Embryology part 2 Flashcards
Patent foramen ovale
forms between the septum primum and septum secundum, allowing oxygenated placental blood to cross over from right to left atrium during intrauterine life
fusion of SP with SS occurs by 2 years of age in 75% of people, closing PFO
Atrial septal defect
allows left to right shunting of blood
endocardial cushions
key event in heart development
abnormalities can lead to atrial and vsd, transposition of great vessels (arteries) and other anomalies
development of aortic arches
4th and 5th week- branchial/pharyngeal arches form, receiving a blood vessel of aortic sac called aortic arches
3rd arch- common carotid (internal carotid)
4th arch- aorta
6th arch- pulmonary artery
ductus arteriosus
connects pulmonary arteries to arch of aorta, bypassing fetal lungs
closes and forms ligamentum arteriosum after birth
blood flow prior to birth
oxygenated blood from placenta, passes through umbilical vein, ductus venosis, ivc, into RA, blood jets through foramen ovale in interarterial septum sending blood into left atrium instead of right atrium, bypassing fetal lungs
second bypass occurs at ductus arteriosus (fetal lungs have high vascular resistance) , allowing blood pumped out of pulmonary artery to join descending aorta
blood flow after birth
with first few breaths, bradykin released from lungs decreases vascular resistance within the lungs, and bradykinin stimulates smooth muscle in wall of ductus arteriosis to contract causing increase in blood flowing to lungs
rise in blood flow to lungs increases blood flowing from lungs returning to left atrium, increasing pressure within LA
blood flow within RA drops as blood flow within umbilical veins is lost, reducing pressure within right atrium
pressure within LA greater than RA, septum primum is pushed against septum secundum, closing foramen ovale, closing atrial shunt
What medication helps close pda
indomethacin- prostaglandin synthesis inhibitor because pge-2 is responsible for keeping ductus arteriosis open
also ibuprofen
what medication helps keep pda open
prostaglandin analogs- alprostadil or misoprostol (pge1 analogs) keep ductus arteriosis open in cases such as new borns with transposition of great arteries
TGA
aorta and pulm artery arise from incorrect ventricle resulting in two closed circuits of blood flow
1st- RV to aorta to organs to RA back to RV to aorta delivers only deoxygenated blood to organs resulting in cyanosis
2nd- LV to pulm artery to lungs for oxygenation to LA back to LV
give Pge1 analogs- misoprostol, alprostadil
branchial clefts
ectodermal ingrowths
branchial pouches
endodermal outpocketings
branchial arches
mesenchymal core- mesoderm and neural crest in between clefts and pouches
which aortic arch provides most adult blood supply to head and neck
third
Pierre Robin Sequence
first arch syndrome cleft soft palate micrognathia glossoptosis (downward displacement of tongue) natal teeth receding chin
Treacher Collins Syndrome
first arch syndrome colobomas (malformation of eye) hypoplasia of mandible malar hypoplasia--> absence of zygomatic bones Malformed pinnae
DiGeorge Syndrome
cardiac, abnormal facies, thymic hypoplasia, cleft palate, hypocalcemia, 22q11
anomalous development of 3rd and 4th branchial pouches
abnormal hard palate and visualization in nasal cavity- failure of fusion of
palatal shelves
holoprosencephaly and FAS
Holoprosencephaly is a disorder caused by the failure of the prosencephalon (the embryonic forebrain) to sufficiently divide into the double lobes of the cerebral hemispheres. The result is a single-lobed brain structure and severe skull and facial defects.
alcohol alters pattern of migration and differentiation of ncc (low levels of superoxide dismutase and catalase, retinoic acid sensitivity)
permanent kidney
metanephric kidney- from intermediate mesoderm - sprouts from mesonephric ducts
only nephron formation is complete at birth; after birth, elongation of segments and functional maturation occurs resulting in dramatic postnatal increase in size
significance of urine formation early in development
key component of amniotic fluid which: cushions embryo control of body temp prevents adherence of amnion to embryo permits symmetrical external growth of embryo allows free movement of embryo
renal agenesis
unilateral: 1/1000, only a problem if other defects are present
bilateral: 1/3000 births, oligo, incompatible with post natal life
anomalies related to ascent of kidneys
ectopic kidneys (pelvic)
horseshow kidney- inf poles of kidneys are fused, ascent blocked by IMA
multiple renal vessels
Wilm’s tumor
nephroblastoma
most common primary renal tumor affecting children (2-5 years old) and 4th most common pediatric tumor
mutation of WT-1 gene
histo- tightly packed cells, fibrocytic or spindle shaped cells, poorly formed tubules
triphasic: blastemic, stromal, epithelial components
polycystic kidneys
recessive- renal failure in infancy, cysts from collecting tubules
dominant- renal failure in adulthood, cysts anywhere
Cloaca
divides into urogenital sinus and anorectal canal
urorectal septal anomalies and imperforate anus
fistulas result from incomplete septation of hindgut from urogenital sinus by urorectal septum, or if cloaca is too small
median umbilical ligament
initially, bladder is continuous with allantois which forms the urachus, which is known in adult as median umbilical ligament
can have a fistula, cyst, or sinus
exstrophy of bladder
exposure and protrusion of posterior wall of bladder through abdominal wall
epispadias
uretrha opens on dorsal surface of penis
hypospadias
urethra opens on venral surface of penis
adrenal glands development
cortex- from intermediate mesoderm
Medulla- from ncc
regulation of adrenal gland
CRH from hypothalamus leads to secretion of ACTH from anterior pituitary–> cortisol from adrenal cortex
inc secretion of cortisol feeds back on ant pit decreasing acth secetion and decreased crh from hypothalamus
hypertrophy of fetal adrenal cortex
inc dehydroepiandrosterone (most often due to C21 hydroxylase enzyme mutation- inability to synthesize corticosteroids)–> inc secretion of ACTH and CRH–> more dehydroepiandrosterone–> inc hydroxyprogesterone–> masculinization of female genitalia (fusion of labia majora and enlargement of clitoris)
congenital virilizing hyperplasia (adrenogenital syndrome)
pseudohermaphroditism
reproductive system
gonads, internal duct system, external genitalia
initially two sexes develop in identical fashion- indifferent stage
acquisition of male and female characteristics at 7th week of development
female development
default pw
mesonephric duct degenerates and paramesonephric duct develops into internal duct system
male
SRY on Y chromosome is testis determining factor
Mullerian inhibitory factor from sertoli cells in testis suppresses paramesonephric ducts development and induces apoptosis of structures
androgens from leydig cells stimulate development of mesonephric ducts into male internal duct structures (seminal vesicle, epididymis, ejaculatory duct, vas deferens)
What inhibits paramesonephric ducts in male repro
mullerian inhibiting substance from sertoli cells
vaginal development
fornices and upper portion of vagina formed by vacuolization of paramesonephric tissue
lower portion of vagina formed by vacuolization of sinovaginal bulbs
uterine abnormalities
caused by persistence of uterine septum or obliteration of lumen of uterine canal
uterus didelphys with double vagina
uterus arcuatus (indent at top of uterus)
uterus bicornis
uterus bicornis with rudimentary horn
atresia of cervix
atresia of vagina
androgen insensitivity syndrome
X linked recessive condition resulting in failure of normal masculinization of external genitalia in chromosomally male individuals
complete or partial syndrome
complete- female external genitalia with normal labia, clit, and vaginal introitus
partial- mildly virilized female external genitalia to midly undervirilized male external genitalia (hypospadias, diminished penile size)
5 alpha reductase deficiency
inability to convert testosterone to dihydrotestosterone
genitala may appear male with underdevelopment and hypospadias or female with clitoromegaly
individuals masculinize at puberty because pubescent changes are due to testosterone, not dht
paramesonephric duct agenesis
xx genotype, normal height, weight, normal external genitalia, normal breast development, normal pubic hair development, absent menses
failure of mullerian duct to develop
Turner syndrome
XO
short stature, low hair line, widely spaced nipples, poor breast development, elbow deformity, web neck with fold of skin, brown spots, rudimentary ovaries, no menstruation
Klinefelter syndrome
XXY
gynecomastia, long limbs, decreased upper/lower segment ratio, testes and penis are small, no evidence of pubertal development
problems with reading, writing, math, spelling
infertility
cryptochidism
failure of testes to reach scrotal sac
inguinal hernia
vaginal process remains open communication with peritoneal cavity, portions of intestinal loops often descend toward and occasionally into scrotum, causing inguinal hernia
