Human Biology ATAR Unit 1 Chapter Pages The digestive system

Keywords Making connections

Definitions Keyword Meaning Ingestion The taking in of nutrients Digestion The breakdown of complex organic molecules into smaller components by mechanical and chemical means Absorption The taking up of digested molecules into the internal environment of the cells of the digestive tract Egestion The removal of waste materials from the body

Digestive systems The function of the digestive system is to break down the food we eat into simpler organic compounds that can be absorbed by the body Digestion changes nutrients: Large to small Insoluble to soluble

Nutrients Nutrients are broken down through: Mechanical digestion Breaks food down into smaller pieces increased surface area increased efficiency of chemical digestion Chemical digestion Enzymes break down food into molecules that can be absorbed into the blood We need 6 types of nutrients: Water Carbohydrates Fats Protein Minerals Vitamins

Mechanical digestion Mastication Teeth Tongue Incisors Canines Premolars Molars Tongue Helps to form a bolus which is swallowed and is forced down into the stomach by peristalsis Stomach churns food by muscular contractions Mechanical digestion of food continues in the duodenum of the small intestines

Chemical digestion Enzymes break down food further through chemical digestion Each nutrient has specific enzymes that work to break it down into its most basic unit Carbohydrates into glucose Fats into fatty acids and glycerol Proteins into amino acids

Organs of the digestive system Mouth Tongue Teeth Pharynx Epiglottis Oesophagus Stomach Liver Gall bladder Pancreas Small intestine Caecum Appendix Large intestine Ascending colon Transverse colon Descending colon Rectum Anus

Enzymes of the digestive system Category Acts on End product Amylases Carbohydrate Simple sugars (e.g. glucose) Lipases Lipids Fatty acids Proteases Proteins Amino acids

The anatomy of the digestive system US Govt NIH

Digestion in the mouth MECHANICAL Mastication (chewing) Bolus formation Swallowing CHEMICAL Amylase Polysaccharides to disaccharides (Complex carbohydrates to sugars eg. starch to sucrose)

Section through the head Nasal cavity Palate Teeth Tongue Pharynx Hyoid bone Epiglottis Larynx Esophagus

The salivary glands Parotid gland Submandibular gland Sublingual gland

The tongue Jari Keinänen

Human dentition Incisors Canine Premolars Molars Upper dentition

Human dentition Pre-molars Molars Incisors Canine Gray’s Anatomy

Tooth section Enamel Dentine Crown Pulp cavity Neck Gum Cementum Root Root canal From: The evolution of teeth cavities 1: The healthy tooth Copyleft : This work is free, you can copy, spread, and modify it under the terms of the Free Art License http://artlibre.org/licence/lal/en/

Peristalsis Wave-like muscle contractions of the oesophagus and intestines forces the bolus into the stomach and then along the gut. This process is called peristalsis. BOLUS

Digestion in the stomach MECHANICAL Muscular churning mixes food with gastric juices (forms chyme) Rennin (in infants only) curdles milk CHEMICAL Hydrochloric acid Activates pepsinogen to pepsin Pepsin Proteins to peptones

Absorption in the stomach Limited absorption of: Water Glucose Alcohol Some drugs

Section through the stomach Fundus Esophagus Rugae Pyloric sphincter muscle G Meyer ANHB – UWA

Section through the stomach Esophagus Three muscle layers Rugae Pyloric sphincter muscle Duodenum

Digestion in the duodenum MECHANICAL Bile salts emulsify fats (reduce them to small droplets which increases their surface area). CHEMICAL Amylase Disaccharides to monosaccharides eg. sucrose to glucose Lipase Fats to fatty acids & glycerol Trypsin Peptones to polypeptides

Inside the duodenum

Digestion in the small intestines MECHANICAL Bile salts emulsify fats (reduce them to small droplets to increases their surface area). CHEMICAL Maltase Maltose to glucose Lactase Laltose to glucose Sucrase Sucrose to glucose Lipase Fats to fatty acids & glycerol Peptidases Polypeptides to amino acids

Absorption in the small intestine Capillaries glucose amino acids water Minerals Lacteals fatty acids glycerol

Villi The small intestine absorbs most of the nutrients. It has a rich supply of capillaries The lining of the small intestine is highly convoluted with many villi These greatly increase the surface area for absorption

Section through small intestine showing villi Secretory cells Villus Gland L. Slomianka ANHB-UWA

Structure of the lining Villus Mucosa Thin muscle layer Submucosa Longitudinal muscle layer Circular muscle layer Peritoneum

The large intestines Function Further absorption of water and some salts Bacterial activity – there are trillions of resident bacteria in the large intestine. They are believed to have several important roles including digestion of cellulose in plant foods synthesis of some vitamins (e.g. folic acid).

The large intestine LIVER Transverse colon Ascending colon Caecum Descending colon Appendix Rectum

The liver Functions Deamination of amino acids Converting glucose to glycogen Bile production Storage of iron and vitamins (A, B12, D, E & K) Synthesis of vitamin A & plasma proteins Detoxification of drugs (including alcohol) and other toxins.

Liver Stomach Pancreas

Liver lobule Artery, vein & bile duct Central vein Lobule L. Slomianka ANHB-UWA

SUMMARY: Enzymes Amylases carbohydrate simple sugars Salivary amylase Target nutrient End product Where in the body Amylases carbohydrate simple sugars Salivary amylase beginning digestion of simple & complex carbohydrates mouth Maltase maltose → glucose small intestine Lactase lactose → glucose Sucrase sucrose → glucose Lipase lipids fatty acids glycerol Proteases proteins amino acids Pepsin peptones stomach Peptidases