Ch 8 Digestive System Structures

Digestive System AKA alimentary canal Aliment means to nourish -ary means pertaining to Responsible for Intake & digestion of food Absorption of nutrients from digested food Elimination of solid waste products

Major Structures Oral Cavity Pharynx Esophagus Stomach Small intestine Large intestine Rectum Anus Accessory organs Liver Gallbladder pancreas

Gastrointestinal tract Divided into two sections Upper GI tract Mouth, esophagus, & stomach Lower GI tract Small intestine, large intestine, rectum, & anus Sometimes referred to as the bowels

Oral Cavity Lips aka labia Palate Hard palate -Soft palate Rugae -uvula Tongue Papillae aka taste buds

Oral Cavity Teeth Dentition refers to the natural teeth arranged in the upper (maxillary) and lower (mandibular) arches. Primary or deciduous dentition Permanent dentition Edentulous means without teeth Periodontium – bone and soft tissues that surround teeth Gingiva aka gums, specialized mucous membranes That surrounds the teeth Salivary glands secrete saliva that moistens food, begins the digestive process, and cleanses the mouth 3 pairs; parotid, sublingual, & submandibular

Pharynx Aka throat Common passageway for both respiration & digestion What structure closes off and prevents food from entering the trachea during swallowing?

Esophagus Sometimes called the gullet A collapsible tube that leads from the pharynx to the Stomach Has a ringlike muscle at the end that controls the flow between the esophagus and the stomach called the lower esophageal sphincter or cardiac sphincter.

Stomach A saclike organ made of the fundus (upper, rounded part), the body(main part), and the antrum (lower part) Has folds in the mucosa lining called Rugae. These folds have glands that make the gastric juices. The pylorus is the narrow passage that connects the stomach with the small intestine Pyloric sphincter is the muscle ring that controls the flow from the stomach to the duodenum of the small intestine.

Small Intestine Has 3 parts Duodenum, beginning Jejunum, middle Ileum, last portion Ileocecal sphincter controls the flow from the ileum of the small intestine into the cecum of the large intestine Has little hairlike or fingerlike projections called villi that line the walls. These absorb fats and fat soluble vitamins

Large Intestine Major parts; Cecum is a pouchlike structure at the beginning of the large intestine. The vermiform appendix hangs from the lower portion. Colon Ascending colon Transverse colon Descending colon Sigmoid colon Rectum is the third major division Anus is the lower opening of the digestive tract. Flow of waste controlled by two anal sphincter muscles.

Accessory Digestive Organs Liver Found in the RUQ Removes excess glucose from bloodstream & stores it as glycogen Destroys old erythrocytes Bilirubin is a pigment produced from the destruction of hemoglobin Makes & secretes bile Digestive juice that has enzymes that break down fat

Accessory Digestive Organs Gallbladder Pear shaped sac located inferior the liver Stores and concentrates bile for later use Pancreas Feather shaped organ located posterior to the stomach Has digestive and endocrine functions. We will discuss the endocrine function in a different chapter. Synthesizes and secretes pancreatic juices. These juices help the body process protein, carbs, & fats, as well as helping to neutralize stomach acids.

Digestion

Digestion The process by which foods are broken down into nutrient form the body can use. Enzymes are responsible for the chemical changes that break foods down into simpler forms of nutrients the body can use A nutrient is a substance, usually from food, that is necessary for normal functioning of the body

Metabolism All the processes involved in the body’s use of nutrients. Anabolism, the building up of body cells or substances Catabolism, the breaking down of body cells or substances

Miscellaneous Terms Mastication aka chewing Peristalsis - wavelike contractions of the smooth muscles Chyme – semifluid mass of partly digested food Emulsification – digestion of fats by pancreatic juices Feces or stools Defecation or bowel movement Flatulence, flatus, or gas Borborygmus is the rumbling noise created by the movement of gas in the intestine