Week 10 - Embryonic Development Flashcards
Describe day 5 of embryonic development
Hollow ball of cells
Blastocyst = outer cell layer
trophoblast eventually forms foetal placenta and inner cell mass forms the embryo
Describe day 6 of embryonic development
Implantation - orientated to uterine endometrium
- Endometrial gland enlarges
- Endometrial (decidua) = more vascularised
Describe day 8 of embryonic development
Cell mass differentiates into distinct layers
1. hypoblast - primitive endoderm
2. epiblast - primitive ectoderm - forms small cavity - aminon
Form bilaminer embryonic disc
Describe gastrulation at day 15
Bilaminer disc develops into trilaminer structure made of three primary germ layers
Migration of cells from epiblast forming primitive streak
Describe the three primary germ layers
Ectoderm - skin and nervous system
Mesoderm - Muscle and bone
Endoderm - Epithelial lining of the GI tract and organs
Describe the primitive streak
Groove on the dorsal surface of the epiblast that extends the posterior to anterior region of the bilaminer disk
Describe day 16 of embryonic development
mesodermal cells from the primitive node migrate towards head region of the embryo to hollow tube notochordal process developing into solid notochordal
Describe week 3 of embryonic development
Oropharangel membrane forms on dorsal surface of anterior region of embryo, cloacal membrane forms on dorsal surface of posterior region
Describe embryonic folding week 4
- Folding because of uneven growth rate of different embryo parts
- medial plane folding produces head and tail
- Lateral folds produce coelom and pinches off the yolk sac forming the primitive gut - foregut, midgut and hindgut
Describe the development of the respiratory system
develops from the ventral wall of the foregut and fourth and sixth pharyngeal arches
Describe the lung bud
Respiratory diverticulum appears as outgrowth of ventral wall of foregut
- early stages has opening common to foregut but the is separated by oesophagotracheal ridges - these fuse and form oesophagotracheal septum
this divides foregut into dorsal region the oesophagus and ventral region the trachea
Association between the two = larangopharynx
Describe the development of the larynx
Lining = endodermal
Muscles + Cartilage = mesodermal arising from mesenchyme of 4th and 6th pharyngeal arches
- Mesenchymal cells rapidly divide, inducing larangeal opening to change from simple split into t shaped opening
Cartilages from larangeal epithelium proliferates and temporarily blocks the lumen of deviticulum, followed by vascularisation and renalisation forming laryngeal ventricles therefore true and false vocal chords
What forms from the 4th and 6th pharyngeal arches?
Thyroid, cricoid and arytenoid cartilages
Describe the trachea and bronchi formation
Diverticulum separates from the foregut - two lateral branches to form right and left primary bronchi by week 5
- Right bronchi extends to form 3 secondary bronchi
- Left bronchi extends to form 2 secondary bronchi
Secondaries grow and extend/expand forming tertiary bronchi 10 on the right and 8 on the left forming the bronchopulmonary segments of the lung
- By 6 months bronchi have formed 17 subdivisions - 6 more postnatal
Describe type 1 and 2 alveolar cells
1 - squamous epithelial cells for gas exchange
2 - produce surfactant to reduce surface tension of alveolar fluid
