topic 9 pt 1

• What is the full form of GIT?

  Gastro-Intestinal Tract
• What are the main components of the digestive tract?

  • Oral cavity (mouth)
  • Pharynx (throat)
  • Oesophagus (gullet)
  • Stomach
  • Small intestine
  • Large intestine

  
• What are the accessory structures of the digestive system?

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

  
• What are the main functions of the digestive system?

  1. Ingestion
  2. Mastication (chewing)
  3. Propulsion

  • Deglutition (swallowing)
  • Peristalsis
  • Mass movement in large intestine

  1. Segmentation (small intestine ONLY)
  2. Secretion

  • Mucus, H2O, bile, enzymes, HCl

  1. Digestion

  • Mechanical and Chemical

  1. Absorption

  • End products move into circulation (blood/lymph)

  1. Defecation (elimination/egestion)

  
• What are the layers of the GI tract?

  1. Mucosa (innermost layer)
  2. Submucosa
  3. Muscularis externa
  4. Serosa or Adventitia (outermost layer)

  
• What is the function of the epithelium in the GI tract?

  • Secretes enzymes, acid, and absorbs nutrients
  • Contains goblet cells for mucus secretion
  • Contains entero-endocrine cells
• What type of connective tissue is found in the lamina propria?

  Loose connective tissue
• What is the role of the muscularis mucosae?

  It is a thin layer of smooth muscle that helps in folding of the small intestine.

  
• What does the submucosa contain?

  • Blood vessels
  • Lymphatic vessels
  • Glands
  • Nerves (Meissner's plexus)

  
• What is the function of Meissner's plexus?

  It contributes to the enteric nervous system of the gut.
• What are the two types of muscle found in the muscularis externa?

  • Smooth Muscle (involuntary control)
  • Skeletal Muscle (voluntary control)
• What is the function of Auerbach's plexus?

  It innervates circular and longitudinal smooth muscle layers.
• How do peristalsis and segmentation differ?

  • Peristalsis: Moves food forward
  • Segmentation: Moves food forward and backwards for mixing
• What is the serosa and its function?

  • A serous membrane containing serous fluid-secreting cells
  • Protective outer layer of intraperitoneal organs
• What are retroperitoneal organs?

  Organs located behind the parietal peritoneum.
• What is the function of mesenteries, mesocolon, and omenta?

  • Hold organs in place
  • Store fat
  • Route for blood and lymphatic vessels and nerves
• What are the ligaments associated with the liver?

  1. Coronary ligament
  2. Falciform ligament
  3. Round ligament (ligamentum teres)
• What is the structure and function of the oral cavity?

  • Bounded by lips, fauces, vestibule, and oral cavity proper
  • Involved in ingestion of food

  
• What are the functions of the lips and cheeks?

  • Lips protect the anterior opening of the oral cavity
  • Cheeks form the lateral walls of the oral cavity
• What are the components of the palate?

  • Hard palate: anterior, supported by maxilla and palatine bone
  • Soft palate: posterior, consists of skeletal muscle and connective tissue
  • Uvula: closes off the nasopharynx during swallowing

  
• What is the structure and function of the tongue?

  • Moves food in mouth
  • Involved in speech and swallowing
  • Contains intrinsic and extrinsic muscles

  
• What are the types of teeth and their functions?

  • Incisors and canines: cut and tear food
  • Molars: grind food

  
• What are the three pairs of salivary glands and their secretions?

  1. Parotid: largest, serous secretion
  2. Submandibular: mixed, more serous than mucous
  3. Sublingual: smallest, primarily mucous secretion

  
• What is the average daily secretion of saliva?

  About 1-1.5 L/day
• What is the composition of saliva?

  • 99.5% water
  • 0.5% solutes (salts, mucin, lysozyme, amylase, lipase, IgA)
  • pH: 6.35 - 6.85
• What are the parts of the pharynx?

  • Nasopharynx
  • Oropharynx
  • Laryngopharynx
• What is the function of the oesophagus?

  • Transports food from pharynx to stomach
  • Produces thick layer of mucus for lubrication
• What are the phases of swallowing (deglutition)?

  1. Buccal or voluntary
  2. Pharyngeal reflex
  3. Esophageal reflex

  
• What are the parts of the stomach?

  • Cardiac
  • Fundus
  • Body
  • Pyloric

  
• What are the layers of the stomach?

  • Mucosa (contains gastric glands)
  • Submucosa (contains blood vessels)
  • Muscularis externa (three layers)
  • Serosa (visceral peritoneum)

  
• What do gastric glands secrete?

  • Mucous neck cells: mucus
  • Parietal cells: HCl and intrinsic factor
  • Chief cells: pepsinogen, gastric lipase
  • G cells: secrete gastrin

  
• What are the movements of the stomach?

  • Mixing waves (80%)
  • Peristaltic waves (20%)