Digestive

• The major subdivisions of the digestive system are the buccal cavity, pharynx, esophagus, stomach, small and large intestines, and cloaca.
• The accessory organs include the tongue, teeth, oral glands, pancreas, liver, and gall bladder.
• The alimentary canal does not include buccal cavity and pharynx.
• Oral glands are found in the buccal cavity.
• The two types of digestion process are mechanical and chemical digestion.
• The pancreas, liver, and gall bladder are found in the peritoneum.
• Differences in the anatomy of vertebrates are correlated with nature & abundance of food.
• Gut is longer for those that require extensive enzymatic activity like carnivores compared to that with animals with readily absorbed food like hummingbirds.
• Constant food supply: herbivores

  Scattered supply: carnivores
• Longer gut, longer digestion process
• The gut develops as part of presumptive germ layer, endoderm.
• As embryo lengthens, endoderm is drawn out into tube
• Initially, the tube is more-or-less straight but soon establishes outgrowths (diverticula), which organs posterior to the stomach.
• Diverticula that rises from the gut soon becomes accessory organs.
• Identify the labeled parts.

  A) Stomach

  B) Duodenum

  C) Spleen

  D) Liver

  E) Gall Bladder

  F) Dorsal and ventral pancreatic bud from duodenum

  
• Coiling occurs when the gut gets longer.
• Mesoderm becomes the mesentery of the digestive system.
• The allantois soon becomes the liver, gall bladder, pancreas, and various ducts of these organs.
• The muscular and connective tissue associated with gut is mesodermal in origin.
• Mesentery are connective tissue that attaches the gut to the body wall.
• The three regions of embryonic digestive tract of vertebrates are the foregut, midgut, and hindgut.
• The midgut of the embryonic digestive tract contains a yolk or attached yolk sac.
• The foregut of the embryonic digestive tract includes the oral cavity, pharynx, esophagus, stomach, and small intestine.
• The hindgut of the embryonic digestive tract includes large intestine and cloaca.
• The development of the jaw in vertebrates defines what food they can eat.
• The mouth and oral cavity begins with the mouth and ends with pharynx.
• The associated organs present in the mouth & oral cavity are the tongue, teeth, and palate.
• The roof cavity is the palate.
• Oral glands are abundant in the oral cavity that empties the substance.
• Fish have a very short oral cavity, while tetrapods have longer oral cavities.
• The mammalian mouth has muscular cheeks (masticatory organ) that help with chewing and suckling milk.
• As food enters, the first part that will modify is the palate.
• The palate is the roof of the oral cavity.
• Two kinds of palate: primary and secondary.
• The primary palate includes the internal nares (choanae) and bones.
• The internal nares (choanae) lead into the oral cavity anteriorly.
• The bones of the primary palate are two kinds: medial and lateral.
• The medial bones of the primary palate include the vomer, pterygoids, and parasphenoids.
• The lateral bones of the primary palate includes palatines and ectopterygoids.
• The nasal passages are located above the secondary palate and open at the end of the oral cavity.