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At what week is the embryo become the fetus?
8 weeks
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During the first two weeks of development the zygote is not susceptible to teratogens
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What is the most common birth defect?
Cleft lip and palate
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Male sperm begin forming when?
At puberty due to surge of LH and FSH
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In Meiosis how many cross over events occur?
30-40, 1-2 per chromosome
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When do homologous pairs align in meisosis?
During metaphase I
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When do primordial germs cells form in embryogenesis?
During week 2, in epiblast and hypoblast
4-6 weeks in polar body wall at gential ridge form the gonad
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How long is the process for male gametes?
70-74 days
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What happens at puberty in males to start spermatogenesis?
Leydig Cells are exposed to LH and in turn produce testosterone
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How early is egg formation in femals?
Week 6 of embryo
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Describe oogenesis pre-puberty?
mitosis produces many oogonium
primary oocyte fetally undergo meiosis I and arrest at prophase
female born with 400K-600K primary oocytes
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Describe oogenesis puberty?
a primary oocytew undergoes oogenesis
LH inc and leads to finish meiosis I, forming secondary oocyte and polar body
then enters meiosis II and stops at metaphase II until fertilization
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Why does a polar body form in oogenesis?
The cytoplasm from the polar body if robbed by the secondary oocyte to increase it's lifespan until implantation which does not occur for 2 weeks
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What does the follicle produces?
Estrogen and progesterone
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describe folliculogensis pre-puberty?
start as squamous cells
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describe folliculogeneiss at puberty?
FSH stimulates 5-15 of primordial follicle to re-enter folliculogensis
cells fatten and become cuboidal and begin produicing estrogen
Zona Pellucida forms (glycoprotein layer) important until implantantion, not needed when implanting (can impede)
follicular cells secrete lots of lfuid to fill antrum
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What cells produce estrogen?
Granulosa cells
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What cells produce progesterone?
Thecal cells
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What are the three phases of female reproductive cycle?
- Luteal
- Secretory
- Menstrual or uterine
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What hormone dominates luteal phase?
Progesterone
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How does birth control work?
High P4 and High estrogen causes LH to stay low.
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What is the most common numerical chromosome abnormality?
Trisomy caused by non-disjunction
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Trisomy 21
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Trisomy 18
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Trisomy 13
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Klinefelters
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Turner Syndrome
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47 XXX
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Two microdeletion syndromes, name and describe?
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What is the embryo termed from 1-2 weeks?
Morula (16 cells) or blastocyst
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What is the embryo termed week 2?
Embryo, bilaminar disk
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What is capacitation?
Sperm undergo breakdown of glycoprotein coat by uterine secretions exposing receptors that allow to penetrate the egg
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What is the path of the egg from ovary to uterus?
Ovary to abdominal cavity to infundibulum to ampulla to isthmus then to uterus
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Union of egg and sperm phases?
- 1. Corona Radiata: penetration by capacitated sperm
- 2. Zona Pellucida: penetrated by acromsomal rxn after binding of proteins sperm-egg
- 3. Zona Reaction: enzymes release in egg hardens to prevent any other sperm, meisosis II finishes
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Zygote forms after sperm fertilizes egg and meiosis II finishes in egg
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What is the function of zona pelucida after fertilization?
Limits growth of embryo allowing cells to be more condensed and have different contacts
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What cells form the placenta?
The trophblasts or periphery cells
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End of second week the embryoblast has what two layers?
Epiblast (dorsal) and hypoblast (ventral)
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What does the sphlanchnopleuric mesoderm give rise to?
connective tissue that surrounds the umbilical cord
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What is the synctiotrophoblast responsible for?
Lose cell membrane releasing enzymes that erode the uterus and produce HCG which allows P4 to continue to be produced
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When is uteroplacenta circulation established for nutrition of embryo?
Day 12
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What does GIFT stand for?
Gamete into Fallopian Tube
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What is a molar pregnancy?
growth of placental material, secretes HcG, 1% of pregnancies, all trophoblastic cells
5% of moles cause carcinoma
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When does the primitive streak form and the embryo is termed going through gastrulation?
Beginning week 3
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At what areas of the embryo will you not find any mesoderm?
Buccopharyngeal and cloacal membranes, ecto and endo derms approximate each other
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When does neuralation begin?
Day 18
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What do neural crest cells differentiate into?
sensory ganglia, ANS, and glial cells
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What is dextro cardia?
Gastrulation defect, heart apex lies on the right side of the body
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What is situs inversus?
Gastrulation defect can be complete or incomplete, organs are not where they should be, reveresed
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When the primitive streak does not regress at 4th week what can happen?
sacrococcygeal terotoma may form, benign tumor
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When are organs done developing?
by week 8, now fetal period where everything rapidly grows
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What is lanugo?
fines hairs weeks 17-20 that cover fetus, degenerate before birth
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What is vernix caseosa?
waxy cheese sebaceous fluid covering fetus weeks 17-20, antibacterial
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When do the testes decend from the posterior abdominal wall?
Weeks 17-20
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When is surfactant begin to be produced?
Weeks 21-25, by type II cells, sufficient surfactant is present week 28
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Blood formation and weeks 9-12?
Shifts from liver to spleen
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Blood formation and weeks 26-29?
shift from spleen to the bone marrow
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What are ways to monitor fetal development?
- 1. Ultrasound: noticeable defects
- 2. Maternal serum screens: downs syndrome
- 3. Amniocentesis: diagnostic
- 4. Chorionic villi sampling: diagnostic
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Weeks 30-35, significant changes?
pupillary light reflex,
testes reach scrotum, mine were at 2 weeks!
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Breathing and weeks 26-29?
can occur under control of CNS
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When is the blink reflex present?
Weeks 21-25
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When do bones begin to ossify?
weeks 9-12
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