![]() The alimentary canal wall contains two important intrinsic nerve plexuses- the submucosal nerve plexus and the myenteric nerve plexus, both of which are networks of nerve fibers that are actually part of the autonomic nervous system and help regulate the mobility and secretory activity of the GI tract organs.ĭifferent regions of the stomach have been named, and they include the following: The serosa is the outermost layer of the wall that consists of a single layer of flat serous fluid-producing cells, the visceral peritoneum. The muscularis externa is a muscle layer typically made up of an inner circular layer and an outer longitudinal layer of smooth muscle cells. The submucosa is found just beneath the mucosa it is a soft connective tissue layer containing blood vessels, nerve endings, lymph nodules, and lymphatic vessels. The mucosa is the innermost layer, a moist membrane that lines the cavity, or lumen, of the organ it consists primarily of a surface epithelium, plus a small amount of connective tissue ( lamina propria) and a scanty smooth muscle layer. The walls of the alimentary canal organs from the esophagus to the large intestine are made up of the same four basic tissue layers or tunics. About 25 cm (10 inches) long, it is essentially a passageway that conducts food by peristalsis to the stomach. The esophagus or gullet, runs from the pharynx through the diaphragm to the stomach. The laryngopharynx is continuous with the esophagus below both of which are common passageways for food, fluids, and air. The oropharynx is posterior to the oral cavity. The lingual tonsils cover the base of the tongue just beyond.įrom the mouth, food passes posteriorly into the oropharynx and laryngopharynx. At the posterior end of the oral cavity are paired masses of lymphatic tissue, the palatine tonsils. The lingual frenulum, a fold of mucous membrane, secures the tongue to the floor of the mouth and limits its posterior movements. The muscular tongue occupies the floor of the mouth and has several bony attachments- two of these are to the hyoid bone and the styloid processes of the skull. The area contained by the teeth is the oral cavity proper. The space between the lips and the cheeks externally and the teeth and gums internally is the vestibule. ![]() The uvula is a fleshy finger-like projection of the soft palate, which extends inferiorly from the posterior edge of the soft palate. The hard palate forms its anterior roof, and the soft palate forms its posterior roof. The lips (labia) protect its anterior opening. ![]() Its organs include the following: Mouthįood enters the digestive tract through the mouth, or oral cavity, a mucous membrane-lined cavity. The alimentary canal, also called the gastrointestinal tract, is a continuous, hollow muscular tube that winds through the ventral body cavity and is open at both ends. The organs of the digestive system can be separated into two main groups: those forming the alimentary canal and the accessory digestive organs. Defecation is the elimination of indigestible residues from the GI tract via the anus in the form of feces. Transport of digested end products from the lumen of the GI tract to the blood or lymph is absorption, and for absorption to happen, the digested foods must first enter the mucosal cells by active or passive transport processes. The sequence of steps in which the large food molecules are broken down into their building blocks by enzymes is called chemical digestion. ![]() Mechanical digestion prepares food for further degradation by enzymes by physically fragmenting the foods into smaller pieces, and examples of mechanical digestion are: mixing of food in the mouth by the tongue, churning of food in the stomach, and segmentation in the small intestine. If foods are to be processed by more than one digestive organ, they must be propelled from one organ to the next swallowing is one example of food movement that depends largely on the propulsive process called peristalsis (involuntary, alternating waves of contraction and relaxation of the muscles in the organ wall). Food must be placed into the mouth before it can be acted on this is an active, voluntary process called ingestion. The functions of the digestive system are: Practice Quiz: Digestive System Anatomy and Physiology.Activities Occurring in the Mouth, Pharynx, and Esophagus.
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