T5-Embryonic folding Flashcards
In longitudinal folding, ________ and ________end loop ventrally
cranial; caudal
Amniotic cavity pinches the_______ to create the ______
yolk sac; gut tube
Order of structures at day 21 (head fold; pre-fold)
developing heart is caudal to the septum transversum
Order of structures at day 26 (head fold; post-fold)
developing heart is cranial to the septum transversum
During longitudinal head folding, the ____________is folded into primative __________ tube with___________ membrane
local endoderm; foregut; oropharyngyeal
Direction of brain growth with longitudinal (head) folding
dorsally , cranially, ventrally
Direction of caudal emminence growth with longitudinal (tail) folding
dorsally, caudally, wraps ventrally
Location of primative streak pre-tail fold
cranial to cloacal membrane
Location of primative streak post-tail fold
caudal to cloacal membrane
Tail folding brings the ___________ ventrally
connecting stalk
During longitudinal tail-folding local endoderm is folded into ___________tube with ____________
primative hindgut; cloacal membrane
Transverse folding Lateral edges of ____________ loop _______ and eventually go towards the ___________ of the developing embryo
amniotic cavity; ventrally; center
Results of transverse folding
foregut and hind gut are folded into complete circles; midgut is not, and instead remains open to umbillical vessicle
In transverse folding local endoderm is folded into what?
primative midgut
What is the primative midgut connected to?
the remains of the secondary umbillical vessicle by the yolk stalk
At which directions is the gut tube a complete circle
cranially and caudally to the yolk stalk
Which day is this?
Day 21
Which day is this?
day 26
Which day is this?
day 21
Which day is this?
day 26
Which day is this
Day 17
Which day is this
day 19
3 fates of the mesoderm
Paraxial mesoderm, intermediate mesoderm, lateral plate mesoderm
Paraxial mesoderm
somites form in a craniocaudal direction as paired blocks of cells, flanking the notochord and neural tube
Intermediate mesoderm
contributes to the formation of the urinary and reproductive systems
Lateral Plate Mesoderm
Divided by intraembryonic coelom into intraembryonic somatic mesoderm and intraembryonic splanchnic mesoderm
What will somites develop into
vertebrae
- intervertebral discs
- ribs
- skeletal muscles of body walls and limbs
- connective tissue of body wall
Intraembryonic somatic mesoderm
supporting ectoderm
-contributes to connective tissue, blood vessels, and smooth muscle of body wall and limbs
Intraembryonic splanchnic mesoderm
supporting endoderm, contributes to smooth muscles, blood vessels and connective tissue of GIT and associated organs
Somatopleure
somatic mesoderm+ectoderm
splanchnopleure
Splanchnic mesoderm+ endoderm
Fate of ectoderm
neuroectoderm and surface ectoderm
Fate of endoderm
- epithelial lining of gastrointestinal tract
- the secretory epithelial cells of liver, gall bladder and pancreas
- epithelial lining of the respiratory system
Methoods of estimation of embryonic age
Mesurement of length and counting of somites
What is Greatest length (GL) used for
very early embryo’s prior to folding
Common gynaecological clinical practice for measuring embryos
crown-rump length (CRL)
Carnegie Embryonic Staging System
a 23 stage international system that enables comparisons based on intra and extra-embryonic development
