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Embryo Farmer Test 1

Embryology - Dr. Farmer - Test 1

QuestionAnswer
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
Created by: lkeith