Repro - Embryology

ekadar's version from 2016-03-13 07:36

When does this happen?

Question Answer
Fertilization by sperm forming zygote, initiating embryogenesisDay 0
hCG secretion begins after implantation of blastocystwithin week 1
Bilaminar disc (epiblast, hypoblast)within week 2
2 weeks, two layers
Trilaminar discwithin week 3
3 weeks 3 layers
Gastrulationwithin week 3
Primitive streak begins to formwithin week 3
Notochord begins to formwithin week 3
Mesoderm and its organization begin to formwithin week 3
Neural plate begins to formwithin week 3
Neural tube formed by neuroectodermWeek 3 and closes by week 4
OrganogenesisWeeks 3-8
Extremely susceptible to teratogensweeks 3-8
Fetal movementweek 8
Fetus looks like a babyweek 8
Heart begins to beatweek 4
Upper and lower limb buds begin to formweek 4
4 weeks, 4 limbs
Genitalia have male/female characteristicsweek 10
Start of fetal periodweek 8
Embryonic periodweeks 3-8


Question Answer
Dizygotic twinsarise from 2 eggs that are separately fertilized by 2 different sperm
always 2 zygotes
2 separate amniotic sacs and 2 separate placentas (chorions)
Monozygotic twinsarise from 1 fertilized egg that splits into 2 zygotes early in pregnancy
The degree of difference between the twins depends on when the fertilized egg splits into 2 zygotes- this timing determines the # of chorions and amnions
Most monozygotic twins split when?4-8 days
If monozygotic twins split 0-4 days...Dichorionic, diamniotic
If monozygotic twins split 4-8 days...Monochorionic, diamniotic
If monozygotic twins split 8-12 daysMonochorionic, monoamniotic
If monozygotic twins split >13 daysmonochorionic, monoamniotic, conjoined twins

From the very beginning...

Question Answer
Cytotrphoblastinner layer of chorionic villi
makes cells
Syncytiotrophoblastouter layer of chorionic villi
secretes hCG - stimulates corpus luteum to secrete progesterone during first trimester
(structurally similar to LH)
Decidua basalisMaternal component of palcenta - derived from the endometrium
Maternal blood in lacunae
Umbilical cord vessels2 arteries - return deoxy blood from fetal internal iliac arteris to placenta
1 vein - supplies oxygenated blood to fetus, drains via ductus venosus to IVC
Umbilical vessels are derived from what?allantois
Urachal duct3rd week: yolk sac forms allantois → extends into urogenital sinus → becomes urachus (a duct between bladder and yolk sac)
Patent urachusurine discharge from ubilicus
Vesicourachal diverticulumoutpouching of bladder
Vitelline duct7th week: obliteration of vitelline duct (omphalo-mesenteric duct) which connects yolk sac to midgut lumen
Vitelline fistulameconium discharge from umbilicus
Meckel's diverticulumpartical closure - patent portion attached to ileum
may have ectopic gastric mucosa → melena, periumbilical pain, ulcer
1st aortic arch →part of maxillary artery (branch of external carotid)
2nd aortic arch →Stapedial artery and hyoid artery
3rd aortic arch →Common Carotid artery
proximal part of internal Carotid artery
3rd letter of the alphabet=C
4th aortic arch →Left side: aortic arch
Right side: proximal part of right subclavian artery
4=4 limbs (systemic)
6th aortic arch →Proximal part or pulmonary arteries
Ductus arteriosus (on left side only)
[Pulmonary and the pulm-to-systemic shunt]
Branchial cleftsderived from ectoderm
AKA branchial grooves
Branchial archesderived from mesoderm (muscles, arteris) and neural crest (bones, cartilage)
Branchial pouchesderived from endoderm
Branchial apparatus (pharyngeal apparatus)CAP covers outside from inside:
Clefts = ectoderm
Arches = mesoderm
Pouches = endoderm
1st branchial cleft becomes...external auditory meatus
2nd-4th branchial clefts become....cysts

Random & genital embryo

Question Answer
Cleft lipfailure of fusion of maxillary and medial nasal processes (formation of 1° palate)
Cleft palatefailure of fusion of lateral palatine processes, nasal septum, and/or median palatine process (formation of 2° palate)
Female genital embryologydefault development
mesonephric duct degenerates and paramesonephric duct develops
SRY gene on Y chromosomeproduces testis-determining factor (testes development)
Sertoli cellssecrete Mullerian inhibitor factor → suppress development of paramesonephric ducts
Leydig cellssecrete androgens that stimulate the development of mesonephric ducts
Paramesonephric (Mullerian) ductDevelops into female internal structures:
fallopian tubes
upper portion of vagina (lower portion from urogenital sinus)
Presentation of Mullerian duct abnormalitiesanatomical defects may present as primary amenorrhea in females with fully developed secondary sex characteristics
Mesonephric (Wolffian) ductDevelops into male internal structures (except prostate): SEED
Seminal vesicles
Ejaculatory duct
Ductus deferens
Bicornuate uterusUrinary tract abnormalities and miscarriages
results from incomplete fusion of paramesonephric ducts
No sertoli cells but are XYdevelop both male and female internal genitalia and male external genitalia
Lack of Mullerian inhibitory factordevelop both male and female internal genitalia and male external genitalia
5α-reductase deficiencymale internal genitalia
ambiguous external genitalia until puberty
Structures arising from genital tuberclemale: glans penis, corpus cavernosum/spongiosum
female: glans clitoris, vestibular bulbs
Structures arising from urogenital sinusmale: bulbourethral glands, prostate gland
female: greater vestibular glands, urethral and paraurethral glands
Structures arising from urogenital foldsmale: ventral shaft of penis (penile urethra)
female: labia minora
Structures arising from labioscrotal swellingmale: scrotum
female: labia majora
HypospadiasOpening of penile urethra on inferior (ventral) side of penis due to failure of urethral folds to close
EpispadiasOpening of penile urethra on superior (dorsal) side of penis d/t faulty positioning of genital tubercle
Assoc w exstrophy of the bladder
When you have Epispadias, you hit your Eye when you pEE
Male remnant of gubernaculum (band of fibrous tissue)anchors tests within scrotom
Female remnant of gubernaculum (band of fibrous tissue)ovarian ligament + round ligament of uterus
Male remnant of processus vaginalis (evagination of peritoneum)forms tunica vaginalis
Female remnant of processus vaginalis (evagination of peritoneum)obliterated