. A laboratory manual and text-book of embryology. Embryology. H4 THE STUDY OF SIX AND TEN MILLIMETER PIG EMBRYOS Transverse Section through the Heart (Fig. 104.)—The section passes through the bases of the upper limb buds. Lateral to the descending aorta; are the common cardinal veins. The right common cardinal opens into the sinus venosus which in turn empties into the right atrium, its opening being guarded by the two valves of the sinus venosus. The trachea has now separated from the esophagus and lies ventral to it. Both trachea and esophagus are sur- rounded by a condensation of mesenchy
. A laboratory manual and text-book of embryology. Embryology. H4 THE STUDY OF SIX AND TEN MILLIMETER PIG EMBRYOS Transverse Section through the Heart (Fig. 104.)—The section passes through the bases of the upper limb buds. Lateral to the descending aorta; are the common cardinal veins. The right common cardinal opens into the sinus venosus which in turn empties into the right atrium, its opening being guarded by the two valves of the sinus venosus. The trachea has now separated from the esophagus and lies ventral to it. Both trachea and esophagus are sur- rounded by a condensation of mesenchyme. The myocardium of the ventricles has formed a spongy layer much thicker than that of the atrial wall. An incomplete interventricular septum leaves the ventricles in communication dorsad. The septum primum is complete in this section but higher up in the series there is an interatrial foramen (see Fig. 96). The for- amen ovale is not yet formed. Spina/ chord Notochord'.. Ant cardinal _ vein oomatopleure Olfactory Myotome Uescenc/inj aorta Pharynx Pericardial cavity Bui bus cordis Telencephalon Fig. -Transverse section through the bulbus cordis and olfactory pits of a 6 mm. pig embryo. X Transverse Section through the Lung Buds and Septum Transversum (Fig. 105).—The tips of the ventricles lying in the pericardial cavity still show in this section. Dor- sally the pericardial cavity has given place to the pleuro-peritoneal cavity. Into this cavity project ventrad the Wolffian ridges in which the posterior cardinal veins partly lie. Into the floor of the pleuro-peritoneal cavities bulge the dorsal lobes of the liver, embedded in mesen- chyma. This mesenchyma is continuous with that of the somatopleure, and forms a complete transverse septum ventrally between the liver and heart. This is the septum transversum which takes part in forming the ligaments of the liver and is the anlage of a portion of the diaphragm. Passing through the septum arc the two prox
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectembryology, bookyear1
