Nutr Unit 3: Anatomy and Physiology

2 main groups of digestive system (Alimentary canal)

• Continous digestive tube through whole body

• Function is digestion (breaks down food into smaller fragments) and absorption

2 main groups of digestive system (Accessory digestive organs)

Teeth, tongue, gallbladder, liver, pancreas

Anatomical structure

• Mouth

• Pharynx

• Esophagus

• Stomach

• Small intestine

• Large intestine

1. Ingestion

physically taking in food

2. Propulsion

• Moving food through alimentary canal

Swallowing

voluntary activity of moving food down into esophagus

Peristalsis

• involuntary movement of food through esophagus, stomach and intestine

• Involves alternative “waves” of contraction and relaxation of smooth muscle

3. Mechanical Digestion

• Physical preparation of food for absorption

• Chewing, mixing food with enzymes (tongue), churning of food in stomach

Segmentation

Mixing of food (chyme) in intestine with digestive “juices”, smooth muscle contraction and relaxation

4. Chemical Digestion

• Involves the secretion of enzymes into alimentary canal

• Chemically breaks down food into “manageable” molecules

• Enzymes secreted by glands

• Starts in mouth (salivary glands releasing amylase)

5. Absorption

• Movement of digested end products from GI lumen to the bloodstream (or lymph)

• Small intestine (THE nature absorption organ)

6. Defecation

• Elimination of indigestible substances through rectal canal and anus

• We do not absorb all the nutrients we take in

Lumen

Hollow inside of digestive tract

• Where the food actually is

Mucosa (Inner layer) & 3 layers

• Touches the food

• Main job: absorption + secretion

• Lines the lumen

3 Layers:

• Epithelium

• Lamina propria

• Muscularis mucosae

Submucosa

• Support layer

• Has blood vessels, nerves, glands

• Helps move absorbed nutrients into blood

Muscularis externa

• Moves food

• Made of smooth muscle

• Creates peristalsis

Serosa

• Protection

• Reduces friction with other organs