| Question |
Answer |
| Embryology |
Study of basic structure formation (2nd to 8th week) |
| Development |
Maturation using basic plan established during embryogenesis; includs pre- and postnatal periods |
| Teratology |
Study of causes of malformations (birth defects) |
| Descriptive Embryology |
Earliest branch; when and how process carried out, Hippocrates described in 500 BC |
| Experimental Embryology |
Why a process occurs at a praticular time and in a particular manner; uses mouse and chick model |
| Gametogenesis |
Production of 2 cells required for new individual, meiosis, spermatogenesis/spermiogenesis; oogenesis |
| Meiosis |
Reduces chromosome # by half (23 pair (22+2) to 22+1); 2 divisions - 1 round of DNA replication; 1st division reduces 46 (diploid) to 23 (haploid); primary germ cells divide by meiosis; Male - 4 gametes from primary, female - 1 gamete from primary |
| Primary germ cells |
Primary spermatocyte and primary oocyte |
| Stem cells |
Spermatogonia, oogonia |
| Acrosome |
Cap containing enzymes needed for fertilization |
| Spermatogenesis to spermiogenesis |
Male testis, seminiferous tubules, begins at puberty and through whole life, stem cells can divide to produce more stem cells or primary germ cells, primary to secondary to 2 spermatids, spermiogenesis converts spermatids to spermatozoan (lose cytoplasm, |
| Spermatogenesis to spermiogenesis con't |
condense nucleus, acrosome, flagellum), about 64 days - staggered production |
| Oogenesis |
Ovary, begins during prenatal development, stem cells divide into stem cells or primary germ cell (surrounded by follicular cells) (primordial follicle), primary to 1st meiotic division, DNA synthesis, no stem cells after birth, primary arrested in |
| Oogenesis con't |
prophase of meiosis I, OMI causes maturation, 1 oocyte per month releases during ovulation (1st meiotic division finishes at ovulation), secondary oocyte and 1st polar body produced |
| Oogenesis/Spermatogenesis comparison |
Both produce haploids, mature gametes at puberty, Oogenesis - no oogonia after birth, primary makes 1 gamete, large, nonmotile, 1 per month, only until 50 years, spermatogenesis - after birth and through life, prim-4gametes, small motile, thru life |
| Chromosomal Abnormalities |
Nondisjunction - chromosomes don't separate during 1st or 2nd division, trisomy - 24 chromosomes (1xy, 22 no xy), down's, kleinfelters (pheno male, sterile), monosomy-single copy of chromosome, turner's (45, XO)-pheno female, sterile, |
| Abnormalities con't |
Translocations-damaged/broken, repaired to wrong spot, deletions, small or large segments missing |
| Morphological Abnormalities |
Sperm - 2 heads or tails (viable), nonmotile; Oocytes - 2 in one follicle (viable), more than one nucleus (non-viable) |
| Ovarian cycle |
28 days, follicular phase (1-12), ovulatory phase (12-14), luteal phase (15-28) |
| Follicular Phase |
Days 1-12, 5 to 15 follicles begin, 1 completes, oocyte with cuboidal follicular cells (granulosa cells) produce estrogens, antrum, zona pellucida-glycoprotein convering-through fertilization and 1st few divisions, stromal dev. of theca folliculi |
| Follicular Phase con't |
component of corpus luteum), primordial follicle (primary oocyte in prophase I - flat follicular cells), Graafian follicle-prior to ovulation, completes meiosis I, 1st polar body-haploid, cumulus oophorus (both detach) |
| Ovulatory Phase |
Days 12-14, Ovarian surface bulges, avascular spot-stigma, surface degenerates, follicle ruptures, oocyte and follicular fluid extruded into peritoneum, secondary oocyte begins meiosis II, transported to uterine tubes via fimbria |
| Cumulus Oophorus |
Granulosa cells, detaches with oocyte from follicle, innermost layer is corona radiata (transfers cytoplasmic material into oocyte, source of nutrients ater fertilization) |
| Luteal Phase |
Corpus Luteum (from follicle and theca folliculi, temp endocrine gland, persists 20 weeks in pregnancy, nonpregnant lasts 10-12 days), produces progesterone |
| Ovarian cycle hormones |
GnRH (gonadotropin releasing hormone), FSH (follicle stimulating hormone), LH (luteinizing hormone) |
| GnRH |
Hypothalamus, acts on ant pit cells, causes secretion of LH and FSH |
| FSH |
Ant pit, promotes early development of ovarian follicles |
| LH |
Ant pit, final stages of follicle maturation, form corpus luteum, triggers ovulation, promotes development of corpus luteum |
| Uterine Structure |
Perimetrium (outer covering), Myometrium (middle muscle layer), endometrium (superficial functional layer and deep basal layer -implantation of embryo) |
| Menstrual (uterine) cycle |
28 days, menstrual phase (1-4), proliferative phase (5-14), secretory phase (15-28) |
| Menstrual phase |
Day 1-4, sloughing of functional layer |
| Proliferative phase |
Day 5-14, regeneration of functional layer from basal layer |
| Secretory phase |
Day 15-28, glands secrete glycogen, embryo implants about day 6 of secretory phase (day 20 of uterine cycle), if no fertilization, ischemia in functional layer leads to sloughing |
| Uterine cycle hormones |
Estrogen (estradiol), progesterone |
| Estrogen |
Especially estradiol, produced by follicular cells in ovary, promotes proliferation of endometrium during 1st half of uterine cycle |
| Progesterone |
Produced by corpus luteum of ovary, stimulates endometrial glands to secrete glycogen |
| Fertilization |
Sperm contact with oocyte to maternal and paternal chromosomal mingling (about 24 hours) |
| Requirements of fertilization |
Viability, location, ability of sperm to fertilize |
| Length of viability |
Sperm - about 24 hours or less, but up to 3 days; oocyte - 24 hours after ovulation |
| Location of fertilization |
In female tract under influence of female secretions, removal of glycoprotein coat over acrosome |
| Acrosomal Reaction |
After contact with zona pellucida, release of acrosomal enzymes (proteases) for penetration |
| Fertilization Phases |
Penetrate corona radiata (multiple sperm), penetrate zona pellucida (multiple sperm) - requires proteases (acrosin, hyaluronidase, neuraminidase), prevent polyspermy via cortical reaction and zona reaction, fusion of sperm and ocyte membrane, fuse pronucl |
| Cortical Reaction |
Release of granules (lysosomal enzymes) from oocyte due to penetration |
| Zona Reaction |
As in zona pellucida caused by enzymes from cortical reaction; inactivates sperm receptors |
| Fusion |
Oocyte and sperm membrane melt, oocyte membrane depolarizes, becomes impenetrable, oocyte completes meiosis II, secondary polar body, male/female pronuclei replicate DNA,fuse to form zygote (w/in 24hrs of ov), diploid, gender, cleavage, embryo/conceptus |
| # of sperm deposited? # of sperm in ampulla? Percent abnormal? |
200 to 600 million; less than 1000; about 10% |
| Birth control |
Pills, barriers, sterilization |
| In vitro fertilization |
Stimulate ovary to produce multiple oocytes, oocytes and sperm mixed in vitro, multiple 8-cell embryos implanted |
| Cleavage |
(blank) |
| Rules of 2's |
Embryoblast makes 2 germ layers; trophoblast makes 2 new tissues, blastocyst cavity remodeled 2 times, Two new cavities, Extraembryonic mesoderm splits to 2 layers |
| Trophoblast |
Forms cytotrophoblast (inner layer of mononucleated cells) and syncytiotrophoblast (outer multinucleate zone without distinct cell boundaries) |
| Cytotrophoblast |
Highly mitotic, eventually merges with syncytiotrophoblast, mononucleate |
| Syncytiotrophoblast |
Invasive, ngestive, digestive, multinucleate, single membrane |
| Embryoblast |
Hypoblast layer (small cuboidals adjacent to blastocyst cavity); epiblast (high columnars adjacent to amniotic cavity); amniotic cavity forms within |
| Amnioblasts |
Epiblast cells adjacent to amniotic cavity |
| Endometrial reaction in 2nd week |
Secretory phase, blastocyst embeds under compact layer in spongy layer between glands; glands secrete glycogen and lipids, tissue eroded by syncytiotrophoblast |
| Abnormal implantation |
Placenta previa - within uterus; ectopic - outside uterus (tubal, rectouterine-Douglas' pouch) |
| Hydatidiform mole |
Abnormal blastocyst, trophoblast only - no embryonic tissue, only paternal genes expressed, increased levels of HCG, can produce benign or malignant tumors, non-viable |
| Bilaminar germ disc |
Day 8, from embryoblast, epiblast, hypoblast |
| Epiblast |
Aka ectoderm, columnar cells, forms amniotic cavity within, amnioblasts |
| Hypoblast |
Aka primary endoderm, cuboidals, extraembryonic endoderm lines blastocyst (Heuser's membrae) about day 9, secondary (definitive) yolk sac about day 13 |
| Heuser's Membrane |
About day 9, exocoelomic cavity formed from Heuser's membrane and primary (primitive) yolk sac |
| Secondary yolk sac |
About day 13 from hypoblast, smaller than primary from Heuser's, exocoelomic cysts (eremnants of primary yolk sac) |
| Uteroplacental circulation |
Increased size limits diffusion, eventually done by placenta, syncytiotrophoblast (vacuoles about day 9) at embryonic pole, lacunae primordia of intervillous spaces of placenta, barriers are all fetal in origin, |
| Uteroplacental circulation con't |
endometrium (blood vessels dilate to form sinusoids), erosion of vessels and glands release contents into lacunae, cytotrophoblast - primary villi extend into lacunae - day 13, begun by developing EEM |
| Extraembryonic mesoderm (EEM) |
Appears about day 12, Between cytotrophoblast and germ disc, plus amnion and yolk sac, possibly from yolk sac endoderm, vacuolation makes 2 layers surrounding extraembryonic coelom (chorionic cavity), connecting stalk, chorionic villi |
| Chorionic cavity |
Aka extraembryonic coelom, somatopleuric mesoderm lines trophoblast, splanchnopleuric mesoderm around yolk sac |
| Connecting Stalk |
Somatopleuric mesoderm connects germ disc to trophoblast lining (chorionic plate), will become umbilicus |
| Chorionic Villi |
Primary (only trophoblast cells) about day 13, secondary (core of mesoderm) - about day 16, Tertiary (contain and develop blood vessels in mesoderm) -3rd week |
| Gastrulation |
Formation of 3 germ layers (ectoderm, mesoderm, endoderm), cranio-caudal (longitudinal) axis, bilateral symmetry |
| Primitive Streak |
Formation of epiblast about day 16, primitive pit/primitive node, cell migration (invagination) of epiblast cells produces embryonic endoderm and mesoderm (mesenchyme) |
| Buccopharyngeal membrane |
Thickened hypoblast at cephalic region, lacks mesoderm |
| Notochord |
Mesenchymal (mesoderm) cells in midline form primitive pit to buccopharyngeal membrane, notochordal process(hollow tube) forms notochordal plate forms notochord, neureteric canal, cranial to caudal direction, basis for axial skeleton, |
| Notochord con't |
includes neural plate from in ectoderm - CNS, directs further development of mesoderm and endoderm |
| Neurenteric canal |
Transient connection between amniotic and yolk sac cavities |
| Ectodermal derivatives |
Maintain contact with external environment, epidermis and its derivatives, CNS - neural plate makes folds, makes tube, neural crest - ganglia, schwann cells, pia mater, arachnoid layer, melanocytes, craniofacial bones, |
| Ectodermal derivatives con't |
sense placodes (otic placodes - inner ear, lens placodes - lens of eye) |
| Mesodermal derivatives |
CT, muscle, circulatory system, kidneys, gonads, paraxial mesoderm makes somites makes skin, bone, muscle, intermediate mesoderm makes kidneys, gonads, lateral plate mesoderm-somatic (parietal) body wall, viscera, angioblasts-prim blood cells and endothel |
| Endodermal derivatives |
Epithelial gut lining, respiratory tract, urinary, liver, pancreas, thyroid and parathyroid, forms tubular gut by two foldings, cephalocaudal fold by rapid growth of nervous system, 3 regions (foregut - ant boundary is bucco), |
| Endodermal derivatives con't |
(prechordal plate), midgut - open to yolk sac via vitelline duct, hindgut - ends posteriorly at cloacal membrane |
| Placental origin |
MAternal - functional layer of endometrium,fetal - trophoblast and especially EEM (chorionic plate), primary secondary and tertiary villi |
| Placental structure |
Fetal (chorion), maternal (decidua), mature placenta - chorion frondosum and decidua basalis, decidual septa from decidual plate, cotyledons (compartments) |
| Fetal placental contributions |
Aka chorion, chorion frondosum - elaboration of villi at embryonic pole, chorion laeve - smooth, no villi at abembryonic pole |
| Maternal placental contributions |
Aka decidua, decidua basalis (decidual plate), adjacent to chorion frondosum, decidua capsularis at abembryonic pole, decidua parietalis - uterine wall away from implantation site |
| Circulation of placenta |
Spiral arteries, intervillous spaces, endometrial veins, separation of mat/fetal blood via fetal structures, initially 4 layers(endothelium, CT, cytotrophoblast, syncytiotrophoblast), at 4 months-2 layers (endothelium/syncytium) - placental membrane |
| Placental function |
Gaseous product exchange, metabolic product exchange, maternal antibody transmission, hormone production, passage of deleterious substances |
| Placental gas exchange |
O2 and CO2 |
| Metabolic placental exchange |
Carbs, amino acids, fatty acids, electrolytes, vitamins |
| Maternal antibodies |
Confers passive immunity for period of fetal immune immaturity, some can't pass through placenta |
| Placental hormone production |
Probably by syncytiotrophoblast, progesterone - maintain pregnancy from 4 months, estrogens, stimulate uterine growth, mammary gland development, hCG- similar to LH, provides basis for preg tests, somatomammotropin - similar to GH, gives fetus glucose |
| 4 fetal membranes |
1st tri - allantois, yolk sac; throughout development - chorion, amnion |
| Allantois |
Outpocketing from yolk sac about day 16, rudimentary in humans, only first tri |
| Yolk sac |
Disappears by end of 3rd month, 1st tri only |
| Chorion |
Fetal portion of placenta, chorionic cavity obliterated by expanding amnion by end of 3rd month, persists |
| Amnion |
Expands to fluid-filled sac which holds embryo/fetus and umbilicus, mostly H2O, derived from mat blood, fetal urine, increases to 1 liter at 37 wks, allows mvmt/protection, replaced every 3 hrs, PROM about 10%, polyhydramnios, oligohydramnios - birth def |
| Polyhydramnios |
Excess (1.5 to 2 liters); anencephaly and GI defects, can't swallow fluid |
| Oligohydramnios |
Reduced (less than 400ml), renal defects, can't replace fluids |
| Umbilical cord |
Primitive umbilical ring makes cord, oval line of reflection between amnion and ectoderm, contents at 5wks-conn stalk, allantois, vessels, yolk stalk, vitellie duct, coelomic canal conn. intra and extra embryonic coelom |
| Umbilical cord con't |
Mature umbilical cord (after month 3)-yolk stalk, allantois and coelomic canal disappear, vessels (2 art, 1 vein), Wharton's jelly-embryonic CT rich in proteoglycans protects blood vessels |
| Dizygotic twins |
Fraternal, 2 ova fertilized by 2 sperm, 2/3 of all twins, implant separately, separate chorion/amnion, placentas may fuse-erythrocyte mosaicism |
| Monozygotic twins |
Identical, 1/3 of all twins, single zygote that splits at diff times, 2 cell stage - separate implant, sep chorion/amnion/placenta; early blastocyst (most common)-sep amnion, same chorion/placenta, bilaminar germ disc-implant together, same am/chor/plac |
| Conjoined twins |
Siamese twins, zygote split at later stages, incomplete separation |
| Twin risks |
Low birth weight, increasedchance of prematurity and perinatal mortality |
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