Development Flashcards
what controls limb development after the initial budding of the mesoderm
ectodermal ridge
what does thalidomide cause
amelia and meromelia
failure to retract seal the abdominal wall after retraction of the gut is called
umbilical hernia
apart from the bladder and urethra, the rest of the urogenital tract is formed from the..
intermediate mesoderm
when does the blastocyst implant into the uterine wall
between 5-10 days
what is the commonest congenital heart defect
ventricular septal defect
what causes sinus invertus
complete failure of the cilia of the primitive node - pure change whether organs are set properly or back to front
what is the neural crest
the cells at the point of fusion of the neural tube
what is the yolk stalk
that part of the yolk sac that is still connected to the gut lumen that persists until it is finally pinched shut
what happens to the urorectal septum
it extends towards the cloacal membrane to divide the rectum from the urogenital tract
order of endoderm, ectoderm and mesoderm from top to bottom of the blastocoele
ectoderm mesoderm endoderm
two cell populations in the blastocyst
inner cell mass
trophoblast
what structural feature determines morula from blastocyst
blastocyst undergoes cavitation to form a cavity = blastocoele
what is the morula
16 cell stage of the embryo
what is the cause of congenital hip dislocation
the acetabulum is malformed
- can be due to genetic or mechanical problems in utero
fate of the neural crest?
cells migrate off and leave the neural tube to form elements of the nervous system that dont form the CNS, and the other random things
what happens to the inner cell mass
- first splits into epiblast and hypoblast
- then epiblast will splits into 3 layers - ectoderm, endoderm and mesoderm
what lies between the allantois and the hind gut
urorectal septum (part of the mesoderm)
how many live births have a birth defect
1:33
how do the trachea, lungs, liver and pancreas initially appear
as endodermal out-pocketings interacting with the mesoderm
how many pharyngeal arches are there
4
what is amelia and meromelia
amelia - absent limbs
meromelia - reduced limbs
how is the gut tube made
yolk sac separates from the embryo –> due to this some of the endoderm is pinched off
which tissues does the intermediate mesoderm give rise to
urogenital system
where does the heart develop from
the lateral splanchnic mesoderm
what causes VSD
when the intraventricular foramen is not filled by membranous part of IVS
what are somitomeres
swellings of the flat sheet of paraxial mesoderm lateral to the neural tube on both sides
components of the mesonephros
pronephric duct of the pronephros becomes the mesonephris duct with mesonephric tubules
what is the zygote
the single fertilized egg
how does the large intestine get to the right position in the body
it is pulled there by the rotation and lengethening of the small intestine
at what time of genstation does the mouth open to the outside
at 3 weeks –> ectoderm meets ectoderm (still present in humans - stratified squamous of mouth to respiratory epithelium that linkes pharynx)
what does the rest of the epiblast (that doesnt contribute to the embyro) and all of the primitive hypoblast give rise to
extra embryonic tissue
what happens to the mesonephric duct
- males –> redeployed and becomes the vas deferences
- females –> throw it away
which tissues does the lateral mesoderm give rise to
- ventrolateral body wall
- limb skeleton
- visceral pleura and peritoneum
- blood vessels and blood forming tissue
- heart
- wall of gut and respiratory tissues
what does mesenchyme refer to
ells that are isolated from each other, that are freely moving, and often have CT between cells
associations of the somatic and splanchnic mesoderm
somatic mesoderm associated with the ectoderm
splanchnic mesoderm associated with the endoderm
what happens to the allantois
gives rise to the bladder and urogenital tract
how is the penis formed
from the fusion of the urogenital folds
which forms first? the urinary system or the genital system
urinary system
what is the 1st identifiable structure that forms in the 3 layers of the epiblast
the notochord
what does the mesoderm give rise to
- dermis, blood, heart and BVs, kidneys and urogenital tract, gonads, most bones and muscles, and CT, walls of gut and respiratory tract (not lining), pleura, peritoneum, pericardium
what forms the fallopian tubes, the uterus and the upper 2/3 of the vagina in girls
the Mullerian duct
when does the blastocyst form
4 days
what is the bilaminar disc
epiblast + hypoblast
how does the allantois form
as a branch of the hind gut
failure of apoptosis of the cells between fingers can lead to
webbing or syndactyly (fused fingers)
what is the first sign of the appearance of the coelom
the split of the lateral mesoderm into somatic mesoderm above and splanchnic mesoderm below
neural crest derivatives
- dorsal root ganglia - sympathetic and parasympathetic ganglia - enteric ganglia - schwann cells - melanocytes - dentine - muscle, cartilage, and bone of skull, jaws, face and pharynx - outflow tracts of the heart (bottom 3 not part of the nervous system)
from what layer of the epiblast is the notochord derived from
mesoderm
what is the most common birth defect
heart defects
which part of the mesoderm becomes the appendicular skeleton
lateral mesoderm
what initially closes the gut tube to the outside world
mouth end = stomodeum
anus end = proctodeum and cloacal membrane (thin layers of ectoderm)
which part of the inner cell mass becomes the embryo
part of the epiblast
when do limbs start development
at the end of the 4th week as a little bud of mesoderm
which parts of the heart are developed from the neural crest
- parts of midline
- major outflow vessels
what does the endoderm give rise to
epithelium of the gut and associated organs
at what time in gestation is the morula
3 days
names of the 3 pairs of kidneys made during development
pronephros
mesonephros
metanephros
how do the commonest congenital heart defects form
as a failure of the fusion of the chambers of the heart
how does the epiblast split into 3 layers
by gastrulation
at what stage of somitomere development does one somitomere become independent
at the 20 somitomere stage
explain the heart development
forms a tube bilaterally –> bought together in the midline underneath the gut (between gut and ventral wall) –> fuse to produce 2 chambers (1 atria and 1 ventricle) with 2 outflows and 2 inflows –> heart then folded and fused to produce 4 chambers
where does the metanephros develop? and where does it migrate
at the bottom of the mesonephric duct –> moves upwards along the mesonephric duct
what do the sclerotome, dermotome and myotome become
sclerotome = axial skeleton
dermatome = dermis of skin
myotome = back muscles and limb muscles
what is hypospadiasis
failure of the urogenital folds to completely fuse in males –> leaving a urethral opening on the base of the penis
what happens if you remove the limb field
no development of the limb
when is the natural period of herniation
around week 6-8
what causes cleft lip and cleft palate
failure of the neural crest cells to completely migrate forwards and fuse and the midline of the face
components of the pronephros
neprostomes and pronephric duct
what do the somatic and splanchnic mesoderm become
somatic - muscle and CT
splanchnic - structures associated with viscera
which somitomere is the first to become independent as a somite, and where anatomically is it located
somitomere 8, at the neck
what causes defects in the outflow tracts of the heart
failure of migration of the neural crest cells
which tissues does the paraxial mesoderm give rise to
- dermis of skin
- axial skeleton
- axial and limb muscles
splitting of the mesoderm..
- paraxial mesoderm - medial to the notochord
- lateral mesoderm - most lateral to notochord
- intermediate mesoderm - in between paraxial and lateral
arterial supplies of the foregut, midgut and hindgut
foregut - ciliac artery
midgut - superior mesenteric artery
hindgut - inferior mesenteric artery
what does the trophoblast form
some extraembryonic structs (part of the placenta)
the dermomyotome splits again into
dermatome and myotome
what allows the gut to undergo rotation when undergoing rapid growth
the yolk stalk
function of the notochord
to induce overlying ectoderm to form the neural plate (organises tissue around it)
what is the second most common birth defect
hypospadias (misplaced urethral opening in boys)
how are the finger and toe digits sculptured
apoptosis kills the cells in the bands between the presumptive fingers
what causes diplopodia
when the ectodermal ridge is damaged –> loss of control of growth
at what time in development does the gut retract back into the body cavity
by week 9
what does the somites do
splits into sclerotome and dermomyotome
failure to retract the gut back into the body cavity is called what
omphalocele
migration of the hypoblast
moves circularly around the blastocoele and encompasses the yolk sac
at what stage in development is major organogenesis complete?
by 3 months (end of the first trimester)
what does the ectoderm give rise to
nervous system and epidermis
folding of neural plate
folds around neural groove to form the neural tube
what is the anatomy of the limb field
central free limb field and peripheral tissue
what is the neural plate
patch of endoderm that is fated to become your nervous system
how are the body axes determined
- AP determined by the first cleavage of the zygote
- D-V determined by the position of the inner cell mass in the blastocyst
- L and R set along the longitudinal axis by the signals distributed by the cilia on the primitive node that swirls current from R to L
