a gradient → unique exposure to all cells.
44
Q

cell migration

A
  • automatic movement to correct location after differentiation
45
Q
  • cell death
A

Apoptosis or Necrosis

46
Q

apoptosis

A
  • programmed cell death
    - at various times of development
    - via singnals or preprogramming
47
Q

necrosis

A

cell death as a result of injury

48
Q

Steps in apoptosis

A

apoptotic blebs → apoptotic bodies → phagocytized

49
Q
  • Regeneration
A
  • ability to regrow certain parts

- possible due to stem cells

50
Q

Types of regeneration

A
  • complete: identical tissue is formed

- incomplete: unidentical tissue is formed (i.e formation of scar tissue in humans.)

51
Q
  • Senescence and aging
A
  • biological aging

- preventened by Telomerase ( a reverse transcriptase) in germ cells, tumor cells, etc.

52
Q

FETAL CIRCULATION facts

A
  • Gas exchange in the fetus occurs across the placenta
    • fetal lungs do not function until birth
  • Fetal hemoglobin (HbF) has higher affinity for oxygen than the mother
53
Q
  • Placenta
A
  • facilitates diffusion of water, glucose, aminos, and inorganic salts.
    • immune protection against antibodies
    • a type of endocrine organ (progesterone, estrogen, (hCG)
54
Q
  • Fetus vs adult
A
  • fetal lungs and liver: unfunctional and shunted from blood flow.
    • mother’s liver: detoxifies for fetus
55
Q
  • types of shunts
A
  • Foramen ovale
    • ductus arteriosus
    • Ductus venous
56
Q

Foramen ovale

A
  • by passes the lungs

- connects right and left atrium

57
Q

ductus arteriosus

A
  • by passes the lungs

- connects pulmonary artery and aorta

58
Q

Ductus venous

A
  • by passes the liver

- connects umbilical vein and inferior vena cava

59
Q

gestation

A
  • 280 days (3 trimesters)

- larger animals = longer gestation

60
Q
  • First trimester
A
  • 1 week: major organs develop
    • 3 weeks: heart begins to beat
    • 5 weeks: 10mm embryo
    • 8 weeks: its a fetus with most of its organs in place inlcuding a brain
61
Q
  • Second trimester
A
  • growth period
    • appendage elongation
    • movement within amnion
    • distinct facial formation
    • 30 - 36cm long
62
Q
  • Third trimester
A
  • rapid growth
    • brain development continues
    • transfer of antibodies to the fetus
63
Q

During cleavage the total cell volume will stay the same in order to maximize the ____________ for nutrient exchange.

A

surface area

64
Q

Hayflick limit

A

the number of mitotic replications a cell can undergo before it enters a senescent state (before it stops undergoing mitosis altogether).

65
Q

Replicative senescence

A

state that mitotically active cells enter into when they have reached their Hayflick limit (when their telomeres have become very short).

66
Q

Which cells are not capable of entering replicative senescence

A

cardiac muscle

nerve

67
Q

order of formation of germ layers

A

ectoderm then endoderm followed by mesoderm.

68
Q

Gestation

A

begins with the uterus getting ready for implantation

69
Q

When does fertilization normally occur?

A

occurs in week 2 of gestation

70
Q

At which point in development do we start to observe a significant increase of the size of embryo?

A

blastulation

71
Q

Which embryological stage divides the embryo in two halves establishing bilateral symmetry in mammals?

A

formation of the neural tube during neurulation divides the embryo in two symmetric halves.

mcat biology (9 decks)

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