3rd Week of Development Flashcards
Gastrulation
Formation of Germ layers
Neurulation
Formation of neural tube
When does gastrulation and neurulation occurs
3rd week of development
Sequence of formation of Gastrulation
Cranio - caudal sequence.
Hypoblast cells are _____ shaped
Cuboidal
Epiblast cells are ____ shaped
Columnar
Prochordal plate are _____ cells of Hypoblast
Columnar
Prochordal plate gives rise to
Buccopharyngeal membrane
Oral cavity is derived from
Buccopharyngeal membrane
Buccopharyngeal membrane is derived from
Prochordal plate
Prochordal plate ____ end
Cranial
Primitive streak ___ end
Tail
Primitive streak is derived from
Epiblast.
When does primitive streak form
end of 2nd week or beginning of 3rd week
What indicates the start of gastrulation
Primitive streak formation.
Persistence of primitive streak causes
Sacrococcygeal teratoma
1st germ layer to be formed
Endoderm
Endoderm replaces
Hypoblast
2nd germ layer to be formed
mesoderm
Prochordal plate and cloacal membrane formed from
ecto and endoderm
3rd germ layer to develop
Ectoderm
remains of epiblast after formation of intraembryonic mesoderm gives rise to
Ectoderm
4th germ layer to be formed
NCC, secondary mesenchyme
All germ layers are derived from
Epiblast > yolk sac
Notochord formation steps
Hensen’s node - primitive pit / blastopore - Notochordal process -Formation of Notochordal plate - Notochord formation.
primitive streak - midline mesoderm forms
Notochord
Role of Notochord
Stimulates formation of Neural tube from ectoderm
Remnants of notochord
Nucleus pulposus > Apical lig of dens
Persistence of notochord -
Chordoma
Pathognomic of Chordoma
Physaliferous cell - vacuolated cytoplasm and peripheral nucleus.
Parts of intraembryonic mesoderm
Paraxial
Intermediate
Lateral mesoderm
Undivided part of lateral mesoderm
Septum Transversum
Septum transversum - location
Cranial to prochordal plate
Septum Transversum gives rise to
Diaphragm ,
Liver - Connective tissue, Kupffer cells, Sinusoids.
Fibrous pericardium.
Paraxial mesoderm gives rise to
Somites
Intermediate mesoderm gives rise to
Urogenital system
Lateral mesoderm - parts
somatic and Splanchnopleuric layer
Somatic layer of Intraembryonic lateral mesoderm gives rise to
Appendicular skeleton and somatic layer of body cavity
Splanchnopleuric layer of intraembryonic mesoderm gives rise to
Cardiac and smooth muscles and Visceral layer of body cavity.
1st pair of somites - when and where
D20 - Occipital region.
Rate of growth of somites -
3 pairs / day
after 5th week - how many somites
35
From which regions does somites disappear
Occipital and Coccygeal
Parts of Somites
Sclerotome and Dermomyotome
Sclerotome - parts
Lateral, Ventral, Dorsal.
Dorsal sclerotome - derivatives
Vertebral spine.
Lateral sclerotome - derivatives
Vertebral arch
Ventral sclerotome - Derivatives
Vertebral body
Axial skeleton is derived from -
Somites
Appendicular skeleton is derived from -
Somatic layer of Intraembryonic mesoderm
NC and NT are surrounded by
Sclerotome
Failure of fusion of Ventral sclerotome
Hemivertebra
Failure of fusion of Dorsal sclerotome
Spina bifida
Parts of dermomyotome
Dermatome and Myotome
Dermatome derivatives
Dermis of skin
Myotome derivatives
Skeletal muscles.
UL bones derived from .?
UL muscles derived from
Somatic IE mesoderm
Myotome of Somties.
tuft of hair seen in which deformity
Spina Bifida occulta.
Smooth muscle over dorsal aorta developed from
Splanchnopleuric layer of lateral mesoderm.
Smooth muscle over Pharyngeal arch arteries derived from
NCC
Smooth muscle of Iris derived from
Neuroectoderm.
Smooth muscle of sweat glands and mammary glands derived from
Surface ectoderm.
Tertiary villi is formed by
Blood vessels formed by Splanchnopleuric EEM + somatic layer of EEM + Syncytiotrophoblast + Cytotrophoblast.
Blood Vessels are derived from
Mesodermal layers.
Blood vessels formation - Sequence
EEM layer - BV then IEM layers - BV then Anastomosis.
Angioma
tumour of blood vessels - Origin - Mesodermal
Origin of Angioma
Mesodermal
Hematopoiesis upto 5th week is carried out by
Splanchnopleuric layer of EEM
From 5 th week Hematopoiesis is carried out by
Liver, Spleen, Thymus and Bone marrow.
Liver - Hematopoiesis timeline
5th week to 7th month.
Maternal component of placenta is formed by
Decidua Basalis
Fetal component of Placenta is formed by
Chorionic villi.