46 - secretion, enzyme breakdown and reabsorption in mouth. Control of secretion. swallowing - phases and control

sections

secretion

salivary enzyme

swallowing

regulation of swallowing

secretion

• Saliva secreted in mouth which is responsible for digestion. It contains a serous and a mucous secretion form.

• Secreted from parotid (serous), submandibular and sublingual (serous&mucous) and many buccal glands.

• mucous secretion contains mucin, mainly responsible for lubrication and surface protection.

salivary enzyme

• salivary a- amylase: starts to break carbohydrates

• lingual lipase: starts to break down lipids

• saliva ph- 7-7.5 in 24 hrs 1-1.5 litres- has water and minerals

swallowing

• Swallowing: has 3 stages—oral, pharyngeal and oesopha1geal

• oral → the food is voluntarily taken into the pharynx by using the tongue

• pharyngeal → bolus of food stimulates epithelial swallowing receptor areas.

  1. the soft palate is pulled upward to prevent reflux of food into nasal cavities.

  2. The palatopharyngeal folds are pulled together to form a slit through which the food can pass

  3. the vocal cords of the larynx are strongly approximated and the larynx

  4. is pulled upward → the epiglottis is pulled back to cover the opening of the larynx.

  5. Upward movement of the larynx enlarges the opening of the esophagus

  6. the entire muscular wall of the pharynx contract and this contraction wave is spreading downwards.

• oesophageal stage

  • primary peristalsis: is the continuation of the peristaltic wave from the pharynx → esophagus into the stomach → enhanced also by gravity

  • secondary peristalsis :is the distention of the esophagus and it continues until all the food is emptied into the stomach

regulation of swallowing

• Parasympathetic branch of ANS

• Acetycholine- muscarinic receptors-- stimulates secretion of saliva with the digestive enzymes

• Sympathetic inhibits saliva production