Unit 4 Lecture 25 Flashcards
What are the organs of the GI tract?
- Mouth
- pharynx
- esophagus
- stomach
- small intestine
- large intestine
- rectum and anus
What is the function of the mouth?
mechanical and chemical breakdown, deglutition (swallowing)
What is the function of the pharynx and esophagus?
swallowing and avoiding airway
What is the function of the stomach?
mechanical and chemical breakdown with some absorption
What is the function of the small intestine?
chemical and mechanical breakdown with major absorption
What is the function of the large intestine?
absorption of electrolytes and some vitamins
What is the function of the rectum and anus?
defecation
What are the major layers of the GI tract?
- Mucosa
- Submucosa
- Muscularis
- Serosa
What are the layers of the Mucosa?
- Epithelium
- Lamina Propria
- Muscularis Mucosae
What is the epithelium of the mucosa layer made out of?
- Stratified squamous: mouth, esophagus and anus
- Simple columnar: rest of GI tract
What is the function of simple columnar epithelium in the mucosa layer?
- Secretes enzymes and absorbs nutrients
- Specialized cells (goblet) secrete mucous onto cell surfaces
- Enteroendocrine cells secrete hormones controlling organ function
What is the lamina propria of the mucosa layer made of?
Connective tissue
What else is found in the lamina propria?
Blood vessels and lymphatic tissue
What is the muscularis mucosa layer of the mucosa made of?
Smooth muscle
What is the function of the muscularis mucosa layer of the mucosa?
- Creates folds in the stomach and small intestine –> drives local movements to increase absorption by exposing ingested material to absorptive surfaces
What is the submucosa made of?
Loose connective tissue
What is found in the submucosa layer?
Submucosal plexus (Meissner’s plexus)
What specific nervous system is the submucosal plexus part of?
Enteric Nervous System?
What is the enteric nervous system?
Nerves from the central nervous system (brain and spinal cord) go to the Peripheral Nervous System (nervous outside brain and spine) and become Autonomic Motor Neurons —> ENTERIC MOTOR NEURONS in enteric plexuses —> smooth muscle, glands and endocrine cells of GI tract
Where does the submucosal plexus receive input from?
- Sympathetic neurons (thoracic and lumbar spinal cord)
- Parasympathetic neurons (Vagus Nerve and Sacral Spinal Cord)
The submucosal plexus motor neurons directly goes innervates on what?
Mucosal epithelium
What is the function of the submucosal plexus?
- Regulates blood vessel diameter
- Secretion from glands and neurosecretory neurons
- Local motility caused by muscularis mucosae
What is the muscularis made of?
- Skeletal muscle: Mouth, pharynx, and Upper esophagus and anus (with voluntary control)
- Smooth muscle: rest of GI tract (inner circular fibers and outer longitudinal fibers)
What does the skeletal muscle control in the muscularis layer of the GI tract?
Controls deglutition and defecation
What does the smooth muscle control in the muscularis layer of the GI tract?
Allows motility for mixing and propulsions
What is found in the muscularis layer of the GI tract?
Myenteric plexus (Auerbach’s Plexus)
What nervous system is the myenteric plexus a part of?
Enteric nervous system (shares some functions with submucosal plexus)
What is the function of the myenteric plexus?
Provides parasympathetic and sympathetic innervation of circular and longitudinal smooth muscle layers
What is the deepest layer of the GI tract (minus esophagus)?
Serosa
What is the deepest layer of the esophagus?
Adventitia
What is the function of the serosa?
- secretes serous fluid
What is the serosa made of?
Areolar conenctive tissue covered in simple squamous epithelium
What is the adventitia made of?
Areolar connective tissue without epithelium
What is another name for the serosa?
Visceral peritoneum
What are the layers of the peritoneum?
- Visceral peritoneum
- Peritoneal cavity
- parietal peritoneum
What does the Visceral peritoneum do?
Covers organs
What does the parietal peritoneum do?
Lines the walls of body cavity
What things connect organs in the body abdominal cavity?
- Greater and lesser omentum
- Mesocolon
- Mesentery
- Falciform Ligament
What are the 2 types of digestion in the mouth?
Chemical and Mechanical
What is mechanical digestion?
Mastication or chewing
- breaks pieces of food into pieces
- mixes with saliva so that it forms a moist bolus
What enzymes are involved in chemical digestion in the mouth?
Salivary amylase and lingual lipase
What does salivary amylase do in the mouth?
Begins starch digestion (pH 6.5-7) but stops when bolus hits acidic gastric juices (pH 2)
What does lingual lipase do in the mouth?
Tongue glands secretes lingual lipase and breaks down triglycerides (Lipids) into fatty acids and glycerol
What are the major glands in the mouth?
- Parotid gland
- Sublingual gland
- Submandibular gland
Where do all ducts empty into?
oral cavity in the mouth
What triggers/ increases salivation
sight, smell, sounds, memory of food and tongue stimulation
What decreases salivation?
fear and anxiety
What are the glands connected to?
salivary ducts (w/ same names as glands)
What is the composition of saliva?
water, HCO3- and enzymes
What are the specific functions of saliva?
- moistens food (swallow)
- dissolves food (taste)
- HCO3- buffers acidic foods
- Protects mouth from infection with rinsing action
- lysozymes helps destroy bacteria
What are the 2 main stages of swallowing?
- Voluntary stage
- Involuntary stages
What are the involuntary stages?
- Pharyngeal stage
- Esophageal stage
What is the voluntary stage of swallowing?
oral cavity to oropharynx
What is the Pharyngeal stage
of swallowing?
pharynx to esophagus
What is the esophageal stage of swallowing?
esophagus to stomach
What process starts the voluntary stage of swallowing?
deglutition (swallowing)
What is deglutition?
food bolus pushed by the tongue into the oropharnyx
What process starts the involuntary stage of swallowing?
sensory nerves in pharynx signal deglutition center in brain
What all happens during the pharyngeal stage of swallowing?
- breathing stops
- soft palate and uvula rise closing off nasopharynx
- vocal cords adduct
- larynx rises
- epiglottis covers the larynx
What all happens during the esophageal stage of swallowing?
- upper esophageal sphincter relaxes
- peristalsis pushes food down (circular fibers contract behind food and longitudinal fibers contract in front)
- travel time (4-8 for food and 1 sec for liquid)
- lower esophageal sphincter relaxes as food approaches
What happens if the lower esophageal sphincter doesn’t open?
- distension of esophagus fees like chest pain or heart attack
What happens if the upper esophageal sphincter doesn’t close?
- stomach acid enters esophagus and causes “heartburn” (GERD)
- worsened by laying down, smoking, or weak sphincter
