Embryology Flashcards
What is a blastocyst
- Blastocyst comprised of outer trophoblast and inner embryoblast.
- Trophoblast becomes foetal component of placenta.
- Embryoblast splits to become bilaminar embryonic disc.
- The cells of this disc develop into the embryo proper.
What is a blastocyst compromised of
Outer trophoblast and inner embryoblast
What does a trophoblast become
Foetal component of placenta
What does a embryoblast become
Splits to become bilaminar embryonic disc
What happens to the cells of the bilaminar embryonic disc
Develop into embryo proper
What happens during the 3rd week in terms of primitive streak
Cranio caudal primitive streak forms on dorsal surface
Cells migrate into streak
Forms trilaminar disc
Ectoderm
Covers the embryo
Mesoderm
Lies between the ectoderm and the endoderm
Endoderm
Lines the gut tube
Gastrulation
3 layers arise:
-ectoderm
-mesoderm
-endoderm
What is the endoderm
Is open to the yolk sac
Fate: Linings of the gut, associated glands and lining of the lungs
What is the mesoderm
Lies between the ectoderm and the endoderm
Fate: notochord, muscles, bone and connective tissue
Somites
Paired mesodermal blocks that lie lateral to the neural tube
What is the mesoderm
Intermédiaire mesoderm- lies lateral to notochord ventral to the somites and dorsal to the lateral plane
Fate: kidneys, ureters and gonads
Lateral place mesoderm- surrounds coelom (body cavity)
Splanchnic mesoderm- visceral (inner) fate= gut wall
Somatic mesoderm- parietal (outer) fate=body wall
Fate: heart, blood vessels, gut musculature and lining of body cavities
What is the surface ectoderm
Covers the embryo. Continous with the amnion
Fate: epidermis of skin (hair, nails, and skin glands)
Neural crest
Dorso lateral to neural tube
Fate: PNS, ganglia, structures in head and neck
Neural tube
Fate:CNS
Neuroectoderm
Neural tube and neural crest tissue derived from neuroctoderm
Neural crest tissue is unique to vertebrates
Notochord
Cranio caudal stiffening rod that is characteristic of chordates
Fate: nucleus pulposus of IV discs during infancy
When is the neural plate formed
At 18 days ectoderm starts to thicken to from the neural plate
When should the neural tube fuse
By the end of the 4th week
Forebrain
Optic cups, cerebral hemispheres, olfactory bulb and tract, hypothalamus and thalamus
Midbrain
Remains undivided
Hindbrain
Cerebellum, medulla and pons
Formation of neural crest
-fusion starts in the middle of the tube
-neural crest cells might into mesoderm
-somites form from mesoderm
-ventral part= vertebrae
-dorsal part=skin/skeletal muscle
Gut folding around transverse axis description
-foregut and hind gut are formed by cephalocaudal folding
-this is due to differential growth
-foregut and hind gut commence as blind tubes that terminate at the buccopharyngeal and cloacal membranes
-midgut open to yolk sac
Development of the diaphragm
-lungs and bronchi develop as out pocketing of forgut
-therefore their lining is derived from ectoderm
-spectrum transversal folded inwards
Development of the lungs
-diverticulum formed in the endoderm at the future site of the glottis
-splits in two: primary bronchi
-divides again: secondary bronchi etc
-endoderm gives rise to: mucosa, alveolar epithelium
What does the mesoderm give rise to during the development of lungs
-bronchai and tracheal cartilages
-bronchai and tracheal muscles
-pulmonary vasculature
-visceral pleurae
Division of the coelom
-the future pericardial and peritoneal cavities are separated by the septum transversum
-the future pleural and peritoneal cavities communicate via (the pericardio- peritoneal) canals
-pleuro-pericardial folds separate the pericardial and pleural cavities and contain phrenic nerves
-lung buds invade the mesoderm of the wall
What is the Diaphragm formed from
-septum transversum centrally
-pleuroperioneal folds dorso laterally
-the oesophageal mesentery dorso medically
-body wall
