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MSU BIO216 Lecture - Week 11 Objective Assignment

MSU BIO216 Lecture - Week 11 Objective Assignment - BIOL216...

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BIOL216 Lecture Week 11 Objective Assignment Chapter 23: The Digestive System PART 1: OVERVIEW OF THE DIGESTIVE SYSTEM 1. Describe the function of the digestive system, and differentiate between organs of the alimentary canal and accessory digestive organs. Function: The main function of the digestive system is to break down the food we eat into smaller parts so the body can use them for energy and cell nourishment. The organs of the digestive system can be separated into two main groups: those forming the alimentary canal (the gastrointestinal tract), and the accessory digestive organs. The alimentary canal digests and absorbs food. The accessory tract assists the alimentary tract. The alimentary canal is a continuous, coiled, hollow, muscular tube that winds through the ventral body cavity. It is open to the environment at both ends. Its organs are the mouth, pharynx, esophagus, stomach, small intestine, and large intestine. Mouth Food enters the digestive tract through the mouth. The labia (lips) protect its anterior opening, the cheeks form its lateral walls, the hard palate forms its anterior roof, and the soft palate forms its posterior roof. The space between the lips and cheeks externally and the teeth and gums internally is the vestibule. The area contained by the oral cavity is the oral cavity proper. The tongue occupies the floor of the mouth and has many bony attachments. As food enters the mouth, it is mixed with saliva and masticated (chewed). This is where the breaking down of food begins. Pharynx From the mouth, food passes posteriorly into the pharynx, which is the common path for food, fluids, and air. The pharynx is divided into three sections: the nasopharynx (air from the nose passes here), the oropharynx (food and air from the mouth passes here), and the laryngopharynx (air going to the lungs passes here).The walls of the pharynx contain two skeletal muscle layers. The cells of the inner layer run longitudinally; those of the outer layer (the constrictor muscles) run around the wall in a circular fashion. Alternating contractions of these muscle layers propels food through the pharynx into the esophagus below. This propelling mechanism is called peristalsis. Esophagus The esophagus runs from the pharynx through the diaphragm to the stomach. The esophagus conducts food to the stomach by peristalsis. Beginning with the esophagus, the walls of the GI tract have a basic pattern that reflects their common functions. Because the tissue arrangement in the alimentary canal walls is modified along its length to serve special functions, here are the basic wall functions for reference.
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BIOL216 Lecture Week 11 Objective Assignment The walls of the alimentary canal organs from the esophagus to the large intestine have four characteristic layers: 1- The mucosa is the innermost layer. Its a moist membrane that lines the cavity or lumen of the organ. It consists primarily of a surface epithelium, plus small amounts of connective tissue, and a scanty smooth muscle layer. 2- The submucosa is just beneath the mucosa. It is a soft connective tissue layer
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MSU BIO216 Lecture - Week 11 Objective Assignment - BIOL216...

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