Reproduction Flashcards
sonic hedgehog gene
produced at base of limbs in zone of ploarizing activity. Involved in patterning along anterior posterior axis. Invovled in CNS development; mutation can cause holoprosencephaly.
Wnt-7 gene
produced at apical ectodermal ridge (thickened ectoderm t distal end of each developing limb). Necessary for proper organization along dorsal-ventral axis
FGF gene
produced at apical ectodermal ridge. Stimulates mitosis of underlying mesoderm, providing for lengthening of limbs.
Homeobox (hox) genes
involved in segmental organization of embryo in a craniocaudal direction. Hox mutations–> appendages in wrong locations
Early fetal development less than a week
day 1: fetilization by sperm, forming zygote, initiating embryogenesis day 2: zygote day 3: morula day 5: blastocyst Day 7-10: implantation
within a week of implantation
hcg secretion begins around the time of implantation of blastocyst by the synctiotrophoblast at 8 weeks the placenta takes over
within week 2
bilaminar disk (epiblast, hypoblast) 2 weeks = 2 layers
within week 3
trilaminar disc 3 layers
-gastrulation
primitive streak, notochord, mesoderm and its organization, neural plate begins to form.
weeks 3-8
neural tube formed by neuroectoderm and closes by week 4
- organogenesis
- extremely susecptible to teratogens
week 4
heart begins to beat!
4 weeks 4 limbs
week 6
fetal cardiac activity visible by transvaginal ultrasound
week 10
genitalia have male/female characteristics
mesoderm
muscle, bone (note the bones of skull), connective tissues, serous lining of body cavities (peritoneum), spleen (derived from foregut mesentery)
cardiovascular structures, lymphatics, blood, wall of gut tube, vagina, kidneys, adrenal cortex (the medulla is neural crest), dermis, testes, ovaries
The notochord induces overyling ectoderm to become neuroectoderm which then forms neural plate
the neural plate becomes the neural tube and neural crest cells
the notochord becomes the nucleus pulposus of the intervertebral disc in adults
mesodermal defects VACTERL
Vertebral defects anal atresia cardiac defects trancho-esophageal fistula renal defects limb defects (bone and muscle)
Endoderm
gut tube epithelium, including anal canal ABOVE the pectinate line
-most of urethra (derived from urogential sinus), luminal epithelial derivatives (lung, liver, gall bladder, pancreas, eustatchian tube, thymus, parathyroid, thyroid follicular cells)
recall the pharyngeal pouches are derived from the endoderm!
Ectoderm
surface ectoderm
neuroectoderm CNS
neural crest cells PNS and nearby structures
surface ectoderm
- adenohypophysis (anterior pit, from rathke pouch)
- lens of eye, epithelial linings of oral cavity, sensory organs of ear, olfactor epithelium, epidermis, anal canal BELOW the pectinate line, parotid, sweat, and mammary glands
neuroectoderm
brain (neurohypophysis post pit, CNS neurons, oligodendrocytes, astrocytes, ependedymal cells, pineal gland)
- retina and optic nerve
- spinal chord
neural crest
PNS (dorsal root ganglia, CN, celiac ganglion, schwann cells, ANS)
- melanocytes
- chrommaffin cells of adrenal medulla
- parafollicular C cells of thyroid
- pia
- archnoid
- bones of skull
- odontoblasts
- aorticpulmonary septum
agenesis
absent organ due to absent primordial tissue
aplasia
absent organ despite presence of primordial tissue
hypoplasia
incomplete organ development; primordial tissue present
dizygotic twins
will have two separate sperm
-2 separate amniotic sacs, placentas (chorions)
monozygotic twins
split early:
separate placenta and dichorionic and diaminiotic
or fused placenta but still dichorionic and diaminiotic
a lil later:
monochorionic
one placenta
diamniotic
even later
monochorionic, once placenta and one aminiotic sac
super late
monochorionic monoamniotic conjoined twins =(
placental development
fetal
cytotrophoblast -inner layer of chorionic villi
synctioblast- out layer of chorinoic villi, secretes hcG
mommy:
decidua basalis: derived from the endometrium, maternal blood in lacunae
Umbilical chord: 2 arteries and 1 vein
derived from allantois
arteries return deoxygenated blood from the fetal internal iliac arteries to the placenta
the veins supply oxygenated blood from the placenta and drain into the IVC from the liver or shunted via the ductus venosus
urachus a duct between the fetal bladder and yolk sac
in the 3rd week the yolk sac forms the allantois which extends into the urogenital sinus
-allantois becomes the urachus a duct between the fetal bladder and yolk sac
Vitelline duct connects the yolk sac to the midgut lumen
7th week obliteration of vitelline duct (omphalo-mesenteric duct)
Patent urachus
-urine discharges from the umbilicus
urachal cyst
-partial failure of urachus to obliterate, fluid filled cavity lined with uroepithelium, between umbilicus and bladder, –can lead to infection and adenocarcinoma
vesicourachal diverticulum
outpouching of bladder due to failure of urachus to obliterate
vitelline fistula
failure of vitelline duct to close
-meconium discharge from umbilicus
meckel diverticulum
- partial closure of the vitelline duct, with patent portion attached to ileum (true diverticulum)
- may have ectopic gastic mucosa and or pancreatic tissue –> melena, periumbilical pain and ulcers
male
SRY gene on Y chromosome produces testis determining factor, testis develop
- in the testis the sertoli cells secrete mullerian inhibitory factor MIF that supresseds development of the female paramesonephric ducts
- leydig cells in the testis secrete androgens that stimulate the development of mesonephric ducts
mesonephric (wolffian duct)
develop into MALE INTERNAL structures except the prostate!!
-seminal vessicles, epididymis, ejaculatory duct, ductus deferens
paramesonephric (mullerian) duct
develops into female internal structures:
fallopian tubes, uterus, and UPPER portion of vagina
urogential sinus
lower portion of vagina ( greater vestibular glands or batholin and urethral and paraurethral glands of skene)
males:
prostate and bulbourethral glands of cowper
bicornuate uterus
results from INCOMPLETE fusion of paramesonephric ducts
can lead to recurrent miscariages
a complete failure would result in double uterus and vagina!
urogenital folds
females: labia minora
males: ventral shaft of penis (penile urethra)
labia scrotal swelling
female: labia major
male: scrotum
genital tubercle
femals: glans clitoris
males: glans penis
females: vestibular bulbs
males: corpus cavernosum and spongiosum
Congenital penile abnormalities:
hypospadias
- abnormal opening of penile urethra on INFERIOR (ventral) side of penis due to failure of urethral folds to close
- more common than epispadias
- fix it to prevent UTI
- hypo is below
Congenital penile abnormalities:
epispadias
abnormal opening of penile urethra on SUPERIOR (dorsal) side of penis due to faulty positioning the genital tubercle
Exstrophy of the bladder is associated with Epispadias.
When you have Epispadias you hit your Eye when you pEE
Descent of testes and ovaries:
Gubernaculum (band of fibrous tissues)
male remnant: anchors testes within scrotum
female: ovarian ligament + round ligament of uterus
Descent of testes and ovaries: processus vaginalis (evagination of peritoneum)
male: form the tunica vaginalis
female: obliterated
In early life the testes are located in the peritoneal cavity, descend into the scrotum, during descent they accompanied by the invagination of peritoneum the processus vaginalis. Which then becomes the tunica vaginalis its remnant. If it does not form a remnant?
failure of obliteration leads to persistent connection between the scrotum and the peritoneal cavity though the inguinal canal
- when the opening is small fluid can leak in
- if the opening gets larger –> indirect inguinal hernia
- a bulge on the groin that increases during straining is the typical presentation
