Gastrointestinal Tract PDF

Gastrointestinal Tract Textbook of Diagnostic Sonography: Chapter 13. The Gastrointestinal Tract Sectional Anatomy for Imaging Professionals: Chapter 7. Abdomen Digestive System The digestive (or alimentary tract) is a tube, 8 m long, extending from the mouth to...

Gastrointestinal Tract Textbook of Diagnostic Sonography: Chapter 13. The Gastrointestinal Tract Sectional Anatomy for Imaging Professionals: Chapter 7. Abdomen Digestive System The digestive (or alimentary tract) is a tube, 8 m long, extending from the mouth to the anus which includes: Mouth Pharynx Esophagus Stomach Small intestine Large intestine Digestive System Accessory digestive glands secrete digestive juices into the digestive system include: Salivary glands Liver Pancreas The gastrointestinal tract is the part of the digestive system that is below the diaphragm Gastrointestinal Tract The gastrointestinal tract is the largest endocrine organ in the body Digestion and absorption are its main functions Food is ingested through the mouth, chewed, and swallowed When these particles are small enough, the nutrient molecules pass through the wall of the intestine into the blood or lymph system by absorption Gastrointestinal Tract The nutrients are transported to the liver after being absorbed by the blood; the liver processes and stores these nutrients The remaining nutrients in the blood are transported to the cells throughout the body The undigested and unabsorbed food is eliminated from the digestive tract by the process of defecation Gastrointestinal Tract When food enters the stomach, the rugae gradually smooth out, causing the stomach to stretch and increase its capacity for food intake Contractions of the stomach help mix the food Three layers of smooth muscle in the stomach wall enable it to mash and churn food and move it along with peristalsis Gastrointestinal Tract Large amounts of mucus are secreted in the stomach Gastric glands secrete gastric juice, which contains hydrochloric acid and enzymes Food is converted into chime This soupy mixture is moved toward the pylorus and into the small intestine Gastrointestinal Tract The villi within the small intestine increase its surface area for digestion and absorption of nutrients; without villi, food would move too quickly through the intestine for absorption The intestinal glands are found between the villi and secrete large amounts of fluid that serve as a medium for digestion and absorption of nutrients The hormone, gastrin, which is released by the stomach mucosa, stimulates the gastric glands to secrete their products Gastrointestinal Tract Most of the digestion occurs within the duodenum Bile and enzymes from the liver and pancreas are secreted into the duodenum to act on the chyme and break down the food particles for absorption Cholecystokinin is released by the presence of fat in the intestine and regulates gallbladder contraction and gastric emptying Secretin is released from the small bowel to stimulate the secretion of bicarbonate to decrease the acid content of the intestine Esophagus Extends from the pharynx through the thoracic cavity and diaphragm and empties into the stomach Lower end acts as sphincter; the entrance to stomach generally closed Stomach Large, smooth, muscular organ Two surfaces: Lesser Greater curvatures Three parts: Fundus Body Pylorus Stomach Stomach Ultrasound of Pylorus in an infant Ultrasound of Pylorus in an infant Normal Long Pylorus Normal Trans Pylorus Ultrasound of Pylorus in an infant Abnormal Long Pylorus Abnormal Trans Pylorus Ultrasound of Pylorus in an infant Normal Long Pylorus Abnormal Long Pylorus Coronal CT of Stomach Axial MRI of Stomach Small Intestine Long, coiled tube that measures approximately 5 m long and 4 cm in diameter Three parts: Duodenum Jejunum Ileum Ileocecal orifice marks the entry into the large intestine Small Intestine Small Intestine Duodenum Large Intestine Larger in diameter and shorter in length than the small intestine Five parts: Vermiform appendix Cecum Ascending Transverse Descending colon Rectum Anus Large Intestine Large Intestine Sonographic Evaluation of Bowel The bowel wall has five layers: 1. Mucosal layer (hyperechoic): The interface between the mucosa and the bowel lumen 2. Muscularis mucosae (hypoechoic): Has a variable thickness and represents the packed glandular tissue 3. Submucosa (hyperechoic): Contains connective tissue with vessels, nerves and fat 4. Muscularis propria (hypoechoic): An inner circular muscle layer and an outer longitudinal muscle layer 5. Serosa (hyperechoic): The visceral peritoneum  Sonographic Evaluation of Bowel The layers alternate their echogenicity from echogenic to hypoechoic Average total thickness of: 3 mm (if distended) 5 mm (if undistended) Sonographic Evaluation of Bowel Sonographic Evaluation of Bowel Image of Small Bowel Sonographic Evaluation of Bowel Haustra is the key feature of large intestine Sonographic Evaluation of Bowel Haustra is the key feature of large intestine Sonographic Evaluation of Bowel Haustra is the key feature of large intestine Coronal MRI Vermiform appendix Remnant of what was originally the apex of the cecum Long, tubular structure that extends from the cecum in one of several directions; it may lie: Superiorly behind the cecum Medially behind the ileum and mesentery Downward and medial into the true pelvis Vermiform appendix Located near the abdominal wall under McBurney’s point. Draw a line from the right anterosuperior iliac spine to the umbilicus At approximately the midpoint of this line lies the root of the appendix Vermiform appendix Normal Long Appendix Normal Trans Appendix Transverse CT of Cecum and Appendix