Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Digestive System PPT File
Document related concepts
Transcript
The Digestive System Human Bio 2A.3 Digestion Is the breaking down of the nutrients we eat into smaller simpler organic compounds that can be absorbed by the body and into the cells Digestive processes can be chemical (involving digestive enzymes), or mechanical Digestion • The organs of the D.S. are structured + arranged to carry out 6 basic activities: 1. Ingestion of food + water 2. Mechanical digestion of food (physical breakdown) 3. Chemical digestion of food 4. Movement of food along the alimentary canal 5. Absorption of digested food and water into the blood + lymph 6. Elimination of material that is not absorbed Mouth Salivary Glands Oesophagus Stomach Liver Pancreas Small intestines Large intestines Rectum & Anus ENZYMES Acts on End product Amylase Carbohydrates Simple sugars (e.g. glucose) Lipase Lipids Protease Proteins Fatty acids Amino acids #1. Mouth PERFORMS ACTIVITES: 1,2 and 3. INDIGESTION, MECHANICAL AND CHEMICAL DIGESTION •Need to know function of teeth, tongue, salivary amylase Mechanical processes in the mouth Chewing (mastication) Bolus formation Swallowing Chemical digestion in the mouth Enzyme Salivary amylase Product Polysaccharides → Sugars Section through the head Nasal cavity Palate Teeth Tongue Pharynx Hyoid bone Epiglottis Larynx Esophagus The salivary glands Parotid gland Submandibular gland Sublingual gland Human dentition Incisors Canine Premolars Molars Upper dentition Human dentition Molars Gray’s Anatomy Pre-molars Incisors Canine #2. Oesophagus Peristalsis Wave-like contraction of the muscular wall travels along the oesphagus BOLUS Structure of the alimentary tube Villus Mucosa Thin muscle layer Submucosa Longitudinal muscle layer Circular muscle layer Peritoneum Questions 1. List the 6 activities the Digestive System is involved in 2. What is the smallest unit carbohydrates break down in to? Proteins? Fats? 3. What type of digestion does the mouth do? 4. Describe in detail the structures that do both types of digestion (i.e. all the different types of teeth and what they do) 5. At the end of digestion in the mouth – what is broken down? 6. What is the term given to food that leaves the mouth? 7. Explain peristalsis Stomach Section through the stomach Fundus Esophagus Rugae Pyloric sphincter muscle G Meyer ANHB – UWA Mechanical processes in the stomach Muscular churning mixes food with gastric juice (forms chyme) Extra muscular layer (oblique) Rennin (in infants only) curdles milk Section through the stomach Esophagus Three muscle layers Rugae Pyloric sphincter muscle Duodenum Chemical digestion in the stomach Enzyme Product Hydrochloric Acidic environment = acid Activates pepsinogen → pepsin Pepsin Proteins → peptones Absorption in the stomach Limited absorption of water, glucose, alcohol and some drugs takes place in the stomach Then enters the DUODENUM (first part of the small intestines) Pancreas (enzymes) and Liver (bile) produce substances that also enter at the duodenum via the common bile duct Pancreas • Pancreatic juice enters the duodenum through the common bile duct • pH ~8 (slightly alkaline) to neutralise acidity from stomach Mechanical processes in the duodenum Bile salts emulsify fats (reduces them to small droplets which increases their surface area) Chemical digestion in the duodenum Enzyme Product Pancreatic Amylase Disaccharides → glucose Pancreatic Fats & oils → fatty acids + Lipase glycerol Trypsin Peptones → polypeptides (pancreatic protease) #3. Small Intestines Segmentation in the Small Intestines • main mixing movement • Contents must be continually moved so mix in with digestive juices. • Circular muscle fibres in the intestinal wall contract, dividing the intestines into segments. • The rhythmic effect is to ‘slosh’ the contents back and forth – mixing contents together a) Peristalsis – occurs in oesphagus b) Segmentation – occurs in small intestines Chemical digestion in the small intestine Enzyme Intestinal Amylase Maltase Lactase Sucrase Intestinal Lipase Product Maltose → glucose Lactose → glucose Sucrose → glucose intestinal protease Peptidases Polypeptides → amino acids Fats & oils → fatty acids & glycerol Absorption in the small intestine • Glucose, amino acids, water and minerals are absorbed into the blood capillaries Move via ACTIVE TRANSPORT • Fatty acids and glycerol are absorbed into the lacteals (forming chyle) *Chlyromicrons Small Intestines are suited to function: • • • • 6m long folded mucosa Small finger-like projections - villi Villi covered in microscopic projections microvilli = Increase the internal surface area of the small intestines = greater absorption. Section through small intestine showing villi Secretory cells Villus Gland L. Slomianka ANHB-UWA Section through a villus Epithelial cells & goblet cells Lacteal Network of blood capillaries Intestinal gland Lymph vessels #4. Large Intestines Functions of the large intestine • Further absorption of water (via OSMOSIS) and some salts • Bacterial activity – there are trillions of resident bacteria in the large intestine. believed to have several important roles in addition to digesting cellulose in plant foods and synthesising some vitamins (e.g. folic acid) The large intestine LIVER Colon (transverse branch) Colon Caecum Appendix (ascending branch) Colon (descending branch) Rectum Liver Blood travels from the small intestines via the Liver via the Hepatic Portal Vein Some major functions of the liver Deaminates amino acids (deamination) – of excess proteins = then broken down Converts glucose to glycogen Produces bile Stores iron, and vitamins A, B12, D, E & K Synthesises vit A & plasma proteins Removes Toxins - Detoxicates drugs (including alcohol) and other toxins External features of the liver Inferior vena cava Hepatic artery Gall bladder Bile duct Hepatic portal vein Miles Kelly Art Library Summary • Each organ designed for specific breakdown of food molecules • Digestion aims to break food into smallest molecule so can be absorbed (and therefore cells able retrieve nutrients) Carbohydrates (break into monosaccharides – simple sugars) 1st - Mouth 2nd - Small Intestines Proteins (break down to amino acids) 1st - Stomach 2nd - Small Intestines (pancreatic & intestinal) Fats/Lipids (break down to fatty aids + glycerol) 1st Small Intestines (pancreatic & intestinal)
