Power Point Lecture Slides prepared by Vince Austin

Power. Point® Lecture Slides prepared by Vince Austin, University of Kentucky The Digestive System Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings 23

Digestive System: Overview § The alimentary canal or gastrointestinal (GI) tract digests and absorbs food § Alimentary canal – mouth, pharynx, esophagus, stomach, small intestine, and large intestine § Accessory digestive organs – teeth, tongue, gallbladder, salivary glands, liver, and pancreas Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Digestive System: Overview Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Digestive Process The GI tract is a “disassembly” line: § Nutrients become more available to the body in each step There are six essential activities: § 1) Ingestion, 2) propulsion, and 3) mechanical digestion § 4) Chemical digestion, 5) absorption, and 6) defecation Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Digestive Process Figure 23. 2 Copyright © 2004 Pearson Education, Inc. , publishing as

Gastrointestinal Tract Activities § 1) Ingestion – taking food into the digestive tract § 2) Propulsion – swallowing and peristalsis § Peristalsis – waves of contraction and relaxation of muscles in the organ walls § 3) Mechanical digestion – chewing, mixing, and churning food Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Peristalsis and Segmentation Esophagus Intestine Figure 23. 3 Copyright © 2004 Pearson Education, Inc.

Gastrointestinal Tract Activities § 4) Chemical digestion – catabolic breakdown of food § 5) Absorption – movement of nutrients from the GI tract to the blood or lymph § 6) Defecation – elimination of indigestible and unabsorbed solid wastes Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Peritoneum and Peritoneal Cavity Peritoneum – serous membrane of the abdominal cavity § Visceral peritoneum – covers external surface of most digestive organs § Parietal peritoneum – lines the body wall Peritoneal cavity § Lubricates digestive organs § Allows them to slide across one another Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Figure 23. 5 a Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin

Mesentery – double layer of peritoneum that provides: § Vascular and nerve supplies to the viscera § A means to hold digestive organs in place and store fat Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Blood Supply: Splanchnic Circulation Arteries and the organs they serve include: § The hepatic, splenic, and left gastric: spleen, liver, and stomach § Inferior mesenteric and superior mesenteric: small and large intestines Hepatic portal circulation: § Collects nutrient-rich venous blood from the digestive viscera § Delivers this blood to the liver for metabolic processing and storage Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Histology of the Alimentary Canal From esophagus to the anal canal the walls of the GI tract have the same four tunics. From the lumen outward they are the: § 1. mucosa § 2. submucosa § 3. muscularis externa § 4. serosa § Each tunic has a predominant tissue type and a specific digestive function Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Histology of the Alimentary Canal Copyright © 2004 Pearson Education, Inc. , publishing as

1. Mucosa Innermost moist epithelial layer that lines the lumen of the alimentary canal § Consists of three layers: a lining epithelium, lamina propria, and muscularis mucosae Its three major functions are: § Secretion of mucus § Absorption of the end products of digestion § Protection against infectious disease Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Lining epithelium § Consists of simple columnar epithelium and mucus-secreting goblet cells The mucus secretions: § Protect digestive organs from digesting themselves § Ease food along the tract Stomach and small intestine mucosa contain: § Enzyme-secreting cells Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Lamina propria § Loose areolar and reticular connective tissue § Nourishes the epithelium and absorbs nutrients Muscularis mucosae § smooth muscle cells that produce local movements of mucosa Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

2. Submucosa – dense connective tissue containing elastic fibers, blood and lymphatic vessels, lymph nodes, and nerves 3. Muscularis externa – responsible for segmentation and peristalsis 4. Serosa – the protective visceral peritoneum § Replaced by the fibrous adventitia in the esophagus Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Mouth Oral or buccal cavity: § Is bounded by lips, cheeks, palate, and tongue § Has the oral orifice as its anterior opening § Is continuous with the oropharynx posteriorly To withstand abrasions: § The mouth is lined with stratified squamous epithelium § The gums, hard palate, and dorsum of the tongue are slightly keratinized Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Mouth 1. cheeks 2. lips (labia), labial frenulum (attach to gums) 3. hard palate - anterior part of roof of mouth (palatine bones) 4. soft palate - posterior of roof of mouth (mucous membrane) 5. uvula - hanging portion of soft palate (punching bag) 6. palatoglossal arch & palatopharyngeal arch a. palatine tonsils between arches Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Anatomy of the Oral Cavity: Mouth Figure 23. 7 a Copyright © 2004 Pearson

Oral Cavity and Pharynx: Anterior View Figure 23. 7 b Copyright © 2004 Pearson

Tongue Functions include: § Gripping and repositioning food during chewing § Mixing food with saliva and forming the bolus § Initiation of swallowing, and speech Note: Lingual frenulum secures the tongue to the floor of the mouth Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Tongue Superior surface bears three types of papillae: § Filiform – give the tongue roughness and provide friction § Fungiform – scattered widely over the tongue and give it a reddish hue § Circumvallate – V-shaped row in back of tongue Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Tongue Figure 23. 8 Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin

Salivary Glands § Parotid – lies anterior to the ear between the masseter muscle and skin § Parotid duct – opens into the vestibule next to the second upper molar § Submandibular – lies along the medial aspect of the mandibular body § Sublingual – lies anterior to the submandibular gland under the tongue Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Salivary Glands Figure 23. 9 a Copyright © 2004 Pearson Education, Inc. , publishing

Permanent Teeth Figure 23. 10. 2 Copyright © 2004 Pearson Education, Inc. , publishing

Classification of Teeth are classified according to their shape and function: § Incisors – chisel-shaped teeth adapted for cutting or nipping § Canines – conical or fanglike teeth that tear or pierce § Premolars (bicuspids) and molars – have broad crowns with rounded tips and are best suited for grinding or crushing § During chewing, upper and lower molars lock together generating crushing force Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Tooth Structure a. crown - above the level of the gums b. root - one to three projections into socket c. neck - between crown and root on gumline d. dentin - hard shell of tooth e. pulp cavity - center of tooth f. pulp - lymph, blood, nerve, connective tissue g. root canal - passage through roots to the pulp i. apical foramen - opening at the base h. enamel - covers the dentin on the crown i. cementum - covers dentin on the root Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Tooth Structure Figure 23. 11 Copyright © 2004 Pearson Education, Inc. , publishing as

Esophagus § Muscular tube going from the laryngopharynx to the stomach § Travels through the mediastinum and pierces the diaphragm § Joins the stomach at the cardiac orifice Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Stomach - Chemical breakdown of proteins begins and food is converted to chyme § Cardiac region – surrounds the cardiac orifice § Fundus – dome-shaped region beneath the diaphragm § Body – midportion of the stomach § Pyloric region – made up of the antrum and canal which terminates at the pylorus - The pylorus is continuous with the duodenum through the pyloric sphincter Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Stomach § Greater curvature – entire extent of the convex lateral surface § Lesser curvature – concave medial surface § Lesser omentum – runs from the liver to the lesser curvature § Greater omentum – drapes inferiorly from the greater curvature to the small intestine § Rugae - folds in the inner lining of the stomach Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Stomach Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 23.

Stomach § Blood supply – celiac trunk, and corresponding veins (part of the hepatic

Microscopic Anatomy of the Stomach Epithelial lining is composed of: § Goblet cells that produce a coat of alkaline mucus - The mucous surface layer traps a bicarbonate-rich fluid beneath it § Gastric pits contain gastric glands that secrete gastric juice, mucus, and gastrin Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Microscopic Anatomy of the Stomach Figure 23. 15 Copyright © 2004 Pearson Education, Inc.

Gastric glands of the fundus and body have a variety of secretory cells § Mucous neck cells – secrete acid mucus § Parietal cells – secrete HCl Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Small Intestine: Gross Anatomy § Runs from pyloric sphincter to the ileocecal valve § The bile duct and main pancreatic duct join the duodenum at the hepatopancreatic ampulla § The ileum joins the large intestine at the ileocecal valve Has three subdivisions: 1. duodenum 2. jejunum 3. ileum Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Small Intestine: Microscopic Anatomy Structural modifications of the small intestine wall increase surface area: § Villi – fingerlike extensions of the mucosa § Microvilli – tiny projections of absorptive mucosal cells’ plasma membranes Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Small Intestine: Microscopic Anatomy Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin

Small Intestine: Histology The epithelium of the mucosa is made up of: § Absorptive cells and goblet cells § Cells of intestinal crypts secrete intestinal juice § Peyer’s patches are found in the submucosa and are collections of lymphatic/wbc tissue § Brunner’s glands in the duodenum secrete alkaline mucus Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Pancreas - structure posterior to great curvature of the stomach 1. head - enlarged portion in C-curve of the duodenum 2. body - tapers off beneath the stomach 3. tail - terminal part near the end 4. pancreatic duct - merges with bile duct to duodenum a. hepatopancreatic ampulla (merging of both) 5. accessory duct - empties into duodenum, smaller Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Pancreas - histology 1. made of glandular epithelial cells 2. pancreatic islets (of Langerhans) (1% of all cells) a. hormones: glucagon, insulin, somatostatin 3. acini - (99% of the cells in pancreas) a. mixture of enzymes called "pancreatic juice" Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Liver § Superficially has four lobes – right, left, caudate, and quadrate § The

Liver: Associated Structures The falciform ligament: § Separates the right and left lobes anteriorly § Suspends the liver from the diaphragm and anterior abdominal wall The ligamentum teres: § Is a remnant of the fetal umbilical vein § Runs along the free edge of the falciform ligament Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Liver: Associated Structures § The lesser omentum anchors the liver to the stomach § The hepatic blood vessels enter the liver at the porta hepatis § gallbladder - rests in a recess on the inferior surface of the right lobe; stores bile for digestion of fats Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Bile leaves the liver via: § Bile ducts, which fuse into the common hepatic duct § The common hepatic duct, which fuses with the cystic duct § These two ducts form the bile duct Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Gallbladder and Associated Ducts Figure 23. 20 Copyright © 2004 Pearson Education, Inc. ,

Liver: Microscopic Anatomy lobules are hexagonal shaped and the structural and functional units of the liver § Composed of hepatocyte (liver cell) plates radiating outward from a central vein § Portal triads are found at each of the six corners of each liver lobule portal triads consist of a bile duct and § Hepatic artery – supplies oxygen-rich blood to the liver § Hepatic portal vein – carries venous blood with nutrients from digestive viscera Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Microscopic Anatomy of the Liver Figure 23. 24 c, d Copyright © 2004 Pearson

§ Liver sinusoids – enlarged, leaky capillaries located between hepatic plates § Kupffer cells – hepatic macrophages found in liver sinusoids Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Hepatocytes Hepatocyte functions include: § Production of bile § Processing bloodborne nutrients § Storage of fat-soluble vitamins § Detoxification Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

The Gallbladder § Thin-walled, green muscular sac on the ventral surface of the liver § Stores and concentrates bile by absorbing its water and ions § Releases bile via the cystic duct, which flows into the bile duct Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Large Intestine § Is subdivided into the cecum, appendix, colon, rectum, and anal canal § The saclike cecum: § Lies below the ileocecal valve in the right iliac fossa § Contains a wormlike vermiform appendix Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Colon Has distinct regions: § ascending colon § hepatic flexure § transverse colon § splenic flexure § descending colon § sigmoid colon Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Large Intestine Figure 23. 29 a Copyright © 2004 Pearson Education, Inc. , publishing

Colon § The transverse and sigmoid portions are anchored via mesenteries called mesocolons § The sigmoid colon joins the rectum § The anal canal, the last segment of the large intestine, opens to the exterior at the anus Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings