Flashcards in The third week Deck (32)
what does the third week represent in the development of the human ?
gasturlation, formation of the three layers and organs
at the end of the second week what happens to the embryonic disk ?
becomes elongated and is broader at the butt end (cephalic end)
What happens on day 15
epiblast cells begin to migrate towards the midline forming a groove
the primitive pit develops into what
What is the notochord composed of ?
mesoderm and endodermal cells
What are the four functions of the notochord ?
CNS development, development of the vertebral column, anatomic midline, and forms the nucleus pulposis
heart is outside of the body
what contributes to the longitudinal (head tail fold)
occurs along the saggital plane and is due to the rapid growth of the CNS and differential growth
What roles do the primitive streak and the primitive node play in development ?
determination of the body axes
heart is on the wrong side of the body
what induces the epiblast to proliferate and migrate towards the midline forming a groove ?
epiblast cells proliferate and migrate through the primitive streak into the space between the epiblast and the hypoblast
when cells completely display the hypoblast cells so that thehypoblast is completely repopulatioed this is defined as what ?
epiblast cells begin to occupy the space between the endoderm and the epiblast
epiblast that do NOT migrate through the streak are known as
cells from the primitive pit invaginate and create a hollow tube what is this called
floor of notochorrdal processes fuse with endoderm and form
notochordal plate detaches beginning at the cranial end to form/
where does the notochord extend from ?
prechordal plate to primitive pit
what is the neurenteric canal
connection between the amniotic cavity and the yolk sac
masses of endodermally derived tissue commonly associated with spinal cord derived from neurenteric canal where ectoderm and endoderm are closely associated
at the buccopharyngeal membrane what begins to forms in the 3rd week
at the cloacal membrane what begins to form in the 3rd week
what is the major outcome of the longitudinal fold
elongated gut tube and closure of the body cavity
complete-all organs are mirror image of normal orientation; incomplete-only a single organ is involved
caudal dysgenesis resulting from inadequate mesoderm in caudal regions (limb and urogenitcal defects)
results from persistence of the primitive streak and pluripotent cells
during the first week of the embryonic period how is the age determined
by the number of somites
after week four how is the age of the embryo expressed
crown rump length (vertex of skull to caudal tip of the trunk)