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repro 3
| Question | Answer |
|---|---|
| Where does fertilization usually occur? | Ampulla of the fallopian tube |
| What must sperm undergo before fertilizing the egg? | Capacitation |
| What is capacitation? | Final maturation of sperm in female tract. Final maturation of sperm in female reproductive tract that increases ability to fertilize |
| What does capacitation do to sperm? | Increases motility Prepares acrosome for reaction Removes inhibitory proteins |
| What surrounds the egg? | Zona pellucida |
| What is ZP3? | Glycoprotein on zona pellucida that binds sperm and triggers acrosomal reaction |
| Why is ZP3 important? | Ensures species-specific binding Starts fertilization process |
| First step of fertilization? | Acrosomal reaction |
| What is the acrosome? | Cap on sperm head containing digestive enzymes |
| What happens during acrosomal reaction? | Enzymes released Zona pellucida is broken down Sperm moves toward egg membrane |
| What happens after sperm penetrates zona pellucida? | Sperm membrane fuses with oocyte membrane |
| What enters the egg? | Sperm nucleus (genetic material) |
| What immediate change occurs inside the egg after sperm entry? | Increase in intracellular Ca²⁺ |
| Why is Ca²⁺ important? | Activates egg Triggers cortical reaction Starts embryonic development |
| What is cortical reaction? | Release of enzymes from cortical granules that modify zona pellucida |
| What is the purpose of cortical reaction? | Prevents polyspermy (multiple sperm entering) |
| What happens to zona pellucida during cortical reaction? | It hardens and becomes impermeable to other sperm |
| When does the oocyte complete Meiosis II? | After sperm enters |
| What forms after completion of Meiosis II? | Mature ovum nucleus Second polar body |
| What are pronuclei? | Male and female haploid nuclei before fusion |
| How many pronuclei are present? | Two (one from sperm, one from egg) |
| What happens when pronuclei fuse? | Diploid zygote forms (46 chromosomes) |
| What is a zygote? | First cell of a new human organism |
| What is the correct sequence of fertilization? | ZP3 binding → acrosomal reaction → sperm entry → ↑Ca²⁺ → cortical reaction → meiosis II → pronuclei → fusion |
| How long is egg viable? | ~24 hours |
| How long can sperm survive? | 2–5 days |
| Where are sperm deposited? | Vagina |
| How many sperm start the journey? | ~250 million sperm are deposited in the vagina |
| What happens at the cervix? | Most sperm die due to mucus + acidity |
| How many sperm make it into the uterus? | ~100,000 sperm (<1%) |
| What helps sperm move through uterus? | Uterine contractions Sperm motility |
| How many sperm reach the egg? | ~50 or fewer |
| How many sperm actually fertilize the egg? | ONE |
| What is a polar body? | Small cell that contains extra chromosomes |
| Why are polar bodies formed? | To discard extra DNA while keeping cytoplasm in egg |
| When does second polar body form? | After sperm enters (completion of meiosis II) |
| What happens to polar bodies eventually? | They die |
| Where does fertilization occur? | Ampulla of fallopian tube |
| What happens ~39 hours after fertilization? | 2-cell stage |
| What happens ~42 hours? | 4-cell stage |
| What happens ~49 hours? | 8-cell stage |
| What is formed at day 3–4? | Morula |
| What is formed at day 5–6? | Blastocyst |
| When does embryo reach uterus? | Blastocyst stage (day 5–6) |
| What hormone moves egg into tube? | Estrogen |
| What hormone prepares uterus? | Progesterone |
| What nourishes embryo in uterus? | Endometrial glycogen secretions |
| When does the blastocyst reach the uterus? | ~Day 5–6 after fertilization |
| What must the blastocyst do before implantation? | Hatch out of zona pellucida |
| What part of the blastocyst attaches to the uterus? | Trophoblast |
| What is the decidua? | Pregnant uterine lining (endometrium) |
| What do trophoblast cells become during invasion? | A: Syncytiotrophoblast 💡 Story: 👉 “Cells fuse into a powerful digging layer” |
| What does syncytiotrophoblast do? | Releases enzymes Breaks down uterine tissue Allows embryo to burrow in 💡 Story: 👉 “It digs into the uterus” |
| Why does the embryo invade the uterus? | To access nutrients and maternal blood supply |
| When is the embryo fully embedded? | ~Day 12 after fertilization |
| What is the correct order of implantation? | Arrive → Hatch → Attach → Invade → Embed |
| What hormone starts being produced after implantation begins? | hCG WHY:👉 Syncytiotrophoblast produces it |
| What structure becomes the embryo? | Embryonic disc |
| What is the amniotic cavity? | Fluid-filled space that protects embryo |
| What does the yolk sac do? | Early nutrient + circulatory support |
| What surrounds the embryo after implantation? | Maternal blood + trophoblast layers |
| What are germ layers? | 3 layers that form all body tissues |
| Ectoderm becomes? | Skin + nervous system |
| Mesoderm becomes? | Muscle + bone + blood + kidneys |
| Endoderm becomes? | Lungs + digestive organs |
| What is the function of the embryonic disc? | Forms all 3 germ layers → entire body |
| What comes from the inner cell mass? | A: 👉 Embryonic disc 👉 Amnion 👉 Yolk sac 👉 Connecting stalk |
| What becomes the actual baby? | Embryonic disc |
| What is the amnion? | Fluid sac that surrounds and protects embryo |
| What is the connecting stalk? | Structure that connects embryo to placenta |
| What does the connecting stalk become? | Umbilical cord |
| What is the chorion derived from? | Trophoblast |
| What happens to chorion and amnion? | They fuse together |
| What happens to the yolk sac? | It degenerates (goes away) |
| When is it called an embryo? | < 8 weeks post-fertilization |
| When is it called a fetus? | > 8 weeks post-fertilization |
| How do twins form? | 👉 Either 2 eggs (fraternal) 👉 Or 1 egg splits (identical) |
| What are dizygotic (fraternal) twins? | 2 eggs + 2 sperm DC/DA |
| What are monozygotic (identical) twins? | 1 egg that splits into 2 |
| What determines identical twin structure? | Timing of the split |
| What happens if identical twins split early? | DC/DA (fully separate) 💡 Story: 👉 “Split before anything forms → separate everything” |
| What happens if identical twins split later? | MC/DA 1 placenta 2 sacs 💡 Story: 👉 “Same house, different rooms” |
| What happens if twins split very late? | A: 👉 MC/MA 1 placenta 1 sac 💡 Story: 👉 “Everything shared (high risk)” |
| What does DC mean? | Di-chorionic (2 placentas) |
| What does MC mean? | Mono-chorionic (1 placenta) |
| What does DA mean? | Di-amniotic (2 sacs) |
| What does MA mean? | Mono-amniotic (1 sac) |
| If twins share a placenta, what are they? | Identical (monozygotic) |
| What determines twin type? | # of zygotes + timing of split |
| Where does maternal blood go in placenta? | Intervillous space |
| What structure allows exchange? | Chorionic villi |
| Do maternal and fetal blood mix? | No |
| Umbilical arteries carry what? | Deoxygenated blood (baby → placenta) |
| Umbilical vein carries what? | Oxygenated blood (placenta → baby) |
| What is exchanged in placenta? | 👉 O₂, nutrients → baby 👉 CO₂, waste → mom |
| What is the respiratory role of placenta? | O₂ to baby, CO₂ to mom |
| What is the excretory role? | Removes fetal waste |
| What nutrients cross placenta? | Glucose, amino acids |
| What type of organ is placenta hormonally? | Endocrine organ |
| Name 2 protein hormones from placenta | hCG, CRH |
| Name 2 steroid hormones from placenta | Progesterone, estrogen |
| What size molecules can cross placenta? | Small (<500 MW) |
| Can alcohol cross placenta? | Yes |
| Can drugs cross placenta? | Yes |
| Can large protein hormones cross? | No |
| Where is hCG produced? | Syncytiotrophoblast |
| hCG is similar to what hormone? | LH |
| When is hCG detectable? | ~6 days after implantation |
| When does hCG peak? | 9–12 weeks |
| Main function of hCG? | Maintains corpus luteum |
| Why maintain corpus luteum? | To keep progesterone high |
| Why is progesterone important? | Maintains uterine lining |
| What do pregnancy tests detect? | hCG |
| How is hCG used clinically? | Mimics LH to trigger ovulation |
| What is the key hormone pathway that maintains early pregnancy? | hCG → corpus luteum survives → progesterone stays high → uterus maintained |
| What event triggers hCG production? | Implantation of the embryo |
| What produces hCG? | Syncytiotrophoblast |
| What is the MOST IMPORTANT function of hCG? | Prevents corpus luteum degeneration (luteolysis) |
| What structure does hCG act on? | Corpus luteum |
| Why must the corpus luteum be maintained? | It produces progesterone, which is essential for pregnancy |
| What happens if hCG is present? | 👉 Corpus luteum survives 👉 Progesterone remains HIGH 👉 Pregnancy continues |
| What is the MAIN role of progesterone in pregnancy? | Maintains the endometrium (uterine lining) |
| How does progesterone affect the endometrium? | Keeps it thick, vascular, and nutrient-rich |
| What effect does progesterone have on the uterus? | Inhibits uterine contractions |
| How does progesterone protect the embryo physically? | Forms cervical mucus plug → blocks pathogens |
| What happens if hCG is NOT produced? | Corpus luteum degenerates |
| What happens when corpus luteum degenerates? | Progesterone levels drop sharply |
| What does low progesterone do to the uterus? | Endometrium breaks down |
| What is the final result of progesterone drop? | 👉 Menstruation (period) 👉 Pregnancy cannot continue |
| What maintains progesterone before implantation? | Corpus luteum (temporarily) |
| What changes after implantation? | 👉 hCG begins to rise 👉 Takes over support of corpus luteum |
| How are hCG and progesterone related? | 👉 hCG regulates progesterone production |
| Why is menstruation prevented in pregnancy? | 👉 Progesterone remains high |
| Why can hCG be used to detect pregnancy? | 👉 It is produced shortly after implantation |
| What is the most common cause of early pregnancy loss hormonally? | 👉 Failure to maintain progesterone (corpus luteum failure) |
| Why is progesterone supplementation sometimes given? | 👉 To prevent luteal phase defect / early pregnancy loss |
| What is the full cause → effect chain for maintaining pregnancy? | A: 👉 Implantation → hCG released → corpus luteum maintained → progesterone stays high → uterus stable → pregnancy maintained |
| What hormone rises first in early pregnancy? | hCG |
| When does hCG peak? | ~9–12 weeks |
| What happens at 10–12 weeks? | Placental shift (placenta takes over hormone production) |
| What structure produces progesterone early? | Corpus luteum |
| What produces progesterone later in pregnancy? | Placenta |
| What are the main effects of progesterone? | 👉 Inhibits uterine contractions 👉 Forms mucus plug |
| What are the main effects of estrogen in pregnancy? | 👉 Stimulates uterine growth 👉 Increases oxytocin receptors 👉 Promotes gap junctions |
| Difference between progesterone and estrogen in pregnancy? | 👉 Progesterone = maintains pregnancy 👉 Estrogen = prepares for labor |
| Why is progesterone supplementation stopped at 10–12 weeks? | Placenta produces enough progesterone |
| What is the full hormone timeline in pregnancy? | 👉 hCG rises → maintains corpus luteum → progesterone increases → placenta takes over (10–12 weeks) → estrogen rises → prepares for labor |
| What is the feto-placental unit? | Cooperation between fetus and placenta to make hormones |
| Who makes progesterone? | Placenta alone |
| Who makes estrogen in pregnancy? | Fetus + placenta together |
| What does the fetus produce for estrogen synthesis? | DHEA into 16-OH DHEA |
| What does the placenta do with DHEA? | Converts it into estrogen |
| What produces CRH in pregnancy? | Placenta |
| What happens to CRH over pregnancy? | It increases steadily |
| What is the role of CRH? | Helps initiate labor |
| What is the “placental clock”? | CRH timing labor |
| What happens if CRH rises too early? | Preterm labor (premature) |
| What hormone INITIATES the labor cascade? | CRH from the placenta |
| What does CRH stimulate in the fetus? | Fetal anterior pituitary |
| What hormone is released from the fetal pituitary? | ACTH |
| What does ACTH stimulate? | Fetal adrenal cortex |
| What hormone is produced by the fetal adrenal for lung development? | Cortisol |
| What does cortisol do in the fetus? | Stimulates surfactant production in lungs |
| What other hormone does the fetal adrenal produce? | DHEA |
| What happens to DHEA in the placenta? | Converted into estrogen |
| What happens to estrogen levels before labor? | They increase |
| What does estrogen do to uterine muscle cells? | Increases gap junctions |
| Why are gap junctions important? | Allow coordinated uterine contractions |
| What does estrogen do to oxytocin receptors? | Increases their number |
| Why is this important? | Uterus becomes more sensitive to oxytocin → stronger contractions |
| What else does estrogen increase? | Prostaglandin production |
| What do prostaglandins do? | Cervical softening (ripening) |
| What happens when all these changes occur? | Uterus contracts as a coordinated unit |
| What is the final result of this cascade? | 👉 Cervical dilation 👉 Labor (parturition) |
| What is the full labor cascade pathway? | 👉 CRH → ACTH → fetal adrenal → cortisol + DHEA → estrogen ↑ → gap junctions + oxytocin receptors + prostaglandins → contractions + cervical softening → LABOR |
| What type of feedback controls Stage 2 labor? | Positive feedback |
| What triggers oxytocin release? | Cervical stretching |
| Where is oxytocin released from? | Posterior pituitary |
| What does oxytocin do? | Increases uterine contractions |
| Why does labor intensify over time? | Positive feedback loop |
| When does Stage 2 end? | When baby is delivered |
| What drugs can induce labor? | 👉 Oxytocin (Pitocin) 👉 Prostaglandins |
| What happens in Stage 3 of labor? | Placenta is delivered |
| What is uterine involution? | Uterus returning to pre-pregnancy size |
| How long does involution take? | 4–6 weeks |
| What happens to estrogen and progesterone after birth? | They decrease rapidly |
| What helps uterus shrink after delivery? | Oxytocin |
| How does breastfeeding affect uterus? | 👉 Increases oxytocin 👉 Speeds uterine contraction |
| What is the full sequence of late labor? | 👉 Stage 2: positive feedback → oxytocin → contractions → baby delivered 👉 Stage 3: placenta delivered → hormones drop → uterus shrinks |
| What is infertility? | Failure to conceive after 12 months of unprotected sex |
| Most common causes of infertility? | Female, male, combined, idiopathic |
| Most common female issue? | Ovulatory dysfunction |
| What is a common male issue? | Low sperm count (oligospermia) |
| What does high FSH + low AMH mean? | Poor ovarian reserve |
| What does HSG test? | If fallopian tubes are open. A dye is used and an x-ray to show if the tubes are blocked. |
| What is oligospermia? | Low sperm count |
| What is azoospermia? | No sperm |
| What temperature is used in cryopreservation? | −196°C (liquid nitrogen) |
| Why does −196°C preserve cells? | Stops all metabolic and enzymatic activity |
| Are cells alive or dead during cryopreservation? | Alive but metabolically inactive |
| Why do cancer patients use cryopreservation? | To preserve fertility before treatment damages gametes |
| Why are embryos frozen in IVF? | To use extra embryos later or improve success rates |
| Why might someone freeze eggs electively? | To delay pregnancy |
| What forms first during freezing? | Extracellular ice |
| Why does extracellular fluid become hypertonic? | Ice excludes solutes, concentrating them |
| What drives water out of the cell during freezing? | Osmotic gradient from hypertonic extracellular fluid |
| What happens to the cell when water leaves? | It shrinks (dehydrates) |
| Why can excessive dehydration damage the cell? | High solute concentration becomes toxic |
| What is the most lethal form of freezing injury? | Intracellular ice formation; 👉 Intracellular ice: breaks membranes destroys organelles 👉 = cell death reducing amount of water in cells (and using a cryoprotectant) decreases risk of intracellular ice formation |
| What happens during slow cooling? | Excess dehydration and solute toxicity |
| What happens during rapid cooling? | Intracellular ice formation |
| What determines the optimal cooling rate? | Balance between dehydration and preventing intracellular ice |
| Why does optimal cooling rate vary by cell type? | 👉 Cell size 👉 Membrane permeability 👉 Water content |
| What is the purpose of cryoprotectants? | Reduce freezing damage |
| What defines permeating cryoprotectants? | They enter the cell |
| How do permeating CPs protect the cell? | 👉 Replace intracellular water 👉 Prevent ice formation |
| What defines non-permeating cryoprotectants? | They remain outside the cell |
| How do non-permeating CPs protect cells? | 👉 Promote dehydration 👉 Reduce extracellular ice |
| Why are both types used together? | To protect both intracellular and extracellular environments |
| What is vitrification? | Ultra-rapid freezing without ice crystal formation |
| Why does vitrification prevent damage? | No intracellular or extracellular ice forms |
| What cooling rate is used in vitrification? | Extremely rapid (1,000–10,000 °C/min) |
| What is the main effect of freezing on sperm? | Reduced motility and metabolism |
| Why is sperm motility reduced? | Membrane and mitochondrial damage |
| Membrane and mitochondrial damage | Large size and complex structure |
| What happens to the meiotic spindle during freezing? | It is disrupted → chromosome errors. Spindle re-forms after thaw and may reform in abnormal way |
| What is the cortical reaction during freezing? | Egg behaves as if fertilized prematurely |
| Why is ICSI required for frozen oocytes? | Sperm cannot penetrate hardened zona pellucida |
| Sperm cannot penetrate hardened zona pellucida | 👉 Controlled cooling 👉 Cryoprotectants 👉 Vitrification |
| What is autotransplantation? | Transplanting tissue back into the same individual |
| What is allotransplantation? | Transplant between two individuals of the same species |
| What is a major issue with allotransplantation? | Immune rejection |
| What is xenotransplantation? | Transplant between different species |
| Where is xenotransplantation commonly used? | Research (e.g., mouse models) |
| What is orthotopic transplantation? | Tissue placed in its normal anatomical location |
| Can natural pregnancy occur with orthotopic transplant? | Yes |
| What is a limitation of orthotopic transplantation? | Uncertain lifespan of graft |
| What is heterotopic transplantation? | Tissue placed in a non-natural location |
| Can spontaneous pregnancy occur with heterotopic transplant? | No |
| Why can’t natural conception occur in heterotopic transplant? | Egg is not near fallopian tube |
Created by:
bythedeli