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Anatomy: ACCESSORY ORGANS OF DIGESTION Daniyal Sithawalla 1ILO’s ● Name and describe the anatomical arrangement, relations, blood supply and innervation of the salivary glands ● Describe the anatomical arrangement, relations, blood supply and innervation of the pancreas ● Describe the gross anatomy of the liver including its structure, relations, vascular supply and innervation ● Explain the flow of blood and bile through the liver lobule ● Explain the function of the hepatic portal system, describe the course of the portal vein, and discuss portal/systemic anatomoses ● Describe the anatomical arrangement, relations, blood supply and innervation of the bilary tree and gallbladder ● Describe the microscopic structure of the salivary glands, pancreas, liver and gall bladderSalivary Glands Glands: Parotid, Submandibular, Sublingual glands and accessory salivary glands over palate, lips, cheeks, tonsils, tongue ● Produce clear, tasteless, odourless saliva ● Keeps the mucous membrane of the mouth moist ● Lubricates the food during mastication ● Begins the digestion of starches ● Serves as an intrinsic mouthwash ● Plays significant roles in the prevention of tooth decay and in the ability to tasteParotid Gland ● Secretes SEROUS SALIVA from parotid duct open into oral cavity opposite second upper molar ● Facial nerve passes through (but does not innervate) ○ External carotid ○ Superficial temporal, maxillary arteries, superficial temporal maxillary, retromandibular veins also drain into it ● ECA gives rise to posterior auricular artery within gland ● Retromandibular vein formed within parotid gland ● Covered by prevertebral fascia/ investing layer of fascia ● Supplied by posterior auricular, superficial temporal arteries, both arising from ECA ● Drained byretromandibular veinParotid Gland Innervation (learning this isn't fun but just memorise it for the exam :)) ● Sensory innervation is supplied by the auriculotemporal nerve (branch of mandibular nerver), great auricular nerve ● Parasympathetic innervation: Glossopharyngeal nerve (CN9)→ synapse at otic ganglion → auriculotemporal nerve → parotid gland ○ This increases saliva production ● Sympathetic innervation: Superior cervical ganglion ○ Inhibits saliva secretion via vasoconstrictionSubmandibular glands ● Produces seromucous saliva ● It is the gland that is most likely to get blocked since it hooks ● Pair of glands, superficial and deep, hooks under mylohyoid muscle ● Secretions enter oral cavity via submandibular duct, open in as orifices on small sublingual papilla at base of lingual frenulum ● Supplied by: submental artery —> From facial artery which arises from ECA ● Drained by: Facial, submental vein —>From facial vein arising from IJVSubmandibular glands Innervation (autonomic): ● Parasympathetic by facial nerve : Superior salivatory nucleus → chorda tympani (CNVII) + Lingual branch of mandibular nerve (CNVI) → synapse at submandibular ganglion ● Sympathetic: Superior cervical ganglionSublingual gland ● Almond shaped that lie on floor of oral cavity, underneath the tongue ● Drain into oral cavity via sublingualpapillae Blood Supply: ● Supplied by sublingual, submental arteries ● Drained by sublingual, submental veins Innervation: ● Parasympathetic: Superior salivatory nucleus → chorda tympani (CNVII) + Lingual branch of mandibular nerve (CNVI) → synapse at submandibular ganglion ● Sympathetic: Superior cervical ganglionSalivary Glands ● Palatal, Buccal, Lingual (just need to know they exist not important) ● Von Ebner’s Gland - at the back of the tongue which produce mucous saliva to help tasteDuct Histology ● Intercalated ducts: Small, tiny lumen, simple low cuboidal epithelium (glands empty into it directly) ● Striated ducts: formed by merging intercalated ducts, simple columnar epithelium ● Intralobular ducts: Formed by merging striated ducts, gradually increasing in size and becoming surrounded by connective tissue ● Interlobular ducts: formed by merging intralobular ducts, epithelium may be pseudostratified ● Interlobar ducts: formed by merging interlobular ducts, pseudostratified or stratified epithelium, may possess cilia, convey saliva into oral cavityPancreasPancreas- An endo and exocrine organ Level of transpyloric plane, at level of L1,L2 bodies Retroperitoneal organ located deep within upper abdomen in epigastrium, left hypochondrium region Structure: ● Head: widest part of pancreas, lies within C shaped curve created by duodenum, borders the confluence of the superior mesenteric vein, hepatic portal ● Uncinate process: Projection arising from lower part of the head, lies posterior to superior mesenteric vessels ● Neck: Head and body of pancreas, overlies superior mesenteric vessels ● Body: Centrally located, crosses midline, lies behind stomach, left of superior mesenteric vessels ● Tail: Close proximity of hilum of pancreas, contained within splenorenal ligament with splenic vessels [this is the only intraperitoneal part]Pancreas Exocrinefunction 80% mass by function ● Acinar cells produce amylase, lipase, trypsin (proteases), nucleases to aid digestion ● Acinar cells produce inactive forms (proenzymes/zymogens) to prevent autodigestion ● Zymogens are also stored in zymogen granules (kept away from sensitive tissue and packaged with protease inhibitors, preventing enzymes from doing damage if prematurely activated Endocrinesecretions: Pancreatic islets of Langerhans directly into blood stream a. Endocrine function 20% mass by function b. Insulin: Beta cells c. Glucagon: Alpha cells d. Polypeptide: gamma cells e. Somatostatin: Delta cells [not that high yield except for the endocrine cells, memorise those]Pancreas ● Adjacent lobules unite, drain into network of intralobular collecting ducts → drain into main pancreatic duct ● Unites with length of common bile duct → becomes hepatopancreatic ampulla of vater ● Release enzymes into duodenum at ampulla vater via pancreatic ductPancreas (cant lie this is abit longto learn) Vasculature ● Supplied by pancreatic branches of splenic artery ● Head and Uncintate process supplied superior pancreaticoduodenal (branch of gastroduodenal) , inferior pancreaticoduodenal arteries (branch of superior mesenteric arteries) Venous drainage: Superior mesenteric branches of hepatic portal veinPancreas Innervation Involuntary innervation via the autonomic nervous system (ANS). Its parasympathetic innervation originates from the vagus nerve (CN X) and its sympathetic innervation from the greater and lesser splanchnic nerves (T5-T12). Both types of autonomic fibers travel until the celiac ganglion and superior mesenteric plexus, ultimately projecting onto the pancreas.Pancreas Lymph Drainage Body and tail of the pancreas via lymphatic vessels → pancreaticosplenic lymph nodes located along the splenic artery. The vessels draining the head empty into pyloric lymph nodes. Subsequently, lymph is transported to the superior mesenteric or celiac lymph nodeslymph nodes.Good to know may come out as a Sem test question -> read up in during your revision :)LiverLiver BordersLiver → Intraperitoneal Organ located in the right upper quadrant Function: ● Protein synthesis e.g albumin, clotting factors ● Glycogen storage ● Deamination ● Detoxification of xenobiotics, hormones, ingested drugs ● Bilirubin metabolism Surfaces: ● Diaphragmatic surfaces: Smooth, convex, beneath curvature of the diaphragm ● Visceral surface: Posterior inferior surface, covered with peritoneum less gallbladder, porta hepatisLiver ● Falciform ligament: Mesentery separates right, left lobes, suspending liver surface of diaphragm, anterior wall of abdominal cavity ● Round ligament (ligament teres): Fibrous cord, inferior to the falciform ligament. Remnant of fetal umbilical vein ● Ligamentum venosum: Fibrous remnant of fetal ductus venosus ● Coronary ligament: Attaches liver to inferior surface of diaphragm ● Right/left triangular ligament: right lateral surface of liver, upper left surface of liver ● Lesser omentum: Attaches liver to lesser curvature of stomach, first part of duodenum, consists of hepatogastric ligamentLiver Lobes (2 anatomical, 2 accessory) ● Right lobe: Largest, separated by falciform ligament, left sagittal fissure ● Left lobe: Smaller (anatomical lobe) ● Quadrate lobe: Accessory lobe, transverse porta hepatis separates it from caudal lobe ● Caudal lobe: Usually gives rise to a "tail" in the form of a long papillary processFunctional subdivisions of liver Porta hepatis contains: Hepatic artery, hepatic portal vein, common hepatic duct Each functional unit of the liver receives its own primary branch of porta hepatis, receiving blood from hepatic artery, drained by hepatic portal vein, hepatic duct Hepatic Veins do not exit the liver at the porta hepatitis Nerves pass through the porta hepatisLiver .Liver Sinusoids ● Mixing of portal vein, hepatic arterial blood ● Normal gaseous and other exchange ○ But hepatocytes also detoxify the blood, removing drugs and alcohol ● Lined with with leaky endothelial cells Portal blood ● Hepatic portal vein brings 75-80% of blood to the liver ● Portal blood contains 40% more O2 than blood returning to the heart ● Portal system receives blood supply from splenic and mesenteric veins ○ Receives all nutrients and toxins absorbed in the GI tractLiver vasculature ● Hepatic artery proper (25%): non parenchymal structures of liver with arterial blood, from common hepatic (celiac trunk) ● Hepatic portal vein (75%): Supplies with partially deoxygenated blood, carrying nutrients from small intestine, allows liver to perform gut related functions e.g detoxification ● 3 Central veins (right, intermediate, left)combine to form multiple hepatic veins, open into inferior vena cavaLiver vasculature (sry lads and ladies even though this is low yield IMO i was told to memorise this last year)Liver Innervation: ● Parenchyma innervated by hepatic plexus, which contains sympathetic (celiac plexus) and parasympathetic (vagus) nerve fibres ○ Sympathetic: Greater splanchnic ● Enter via porta hepatis Lymph: ● Anterior: hepatic lymph node ● Posterior: phrenic, posterior mediastinal node Which empties into Coeliac node → intestinal trunk → cysterna chylliGallbladderGallbladder ● Located in right hypochondrial region of abdomen ● Intraperitoneal, pear shaped sac ● Function: Concentrate and store bile, bile is released in response to cholecystokininGallbladder Fundus: Projects to midclavicular line Body: Largest part, adjacent to posteroinferior aspect of liver, transverse colon, superior part of duodenum Neck: Common place for gallstones to be lodged Bilesecretion Components: bile salts, phospholipids ● Cholesterol, bile pigments, bilirubin gives colour ● Bilirubin is a component of RBC degradationBiliary Tree ● Series of GI duct allowing newly synthesised bile from liver to be concentrated and stored in gallbladder ● Bile secreted from hepatocytes drains via intralobular ducts, collecting ducts into left and right hepatic ducts, amalgamate to form common hepatic ducts ● Joined by cystic duct, allows bile to flow in and out of gallbladder for storage and release ● Cystic duct + common hepatic duct combine to form common bile duct ● Gall bladder contracts in response to cholecystokinin → bile is released into common bile ducts ● Bile ducts lined with cholangiocytes, secrete bicarbonate rich fluid ● Combines with main pancreatic duct to form hepatopancreatic ampulla, empties into duodenum ● Sphincter of Oddi: Relax in the presence of cholecystokinin (produced in the presence of lipids) ○ Sphincter choledochus: Surrounds the common bile duct ■ Closure of sphincter where there are no fats present → bile backflows into cystic duct and become stored in gallbladder ○ Sphincter pancreatus: Surround pancreatic duct ○ Sphincter ampullae: Surround ampulla of vaterBile salts Amphipathic, have hydrophilic and hydrophobic parts ● Arranged itself in micelles (hydrophilic exterior, hydrophobic interior), allows little droplets of fat to settle within hydrophobic interior → emulsification of fat globules ● Micelles move lipid into brush border of intestinal cells where they diffuse out and absorbed through into intestinal villiGallbladder Vasculature ● Supplied by cystic artery (branch of hepatic artery) ● Drained by Cystic veins, which drain into portal vein Innervation ● Sympathetic: Greater splanchnic with postganglionic fibres from celiac plexus ● Parasympathetic: Vagus nerve Lymph ● Cystic lymph nodes, at neck of gallbladder -> hepatic node -> coeliac -> intestinal trunk -> cysterna chylli -> thoracic duct -> left subclavianHistology Pls have a look at Nazneen’s notion for Histology (life saver frfr) and 1med lectures!!!Do your anatomy wrap ups and Virtual Resources!!THANK YOU FOR LISTENING 39