. Comparative embryology of the vertebrates; with 2057 drawings and photos. grouped as 380 illus. Vertebrates -- Embryology; Comparative embryology. 598 THE DIGESTIVE SYSTEM ESOPHAGUS VERTICULUM GE INTESTINE OSTflNAL GUT. MESENCI CONTRIBUTED FROM SPLANCHNIC LAYERS OF HYPOMERE Fig. 278. Diagrams showing basic features of digestive-tube development in the verte- brates. (A) The regions of the primitive gut where outgrowths (diverticula) normally occur. (B) Basic cellular features of the gut tube. (C) Contributions of the basic cellular composition to the adult structure of the digestive tract. C
. Comparative embryology of the vertebrates; with 2057 drawings and photos. grouped as 380 illus. Vertebrates -- Embryology; Comparative embryology. 598 THE DIGESTIVE SYSTEM ESOPHAGUS VERTICULUM GE INTESTINE OSTflNAL GUT. MESENCI CONTRIBUTED FROM SPLANCHNIC LAYERS OF HYPOMERE Fig. 278. Diagrams showing basic features of digestive-tube development in the verte- brates. (A) The regions of the primitive gut where outgrowths (diverticula) normally occur. (B) Basic cellular features of the gut tube. (C) Contributions of the basic cellular composition to the adult structure of the digestive tract. Consult Fig. 293 for actual structure of mucous layer in esophagus, stomach, and intestines. type, on the other hand, most of the yolk material Hes outside the confines of the primitive gut tube (fig. 217), and the midgut region of the primitive tube is open ventrally, the ventro-lateral walls of the tube being incomplete. The latter condition is found in elasmobranch fishes, reptiles, birds, and primitive mammals. In higher mammals, although yolk substance is greatly reduced, the arrangement is similar to that of the latter group. The teleost fishes repre- sent a condition somewhat intermediate between these two major groups. 2. Basic Structure of the Early Metenteron (Gut Tube) (Consult figs. 278A; 279A; 280A; 281A; and 282B.) a. Basic Regions of the Primitive Metenteron The primitive vertebrate metenteron possesses the following regions. 1) Stomodaeum. The stomodaeum lies at the anterior extremity of the gut tube, and represents an ectodermal contribution to the entodermal portion of the primitive gut. It results from an invagination of the epidermal tube directed toward the oral evagination of the foregut. The membrane, formed by the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Nelsen, Olin E. (Olin E
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