EMBRYO Flashcards
What is the first step in gastrulation?
Formation of the primative streak and primative node
Where is the primative node located?
at the cranial end of the streak
What is at the center of the primative node?
primative pit
What forms the primative streak?
thickening of the epiblast cells
When do cells fall through the primative streak?
days 2-3 or third week
What is the 1st layer of epiblast cells that move through the primative streak?
endoderm
What group of cells does not enter the primative streak?
ectoderm
What group of epiblast is second through the primative streak?
mesoderm
What is formed by the endoderm, ectoderm, and mesoderm?
trilaminar disk
What marks the end of gastrulation?
The primitive streak receeds caudallyCells in node migrate cranially
What is formed by the cells that move cranially at the end of gastrulation?
notocord
When do most newborn tertatomas develope?
around week 3
What is the 4th major tissue that is derived at the end of gastrulation?
notocord
What is derived from the pharyngeal arch of mesoderm?
most skeletal muscle of the headaortic arches
What is derived from the cardiac mesoderm?
cardiovascular structures
What is derived from the laterally migrating mesoderm?
paraxial mesodermintermediate mesodermlateral plate mesoderm
What day do mesodermal cells begin migrating?
day 16
When does laterally migrating mesoderm split into 3 distict regions?
day 20
What is derived from the paraxial (somite) mesoderm?
makes caudal block of somites that give rise to musculoskeletal system and dermis
Where is paraxial (somite) mesoderm located?
immediately lateral to the notcord
What does the intermediate mesoderm give rise to?
urogenital system
What happens to lateral plate mesoderm ~d18-20?
Forms vesicles to form intraembryonic coelum
What does the intraembryonic coelum give rise to?
body cavities, pleural, pericardial, and parietal spaces
What gives rise to the visceral and parietal mesoderm?
intraembryonic coelum
T or F: parietal mesoderm fuses with endoderm?
False - it fuses with the ectoderm
What comes of the parietal mesoderm?
Skeleton of limbsParietal layers of serous membranes
What comes of the visceral mesoderm?
smooth muscle walls of the gut tubevisceral layer of serous membranes cardiac muscle of heart tube
What three broad categories of tissue are derivatives of mesoderm?
musculoskeletal, cardiovascular, and genitourinary
What comes of the musculoskeletal mesoderm?
muscle (smooth, cardiac, skeletal)CTBone and cartilage
What comes of the cardiovascular mesoderm?
Blood, lymph, CV tissuesspeel
What comes of the genitourinary mesoderm?
Adrenal cortexKidney uretergonads and genital tractsdura materall serous membranes
What the the endoderm generally give rise to?
Epithelial lining of the GI tract, Lower respiratory system, Genitourinary system, pharyngeal pouchesParenchyma of liver, pancreas, submandibular and sublingual glands, follicles of the thyroid gland
What germ cell line gives rise to the greatest mass of tissues?
mesoderm
What are the only muscles not derived from the mesoderm?
2 smooth muscles of the eyeconstrictor pupillae and dilator
Where do the constrictor pupillae and dilator derive from?
Somite, lateral plate, pharyngeal, or cardiac mesoderm
What part of the genitourinary system is not developed from the intermediate mesoderm?
lower part of the vagina
What part of the adrenal gland is derived from the mesoderm?
adrenal cortex
What is the adrenal medulla derived from?
neural crest cells (of ectoderm)
T or F: Endodermal cells give rise to most tissues that form GI secreting glands
TRUE
What two GI secreting glands are not derived from endoderm?
spleen (mesoderm)Parotid salivary gland (ectoderm)
What part of the thyroid gland is derived from mesoderm?
C cell - secrete calcitonin
What part of the thyroid gland is derived from endoderm?
Follicular cells thyroxine
What are the three subsets of ectoderm?
General, neuroectoderm, neural crest
What are the 3 tissues that the neural crest cells work to compose?
Nervous system, head, heart
When does neurulation occur?
latter half of w3 to w5
What initiates neurulation?
presence of notocord
Where is the neural plate formed?
on the midline of the dorsal axis of the embryo
What type of cells make up the neural plate?
neuroectodermal cells
What happens if the notocord doesn’t develope?
neurulation wont take place
What happens to the neural plate at the end of w3?
it migrates to make the neural groove
What type of cells develope from the lateral margin of the neural groove?
neural crest cells
the entire nervous system is derived from what type of tissues?
neural crest cells and neuroectoderm
What is formed by the dorsal folding of the neural groove?
the neural tube
Where does the fusion of the neural groove first occur and in what direction does it proceed?
starts in middle and proceeds cranially and caudally
T or F: the ends of the notocord are left open and ectoderm grows over the openings to cover the dorsal surface
TRUE
What closes first the cranial or caudal neopore?
cranial
What flows through the neopores before they are closed?
amniotic fluid
What are the 3 primary vesicles of the brain?
Forebrain, Midbrain, Hindbrain
What are the 3 secondary vesicles of the brain?
telencephalon, diencephalon (forebrain)Mesencephalon (midbrain)Metencephlon, mylencephlon (hindbrain)
What does the telencephalon give rise to?
Cerebral hemisphersbasal ganglialateral ventricles
What does the diencephalon give rise to?
thalmus, hypothalamus, epithalmus, subthalmus, retina, and optic n. 3rd ventricle
what does the mesencephalon give rise to?
midbraincerebral aquaduct
What does the metencephalon give rise to?
ponscerebellum4th ventricle
What does the mylencephalon give rise to?
Medulla
when do most neural tube defects manifest themselves?
day 22 to day 28 when neural tube is closing
What causes a great deal of neural tube defects?
lack of folic acid in diet
What is anecephaly?
failure of the cranial end of the neuropore to close
How can anencephaly be distinguished from spina bifida early on?
a fetus with anencephaly with have polyhyramnios
What test indicates a neural tube defect?
Elevated AFP (alpha fetal protein)
Besides NTDs what causes elevated AFP?
any defect in body closure
What causes spina bifida?
failure of the vertebral arch to form
Characterize spina bifida occulta
no NTDno inc. AFTNo clinical symptoms
