Digestive System Processes THE DIGESTIVE SYSTEM Dr Adrian Mascia

Digestive System Processes Five Processes – Acronym MSDAE  Mechanical processing and movement: chewing, mixing  Secretion: fluid, digestive enzymes and hormones, bile, acid, alkali, mucus  Digestion: breaking down food to smallest absorbable units  Absorption: through mucosa, into blood or lymph vessels  Egestion: undigested material eliminated  Egestion: undigested material eliminated Processes of digestion

Overview of Digestive Pathway 1. Mouth 2. Oesophagus 3. Stomach 4. Small Intestine (Duodenum, Jejunum, Ileium) 5. Large Intestine (Colon, Rectum, Anus) Acronym:MOSDJICRA

Digestive System

The Mouth Mouth: begins digestion (Physical & Chemical)  Teeth - Incisors, canines, premolars, molars  Tongue - skeletal muscle, moves food in mouth, taste  Saliva -  Source: Salivary glands  Composition: Salivary amylase, bicarbonate. Mouth Oesophagus Stomach Small Intestine Large Intestine The Mouth

Pharynx and Oesophagus  Pharynx  Common passageway for air and food  Participates in swallowing  Oesophagus: connects pharynx to stomach  Structure: mix of skeletal and smooth muscle  Mucus secreting cells: assist passage of food  Food motility: gravity and peristalsis Mouth Oesophagus Stomach Small Intestine Large Intestine The Oesophagus

The contraction of the muscles within the esophagus causing food to be pushed into the stomach Motility: Peristalsis

Stomach Function (Chemical digestion) Functions: - Food storage - Chemical Digestion of Fats and some proteins - Delivery of Gastric juices Gastric Juices  Hydrochloric acid: produces a pH of about 2, breaks down large bits of food, creates suitable conditions for enzyme activity  Pepsinogen: begins protein breakdown  Bile : Breaks down Lipids  Mucus: protects stomach lining from acid Mouth Oesophagus Stomach Small Intestine Large Intestine The Stomach (Chemical Digestion)

Stomach Contraction (Mechanical Digestion) Produces Chyme Product of mixing food with the gastric juices Stomach contractions Propel Chyme from the lower Oesophageal sphincter to pyloric sphincter (Muscular bands that act as valves to stop back flow) Mouth Oesophagus Stomach Small Intestine Large Intestine

Small intestine Structure Duodenum Jejunum ileum Mouth Oesophagus Stomach Small Intestine Large Intestine

Small Intestine Functions (Digestion & Absorption) Absorption: 95% of food nutrients absorbed here Duodenum Break down of Long protein chains and Lipids Jejunum Break down of Carbohydrates & Completion of Protein Digestion Ileum Any final absorption of nutrients Mouth Oesophagus Stomach Small Intestine Large Intestine

Villi: Structure within the intestines Villi are like little hairs that line the intestines, they provide a large surface area for absorption of nutrients In the diagram you can see there are circulatory path ways inside the Villi waiting to take nutrients absorbed into the Villi around the body Nutrients enter the Villi via diffusion, this is possible as enzymes have acted on them, making them small enough to cross through the membrane.

Large Intestine = Mouth Oesophagus Stomach Small Intestine Large Intestine

. Large Intestine: Function and Structure Functions - Absorbs nutrients and water - Eliminates waste Structure: Caecum (Cellulose Break down), appendix Colon: ascending, transverse, descending, sigmoid Rectum Anus Mouth Oesophagus Stomach Small Intestine Large Intestine

Accessory Organs: Aid Digestion and Absorption  Pancreas  Secretes digestive enzymes and sodium bicarbonate  Liver  Produces bile (acts as emulsifer – begins fat breakdown)  Hepatic portal system: drains blood from digestive tract  Metabolic functions: storage, synthesis, chemical processing  Gallbladder stores Bile Slide 14.12

What influences Digestive structure? Diet influences digestive structure (or vice versa): Protein is digested in the stomach Carbohydrates digested in the small intestine Cellulose in a Caecum or Rumen

TYPES OF DIGESTIVE SYSTEMS

Cellulose Cellulose is a major part of many plant cells. A special Enzyme called “Cellulase” is required to break it down This enzyme is not naturally produced, it is produced by bacteria kept in specialised areas of herbivore digestive systems called a caecum

Mammalian Digestive Structure

Overview of Chemical Digestion

Digestive System Information to include in digestive diagram -Name & function of organs -Location of enzymes / secretions involved in the digestive process -Location of the absorption of the organic compounds being digested