embryology Flashcards
development of the limbs begins at what week?
end of the fourth week
upper limb bud appears by
day 24
upper limb patterns regulated by which genes?
homeobox genes (HOX)
limb buds elongate by proliferation of
mesenchyme
apex of each limp bud is the
ectoderm
apex limb bud ectoderm thickens to form
apical ectodermal ridge
role of the apical ectodermal ridge
inductive influence of limb mesenchyme to form blood vessels and cartilage
by what weeks has the mesenchymal tissue in the hand plates condensed to form digital rays?
end of the 6th week
during which week does the digital foot plates form
7th week
interdigital apoptosis is mediated by
bone morphogenetic proteins
cartilaginous precursors of limb bones develop by..
chondrification
chondrification of the limb bones occurs within and by what week?
mesoderm in the 6th weel
primary ossification centres appear by which weeks in the limbs?
8-12 weeks
all limb bones bar the clavicle develop by
endochondrial ossification
the clavicle forms by
membranous
which way does the limbs rotate in development
90 degrees laterally
lower limbs rotate by which direction in development
90 degrees medially
which week does peripheral nerves grow?
5th week
total absence of limb is called
amelia
partial limb absence is called
meromelia
long bone absence is called
phocomelia
all parts present but small is called
micromelia
presence of more than 5 digits is called
polydactyly
fusion of digit bones is called
osseous syndactyly
webbed fingers is called
cutaneous syndactyly
thalidomide causes
meromelia
congenital club foot is called
talipes equinovarus
most common birth defect is
congenital heart defects
greatest risk time period for teratogens
week 3 and 11
functional and growth defects are more likely to occur after how many weeks?
12
rubella triad
sensorineural deafness, eye abnormalities, congenital heart disease
cervical kidneys are called
pronephros
thoracolumbar kidneys are called
mesonephros
pelvic functional kidneys are called
metanephros
cloaca divides to from
rectum and urogenital sinus
mesonephric duct drains into the
urogenital sinus
urogenital sinus forms the
urinary bladder and the urethra
at week 6 the mesonephros forms
genital ridge
weeks cells germ cells migrate from where to form
the yolk sac to form primitive sex cords
primitive sex cords consist of
mesenchyme of the genital ridges and germ cells from the yolk sac
mesonephric duct in men forms
epididymis, vas deferens and seminal vesicle
paramesonephric duct in men
degenerates
urogenital sinus in men forms
bladder, urethra, and prostate
in females the mesonephric duct
degenerates
in females the paramesonephric duct
forms the fallopian tube, uterus, cervix and part of the vagina
the urogenital sinus in females forms
bladder and lower part of the vagina
SRY gene encodes for
testis determining factor
in men Sertoli cells secrete what
Mullerian inhibiting substance that stimulates paramesonephric duct degeneration
interstitial cells of Leydig are formed from
mesenchyme
caudal end of the paramesonephric duct becomes
uterus, and superior part of the vagina
descent of testis and ovaries begins
week 7
testis enter scrotum week
39
a heavily indented uterus is called
bicornuate uterus
a slightly ridged uterus is called
arcuate uterus
two cervixes and two uteruses is called
complete duplication
one cervix but two uteruses is called
septate uterus
