Lecture Two

Glands that secrete fluid into the digestive system.

• Oral cavity (mouth) Accessory organs= tonsils and salivary glands. • Pharynx (throat). • Oesophagus. • Stomach. • Small intestines= Duodenum, Jejunum, Ileum. Accessory organs= liver gallbladder and pancreas. • Large intestines- cecum, colon, rectum and anal canal.

• Ingestion • Mastication • Propulsion • Mixing • Secretion • Digestion • Absorption • Elimination

Food is mechanically broken down to increase the total surface area to allow digestive enzymes to easily break down food.

Propulsion-The movement of food through the digestive tract. Swallowing-Moves the bolus (mass of liquid and soft food) from the oral cavity to the oesophagus. Peristalsis-Wave of smooth muscle relaxation & contractions which expands the tract in front of the bolus. -Process by which food moves through the gut. Mass movements-Contractions that move material -Large intestines

-Segmental contractions. oSegments fluctuate between relaxation and contractions. oPurpose is to mix the food with digestive secretions which assist with breaking in down into smaller pieces. oSmall intestines.

-Purpose to digest, buffer, lubricate and liquefy

• Mechanical- Mastication and mixing - Chemical- Digestive enzymes

-Molecules moving out of the digestive tract into the circulatory or lymphatic system.

-Waste products are eliminated from the body via defecation. -Occurs in the large intestine, material is altered from a liquefied substance to semi-solid (faeces) substance by absorbing water and salts. →Ultimate aim= the breakdown of large food molecules to smaller ones that can be absorbed into the circulatory system.

oMucus- Entire digestive tract. -Protects the epithelial cells from digestive enzymes, stomach acids and abrasion. -Lubricates the lining of the tract and the food. oWater -Liquefies the food- easier to digest/absorb. oEnzymes -Secreted from pancreas, small intestines, stomach and oral cavity.

-Food we ingest needs to be broken down to smaller molecules. -This occurs via chemical reactions. oThese can occur naturally but are quite slow. oRequires an enzyme. oDefinition: a substance that increase the speed of a reaction without being changed or used up in the process. -An enzyme is a type of catalyst. →Protein.

• Amylase - Breaks down carbohydrates. • Lipase - Breaks down lipids. • Protease - Breaks down proteins.

• Temperature 2. PH

• Mucosa - Mechanoreceptors - Chemoreceptors • Submucosa - Nerves, lymphatic and blood vessels and small glands. • Muscularis - Smooth muscle • Serosa - Smooth layer that covers the digestive tract organs.

Nervous Regulation -Enteric Nervous System (ENS) oA division of the autonomic nervous system. oLocated within the walls of the digestive tract. oCan work independently of the autonomic nervous system. Autonomic Nervous System -Parasympathetic Nervous System oRest and digest oIncreases motility, salivary and gastric acid secretions. -Sympathetic Nervous System oFight or flight oDecreases motility. Chemical Regulation -Endocrine secretions (hormones): gastrin, secretin and cholecystokinin.

-Mechanical & chemical digestion. -Normal adult teeth number=32. -Assists with the process of mastication (mechanical). oIncisors & canines -Tear & cut food. oPremolars & molars -Grind & crush food.

• 3 large salivary glands. • 1-1.5L/day • Watery/mucous secretion.

• Keeps the oral cavity moist. - Assists with the normal speech. • Suspension of food in a solution which aids taste. • Begins digestion. - Salivary Amylase-Starch splitting enzyme which breaks down 3-5% of carbohydrates. - Lingual Lipase-Digests small amount of lipids. • Protective Functions - Washes oral cavity. - Contains bicarbonate ions= Neutralize acids from oral bacteria. - Contains the enzyme lysozyme= Antibacterial properties which assists with preventing infection from bacteria.

-In response to taste, tactile stimuli & food odour.

• Nasopharynx • Oropharynx • Laryngopharynx

• Only the oropharynx & laryngopharynx are associated with digestion. • Uvula prevents food material entering the nasopharynx.

Covers the larynx to prevent food entering the respiratory passages. Connects pharynx to the stomach.

• From pharynx to stomach. • Posterior to the trachea. • Travels through the opening (hiatus) of the diaphragm.