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MCAT Bio > 3. Embryogenesis > Flashcards

3. Embryogenesis Flashcards

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1
Q

What is the widest part of the fallopian tube called? What process happens here?

A

Ampulla; fertilization

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2
Q

What forms when first sperm reaches secondary oocyte?

A

Tubelike structure called acrosomal apparatus and it penetrates cell membrane

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3
Q

What rxn happens after sperm penetrates cell membrane?

A

Cortical rxn: release of Ca ions

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4
Q

Why does cortical rxn occur?

A

Depolarize ovum membrane to prevent other sperm from fertilizing and the increase of Ca conc increases metabolic rate of the newly formed diploid zygote

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5
Q

What is the fertilization membrane (as opposed to a cell membrane)?

A

The now depolarized and impenetrable membrane

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6
Q

How are dizygotic (fraternal) twins formed?

A

2 different eggs released in 1 ovulation fertilized by 2 different sperm; each zygote has their own structure

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7
Q

How are monozygotic (identical) twins formed?

A

1 zygote splits into 2 zygotes; if division is incomplete –> conjoined twins

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8
Q

Monochorionic/monoamniotic twins vs Monochorionic/diamniotic twins vs Dichorionic/diamniotic twins

A

mono = shared, di = their own

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9
Q

What is cleavage?

A

Rapid mitotic cell division for zygote as it moves to uterus for implantation; first cleavage creates embryo

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10
Q

What happens to size of cells as cleavage continues?

A

Cells = smaller –> inc SA:V ratio and N:C ratio

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11
Q

What are 2 types of cleavage?

A

Indeterminate: results in cells that can develop into complete organisms or any cell type; determinate: results in cells differentiated into specific types of cells

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12
Q

What is a morula?

A

When the embryo is a solid mass ball of cells

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13
Q

What is blastulation?

A

Morula forms to blastula, a hollow ball of cells containing fluid-filled inner cavity => blastocoel

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14
Q

What is a mammalian blastula called and what does it consist of?

A

Blastocyst; trophoblast cells and inner cell mass

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15
Q

What are trophoblast cells and inner cell mass?

A

trophoblast cells surround blastocoel and give rise to chorion and later placenta; inner cell mass protrude into blastocoel and give rise to organism itself

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16
Q

What is a chorion? How do trophoblast cells produce chorion specifically?

A

extraembryonic membrane that develops into a placenta. They form chorionic villi, fingerlike projections that penetrate endometrium and develop into placenta for maternal-fetal gas exchange

17
Q

What does umbilical cord consist of?

A

2 arteries and 1 vein encased in gelatinous substance; vein carries fresh oxygenated blood + nutrients from placenta to embryo, arteries carry deoxygenated blood and waste from embryo to placenta

18
Q

What is the yolk sac?

A

Before the placenta works, yolk sac supports embryo; it’s also the site of early blood cell development. Remnants of yolk sac and allantois make up umbilical cord

19
Q

What are allantois and amnion?

A

Allantois allows fluid exchange b/w yolk sac and embryo; amnion is a thin, tough membrane that surrounds allantois as shock absorber to lessen impact from maternal motion on developing embryo

20
Q

What is gastrulation?

A

Generation of 3 distinct germ layers after implantation; membrane invagination into blastocoel => gastrula

21
Q

What are archenteron and blastospore?

A

Membrane invagination that becomes anus in deuterstomes or mouth in protostomes; opening of archenteron

22
Q

What are the primary germ layers?

A

Ectoderm: give rise to integument (hair, nails, nose, mouth, ears, eye), nervous system; mesoderm: give rise to musculoskeletal, circulatory, and excretory systems, gonads, connective tissue; endoderm: give rise to epithelial linings, digestive and respiratory system

23
Q

How do cells with same genes know what type they’ll become?

A

Selective transcpxn/induction; inducers diffuse from organizing cells to responsive cells (responsive cells have to be competent - respond to signal)

24
Q

When does neurulation occur? What is it? How does it occur?

A

After gastrulation; development of nervous system; rod of mesodermal cells make notochord (later developed into hollow dorsal nerve cord aka spinal cord) along long axis of organism –> overlying ectodermal cells slide inward to make neural folds which surround a neural groove –> neural folds grow toward each other until they fuse into a neural tube –> CNS, neural crest cells at tip of neural tube migrate away from origin sites —> give rise to PNS. Neural tube has alar plate that differentiates to sensory neurons and basal plate that differentiates to motor neurons

25
Q

What are teratogens?

A

Substances that interfere with embryo development

26
Q

Specification vs determination vs differentiation vs induction

A

Cell is designated to specific cell type (reversible) vs commitment of cell to a specific cell type (irreversible) vs produce the needs for cell to become specific cell type vs cells inducing adjacent cells to commit to a certain cell type

27
Q

What are stem cells? What is potency?

A

Cells that didn’t differentiate yet or give rise to other cells that’ll differentiate; determines which cell type to differentiate to

28
Q

Totipotent cells vs pluripotent cells vs multipotent cells. Adult stem cells vs embryonic stem cells in terms of potency

A

Can differentiate into any cell type or whole organism vs can differentiate into any cell type except those in placental structures vs can differentiate into any cell type within a certain group. Multi potent vs pluripotent

29
Q

How is determination and differentiation determined?

A

Morphogens, location of cells

30
Q

What is regenerative capacity? Complete vs incomplete regeneration?

A

Ability of organism to regrow certain parts of body. Regenerate with identical tissues (like liver) vs regenerate with nonidentical tissues (like MI); humans do this

31
Q

How do shunts move blood (explain foramen ovale, ductus arteriosus and ductus venosus)?

A

Foramen ovale = 1 way valve that connects right atrium to left atrium –> allows blood to flow from IVC to right atrium to left atrium instead of right ventricle –> pumps blood through aorta into systemic circulation directly (bypass lungs); ductus arteriosus shunts leftover blood from pulmonary artery to aorta and into systemic circulation (bypass lungs); ductus venosus shunts blood from placenta to IVC (bypass liver)

32
Q

What happens in first trimester?

A

Most organs are formed, brain is fairly developed, embryo becomes fetus; corpus luteum degenerates after first trimester, placenta has formed and releases estrogen and progesterone to maintain pregnancy

33
Q

What happens in second trimester?

A

Fetus moves w/in amniotic fluid, facial features, definition of fingers and toes

34
Q

What happens in third trimester?

A

Continued brain development, ab passed on

35
Q

What happens in birth?

A

Prostaglandins and oxytocin coordinate contractions from cervix stretching out or dec lvls of estrogen from placenta breaking down. Cervix thins out and amniotic sac ruptures (water breaks), increased uterine stretch –> inc uterine contractions, placenta and umbilical cord = expelled (afterbirth). Progesterone later inhibits contractions

36
Q

Order of developing an embryo

A

Fertilization —> simultaneous cleavage and moving to endometrium —> morula + simultaneous cleavage and moving to endometrium —> blastula + implantation in endometrium —> gastrulation –> neurulation

37
Q

What is hCG?

A

hormone produced by trophoblast cells; its lvls = high in early pregnancy to maintain corpus luteum –> after 1st trimester, placenta = developed and hCG drops –> corpus luteum deteriorates, placenta maintains progesterone (and estrogen) to maintain pregnancy

38
Q

Which gamete = responsible for providing all organelles after a zygote is formed?

A

ovum; so any d/o of organelles = from mother

MCAT Bio (20 decks)

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