|Digestion|| the mechanical and chemical|
breakdown of foods and the absorption of the
resulting nutrients by cells.
|Functions of Digestion||ingestion; mechanical digestion; chemical digestion; propulsion; absorption; defecation|
|Mechanical Digestion||Break food without altering chemical make-up.|
|Chemical Digestion||Break food into simpler compounds.|
|Salivary Glands||Secrete saliva which contain enzymes that initiate breakdown of accessory carbohydrates.|
|Liver||Produces bile, which emulsifies fat.|
|Gallbladder||Stores bile and introduces it to the small intestine.|
|Pancreas||Produces and secretes pancreatic juice,containing digestive enzymes and bicarbonate ions, into small intestines.|
|Mouth||Mechanical breakdown of food; begins chemical digestion of carbohydrates.|
|Pharynx||Connects mouth with esophagus.|
|Esophagus||Peristalsis pushes food to stomach.|
|Stomach||Secretes acid and enzymes. Mixes food with secretions to begin enzymatic digestion of proteins.|
|Small Intestine||Mixes food with bile and pancreatic juice. Final enzymatic breakdown of food molecules, main site of nutrient absorption.|
|Large Intestine||Absorbs water and electrolytes to form feces.|
|Rectum||Regulates elimination of feces.|
|Mouth|| ingestion; mechanical digestion; prepares food for|
|Tongue||Mix food particles with saliva during chewing; Move food to pharynx during swallowing. Also, helps to move food under teeth for chewing. Papillae help handle and taste food.|
|Palate||Roof of oral cavity|
|Secretions of Salivary Glands||Parotoid glands (Largest); Submandibular glands; Sublingual glands (Smallest)|
|Parotoid Glands|| (Largest), Secretion of salivary glands:|
• water, serous fluid
• rich in amylase
|Submandibular Glands|| Secretion of salivary glands:|
• Primarily serous
• some mucus
|Sublingual Glands|| (Smallest), Secretion of salivary glands: |
• primarily mucus
• thick and stringy
|Pharynx|| • A cavity posterior to the|
mouth from which the
tubular esophagus leads
to the stomach.
• Does not digest food.
• Three parts:
|Swallowing Mechanism||• soft palate and uvula raise - preventing food from|
entering the nasal cavity.
• hyoid bone and larynx elevate.
• epiglottis closes off top of trachea.
• longitudinal muscles of pharynx contract.
• inferior constrictor muscles relax and esophagus opens
• peristaltic waves push food through pharynx.
• The tongue is pressed against the soft plate, sealing off
the oral cavity from the pharynx.
|Stomach||Inferior to the diaphram, holds about 1liter or more.|
|Lining of the Stomach||Thick; Studded with gastric pits which are ends of tubular gastric pits|
|Gastric Secretions||pepsinogen, pepsin, hydrochloric acid, mucus, intrinsic factor.|
|Pepsinogen||From chief cells; inactive form of pepsin.|
|Pepsin|| From pepsinogen in presence of|
HCl; protein splitting enzyme.
|Hydrochloric Acid|| From parietal cells; needed to convert|
pepsinogen to pepsin.
|Mucus|| From goblet cells and mucous|
glands, protective to stomach wall.
|Intrinsic Factors|| From parietal cells, required for vitamin B12|
|Phases of Gastric Secretion||Cephalic Phase, Gastric Phase, Intestinal Phase|
|Cephalic Phase|| Phase of Gastric Secretion • triggered by smell, taste, sight, or thought of food|
• parasympathetic impulses trigger gastric juice secretion
|Gastric Phase|| Phase of Gastric Secretions • triggered by presence of food in stomach|
• gastrin released
• gastric juice secreted
|Intestinal Phase|| Phase of Gastric Secretion • triggered by movement of food into small intestine|
• intestinal cells release intestinal gastrin
• secretion of gastric juice
|Gastric Absorption||Some water, certain salts, certain lipid-soluble drugs, alcohol.|
|Pancreatic Juice||pancreatic amylase; pancreatic lipase; trypsin, chymotrypsin, and carboxypeptidase; nucleases; bicarbonate ions.|
|pancreatic amylase||Type of pancreatic juice; splits glycogen into disaccharides.|
|pancreatic lipase||type of pancreatic juice; breaks down triglycerides.|
|nucleases||type of pancreatic juice; digest nucleic acids.|
|bicarbonate ions||type of pancreatic juice; make pancreatic juice alkaline.|
|digest proteins||trypsin, chymotrypsin, and carboxypeptidase.|