DIGESTIVE SYSTEM. Chapter 25

Transcription

1 DIGESTIVE SYSTEM Chapter 25

2 DIGESTIVE SYSTEM Digestive Tract Mouth Pharynx Esophagus Stomach Small intestines Large intestines Anus Accessory Organs Teeth Tongue Salivary glands Pancreas Liver Gallbladder

3 FUNCTIONS OF DIGESTIVE SYSTEM Ingestion Digestion Propulsion Secretion Absorption Excretion

4 Major Subdivisions of the Digestive Tract Oral Cavity Mouth Mechanical processing, moistening, mixing with salivary secretions Pharynx Muscular propulsion of materials into the esophagus Esophagus Transport of materials to the stomach Stomach Chemical breakdown of materials via acid and enzymes; mechanical processing through muscular contractions Small Intestine Enzymatic digestion and absorption of water, organic substrates, vitamins, and ions Large Intestine Enzymatic digestion and absorption of water, organic substrates, vitamins, and ions Accessory Organs of the Digestive System Salivary Glands Secretion of lubricating fluid containing enzymes that break down carbohydrates Liver Secretion of bile (important for lipid digestion), storage of nutrients, many other vital functions Gallbladder Storage and concentration of bile Pancreas Exocrine cells secrete buffers and digestive enzymes; endocrine cells secrete hormones Anus FIGURE 25.1 COMPONENTS OF THE DIGESTIVE SYSTEM 2015 Pearson Education, Inc.

5 Major Subdivisions of the Digestive Tract Oral Cavity Pharynx Accessory Organs of the Digestive System Salivary Glands Esophagus Liver Stomach Small Intestine Gallbladder Large Intestine Pancreas

6 Hard palate Soft palate Pharyngeal Arches Uvula Palatoglossal arch Palatopharyngeal arch Palatine tonsil Gingiva Openings of submandibular ducts FIGURE 25.5B THE ORAL CAVITY 2015 Pearson Education, Inc.

7 Hard palate Soft palate Opening of parotid duct Pharyngeal tonsil Entrance to auditory tube Uvula Palatine tonsil Palatopharyngeal arch Lingual tonsil Epiglottis Hyoid bone FIGURE 25.5A THE ORAL CAVITY 2015 Pearson Education, Inc.

8 TONGUE Muscles of the Tongue Dorsum contains papillae Papillae contain taste buds Embedded glands release lingual lipase Lingual frenulum attaches tongue to floor of mouth Tongue muscles controlled by CN XII Hypoglossal nerve

9 SALIVARY GLAND 1. Parotid 2. Submadibular 3. Sublingual Produce amylase Largest: Parotid Drains to mouth via parotid duct

10 TEETH Designed for mastication Crown: covered by enamel, consists of dentin (mineralized matrix) and pulp which is highly vascularized Neck : area of gingiva Root: consists of root canal, artery vein, and nerve Apical foramen- end of root canal Peridontal ligament

11 Deciduous Teeth Permanent Teeth

12 FIGURE 25.7C TEETH Maxillary dental arcade Hard palate Central incisors (7 8 yr) Lateral incisor (8 9 yr) Cuspid (11 12 yr) 1st Premolar (10 11 yr) 2nd Premolar (10 12 yr) 1st Molar (6 7 yr) 2nd Molar (12 13 yr) 3rd Molar (17 21 yr) Mandibular dental arcade 3rd Molar (17 21 yr) 2nd Molar (11 13 yr) 1st Molar (6 7 yr) 2nd Premolar (11 12 yr) 1st Premolar (10 12 yr) Cuspid (9 10 yr) Lateral incisor (7 8 yr) Central incisors (6 7 yr) c The normal orientation of adult teeth. The normal range of ages at eruption for each tooth is shown in parentheses.

13 THE PHARYNX Pharyngeal constrictors Push the bolus toward the esophagus Palatopharyngeus Elevates the larynx Stylopharyngeus Elevates the larynx Palatal muscles Raise the soft palate

14 Palatal Muscles Tensor veli palatini Levator veli palatini Laryngeal Elevators Stylopharyngeus Palatopharyngeus Pharyngeal Constrictors Superior pharyngeal constrictor Middle pharyngeal constrictor Inferior pharyngeal constrictor Esophagus a Lateral view

15 FIGURE 25.8 THE SWALLOWING PROCESS 1 Buccal Phase Hard palate 3 Esophageal Phase Tongue Epiglottis Larynx Soft palate Bolus Esophagus Peristalsis 2 Pharyngeal Phase Esophagus Thoracic cavity Diaphragm Stomach 2015 Pearson Education, Inc.

16 FIGURE 25.3A PERISTALSIS AND SEGMENTATION Peristalsis INITIAL STATE Longitudinal muscle Circular muscle From mouth To anus 1 Contraction of circular muscles behind bolus Contraction 2 Contraction of longitudinal muscles ahead of bolus Contraction Contraction 3 Contraction in circular muscle layer forces bolus forward a Peristalsis propels materials along the length of the digestive tract by coordinated contractions of the circular and longitudinal layers Pearson Education, Inc.

17 Segmentation FIGURE 25.3B PERISTALSIS AND SEGMENTATION b Segmentation movements primarily involve the circular muscle layers. These activities churn and mix the contents of the digestive tract, but do not produce net movement in a particular direction Pearson Education, Inc.

18 Mesenteric artery and vein Mesentery Plica Mucosa Submucosa Muscularis externa Serosa (visceral peritoneum) FIGURE 25.2A HISTOLOGICAL STRUCTURE OF THE DIGESTIVE TRACT 2015 Pearson Education, Inc.

19 THE MUCOSA Inner lining of digestive tract Mucous membrane Cells are stratified squamous or simple columnar Stratified squamous Epithelium location: Simple columnar Epithelium location: Mucosa makes up folds called plicae Lamina propria

20 THE SUBMUCOSA Surrounds the muscularis mucosae Contains large blood vessels and lymphatics Contains submucosal plexus (innervation of the mucosa)

21 MUSCULARIS EXTERNA Surrounds submucosa Mostly smooth muscle fibers Forms sphincters or valves Contains myenteric plexus SEROSA (VISCERAL PERITONEUM) Covers the muscularis externa

22 THE ESOPHAGUS Hollow muscular tube from pharynx to stomach Enters peritoneal cavity by passing through esophageal hiatus of diaphragm Innervated by CN X Contains upper and lower esophageal sphincter Esophageal wall made up of mucosa lining, submucosa, smooth muscle layer (muscularis mucosae), muscularis externa Does not have serosa layer

23 FIGURE 25.9 HISTOLOGY OF THE ESOPHAGUS Muscularis mucosae Stratified squamous epithelium Mucosa Lamina propria Submucosa Muscularis externa Muscularis mucosae The esophagus LM x 5 The esophageal mucosa LM x 300 a Low-power view of a section through the esophagus b The esophageal mucosa 2015 Pearson Education, Inc.

24 THE STOMACH Histology:, Gastric pits with: mucous surface cells, mucous neck cells, parietal cells, chief cells, enteroendocrine cells Regions of stomach: lesser and greater curvature, cardia, fundus, body, and pylorus, gastric rugae

25 HISTOLOGY OF THE STOMACH Gastric pits: produce cells to continuously replace lost stomach cells. Mucous surface cells Produce mucus to protect lining of stomach Mucous neck cells Produce mucus to lubricate food entering stomach Parietal cells Secrete intrinsic factor and hydrochloric acid Chief cells Secrete pepsinogen which converts to pepsin Enteroendocrine cells- produce hormones G cells produce hormone gastrin

26 FIGURE 25.12CD HISTOLOGY OF THE STOMACH WALL Layers of the Stomach Wall Mucosa Gastric pit (opening to gastric gland) Gastric pit Luminal surface Lamina propria Mucous neck cells Mucous epithelium Cells of Gastric Glands Lamina propria Gastric gland Parietal cells Muscularis mucosae Submucosa Muscularis externa Oblique muscle Circular muscle Longitudinal muscle Serosa Artery and vein Lymphatic vessel Myenteric plexus d G cell Chief cells Smooth muscle cell Muscularis mucosae Diagrammatic view of a gastric gland and micrograph of the gastric mucosa. LM x 200 c Diagrammatic view of the organization of the stomach wall. This corresponds to a sectional view through the area indicated by the box in part (b).

27 Mesenteries of the Stomach Retractor Lesser curvature (medial surface) Esophagus Lesser Omentum Diaphragm Spleen Liver Hepatogastric Ligament STOMACH Left gastric artery Hepatoduodenal Ligament Right gastric artery Greater Omentum Greater curvature (lateral surface) Gall bladder Right kidney Duodenum FIGURE ANATOMY OF THE STOMACH 2015 Pearson Education, Inc.

28 Musculature of the Stomach Longitudinal muscle layer Circular muscle layer Oblique muscle layer (overlying mucosa) FIGURE ANATOMY OF THE STOMACH 2015 Pearson Education, Inc.

29 BLOOD SUPPLY TO STOMACH Three branches from celiac trunk: Left gastric artery Supplies lesser curvature and cardia Splenic artery Supplies blood to fundus Branches and supplies greater curvature Common hepatic artery Branches and supplies greater and lesser curvatures

30 Inferior vena cava THORACIC AORTA Celiac trunk ABDOMINAL AORTA Common hepatic Left gastric Splenic Superior mesenteric Inferior mesenteric Left common iliac Intestinal Right external iliac Right internal iliac FIGURE 22.15A ARTERIES OF THE ABDOMEN Rectal 2015 Pearson Education, Inc.

31 WHICH OF THE FOLLOWING CELLS PRODUCE GASTRIN, A SUBSTANCE THAT STIMULATES SECRETORY ACTIVITY AND ENHANCES SMOOTH MUSCLE ACTIVITY? A. parietal cells B. enteroendocrine cells C. beta cells D. chief cells

32 WHICH OF THE FOLLOWING CELLS PRODUCE GASTRIN, A SUBSTANCE THAT STIMULATES SECRETORY ACTIVITY AND ENHANCES SMOOTH MUSCLE ACTIVITY? A. parietal cells B. enteroendocrine cells C. beta cells D. chief cells

33 THE STOMACH AND LIVER ARE EXAMPLES OF WHICH OF THE FOLLOWING? A. intraperitoneal organs B. retroperitoneal organs C. interperitoneal organs D. secondarily retroperitoneal organs

34 THE PERITONEUM The abdominal organs lie within the peritoneal cavity (abdominal cavity) and covered by visceral peritoneum Intraperitoneal organs Stomach, liver, ileum, jejunum, parts of colon (transverse and sigmoid) Retroperitoneal organs Kidneys, ureters, abdominal aorta, most of duodenum, pancreas, ascending and descending colon, and rectum Secondarily retroperitoneal organs Pancreas, duodenum

35 MESENTERIES Fused double sheets of peritoneal membrane Function: Mesentery proper suspends digestive organs except duodenum Mesocolon = attaches to _large intestine Transverse mesocolon = attaches to transverse mesocolon Sigmoid mesocolon = attaches to sigmoid colon

36 MESENTERIES CONTINUED Fusion fascia Attaches the ascending, descending, and rectum to posterior abdominal wall Lesser omentum Mesentery that lies between the stomach and the liver Greater omentum Mesentery extends from stomach and covers the rest of the abdominal organs on the anterior surface

37 Lesser omentum Greater omentum (cut) Transverse mesocolon Mesentery proper (mesenterial sheet) Fusion fascia of ascending and descending colons fuses to dorsal peritoneum Sigmoid colon FIGURE 25.4D MESENTERIES 2015 Pearson Education, Inc.

38 THE STOMACH AND LIVER ARE EXAMPLES OF WHICH OF THE FOLLOWING? A. intraperitoneal organs B. retroperitoneal organs C. interperitoneal organs D. secondarily retroperitoneal organs

39 Mesenteric artery and vein Plica Mesentery Plica Mucosal epithelium Lamina propria Mucosa Villi Mucosal glands Submucosal gland Muscularis mucosae Mucosa Lymphatic vessel Artery and vein Submucosa Muscularis externa Serosa (visceral peritoneum) Submucosal plexus Circular muscle layer Myenteric plexus Longitudinal muscle layer a Three-dimensional view of the histological organization of the general digestive tube b An enlarged section of the digestive tube showing the structure of a plica FIGURE 25.2AB HISTOLOGICAL STRUCTURE OF THE DIGESTIVE TRACT 2015 Pearson Education, Inc.

40 SMALL INTESTINE Approx 20 feet by in diameter Duodenum 10 inches; receives digestive enzymes from pancreas, bile from liver and gallbladder Jejunum 8 feet, site of most digestion and absorption Ileum 12 feet long

41 Duodenum Jejunum Ileum FIGURE REGIONS OF THE SMALL INTESTINE 2015 Pearson Education, Inc.

42 FIGURE 25.14A-C HISTOLOGY OF THE INTESTINAL WALL Plica circularis Villi Lymphoid nodule Layers of the Small Intestine Lamina propria Mucosa Muscularis mucosae Submucosa Muscularis externa Submucosal plexus Circular layer of smooth muscle Myenteric plexus Arteriole Venule Lymphatic vessel Serosa Longitudinal layer of smooth muscle 2015 Pearson Education, Inc.

43 FIGURE 25.14C HISTOLOGY OF THE INTESTINAL WALL Goblet cell Columnar epithelial cell Lacteal Nerve Capillary network Lamina propria Arteriole Venule Lymphatic vessel c Diagrammatic view of a single villus showing the capillary and lymphatic supply

44 REGIONAL SPECIALIZATIONS OF SMALL INTESTINES Duodenum Contains duodenal submucosa glands Receives bile from liver and gallbladder Buffers and digestive enzymes from pancreas Jejunum Has prominent plicae and villi Ilium Contains prominent lymphoid centers called aggregated lymphoid nodules (Peyer s patches)

45 REGULATION OF SMALL INTESTINES Vagal (CN X) stimulation, enteroendocrine cells of small intestines release: Secretin Causes liver to begin making bile Causes pancreas to release buffers Cholecyostokinin Causes pancreas to release digestive enzymes Causes gallbladder to contract to release bile Causes hepatopancreatic sphincter to open

46 LARGE INTESTINES Approx 5 feet in length by 3 inches in diameter Receives blood from branches of superior and inferior mesenteric arteries Function:

47 Aorta Hepatic portal vein Superior mesenteric vein Inferior vena cava Splenic vein Superior mesenteric artery Inferior mesenteric vein Left colic vein Inferior mesenteric artery Omental appendices Intestinal arteries and veins Rectal artery Sigmoid arteries and veins Taenia coli FIGURE 25.16A THE LARGE INTESTINE Rectum 2015 Pearson Education,

48 THE COLON The wall of the colon has pouches that allow for expansion called haustra Longitudinal muscles called teniae coli aid in the process of peristalsis The serosa of the large intestine has numerous flaps of sacs of fat attached to, extending from the intestine called omental appendices

49 HISTOLOGY OF LARGE INTESTINES Walls are thinner than the walls of the small intestine The walls lack villi Has numerous goblet cells Has very distinctive intestinal crypts Produces lots of mucus to lubricate undigested material Contains large lymphoid nodules

50 FIGURE 25.18A THE WALL OF THE LARGE INTESTINE Taenia coli Omental appendices Haustrum Layers of the Large Intestine Mucosa Lymphoid nodule Simple columnar epithelium Goblet cells Muscularis mucosae Submucosa Muscularis externa Serosa Circular layer Longitudinal layer (taenia coli) Intestinal crypt 2015 Pearson Education, Inc.

51 FIGURE Left colic (splenic) flexure Right colic (hepatic) flexure Transverse colon Haustra Ascending colon Descending colon Cecum Sigmoid colon Rectum 2015 Pearson Education,

52 Major Subdivisions of the Digestive Tract Oral Cavity Mouth Pharynx Accessory Organs of the Digestive System Salivary Glands Esophagus Liver Stomach Small Intestine Gallbladder Large Intestine Pancreas Anus

53 THE LIVER Largest visceral organ of the body Metabolic regulation Hematological regulation Bile production

54 FIGURE 25.21AC Round ligament Right hepatic duct Cystic duct Gallbladder Left hepatic duct Common hepatic duct Common bile duct Liver Duodenum Hepatic portal vein Common hepatic artery Stomach Pancreas Hepatopancreatic sphincter Duodenal ampulla Duodenal papilla Intestinal lumen Pancreas Common bile duct Pancreatic duct 2015 Pearson Education, Inc.

55 Major Subdivisions of the Digestive Tract Oral Cavity Mouth Pharynx Esophagus Stomach Small Intestine Large Intestine Accessory Organs of the Digestive System Salivary Glands Secretion of lubricating fluid containing enzymes that break down carbohydrates Liver Secretion of bile (important for lipid digestion), storage of nutrients, many other vital functions Gallbladder Storage and concentration of bile Pancreas Exocrine cells secrete buffers and digestive enzymes; endocrine cells secrete hormones Anus FIGURE 25.1 COMPONENTS OF THE DIGESTIVE SYSTEM 2015 Pearson Education, Inc.

56 2015 Pearson Education, Inc.

57 FIGURE 25.19C ANATOMY OF THE LIVER Coronary ligament Right lobe Left lobe Falciform ligament Round ligament Gallbladder 2015 Pearson Education, Inc.

58 ACCESSORY GLANDULAR DIGESTIVE ORGANS Anatomy of the Liver Falciform ligament Marks the boundary between the left and right lobes The inferior portion of the falciform ligament becomes thick and round and is called the round ligament The falciform ligament spreads on the surface of the liver attaching to the inferior side of the diaphragm This spreading ligament is called the coronary ligament

59 HISTOLOGICAL ORGANIZATION OF THE LIVER The liver is divided into approximately 100,000 liver lobules Each lobule is separated by the interlobular septum The center of each lobule consists of a vein from the hepatic portal system The hepatocytes are arranged in such a manner forming cellular lines extending from the central vein outward Spaces created between lines of hepatocytes are called sinusoids Sinusoids consists of capillaries leading to central vein and Kupffer cells

60 Interlobular septum Bile duct Branch of hepatic portal vein Portal area Bile ductules 2015 Pearson Education, Inc.

61 FIGURE 25.21AC Round ligament Right hepatic duct Cystic duct Gallbladder Left hepatic duct Common hepatic duct Common bile duct Liver Duodenum Hepatic portal vein Common hepatic artery Stomach Pancreas Hepatopancreatic sphincter Duodenal ampulla Duodenal papilla Intestinal lumen Pancreas Common bile duct Pancreatic duct 2015 Pearson Education, Inc.

62 GALLBLADDER When hepatopancreatic sphincter is closed: Bile enters cystic duct into gallbladder Gall bladder can store ml of bile Water is removed to concentrate bile If food in sm intestines is high in fat content, sm intestines release cholecystokinin_(cck) cholecystokinin will cause gallbladder to release bile

63 Left hepatic duct Right hepatic duct Cystic duct Gallbladder Common hepatic duct Common bile duct Liver Duodenum Pancreas Stomach

64 Major Subdivisions of the Digestive Tract Oral Cavity Mouth Pharynx Accessory Organs of the Digestive System Salivary Glands Esophagus Liver Stomach Small Intestine Gallbladder Large Intestine Pancreas Exocrine cells secrete buffers and digestive enzymes; endocrine cells secrete hormones Anus 2015 Pearson Education, Inc.

65 Splenic artery Tail of pancreas Abdominal aorta Celiac trunk Common hepatic artery Common bile duct Superior pancreatic artery Lobules Head of pancreas Pancreatic duct (to greater duodenal papilla) with common bile duct Body of pancreas Superior mesenteric artery FIGURE 25.22A THE PANCREAS 2015 Pearson Education, Inc.

66 HISTOLOGY OF PANCREAS Consists of lobules with: Acinar cells: Produce digestive enzymes Enzymes travel through the pancreatic duct to the small intestines Pancreatic islets: Produce hormones Hormones enter bloodstream to travel to target organs

67 Pancreatic duct Acinar cells (exocrine) Pancreatic islet (endocrine) Pancreatic acini FIGURE 25.22B THE PANCREAS 2015 Pearson Education,

68 FIGURE 25.22C THE PANCREAS Duct Pancreatic acini (exocrine) Pancreatic islet (endocrine) Pancreas LM x Pearson Education,

69 PANCREATIC ENZYMES (FROM ACINAR CELLS) Lipases Carbohydrases Nucleases Proteinases PANCREATIC HORMONES (FROM PANCREATIC ISLETS Insulin Glucagon Somatostatin

70 REGULATION OF PANCREATIC SECRETION Cholecystokinin (CKK) From small intestines will cause pancreas to release digestive enzymes Secretin From small intestines will cause the pancreas to release buffers to neutralize acidic chyme from stomach