The Digestive System. Chapter 14. The Digestive System and Body Metabolism. Metabolism. Organs of the Digestive System. Digestion.

Transcription

1 Chapter 14 The Digestive System The Digestive System and Body Metabolism Digestion of ingested food of nutrients into the blood Metabolism Production of Constructive and degradative cellular activities Organs of the Digestive System Two main groups continuous coiled hollow tube

2 Organs of the Digestive System Figure 14.1 Organs of the Alimentary Canal Mouth (Oral Cavity) Anatomy (labia) protect the anterior opening form the lateral walls forms the anterior roof forms the posterior roof fleshy projection of the soft palate Figure 14.2a

3 Mouth (Oral Cavity) Anatomy Vestibule space between lips externally and teeth and gums internally area contained by the teeth attached at hyoid and styloid processes of the skull, and by the lingual frenulum Figure 14.2a Mouth (Oral Cavity) Anatomy Tonsils tonsils tonsil Figure 14.2a Processes of the Mouth (chewing) of food Mixing masticated food with breaking chemical bonds Initiation of swallowing by the Allowing for the sense of taste

4 Pharynx Anatomy not part of the digestive system posterior to oral cavity below the oropharynx and connected to the esophagus Figure 14.2a Pharynx Function Serves as a passageway for and Swallowing starts voluntarily (skeletal muscle); push food toward with tongue closes nasopharnyx; closes larnyx; tongue blocks oral cavity food can only go to Pharynx Function Food is propelled to the esophagus by two muscle layers (smooth muscle) inner layer outer layer Food movement is by alternating contractions of the muscle layers ( )

5 Esophagus Runs from pharynx to stomach through the diaphragm (collapsible tube) Has walls seen in rest of GI tract Conducts food by peristalsis (slow rhythmic squeezing) carries to stomach Passageway for only (respiratory system branches off after the pharynx) Layers of Alimentary Canal Organs Mucosa Innermost layer Specialized cells for (mucus &/or enzyme) Moist membrane Surface epithelium Small amount of tissue (lamina propria) Small muscle layer Layers of Alimentary Canal Organs Submucosa Just beneath the Soft connective tissue with blood vessels, nerve endings, and lymphatics

6 Layers of Alimentary Canal Organs Muscularis externa muscle Inner layer Outer l layer Mixes and propels food through canal (peristalsis) Serosa Outermost layer serous membrane covering organs; peritoneum Layer of serous fluid-producing cells Layers of Alimentary Canal Organs Figure 14.3 Alimentary Canal Nerve Plexuses All are part of the autonomic nervous system Three separate networks of nerve fibers Submucosal nerve plexus Myenteric nerve plexus Subserous plexus Regulates motility and secretion of GI tract organs

7 Stomach Anatomy C-shaped pouch, enlarged area of canal Located on the left side of the abdominal cavity Food enters at the sphincter (weak musclular valve at end of esophagus); keeps stomach contents in stomach Heartburn Stomach Anatomy Regions of the stomach near the heart funnel-shaped terminal end Food empties into the small intestine at the sphincter (strong valve) Controls how much food enters Stomach Anatomy Rugae External regions curvature curvature

8 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 to insulate, cushion, and protect abdominal organs Stomach Anatomy Figure 14.4a Stomach Functions Acts as a storage tank for food Churns 3 layers of muscle; mix food with gastric juice ( = food + gastric juices)) Site of food breakdown; chemical breakdown of begins Delivers chyme (processed food) to the

9 Specialized Mucosa of the Stomach Simple columnar epithelium produce a sticky alkaline mucus Protects stomach lining Gastric glands Chief cells Produce protein-digesting enzymes Specialized Mucosa of the Stomach Parietal cells produce Kills bacteria Softens connective tissue Activates Endocrine cells produce Regulates secretion of gastric juices Intrinsic factor produced by Needed for the absorption of Structure of the Stomach Mucosa Gastric pits formed by folded Glands and specialized cells are in the gastric gland region

10 Structure of the Stomach Mucosa Figure 14.4b, c Small Intestine The body s major digestive organ Site of nutrient into the blood Muscular tube extending form the pyloric sphincter to the valve Suspended from the posterior abdominal wall by the mesentery Subdivisions of the Small Intestine Attached to the stomach Curves around the head of the pancreas Attaches anteriorly to the duodenum Extends from jejunum to large intestine

11 Chemical Digestion in the Small Intestine Source of enzymes that are mixed with chyme Intestinal cells Pancreas Bile enters from the Chemical Digestion in the Small Intestine Figure 14.6 Villi of the Small Intestine Fingerlike structures formed by the Give the small intestine more Figure 14.7a

12 Microvilli of the Small Intestine Small projections of the Found on cells Figure 14.7c Structures Involved in Absorption of Nutrients Absorptive cells Blood capillaries Lacteals (specialized lymphatic capillaries) Figure 14.7b Folds of the Small Intestine Called folds or plicae circulares Deep folds of the mucosa and submucosa Do not disappear when filled with food The submucosa has (collections of lymphatic tissue)

13 Function of the Small Intestine - receives digestive juices from pancreas, brush border cells and bile from liver most of the absorption occurs in small intestines; it is the longest part of the GI tract; increased surface area (villi, microvilli, etc.) Large Intestine Larger in diameter, but shorter than the small intestine Frames the internal abdomen Large Intestine Figure 14.8

14 Structures of the Large Intestine Colon Rectum Anus Structures of the Large Intestine saclike first part of the large intestine Appendix Accumulation of tissue that sometimes becomes inflamed (appendicitis) Hangs from the cecum Functions of the Large Intestine Absorption of and (most occurs in small intestine) Eliminates indigestible food from the body as feces ( ) Does not participate in of food

15 Functions of the Large Intestine cells produce mucus to act as a lubricant Intestinal bacteria ( ) live in large intestines, produce and some Accessory Digestive Organs Teeth participate in Organs not part of the alimentary canal; produce secretions carried by ducts Salivary Glands Saliva-producing glands glands located anterior to ears _ glands _ glands

16 Saliva Production of saliva stimulated by the thought, sight, smell and eating of food Mixture of and fluids Helps to form a food Contains to begin starch digestion (breaks starch down into smaller carbohydrates) Dissolves chemicals so they can be tasted Pancreas Both and functions Production of pancreatic juices (carried by duct into duodenum = function) neutralizes the acidic chyme from the stomach fluid contains enzymes for all food molecules ( carbohydrates, fats, proteins) Pancreas Endocrine products of pancreas Regulation of pancreatic secretion Cells of small intestine release hormones when food enters Secretin and CCK (cholecystokinin) Stimulate pancreas pancreatic juices

17 Liver Largest gland in the body Located on the right side of the body under the diaphragm Consists of lobes suspended from the diaphragm and abdominal wall by the falciform ligament Connected to the gall bladder via the Liver Hepatic portal circulation metabolic function Blood flows from digestive tract to liver carrying nutrients and toxins that the liver processes Digestive function production of (not an enzyme) Derived from Bile is involved in the of fats Bile Produced by cells in the Composition salts Bile pigment (mostly from the breakdown of ) Phospholipids Electrolytes

18 Liver Central roles of liver in metabolism Maintain proper level of nutrients in blood of poisonous substances Production of Also: Production of Destruction of Production of blood proteins Storage of fat soluble vitamins ( ) Gall Bladder Sac found in hollow fossa of liver Stores (and ) bile from the liver by way of the cystic duct Bile is introduced into the duodenum in the presence of CCK hormone released when fatty chyme enters small intestine; causes gall bladder to contract Gallstones can cause blockages Processes of the Digestive System getting food into the mouth moving foods from one region of the digestive system to another digestion Mixing of food in the mouth by the of food in the stomach _ in the small intestine

19 Processes of the Digestive System Chemical Digestion Enzymes break down food molecules into their building blocks in saliva; acts on starch in gastric juices; starts digestion of proteins found in pancreatic juice; acts on emulsified fats Intestinal juices (brush border cells) enzyme poor; enzymes to finish digestion Processes of the Digestive System Each major food group uses different enzymes Carbohydrates are broken to Proteins are broken to Fats are broken to and Processes of the Digestive System Absorption End products of digestion are absorbed in the or Food must enter mucosal cells and then into blood or lymph Defecation Elimination of substances as feces

20 Processes of the Digestive System Figure 14.11