42 Questions
What is the primary function of the gastrointestinal system?
Digestion and absorption of nutrients
What is the role of sphincters in the gastrointestinal system?
To regulate the passage of food from one compartment to another
What is the term for the chemical breakdown of ingested food into absorbable molecules?
Digestion
Which of the following is an example of an accessory gland in the gastrointestinal system?
Pancreas
What is the term for the propulsion and mixing of ingested food in the gastrointestinal system?
Motility
What is the term for the absorption of nutrients, electrolytes, and water from the lumen into the bloodstream?
Absorption
What is the layer of the gastrointestinal tract that comes into contact with ingested food?
Mucosa
What is the term for the release of substances such as enzymes and hormones from cells in the gastrointestinal system?
Secretion
What is the primary function of the UES during the pharyngeal phase of swallowing?
To prevent reflux into the pharynx
What is the mechanism that propels the bolus through the open UES during the pharyngeal phase?
Initiation of a peristaltic wave of contraction in the pharynx
What is the name of the wave-like muscular contractions that move the bolus along the GIT?
Peristalsis
What is the function of the soft palate during swallowing?
To separate the oropharynx from the nasopharynx
What is the primary function of the oral phase of swallowing?
To chew and mix food with saliva
What is the name of the phase of swallowing that involves the movement of the bolus from the pharynx into the esophagus?
Pharyngeal phase
What is the mechanism that prevents reflux into the pharynx during swallowing?
Closure of the UES
What is the purpose of secondary peristalsis in the esophagus?
To clear the bolus from the esophagus
What is the primary function of salivary amylase in the mouth?
To break down complex carbohydrates
What is the mechanism that prevents food from entering the nasopharynx during swallowing?
Closure of the soft palate
What triggers the secondary peristalsis in the esophagus?
Distension of the esophagus
What is the role of VIP in the swallowing process?
It mediates the relaxation of the lower esophageal sphincter
What is the velocity of the primary peristalsis in the esophagus?
3-5 cm/s
What is the mechanism that pushes the food bolus down the esophagus?
Peristaltic wave triggered by the distension of the esophagus
What happens when the primary peristalsis fails to clear the bolus?
A secondary peristalsis is initiated
What is the role of the jaw muscles during the swallowing process?
They relax during the swallowing process
What is the state of the UES and LES at rest?
UES and LES are both tonically constricted
What happens to the UES and LES during swallowing?
UES relaxes, LES remains contracted
What is the characteristic of Achalasia?
Impaired relaxation of the LES in response to swallowing
What is the result of Achalasia?
Food builds up in the esophagus behind the closed LES
What is the cause of Achalasia?
Selective loss of inhibitory neurons
What is the most common symptom of Achalasia?
Dysphagia and regurgitation
What is one of the treatment options for Achalasia?
All of the above
What is the cause of LES dysfunction?
Reduced resting LES pressure
What is the primary function of the stomach in terms of food storage?
To provide a reservoir for up to 1.5 L of food without increasing pressure
Which region of the stomach is primarily responsible for mixing food with gastric secretions?
Antrum
What is the role of the lower esophageal sphincter (LES) in the process of swallowing?
To open before the arrival of food to allow it to pass into the stomach
What is the term for the relaxation of the stomach in preparation for food entry?
Receptive relaxation
What is the primary mechanism by which the stomach relaxes to accommodate food?
Relaxation of smooth muscle through vagal fibers
What is the role of VIP in the stomach?
To relax the smooth muscle of the stomach
What is the purpose of the secretion of intrinsic factor in the stomach?
To absorb vitamin B12
What is the consequence of suddenly increasing pressure in the stomach?
Regurgitation of food
What is the role of mucus secretion in the stomach?
To protect the gastric mucosa
What is the term for the controlled release of food from the stomach into the duodenum?
Gastric emptying
Study Notes
Gastrointestinal System and Accessory Organs
- The gastrointestinal (GI) system consists of tubular portions (hollow organs) separated by sphincters and accessory glands and organs, including salivary glands, pancreas, liver, and gallbladder.
- The GI system's main functions are digestion, absorption of nutrients, and propulsion and mixing of ingested food.
Functions of the Stomach
- The stomach stores food (1.5 L capacity) without increasing pressure and relaxes before the arrival of food.
- The stomach mixes food with gastric secretions (HCl and pepsin), mainly in the antrum.
- The stomach controls the emptying of food into the duodenum.
- The stomach secretes HCl to kill microorganisms and convert pepsinogen to its active form, pepsin.
- The stomach also secretes intrinsic factor to absorb vitamin B12 and mucus and HCO3− to protect the gastric mucosa.
- The stomach secretes water for lubrication and to provide an aqueous suspension of nutrients.
Phases of Swallowing
- Voluntary phase: A bolus of food is separated using the tip of the tongue and forced into the oropharynx.
- Pharyngeal phase: Stimulation of touch receptors in the oropharynx initiates this phase, followed by contraction and relaxation of muscles.
- Esophageal phase: The bolus is pushed down the esophagus by primary peristalsis, and if this fails, secondary peristalsis is initiated.
Pharyngeal and Esophageal Motility
- Peristalsis is a wave-like muscular contraction that moves the bolus along the GIT.
- Upper esophageal sphincter (UES) opens, allowing the bolus to move to the esophagus, and then closes to prevent reflux into the pharynx.
- Lower esophageal sphincter (LES) opens before the arrival of the food, mediated by peptidergic fibers in the vagus nerve that release VIP.
LES Dysfunction and Achalasia
- Achalasia is a disorder characterized by impaired LES relaxation in response to swallowing, leading to esophageal distension.
- Symptoms include dysphagia, regurgitation of bland undigested food or saliva, chest pain, heartburn, weight loss, and esophagitis.
- Treatment options include antispasmodic drugs, Botulinum Toxin (Botox) injection, pneumatic dilatation, and Heller Myotomy.
Quiz on the components and functions of the gastrointestinal system, including the tubular portion and accessory organs, as well as the major activities of motility, secretion, and digestion. Learn about the physiology of the GI system. Test your knowledge on the organs involved and their roles.
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