PHA618 LAB - digestive system

• chol/e


  gall, bile
• cyst/o


  bladder, sac
• sigmoid/o


  sigmoid colon
• Hollow tube structures of the digestive system form the alimentary canal
• Accessory structures


  • Teeth
  • Tongue
  • Salivary glands
  • Liver
  • Gallbladder
  • Bile ducts
  • Pancreas

  
• Nutrients are required for normal body function
• Nutrients


  • Carbohydrates
  • Proteins
  • Lipids
  • Vitamins
  • Minerals
• Nutrients are derived from food
• Food we eat is too big to be directly passed into blood
• Goals of digestive system

  • Digest food into smaller molecules
  • Absorb smaller molecules into the blood
• Mechanical Digestion


  Physical breakdown of food into smaller pieces to form a greater surface area for contact with digestive enzymes
• Chemical Digestion


  Splitting of complex, non-absorbable food molecules into small, absorbable nutrient molecules by hydrolysis using enzymes
• Enzymes speed up the reaction and enable digestion to occur
• Oral Cavity


  Lined by stratified squamous epithelial tissue
• Deciduous teeth are replaced by permanent teeth
• Tooth structure


  • Crown
  • Enamel
  • Dentin
  • Root
  • Pulp cavity

  
• The purpose of the tongue is to manipulate what is ingested and to provide the sense of taste
• Salivary glands


  • Parotid glands
  • Submandibular glands
  • Sublingual glands
• Saliva contains enzymes amylase and lingual lipase, along with mucus, lysozymes, and antibodies
• Mechanical and chemical digestion takes place in the mouth
• The masseter and temporalis muscles move the jaw for mastication
• Amylase in saliva partially digests carbohydrates
• Mucus mixes with the food to make it easier to swallow
• Bolus


  The bite of food before it is swallowed
• The pharynx is composed of the nasopharynx, the oropharynx, and the laryngopharynx
• Epiglottis


  Elastic cartilage that guards the opening of the larynx
• The esophagus is a tube that goes through the diaphragm to connect with the stomach
• Deglutition (swallowing) involves four cranial nerves
• The epiglottis closes off the glottis so that the bolus moves to the esophagus
• Peristalsis moves the bolus through the esophagus
• The stomach has three layers of smooth muscle in its walls, each oriented in a different direction
• The lining of the stomach has rugae for more surface area to accommodate gastric pits that lead to gastric glands
• Types of cells in gastric pits and gastric glands

  • Mucous cells
  • Endocrine cells
  • Parietal cells
  • Chief cells
  • Regenerative cells
• During swallowing, the medulla oblongata sends signals to the stomach, telling it to relax
• The cardiac sphincter opens to allow the bolus to enter the stomach
• Stretching of the stomach walls starts peristaltic contractions
• The pyloric sphincter remains closed until the pH of the stomach contents reaches 2
• Hydrochloric acid changes pepsinogen to pepsin so that proteins are partially digested
• Hydrochloric acid activates lingual lipase, which partially digests lipids along with gastric lipase
• Intrinsic factor binds to vitamin B12 so that it can be absorbed later