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Basic Embryology
n/a
44
Anatomy
Undergraduate 3
08/27/2012

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Term
What is embryology?
Definition
the study of the development of single individual
Term
What is the prenatal period? What periods does it consist of?
Definition
"before birth"
-embryonic
-fetal
Term
What is the embryonic period?
Definition
first 8 weeks
-orgnas form from three embryonic germ tissues; emergence of the basic body plan.
Term
What is the fetal period?
Definition
Remaining 30-32 weeks
-tissues/organs grow in size and complexity
Term
What is week 1 of the embryonic period?
Definition
zygote to blastocyst:
-Zygote moves toward the uterus; fertilization in lateral third of uterine tube
-Blastomeres- daughter cells formed from zygote
-Morula- cluster of 16-32 blastomeres
-Blastocyst- fluid filled structure, about 60 cells
Term
What makes up a blastocyst?
Definition
inner cell mass- cluster of cells (future fetus)
Trophoblast- outer layer (contributes to placenta)
Term
Week 2 of the Embryonic period?
Definition
Bilaminar Embryonic disk, inner cell mass divided into two sheets.
Amniotic sac
yolk sac
Term
What are the two sheets of the Bilaminar disc?
Definition
1. Epiblast and Hypo blast
Term
What is the Amniotic Sac?
Definition
formed by an extension of epiblast
-forms the amnion and amniotic sac cavity that is filled with amniotic fluid
Term
What forms the yolk sac?
Definition
formed by an extension of hypoblast.
Term
Is the yolk significant to humans? What is formed by the yolk sac?
Definition
no. A small portion of the digestive tube forms from part of yolk sac.
Term
What do tissues around yolk sac give rise to?
Definition
earliest cells and blood vessels
Term
Week 3 of the Embryonic Period Includes:
Definition
The three-layered embryo.
-Primitve Streak
-Notochord
-Neurulation
-Mesoderm Begins to differentiate
Term
What is the primitive streak?
Definition
raised grooves on the dorsal surface of the epiblast; gastrulation is a process of invagination of epiblast cells
Term
What does the primitive streak produce?
Definition
3 layers of cells which will form all tissues in the body.
Term
What are the 3 layers of cells?
Definition
Endoderm- formed from migrating cells that replace the hypoblast
Mesoderm- formed between epiblast and endoderm
Ectoderm- formed from epiblast cells that stay on dorsal surface.
Term
What is the notochord formed from?
Definition
Primitive node- a swelling at one end of primitive streak; cells that mvoe through node become notochord
Term
What does the Notochord define?
Definition
Body axis- acts as a scaffold for the furture vertebral column.
-one of the first structures to form.
Term
What is neurulation?
Definition
ectoderm starts forming brain and spinal cord.
Term
Ectoderm in the dorsal midline thickens to create:
Definition
neural plate
Term
Ectoderm folds inward to create:
Definition
neural groove
Term
A hollow tube pinches off into the body to form:
Definition
Neural Tube
Term
Cranial part of the neural tube becomes:
Definition
the brain
Term
What is the neural crest?
Definition
cells adjacent to neural plate; pulled along with the neural tube. Forms sensory nerve cells, ganglia, and melanocytes.
Term
What happens as the mesoderm begins to differentiate?
Definition
somites- our first body segments (from paraxial mesoderm, adjacent to notochord)
intermediate mesoderm begins as a continuous strip of tissue just lateral to paraxial mesoderm.
Lateral Plate (mesoderm)- most lateral part of mesoderm splits into 2 halves.
Term
What becomes the serous body cavities?
Definition
coelom
Term
What is apposed to the ectoderm?
Definition
somatic mesoderm
Term
What is apposed to the endoderm?
Definition
Splanchnic mesoderm
Term
What happens in week 4 of the embryonic period?
Definition
The body takes shape.
-folding of embryo laterally and at the head and tail forms the primitive gut.
Term
At day 24 what is the shape?
Definition
tadpole
Term
What derives from the ectoderm in week 4?
Definition
ectoderm- forms brain, spinal cord, and epidermis
Term
What derives from the endoderm?
Definition
Forms inner epithelial lining of the gut tube and respiratory tubes, digestive organs, including liver and pancreas and urinary bladder.
Term
What does the notochord give rise to in week 4?
Definition
nucleus pulposus within intervertebral discs
Term
What does the mesoderm give rise to in week 4?
Definition
forms muscle bone dermis and connective tissues
Term
What does the Somites give rise to in week 4?
Definition
divide into sclerotome (vertebrae) dermatomme (dermis of dorsal body) and myotome (trubk and limb muscles)
Term
What does the intermediate mesoderm give rise to in week 4?
Definition
forms kidneys and gonads
Term
What does the Lateral Mesoderm give rise to in week 4?
Definition
-splanchnic mesoderm and somatic mesoderm
Term
splanchnic mesoderm forms:
Definition
musculature, connective tissues, and serosa of the digestive and respiratory structures. Forms heart and most blood vessels
Term
Somatic mesoderm forms:
Definition
dermis of skin, bones and ligaments
Term
During weeks 5-8 what happens?
Definition
limb buds form
embryo first looks recognizably hums
head is disproportionately large
all major organs are in place
Term
Rapid growth and maturation occurs in:
Definition
the fetal period
Term
During the first half of the fetal period cells are:
Definition
differentiating
Term
Normal births occur # weeks after conception?
Definition
38-40 weeks
Term
A premature birth is one that occurs before:
Definition
38 weeks
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