Breakdown of large organic molecules into smaller molecules that can be absorbed
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Absorption
Movement of molecules out of the digestive tract and into the blood or lymphatic system
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Elimination
Removal of undigested material such as fiber from the food and other waste products from the body
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Feces
Undigested materials such as fiber from food and other waste products from the body are eliminated as
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Divisions of Digestive System
Digestive/Gastrointestinal Tract and Specific Associated Organs
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Organs of the Digestive System
Oral Cavity
Pharynx
Esophagus
Stomach
Small Intestine
Large Intestine
Anus
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Layers of the GI Tract
Mucosa
Submucosa
Muscularis
Serosa/Adventitia
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Mucosa
Innermost layer; Mucus Membrane
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Submucosa
Thick layer that contains nerves, blood vessels, and small glands
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Muscularis
Made of an inner and outer layer of smooth muscle
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Serosa
Outermost layer; made of peritoneum
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Anatomy of Oral Cavity
Lips
Cheek
Tongue
Palate
Tonsils
Teeth
Salivary Glands
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Lips
Also called labia; protects interior opening
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Cheek
Forms lateral walls of the mouth; Helps in forming words during speech
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Buccinator
Flattens cheek against teeth
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Tongue
Attached to the posterior part of the oral cavity; Functions in moving food in the mouth; Helps in speech
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Palate
Separates oral cavity and nasal cavity; Prevents food from passing into the nasal cavity during chewing and swallowing
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Parts of the Palate
Hard Palate
Soft Palate
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32
Teeth in Normal Adult
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Primary Teeth
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Major Pairs of Salivary Glands
Parotid
Submandibular
Sublingual
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Parotid Gland
Largest salivary gland
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Submandibular Gland
Produces serous secretion
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Sublingual Gland
Produces mucus secretions
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Saliva
Contains salivary amylase the breaks down starch into simple sugars
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Lysozyme
Lyses bacterial cell membrane; antimicrobial agent in food
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Mucin
A proteoglycan that gives a lubricating quality to the secretions of the salivary glands
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ANS
Salivary gland secretion is primarily regulated by the
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Pharynx
Connects mouth with esophagus
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Parts of Pharynx
Nasopharynx
Oropharynx
Laryngopharynx
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Oropharynx and Laryngopharynx
Only parts of the pharynx that carry food downs to the esophagus
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Esophagus
Extends from the pharynx to the stomach
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25cm
Length of esophagus
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Anterior, Posterior, Mediastinum
The esophagus lies ________ to the vertebrae and ______ to the trachea within the P *__________*
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Regions of Esophagus
Upper esophageal sphincter
Lower esophageal sphincter
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2/3
____ of the esophagus is made of skeletal muscle
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Phases of Deglutition
Buccal Phase
Pharyngeal Phase
Esophageal Phase
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Buccal Phase
Voluntary; Oral transit phase
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Tongue
Moves the bolus to the oropharynx
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Pharyngeal Phase
The bolus is pushed through the pharynx and into the esophagus;
Movement of the bolus stimulates receptors in the oropharynx which stimulates the soft palate and uvula to close off the nasopharynx and the epiglottis to seal off the larynx which prevents the bolus from entering the respiratory system.
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Esophageal Phase
The upper esophageal sphincter relaxes to allow the bolus to enter the esophagus and contracts to reduce backflow into the pharynx
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Peristalsis
A wave of involuntary light contractions of the circular longitudinal smooth muscles of the esophagus
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Muscularis layer:
Outer longitudinal layer
Middle circular layer
Inner oblique layer
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Stomach
Is Eolined with simple columnar epithelium
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Epithelial Cells in the Stomach
Surface Mucus Cells
Mucous Neck Cells
Parietal Cells
Endocrine Cells
Chief Cells
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Surface Mucous Cells
produces mucus that Muprotects the stomach lining
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Mucous Neck Cells
produce mucus that lubricates the epithelial cells; protects the stomach walls from the acidic chyme
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Parietal Cells
produce hydrochloric acid and intrinsic factor
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Hydrochloric Acid
keeps the stomach acidic and this pH (2.0) must be maintained to kill microorganisms and activate the enzyme, pepsin
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Intrinsic Factor
Is needed for the absorption of vitamin B12 (for DNA synthesis RBC production) from the small intestine
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Endocrine Cells
produce regulatory chemicals
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Chief Cells
produce pepsinogen (precursor of pepsin)
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Stomach Secretions from other gastric glands
o Mucus o Hydrochloric acid o Intrinsic factor o pepsin
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Chyme
Mixture of food and stomach secretions
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Bolus
Folds in the stomach when it is empty
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True
Approximately 2L of gastric secretions are produced each day
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False
When there is an decrease of gastric secretions it results to heartburn or burning sensation in the chest (caused by overconsumption of caffeine or alcohol or fatty food or when you lie down after you eat)
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Gastric Secretions
Regulated by both nervous and hormonal mechanisms
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Three phases of Gastric Secretion
cephalic phase
gastric phase
intestinal phase
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20 seconds
Movement in the stomach occurs every
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Movements in the Stomach
move chyme through the digestive tract, made by smooth muscle contractions in the stomach wall, move chyme toward the pyloric sphincter
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Types of Stomach Movement
Mixing Waves
Peristaltic Wave
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Mixing Waves
relatively weak contractions that mix food with stomach secretions to form chyme F
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False
In mixing waves, the solid part of the chyme is pushed toward the pyloric sphincter while liquid part is pushed back toward the body of the stomach
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Peristaltic Wave
stronger contractions that push the chyme toward and through the pyloric sphincter
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False
In peristaltic wave, a few milliliters of fluid chyme is forced through the pyloric sphincter into the jejunum
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True
Most of the chyme is forced back to the stomach to further mix in peristaltic wave
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Small Intestine
Approximately 3 meter long; Major site of digestion and absorption
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Parts of the Small Intestine
* Duodenum * Ileum * Jejunum
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Cell Types in the Small Intestine
Absorptive
Goblet
Granular
Endocrine
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Absorptive Cells
have microvilli and absorb digested food
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Goblet Cells
produce protective mucus
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Granular Cells
protect the epithelium against bacteria
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Endocrine Cells
produce hormones
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Modifications that increase small intestine surface area
Circular Folds
Villi
Microvilli
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Circular Folds
formed by mucosa and submucosa and do not disappear when filled with food
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Secretions of Small Intesine
Mucus
Ions
Water
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Small Intestine Secretions
lubricate and protect the intestine from the acidic chyme and action of digestive enzymes.; keep the chyme in the small intestine in a liquid form to facilitate the digestive process.
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enzymes
The epithelial cells in the walls of the small intestine have ________, bound to their free surfaces that are significant in the final steps of digestion.
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Peptidase
Protein-digesting enzyme
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Disaccharidase
Disaccharide-digesting protein
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Maltose
broken downby Disaccharidases into the monosaccharide, glucose.
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Peristaltic Contractions
proceed along the length of the intestine for variable distances and cause the chyme to move along the small intestine.
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Segmental Contractions
are propagated for only short distances and mix intestinal contents.
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Structures of the Large Intestine
Cecum
Colon
Rectum
Anal Canal
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Cecum
saclike first part of the large intestine that joins the small intestine at the ileocecal junction; 9cm tube that hangs to it which is the appendix
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Appendix
Hangs from the cecum
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Appendicitis
Accumulation of lymphatic tissue that sometimes becomes inflamed
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Colon
Approximately 1.5 to 1.8 meters long
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Parts of the Colon
Ascending
Transverse
Descending
Sigmoidal
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Anal Canal
Internal Anal Sphincter
External Anal Sphincter
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18-24
It takes _____ hours for the material to pass the large intestine
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3-5
It takes ____ hours for chyme to pass through small intestine
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Functions of the Large Intestine
Eliminates indigestible food from the body as feces
Feces formation
Defecation
Mass movement
Defecation reflex
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Defecation
Process of removing waste from the digestive tract
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Mass Movement
Several strong contractions that push the contents of the colon to the anus
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Liver
Largest internal organ of the body;
Located on the right side of the body under the diaphragm; Produces bile