Presentation on theme: "Anatomy of the Digestive System"— Presentation transcript:
1Anatomy of the Digestive System Lab Exercise 26Anatomy of the Digestive SystemPortland Community CollegeBI 233
2Digestive SystemAlimentary Canal: hollow tube extending from mouth to anusTechnically outside the bodyCovered with mucous membraneAccessory digestive organs – teeth, tongue, gallbladder, salivary glands, liver, and pancreas
3DigestionProcess by which foods are broken down into simpler forms so that nutrients can be delivered to all areas in the body.Ingestion chewing muscular actions Enzymatic breakdown absorption excretion
4Membranes Parietal Peritoneum: Covers the wall of the abdominal cavity Visceral Peritoneum: Covers the outside of all the abdominal organsMesentery: a fold of peritoneum attaching the small intestine to the posterior abdominal wallGreater Omentum: Thick sheet of tissue (lots of fat) that hangs off the greater curvature of the stomachLesser Omentum: Anchors the liver to the lesser curvature of the stomachMesocolon: a fold of peritoneum attaching the colon to the posterior abdominal wall
9Oral Cavity The lips surround the anterior opening. Consist of skeletal muscle covered with skin.Posteriorly, the fauces is the opening leading to the oropharynx.Cheeks form the lateral walls.The tongue occupies the floor
10Tongue Composed of skeletal muscle. Intrinsic tongue muscles are important for changing the shape of the tongue while speaking and swallowing.Extrinsic tongue muscles are connected to hyoid bone and styloid process of temporal bone.
11Teeth Gingiva is the mucous membrane (gums) Each region of a tooth is identified according to its relationship to the gingival margin (gum line)Crown is visible portionRoot is below gum lineNeck is between
12Teeth Incisor (cutting) Canine (tearing) Adults have 32 teethChildren have 20 deciduous teethIncisor (cutting)Canine (tearing)Premolar (tearing and grinding)Molar (grinding)
13Salivary GlandsParotid: Primarily serous with salivary amylase Sublingual: Primarily secrete mucousSubmandibular: Smallest of the salivary glands secrete both serous and mucous fluids
20Small Intestine: Gross Anatomy Runs from pyloric sphincter to the ileocecal valveHas three subdivisions: duodenum, jejunum, and ileumThe bile duct and main pancreatic duct:Join the duodenum at the hepatopancreatic ampullaAre controlled by the sphincter of OddiThe jejunum extends from the duodenum to the ileumThe ileum joins the large intestine at the ileocecal valve
21Small Intestine Minor papilla Plica Circularis Ileum Duodenum C-Loop Major papilla
25Large Intestine Is subdivided into the The saclike cecum: Cecum AppendixColonRectumAnal canalThe saclike cecum:Lies below the ileocecal valve in the right iliac fossaContains a wormlike vermiform appendixIleum
26Large Intestine Hepatic Portal Vein Aorta Superior Mesenteric Artery Inferior Mesenteric ArteryIleocecal valve is in hereCecumAppendixIleum
27ColonHas distinct regions: ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, and sigmoid colonThe sigmoid colon joins the rectumThe anal canal, the last segment of the large intestine, opens to the exterior at the anus
29Valves and Sphincters of the Rectum and Anus Three valves of the rectum stop feces from being passed with gasThe anus has two sphincters:Internal anal sphincter composed of smooth muscleExternal anal sphincter composed of skeletal muscleThese sphincters are closed except during defecation
32Liver The largest gland in the body Superficially has four lobes – right, left, caudate, and quadrateThe falciform ligament:Separates the right and left lobes anteriorlySuspends the liver from the diaphragm and anterior abdominal wall
34GI Tract Histology 2. Submucosa All of the hollow organs have the same basic 4 layers.1. Mucosa (Lumen side)Epithelial layer (remember from 231: stratified squamous, columnar ect…)Lamina Propria: Base made of loose areolar connective tissueMuscularis Mucosa: Base of smooth muscle fibers2. SubmucosaDense irregular connective tissueThis is where the blood vessels, nerves and the glands are.
35GI Tract Histology 3. Muscularis Externa The main smooth muscle layer used for peristalsisLongitudinal and Circular layers with myenteric plexus (parasympathetic ganglion) in between4. Serosa (Abdominal cavity side)Epithelial layer (usually simple squamous)Also known as the visceral peritoneum
47Lamina propriaLumen of pitParietal cellChief cellEntroendocrine (G cell)
48Small Intestine: Histology Structural modifications of the small intestine wall increase surface areaPlica circularis: Transverse folds on the mucosaVilli: Fingerlike extensions of the mucosaMicrovilli (Brush border): Tiny projections of absorptive mucosal cells’ plasma membranes
50Small Intestine Histology: Mucosa Plicae circulares: Large deep, permanent folds of the mucosa and submucosa.Slow the movement of chyme (more time for digestion/absorption) and increase the surface area.
52Small Intestine Histology: Villi Villi: Fingerlike projections of the mucosa.Made of simple columnar epitheliumIncrease the surface area.Within the core of each villus is a capillary bed and a lacteal for transport of the absorbed nutrients
54Small Intestine Histology: Mucosa Microvilli: Tiny projections of the plasma membrane of the simple columnar absorptive cells.Often called the "brush border" due to their appearance.They further increase the available surface area and contain membrane-bound enzymes involved in digestion.
57Crypts of LiberkühnPaneth cells in a Crypt of Lieberkühn secrete lysozymes
58Small Intestine Histology: Submucosa with Brunner’s Glands Brunner’s glands in the proximal duodenum secrete alkaline mucusBrunner’s glands
59Small Intestine Histology: Submucosa with Peyer’s Patches Peyer’s patches are found in the submucosa of ileumLymphoid tissue
60Large Intestine: Histology Colon mucosa is simple columnar epithelium except in the anal canalHas numerous deep crypts lined with goblet cellsAnal canal mucosa is stratified squamous epitheliumSuperficial venous plexuses are associated with the anal canal
64Anal Canal HistologyAt the junction of the rectum and anus, the histology of the mucosa changes to stratified squamous
65Liver HistologyHexagonal-shaped liver lobules are the structural and functional units of the liverComposed of hepatocyte (liver cell) plates radiating outward from a central vein (flows toward hepatic vein)Portal triads are found at each of the six corners of each liver lobulePortal triadsBile ductHepatic artery – supplies oxygen-rich blood to the liverHepatic portal vein – carries venous blood with nutrients from digestive viscera
66Liver HistologyLiver sinusoids – enlarged, leaky capillaries located between hepatic platesKupffer cells – hepatic macrophages found in liver sinusoids
70Liver Brach of Portal Vein Bile Duct Hepatocytes Branch of Hepatic Artery
71Pancreas Exocrine function: Acinar cells Secretes pancreatic juice which breaks down all categories of foodstuffAcini (clusters of secretory cells) contain zymogen granules with digestive enzymesEndocrine function: Islets of LangerhansRelease of insulin and glucagon