3. Embryogenesis

Question 1

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

Answer 1

Ampulla; fertilization

Question 2

What forms when first sperm reaches secondary oocyte?

Answer 2

Tubelike structure called acrosomal apparatus and it penetrates cell membrane

Question 3

What rxn happens after sperm penetrates cell membrane?

Answer 3

Cortical rxn: release of Ca ions

Question 4

Why does cortical rxn occur?

Answer 4

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

Question 5

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

Answer 5

The now depolarized and impenetrable membrane

Question 6

How are dizygotic (fraternal) twins formed?

Answer 6

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

Question 7

How are monozygotic (identical) twins formed?

Answer 7

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

Question 8

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

Answer 8

mono = shared, di = their own

Question 9

What is cleavage?

Answer 9

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

Question 10

What happens to size of cells as cleavage continues?

Answer 10

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

Question 11

What are 2 types of cleavage?

Answer 11

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

Question 12

What is a morula?

Answer 12

When the embryo is a solid mass ball of cells

Question 13

What is blastulation?

Answer 13

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

Question 14

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

Answer 14

Blastocyst; trophoblast cells and inner cell mass

Question 15

What are trophoblast cells and inner cell mass?

Answer 15

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

Question 16

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

Answer 16

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

Question 17

What does umbilical cord consist of?

Answer 17

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

Question 18

What is the yolk sac?

Answer 18

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

Question 19

What are allantois and amnion?

Answer 19

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

Question 20

What is gastrulation?

Answer 20

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

Question 21

What are archenteron and blastospore?

Answer 21

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

Question 22

What are the primary germ layers?

Answer 22

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

Question 23

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

Answer 23

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

Question 24

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

Answer 24

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

Question 25

What are teratogens?

Answer 25

Substances that interfere with embryo development

Question 26

Specification vs determination vs differentiation vs induction

Answer 26

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

Question 27

What are stem cells? What is potency?

Answer 27

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

Question 28

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

Answer 28

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

Question 29

How is determination and differentiation determined?

Answer 29

Morphogens, location of cells

Question 30

What is regenerative capacity? Complete vs incomplete regeneration?

Answer 30

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

Question 31

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

Answer 31

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)

Question 32

What happens in first trimester?

Answer 32

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

Question 33

What happens in second trimester?

Answer 33

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

Question 34

What happens in third trimester?

Answer 34

Continued brain development, ab passed on

Question 35

What happens in birth?

Answer 35

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

Question 36

Order of developing an embryo

Answer 36

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

Question 37

What is hCG?

Answer 37

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

Question 38

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

Answer 38

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