University:
Northwest College
Course:
ANT 201 | Anatomy
Academic year:

2023
Views:

468

Pages:

66
Author:

Yesenia M.

Functions • Motility • Secretion • Digestion • Absorption Components of the Digestive System Components • Oral cavity • Alimentary Canal • Accessory organs – teeth salivary glands liver gall bladder pancreas appendix Digestive Tract ( G.I. tract) Terminology •Ingestion •to take in food •Mastication •chewing (mechanical breakdown of food) •Deglutition •swallowing •Digestion •chemical breakdown of food •Absorption •passage of nutrients from the gi tract lumen to the blood •Peristalsis •Waves of smooth muscle contraction to propel food •Defecation •formation and excretion of solid waste Digestive tract tunics Digestive tract tunics Mucosa • Absorptive layer, large surface area • 3 major components – mucosal epithelium • columnar epithelium (stomach, intestines) or stratified squamous • Crypts of Leiberkuhn – folds in the mucosa, source of new epithelial cells – lamina propria • loose CT of the mucosa, with capillaries that receive absorbed nutrients • lymphatic tissue: capillaries and lymphatic nodules involved in absorption of fat • Peyer’s Patches: aggregates of lymph nodes, significant protection against intestinal infections – muscularis mucosae • a thin layer of smooth muscle that keeps the folds of the mucosa folded Submucosa, Muscularis Externa, Serosa • submucosa – tissue: dense irregular CT – Meissner’s plexus • nerve supply to the muscularis mucosae • muscularis externa – mainly a double layer of smooth muscle, propels and mixes digestive contents • circular layer: thick inner layer, muscle fibers describe a circle • longitudinal layer: thin outer layer, muscle fibers run along the length of the GI tract – Auerbach’s plexus: nerve supply to the muscularis externa • Serosa – loose CT + simple squamous epithelium – outer wall of the GI tract, visceral peritoneum, Mouth and Pharynx • Tongue – a muscular soft organ, involved in moistening/mixing food, taste, speech • lingual tonsils – aggregates of lymph nodes located on the posterior/superior aspect • frenulum linguae – an inferior attachment of the tongue to the lower jaw • Papillae – microscopic folds in the tongue containing taste buds epiglottis mouth pharynx tongue The Tongue • • • • • Body Root Papillae Taste buds Frenulum Teeth • • • • • • Neck Crown Gingivae Enamel Dentine Pulp cavity – Apical foramen • Periodontal ligaments • Cementum Characteristics of human teeth • Heterodont dentition-( variations in the shapes of the types of teeth ie bicuspid vs. molars. ) • Diphyodont – 2 sets of teeth within 1 life time • dental formulas – ( I - C - P - M in each quadrant): Deciduous teeth I - C- P- M 2- 1- 0- 2 2- 1- 0- 2 Permanent Teeth I - C- P- M 2- 1- 2- 3 2- 1- 2- 3 Sublingual submandibular salivary glands • release water, lysozyme, digestive enzymes, mucus • Locations – buccal: in cheeks – parotid: largest, anterior to the ear (pure serous) – submandibular (submaxillary): medial to mandible (contain serous/mucus cells) – sublingual: inferior aspect of the tongue Serous and mucous cells Mesentaries • Sheets of serous membrane that connect the parietal and visceral peritoneum – Suspends organs in the space – Provides a route for blood vessels, nerves, lymphatics • • • • • • Lesser omentum Greater omentum Mesentery proper Mesocolon Transverse mesocolon Sigmoidal mesocolon • The greater omentum connects the stomach to the colon. Greater Omentum Esophagus • function – move food to the stomach • lining epithelium – stratified squamous • M u s c le layer – 1st third • skeletal muscle – 2nd third • a mixture of skeletal and smooth muscle – 3rd third • smooth muscle Stomach • a large, muscular distensible portion of the GI tract • Functions – food storage – initiates protein digestion – kills bacteria – moves food to S I – intrinsic factor Anatomical structure of stomach • 3 layers of smooth muscle – longitudinal, circular and oblique • Rugae – macroscopic folds in the stomach, luminal lining – flatten when the stomach is full – Also in gall bladder and urinary bladder Histology of stomach • lining epithelium – simple columnar epithelium – Microvilli increase surface area • gastric glands – microscopic folds, secrete gastric juice. • gastric pits – openings from gastric glands to gastric lumen Types of cells – 1) chief (zymogenic) cells • secrete pepsinogen – 2) parietal cells • secrete HCl – 3) goblet cells • secrete mucus – 4) G-cells • secrete hormones to support stomach activity Small intestine • ~3 meters long • Function – Digestion and absorption • 3 histologically different regions – Duodenum – Jejunum – Ileum Duodenum • Length – Approx 25 cm • Function – 95% of digestion and absorption • surface area – 600x’s its length = 15000cm, 150m or approx 138 yards! Note the Brunner’s glands in the submucosa Surface area • Plicae circularis – macroscopic permanent folds (permanent until death) – Circular pleats like conduit • Villi – fingerlike projections • Microvilli – submicroscopic folds on apical surface of columnar cells – “brush border” Paneth Cells • Highly specialized secretory epithelial cells • Located in the small intestinal crypts of Lieberkühn. • The dense granules produced by Paneth cells contain an abundance of antimicrobial proteins that function to regulate the composition of the intestinal flora. ( SEE NEXT SLIDE) Villi and microvilli capillary arteriole lacteal Ampullae • enlargements allowing for openings from pancreatic and bile ducts • Hepatopancreatic duct – Ampulla of Vater – Sphincter of Oddi • Accessory duct – Duct of Santorini Jejunum • 1 m long • histologically similar to duodenum, but lacking Brunner’s glands • completes digestion and absorption started in the duodenum Ileum • 2m long • mainly water, mineral, vitamin absorption Large intestine • regions (7) – Cecum – Ascending – Transverse – Descending – Sigmoid – Rectum – Anus Large intestines • Approx 1.5 mlong • lining epithelium – Predominately simple columnar – stratified squamous in the anal canal • haustra – sacs or pouches seen along the length of the large intestine – haustral churning • contraction of the haustra • mixes feces, max absorption of water • taenia coli – 3 distinct bands of smooth muscle (longitudinal) running the length of the large intestine Histology of large intestines • Many Crypts of Lieberkuhn without Paneth cells • Increasing number of goblet cells as move from cecum to rectum Histological comparison between small and large intestines Rectum and anus • Rectum – stores feces until defecation – Characterized by deep crypts of Lieberkuhn • Anus – contains 2 sphincter muscles controlling passage of feces to the exterior. – Mucosa transitions from simple cuboidal to stratified squamous nonkeratinized to stratified squamous keratinized at anus Appendix • 5-6 cm long • an extension of lymphatic tissue near the ileocecal junction Anal Canal More Accessory Organs… Functions of Liver • Bile production and secretion • Detoxication of blood • Secretion of glucose, triglycerides, ketone bodies • Plasma protein production Gross Anatomy of Liver Lobes: Left, Right, Cuadate, Quadrate Posterior aspect Gross anatomy of the liver, anterior aspect Ligaments • falciform ligament – suspends liver from diaphragm • ligamentum teres hepatis – extends from falciform ligament to umbilicus (remnant of umbilical vein) Liver Lobules • hepatic plates – arrangement of hepatocytes around the central vein • hepatocytes • central veins – from the hepatic portal vein to hepatic veins • bile canaliculi – from hepatocytes to duodenum Histology of the liver Movement of blood and bile through the liver gall bladder • small distensible organ • stores bile • bile ducts – hepatic – cystic – common bile Pancreas pancreas • acinar cells – exocrine – secrete most – digestive enzymes – and bicarbonate • pancreatic islets – Islets of Langerhans – endocrine – secrete hormones (insulin and glucagon) • pancreatic ducts – collect enzymes, bicarb, pass them onto the duodenum