Essentials of Human Anatomy & Physiology PDF

Essentials of Human Anatomy & Physiology Seventh Edition Elaine N. Marieb Chapter 14 The Digestive System and Body Metabolism Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings ...

Essentials of Human Anatomy & Physiology Seventh Edition Elaine N. Marieb Chapter 14 The Digestive System and Body Metabolism Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  The Digestive System and Body Metabolism ∙ Digestion ∙Breakdown of ingested food ∙ Absorption ∙ Passage of nutrients into the blood ∙ Metabolism ∙ Production of cellular energy (ATP) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.1  Organs of the Digestive System ∙ Two main groups ∙ Alimentary canal – continuous coiled hollow tube ∙ Accessory digestive organs Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Organs of the Digestive System Figure 14.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Organs of the Alimentary Canal ∙ Mouth ∙ Pharynx ∙ Esophagus ∙ Stomach ∙ Small intestine ∙ Large intestine ∙ Anus Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.3  Mouth (Oral Cavity) Anatomy ∙ Lips (labia) – protect the anterior opening ∙ Cheeks – form the lateral walls ∙ Hard palate – forms the anterior roof ∙ Soft palate – forms the posterior roof ∙ Uvula – fleshy projection of the Figure 14.2a soft palate Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.4  Mouth (Oral Cavity) Anatomy ∙ Vestibule – space between lips externally and teeth and gums internally ∙ Oral cavity – area contained by the teeth ∙ Tongue – attached at hyoid and styloid processes of the skull, and by the lingual frenulum Figure 14.2a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.5  Mouth (Oral Cavity) Anatomy ∙ Tonsils ∙ Palatine tonsils ∙ Lingual tonsil Figure 14.2a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.6  Processes of the Mouth ∙ Mastication (chewing) of food ∙ Mixing masticated food with saliva ∙ Initiation of swallowing by the tongue ∙ Allowing for the sense of taste Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.7  Pharynx Anatomy ∙ Nasopharynx – not part of the digestive system ∙ Oropharynx – posterior to oral cavity ∙ Laryngopharynx – below the oropharynx and connected to the esophagus Figure 14.2a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.8  Pharynx Function ∙ Serves as a passageway for air and food ∙ Food is propelled to the esophagus by two muscle layers ∙ Longitudinal inner layer ∙ Circular outer layer ∙ Food movement is by alternating contractions of the muscle layers (peristalsis) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 14.9  Esophagus ∙ Runs from pharynx to stomach through the diaphragm ∙ Conducts food by peristalsis (slow rhythmic squeezing) ∙ Passageway for food only (respiratory system branches off after the pharynx) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Layers of Alimentary Canal Organs ∙ Mucosa ∙ Innermost layer ∙ Moist membrane ∙ Surface epithelium ∙ Small amount of connective tissue (lamina propria) ∙ Small smooth muscle layer Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Layers of Alimentary Canal Organs ∙ Submucosa ∙ Just beneath the mucosa ∙ Soft connective tissue with blood vessels, nerve endings, and lymphatics Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Layers of Alimentary Canal Organs ∙ Muscularis externa – smooth muscle ∙ Inner circular layer ∙ Outer longitudinal layer ∙ Serosa ∙ Outermost layer – visceral peritoneum ∙ Layer of serous fluid-producing cells Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Layers of Alimentary Canal Organs Figure 14.3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Stomach Anatomy ∙ Located on the left side of the abdominal cavity ∙ Food enters at the cardioesophageal sphincter Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Stomach Anatomy ∙ Regions of the stomach ∙ Cardiac region – near the heart ∙ Fundus ∙ Body ∙ Phylorus – funnel-shaped terminal end ∙ Food empties into the small intestine at the pyloric sphincter Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Stomach Anatomy ∙ Rugae – internal folds of the mucosa ∙ External regions ∙ Lesser curvature ∙ Greater curvature Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Stomach Anatomy ∙ Layers of peritoneum attached to the stomach ∙ Lesser omentum – attaches the liver to the lesser curvature ∙ Greater omentum – attaches the greater curvature to the posterior body wall ∙ Contains fat to insulate, cushion, and protect abdominal organs Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Stomach Anatomy Figure 14.4a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Stomach Functions ∙ Acts as a storage tank for food ∙ Site of food breakdown ∙ Chemical breakdown of protein begins ∙ Delivers chyme (processed food) to the small intestine Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Specialized Mucosa of the Stomach ∙ Simple columnar epithelium ∙ Mucous neck cells – produce a sticky alkaline mucus ∙ Gastric glands – secrete gastric juice ∙ Chief cells – produce protein-digesting enzymes (pepsinogens) ∙ Parietal cells – produce hydrochloric acid ∙ Endocrine cells – produce gastrin Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Structure of the Stomach Mucosa ∙ Gastric pits formed by folded mucosa ∙ Glands and specialized cells are in the gastric gland region Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Structure of the Stomach Mucosa Figure 14.4b, c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Small Intestine ∙ The body’s major digestive organ ∙ Site of nutrient absorption into the blood ∙ Muscular tube extending form the pyloric sphincter to the ileocecal valve ∙ Suspended from the posterior abdominal wall by the mesentery Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Subdivisions of the Small Intestine “Dogs Just Itch! ∙ 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 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Chemical Digestion in the Small Intestine ∙ Source of enzymes that are mixed with chyme ∙Intestinal cells ∙Pancreas ∙ Bile enters from the gall bladder Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Chemical Digestion in the Small Intestine Figure 14.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Villi of the Small Intestine ∙ Fingerlike structures formed by the mucosa ∙ Give the small intestine more surface area Figure 14.7a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Microvilli of the Small Intestine ∙ Small projections of the plasma membrane ∙ Found on absorptive cells Figure 14.7c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Structures Involved in Absorption of Nutrients ∙ Absorptive cells ∙ Blood capillaries ∙ Lacteals (specialized lymphatic capillaries) Figure 14.7b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Folds of the Small Intestine ∙ Called circular folds or plicae circulares ∙ Deep folds of the mucosa and submucosa ∙ Do not disappear when filled with food ∙ The submucosa has Peyer’s patches (collections of lymphatic tissue) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Digestion in the Small Intestine ∙ Enzymes from the brush border ∙ Break double sugars into simple sugars ∙ Complete some protein digestion ∙ Pancreatic enzymes play the major digestive function ∙ Help complete digestion of starch (pancreatic amylase) ∙ Carry out about half of all protein digestion (trypsin, etc.) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Digestion in the Small Intestine ∙ Pancreatic enzymes play the major digestive function (continued) ∙ Responsible for fat digestion (lipase) ∙ Digest nucleic acids (nucleases) ∙ Alkaline content neutralizes acidic chyme Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Absorption in the Small Intestine ∙ Water is absorbed along the length of the small intestine ∙ End products of digestion ∙ Most substances are absorbed by active transport through cell membranes ∙ Lipids are absorbed by diffusion ∙ Substances are transported to the liver by the hepatic portal vein or lymph Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Propulsion in the Small Intestine ∙ Peristalsis is the major means of moving food ∙ Segmental movements ∙ Mix chyme with digestive juices ∙ Aid in propelling food Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Large Intestine ∙ Larger in diameter, but shorter than the small intestine ∙ Frames the internal abdomen Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Large Intestine Figure 14.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Functions of the Large Intestine ∙ Absorption of water ∙ Eliminates indigestible food from the body as feces ∙ Does not participate in digestion of food ∙ Goblet cells produce mucus to act as a lubricant Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Structures of the Large Intestine ∙ Cecum – saclike first part of the large intestine ∙ Appendix ∙Accumulation of lymphatic tissue that sometimes becomes inflamed (appendicitis) ∙Hangs from the cecum Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Structures of the Large Intestine ∙ Colon ∙ Ascending ∙ Transverse ∙ Descending ∙ S-shaped sigmoidal ∙ Rectum ∙ Anus – external body opening Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Structures of the Large Intestine ∙ Colon ∙ Ascending ∙ Transverse ∙ Descending ∙ S-shaped sigmoidal ∙ Rectum ∙ Anus – external body opening Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Food Breakdown and Absorption in the Large Intestine ∙ No digestive enzymes are produced ∙ Resident bacteria digest remaining nutrients ∙ Produce some vitamin K and B ∙ Release gases ∙ Water and vitamins K and B are absorbed ∙ Remaining materials are eliminated via feces Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Propulsion in the Large Intestine ∙ Sluggish peristalsis ∙ Mass movements ∙ Slow, powerful movements ∙ Occur three to four times per day ∙ Presence of feces in the rectum causes a defecation reflex ∙ Internal anal sphincter is relaxed ∙ Defecation occurs with relaxation of the voluntary (external) anal sphincter Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Accessory Digestive Organs ∙ Salivary glands ∙ Teeth ∙ Pancreas ∙ Liver ∙ Gall bladder Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Salivary Glands ∙ Saliva-producing glands ∙ Parotid glands – located anterior to ears ∙ Submandibular glands ∙ Sublingual glands Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Saliva ∙ Mixture of mucus and serous fluids ∙ Helps to form a food bolus ∙ Contains salivary amylase to begin starch digestion ∙ Dissolves chemicals so they can be tasted Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Teeth ∙ The role is to masticate (chew) food ∙ Humans have two sets of teeth ∙ Deciduous (baby or milk) teeth ∙ 20 teeth are fully formed by age two Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Teeth ∙ Permanent teeth ∙ Replace deciduous teeth beginning between the ages of 6 to 12 ∙ A full set is 32 teeth, but some people do not have wisdom teeth Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Classification of Teeth ∙ Incisors ∙ Canines ∙ Premolars ∙ Molars Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Classification of Teeth Figure 14.9 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Regions of a Tooth ∙ Crown – exposed part ∙ Outer enamel ∙ Dentin ∙ Pulp cavity ∙ Neck ∙ Region in contact with the gum ∙ Connects crown to root Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.10 Slide  Regions of a Tooth ∙ Root ∙ Periodontal membrane attached to the bone ∙ Root canal carrying blood vessels and nerves Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14.10 Slide  Pancreas ∙ Produces a wide spectrum of digestive enzymes that break down all categories of food ∙ Enzymes are secreted into the duodenum ∙ Alkaline fluid introduced with enzymes neutralizes acidic chyme ∙ Endocrine products of pancreas ∙ Insulin ∙ Glucagons Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Liver ∙ Largest gland in the body ∙ Located on the right side of the body under the diaphragm ∙ Consists of four lobes suspended from the diaphragm and abdominal wall by the falciform ligament ∙ Connected to the gall bladder via the common hepatic duct Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Bile ∙ Produced by cells in the liver ∙ Composition ∙ Bile salts ∙ Bile pigment (mostly bilirubin from the breakdown of hemoglobin) ∙ Cholesterol ∙ Phospholipids ∙ Electrolytes Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Role of the Liver in Metabolism ∙ Several roles in digestion ∙ Detoxifies drugs and alcohol ∙ Degrades hormones ∙ Produce cholesterol, blood proteins (albumin and clotting proteins) ∙ Plays a central role in metabolism Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  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 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Processes of the Digestive System ∙ Ingestion – getting food into the mouth ∙ Propulsion – moving foods from one region of the digestive system to another Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Processes of the Digestive System ∙ Peristalsis – alternating waves of contraction ∙ Segmentation – moving materials back and forth to aid in mixing Figure 14.12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Processes of the Digestive System ∙ Mechanical digestion ∙ Mixing of food in the mouth by the tongue ∙ Churning of food in the stomach ∙ Segmentation in the small intestine Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Processes of the Digestive System ∙ Chemical Digestion ∙ Enzymes break down food molecules into their building blocks ∙ Each major food group uses different enzymes ∙ Carbohydrates are broken to simple sugars ∙ Proteins are broken to amino acids ∙ Fats are broken to fatty acids and alcohols Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Processes of the Digestive System ∙ Absorption ∙ End products of digestion are absorbed in the blood or lymph ∙ Food must enter mucosal cells and then into blood or lymph capillaries ∙ Defecation ∙ Elimination of indigestible substances as feces Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Processes of the Digestive System Figure 14.11 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Control of Digestive Activity ∙ Mostly controlled by reflexes via the parasympathetic division ∙ Chemical and mechanical receptors are located in organ walls that trigger reflexes Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Control of Digestive Activity ∙ Stimuli include: ∙ Stretch of the organ ∙ pH of the contents ∙ Presence of breakdown products ∙ Reflexes include: ∙ Activation or inhibition of glandular secretions ∙ Smooth muscle activity Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Nutrition - Take a Class! ∙ Nutrient – substance used by the body for growth, maintenance, and repair ∙ Categories of nutrients ∙ Carbohydrates: simple sugars, starches, fiber ∙ Lipids: triglycerides, phospholipids, fatty acids ∙ Proteins: amino acids ∙ Vitamins Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Body Energy Balance ∙ Energy intake = total energy output (heat + work + energy storage) ∙ Energy intake is liberated during food oxidation ∙ Energy output ∙ Heat is usually about 60% ∙ Storage energy is in the form of fat or glycogen Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide