GUT

• What is the primary function of the Gastrointestinal Tract (GIT)?


  To provide the body with a continual supply of water, electrolytes, and nutrients.
• What are the main functions of the GIT?

  • Ingestion of food
  • Digestion of food
  • Secretion of digestive juice
  • Absorption of water, salt, vitamins, and end-products of food digestion
  • Excretion of heavy metals, toxins, alkaloids, etc.
  • Helps erythropoiesis by secreting intrinsic factor needed for vitamin B12 absorption
• What are the phases of GIT activity?

  Movement of food, secretion of digestive juices, absorption of digestive foods, circulation of blood, and control of functions by nervous and humoral systems.
• What are the layers of the intestinal wall?

  1. Serosa

  2. Longitudinal muscle layer

  3. Circular muscle layer

  4. Submucosa

  5. Mucosa
• What is the Enteric Nervous System?

  It is the intrinsic nervous system of the GIT that begins in the esophagus and extends to the anus.
• What are the two layers of neurons in the Enteric Nervous System?

  1. Myenteric or Auerbach’s Plexus (outer)

  2. Meissner’s Plexus or submucosal layer (inner)
• What is the function of the Myenteric Plexus?

  It controls GIT movements and increases the tone of the gut wall, intensity of contractions, and conduction velocity of excitatory waves.
• What is the role of the Meissner’s Plexus?


  It controls secretion and blood flow in the GIT.
• How does the GIT receive innervation?

  • Extensive parasympathetic and sympathetic innervation
  • Parasympathetic supply includes:
  • Cranial (10th) Vagus nerve
  • Sacral (2nd, 3rd, 4th spinal pelvic nerves)
  • Sympathetic fibers originate in the spinal cord (between T-5 and L2) and inhibit GIT activity
• What are Slow Waves or Basic Electrical Rhythm (BER) in the GIT?

  They are slow undulations of activity caused by the Na-K pump, with varying frequencies in different parts of the GIT.
• What is the frequency of Slow Waves in the body of the stomach?

  3 waves per minute.
• What triggers spike potentials in GIT smooth muscle?

  When the resting membrane potential rises above -40 mV due to the opening of slow Ca-Na channels.
• What are the functional types of movement in the GIT?

  1. Mixing movements

  2. Propulsive movement

  3. Peristalsis
• What is the Law of the Gut?

  It describes the intrinsic desire for food (hunger) and the type of food preferred (appetite).
• What is the role of saliva in digestion?

  Saliva helps in the digestion of starches through the enzyme ptyalin and lubricates food for easier swallowing.
• What are the principal glands of salivation?

  • Parotid glands
  • Submandibular glands
  • Sublingual glands
  • Small buccal glands
• What are the two major types of protein secretions in saliva?

  Serous secretion containing ptyalin and mucous secretion containing mucin.
• What is the function of ptyalin in saliva?

  Ptyalin digests starches into maltose.
• What are the mechanical functions of saliva?

  • Keeps mouth moist and helps speech
  • Aids in mastication of food
  • Prevents injury to mucous membrane
• What are the digestive functions of saliva?

  • Ptyalin splits starch into maltose
  • Excretes urea, heavy metals, drugs, and microorganisms
• What are the stages of swallowing (deglutition)?

  1. Voluntary Stage

  2. Pharyngeal Stage (involuntary)

  3. Esophageal Stage (involuntary)
• What is the function of the gastroesophageal sphincter?


  It prevents backflow of stomach contents into the esophagus.
• What are the physiological divisions of the stomach?

  1. Corpus or Body (including fundus)

  2. Antrum
• What are the motor functions of the stomach?

  1. Storage of food

  2. Mixing food with gastric secretions to form chyme

  3. Slow emptying of chyme into the small intestine
• What is chyme?


  Chyme is a murky, milky semi-fluid mixture resulting from food mixed with stomach secretions.
• What are the phases of gastric secretion?

  1. Cephalic Phase

  2. Gastric Phase

  3. Intestinal Phase
• What types of stomach glands are there?

  1. Single-cell Mucous Gland

  2. Oxyntic (Gastric) Glands

  3. Pyloric Glands

  4. Cardiac Glands
• What are the types of cells in the stomach and their secretions?

  • Mucous neck cells: Secrete mucus and some pepsinogen
  • Peptic or chief cells: Secrete pepsinogen
  • Oxyntic or parietal cells: Secrete HCl and intrinsic factor
• What is the daily secretion of gastric juice?

  1200-1500 mL.
• What is the pH range of gastric juice?

  0.9 - 1.5.
• What is the role of the pyloric valve?

  It prevents intestinal contents from backflowing into the stomach.
• What is the primary function of the small intestine?

  The small intestine is where most chemical and mechanical digestion occurs, particularly the digestion of proteins into amino acids.
• What is the average length of the small intestine?

  1. 10 feet.
• What are the movements of the small intestine?

  1. Mixing contractions (segmentation)

  2. Propulsive movement (peristalsis)
• What is peristaltic rush?

  It is a powerful and rapid peristalsis in the small intestine caused by irritation of the intestinal mucosa.
• What enzymes are secreted by the small intestinal mucosa?

  1. Enterokinase

  2. Proteolytic enzymes (e.g., Aminopolypeptidase, Dipeptides)

  3. Carbohydrate-splitting enzymes (e.g., Lactase, Sucrase, Maltase, Alpha-dextrinase)
• How is water absorbed in the small intestine?

  Water is absorbed by osmosis, with 99% of the amount absorbed.
• What is the absorption mechanism for glucose in the small intestine?

  Glucose is absorbed by Na-glucose co-transport.
• How are amino acids absorbed in the small intestine?

  Amino acids are absorbed via sodium-amino acid co-transport.
• How is fructose absorbed in the small intestine?

  Fructose is absorbed by facilitated diffusion after being converted to glucose.