UM 1011- GI Part 1-Upper GI PDF

GI: Gross Anatomy & Microanatomy UM1011-GI Block [email protected]  Learning outcomes  M1.I.GAS.ANA1: Describe the functional anatomy of the digestive tract (oral cavity, oesophagus, stomach, duodenum, jejunum, ileum, caecum and colon), accessory digestive organs...

GI: Gross Anatomy & Microanatomy UM1011-GI Block [email protected]  Learning outcomes  M1.I.GAS.ANA1: Describe the functional anatomy of the digestive tract (oral cavity, oesophagus, stomach, duodenum, jejunum, ileum, caecum and colon), accessory digestive organs (salivary glands, liver, gallbladder, pancreas) and the spleen.  M1.I.GAS.ANA2: Outline the major structures of the neurovascular supply to the gastrointestinal system.  M1.I.GAS.ANA3: Describe the organisation and clinical significance of the parietal and visceral peritoneum, the greater and lesser sacs, mesenteries and peritoneal ‘ligaments’.  M1.I.GAS.ANA4: Understand specific common clinical examples associated with the gastrointestinal system.  Introduction Digestive system carries out three primary processes: mixing food, moving food through the digestive tract (peristalsis) and using chemicals to break down food into smaller molecules. 2 organs of the digestive system: 1. Gastrointestinal (GI) tract or Alimentary canal A continuous coiled hallow tube (5-7 meters long) that extends from the mouth to the anus – runs through the thoracic and abdominopelvic cavities Organs: Mouth, most of pharynx, oesophagus, stomach, small & large intestine 2. Accessory digestive organs  Includes teeth, tongue, salivary glands, liver, gallbladder and pancreas. Part 1: Upper GI LECTURE OVERVIEW 1.1: Thoracic region 1.Oral region 2. Pharynx 3. Oesophagus 2.2: Abdominal region 1. Surface anatomy & Abdominal regions 2. Stomach 3. Small intestine- Duodenum 4. Pancreas 5. Liver 6. Biliary tree & gall bladder 7. Spleen 8. GI gut blood supply  What we will cover…  Functional anatomy of the oral region, oesophagus, stomach and duodenum.  Peritoneal cavity and its subdivisions.  Functional anatomy of the pancreas, liver and gall bladder  Upper GI, hepatic and pancreatic histology.  Their vascular supply. Nerve supply in part 2.  Oral region (Mouth) Point of food entry into the digestive system. Lips (labia) Cheeks Oral (buccal) cavity Teeth Gingivae Tongue (lingula) Palate: separates oral cavity from nasal cavity. Region of palatine tonsils  Oral (Buccal) cavity First part of the digestive system. Food and drinks are tasted. Mastication occurs (movement of jaw chewing), lingual manipulation and saliva from salivary glands– prepares food into bolus to be swallowed.  The oral cavity is divided into two parts: 1. Oral vestibule 2. Oral cavity proper Boundaries of the oral cavity Hard palate: Maxilla and palatine bone Tongue  Main function: articulation of words (speech) and food manipulation squeeze into pharynx.  3 parts: 1) Root, 2) body and 3) apex.  Dorsum has 2 surfaces: 1) Oral part (ant. 2/3) and 2) pharyngeal part (post. 1/3). Divided by V-shaped groove-terminal sulcus that meets at point as foramen cecum. Mucosa of anterior part is rough due to small lingula papillae – taste buds (receptors) located. Mucosa of posterior part – lingual tonsils (lymphoid nodules). Tongue  Inferior surface (underside) of tongue: Frenulum of tongue – connects tongue to floor of mouth. Sublingual folds with opening of sublingual ducts. Sublingual caruncle (papillae) with opening of the duct of the submandibular salivary gland. Clinical correlation: Food can sometimes get stuck in the opening and cause blockage of submandibular duct → swelling of salivary gland and inflammation.  Tongue  Mass of muscles covered by mucosa membrane. Made up of: Extrinsic muscles: alter the position Genioglossus – protrudes and retracts tongue (bilateral), deviates tongue (unilateral) Hyoglossus – Depress tongue Styloglossus – Elevates side of tongue Palatoglossus – Elevates posterior tongue and depresses soft palate to constrict the isthmus Intrinsic muscles: alter shape Superior & Inferior longitudinal Transverse Vertical Nerves of oral cavity  Five Cranial nerves in the oral cavity: CN 5, 7, 9, 10, and 12. (Will go in detail in Neuroendocrine block: Cranial nerves lecture). Salivary glands   Histology of salivary glands  Salivary glands are made up of secretory acinic and ducts. Parotid gland. Sublingual gland. Key: (SA)  2 types of secretions (saliva) – serous Mucous Secretory acini; (InD) intercalated ducts; CT loose connective tissue (isotonic watery fluid) and mucous (mucin lubricant).  Parotid glands mainly has serous acini.  Sublingual glands mainly has mucous acini.  Submandibular glands have a mixture of both types of acini. Submandibular gland Pharynx  Alimentary layer of the cervical viscera.  Extends from cranial base to C6 vertebrae  Has 3 parts: 1) Nasopharynx, 2) Oropharynx and 3) Laryngopharynx  A musculofascial (voluntary skeletal ms.) half-cylinder that connects the oral and nasal cavities in the head to the larynx and oesophagus of the neck.  Consists of external circular muscles (constrictors) and internal longitudinal muscles.  Although the pharynx conducts air to the larynx, trachea and lungs. The pharyngeal constrictor muscles direct food to the oesophagus in a complex three-stage process known as deglutition (swallowing).  Epiglottis is part of the larynx and deflects food from entering the trachea. Pharynx Oesophagus Trachea Posterior view of pharynx. Key: Yellow – Superior constrictor m.; Pink – Middle constrictor m.; Inferior constrictor m.  Oesophagus  Muscular tube (20-40cm long & 2cm wide) connects pharynx to the stomach.  Extends from C6 to T11.  Enters abdomen through hiatus in diaphragm at T10 level.  Relations and constrictions (‘ABCD’) Arch of aorta Bronchus (Left main bronchus) Cricoid cartilage Diaphragmatic (oesophageal) hiatus  2 sphincters at top and bottom of oesophagus: Upper oesophageal sphincter (anatomical) – Cricopharyngeus m. Lower oesophageal sphincter (physiological) – sphincter is maintained by several factors.  Oesophagus  Lower oesophageal sphincter is maintained by: 1. Oesophagus enters stomach at an acute angle creating cardial notch 2. Diaphragmatic musculature (right crus) has a “pinch-cock” effect. 3. Intra-abdominal section of the oesophagus are compressed when there is positive intra-abdominal pressure. Clinical correlates: Incompetent lower oesophageal sphincter can lead to Gastroesophageal reflux disease (GORDs).  Oesophagus Muscular tube made up of both skeletal and smooth muscle.  Upper 3 rd – skeletal m.  Middle 3 rd – mixture of skeletal and smooth m. fibres  Lower 3 rd – smooth m. Muscle layers:  Outer Longitudinal  Inner circular Functions to create peristaltic movement to push bolus food down towards stomach  Histology of GI tract General histology of GI tract, 4 basic layers: 1. Mucosa (inner most layer): consist of epithelium, lamina propria and muscularis mucosa 2. Submucosa 3. Muscularis externa 4. Serosa/adventitia – exhibits regional variations, reflecting the changing functions of the GI system from mouth to anus. Histology of oesophagus  Epithelium type: Stratified squamous epithelium (non- keratinised).  2 muscle layers (externa): Outer longitudinal Inner circular Innervation: Enteric nervous system (part of ANS) – Myenteric plexus Surface anatomy: Abdomen quadrants and regions ASIS  Abdominal cavity can be divided into either REGIONS or QUADRANTS.  Clinicians often use quadrants to explain pain location. Regions are used in describing location of abdominal organs.  PRE-LAB ACTIVITY: Abdominal regions A. Fill in the red boxes with the correct names for abdominal B. Fill in the table with the organs/tissue that you would find in each regions. regions. Right Hypochondrium Epigastric Left Hypochondrium Right Hypochondric Right Lumbar Umbilical Left Lumbar Transpyloric Subcostal plane (L1) plane (L2) Right Inguinal Pubic/Hypogastric Left Inguinal Left Inguinal Stomach  J- shaped organ. Capacity up to 3 litres.  Location: Epigastric and Umbilical regions. *can vary markedly in individuals and different body types, also moves during respiration and during empty vs. after heavy meals.  Intraperitoneal organ. Peritoneum and Peritoneal cavity Lesser sac also known as omental bursa Stomach  4 parts: Cardia, Fundus, Body, Pyloric part Pylorus at L1 vertebrae level- Transpyloric plane  Two curvatures: Lesser curvature Greater curvature  Transverse section at L1 vertebrae Stomach  Relations (surrounding viscera): Greater omentum Lesser omentum Liver Spleen Pancreas Left Kidney and supradrenal gland Transverse colon Diaphragm  Histology Stomach  Muscularis externa- three layered; unique to stomach allowing for vigorous contraction, churning Inner oblique layer Middle circular layer Outer longitudinal layer  Mucosa lining, thick (0.3-1.5mm) forms irregular longitudinal folds-rugae (internal feature of stomach). Rugae flattens when stomach expands.  Histology Stomach  Epithelium type (gastric): Simple columnar.  Epithelium forms gastric pits with gastric glands.  The gastric pits have mucous cells that produce mucous to protect the inner lining of the stomach.  Gastric glands are lined by: Parietal cells – HCI Chief cells-pepsinogen and chymosin Enteroendocrine cells – local hormones. Duodenum  C-shaped organ.  Location:; Umbilical region  Retroperitoneal organ.  4 parts: 1. Superior; 2. Descending; 3. Inferior; 4. Ascending.  Relations: Curves around head of pancreas. Duodenum: Internal features  Superior (1st) part – no circular folds. Lies at body of L1.  Other parts has circular folds (plicae circulares, valves of Kerkring) – large valvular flaps projects into the lumen Does not disappear when intestine distended. Circular folds slow the passage of food along the small intestine  Descending (2 nd) part – Extends between L2-L3 level. Major duodenal papilla – this is the opening of the bile and main pancreatic duct.  Ascending part (4 th ) part – Ends as duodenojejunal flexure as it continues as jejunum at L2 vertebrae level. Pancreas  Elongated, accessory digestive gland  Location: Epigastric, Left Hypochondrium  4 part: Head (with uncinate process), Neck, Body and Tail  Retroperitoneal except for at the tail.  Relations: Posterior to stomach. Between duodenum and spleen.  Histology of pancreas Has both exocrine and endocrine secretions.  Acinar cells – produce digestive enzymes; Exocrine part. Empties into 2nd part of duodenum via two excretory duct – larger main pancreatic duct and smaller accessory pancreatic duct. Q: Why does pancreas have an accessory duct?  Islet of Langerhans – produces hormones (Glucagon, insulin and somatostatin); Endocrine part. Liver  Largest gland in the body.  Location: Majority protected by thoracic ribs (deep to ribs 7- 11). Right hypochondrium, Upper epigastric, Left hypochondrium.  Intraperitoneal organ  Surfaces: Diaphragmatic surface – Mainly anterosuperior. Has bare area: direct contact with diaphragm (i.e no visceral peritoneum. Visceral surface – Posteroinferior. Has impression of other organs. Porta hepatis: Transverse fissure where hepatic vessels and ducts enter and leave liver or portal triad. Portal triad: Hepatic artery proper, hepatic portal vein and bile duct. Posterior-inferior view of the liver Liver  Anatomical lobes: 2 main lobes – Right and left. 2 accessory lobes – Quadrate and Caudate.  Functional lobes: 2 independent right and left lobes with the quadrate and caudate being a part of the functional left lobe. Each lobe receives its own primary branch of hepatic artery and hepatic portal vein and is drained by its own hepatic duct. Posterior-inferior view of the liver Liver  Ligaments of the Liver: Falciform ligament – free edge has ligamentum teres (remnant of umbilical vein) Coronary ligament (anterior and posterior folds) Triangular ligaments (Left and right) Lesser Omentum: Hepatogastric lig. and Hepatoduodenal lig. Hepatoduodenal lig. surrounds the portal triad. Liver  Ligaments of the Liver: Falciform ligament Coronary ligament (anterior and posterior folds) Triangular ligaments (Left and right) Lesser Omentum: Hepatogastric lig. and Hepatoduodenal lig. Hepatoduodenal lig. surrounds the portal triad.  Liver  Dual blood supply (afferent vessels – oxygenation): Hepatic artery Hepatic portal vein (HPV)  HPV main blood supply to the liver (75%) conveying absorbed nutrients from small and large bowel. Histology of Liver  Polygonal hepatic lobules – basic functional unit of the organ, formed by hepatocytes.  Periphery of the hexagon has 3 structures known as portal triad.  The direction of bile flow is opposite to blood.  Bile canaliculi are the smallest branches of the biliary tree.  Stellate macrophages – Kuffer cells; Phagocytose aged erythrocytes and foreign bacteria or viruses. Hepatic sinusoids – leaky endothelial walls; facilitates for greater contact with hepatocytes Biliary ducts & Gallbladder  Gall bladder: Intraperitoneal pear shaped-sac  Location: In fossa between inferior aspects of the right and quadrate lobes of the liver.  Bile formed by hepatocyte and is secreted into common bile duct until it reaches the sphincter of bile duct, if the sphincter closes, the bile is refluxed back into the gallbladder to be stored. Capacity – storage of bile 30-50 ml.  3 parts: Fundus, Body and Neck.  Biliary tree has intrahepatic and extrahepatic parts. Biliary ducts & Gallbladder  Extrahepatic bile passages and pancreatic ducts: 1. Sphincter of bile duct 2. Sphincter of pancreatic duct 3. Hepatopancreatic sphincter (Sphincter of Oddi) Spleen  Ovoid-shaped; largest lymphoid organ.  Location: Left hypochondrium under protection of the inferior thoracic cage.  Surfaces: Diaphragmatic surface and visceral surface  Relations: Stomach, tail of pancreas, diaphragm, left colic flexure and left kidney  Internal features: Red pulp – RBCs. Venous sinus, rich in macrophages – removes old and damaged erythrocytes, recycles iron from Hb. White pulp – WBCs. T- and B- Lymphocytes  Splenic venous sinuses – leaky endothelial walls; allows transport of cells Spleen  Ovoid-shaped; largest lymphoid organ.  Location: Left hypochondrium under protection of the inferior thoracic cage.  Surfaces: Diaphragmatic surface and visceral surface  Relations: Stomach, tail of pancreas, diaphragm, left colic flexure and left kidney  Internal features: Red pulp – RBCs. Venous sinus, rich in macrophages – removes old and damaged erythrocytes, recycles iron from Hb. White pulp – WBCs. T- and B- Lymphocytes  Splenic venous sinuses – leaky endothelial walls; allows transport of cells Derivative of the gut & blood supply   Blood supply: Abdominal viscera  Unpaired visceral arteries – branch from the abdominal aorta in the midline: 1. Celiac trunk (T12) 2. Superior mesenteric artery (L1) 3. Inferior mesenteric artery (L3)  Clinical correlates: Renal entrapment syndrome Blood supply: Celiac trunk and branches Celiac trunk:  Common hepatic artery Hepatic artery proper Right gastric artery Gastroduodenal artery Right Gastro-omental  Left gastric artery  Splenic artery Left Gastro-omental Short gastric arteries Dorsal pancreatic artery Inferior pancreatic artery