Presentation is loading. Please wait.

Presentation is loading. Please wait.

The Digestive System. Functions of the Digestive System Ingest food Ingest food Break down food into nutrient molecules Break down food into nutrient.

Similar presentations


Presentation on theme: "The Digestive System. Functions of the Digestive System Ingest food Ingest food Break down food into nutrient molecules Break down food into nutrient."— Presentation transcript:

1 The Digestive System

2 Functions of the Digestive System Ingest food Ingest food Break down food into nutrient molecules Break down food into nutrient molecules Absorb molecules into the bloodstream Absorb molecules into the bloodstream Rid the body of indigestible remains Rid the body of indigestible remains

3

4 Main Divisions of the Digestive System Alimentary Canal Alimentary Canal Continuous, muscular digestive tube winding throughout the body Continuous, muscular digestive tube winding throughout the body Digests and absorbs food particles Digests and absorbs food particles Contains the following organs: Contains the following organs: Mouth, Pharynx, Esophagus, Stomach, Small and Large Intestines Mouth, Pharynx, Esophagus, Stomach, Small and Large Intestines Accessory Digestive Organs Accessory Digestive Organs Contains the following organs: Contains the following organs: Teeth, Tongue, Gallbladder, Salivary Glands, Liver, and Pancreas Teeth, Tongue, Gallbladder, Salivary Glands, Liver, and Pancreas

5 Digestive System Divisions

6 Digestive Processes Ingestion Ingestion Propulsion Propulsion Mechanical digestion Mechanical digestion Chemical digestion Chemical digestion Absorption Absorption Defecation Defecation

7 Circulation of the Alimentary Canal/GI Tract Splanchnic Circulation Splanchnic Circulation Includes all arteries branching off the abdominal aorta and the hepatic portal circulation Includes all arteries branching off the abdominal aorta and the hepatic portal circulation Arterial supply: Arterial supply: Celiac Trunk (hepatic, splenic, and left gastric) Celiac Trunk (hepatic, splenic, and left gastric) Mesenteric Arteries: sup. and inf. Mesenteric Arteries: sup. and inf. Receives ¼ of the blood volume (CO); increases after a meal Receives ¼ of the blood volume (CO); increases after a meal

8 Histology of the Alimentary Canal/GI Tract From esophagus to anus, the walls of the alimentary canal have the same 4 layers: From esophagus to anus, the walls of the alimentary canal have the same 4 layers: Mucosa (secretes hormones and mucus, absorbs end products of digestion, and protects against infection Mucosa (secretes hormones and mucus, absorbs end products of digestion, and protects against infection Submucosa (contains lymphoid follicles and elastic tissue) Submucosa (contains lymphoid follicles and elastic tissue) Muscularis externa (segmentation and peristalsis, contains inner circular layer and outer longitudinal layer, area where valves are found) Muscularis externa (segmentation and peristalsis, contains inner circular layer and outer longitudinal layer, area where valves are found) Serosa (same as visceral peritoneum, made of areolar connective tissue) Serosa (same as visceral peritoneum, made of areolar connective tissue)

9

10 Histology of the GI Tract

11 Peritoneum Peritoneum is the serous membrane lining the abdominopelvic cavity Visceral peritoneum covers the external surfaces of most digestive organs and is continuous with the parietal peritoneum that lines the body wall Between the two peritoneums is the peritoneal cavity Mesentery is a double layer peritoneum; provides routes for BV, lymphatics, nerves Alimentary canal organs are classified as Retroperitoneal - no mesentery and organs lies posterior to the peritoneum (SADPUCKER) Intraperitoneal - mesentery and organs lies within the peritoneal cavity

12

13 Features and Functions of the Mouth Buccal/oral cavity Buccal/oral cavity Contains stratified squamous epithelium Contains stratified squamous epithelium Vestibule: area bounded by lips and cheeks externally and teeth and gums internally Vestibule: area bounded by lips and cheeks externally and teeth and gums internally Lips: posses no sweat or oil glands Lips: posses no sweat or oil glands Palate: forms roof of the mouth, soft and hard palate, uvula Palate: forms roof of the mouth, soft and hard palate, uvula

14 Anatomy of the Mouth

15 Features and Functions of the Tongue Helps grind food into a bolus which contains partially digested food and saliva Helps grind food into a bolus which contains partially digested food and saliva Helps form words and is a sensory organ for taste Helps form words and is a sensory organ for taste Three surface features: Three surface features: Filiform papillae (roughness and grip) Filiform papillae (roughness and grip) Fungiform papillae (contains taste buds) Fungiform papillae (contains taste buds) Circumvallate papillae (contains taste buds) Circumvallate papillae (contains taste buds)

16 Anatomy of the Tongue

17 Features and Functions of the Salivary Glands Main functions: Main functions: Produces and secretes saliva Produces and secretes saliva Cleanses the mouth Cleanses the mouth Dissolves food chemicals so they can be tasted Dissolves food chemicals so they can be tasted Moistens food, compacting it into a bolus Moistens food, compacting it into a bolus Begins the chemical breakdown of food Begins the chemical breakdown of food Salivary amylase: starch Salivary amylase: starch

18 Types of Salivary Glands Submandibular Glands Submandibular Glands Found underneath the mandible Found underneath the mandible Sublingual Glands Sublingual Glands Found underneath the tongue Found underneath the tongue Parotid Glands Parotid Glands Found anterior to the ear between masseter and skin Found anterior to the ear between masseter and skin Saliva travels to oral orifice via ducts from all three glands Saliva travels to oral orifice via ducts from all three glands

19 Anatomy of the Salivary Glands

20 Composition of Saliva: % water Composition of Saliva: % water pH pH Sodium, potassium, chloride, phosphate, and bicarbonate Sodium, potassium, chloride, phosphate, and bicarbonate Mucin Mucin Salivary amylase Salivary amylase

21 Features and Functions of the Teeth Break food into smaller parts, increasing surface area for digestion Break food into smaller parts, increasing surface area for digestion Types of Teeth Types of Teeth Deciduous Teeth (“baby” teeth) Deciduous Teeth (“baby” teeth) Permanent Teeth Permanent Teeth Incisors- cutting and shredding Incisors- cutting and shredding Canines- piercing and tearing Canines- piercing and tearing Molars- grinding Molars- grinding Premolars- grinding and crushing Premolars- grinding and crushing

22 Tooth Structure Crown: exposed portion of tooth covered by enamel which covers dentin Crown: exposed portion of tooth covered by enamel which covers dentin Root: internal portion that is beneath the gums (gingiva) and is anchored by periodontal ligaments Root: internal portion that is beneath the gums (gingiva) and is anchored by periodontal ligaments

23 Deglutition and the Pharynx Deglutition = swallowing Deglutition = swallowing Oropharynx and Laryngopharynx are common passageways for food and air Oropharynx and Laryngopharynx are common passageways for food and air Pharynx contains stratified squamous epithelium (friction-resistant) Pharynx contains stratified squamous epithelium (friction-resistant)

24 Features and Functions of the Esophagus Muscular tube that propels food to stomach; bolus enters stomach through esophageal hiatus Muscular tube that propels food to stomach; bolus enters stomach through esophageal hiatus Skeletal muscle (upper third for swallowing) and smooth muscle (lower third) for peristalsis Skeletal muscle (upper third for swallowing) and smooth muscle (lower third) for peristalsis Esophageal glands – produce mucus to lubricate bolus Esophageal glands – produce mucus to lubricate bolus Esophageal sphincter – prevents backflow into oral cavity Esophageal sphincter – prevents backflow into oral cavity Cardiac sphincter- prevents backflow into esophagus Cardiac sphincter- prevents backflow into esophagus

25 Anatomy of the Esophagus

26 Microscopic Anatomy of the Esophagus

27 Digestive Processes in the Mouth, Pharynx, and Esophagus Mouth processes: Mouth processes: Ingestion Ingestion Mechanical digestion (e.g. salivary amylase) Mechanical digestion (e.g. salivary amylase) Initiation of Propulsion Initiation of Propulsion Mastication: chewing Mastication: chewing Pharyngeal processes: Pharyngeal processes: Deglutition = swallowing Deglutition = swallowing Voluntary Buccal phase Voluntary Buccal phase Involuntary Pharyngeal-Esophageal Phase Involuntary Pharyngeal-Esophageal Phase Esophageal processes: Esophageal processes: Peristalsis (rhythmic contractions, involuntary) Peristalsis (rhythmic contractions, involuntary)

28 Deglutition and the Pharynx

29 Peristalsis

30 Features and Functions of the Stomach Temporary storage area for food and allows it to mix with gastric juice to produce chyme Temporary storage area for food and allows it to mix with gastric juice to produce chyme Regions: cardiac, fundus, body, and pyloric Regions: cardiac, fundus, body, and pyloric Greater and Lesser Curvatures: connected to greater and lesser omentums Greater and Lesser Curvatures: connected to greater and lesser omentums Rugae folds: longitudinal folds in stomach wall Rugae folds: longitudinal folds in stomach wall - mucous b/w folds Muscle layers arranged circularly, longitudinally, AND obliquely (aids in digestion) Muscle layers arranged circularly, longitudinally, AND obliquely (aids in digestion)

31 Anatomy of the Stomach

32 Microscopic Anatomy of the Stomach Simple columnar epithelium – contains gastric pits that secrete gastric juices Simple columnar epithelium – contains gastric pits that secrete gastric juices Goblet cells – secrete mucus that coats stomach and prevents it from being digested itself Goblet cells – secrete mucus that coats stomach and prevents it from being digested itself Parietal cells – secrete hydrochloric acid (converts pepsinogen into pepsin) and intrinsic factor (necessary for absorption of vitamin B 12) Parietal cells – secrete hydrochloric acid (converts pepsinogen into pepsin) and intrinsic factor (necessary for absorption of vitamin B 12) Chief cells – secrete pepsinogen which is converted to pepsin to aid in protein digestion Chief cells – secrete pepsinogen which is converted to pepsin to aid in protein digestion Enteroendocrine cells – release hormones such as: Enteroendocrine cells – release hormones such as: Histamine, Serotonin, Gastrin, Endorphins, and Somatostatin Histamine, Serotonin, Gastrin, Endorphins, and Somatostatin

33 Histamine Histamine - activates parietal cells to release HCl Serotonin Serotonin - contraction of stomach muscle Gastrin Gastrin - gastric glands to increase secretion Endorphins Endorphins - natural opiates Somatostatin Somatostatin - sympathetic n.s. - inhibits gastric secretion - inhibits gastric emptying

34 Microscopic Anatomy of the Digestive System

35 Digestive Processes in the Stomach Gastric Secretion Gastric Secretion Cephalic Phase Cephalic Phase Stimulated by the thought, sight, taste, or aroma or food Stimulated by the thought, sight, taste, or aroma or food Inputs from olfactory receptors and taste buds travel to parasympathetic enteric ganglia which then stimulate stomach glands Inputs from olfactory receptors and taste buds travel to parasympathetic enteric ganglia which then stimulate stomach glands Gastric Phase Gastric Phase Stomach distension activates stretch receptors Stomach distension activates stretch receptors Food chemicals (e.g. peptides, rising pH) activate chemoreceptors which activate G cells which secrete gastrin Food chemicals (e.g. peptides, rising pH) activate chemoreceptors which activate G cells which secrete gastrin Intestinal Phase Intestinal Phase Presence of low pH and partially digested foods in duodenum stimulates intestinal gastrin secretion Presence of low pH and partially digested foods in duodenum stimulates intestinal gastrin secretion

36 Digestive Processes in the Stomach

37 Gastric Motility and Emptying Peristaltic waves approach stomach and become stronger near pyloric region Peristaltic waves approach stomach and become stronger near pyloric region Pyloric sphincter allows ~ 3 mL of chyme to pass to duodenum and the rest to return to stomach for further mixing Pyloric sphincter allows ~ 3 mL of chyme to pass to duodenum and the rest to return to stomach for further mixing

38 Features and Functions of the Small Intestine Receives chyme from stomach; performs majority of digestion and absorption of nutrients Receives chyme from stomach; performs majority of digestion and absorption of nutrients Regions: Regions: Duodenum (upper region receiving chyme from stomach and digestive enzymes from pancreas and bile from liver and gallbladder) Duodenum (upper region receiving chyme from stomach and digestive enzymes from pancreas and bile from liver and gallbladder) Jejunum/Ileum (lower regions where absorption occurs) Jejunum/Ileum (lower regions where absorption occurs) Plicae circulares (permanent folds in mucosa and submucosa that slow movement of chyme) Plicae circulares (permanent folds in mucosa and submucosa that slow movement of chyme)

39

40

41 Anatomy of the Small Intestine

42 Microscopic Anatomy of Small Intestine Villi: fingerlike projections that increase the surface area of the SI Villi: fingerlike projections that increase the surface area of the SI Microvilli: tiny projections on the plasma membranes of columnar cells that appear fuzzy (i.e. brush border cells) Microvilli: tiny projections on the plasma membranes of columnar cells that appear fuzzy (i.e. brush border cells) Crypts of Lieberkuhn: secrete intestinal juice and special lysozymes that protect against bacteria Crypts of Lieberkuhn: secrete intestinal juice and special lysozymes that protect against bacteria Peyer’s Patches: aggregated lymphoid tissues containing lymphocytes Peyer’s Patches: aggregated lymphoid tissues containing lymphocytes

43 Microscopic Anatomy of the Small Intestine

44 Secretions of the Small Intestine Secretin: released by enteroendocrine cells when acidic chyme enters SI; causes release of bicarbonate-rich pancreatic juices Secretin: released by enteroendocrine cells when acidic chyme enters SI; causes release of bicarbonate-rich pancreatic juices Somatostatin: slows gastric motility and emptying and inhibits production of gastric secretions Somatostatin: slows gastric motility and emptying and inhibits production of gastric secretions Cholecystokinin (CCK): released when fatty, protein- rich chyme enters SI; causes release of enzyme-rich pancreatic juices and bile Cholecystokinin (CCK): released when fatty, protein- rich chyme enters SI; causes release of enzyme-rich pancreatic juices and bile Brush border enzymes: process long peptides, nucleic acids, and sugars into smaller ones Brush border enzymes: process long peptides, nucleic acids, and sugars into smaller ones

45 After Digestion: Absorption ProteinFats

46 Functions of the Liver Largest internal organ Largest internal organ Functions: Functions: Filters and processes nutrient-rich blood of carbohydrates, proteins, and lipids from intestine Filters and processes nutrient-rich blood of carbohydrates, proteins, and lipids from intestine Production and regulation of cholesterol Production and regulation of cholesterol Production of bile which emulsifies fats Production of bile which emulsifies fats Removes drugs and hormones from circulation Removes drugs and hormones from circulation Storage of vitamins and minerals Storage of vitamins and minerals

47 Anatomy of the Liver Right and Left Lobes: separated by falciform ligament Right and Left Lobes: separated by falciform ligament Caudate and Quadrate Lobes: found on posterior side Caudate and Quadrate Lobes: found on posterior side Blood vessels: Blood vessels: Hepatic artery/vein and hepatic portal vein Hepatic artery/vein and hepatic portal vein Gallbladder: found underneath left lobe, stores bile Gallbladder: found underneath left lobe, stores bile

48 Gross Anatomy of the Liver

49

50 Microscopic Anatomy of the Liver Liver Lobules: structural unit of liver Liver Lobules: structural unit of liver Hepatocytes: liver cells contained within the lobules Hepatocytes: liver cells contained within the lobules Hepatic portal vein & Hepatic Artery: the circulation of the liver, they bring blood into the liver where it is filtered through the liver sinusoidal capillaries Hepatic portal vein & Hepatic Artery: the circulation of the liver, they bring blood into the liver where it is filtered through the liver sinusoidal capillaries Kupffer cells: remove debris Kupffer cells: remove debris Filtered blood drains into the central vein, then to the hepatic vein, and eventually to the inferior vena cava Filtered blood drains into the central vein, then to the hepatic vein, and eventually to the inferior vena cava Bile (produced by hepatocytes) drains into the bile duct after passing through portal triad Bile (produced by hepatocytes) drains into the bile duct after passing through portal triad Bile then shipped to gallbladder for storage Bile then shipped to gallbladder for storage

51 Microscopic Anatomy of the Liver

52

53 Blood supply - receives fresh O2 blood from hepatic artery (off of aorta) - receives deoxygenated blood with nutrients (from small intestine) - receives deoxygenated blood with nutrients (from small intestine) - hepatic portal vein - From liver- hepatic vein- inferior vena cava Hepatic portal vein, hepatic artery and bile ducts make up the portal triad.

54

55 Function and Regulation of Bile Bile ducts are present at every portal triad Bile ducts are present at every portal triad Bile flows down bile canaliculi (tiny canals) between adjacent hepatocytes towards bile duct branches at every portal triad Bile flows down bile canaliculi (tiny canals) between adjacent hepatocytes towards bile duct branches at every portal triad Bile enters the bile ducts which drain into the common hepatic duct Bile enters the bile ducts which drain into the common hepatic duct Bile emulsifies fats, separating them into smaller parts Bile emulsifies fats, separating them into smaller parts Bilirubin: the chief bile pigment, a waste product of the heme of hemoglobin formed during the breakdown of worn-out erythrocytes Bilirubin: the chief bile pigment, a waste product of the heme of hemoglobin formed during the breakdown of worn-out erythrocytes

56 Regulation of Bile Production Bile exits cystic duct upon stimulation Bile exits cystic duct upon stimulation CCK released when acidic, fatty chyme enters intestines CCK released when acidic, fatty chyme enters intestines Causes: Causes: Gallbladder Contraction Gallbladder Contraction Pancreatic Juice Secretion Pancreatic Juice Secretion Relaxation of hepatopancreatic sphincter Relaxation of hepatopancreatic sphincter

57 Features and Functions of the Pancreas Pancreatic Juice secreted by acinar cells Pancreatic Juice secreted by acinar cells Islets of Langerhans release insulin and glucagon (important in glucose metabolism) Islets of Langerhans release insulin and glucagon (important in glucose metabolism) Pancreatic Juice contains: Pancreatic Juice contains: Sodium Bicarbonate (buffers HCl in stomach) Sodium Bicarbonate (buffers HCl in stomach) Proteases (break down polypeptides) Proteases (break down polypeptides) Pancreatic amylase (digests oligosaccarides and disaccharides into monosaccharides) Pancreatic amylase (digests oligosaccarides and disaccharides into monosaccharides) Pancreatic lipases (break down lipids into fatty acids and glycerol) Pancreatic lipases (break down lipids into fatty acids and glycerol) Pancreatic nucleases (break down nucleic acids) Pancreatic nucleases (break down nucleic acids)

58 Anatomy of the Pancreas

59 Regulation of Pancreatic Secretion

60 Features and Functions of the Large Intestine Functions: Functions: Reabsorption of remaining water and electrolytes Reabsorption of remaining water and electrolytes Production and absorption of Vitamins B and K Production and absorption of Vitamins B and K Elimination of feces Elimination of feces Diameter is only 7 cm but is larger than that of the small intestine Diameter is only 7 cm but is larger than that of the small intestine

61 Gross Anatomy of the Large Intestine Teniae Coli: bands of smooth muscle that create pocket-like sacs (haustra) Teniae Coli: bands of smooth muscle that create pocket-like sacs (haustra) Cecum: sac-like connection between the small and large intestines Cecum: sac-like connection between the small and large intestines Appendix: small structure containing lymphoid tissue; small immune function Appendix: small structure containing lymphoid tissue; small immune function Ascending, Descending, Transverse, and Sigmoid Colon Ascending, Descending, Transverse, and Sigmoid Colon Splenic and hepatic flexure Splenic and hepatic flexure Rectum: storage area Rectum: storage area Anus: regulates defecation with two sphincter muscles; internal and external Anus: regulates defecation with two sphincter muscles; internal and external

62 Anatomy of the Colon

63 Microscopic Anatomy of the Large Intestine Simple columnar epithelium for absorption except in the anal canal where there is stratified squamous Simple columnar epithelium for absorption except in the anal canal where there is stratified squamous No villi, no digestive-secreting cells No villi, no digestive-secreting cells Goblet cells produce mucus for lubrication of feces Goblet cells produce mucus for lubrication of feces Bacterial flora synthesize vitamin B and most of the vitamin K needed for blood clotting Bacterial flora synthesize vitamin B and most of the vitamin K needed for blood clotting

64 Microscopic Anatomy of the Large Intestine

65 Summary of Digestion

66

67 The Process of Absorption

68 Clinical corner Peptic ulcers - gastric and duodenal, caused by Helicobacter pylori, NSAIDS, Hcl hypersecretion Peptic ulcers - gastric and duodenal, caused by Helicobacter pylori, NSAIDS, Hcl hypersecretion Cirrohsis - scarred liver due to chronic inflammation Cirrohsis - scarred liver due to chronic inflammation Hepatitis - A,B,C,D, and E Hepatitis - A,B,C,D, and E Biliary calculi - gall stones - crystals of cholesterol in bile Biliary calculi - gall stones - crystals of cholesterol in bile Borborygmus - rumbling noise caused by gas through intestines Borborygmus - rumbling noise caused by gas through intestines

69 Cholecystitis - inflammation of gall bladder Cholecystitis - inflammation of gall bladder Colitis - inflammation of colon Colitis - inflammation of colon Dysphagia - difficulty in swallowing Dysphagia - difficulty in swallowing Enteritis - inflammation of the intestines Flatuation/erucation Enteritis - inflammation of the intestines Flatuation/erucation


Download ppt "The Digestive System. Functions of the Digestive System Ingest food Ingest food Break down food into nutrient molecules Break down food into nutrient."

Similar presentations


Ads by Google