Anatomy & Physiology 2 - The Alimentary System (PDF)

RNB10702 ANATOMY & PHYSIOLOGY 2 THE ALIMENTARY SYSTEM GENERAL OVERVIEW OF THE SYSTEM THE MOUTH, PHARYNX AND OESOPHAGUS  LEARNING OUTCOMES At the end of the session, the students should be able to: list the organs of the gastrointestinal (GI) tract / alimentary canal; identif...

RNB10702 ANATOMY & PHYSIOLOGY 2 THE ALIMENTARY SYSTEM GENERAL OVERVIEW OF THE SYSTEM THE MOUTH, PHARYNX AND OESOPHAGUS  LEARNING OUTCOMES At the end of the session, the students should be able to: list the organs of the gastrointestinal (GI) tract / alimentary canal; identify the major functions of the digestive system; describe the layers forming the wall of the alimentary canal; describe the location, structure and functions of the:  mouth  pharynx  oesophagus 2  INTRODUCTION The digestive system is composed of the digestive tract and the accessory organs The digestive tract also called the alimentary canal or gastrointestinal (GI) tract The system extends from the mouth to the anus through the ventral body cavity (approximately 9 m/ 30 ft) Gastroenterology is the study of the gastrointestinal system 3  ORGANS OF THE GI TRACT Alimentary canal 1. Mouth 2. Pharynx 3. Esophagus 4. Stomach 5. Small intestine 6. Large intestine 7. Rectum & Anal canal Accessory organs 1. Liver 2. Gallbladder 3. Pancreas 4  24_01b Anterior view of the gastrointestinal tract 5 FUNCTIONS OF THE DIGESTIVE SYSTEM 1. Ingestion & mastication Ingestion is the introduction of food into stomach Mastication is the process of chewing to mechanically breakdown the food 2. Propulsion & mixing  Mixes & moves the food along the alimentary tract 3. Digestion Mechanical digestion – the teeth cut & grind the food Chemical digestion - digest food into small molecules by enzymes 6  Functions of the digestive system…cont 4. Absorption The simple molecules produced from chemical digestion absorb from the small intestine into the blood and lymph capillaries 5. Elimination Waste product excreted by bowel as feces through process of defecation 7  LAYERS OF GI TRACT The wall of alimentary tract are formed by 4 layers of tissue Layers covered from oesophagus onward;  Adventitia or serosa (visceral peritoneum)  Muscularis (Muscle layer)  Submucosa  Mucosa (lining) 8  Layers of GI tract…cont Adventitia or Serosa Outermost covering of GI tract organs Secretes slippery, watery fluid that allows the tract to glide easily against other organs In the thorax, consists of fibrous tissue In the abdomen, the organ covered by visceral peritoneum 9  Layers of GI tract…cont Muscularis (Muscle layer) Consists of 2 layers smooth involuntary muscle Contraction of the muscle layers produce peristalsis – push the contents of the tract onwards Circular muscle layer – if contract, the diameter of tube decreased Longitudinal layer – if contract, the length decreased & the tube shortens Contain myenteric plexus - controlling the movement & secretion of digestive tract 10  Layers of GI tract…cont Submucosa Contain blood & lymphatic vessels, nerves & glands Nerve - submucosal plexus (plexus of Meissner) – contain parasympathetic & sympathetic nerve that supply mucosal lining 11  Layers of GI tract…cont Mucosa – innermost layer Direct contact with the contents of the GI tract Consists 3 layers: Mucous membrane – functions as protection, secretion & absorption Lamina propria - contains blood vessels & lymphatic nodules - protect against microbial invader Muscularis mucosa – smooth muscle 12 13  Nerve supply Nerve supply from autonomic nervous system – sympathetic & parasympathetic Effect of sympathetic system ↓ Muscular activity especially peristalsis as stimulation of myenteric plexus is reduced ↓ glandular secretion as less stimulation of the submucosal plexus Effect of parasympathetic system ↑ Muscular activity especially peristalsis through increased activity of myenteric plexus ↑ glandular secretion as increased activity of the submucosal plexus 14  PERITONEUM The largest serous membrane of the body Closed sac filled with serous fluid within abdominal cavity contains blood & lymph vessels & many lymph nodes Has 2 layers:  Visceral peritoneum - covers organs within the abdominal & pelvic cavities  Parietal peritoneum - lines the abdominal wall Peritoneal cavity – space between visceral & peritoneal cavity which contains serous fluid 15  Peritoneum…cont Covered the stomach & intestine completely The mesentery, mesocolon, falciform ligament, lesser omentum, and greater omentum - extensions of the peritoneum 16  Peritoneum…cont The kidney, pancreas, spleen & adrenal glands are lies on behind the peritoneum (retroperitoneal) Greater omentum - cover in front of abdominal organ like an apron responsible for fat deposition contains lymph nodes Lesser omentum – attaches stomachs to liver forms a pathway for blood vessels to the liver contains common bile duct 17  Peritoneum…cont Mesentery & Mesocolon Hold the intestines loosely as muscular contractions mix and move the contents along the GI tract Mesentery - binds the small intestine to the posterior abdominal wall Mesocolon - binds the large intestine to the posterior abdominal wall 18  Peritoneum…cont Function of peritoneum Allow abdominal contents to glide without friction Keep the organs especially the intestine in position to prevent malposition Carries or supports the blood vessels, lymph vessels and nerves supplying the intestine and other organs Store fats to provide insulation for the body and long term storage of energy Wrapping itself around the affected part of the alimentary tract (e.g, appendicitis) to prevent infection from spreading Ability to absorb excessive fluids in large quantities 19  Peritoneum…cont (clinical application) Peritonitis - is an acute inflammation of the peritoneum 20  COMPONENT OF DIGESTIVE TRACT 21 ORAL CAVITY 22  MOUTH First part of alimentary canal for food ingestion Functions; Mastication: mechanical breakdown of solid particles, mixes them with saliva Chemical digestion - salivary acts on starches & lingual lipase acts on triglycerides organ of speech and sensory reception Surrounded by lips, cheeks, tongue, palate Includes oral cavity and vestibule 23  Mouth…cont Cheeks & lips Hold the food during chewing Assist in speech Palate Roof of the oral cavity Hard palate – formed by maxilla & palatine bone Soft palate –continuous from hard palate Uvula - extends from the soft palate  Move upwards with the soft palate to prevent entry of food & liquids into oropharynx 24  Accessory organs of the mouth Tongue Teeth Salivary glands 25  TONGUE Composed of voluntary muscle Attached by its base to the hyoid bone Frenulum – connect tongue to floor of mouth Papillae – contain taste buds & cover upper surface of tongue Lingual tonsil – lymphatic tissue mass on root of tongue Functions include – chewing, swallowing, speech, taste 26  TEETH Used for mechanical digestion Primary or deciduous teeth  Appear at 6 months of age  Contain 20 teeth Secondary or permanent teeth  Contain 32 teeth 27  Teeth…cont Function of the teeth Incisors - to cut food Cuspids or canines - used to tear or shred food Premolars & molar teeth - used for crushing & grinding food 28 Superior and inferior view of teeth for 2 sets of dentition 24_08 Temporary dentition Permanent dentition  Teeth…cont Structure of the tooth Crown – covered with enamel - thin, outer layer of a very hard substance Neck – place for crown & root meet & is adjacent to the gingiva or gum Root – anchor tooth in bone Enamel – hardest substance surround the dentin 30  Teeth…cont Structure of the tooth Pulp cavity – contain blood vessels, connective tissue & nerves Dentin – surrounded pulp cavity Cementum – connective tissue that surround dentin Nerve supply – upper teeth is by maxillary nerve & lower teeth is by mandibular nerve 31  Teeth (Clinical application) Dental carries Cavities within enamel of a tooth Formed when sticky foods lodge between teeth or in crevices of molars Bacteria on teeth metabolize sugars Acidic by-products destroy enamel and dentin 32  SALIVARY GLANDS 3 main pairs of salivary glands – parotid, submandibular & sublingual glands Have 2 types of cells  Serous cells - produce a watery fluid, containing a digestive enzyme called salivary amylase, which splits starch and glycogen into disaccharides  Mucous cells - secrete mucus, which binds food particles and lubricates food while swallowing 33  Salivary glands…cont Secretion of saliva Controlled by autonomic nervous system Parasympathetic stimulation – increase salivation Sympathetic stimulation - inhibits salivation caused dry mouth Components of saliva Water & electrolytes – eg; Na+, K+, Cl– Digestive enzyme – salivary amylase Mucus Lingual lipase (enzyme) digests fat Protection against microorganisms: e.g. IgA & lysozyme 34  Salivary glands…cont Function of saliva Chemical digestion of polysaccharides into disaccharides by enzyme amylase Cleaning & lubricating the mouth – to keep the mouth soft & moist to prevent mucous damage Lubrication of food - moisten & lubricate food during mastication & swallowing Non-specific defense – lysozyme & immunoglobulins in saliva combat invading microbes Taste – taste buds are stimulated after the food are mixing with saliva 35  Salivary glands (clinical application) Mumps is an inflammation and enlargement of the parotid salivary glands caused by infection with the mumps virus (myxovirus) Symptoms include fever, malaise, pain, and swelling of one or both glands If mumps is contracted by a male past puberty, it is possible to experience inflammation of the testes and, occasionally, sterility 36  PHARYNX Cavity posterior to the mouth Extends from nasal cavity to esophagus Do not help in food digestion Nerve supply Sympathetic - cervical ganglia Parasympathetic - glossopharyngeal & vagus nerve 37  Pharynx…cont Divided in 3 parts:  Nasopharynx – act as passageway of air  Oropharynx – allow food to enter during swallowing  Laryngopharynx – open into esophagus & the larynx Uvula - prevent food entering the nasopharynx Epiglottis - prevent food entering the larynx & direct food into esophagus Function in swallowing Peristaltic movements - force food from the pharynx into esophagus 38  ESOPHAGUS It is a collapsible, muscular tube Lies behind the trachea Connects the pharynx to the stomach About 25cm long & 2cm dimeter Serves as a passageway for food between the pharynx & stomach Wall of the esophagus - mucosa, submucosa, and muscularis layers 39 Esophagus…cont Continuous with pharynx from above and join the stomach just below the diaphragm. 40  Esophagus…cont Upper esophageal sphincter – regulate the movement of food from the pharynx into esophagus Lower esophageal/cardiac sphincter – control movements of food from esophagus into the stomach & prevents the reflux of gastric contents into the esophagus 41 42  Esophagus (Clinical application) Gastroesophageal reflux disease occurs when the lower esophageal sphincter fails to close adequately after food has entered the stomach, resulting in stomach contents refluxing into the inferior portion of the esophagus HCl from the stomach contents irritates the esophageal wall resulting in heartburn 43  Function of The Mouth, Pharynx and Esophagus Formation of bolus Food is chewed by teeth in the mouth (masticated) → move around by tongue & muscle of cheeks → mixed with saliva → formed into soft mass (bolus) Muscle of cheeks 44  Function of The Mouth, Pharynx and Esophagus Swallowing (deglutition) Occurs in 3 stages – oral stage, pharyngeal stage & esophageal stage Oral stage  Tongue move upward & backward against the palate to push the bolus  Voluntary muscles of tongue & cheeks push the bolus backward into the pharynx 45  Function of The Mouth, Pharynx and Esophagus Swallowing (Deglutition) Pharyngeal stage – swallowing center in medulla stimulated involuntary action to push bolus down into esophagus  Soft palate closed the nasopharynx  Epiglottis closed the larynx 46  Function of The Mouth, Pharynx and Esophagus Swallowing (Deglutition) Esophageal stage - peristalsis propel food into the stomach  Cardiac sphincter relax – bolus pass into stomach Esophagus are lubricated by mucus to assist the movement of bolus during peristalsis Peristalsis - constriction and relaxation of the. oesophageal muscles that pushes food bolus down into the stomach 47 The peristalsis proses 48 49 50 51 52