Flashcards in Embryology Deck (54)
During development which part of the gut tube has both dorsal and ventral mesentery?
How does the pancreas develop within the mesentery?
Tail in dorsal mesentery
Head in ventral mesentery
When does lateral folding of the embryo occur during development?
What name is given to the identical ball of cells formed before the blastocyst?
What are the 2 cell layers in a blastocyst?
Trophoblast and Embryoblast
When does implantation occur?
When does the amniotic cavity form?
What is the Syncitiotrophoblast?
Multinucleated cell, multiple cells fused together, surrounds embryo
Secretes enzymes to aid invasion of the endometrium by the forming embryo
When does the primary yolk sac form?
What does the extraembryonic mesoderm consist of?
Cells, extracellular matrix, cavities (coelom)
What is formed by cavitation of extraembryonic mesoderm?
Chorionic cavity, fluid filled
At day 13, what structure is present which will form the future umbilicus?
Connecting stalk, made from extraembryonic mesoderm
At day 13, what cell laters form the bilayer disc?
Epiblast and hypoblast
When is the first time to notice that the menstrual period is late?
What are the primitive streak and node?
Raised areas of ectoderm, significant cell division
Streak extends from cloaca to primitive node
What are primitive groove and pit?
Indentations of ectoderm in centre of streak and node
At day 15, what primitive forms of the mouth and anus are present?
Prochordal plate - mouth
Cloacal membrane - anus
What is Gastrulation?
Formation of 3 germ cell layers
Migration of epiblast cells from primitive streak towards hypoblast
During Gastrulation, which parts of the embryonic disc remain mesoderm free?
Buccopharyngeal and cloacal membranes
What does ectoderm develop into?
Skin and neural tissue
What does endoderm develop into?
Lining of gut tube, respiratory system and urinary system
What does mesoderm develop into?
Paraxial - somite (skeleton, muscle, dermis of skin)
Intermediate - genitourinary
Lateral plate - serous membranes
Muscle, bone, connective tissue, organs, body cavity linings (peritoneum)
What are somites?
Somites form axial skeleton, associated muscle & dermis of skin Appear sequentially between days 20 – 30
30-35 pairs formed by paraxial mesoderm
Each supplied by single spinal nerve and migrate to form parts of body
Explains dermatomal sensory mapping of the skin - migrate towards the anterior midline and pull spinal nerves with them
Which cavity is drawn around the disc during folding?
What is reversal?
Longitudinal folding moves heart, brain, mouth & anus to adult position
At what point are tissues of the folding disc folded and reflected?
What forms the dilated terminal portion of the gut tube?
What does the urorectal septum separate?
Cloaca is separated into the bladder and rectum
What is the name of the point where the cloacal membrane meets the septum?