Salivary Glands and Ducts Quiz

Salivary Glands and Saliva

• Saliva is a watery secretion produced by 3 major glands in the exocrine system: submandibular, parotid, and sublingual glands.
• Each gland has a duct that secretes saliva into the oral cavity.
• Parotid gland: produces watery serous saliva through Stenson's duct.
• Submandibular gland: produces mixed secretion (serous and mucous) through Wharton's duct.
• Sublingual gland: produces mainly mucous saliva through Bartholin's or sublingual duct.
• At rest, the submandibular gland produces 70-75% of saliva, the parotid gland produces 20-25%, and the sublingual gland produces 5%.
• After stimulation, the parotid gland releases the highest amount of saliva.

Composition of Saliva

• Saliva is 99% water and 1% electrolytes/proteins.
• Electrolytes and proteins include Na, K, Ca, HCO3, and enzymes.
• Enzymes in saliva: alpha amylase (ptyalin), lingual lipase, and lysozyme.
• Alpha amylase breaks down starch, lingual lipase breaks down fat, and lysozyme acts against pathogens.

Stomach

• The stomach has different layers: mucosa, submucosa, muscularis, and serosa.
• The stomach has five areas: cardia, fundus, body, antrum, and pyloric sphincter.
• The stomach has specialized gastric cells: mucous cells, chief cells, parietal cells, G cells, and D cells.
• Mucous cells secrete mucous, chief cells secrete inactive pepsinogen, and parietal cells secrete HCL and intrinsic factor.
• Inactive pepsinogen is converted into active pepsin by hydrochloric acid.
• Pepsin breaks down proteins and polypeptides.

Small Intestine

• The small intestine is 6.5m long and has three parts: duodenum, jejunum, and ileum.
• The small intestine has a circular shape to increase surface area for absorption of nutrients.
• Food mixed with acid from the stomach becomes chyme, which is then absorbed in the small intestine.
• Chemical digestion occurs in the small intestine, aided by secretions from the liver and pancreas.

Liver and Pancreas

• The liver secretes bile, which is stored in the gallbladder.
• The pancreas secretes pancreatic juice, which contains lipase, amylase, and bicarbonate enzymes.
• Bicarbonate is alkaline and neutralizes the acidic environment in the small intestine.

Nerves Involved

• The parasympathetic nervous system increases muscular activity and glandular secretion (rest and digest).
• The sympathetic nervous system decreases muscular activity and glandular secretion (fight or flight).
• The vagus nerve supplies the parasympathetic nervous system.

Digestive System

• The digestive system converts food into nutrients and excretes unwanted substances.
• The process of digestion involves ingestion, digestion, absorption, and egestion.
• The mouth and oral cavity are involved in mechanical digestion, with the help of teeth and salivary glands.
• The throat (pharynx) is involved in both respiration and digestion.
• Food is pushed back by the tongue and swallowed through the pharyngeal phase, which is the first irreversible step in swallowing.
• The esophagus is a muscular tube that transports food to the stomach through peristalsis.
• The esophageal sphincter prevents reflux of gastric contents and allows food to enter the stomach.