Tractus Degestive Lecture 3 (2024) PDF

Structure and function of tractus digestivus (1) Integrated lecture: Department of Anatomy Department of Histology and Cell Biology Department of Physiology Faculty of Medicine, Public Health and Nursing Learning...

Structure and function of tractus digestivus (1) Integrated lecture: Department of Anatomy Department of Histology and Cell Biology Department of Physiology Faculty of Medicine, Public Health and Nursing Learning Objectives Explain structure and function of the upper and lower digestive tract. Explain gastrointestinal motility as a function of position and time Function of tractus digestivus to obtain necessary molecules from ingested food → maintenance, growth, and energy needs of the body as converter engine: from macromolecules to smaller molecules  What happens in tractus digestivus? Ingestion – introduction of food and liquid into the oral cavity (cavum oris) Mastication or chewing - divides solid food into digestible pieces Secretion of lubricating and protective mucus, digestive enzymes, acidic and alkaline fluids, and bile Motility – muscular movements of materials through the tractus Hormone release - for local control of motility and secretion Chemical digestion – enzymatic degradation of large macromolecules in food to smaller molecules and their subunits Absorption of the small molecules and water into the blood and lymph Elimination – of indigestible, unabsorbed components of food Working Diagram in the traktus digestivus Tractus digestivus - hollow tube - variable diameter - wall made of four main layers 1 3 2 4 Epithelium di tractus digestivus Labia oris & lingua: epithelium stratificatum squamosum with thin cornificatum Cavum oris Oesophagus epithelium stratificatum squamosum non cornificatum Gaster Epithelium simplex columnare Duodenum Enterocytus dengan microvilli Exocrinocytus caliciformis (Goblet cells) Jejenum Endocrinocytus gastroenteropancreatici (several types) Ileum Cellula panethensis (Paneth cells) Epitheliocytus microplicatus (M cells) Colon Lymphocytus Rectum Cellulae basale (stem cells) Anus: epithelium stratificatum squamosum non cornificatum Main layers of tractus digestivus, tunica mucosa Epithelium Stratificatum squamosum (non cornificatum) Simplex columnare Lamina propria Textus connectivus laxus Vasa sanguinea and lymphatica, glandula, nodulus lymphaticus (MALT) Lamina Muscularis mucosae 1 Myocytus nonstriatus/myocytus levis provide independent movement to increases the contact with food Main layers of tractus digestivus Tunica mucosa Tunica submucosa Textus connectivus plexus nervosus Tunica muscularis Myocytus non striatus plexus nervosus 1 Tunica serosa Textus connectivus Mesothelium  Plexus nervosus myentericus (Auerbach’s) and Plexus nervosus submucosus (Meissner’s) Connected to Related to systema nervosum Neuron tractus digestivus; local reflex Immune system Other cells in tractus digestivus Myocytus non striatus Endocrinocytus Cells in glandula intestinalis Immune cells (in lamina propria) Microbiome in lumen CNS: encephalon and medulla spinalis CNS: central nervous system  Plexus nervosus myentericus (Auerbach’s) and Plexus nervosus submucosus (Meissner’s) Related to systema nervosum Types Immune system Sensoric nerve ending Ganglion Parasympathetic ganglion n. vagus Second brain in intestinum: neuron in intestinum are more numerous than neurons in medulla spinalis Sympathetic nerve ending CNS: central nervous system Macrostructure of cavum oris Anatomi & Histologi Cavum oris Cavum oris (oral cavity) Epithelium stratificatum squamosum (cornificatum) Lingua myofibra striata non cardiaca in different directions 4 types of papilla lingualis Dens Glandula salivarii (in other topic) Epithelium stratificatum squamosum cornificatum and non-cornificatum Macrostructure of Lingua  Four types of papilla in lingua 8-12 most abundant numerous taste bud no taste bud largest papilla keratinized anterior sulcus terminalis not well developed in less abundant human some taste bud non-keratinized close to the tip of lingua Gemma gustatoria  Taste perception All location of lingua are capable of determining all types of taste. Some areas react faster than others.  Dens enamelum Corona dentis enamelum Cervix dentis dentinum Cavitas dentis Canalis radicis dentis Radix dentis dentinum Ligamentum Cementum with periodontalis cementocytus Gingiva The process of swallowing Macrostructure of Pharynx Macrostructure of esophagus  Microstructure of Esophagus Abundant mucus secreting gland called glandula esophageal could be observed on tunica submucosa Different proportion of myocytus of tunica muscularis Tunica muscularis esophagus 1/3 Proximal: myofibra striata non cardiaca 2/3 Distal: myocytus nonstriatus/myocytus levis Peristaltic Gaster secretion Gastric Motility 1. Receptive Relaxation When the bolus of food enters and causes distention of the stomach, a vagovagal reflex is initiated that causes relaxation of the orad region of the stomach, hence accommodating the ingested food. 2. Mixing and Digestion Slow/weak peristaltic constrictor waves – these waves are regulated by basic electric rhythm and occur every 3–5 minutes. Their function is to mix the gastric secretions and the food together and weak propulsion. Powerful peristaltic constrictor rings – this causes the contraction of the distal antrum, so when the weak peristalsis waves propel food towards the distal antrum, the power constrictor waves causes it to be propelled back (retropropulsion) therefore mixing the food in the process. 3. Gastric Emptying Two factors controlling the emptying of the stomach contents into the duodenum are the pylorus (which is usually tonically contracted, therefore controls stomach emptying) and antral peristalsis or pyloric pump (the peristaltic movements that cause the propulsion of chyme into the duodenum). https://step1.medbullets.com/gastrointestinal/106024/gastric-motility Macrostructure of Gaster Anatomi Stomach tissue have different configurations Transition from epithelium stratificatum squamosum non cornificatum to simplex columnare Microstructure of cardia & pylorus are similar → Mucus production The particular mucus serve as protection against gastric acid Cells of stomach wall Microstructure of fundus & corpus are similar → Gastric juice production Ruggae and foveola gastrica are special folds → different composing layers Glandula gastrica Exocrinocytus Fundus and principalis corpus Exocrinocytus parietalis Exocrinocytus parietalis Exocrinocytus principalis 35  endocinocytus gastroenteropancreatici: Hormone-secreting epitheliocytus found on those 3 organs fig. 1. Vosmaer et al., 2005 some book give name of the cell with alphabets (e.g) G : Gastrin/gaster D : Delta/somatostatin N : Neurostatin L : Cholecystokinin fig. 2. Vosmaer et al., 2005 Cellulae precursoria epithelialis (epithelial stem cell) reside on crypta intestinalis → Proliferation drove by Injury, hypoxia, ER Stress -> mitogenic signal → Differentiation process depends on extracelullar signal Glandula gastrica Fundus and corpus Exocrinocytus parietalis Exocrinocytus principalis  Structure and function of tractus digestivus (2) Integrated lecture: Department of Anatomy Department of Histology and Cell Biology Department of Physiology Faculty of Medicine, Public Health and Nursing Macrostructure of duodenum  Microstructure of duodenum - 2 layers of myocytus - Appearance of villi intestinales - Abundant mucus-producing glandula duodenalis (Brunner)  Work & Output in the duodenum After bolus mixed with stomach acid, becoming chymes, then the next steps are: → they move into the duodenum → they mix with bile from the gallbladder → they mix with digestive juices from the pancreas. → the absorption of vitamins, minerals, and other nutrients begins. Motility and structure in duodenum  Macrostructure of jejunum dan illeum  Structure of jejunum Plica circulares and vili intestinalis both serve to increase surface area → maximise contact absorption Glandula/ crypta intestinalis consist of various cell type  Epithelium simplex columnare Enterocytus (columnar cells with microvilli) Epitheliocytus caliciformis (goblet cells) Endocrinocytus gastroenteropancreatici (several types) Cellula panethensis (Paneth’s cells) Epitheliocytus microplicatus (M cells) Lymphocytus Cellulae basale (stem cells) Absorption of nutrition Increase surface area*: microvilli Defense to pathogen Barrier function (intercellular junctions and mucous layer) Antimicrobial substance antigen sampling#, immune effector cells & *together with plica dan villi # can be done by other cell transpor immunoglobulin (block A.6) https://www.researchgate.net/figure/Neuroendocrine-cell-differentiation-in-the-gastrointestinal-tract-Basal-crypt-stem_fig3_49792209 regulation & coordination 46 Enterocytus: main cell in epithelium intestinum; barrier function; absorption Zonula occludens: prevent the leak of the lumen to the wall. Disturbed by toxin exposure and changes in microbiota composition Zonula adherens Desmosoma Microvilli: increase surface area (20x), microfilamentum in cytoplasm Cellula panethensis Villi intestinales (Paneth cells) – main source of antimicrobial peptides and stabilize the stem cell zone. Epitheliocytus caliciformis (Goblet cells): mucin secretion Endocrinocytus gastroenteropancreatici: produce signal molecules Epitheliocytus microplicatus (M cells) transport antigen from lumen to lamina propria The base of crypta intestinales  Motility and process in jejunum Sites of absorption of diet constituents and secretions in the intestinal tract: # Fat, protein, carbohydrates, vitamins, and trace elements are mainly absorbed in the proximal jejunum. # Bile acids and vitamin B12 are absorbed exclusively in the ileum ← the life site of microbiota! # Water and electrolyte absorption takes place in both the large and small intestines https://www.researchgate.net/publication/282211844_Short-Bowel_Syndrome_in_Dogs_and_Cats/figures?lo=1 Microstructure of Ileum Vili Intestinalis appeared to be shorter than jejunum Plaques Peyers can be observed on tunica submucosa→ lined with special tunica mucosa configuration to facilitate antigen sampling from lumen  Process in ileum The ileum helps to further digest food coming from the stomach and other parts of the small intestine. It absorbs nutrients (vitamins, minerals, carbohydrates, fats, proteins) and water from food so they can be used by the body. The small intestine connects the stomach and the colon. Vitamins A, D, E, and K, fats, and cholesterol are absorbed in the lower third of the ileum. Vitamin B12 is absorbed just before the small intestine joins the large intestine. Bile salts are reabsorbed in the distal ileum and the ascending colon https://doctorlib.info/physiology/medical-physiology-molecular/46.html Motility and process in colon Macrostructure of colon Anatomi & Histologi  Microstructure of colon Abundant exocrinocytus caliciformis and colonocytus (absorptive cells) observed on tunica mucosa, Distinctive third muscular layer → taeniae coli Macrostructure of rectum & Anus Anatomi &  Rektum & Anus Rectum to Anus: Simplex Columnare to AG: Glandula anal (tubuloacinar) Stratificatum squamosum IASM: internal anal sphincter muscle *: anal sinus → : ductus excretorius glandula analis Defecation Thank You