Digestive System Notes
Alimentary Canal (Gastrointestinal Tract)
The continuous tube through which food passes, allowing digestion and absorption of nutrients.
Organs Included:
1. Mouth:
⢠Entry point for food.
⢠Mechanical digestion via chewing (teeth).
⢠Chemical digestion begins with saliva containing amylase.
2. Pharynx:
⢠Passageway for food, fluids, and air.
3. Esophagus:
⢠Propels food to the stomach using peristalsis.
4. Stomach:
⢠Function: Temporary storage tank for food.
⢠Mixes food with gastric juices for breakdown into chyme.
⢠Secretes pepsin (breaks down proteins).
5. Small Intestine:
⢠Divisions:
⢠Duodenum.
⢠Jejunum.
⢠Ileum.
⢠Primary site of nutrient absorption.
⢠Receives bile (from liver) and pancreatic juices (from pancreas) to aid digestion.
6. Large Intestine:
⢠Divisions:
⢠Cecum, appendix, colon (ascending, transverse, descending, sigmoid), rectum, anal canal.
⢠Functions:
⢠Absorbs water.
⢠Houses bacterial flora for vitamin synthesis.
⢠Forms and eliminates feces.
7. Rectum and Anal Canal:
⢠Stores feces for elimination.
Accessory Digestive Organs
These organs assist the alimentary canal by producing or storing substances necessary for digestion.
Organs Included:
1. Teeth:
⢠Primary Teeth: 20 deciduous teeth erupt between 6 and 24 months.
⢠Permanent Teeth: 32 permanent teeth appear between 6 and 12 years.
⢠Classifications:
⢠Incisors: For cutting and nipping.
⢠Canines: Fang-like for tearing and piercing.
⢠Premolars (Bicuspids) and Molars: Broad crowns for grinding and crushing.
2. Tongue:
⢠Mostly skeletal muscle.
⢠Functions:
⢠Contains taste buds to analyze nutrient content of food.
⢠Mixes food with saliva to form a bolus.
⢠Aids in swallowing.
3. Salivary Glands:
⢠Function: Produce and secrete saliva (water-based liquid containing amylase) for chemical digestion.
⢠Types:
⢠Parotid glands.
⢠Submandibular glands.
⢠Sublingual glands.
⢠Fun Fact: Mumps infect the parotid glands.
4. Liver:
⢠Secretion: Produces bile, a greenish liquid (pH 7.6â8.6) essential for fat digestion.
⢠Functions of Hepatocytes:
⢠Produce bile.
⢠Process nutrients from blood.
⢠Store fat-soluble vitamins.
⢠Detoxify harmful substances.
5. Gallbladder:
⢠Thin-walled muscular sac on the liverâs ventral surface.
⢠Functions:
⢠Stores and concentrates bile.
⢠Releases bile into the duodenum to emulsify fats.
⢠Disorders:
⢠Gallstones causing blockages and pain.
⢠Extreme cases can result in gallbladder rupture.
6. Pancreas:
⢠Exocrine Function:
⢠Produces pancreatic juice containing enzymes for digesting carbohydrates, proteins, and lipids.
⢠Endocrine Function:
⢠Secretes insulin to regulate blood glucose levels.
⢠Disorders: Malfunction can cause diabetes.
Important Notes About Digestive System Processes
1. Ingestion: Intake of food through the mouth.
2. Propulsion:
⢠Swallowing.
⢠Peristalsis (waves of muscle contractions moving food through the tract).
3. Mechanical Digestion:
⢠Chewing (mouth).
⢠Churning (stomach).
⢠Segmentation (small intestine).
4. Chemical Digestion:
⢠Breakdown of food molecules by enzymes.
5. Absorption:
⢠Movement of nutrients into blood or lymph via small intestine.
6. Defecation:
⢠Elimination of indigestible substances and waste products as feces.
Note 
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