Early Embryology Simple Summary Essay

2279 Words Jun 1st, 2011 10 Pages
Week 1
Ovarian cycle:
GnRH from hypothalamus FSH and LH from pituitary cyclic changes in the ovary.
Follicular phase: * 15-20 preantral follicles start to grow due to FSH * 1 reaches full maturity released * Others undrgo atresia * Estrogens are released which; 1. Proliferate endometrium 2. Thin the cervical mucus 3. Stimulate pituitary to release LH * The LH; 1. Elevate concentrations of maturation promoting factor (oocytes complete meiosis one and begin meiosis II, stopped at metaphase) 2. Stimulate progesterone production by follicular stromal cells (luteinisation) 3. Cause follicular rupture

* High concentration of LH makes the collagenase
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Most form axial skeleton, others disappear. * Also forms neural crest ( which will later give components to the pharyngeal arches) * Somites segment into dermatome (epidermis and hyperdermis), myotome (skeletal muscle) and sclerotome (axial skeleton). * The lateral mesoderm seperates into the splanchnic mesoderm ( forming Git along with endoderm) and somatic mesoderm (forms muscle). * Lateral mesoderm also gives the laryngeal cartilages. * Between these layers is a cavity which will later differentiate into the pericardial, pleural and peritoneal cavity * Intermediate mesoderm connects the lateral and paraxial * Blood vessels form here. * Paraxial and lateral plate mesoderm develop the flat bones of skull and all voluntary muscles of the facial region. Endoderm: * GIT mainly – foregut, midgut (which for a while communicates with yolk sac via vitelline duct)and hind gut * Buccopharyngeal membrane ruptures in the 4th week * Cloacal membrane breaks down in the 7th week * Forms the

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