Digestive System: Tongue, Teeth, and Saliva

• Digestive system functions include:
  • Ingestion
  • Digestion
  • Absorption
  • Compaction
  • Defecation

Tongue Functions and Taste

• The tongue has three main functions:
  • Manipulating food
  • Sensing taste
  • Swallowing
• Papillae on the tongue contain taste buds.
• Taste buds can detect five primary tastes:
  • Sweet
  • Sour
  • Salty
  • Bitter
  • Umami
• Saliva dissolves food chemicals, allowing them to be tasted.
• About 80% of flavor perception is due to smell.

Teeth

• A full set of deciduous teeth (baby teeth) consists of 20 teeth.
• A full set of permanent teeth consists of 32 teeth.
• Permanent teeth often require braces due to jaw size and evolutionary changes in diet.
• Tooth decay results from bacteria metabolizing sugars and producing acids that erode tooth enamel.
• Odontoclasts resorb the roots of baby teeth, allowing them to be shed.

Salivary Glands, Swallowing

• The three pairs of salivary glands are:
  • Parotid
  • Submandibular
  • Sublingual
• Approximately 1-1.5 liters of saliva is produced daily
• The soft palate and uvula prevent food and liquid from entering the nasal cavity during swallowing.
• Peristalsis is the process that moves food along the digestive tract.
• The esophageal sphincter prevents stomach acid from entering the esophagus.
• Acid reflux or heartburn occurs when the sphincter malfunctions.

Stomach

• The stomach stores food, mixes it with gastric juices, and begins protein digestion.
• Rugae are folds in the stomach lining that allow for expansion.
• The stomach's three muscle layers, each with different fiber directions, enable powerful churning and mixing.
• The pyloric sphincter regulates the release of chyme into the small intestine.

Small intestine

• The small intestine:
  • Completes digestion
  • Absorbs nutrients
• Villi lining the small intestine contain:
  • Blood vessels: Absorb carbohydrates and proteins
  • Lacteals: Absorb fats

Large Intestine

• The large intestine:
  • Absorbs water and electrolytes
  • Compacts and eliminates feces
• E. coli in the intestines synthesize vitamins and aid digestion.
• Diarrhea, constipation, and hemorrhoids can be related:
  • Diarrhea: Rapid movement of feces can irritate the anal canal
  • Constipation: Straining during bowel movements can cause hemorrhoids

Liver and Gallbladder

• Bile contains:
  • Bile salts: Aid in fat digestion
  • Bilirubin: A waste product from hemoglobin breakdown.
• Besides bile production, the liver performs:
  • Detoxification
  • Nutrient storage
  • Protein synthesis
  • Red blood cell and hormone breakdown
• Jaundice occurs when bilirubin accumulates in the blood, causing yellowing of the skin and eyes.

Liver Problems

• Gallstones: Crystalized cholesterol and bile salts.
• Cirrhosis: Scarring of the liver, often due to alcohol abuse or hepatitis.
• Hepatitis: Inflammation of the liver, usually caused by viral infection.
• Gallstones, cirrhosis, or hepatitis can cause jaundice by impairing bilirubin processing.

Pancreas

• The pancreas has two main functions:
  • Producing digestive enzymes
  • Secreting insulin and glucagon to regulate blood sugar
• Acute pancreatitis is inflammation of the pancreas, often due to gallstones or alcohol abuse.
• Diabetes is a metabolic disorder characterized by elevated blood sugar levels.

Gallbladder

• The gallbladder stores and concentrates bile.

Hormones vs Enzymes

• Digestive hormones regulate digestive processes.
• Digestive enzymes break down food molecules.

Enzymes

• Amylases break down carbohydrates.
• Enzymes ending in "-psin" (e.g., trypsin, pepsin) break down proteins.