Anatomy and Physiology of Digestion.doc

48 Pages
69 Views
Unlock Document

Department
Kinesiology
Course
KINESIOL 1F03
Professor
Danny M.Pincivero
Semester
Fall

Description
34 ANATOMY AND PHYSIOLOGY OF DIGESTION DIGESTIVE SYSTEM 2 main groups: 1) Alimentary canal • Gastrointestinal tract – starts at stomach through intestines • Continuous digestive tube through whole body Function: A) Digestion • breaks food into smaller fragments B) Absorption • moves the digested fragments from the alimentary canal into the blood • macronutrients, micronutrients have to be broken up small enough to retrieve nutrients • Anatomical structures • Mouth (lips, cheeks, palate, tongue, teeth, salivary glands) • Pharynx • Esophagus • Stomach (cardiac orifice, fundus, body, pyloric canal, pylorus, pyloric sphincter, omentum) • Small intestine (duodenum, jejunum, ileum) – KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 35 • Large intestine (cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal) • considered to be “outside” the body (still in external environment) 2) Accessory digestive organs • teeth, tongue, gallbladder, liver, pancreas KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 36 DIGESTIVE SYSTEM ANATOMY KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 37 Digestive System Activities 6 essential activities: 1) Ingestion • physically taking food into the digestive system • mechanical digestion 2) Propulsion • moving food through the alimentary canal a) Swallowing • voluntary activity moving food down into the esophagus b) Peristalsis • involuntary movement of food through the esophagus, stomach and intestine • involves alternative “waves” of contraction and relaxation of smooth muscle • alters intestinal vessel (“tube”) diameter • chyme – whatever we ate that leaves the stomach KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 38 3) Mechanical digestion • physical preparation of food for absorption • chewing, mixing food with enzymes (tongue), churning of food in stomach Segmentation • mixing of food in intestine with digestive “juices” • smooth muscle contraction and relaxation KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 39 4) Chemical digestion • involves the secretion of enzymes into the alimentary canal • chemically breaks down food into “manageable” molecules • enzymes secreted by glands • starts in the mouth (salivary glands releasing amylases) 5) Absorption • movement of digested end products from GI lumen to the bloodstream (or lymph) • small intestine manageable molecules: CHO (carbs) - monosaccharide (glucose, fructose, galatose) Lipids – FFA (free fatty acid), MG (monoglyceride) PRO (proteins) – amino acids 6) Defecation • elimination of indigestible substances through the rectal canal and anus KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 40 ALIMENTARY CANAL STRUCTURE • Esophagus to anal canal • Mucous reduces friction in digestive system Four tunics (layers): 1) Mucosa 2) Submucosa 3) Muscularis externa 4) Serosa MUSCOSA • Moist epithelial layer that lines the lumen of the alimentary canal Three major functions: • Secretion of mucus (decreases friction, allows for easier movement of chime) • Absorption of end products of digestion • Protection against infectious disease 3 LAYERS 1) Epithelium • Mucus secretions: • Protect digestive organs from digesting themselves • Ease food along the tract KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 41 • Stomach and small intestine mucosa contain: • Enzyme-secreting cells • Hormone-secreting cells (making them endocrine and digestive organs) 2) Lamina propria • Loose areolar and reticular connective tissue • Nourishes the epithelium and absorbs nutrients • Contains lymph nodes 3) Muscularis mucosae • smooth muscle cells that produce local movements of mucosa KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 42 Submucosa – dense connective tissue containing elastic fibers, blood and lymphatic vessels, lymph nodes, and nerves - intestinal lining damage will lead to nutritional deficiencies - elasticity refers to the ability of the tissue to stretch and return back to original length (increasing diameter to accommodate, must be able to recoil) Muscularis externa – responsible for segmentation and peristalsis - nervous system will activate …. Peristalsis… longitudinal and circular muscle, contractions both responsible for applying pressure to chyme, chyme moves in path of least mechanical resistance – region where smooth muscle is relaxed - contracting cells move towards each other Serosa – the protective visceral peritoneum Forms the wall of the abdomominal cavity • Replaced by the fibrous adventitia in the esophagus • Retroperitoneal organs (behind peritoneal layer) have both an adventitia and serosa - Organ is behind the peritoneal layer .. talking mainly about kidneys..?? - Dietary Lipids and fat soluble vitamins are absorbed into lacteal - KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 43 KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 44 KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 45 NERVOUS SYSTEM CONTROL Enteric nervous system Composed of two major intrinsic nerve plexuses: • Submucosal nerve plexus (Meissner’s plexus) – regulates glands and smooth muscle in the mucosa • Present in small and large intestine • Not the portion responsible for peristalsis or segmentation • Helps to control pressure • Myenteric nerve plexus (Auerbach’s plexus) – Major nerve supply that controls GI tract mobility (change structure of actual tissue itself) motility – movement of chyme / contents of lumen • Present throughout alimentary canal • Segmentation and peristalsis are automatic involving local reflex arcs • Physical presence of food in intestinal system will stretch the intestines, stretch of skeletal muscle tissue discharges… when smooth muscle stretches … causes local reflex which leads to smooth muscle contraction through spinal cord • Smooth muscle is embedded with sensory neurons • Linked to the CNS via long autonomic reflex arc • Dietary fiber enhances GI motility Digestive System Blood Flow Splanchnic circulation - Portion of cardiovascular system that serves GI tract KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 46 • arteries - branch off abdominal aorta • Superior mesenteric – small intestine • Inferior mesenteric – large intestine • Serves gut (alimentary canal) , spleen, pancreas and liver (accessory digestive organs) • 1/4 of cardiac output under resting conditions • cardiac output  total amount blood leaving the left ventricle / minute (oxygenated) = HR (hb/min) x SV (how much of the blood gets kicked out of left ventricle / hb) = 5L/min @ rest, 25L/min @ maximal exercise • increases after a meal Function: • Metabolic support to intestinal cells • Secretion of chemicals into GI lumen • Absorption of macro- and micro-nutrients Portal vein • Blood flow into liver (from digestive organs) • Non-fat, water soluble nutrients (proteins in amino acid form, vitamin C, Bs, carbs) Hepatic vein • Blood flow away from liver (into vena cava which feeds deoxygenated blood back to heart) DIGESTIVE ANATOMICAL STRUCTURES KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 47 1) Mouth (lips, cheeks, palate, tongue, teeth, salivary glands) 2) Pharynx 3) Esophagus 4) Stomach (cardiac orifice, fundus, body, pyloric canal, pylorus, pyloric sphincter, omentum) 5) Small intestine (duodenum, jejunum, ileum) 6) Large intestine (cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal) MOUTH (oral cavity) Palate • forms the roof of mouth 2 parts: 1) Hard palate • palatine bones and palatine processes of maxilla • forms a rigid structure for food 2) Soft palate • formed mostly of skeletal muscle • closes the nasopharynx during swallowing Tongue • composed of bundles of muscle fibers KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 48 Function: 1) Grips food during chewing, mechanical digestion of food only 2) Repositions the teeth 3) Forms a bolus (single mass of food that is swallowed) and initiates swallowing 4) sensory organ… taste! omnomnom KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 49 Salivary glands • produces saliva Function: 1) Cleanses the mouth but doesn’t clean it..? 2) Dissolves food chemicals for tasting 3) Moistens food 4) Initiates breakdown of food (enzymes) Salivary amylase: breakdown of polysaccharides Intrinsic gland: buccal glands Extrinsic glands: parotid, submandibular and sublingual glands Exocrine glands: contains ducts the open into the oral cavity KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 50 Mastication • Chewing • Mechanical breakdown of food • Mixing with saliva • Voluntary and reflexive muscle activity (similar to walking) Swallowing 1st part: oropharynx 2nd part: laryngopharynx • pathway for food, fluids and air • consists of 2 layers of skeletal muscle • coordinated contraction moves food into the esophagus Deglutition (swallowing) Buccal phase: (1st phase of swallowing) • tongue forces food up and back against palate • voluntary activity Pharyngeal-esophageal phase: (2nd phase of swallowing) KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 51 • reflexive • controlled by “swallowing center” in lower pons and medulla, via cranial nerves • swallowing center refers to a cluster of neurons that controls the activity of the muscles that control swallowing – must be activated by motor neurons • cluster of neurons are located just inferior to the brain in the region called the brain stem ( lower pons, medulla); controls many autonomic functions including digestion Steps: 1) Tongue blocks off mouth 2) Soft palate rises to close nasopharynx 3) Larynx rises and is covered by epiglottis Diagram – be aware of: epiglottis, trachea, esophagus, oral cavity, hard palate Esophagus • Hollow tube surrounded by muscle • moves food toward the stomach • Approximately 10 inches long • Pierces the diaphragm muscle through the esophageal hiatus (“opening”) • Hole in the centre of the muscle to get to stomach Cardiac orifice • Opening into the stomach • Connection between the esophagus and the stomach • Surrounded by the cardiac (gastroesophageal) sphincter (ring of smooth muscle) KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 52 Stomach • “Storage tank” , food is partially digested • chemical breakdown of proteins: amylase breaks down carbs and lingual lipase – enzyme secreted in saliva • converted to chyme • 6-10 inches long • Empty stomach volume: 50 mL • “Full” stomach volume: up to 4 L. Rugae • folds in the stomach lining • folds maximize absorption, fit more glands, protein channels, etc. • more cells to secrete chemicals to breakdown food, increased SA Cardiac region • “near the heart” • opening of the stomach (coming from esophagus) Stomach (cont’d) Fundus: dome-shaped part (bulge), lateral to cardiac region KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 53 Body: mid-portion of the stomach Pyloric region: funnel-shaped, distal to body Pyloric antrum: superior and wider portion of pyloric region Pyloric canal: narrows from the pyloric antrum Pylorus: terminal portion of pyloric region Pyloric sphincter: controls stomach emptying Greater curvature: convex lateral surface of stomach Lesser curvature: concave medial surface of stomach Omenta: mesenteries that connect the stomach to other organs and peritoneum Mesenteries – sheet-like connective tissue, secretes mucous to protect organs from friction, houses blood vessels, coverings KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 54 Stomach (cont’d) - non uniform change in shape of stomach when diff angled muscle layers contract – increased mechanical digestion - gastric pits – secretion of enzymes, acid - pyloric sphincter – ring of smooth muscle that prevents the stomach from emptying, keeps contents in stomach – optimizes nutrient absorption and digestion - if bowels are open, it reduces the time that absorption can take place - chief cells produce pepsinogen is the inactive form of pepsin – active enzyme that breaks down proteins , parietal cells produce HCl which activates pepsinogen into pepsin - stomach is the first site of protein digestion KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 55 - lingual lipase for lipids, amylase for carbs (first enzymes to break them down) Gastric pits • Secretes gastric juice and alkaline mucus (bicarbonate – protective secretion) • Alkaline mucus – protective • Ulcers are holes burned in stomach by acid in it, Parasympathetic nervous system • vagus nerve • increases secretion of gastric glands • ANS – controls autonomic functions eg. Breathing, heart rate • Increased activation of PNS increases activation of gastric glands but slows down cellular metabolism of other systems – eg. After a meal • SNS – heighten activation of systems, increasing HR, cellular metabolism eg. Exercising Local reflexes - also activates secretions from gastric pits, stimulated by physical presence of food, stretching of stomach activates sensory neurons and local reflexes activated Stimuli • Head, stomach, small intestine • Psychological stimuli – increase PNS stimulation – memories, thinking, smells • Physical presence of food in small intestine will speed up and activate gastric glands KIN 1F03 – Introduction to Human Nutrition and Health D.M. Pincivero, 2012 56 Vomiting (emesis) Causes: • extreme stomach stretching (overeating) • irritants (alcohol, bacteria, spicy food) • syrup of ipecac • ipecac - dried root from Brazil • emetic - agent that induces vomiting (acting locall
More Less

Related notes for KINESIOL 1F03

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit