Digestive Organs and Their Functions

Accessory Organs

• Assist in digestion, absorption of nutrients, and waste elimination.

Digestive Tract - Digestive Organs

• Mouth:

  • Lips and cheeks aid in chewing and swallowing.
  • Tongue is a muscular organ with taste buds:
    • Filiform papillae: Provide texture and grip.
    • Fungiform papillae: Sensory receptors for taste.
    • Vallate papillae: Large, mushroom-shaped for taste perception.
    • Foliate papillae: Located on the sides of the tongue, contribute to taste.
  • Salivary glands:
    • Parotid: Secretes serous saliva, rich in enzymes.
    • Sublingual: Produces mucous saliva, for lubrication.
    • Submandibular: Secretes mixed saliva, containing both serous and mucin.
  • Teeth:
    • Deciduous (baby) teeth: 20 teeth that are replaced by permanent teeth.
    • Permanent (adult) teeth: 32 teeth, designed for specific functions.
      • Incisors: Cutting.
      • Canine: Tearing.
      • Premolars: Grinding.
      • Molars: Crushing.
    • Dental formula: 2I, 1C, 2PM, 3M for one quadrant of the mouth.
    • Tooth structure: Crown, neck, root.
  • Tooth/Gum Disease:
    • Dental Caries (tooth decay): Destruction of tooth enamel due to bacteria.
    • Gingivitis: Inflammation of the gums.
    • Periodontitis: Inflammation and destruction of the tissues surrounding teeth.

• Tonsils:

  • Palatine and lingual tonsils are part of the immune system, protecting against infection.
  • Tonsillitis: Inflammation of the tonsils.

• Pharynx:

  • Oropharynx and laryngopharynx are involved in swallowing.
  • Deglutition (swallowing):
    • Epiglottis covers the glottis to prevent food entry into the trachea.
    • Soft palate covers the nasopharynx, blocking food from entering the nasal cavity.

• Esophagus:

  • Muscular tube that propels food to the stomach via peristalsis.
  • Gastroesophageal (cardiac) sphincter controls food movement into the stomach.

Stomach

• Areas:

  • Cardia: Entrance of the esophagus.
  • Fundus: Dome-shaped region.
  • Body: Main central region.
  • Pylorus: Lower region containing the pyloric sphincter.

• Histology:

  • Rugae: Folds of the mucosa, increasing surface area for absorption.
  • Gastric pits/glands:
    • Mucous (neck) cells: Secrete mucus, protecting the stomach lining.
    • Parietal cells: Produce HCl and intrinsic factor (vitamin B12 absorption).
    • Chief cells: Secrete pepsinogen (inactive form of pepsin, a protein-digesting enzyme).
    • Enteroendocrine cells: Secrete hormones like gastrin.

• Gastric juice: Contains pepsin and HCl, crucial for digestion.

Energy Balance

• Obesity: Body weight exceeding 20% of "ideal" weight.
• BMI (Body Mass Index): Measures body fat based on height and weight.
• Metabolic Rate: Rate at which the body uses energy.
  • Basal Metabolic Rate (BMR): Energy expenditure at rest.
  • Total Metabolic Rate (TMR): Total daily energy expenditure.

Temperature and Heat Exchange

• Hypothalamus: Regulates body temperature.
• Heat Exchange Mechanisms:
  • Radiation: Heat transfer without direct contact.
  • Conduction: Heat transfer through direct contact.
  • Convection: Heat transfer through fluid movement.
  • Evaporation: Heat loss through sweat.