3. Embryogenesis Flashcards
What is the widest part of the fallopian tube called? What process happens here?
Ampulla; fertilization
What forms when first sperm reaches secondary oocyte?
Tubelike structure called acrosomal apparatus and it penetrates cell membrane
What rxn happens after sperm penetrates cell membrane?
Cortical rxn: release of Ca ions
Why does cortical rxn occur?
Depolarize ovum membrane to prevent other sperm from fertilizing and the increase of Ca conc increases metabolic rate of the newly formed diploid zygote
What is the fertilization membrane (as opposed to a cell membrane)?
The now depolarized and impenetrable membrane
How are dizygotic (fraternal) twins formed?
2 different eggs released in 1 ovulation fertilized by 2 different sperm; each zygote has their own structure
How are monozygotic (identical) twins formed?
1 zygote splits into 2 zygotes; if division is incomplete –> conjoined twins
Monochorionic/monoamniotic twins vs Monochorionic/diamniotic twins vs Dichorionic/diamniotic twins
mono = shared, di = their own
What is cleavage?
Rapid mitotic cell division for zygote as it moves to uterus for implantation; first cleavage creates embryo
What happens to size of cells as cleavage continues?
Cells = smaller –> inc SA:V ratio and N:C ratio
What are 2 types of cleavage?
Indeterminate: results in cells that can develop into complete organisms or any cell type; determinate: results in cells differentiated into specific types of cells
What is a morula?
When the embryo is a solid mass ball of cells
What is blastulation?
Morula forms to blastula, a hollow ball of cells containing fluid-filled inner cavity => blastocoel
What is a mammalian blastula called and what does it consist of?
Blastocyst; trophoblast cells and inner cell mass
What are trophoblast cells and inner cell mass?
trophoblast cells surround blastocoel and give rise to chorion and later placenta; inner cell mass protrude into blastocoel and give rise to organism itself
What is a chorion? How do trophoblast cells produce chorion specifically?
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
What does umbilical cord consist of?
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
What is the yolk sac?
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
What are allantois and amnion?
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
What is gastrulation?
Generation of 3 distinct germ layers after implantation; membrane invagination into blastocoel => gastrula
What are archenteron and blastospore?
Membrane invagination that becomes anus in deuterstomes or mouth in protostomes; opening of archenteron
What are the primary germ layers?
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
How do cells with same genes know what type they’ll become?
Selective transcpxn/induction; inducers diffuse from organizing cells to responsive cells (responsive cells have to be competent - respond to signal)
When does neurulation occur? What is it? How does it occur?
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
What are teratogens?
Substances that interfere with embryo development
Specification vs determination vs differentiation vs induction
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
What are stem cells? What is potency?
Cells that didn’t differentiate yet or give rise to other cells that’ll differentiate; determines which cell type to differentiate to
Totipotent cells vs pluripotent cells vs multipotent cells. Adult stem cells vs embryonic stem cells in terms of potency
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
How is determination and differentiation determined?
Morphogens, location of cells
What is regenerative capacity? Complete vs incomplete regeneration?
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
How do shunts move blood (explain foramen ovale, ductus arteriosus and ductus venosus)?
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)
What happens in first trimester?
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
What happens in second trimester?
Fetus moves w/in amniotic fluid, facial features, definition of fingers and toes
What happens in third trimester?
Continued brain development, ab passed on
What happens in birth?
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
Order of developing an embryo
Fertilization —> simultaneous cleavage and moving to endometrium —> morula + simultaneous cleavage and moving to endometrium —> blastula + implantation in endometrium —> gastrulation –> neurulation
What is hCG?
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
Which gamete = responsible for providing all organelles after a zygote is formed?
ovum; so any d/o of organelles = from mother
