Digestion and Absorption

Digestion & Absorption Digestion Label the following diagram of the human digestive system Salivary gland 1. ………………………………………………………………………... Oesophagus 2. ………………………………………………………………………... Liver 3. ………………………………………………………………………... Stomach 4. ………………………………………………………………………... Gall bladder 5. ………………………………………………………………………... Pancreas 6. ………………………………………………………………………... Small intestine 7. ………………………………………………………………………... Large intestine 8. ………………………………………………………………………... Outline the function of the following digestive organs A temporary storage tank where food is mixed by churning and protein digestion begins Stomach: ………………………………………………………………………………………………………………………………………… It is lined by gastric pits that release digestive juices, which create an acidic environment ………………………………………………………………………………………………………………………………………………….......... Produces a broad spectrum of enzymes that are released into the small intestine via the duodenum Pancreas: …………..…………………………………………………………………………………………………………………………… Also secretes certain hormones (insulin, glucagon), which regulate blood sugar concentrations ………………………………………………………………………………………………………………………………………………….......... A long, highly folded tube where usable food substances (nutrients) are absorbed Small Intestine: …………….………………………………………………………………………………………………………………… Consists of three sections – the duodenum, jejunum and ileum ………………………………………………………………………………………………………………………………………………….......... Final section of alimentary canal, where water and dissolved minerals are absorbed Large Intestine: …………….………………………………………………………………………………………………………………… Consists of the ascending / transverse / descending / sigmoidal colon, as well as the rectum ………………………………………………………………………………………………………………………………………………….......... Takes the raw materials absorbed by the small intestine and uses them to make key chemicals Liver: ……….……………………………………………………………………………………………………………………………….......... Its role includes detoxification, storage, metabolism, bile production and haemoglobin breakdown ………………………………………………………………………………………………………………………………………………….......... Differentiate between chemical and mechanical digestion Mechanical digestion is the breakdown of food by physical action (e.g. chewing, churning, segmentation) ………………………………………………………………………………………………………………………………………………….......... Chemical digestion is the breakdown of food by chemical agents (e.g. stomach acids, bile, enzymes) ………………………………………………………………………………………………………………………………………………….......... ………………………………………………………………………………………………………………………………………………….......... Complete the following table Enzyme Source Substrate Product Optimal pH (salivary) amylase Salivary gland Starch Maltose ~7 pepsin (protease) Gastric pits (stomach) Proteins Short polypeptides ~2 (pancreatic) lipase Pancreas Triglycerides Glycerol + fatty acids ~8 Compare digestive movement via peristalsis and segmentation Continuous segments of longitudinal smooth muscle rhythmically contract and relax Peristalsis: ……………………………………………………………………………………………………………………………………… Food is moved unidirectionally along the alimentary canal in a caudal direction (mouth to anus) ………………………………………………………………………………………………………………………………………………….......... ………………………………………………………………………………………………………………………………………………….......... and relaxation of non-adjacent segments of circular smooth muscle in intestines Segmentation: Contraction ………………………………………………………………………………………………………………………………… Contractions move chyme in both directions, allowing for a greater mixing of food with digestive juices ………………………………………………………………………………………………………………………………………………….......... ………………………………………………………………………………………………………………………………………………….......... Absorption Label the tissue layers of the small intestine Serosa 1. ………………………………………………………………………… Longitudinal muscle 2. ………………………………………………………………………… Circular muscle 3. ………………………………………………………………………… Submucosa 4. ………………………………………………………………………… Mucosa (with intestinal villi) 5. ………………………………………………………………………… Lumen 6. ………………………………………………………………………… What type of cross-section is this? Transverse ……………………………………………………………………………… Distinguish between absorption and assimilation Absorption is the movement of fluids or dissolved substances across a membrane Absorption: ……………………………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………………………………………….......... The conversion of nutrients into fluid / solid parts of the organism Assimilation: …………………………………………………………………………………………………………………………………... ………………………………………………………………………………………………………………………………………………….......... With the aid of the diagram, explain how the structure of an intestinal villus relates to its role The primary role of the intestinal villus is to absorb digested products …………………………………………………………………………………………………… Microvilli – Ruffling of epithelial membrane increases surface area …………………………………………………………………………………………………… Rich blood supply – Capillary network transports absorbed products …………………………………………………………………………………………………… Single layer epithelium – Minimises diffusion distance …………………………………………………………………………………………………… Lacteals – Absorbs lipids from the intestine into the lymphatic system …………………………………………………………………………………………………… Intestinal glands – Exocrine pits release digestive juices …………………………………………………………………………………………………… Membrane proteins – Facilitates transport of digested materials …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… Identify the different methods of membrane transport that may be used to absorb nutrients Secondary Active Transport: Glucose and amino acids are co-transported with Na+ ions ………………………………………………………………………………………………………………………………………………….......... Facilitated Diffusion: Monosaccharides, vitamins and some minerals are transported by channel proteins ………………………………………………………………………………………………………………………………………………….......... Simple Diffusion: Hydrophobic materials (e.g. lipids) may diffuse freely across the epithelial membrane ………………………………………………………………………………………………………………………………………………….......... Endocytosis: Dissolved materials are absorbed en masse by the process of pinocytosis (cell ‘drinking’) ………………………………………………………………………………………………………………………………………………….......... Outline the digestion of starch (and subsequent transport of products) Starch is composed of glucose monomers in either linear (amylose) or branched (amylopectin) arrangement ………………………………………………………………………………………………………………………………………………….......... Amylase is an enzyme that digests starch (amylose into maltose ; amylopectin into short dextrin chains) ………………………………………………………………………………………………………………………………………………….......... The pancreas plays a fundamental role in the digestion of starch molecules: ………………………………………………………………………………………………………………………………………………….......... It secretes amylase and hormones (insulin and glucagon) that regulate glucose uptake by the liver …………………………………………………………………………………………………………………………………………………..........