Repro Embryology Flashcards
Sonic hedgehod gene
Produced at base of limbs in zone of polarizing. Involved in patterning along anterior-posterior axis. Involved in CNS development; mutation can cause holoprosencephaly.
Wnt-7 gene
Produced at apical ectodermal ridge (thickened ectoderm at distal end of each developing limb). necessary for proper organization along dorsal-ventral axis.
FGF gene
Produced at ectodermal ridge. Stimulates mitosis of underlying mesoderm, providing for lengthening of limbs.
Homeobox genes
Involved in segmental organization of embryo in a craniocaudal direction. hox mutation leads to appendages in wrong locations.
Within Week 1
hCG secretion around time of implantation of blastocyst
Within Week 2
Bilaminar disc (epiblast, hypoblast). 2 weeks= 2 layers
Within Week 3
Trilaminar disc. 3 weeks = 3 layers.
Gastrulation.
Primitive streak, notochord, mesoderm, and its organization, and neural plate begin to form.
Weeks 3-8 (embryonic period)
Neural tube formed by neuroectoderm and closes by week 4. Organogenesis. Extremely susceptible to teratogens.
Week 4
Heart begins to beat. Upper and lower limb buds begin to form. 4 weeks = 4 limbs.
Week 6
Fetal cardiac activity visible by transvaginal u/s
Week 10
Genitalia have male/female characteristics
How does gastrulation happen
Starts with epiblast invaginating to form the primitive streak, eventually establishing ectoderm, mesoderm, and endoderm germ layers.
What is primitive streak?
Forms in the blastula stage?????????????
What is a craniopharyngioma
Benign Rathke pouch tumor with cholesterol crystal, calcifications.
Mesodermal defects = ?
VACTERL: Vertebral defects, anal atresia, cardiac defects, tracheo-esophageal fistula, renal defects, limb defects (bone and muscle)
What kind of tissue is notochord?
Mesodermal
What is agenesis
Absent organ due to absent primordial tissue
What is aplasia
Absent organ despite presence of primordial tissue
What is hypoplasia
incomplete organ development; primordial tissue present
What is deformation
Extrinsic disruption; occurs after the embryonic period
What is disruption
Secondary breakdown of a previously normal tissue or structure (e.g. amniotic band syndrome)
What is malformation
Intrinsic disruption; occurs during the embryonic period (weeks 3-8)
What is sequence
Abnormalities result from a single primary embryological event (oligohydramnios resulting in Potter sequence)
Know what the embryologic derivaties are
………..
When are embryos most sensitive to teratogens?
Weeks 3-8. Before week 3: all or none effects. After week 8: Growth and function affected
Dizygotic twins aminion and chorion
Always diamniotic and dichrionic
What percent of twins are dizygotic
80%, monozygotic makes up 20%
Dichorionic, diamniotic monozygotes
Happens between 2-cell stage and morula stage, between 0-4 days post-fertilization (25%). can have fused or separate placenta
Diamniotic, monochorionic
Happens between Morula to blastocyst stage, 4-8 days, 75% of identical twins
Monochorionic, monoamniotic
If not conjoined, it happens between blastocyst and formed embryonic disc stage between 8-12 days and is 13 days
Components of placenta
Fetal component: cytotrophoblast (inner layer of chorionic villi), syncytiotrophoblast (outer layer of villi, secretes hCG)
Maternal component: Derived from the endometrium. Maternal blood in lacunae.
Where do umbilical arteries come from
Fetal internal iliac arteries
Allantois
Umbilical arteries and veins are derived from allantois
Urachus
3rd week: yolk sac forms allantois, which extends into the urogenital sinus. Allantois becomes the urachus, a duct between fetal bladder and yolk sac.
patent urachus
urine discharge from umbilicus
Urachal cyst:
artial failure of urachus to obliterate; fluid-filled cavity linked with uroepithelium, between umbilicus and bladder. Can lead to infection, adenocarcinoma.
Vesicourachul diverticulum:
outpouching of bladder
Vitelline duct
7th week: obliteration of vitelline duct (omphalo-mesenteric duct), which connects yolk sac to midgut lumen
Vitelline fistula
Meconium discharge from umbilicus
Meckel diverticulum
Partial closure, with patent portion attached to ileum (true diverticulum). May have ectopic gastric mucosa and/or pancreatic tissue leading to melena, periumbilical pain, and ulcers.
Aortic arch derivatives
1st: Part of maxillary artery (branch of external carotid) (1st arch is MAXimal)
2nd: Stapedial artery and hyoid artery (second=stapedial)
3rd: Common Carotid artery and proximal part of internal Carotid artery. (C is 3rd letter of alphabet).
4th: On left, aortic arch; on right, proximal part of R subclavian artery (4th arch (4 limbs)=systemic)
6th: Proximal part of pulm. arteries and (on left only) ductus arteriosus (6th arch=pulm. and the pulm.-to-systemic shunt (ductus arteriosus)
Organization of primitive pharynx
CAP (outside to inside): Cleft-Arch-Pouch
Cleft (Grooves) is ectoderm, Arch is mesoderm/neural crest (muscles, arteries, bones, cartilage), and Pouch is endoderm
Branchial Cleft Derivatives
1st cleft develops into external auditory meatus
2nd through 4th cleft forms temproary cervical sinuses, which are obliterated by proliferation of 2nd arch mesenchyme.
Persistent cervical sinus leads to branchial cleft cyst within lateral neck.
Know Branchial Arch Derivatives
???????????????
Which trigeminal branch is sensory only
V2
Mnemonic for branchial arch derivatives
When at the restaurant of the golden arches, children first tend to CHEW (1), then smile (2), then swallow stylishly (3) or simply swallow (4), and then speak (6)
What branchial arch doesn’t contribute to major developmental changes.
Arch 5
Treacher Collins syndrome
1st arch neural crest fails to migrate leading to mandibular hypoplasia and facial abnormalities
Congenital pharyngocutaneous fistula
Persistence of cleft and pouch leading to fistula between tonsillar area and lateral neck
What arches form the posterior 1/3 of tongue
Arches 3 and 4
Cleft lip
Failure of fusion of the maxillary and medial nasal process (formation of primary palate)
Cleft palate
Failure of fusion of the two lateral palatine processes or failure of fusion of lateral palatine processes with the nasal septum and/or median palatine process (formation of secondary palate).
Mnemonic for branchial pouches
Ear, Tonsils, bottom-to-top: 1. Ear 2. Tonsils 3. Dorsal (bottom for inferior parathryoids) 3. Ventral Thymus 4. Top: superior parathyroids
DiGeorge Branchial pouches
Aberrant development of 3rd and 4th pouches (T cell deficiency (thymic aplasia and hypocalcemia (failure of parathyroid development). Associated with cardiac defects (conotruncal anomalies)
MEN 2A Branchial pouches
Mutation of germline RET (neural crest cells): Adrenal medulla (pheo), Parathyroid (tumor): 3rd/4th pharyngeal pouch. Parafollicular cells (medullary thyroid cancer); derived from neural crest cells, associated with 4th/5th pharyngeal pouches
In women: what duct degenerates and which one develops
Mesonephrics degenerate and paramesonephrics develop
Male genital embryo
SRY on Y chromosome: Testis Determining Factor (testes development): Sertoli cells secrete MIF that suppresses paramesonephrics. Leydig cells secrete androgens that stimulate the development of mesonephric ducts.
Paramesonephrics (Mullerian)
Fallopian tubes, uterus, upper vagina (lower portion from urogenital sinus). Mullerian duct abnormalities result in anatomical defects that may present as primary amenorrhea in females with fully developed secondary sexual characteristics (functional ovaries)
Mesonephrics (Wolffian)
Develops into male internal structures (except prostate): Seminal vesicles, Epididymis, Ejaculatory duct, and Ductus deferens (SEED)
Bicornuate uterus
Incomplete fusion of paramesonephrics: recurrent miscarriages
What do Leydig cells produce and effect
Testosterone, develops mesonephrics (Wolffian): male internal genitalia except prostate
What does DHT do
Turns genital tubercle, urogenital sinus into the male external genitalia, prostate
What do Sertoli cells do
Produce Mullerian Inhibitory Factor: degenerates paramesonephrics (Mullerian) duct (female internal genitalia)
What happens if you lack sertoli cells
OR if you lack MIF: male and female internal genitali and male external genitalia
What happens if you have 5alpha-reductase deficiency
Can’t turn testosterone into DHT; male internal genitalia, ambiguous external genitalia until puberty (increased testosterone levels cause masculinization)
in men, what does the genital tubercle produce
Glans penis and corpus cavernosum and spongiosum
What does urogenital sinus produce in men
Bulbourethral glands (of Cowper), Prostate gland, ventral shaft of penis (penile urethra)
What does labioscrotal swelling in men produce
Scrotum
In women: what does genital tubercle produce
Glans clitoris and vestibular bulbs
In women: what does the urogenital sinus produce
Greater vestibular glands of Bartholin, Urthreal and paraurethral glands of Skene
In women: what does urogential folds produce
Labia minora
In women: what does labioscrotal swelling form
Labia majora
Why fix hypospadias?
To prevent UTIs
What is epispadias associated with
Exstrophy of the bladder
What does gubernaculum produce in women
Ovarian ligament + round ligament of uterus
What happens to processus vaginalis in men and women
In Men: forms tunica vaginalis, In women: it is obliterated
