Digestive System Lecture Notes PDF

Chapter 24 Digestive System B305 – Human Anatomy Dr. Preston  Digestive System Function o Ingestion, transportation and break down of food: absorption of nutrients and expelling of wastes o Food mixed with saliva is a bolus o Stomach converts bolus into chyme © McGraw Hill...

Chapter 24 Digestive System B305 – Human Anatomy Dr. Preston  Digestive System Function o Ingestion, transportation and break down of food: absorption of nutrients and expelling of wastes o Food mixed with saliva is a bolus o Stomach converts bolus into chyme © McGraw Hill 2  Structure of the Digestive System Gastrointestinal (GI) tract – o Oral cavity, pharynx o Esophagus o Stomach, small intestine, large intestine, and anus Accessory digestive organs – o Teeth, tongue, salivary glands o Liver, gallbladder, and pancreas © McGraw Hill 3  General Anatomy Digestive Tract © McGraw Hill 4  Anatomy of the Digestive Tract o Open tract to environment at both ends o Material in tract considered to be external to body until it is absorbed by the epithelial cells o In a strict sense, defecated food residue was never in the body © McGraw Hill 5  Anatomy of the Digestive Tract Majority of digestive tract wall consists of layers: © McGraw Hill 6  Mucosa (mucous membrane) Inner epithelium o Simple columnar in majority o Stratified squamous (mouth Muscularis to esophagus, lower anal Mucosae canal) Lamina propria: loose connective Lamina propia Inner tissue layer Epithelium Muscularis mucosa: thin layer of smooth muscle o Creates grooves and ridges to enhance surface area © McGraw Hill 7  Submucosa o Thicker layer of loose Submucosae connective tissue o Contains blood vessels, lymphatic vessels, a nerve plexus o In some areas mucus- secreting glands that lubricate into the lumen © McGraw Hill 8  Muscularis Externa and Serosa Muscularis externa (motility): o Inner circular layer o Outer longitudinal layer Muscularis Serosa—composed of a thin layer Externa of areolar tissue topped by simple squamous mesothelium Serosa © McGraw Hill 9  Oral Cavity and Esophagus © McGraw Hill 10  Anatomy of the Oral Cavity Regions of oral cavity: Vestibule between cheeks or lips and gums Oral cavity proper central to alveolar processes of jaw bones © McGraw Hill 11  Salivary Glands o Parotid salivary glands: secrete 25 to 30% of saliva o Submandibular salivary glands: Produce 60 to 70% of saliva Figure 26.4 © McGraw Hill 12  The Esophagus o Straight muscular tube 25–30cm long o Begins: level between C6 and cricoid Esophagus cartilage o Extends from laryngopharynx to cardial orifice of stomach © McGraw Hill 13  The Esophagus o Passes through esophageal hiatus in diaphragm o Lower esophageal sphincter:  Constriction beyond hiatus  Prevents regurgitation © McGraw Hill 14  Normal Radiographic Images of the Esophagus Barium swallow tests © McGraw Hill 15  Normal Barium Test © McGraw Hill https://youtu.be/xlLnOSLoME4?si=zxvCMbq-ixUMonrv 16  Abnormal Radiographic Images of the Esophagus © McGraw Hill 17  Abnormal Radiographic Images of the Esophagus © McGraw Hill 18  Abdominal Regions and Quadrants © McGraw Hill 19  Anatomy of the Stomach Located in: o Upper left quadrant o Epigastric and left hypochondriac regions © McGraw Hill 20  Gross Anatomy of the Stomach Four regions: Cardia Fundus Body: Largest region Pylorus: Funnel- shaped terminal region © McGraw Hill (b) Victor P. Eroschenko 21  Gross Anatomy of the Stomach Internal surface of the stomach has gastric folds (rugae) Lesser curvature Pyloric region: Greater curvature © McGraw Hill (b) Victor P. Eroschenko 22  Clinical Anatomy – Stomach © McGraw Hill (b) Victor P. Eroschenko 23  Innervation and Circulation Stomach innervation: o Parasympathetic fibers from Vagus o Sympathetic fibers from Celiac ganglia Blood supply: o Branches of the Celiac trunk o Blood drained from stomach and intestines enters hepatic portal circulation and is filtered through liver before returning to heart © McGraw Hill 24  Small Intestines © McGraw Hill 25  The Small Intestine The longest part of the GI tract o About 5 m long in a living person o Up to 8 m long in a cadaver—no muscle tone o Diameter is about 2.5 cm (1 in.) © McGraw Hill 26  Gross Anatomy of the Small Intestine Divided into three regions: o Duodenum o Jejunum o Ileum © McGraw Hill 27  Small Intestine - Duodenum o Most duodenum is retroperitoneal (except first portion) o Begins at pyloric valve o Receives stomach contents, pancreatic juice, and bile o Duodenojejunal flexure – border between duodenum and jejunum Duodenojejunal flexure © McGraw Hill 28  Small Intestine - Jejunum Jejunum: first 40% of post-duodenum o Intraperitoneal o Rich blood supply which gives a red color Jejunum © McGraw Hill 29  Small Intestine - Ilium Ileum: last 60% of post- duodenal small intestine o Intraperitoneal Ileum o Ileocecal junction— where the ileum joins the cecum of the large intestine Terminal part of Ileum o Ileal papilla— protrudes into the cecum; regulates passage of food Ileal papilla residue into the large intestine © McGraw Hill 30  Gross Anatomy of the Large Intestine Begins as cecum inferior to ileal papilla Colonic regions: o Ascending colon, Right colic (hepatic) flexure, Transverse colon, Left colic (splenic) flexure, and Descending colon Left colic flexure Right colic flexure © McGraw Hill 31  Gross Anatomy of the Large Intestine Rectum: o Has three curves and three infoldings, called the transverse rectal folds (rectal valves) Anal canal: final 3 cm of the large intestine Passes through levator ani muscle and pelvic floor, terminates at the anus o Internal anal sphincter o External anal sphincter © McGraw Hill 32  The Liver © McGraw Hill 33  The Liver o Reddish brown organ located immediately inferior to the diaphragm o Right upper abdominal quadrant o The body’s largest organ (~ 1.4 kg (3 lbs) Functions: © McGraw Hill 34  Gross Anatomy of Liver Four lobes: o Right o Left o Quadrate o Caudate Caudate lobe Right lobe Left lobe Quadrate lobe © McGraw Hill 35  Gross Anatomy of Liver Ligaments: Falciform ligament o Separates left and right lobes Round ligament (ligamentum teres) Falciform Ligament o fibrous remnant of Round umbilical vein Ligament o Carries blood from umbilical cord to liver of the fetus © McGraw Hill 36  Gross Anatomy of Liver 2 Caudate lobe Hilum—irregular opening between quadrate and caudate lobes Left lobe o Entry of hepatic portal vein and proper hepatic artery o Exit for the bile ducts Hilum Gallbladder— inferior surface of the liver, between right and Quadrate lobe quadrate lobes © McGraw Hill 37  End of Main Content Because learning changes everything. ® www.mheducation.com © 2021 McGraw Hill. 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