Đang chuẩn bị liên kết để tải về tài liệu:
Ebook Textbook of clinical embryology: Part 2

(BQ) Part 2 book "Textbook of clinical embryology" presents the following contents: Digestive tract, major digestive glands and spleen, development of oral cavity, respiratory system, body cavities and diaphragm, development of heart, development of blood vessels, development of urinary system,. | 13 Digestive Tract Overview The digestive tract gastrointestinal tract develops from primitive gut that is derived from the dorsal part of endodermal yolk sac. The primitive gut forms during the fourth week of intrauterine life by the incorporation of a larger portion of the yolk sac umbilical vesicle into the embryonic disc during craniocaudal and lateral folding of embryo Fig. 13.1 . The tubular primitive gut extends in the median plane from buccopharyngeal membrane at its cranial end to cloacal membrane at its caudal end. It freely communicates with the remaining yolk sac by the vitellointestinal duct. The part of gut cranial to this communication is called foregut part caudal to this communication is called hindgut and part intervening between foregut and hindgut is called midgut Fig. 13.1 . The cranial end of foregut is separated from the stomo-deum by buccopharyngeal membrane while caudal end of hindgut is separated from the proctodeum by cloacal membrane. At later stage of development buccopharyngeal and cloacal membranes rupture and gut communicates to exterior at its both ends. The endoderm of primitive gut forms the endothelial lining of all parts of the gastrointestinal tract except part of mouth and distal part of anal canal that are derived from ectoderm of stomodeum and proctodeum respectively. The muscular connective tissues and other layers of wall of the digestive tract are derived from splanch-nopleuric mesoderm surrounding the primitive gut Fig. 13.2 . While the primitive gut is being formed the midline artery dorsal aorta gives off a series of ventral branches to the gut. Those in the region of midgut run right up to the yolk sac and are therefore termed vitelline arteries. Later most of these ventral branches of dorsal aorta disappear and only three of them remain one of foregut the celiac artery one of midgut the superior mesenteric artery and one of hindgut the inferior mesenteric artery Fig. 13.3 . The development of digestive .