embryology Flashcards
What becomes of the mesoderm?
Divides into Paraxial mesoderm–>intermediate mesoderm–>lateral plate (splachnic and somatic) and separately the notochord
Forms:
Somite- Muscle , vertebrae and ribs, dermis
Intermediate mesoderm- kidneys and gonads
Lateral plate- somatic [parietal serosa, dermis of ventral organs, CT of limbs], splanchnic [viseral serosa, gi and respiratory wall]
notochord- nucleus of pulposus of intervertebral discs
lateral plate- somatic (connective tissue, dermis of ventral body region, parietal serosa) and splanchnic mesoderm (wall of digective tract, respiratory tract except the epithelial tract, heart, BV, viseral serous)
during which week does the body take shape?
week 4
What does the epiblast give rise to ?
Amnion outer membrane and amniotic sac cavity by the inner membrane
Name the developmental features at 12 weeks
Liver and head are still dominant
Blood cell formation begins in bone marrow, liver and spleen
Sex of fetus can be determined
what the major embryological events?
organs form from the three primary germ tissues and emergence of the basic body plan
Pair the following to its respective layer:
A. dermis of the ventral body region
B. pigment cells
C. visceral serosa
D. Hair
E. dermis of the dorsal body region
F. Joints
G. sclerotoma
A. Somatic mesoderm (lateral mesoderm)
B. Ectoderm
C. Splanchnic mesoderm (lateral mesoderm)
D. Ectoderm
E. Somite
F. Somatic mesoderm (lateral mesoderm)
G. Somite (vertebrae and ribs)
Name the prenatal periods and time frame
Embryonic period – first 8 weeks
Fetal period – remaining 30 weeks
How and when does implantation occur?
After the blastocyst has been released, the trophoblast differentiate and invade the wall the of the endometrium around day 7
How is the neural tube made?
By neurulation.
Via induction (ability of cells to influence developmental direction of other cells) of the mesoderm cells, the midial sagital portion dorsal to the primitive streak thickens on the ectoderm to form the neural plate. As it folds inward, a neural groove is formed. The neural folds approach each other, fuse and pinch off to form the neural tube. The cranial portion becomes the brain.
What are the somatic mesoderm and splanchnic mesoderm? Where do they come from? What do they become?
The are formed by the division of the lateral plate.
paraxial mesoderm–>intermedite mesoderm–>lateral plate–> divides into the somatic and splanchnic mesoderm and form the coelom (serous body cavities)
Somatic mesoderm- parietal mesoderm of the coelom that meshes with the ectoderm
Splanchnic mesoderm- viseral mesoderm of the coelom that meshes with the endoderm
Where do the early blood cells and blood vessels come from?
tissues around the yolk sac
When is the fetus propotional? what else happens during this period?
At month 4
sucking motions of lips occur
Which of the following are paired correctly:
A. Gonads arise from the intermediate mesoderm
B. Muscles, ribs and bones arise from the somite
C. dermis of the ventral body region arise from the somatic mesoderm
D. epithelial lining of digestive and respiratory tracts arise from the splanchnic mesoderm
E. epithelial lining of digestive and respiratory tracts arise from the endoderm
F. Sclerotoma, dermatoma and Myotoma arise from you somite
A, C, E,F
B. bones arise from somatic mesoderm of the lateral plate (bones are connective tissues)
D. Wall of the digestive and respiratory tracts arise from the splanchnic mesoderm not their epithelial lining
What does the endoderm form?
Inner epithelial lining of the gut tube
Respiratory tubes, digestive organs, and urinary bladder
and Notochord – gives rise to nucleus pulposus within intervertebral discs
When is the fetus most susceptible to teratogens?
morphological abnormalities from week 3-7 and mostly physiological defects from week 8 and on
highest mortality during weeks 1-2
What becomes of the ectoderm?
This top layer undergoes neurulation starts to form the:
CNS - brain and spinal cord and epidermis(hair, nails and glands of skin)
neural crest becomes the PNS, BV of the head and neck, pigment cells and portions of the skeleton.
What is considered normal and premature birth?
normal at 37 weeks and premature before that
where are each germ layers and how are they formed?
Endoderm: formed from migrating cells that replace the hypoblast layer
Mesoderm: formed btw the epiblast and endoderm
ectoderm- formed from the epiblast cells that remain on the dorsal surface
The last 4 weeks of the embryonic development is important because….
limb buds form and all major organs are in place,
at week 8 the embyro finally looks like a human
**the Head is disproportionately large **
where does conception occur?
in the lateral third of the unterine tube
Define somites and explain what gives rise to them?
Somites are our first body segments like muscles and dermis that come from the paraxial mesoderm.
What are the distinct features of a fetus at week 8?
Large head and liver.
Bone formation has begun
Limbs are complete and fingers and toes are no longer webbed
cardiovascular system is fully functional
what is a blastocyst and how is it formed?
Blastocyst (fluid filled structure) made during day 5. What has been formed is an outer cell mass (the trophoblast), consisting of many flat cells and the morula forms a inner cell mass at the embryonic pole making that space for the blastocyst cavity
day 6- it frees itself from the pellucid zone aka the “first birth”
How is the PNS formed?
From the neurulation of the ectoderm but specifically from the neural crest made after the neural tube is made on the caudal portion of the neural plate.
- it forms the sensory nerve cells (ANS)
