Flashcards in Embryology Deck (45):
What does a blastocyst consist of?
The Embryoblast splits into which two layers?
What does the trophoblast split into? And at what stage does this happen?
In week to when in invades the endometrium
What are the two cavities formed in week 2?
What happens to the syncytiotrophoblast in week 2?
It becomes vascularised in maternal blood
At what stage is the embryo known as en bilaminar embryonic disc?
Where does the primitive streak form from and in which week?
Week three from the Epiblast
What is gastrulation? When does this occur?
It's the formation of the three germ layers from the Epiblast
What are the three layers that the Epiblast forms?
Where does the notochord form from and when?
Week 3 from the mesoderm
What is derived from the ectoderm?
Epidermis of skin
Brain, spinal cord, peripheral nerves and nervous tissue
What is derived from the mesoderm?
Muscle, tendons and ligaments
Vessels and blood
What is derived from the endoderm?
Epithelial of organ systems
What cells are in the primitive node?
What are the three main steps of gastrulation?
First, cells proliferate and begin to migrate and displace the hypoblast layer, this forms the endoderm
Secondly, cells migrate and settle above endoderm to form the mesoderm
Remaining Epiblast cells form the ectoderm
What is neurulation and when does it happen?
Transformation of neural plate into neural tube week 3 + 4
What is the notochord?
A column of midline cells vital for induction of neural plate, motor region of the brain and spinal cord and vertebral formation.
At the end of week four when neural tube closure is complete, what are the 3 primary brain vesicles that are formed?
How is the mesoderm split up?
Paraxial mesoderm (somites-form tissues of back)
When is the umbilical cord formed?
Around 5 weeks
What are the four factors that affect placental transfer
Maternal-placental blood flow
Concentration or electrochemical gradient
Presence of transporters
What are the two main types of transport across the placenta?
Passive diffusion (simple or facilitated)
Active transport (enzymatic reaction or pinocytosis)
What are neural crest cells?
Cells that are pinched off during the formation of the neural tube
They migrate to diff locations
The lateral plate of the mesoderm forms......
The intermediate mesoderm forms.....
It's the formation of the neural tube (cns)
Neural crest cells also created and pinched off
A thickening of the ectoderm folds and closes
Notochord is needed to induce the formation
Neural crest cells can develop into......
Pia and arachnoid mater
Dorsal root ganglion
What happens in week four?
Lateral and longitudinal folding
Beginning of organogenesis
Formation of limb buds
Describe brain formation
It's the dilation, thickening and folding of the neural tube
The central canal widens to form the ventricles
The brain then forms around the ventricles
How is the liver formed?
Liver bud forms from endoderm gut tube and grows into septum transversum
Endoderm forms hepatocytes
Mesoderm forms blood vessels
Connection with duodenum narrows forming the bile duct
Which arteries supply the diff parts of the gut?
Forgut- celiac artery
Midgut- superior mesenteric
Hindgut- inferior mesenteric
Describe the development of the pancreas
It develops from dorsal and ventral buds of the Forgut
Dorsal buds grow largest
Dorsal and ventral buds fuse after midgut rotation
How is the heart formed?
Wk 3- blood islands form in mesoderm
Vasculogenic endothelial growth factor- angiogenesis
Wk 4- 2 heart tubes form from lateral mesoderm
They unite and dilate forming atria and ventricles
Heart tubes fold upwards
R. Sinus venosum forms SVC
L. Sinus venosum forms IVC
Wk 8- neural crest cells form spiral valve which splits bulbus cordis into pulmonary trunk and aorta
What is cardiac looping?
The process where the heart tube folds to create typical heart shape and location
What is the ductus venosus?
A channel that bypasses the liver
It regulates blood flow from placenta to IVC
What is the ductus arteriosus?
Ductus that connects pulmonary artery to aorta so most blood coming fro might ventricle can bypass the lungs which are non functional
What is atrial septation?
It involves the growth of two overlying septa to create an opening with a valve
The opening is the foramen ovale
Heart septation is done by week 8
What happens at birth to the ductus venosus?
The cord is clamped stopping blood flow from placenta
The ductus venosus becomes the ligamentum venosum
What happens to the foramen ovale at birth?
Increased blood flow from lungs causes more pressure in left atrium
The pressure change closes the flap forming the fossa ovale
What happens to the ductus arteriosus after birth?
Bradykinin is secreted by the lungs and causes it to close
It then becomes the ligamentum arteriosum
The two dorsal aorta have how many arches coming off them?
Pair three of the aortic arches form......
Pair 4 of the aortic arches form........
Aorta and subclavian artery
What does pair 6 of the aortic arches form?
The pulmonary arteries and ductus arteriosus