Anatomy of Oesophagus and Swallowing

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary reason the stomach can accommodate up to one liter of food without increasing intragastric pressure?

The Law of LaPlace states that distending pressure equals the tension in its wall divided by its radius.

The stomach wall has plasticity, allowing it to expand. (correct)

The stomach has a unique type of smooth muscle that resists contraction.

The stomach has a gastric basic electrical rhythm (BER) that regulates pressure.

What is the frequency of gastric slow waves in the stomach?

1-2 cycles/min

9-12 cycles/min

6-8 cycles/min

3-5 cycles/min (correct)

What is the function of tonic gastric waves?

To increase intragastric pressure

To relax the fundus and body of the stomach

To mix food with gastric secretions (correct)

To stimulate the release of gastrin and motilin

What is the effect of vagal stimulation on gastric slow waves?

Increases the frequency of slow waves Signup and view all the answers

What is the primary function of electrolytes like Na, Cl, HCO3, and K in saliva?

Act as coenzymes for salivary enzyme amylase Signup and view all the answers

What is the purpose of receptive relaxation?

To relax the fundus and body to receive a bolus of food Signup and view all the answers

What is the location of the pacemaker of the stomach?

Midpoint of the greater curvature Signup and view all the answers

Which of the following is NOT a function of saliva?

Regulation of body temperature Signup and view all the answers

What is the primary role of ptyalin (salivary α-amylase) in digestion?

Digest starch into maltose, maltotriose, and alpha limit dextrin Signup and view all the answers

What is the frequency of slow waves in the duodenum?

12 cycles/min Signup and view all the answers

What is the role of lingual lipase in digestion?

Digest triglycerides into fatty acids and glycerol Signup and view all the answers

What is the effect of sympathetic stimulation on gastric slow waves?

Decreases the frequency of slow waves Signup and view all the answers

What is the primary role of kallikrein enzyme in saliva?

Produce bradykinin, which acts as a vasodilator Signup and view all the answers

What is the primary composition of saliva in the salivary acini stage?

Isotonic with Na+ = 150mmol/L, K = 10 mmol/L, Cl = 113 mmol/L, HCO3- = 23-30 mmol/L Signup and view all the answers

What is the primary function of bicarbonate and phosphate systems in saliva?

Maintain the pH of the mouth at 7.0 Signup and view all the answers

What is the role of saliva in facilitating taste sensation?

Serves as a solvent for molecules that stimulate taste receptors Signup and view all the answers

What is the primary role of cholagogues in the gallbladder?

To evacuate the bile from the gallbladder and increase its flow Signup and view all the answers

During which phase of gastric secretion does vagal stimulation occur?

Cephalic phase Signup and view all the answers

What is the primary source of bile salts in the intestine?

Bacterial effect on dry salts Signup and view all the answers

What percentage of bile salts are reabsorbed from the terminal ileum back to the liver?

90-95% Signup and view all the answers

What is the normal rate of bile salts secretion?

0.3 gm/day Signup and view all the answers

What is the name of the primary bile salts formed from cholesterol?

Tauro- and glyco-salts of cholic and chenodeoxycholic acids Signup and view all the answers

What is the main difference between the muscle layers of the upper and lower portions of the oesophagus?

The upper portion has striated muscle, while the lower portion has smooth muscle. Signup and view all the answers

What is the role of the vagovagal reflex in the oesophagus?

It controls the peristalsis in the upper portion of the oesophagus. Signup and view all the answers

During the pharyngeal phase of swallowing, what happens to the glottis?

It closes to prevent food from entering the air passages. Signup and view all the answers

What is the function of the palatopharyngeal folds during the pharyngeal phase of swallowing?

They allow small food particles to pass through, while preventing large particles from entering the air passages. Signup and view all the answers

What is the duration of the pharyngeal phase of swallowing?

1 second Signup and view all the answers

Which nerve is responsible for transmitting the afferent signal during the swallowing reflex?

Glossopharyngeal nerve Signup and view all the answers

What is the function of the superior pharyngeal muscle during the pharyngeal phase of swallowing?

It contracts to facilitate rapid pharyngeal peristalsis. Signup and view all the answers

What is the term for the temporary cessation of breathing during the pharyngeal phase of swallowing?

Swallowing apnea Signup and view all the answers

What is the primary cause of secretory diarrhea in cholera?

Increased secretion of NaCl and H2O Signup and view all the answers

What is the typical pH range of pancreatic secretion?

7.8 - 8.3 Signup and view all the answers

What is the function of alpha cells in the pancreas?

To produce glucagon Signup and view all the answers

What is the primary complication of diarrhea?

Dehydration and hypovolemic shock Signup and view all the answers

What is the type of pancreatic secretion stimulated by secretin hormone?

Aqueous alkaline secretion Signup and view all the answers

What is the typical volume of pancreatic secretion per day?

1 - 1.5 L/day Signup and view all the answers

What is the primary function of the exocrine pancreas?

To secrete digestive enzymes Signup and view all the answers

What is the name of the sphincter that surrounds the common opening of the pancreatic duct and common bile duct?

Sphincter of Oddi Signup and view all the answers

Study Notes

Oesophagus

The oesophagus is a muscular tube with outer longitudinal and inner circular muscle layers, which are striated in the upper portion and smooth in the lower portion.
Peristalsis in the upper portion depends on the vagovagal reflex, while in the lower portion it depends on the local enteric reflex.

Swallowing (Deglutition)

Swallowing is the propelling of food bolus from the mouth to the stomach, controlled by the swallowing center in the medulla.
It is divided into three phases:
- Buccal phase: voluntary elevation and retraction of the tongue against the hard palate, propelling the bolus to the pharynx.
- Pharyngeal phase: involuntary, rapid (1 second), and occurs reflexly via the swallowing reflex, which involves:
  - Receptor: in the oropharynx (tonsillar pillars).
  - Afferent: glossopharyngeal nerves.
  - Center: medulla oblongata (swallowing center).
  - Efferent: motor fibers of cranial nerves V, IX, X, and XI.
  - Response: series of reflexes to prevent entry of food into air passages, including:
    - Elevation of the soft palate, closing the nasal cavity.
    - Approximation of palatopharyngeal folds, forming a sagittal slit.
    - Closure of the glottis, and elevation of the larynx and folding of the epiglottis.
    - Inhibition of breathing (swallowing apnea).
    - Relaxation of the pharyngoesophageal sphincter and contraction of the superior pharyngeal muscle, resulting in rapid pharyngeal peristalsis.

Saliva

Saliva has various functions, including:
- Facilitating speech and deglutition by lubricating food with mucin.
- Cleaning the mouth by washing and antibacterial effects of lysozymes, thiothianate ions, and immunoglobulins A.
- Buffering function: maintaining pH at about 7.0 by bicarbonate and phosphate systems, preventing decalcification of teeth.
- Digestive function: containing ptyalin (salivary α-amylase) that digests starch to maltose, maltotriose, and alpha-limit dextrin.
- Excretory function: excreting lead, mercury, iodides, fluoride, and some drugs.
- Facilitating taste sensation: serving as a solvent for molecules that stimulate taste receptors.
- Containing kallikrein enzyme that produces bradykinin, which acts as a vasodilator during salivary secretion.
- Regulating water balance: decreasing in dehydration and giving a thirst sensation.

Stages of Salivary Secretion

I) Salivary acini (primary) → saliva similar in composition to plasma (isotonic).

Gastric Motility

Filling and storage of food in the stomach:
- Accommodating up to one liter of food without increasing intragastric pressure due to plasticity of the gastric wall, receptive relaxation, and the law of LaPlace.
Gastric basic electrical rhythm (BER) (gastric slow waves):
- 3-5 cycles/min, due to partial depolarization of circular smooth muscle cells in the stomach wall.
- Some lead to spike potential → peristalsis.
- Frequency of slow waves determines the rate at which action potentials and contractions occur.
- Start at the midpoint of the greater curvature (pacemaker of the stomach).
- Vagal stimulation, gastrin, and motilin increase spike potential rate, while sympathetic stimulation, secretin, and GIP decrease spike potential rate.

Types of Movements of the Stomach

Tonic gastric waves:
- Regular weak contractions (3 waves/min) that maintain intragastric pressure and mix gastric secretion with food.
Receptive relaxation:
- Reflex relaxation of the fundus and body to receive the bolus of food.

Physiology of Pancreas

Pancreatic secretion:
- The pancreas has both endocrine and exocrine glands.
- Exocrine pancreatic secretion:
  - Volume: 1-1.5 L/day.
  - pH: 7.8-8.3.
  - Osmolarity: iso-osmotic with plasma.
  - Ions: Na+, K+, HCO3-, and Cl-.
  - Types: aqueous alkaline juice and enzyme-rich juice.

Bile Secretion

Mechanism of secretion:
- Cholagogue: factors evacuate the bile from the gallbladder and increase flow of bile.
- Secretin hormone stimulates and sympathetic stimulation inhibits secretion.
Mechanism of bile secretion:
- Between meals: the sphincter of Oddi is closed, and the hepatic bile is stored in the bladder to be concentrated and acidified.
- During food intake: the sphincter of Oddi is relaxed, and the bile is evacuated into the intestine.
- After a meal: 90% to 95% of bile salts are actively reabsorbed from the terminal ileum back to the liver via the portal vein and re-excreted in the bile, stimulating more bile secretion (enterohepatic circulation).

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Learn about the muscular tube of oesophagus, its muscle layers, peristalsis, and the process of swallowing or deglutition.