Essentials of Human Anatomy & PhysiologyThe Digestive System Anatomy & Physiology II Mr. Hildebrandt
Digestive System Overview• Mastication: chewing of food• Peristalsis: moving food along the alimentary canal• Digestion Function: • Breakdown of ingested food • Absorption of nutrients into blood• Metabolism: production of cellular energy (ATP)
Organs of the Alimentary Canal• Mouth• Pharynx• Esophagus• Stomach• Small intestine• Large intestine• Anus
Mouth Anatomy: Digestion begins• Hard palate – forms the anterior roof• Soft palate – forms the posterior roof• Uvula – fleshy projection of the soft palate• Tongue – attached at hyoid and skull
Pharynx Function• Passageway for air and food• Epiglottis is fold of tissue that determines the pathway• Food movement continues to esophagus via peristalsis.
Esophagus• Runs from pharynx to stomach through the diaphragm• Conducts food by peristalsis• Passageway for food only (respiratory system branches off after the pharynx)
Stomach Anatomy• Cardioesophageal sphincter and Pyloric sphincter regulate “entrance & release”• Regions of stomach: • Cardiac region – near the heart • Fundus – upper area • Body – main area • Pylorus – funnel shaped terminal end
Stomach Functions• Churns, mixes & stores food• Site of food breakdown using HCl and Pepsin• Chemical breakdown of protein begins• Delivers chyme (processed food) to the small intestine
The Small Intestine• The body’s major digestive organ• Muscular tube extends approximately 20 feet!• Held in place by the mesentery• Villi and microvilli allow nutrient absorption into the blood
Subdivisions of the Small Intestine• Duodenum: • Attached to the stomach • Curves around the head of the pancreas• Jejunum: Attaches anteriorly to the duodenum• Ileum: Extends from jejunum to large intestine
Large Intestine (Colon)• Ileocecal valve allows chyme to enter• Thicker but shorter than small intestine• Water absorption center• Rectum & Anus store and release solid waste respectively
Salivary Glands• Saliva-producing glands• Saliva breaks down starches• Three pairs exist: • Parotid glands – located anterior to ears • Submandibular glands • Sublingual glands
Teeth• The role is to masticate (chew) food• Humans have two sets of teeth • Deciduous (baby or milk) teeth • Permanent teeth - usually 32 in a set
Pancreas: dual function• Produces pancreatic fluid that breaks down all categories of food• Pancreatic fluid is secreted into the duodenum• The alkaline fluid introduced neutralizes acidic chyme• Endocrine products: • Insulin • Glucagons
Liver: largest internal organ• Liver performs over 500 functions!• Located on the right side of the body under the diaphragm• Produces Bile (fat emulsifier)• Connected to the gall bladder via the common hepatic duct
Gall Bladder• Sac found in hollow fossa of liver• Stores bile from the liver by way of the cystic duct• Bile is introduced into the duodenum in the presence of fatty food• Gallstones can cause blockages
Chemical Digestion in the SmallIntestine Figure 14.6
Hepatic Portal Circulation•Blood leavingdigestive organshas own filteringsystem• Food could be“toxic”•Blood getscleaned by liverand then dumpedinto inferior vena Figure 11.14
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