Embryology II Flashcards
Early CV system: development of primitive heart:
Before 3rd week first blood cells arise in yolk sac and spaces in mesoderm > gaps in endothelial cells along with mesoderm spaces
By 3 weeks there is a system of paired blood vessels > swellings of these vessels merge together to form primitive heart
Early CV system: how does embryo initially receive O2?
Diffusion from nearby maternal blood
First heart beat?
21-22 days
Development of the heart: first blood flow
Occurs inferiorly to superiorly
Development of the heart: heart tubes bend creating three areas:
Bulbous cordis (superior)
Ventricle
Atrium (inferior)
Development of the heart: continued folding results in:
Atrium moved superiorly towards BC dividing in to two parts
Ventricle moves inferiorly deciding in to two parts
BC becomes truncheon arteriosis then aorta
Development of the heart: what are the ‘cushions’
Thickening so between atria and ventricles that separate them allowing unidirectional bood flow. Eventually become the valves
Development of the heart: Umbilical vein
Return from placenta and empty in to inferior vena cava via ductus venosis
Development of the heart: Umbilical artery
Extends from internal iliac artery through the umbilical cord to placenta
Development of the heart: Ductus venosis
S a vascular shunt from umbilical vein to inferior vena cava
Development of the heart: foraman ovale
Hole in the atrial septum allowing blood flow directly between atria
Development of the heart: ductus arteriosis
Vascular shunt from pulmonary trunk to aorta bypassing pulmonary circulation
Respiratory development WEEK 4
- Laryngotrachial diverticum arises from foregut
- lung bud arises from laryngotrachial tube
- bronchial buds lengthen and become primary bronchi
- RHS = 3 secondary bronchi
- LHS = 2 secondary bronchi
Repiratory system WEEK 5
- Secondary bronchial buds continue to generate successive branches
- surrounding mesoderm will become surrounding CT, cartilage, muscles, blood, lymphatic system
GI Tract development
- Wk 4 primordial gut (foregut, midgut, hindgut) forms from endoderm folding as it creates endoderm tube
- surrounding mesoderm will create muscles and CT tissue of GI tract
Forgut develops in to:
Pharynx Esophagus Lower respiratory tract Stomach Duodenum Liver and bilary apparatus Pancreas
Midgut develops in to:
Duodenum Jejunum and ilium Appendix Ascending colon First part of transverse colon
Hindgut develops in to
Remaining transverse colon Descending colon Sigmoid colon Rectum Anal canal
Renal system development:
(Wk 3)Development of epithelial cords > mesonephric tubules (which empty in to mesonephric ducts) > mesonephric ducts form ureteric bud > develops in to ureters and kidneys.
Reproductive system: gonads
Sex is determined at conception by presence of Y chrom
Reproductive system: genital ducts
Mesonephric ducts become part of reproductive system
Paramesonephric ducts develop alongside
Reproductive system: external genitalia
Mesoderm forms genital eminence near cloaca which becomes genital tubercle, genital folds flank genital tubercle and urogenital sinus
Differentiation of genital tract occurs when:
Testes produce MIH and testosterone:
Mesonephric stimulated under presence of testosterone
Para mesonephric ducts are suppressed by MIH
Skeletal system:
Cartilage preform skeleton is developed from mesoderm, some ossification occurring
Limb development
4th week: limb buds are present
8th week: regions are distinct and fingers/toes are developed
Integumentary system development:
Out of single layer of epidermal cells have connected with a loose dermis tissue by end of 8th week
