Embryology Flashcards
What is the stomodeum?
Thin barrier that will become the mouth
Most of the urogenital system is formed from what? What isn’t?
Intermediate mesoderm
Bladder and urethra
What is the issue with ectoderm taking over control of regulating limb development?
It is only one layer thick > easily damaged > damage leads to malformation
Somites split into 3 layers, what are they called?
Sclerotome (>bone of axial skeleton)
Myotome (>muscle)
Dermotone (>dermis of skin)
What is the function of the allantois in most developing mammals?
Stores nitrogenous waste
When does the small bowel move out into the body stalk and when does it retract?
Week 6-7 and week 9 respectively
What causes sinus invertus?
Cilia on the primitive node of the primitive groove don’t beat correctly sending TFs and other developmental factors a random direction (instead of right to left)
Why don’t human use their yolk sack?
All nutrients are provided the mother
Where does the urorectal septum lie?
Between the allantois and hindgut
What is the 16 cell stage called?
Morula
What is the name of the defect where the urogenital folds don’t properly fold?
Hypospadiasis
Abnormalities in which broad factors can lead to birth defects?
Genes
Metabolism - deficiency in requirement
Intrauterine environment
Chromosome
Teratogen
At what stage is all major organogenesis finished?
3 months (first trimester)
What is the name of the cavity in the blastocyst?
Blastocoele
What is amelia?
Absent limb
What is the most critical period for development of birth defects?
First month
What is derived from the intermediate mesoderm?
Urogenital system
Why are the pharyngeal arches important?
Because they go on to form a multitude of different structures in the face and cervical region therefore defects in them have a large impact
What do neural crest defects result in?
Cleft palate defects
Which opens first the stomodeum or the proctodeum?
The stomodeum (mouth one)
What is the rate of cleft palate defects?
1:1000
Which germ layer initiates limb development?
Mesoderm
What is the proctodeum?
The thin barrier that will become the anus
Fusion of what causes the penis?
Urogenital folds
What is the frequency of birth defects?
1:33 in live births
What is the rate of hypospadiasis?
1:300
What part of the blastocyst goes on to form the embryo?
Inner cell mass
How does the fertilised egg get down the fallopian tube?
Cilia action
What are the three germ layers?
Ectoderm
Mesoderm
Endoderm
What is the notochord?
Stiffened rod that runs down the midline in the developing embryo
Endoderm is always found with what?
Mesoderm
At the 20 somitomere stage, at what number do the somites start breaking off?
8, (1-7 stay attached and become the head)
What is the name of the structure that becomes the regulator of limb development?
Apical ectodermal ridge
What is the rate of limb malformations?
1:500
What is a failure of the gut to retract back into the body cavity called?
Omphalocoele
What is the name of genetic congenital hip malformation?
Acetabulum malformation
Where do neural crest cell come from?
On top of the neural tube
The superior mesenteric artery act as what for the developing gut?
Axis of rotation
When to inner cell mass splits into 2, only one part goes on to develop into the embryo, which one is that?
Epiblast
Two tubes are formed in the purse string closure of the embryo, the primitive gut and the …?
Coelom
When does the flapper valve in the atria close?
Upon taking the first breath
Will a heart defect abort a foetus in utero?
No, only become a problem after birth
Why ventricular defects occur?
The foramen present in utero doesn’t close over properly
What is the failure of the abdominal wall to seal after retraction of the gut called?
Umbilical hernia
The trophoblast of the blastocyst becomes what?
The life support system of the embryo
What are somites?
Broken off, free floating somitomeres
What is gastrulation?
The splitting of the inner cell mass into 2 then 3 layers
What does the lateral mesoderm split into?
Somatic and Splanchic mesoderm
At what day does the heart start developing?
22
How does the liver, lungs, pancreas and trachea develop off the developing GIT?
Outpocketing of endoderm that interacts with mesoderm
Splitting of the ectoderm ridge results in what?
Diplopodia
What are crest palate defects due to?
Failure of neural crest cells to migrate completely to the midline of the face
What are mesenchymal cell like?
Free moving, with associated connective tissue (opposite to epithelial cells)
What does the notochord do to the overlying ectoderm in the early embryo?
Direct it to developed into the neural plate - the precursor to the nervous system
What is the limb field?
A patch of mesoderm that goes on to develop into the limbs
What is most of the heart derived from? Be specific
Lateral splanchnic mesoderm
At what stage does the blastocyst implant in the uterine wall?
5-10 days
What is the name of the structure that the kidneys and ureters are derived from?
Mesonephros
What does the urorectal septum do?
Separates the allantois and hindgut as it travels to the cloacal membrane
What is the most common birth defect?
Heart defect 1:200
What is it called when apoptosis fails leaving fused fingers?
Syndactyly
What two germ layers make up the viscera? (be specific)
Splanchnic mesoderm
Endoderm
How are digits formed?
Apoptosis of symmetrical disc between where fingers will form
How does the foetus compensate for the small bowel growing too long?
It extends into the body stalk
What do neural crest cell become?
Peripheral nervous system tissue
Schwann cells
Melanocytes
Dentine
Facial bone, skin, muscle
What is the cloacal membrane?
Primitive seal of the anus
What is derived from endoderm?
Epithelium of gut, lung, liver, pancreas and associated organs
What is the name of the structure that undergoes cavitation at day 4?
Blastocyst
What are the most common heart defects?
Venticular defects (25%)
What organ is slowest to develop?
Brain
The embryonic mesoderm is divided into three sections, what are they called.
Paraxial (medial)
Intermediate
Lateral mesoderm
Which part of the limb field can be removed but compensated for?
The free limb patch
What are the names of the two tubes that become the heart?
Endocardial tubes
What is derived from ectoderm?
Neural tissue
Epidermis
Which germ initiates and which germ layer finishs limb development?
Mesoderm and ectoderm respectively
What does the allantois become in humans?
The bladder and urogenital tract
What is derived from mesoderm?
Kidneys
Heart
Muscle
Most bones
Blood and vessels
Connective tissue
Gonads
Dermis of skin
Urogenital tract
Wall of gut and resp tract (but not epithelium)
What does the neural plate do?
Fold to form the neural groove
Of the 3 kidney pairs that develop, only one is used for the kidneys. What is the the second pair recycled for?
The ductus deferens from the mesonephric duct
What is meromelia?
Limb defect where hand or foot is present on a shortened limb
What are somitomeres?
Swelling of paraxial mesoderm running down laterally
What is the coelom?
Hollow space around the viscera
What is derived from the lateral mesoderm?
Heart
Blood
Limb skeleton
Ventrolateral body wall
Wall of gut and resp tract
Visceral peritoneum and pleura
What brings the colon into its normal place?
Twisting of the small bowel pulls it down
What two germ layers become the body wall? (be specific)
Ectoderm
Somatic mesoderm
Which part of the developing gut remains connected to the yolk sack?
Midgut
When in embryonic development does limb development begin?
End of fourth week
What sets right-left asymmetry of (some) of the visceral?
The action of cilia in the primitive groove controlling the direction of transcription factor flow
What is sinus invertus?
Inversion of the viscera so that they are on the opposite side
