Sunday 29th January Day 1: The Digestive Tract From Anatomy to Treatment A Nutritional Approach MPS www.osteopathicea.com mike@osteopathicea.com
AKA Digestive Tract, Alimentary Canal, Enteron, or Gut Body cavity extending from the mouth to the anus, approximately 9m (30ft) long Primary functions: Digestion / Breakdown of food Absorption of nutrients Water balance regulation Major barrier to infection and infiltration by pathogens, including bacteria, viruses, parasites etc Expulsion of toxic substances i.e. vomiting and diarrhoea.
GIT Organs include: Mouth (oral cavity) Pharynx Oesophagus Stomach Small intestine Large intestine Rectum and Anus Accessory organs include: Liver Gallbladder Pancreas
The GIT is a hollow tube surrounded by a wall composed of four main layers: 1. Mucosa 2. Submucosa 3. Muscularis 4. Serosa or adventitia The inside is known as the Lumen Remember the contents of the Lumen are actually outside of the body, so the GIT can be seen as a continuation of the the bodies other primary barrier organ, the skin.
Layers of the GIT Body wall Outer longitudinal muscle Inner circular muscle Muscularis externa Peritoneum Mesentery Serosa Submucosa Muscularis mucosa Lamina propria Mucous membrane Lumen Mucosa Myenteric plexus Submucosa plexus
Layer 1: Mucosa consists of : epithelium (lining the lumen) lamina propria (loose connective tissue) muscularis mucosae (thin layer of smooth muscle cells) Epithelium: Selective barrier for absorption and immune defence Transport of digested food particles Goblet Cells produce mucus for lubrication Diffuse Endocrine System cells produce digestion regulating polypeptide hormones
Lamina propria: Below epithelium Loose connective tissue Rich blood supply Lymph nodes, lymphocytes and plasma cells, and macrophages form the first line of immunological defense against bacterial and viral invasion. Muscularis mucosa Produces local muscular contractions in mucosa
Layer 2: Submucosa consists of: Loose connective tissue Meissner's nerve plexus Regulates blood vessels Regulates glandular secretions i.e. Stomach acid, mucus, hormones
Layer 3: Muscularis consists of: 2 sub-layers of smooth muscle Circular inner layer & Longitudinal outer layer Involved in peristalsis Auerbach's (myenteric) nerve plexus (between mm layers) Peristaltic muscularis contractions propel & mix food, & forcibly expel unwanted contents, i.e. Vomiting Peristaltic contractions mainly generated by Auerbach's myenteric plexus. Plexi consist of small parasympathetic ganglia PNS fibres provide secretomotor innervation to the mucosa nearest the lumen of the gut
Layer 4: Serosa or Adventitia consisting of: Serosa: Thin layer loose connective tissue covered by mesothelium (simple squamous epithelium) Serosa present in regions of GIT found within peritoneal cavity Adventitia: Thin layer of loose connective tissue that holds regions of GIT not found in peritoneal cavity in place
Layers & Structures of the GIT
Various Facts Associated with the GI Tract Timings: Food bolus, once swallowed, takes 9 seconds to reach stomach (peristaltic movement 3cm/second) Food in stomach - 2 hours ( 80% of food into duodenum in 3hrs) Food in small intestine - 6 hours Food in large intestine ~ 18 hours (constipation > 90 hours) Size: Overall - 4.6 metres long Small intestine - 2.8 metres Large intestine - 1.2 metres Area of small intestine - 2,000,000cm 2 (20m x 10m)
Secretions and Functions of the GI Tract Site of secretion Secretory cell Secretory component Substrate End result/product Salivary glands Serous Mucous Amylase Lipase Mucin Starch Triglycerides Maltose + oligoscccharides Fatty acids + monoglycerides Esophagus Mucous Mucin Stomach Parietal Chief Mucous HCl Intrinsic factor Pepsinogen Lipase Mucin Stomach contents Vitamin B 12 Protein Triglycerides Acidification Absorption Peptides + amino acids Monoglycerides + fatty acids Pancreas Acinar Amylase Trypsin Chymotrypsin Carboxypeptidase Polysaccharides Proteins Proteins + peptides Oligosaaccharides Small peptides Peptides + amino acids
Secretions and Functions of the GI Tract Site of secretion Secretory cell Secretory component Substrate End result/product Pancreas (cont) Duct epithelium Lipase Phospholipase Cholesterol Esterase Ribonuclease Deoxyribonuclease Bicarbonate Triglycerides Lecithin Cholesterol Esters Nucleic acids Intestinal contents Fatty acids + monoglycerides Lysolecithin Cholesterol + fatty acids Mononucleotides Neutralisation Liver Hepatocyte Duct epithelium Bile salts Bicarbonate Lipids Intestinal contents Micellisation & absorption Neutralisation Small intestinal mucosa Enterocytes Oligosaccharidases Peptidases Mucin Oligosaccharides Peptides Monosaccharides Amino acids Large intestine Mucous Mucin
Water Balance in the GI Tract Volume (ml/day) entering lumen of digestive tract 2,000 Ingestion 1,500 Salivary glands Volume (ml/day) absorbed from lumen of digestive tract Small intestine 8,500 Large intestine 400 Total absorbed 8,900 2,500 Stomach 500 Liver 1,500 Pancreas 1,000 Small intestine 9,000 Total entering Secretion 7,000 Faeces 100
The Mouth or Oral Cavity
The Mouth or Oral Cavity Functions: 1. Food / drink ingestion 2. Taste 3. Physical Digestion begins: 1. Mastication (chewing / grinding) breaks food into small particles 2. Mixes food with saliva. 3. Formation of a bolus 4. Initiation of physical digestive processes (2nd phase after cephalic) 5. Swallowing 6.
Consists of: The Mouth or Oral Cavity 1. Teeth for mechanical breakdown of food 2. Tongue with taste buds to detect sweet, sour, salt, bitter & umami for identification of foods, minerals, poisons etc 3. Tongue for moving food and initiating swallowing 4. Salivary glands produce saliva for lubrication and bolus 5. Salivary glands produce saliva containing amylase enzyme for initial breakdown of starches and lysosomal enzyme for antibacterial action 6. Salivary glands produce Haptocorrin (R Factor) protein to protect B12 from stomach acid 7. Lips, gums, palate, uvula etc The mouth leads directly into the Pharynx and Oesophagus
Pharynx & Oesophagus Naso - pharynx Oropharynx Laryngo - pharynx Oesophagus
Pharynx & Oesophagus Pharynx (AKA Throat) is made up of 3 parts: 1. Nasopharynx for respiration 2. Oropharynx for entry of air or bolus to laryngopharynx 3. Laryngopharynx for transport of air to trachea / larynx and bolus to Oesophagus 4. Epiglottis found behind the tongue 5. Lingual Tonsils on posterior tongue at pharyngeal opening 6. Palatine Tonsils near opening of oral cavity into pharynx 7. Pharyngeal Tonsils bear opening of nasal cavity to pharynx. When enlarged known as Adenoids
Pharynx & Oesophagus Oesophagus: Approx 3cm long & travels into abdomen via the right crus of diaphragm, posterior to central tendon. Propels bolus from Pharynx to Stomach Ends with Lower Oesophageal Sphincter (LOS), becoming continuous with the stomach at the Cardiac Orifice Lies left of midline between Diaphragm and Liver's left lobe Peritoneum covers anterolaterally Gastric arteries & veins Vagal innervation LOS hypertonicity => Achalasia LOS hypotonicity => Hiatus Hernia +/- Gastric Reflux
Pharynx & Oesophagus Achalasia: Spasm of Lower Oesophageal Sphincter (LOS) Symptoms: Acute / Severe Retrosternal pain Commonly felt during or after eating Often due to mineral imbalances Can be due to excessive Vagal tone Diaphragm hypertonicity can predispose Ensure medical examination rules out CVS causes etc Treatment: Calcium-Magnesium dissolved in water at end of or after finishing meal Cal-Mag allow muscle fibres to relax Osteopathic treatment to reduce Vagal tone & relax diaphragm