The Anatom Digestive System We need food for cellular utilization: →nutrients as building blocks for synthesis →sugars, etc to break down for energy most food that we eat cannot be directly used by the body too large and complex to be absorbed →chemical composition must be modified to be useable by cells Functions of Digestive System: 1. physical and chemical digestion 2. absorption 3. collect & eliminate nonuseable components Anatomy of Digestive System organs of digestive system form essentially: a long continuous tube open at both ends → alimentary canal (gastrointestinal tract) mouth →pharynxesophagus stomach→→small intestine→→large intestine attached to this tube are assorted accessory organs and structures that aid in the digestive processes salivary glands teeth liver gall bladder pancreas mesenteries The GI tract (digestive system) is located mainly in abdominopelvic cavity surrounded by serous membrane visceral peritoneum this serous membrane is continuous with parietal peritoneum and extends between digestive organs as mesenteries → hold organs in place, prevent tangling The wall of the alimentary canal consists of 4 layers: serosa: visceral peritoneum, outer mainly fibrous and areolar CT muscularis several layers of smooth muscle submucosa blood vessels, lymphatic vessels, nerves, connective tissue inner mucosa: mucous membrane lining these layers are modified within various organs → some have muscle layers well developed → some with mucous lining modified for secretion of digestive juices → some with mucous lining modified for absorption 1. Mouth (Buccal Cavity, Oral Cavity) bordered above by hard and soft palate forms partition between mouth and nasal passages fauces opening of buccal cavity into throat uvula is suspended from rear of soft palate blocks nasal passages when swallowing tongue lines ventral border of mouth cavity is skeletal muscle covered with mucous membrane rough elevated projections = papillae types of papillae: fungiform, foliate, vallate on some are taste buds frenulum is thin fold of mucous membrane on ventral surface of tongue that anchors the tongue to the floor of the mouth short frenulum → "tongue tied" two sets. deciduous (=baby teeth) 20 begin at 6 months; shed 6-13 yrs permanent teeth. 32 each tooth has a crown (above gum) and a root (below gum) neck is the line where crown, gum and root meet imbedded in socket = alveolus gingivitis = inflammation of gum surrounding teeth; can lead to periodontal disease kinds of teeth modified for specific functions incisors -cut, knip canines -holding onto prey premolars -cutting, crushing molars -chewing, grinding, crushing each tooth is composed of several layers: enamel very hard outer surface on upper exposed crown only not living tissue, noncellular secretion deposited before tooth erupts from gum resists bacterial attack cannot regenerate if damaged dentin below enamel living connective tissue with cells that line pulp cavity: that send processes into the calcified matrix through: tiny parallel tubes less hard, similar to bone matrix decays quickly of enamel is penetrated pulp living portion of tooth consists of blood vessels, nerves cementum on root of tooth only outer surface living connective tissue with cells in lacunae holds root into socket in jaws Salivary Glands 3 Pairs of salivary glands: sublingual submandibular parotid largest, below ears mumps = acute infection of parotid gland secrete saliva (enzymes and mucous for digestion) 2. Pharynx (throat) already discussed 3. Esophagus collapsible tube 10" long extends from pharynx to stomach →gets food through thorax to abdominal cavity pierces diaphragm posterior to trachea and heart uses peristalsis to move food to stomach → can swallow upsidedown 4.consists of blood vessels, nerves cementum on root of tooth only outer surface living connective tissue with cells in lacunae holds root into socket in jaws Salivary Glands 3 Pairs of salivary glands: sublingual submandibular parotid largest, below ears mumps = acute infection of parotid gland secrete saliva (enzymes and mucous for digestion) 2. Pharynx (throat) already discussed 3. Esophagus collapsible tube 10" long extends from pharynx to stomach →gets food through thorax to abdominal cavity pierces diaphragm posterior to trachea and heart uses peristalsis to move food to stomach → can swallow upsidedown 4. Stomach muscular sac just below diaphragm and liver alimentary canal expands to form stomach divided into regions: fundus body pyloris muscular sac just below diaphragm and liver alimentary canal expands to form stomach divided into regions: fundus body pyloris Muscle layers are very well developed in stomach circular longitudinal oblique Help to break up food by churning action results in milky white liquid chyme sphincter muscles close both stomach openings cardioesphageal sphincter pyloric sphincter within the mucous lining of stomach are glandular tubes called gastric pits →within gastric pits are numerous microscopic gastric glands: epithelial cells secrete mucous for protection chief cells secretes various digestive enzymes parietal cells secretes HCI 5. Small Intestine longest part of alimentary canal: → 1" diameter x 10' long (living) or 20' long (cadaver) small intestine fills most of abdominal cavity held in place by mesenteries (=serous membranes) subdivided into 3 functional regions: duodenum 10" long uppermost drains pyloric stomach receives ducts from gall bladder and pancreas jejunum 8' central portion mostly in umbilical region ileum 12' mainly in hypogastric region joins to caecum of large intestine 6. Large Intestine 2.5" diameter x 6' long valve like sphincter separates small from large intestine = ileocecal valve subdivided into 3 regions: cecum blind ended sac that extends from point of attachment to small intestine contains appendix~3.5" (9cm) long significant source of lymphocytes herbivorous primates such as gorillas and orangutans have an enormous cecum packed with bacteria that digest plant fiber colon subdivided into: ascending colon transverse colon descending colon sigmoid colon rectum last 7-8" ends at anus external anal sphincter of skeletal muscle 7. Serous Membranes body wall and organs of abdomen are lined with peritoneum →parietal peritoneum →visceral peritoneum most, but not all, of the visceral organs are completely lined with visceral peritoneuileum 12' mainly in hypogastric region joins to caecum of large intestine 6. Large Intestine 2.5" diameter x 6' long valve like sphincter separates small from large intestine = ileocecal valve subdivided into 3 regions: cecum blind ended sac that extends from point of attachment to small intestine contains appendix~3.5" (9cm) long significant source of lymphocytes herbivorous primates such as gorillas and orangutans have an enormous cecum packed with bacteria that digest plant fiber colon subdivided into: ascending colon transverse colon descending colon sigmoid colon rectum last 7-8" ends at anus external anal sphincter of skeletal muscle 7. Serous Membranes body wall and organs of abdomen are lined with peritoneum →parietal peritoneum →visceral peritoneum most, but not all, of the visceral organs are completely lined with visceral peritoneum when an organ is lying against the dorsal body wall and is covered by serosa on the ventral side only = retroperitoneal eg. duodenum, most of pancreas, parts of large intestine these layers are continuous with thin flaps of serous tissues mesenteries mesenteries allow free movement while holding organs in place and prevent them from tangling greater omentum fold of mesentery extending from stomach and duodenum loosely covers the small intestine like an apron contains fat deposits lesser omentum smaller fold of mesentery between liver and stomach Accessory Organs of Digestive Tract A. Liver is the largest gland in body lies immediately under the diaphragm consist of 2 lobes separated by falciform ligament B. Gall Bladder lies on undersurface of liver →gall bladder stores and concentrates bile C. Pancreas most digestion is carried out by pancreatic enzymes in curve of duodenum and dorsal to greater curvature of the stomach composed of 2 kinds of glandular tissue: endocrine secretes hormones islets 2% of total mass of pancreas their secretions pass into circulatory system2 secrete insulin and glucagon exocrine digestive function pancreatic digestive secretions are collected in pancreatic duct when an organ is lying against the dorsal body wall and is covered by serosa on the ventral side only = retroperitoneal eg. duodenum, most of pancreas, parts of large intestine these layers are continuous with thin flaps of serous tissues mesenteries mesenteries allow free movement while holding organs in place and prevent them from tangling greater omentum fold of mesentery extending from stomach and duodenum loosely covers the small intestine like an apron contains fat deposits lesser omentum smaller fold of mesentery between liver and stomach Accessory Organs of Digestive Tract A. Liver is the largest gland in body lies immediately under the diaphragm consist of 2 lobes separated by falciform ligament B. Gall Bladder lies on undersurface of liver →gall bladder stores and concentrates bile C. Pancreas most digestion is carried out by pancreatic enzymes in curve of duodenum and dorsal to greater curvature of the stomach composed of 2 kinds of glandular tissue: endocrine → secretes hormones islets 2% of total mass of pancreas their secretions pass into circulatory secrete insulin and glucagon exocrine digestive function pancreatic digestive secretions are collected in pancreatic duct Name: Description: ...