Early Embryology Simple Summary Essay

2279 Words Jun 1st, 2011 10 Pages
Embryology
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
Ovulation

* 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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