Digestive System for KEATS PDF
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These are notes on the digestive system for KEATS students. The notes cover the introduction, the mouth, the esophagus, stomach, small intestine and large intestine. There are sections of diagrams and descriptions throughout the document.
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Introduction to digestive system All cells need energy and nutrients to carry out their chemical...
Introduction to digestive system All cells need energy and nutrients to carry out their chemical processes, which mostly comes from the food and fluids ingested Digestive system is responsible for: o Breaking down food and fluids into small molecules (mechanical and chemical digestion) that can absorbed into the blood o Removing waste products from the body The digestive system is altered by Reproduced from: Anatomy and Physiology in Healthcare by Marshall et al. increased progesterone during ISBN: 97819079042958 © Scion Publishing Ltd, 2017 pregnancy, and problems can be aggravated by the growing uterus 1 Figure 7.12 Reproduced from: Anatomy and Physiology in Healthcare by Marshall et al. ISBN: 97819079042958 © Scion The mouth, salivary glands & pharynx Teeth o 20 deciduous/milk teeth o 32 permanent teeth Palate o Roof of the mouth o Hard palate at the front and soft palate at the back o Hard palate is formed by maxilla and palatine bones o Soft palate is formed by muscle Tongue 📷 @sarahstirkphotography 3 pairs of salivary glands o Produce digestive enzymes that pass into the mouth o Saliva is the combined secretions of these 6 glands and small glands inside the mouth Pharynx is involved in swallowing process (epiglottis covers the trachea) 3 Oesophagus Peristalsis enables transportation of boluses of food ~25cm long thin-walled tube that runs from pharynx to stomach Each end has a sphincter: 1) cricopharyngeal sphincter prevents air entering the oesophagus during inspiration 2) cardiac sphincter prevents regurgitation of stomach contents Movement of a bolus by peristalsis. Reproduced from: Ross & Wilson Anatomy and Physiology in Health and Illness by Waugh Stomach Enlarged J-shaped organ Stomach walls are arranged in rugae (folds) which allow distension Produces gastric secretions including hydrochloric acid (highly acidic) to enable digestion Food is stored in fundus and body More muscular pylorus contracts to churn up the bolus with the gastric secretions and reduce it to semi-fluid mass called chyme Chyme passes through the pyloric sphincter into the small intestine Gastric emptying takes 2-6 hours after eating Reproduced from: Anatomy and Physiology in Healthcare by Marshall et al. Limited absorption of nutrients ISBN: 97819079042958 © Scion Publishing Ltd, 2017 Small intestine - digestion The small intestine is ~6.5m long and can be divided into 3 parts: 1. Duodenum (25cm) 2. Jejunum (2.5m) 3. Ileum (3.6m) Chyme mixes with intestinal secretions, bile and pancreatic juices, some of which enter through 2 ducts that open into the mid part of the duodenum Chyme is transported via peristalsis and segmentation, which separates the chyme into small parcels though localised contraction of the intestinal Reproduced from: Anatomy and Physiology in wall Healthcare by Marshall et al. ISBN: 97819079042958 © Scion Publishing Ltd, 2017 6 Small intestine - absorption Absorption begins in duodenum Mucosal layer is folded to increase surface area for absorption The brush border (villi and microvilli) further increases surface area Approximately 30m2 Substances are absorbed into a network of blood capillaries in each villus Absorbed by various mechanisms including passive diffusion, facilitated diffusion and active transport End products of digestion take to liver for metabolism via the portal vein Reproduced from: Anatomy and Physiology in Healthcare by Marshall et al. ISBN: 97819079042958 © Scion Publishing Ltd, 2017 7 Accessory organs – liver, gall bladder & pancreas Liver produces 750-1000ml of a thick , alkaline, greenish-yellow substance called bile each day Bile is stored in the gall bladder and released into the duodenum via the common bile duct to help digestion and excretion The pancreatic duct carries 1500ml of pancreatic juices carrying digestive enzymes from the pancreas to the duodenum each day via two ducts: 1. Pancreatic duct which joins the common bile duct 2. Accessory duct which enters duodenum directly Reproduced from: Anatomy and Physiology in Healthcare by Marshall et al. ISBN: 97819079042958 © Scion Publishing Ltd, 2017 8 Large intestine & appendix The large intestine is ~1.5m long and can be divided into 2 parts: 1. Caecum 2. Colon(ascending, transverse, descending & sigmoid) More water is absorbed here with some electrolytes and vitamins from the chyme The appendix is attached to the caecum Images Reproduced from: Anatomy and Physiology in Healthcare by Marshall et al. ISBN: 97819079042958 © Scion Publishing Ltd, 2017 9 Rectum & anus The rectum and anus form the final 20cm of the GI tract The anus has 2 sphincters: 1. Internal anal sphincter under involuntary control (parasympathetic NS) 2. External anal sphincter under voluntary control (somatic NS) Defecation occurs due to co- ordinated contraction and relaxation of these 2 sphincters (defecation reflex) Reproduced from: Anatomy and Physiology in Healthcare by Marshall et al. ISBN: 97819079042958 © Scion Publishing 10 Ltd, 2017 Metabolism of food Metabolism is the process in which food (carbohydrates, lipids and proteins) is turned into energy Cells need a continuous supply of energy, but we eat food periodically Absorptive state During periods of digestion and absorption digested foods are absorbed, transported and used immediately for energy as required Any excess glucose is stored as glycogen in the liver and muscle cells Excess fat is stored as triglycerides in adipose tissue Post-absorptive state During periods of fasting (e.g. overnight) these stores are used Body initially relies on stored glycogen: Blood glucose Glycogen broken Glucagon released drops down into glucose Starvation state Once glycogen stores are used, triglycerides are broken down (lipolysis) generating ketones which become the body’s main source of energy 11 Impact of physiological changes during pregnancy Increased appetite (consumption of food) & thirst Pregnancy cravings and food aversions Non-food cravings (pica) Nausea and vomiting of pregnancy (NVP) Hyperemesis gravidarum (HG) Heartburn and acid reflux Constipation Haemarrhoids Gingivitis Excessive saliva (ptyalism) Increased risk of food poisoning Increased risk of gall stones Risk of intrahepatic cholestasis Fig. 11.9 Gastrointestinal function in pregnancy Reproduced from: Anatomy & Physiology for Midwives by Coad et al 12 Digestive system during labour NICE (2023) Intrapartum care NG235 Slower gastric emptying Risk of Mendelson’s syndrome if GA needed Many women do not feel like eating in labour Little research into fluid and nutrient needs during labour Nausea and vomiting common Diarrhoea or constipation 📷 @freshpinephotos_stlmotherhood 13