Swallowing Mechanics and Phases

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Questions and Answers

What is the primary component of saliva?

Salivary proteins

Electrolytes

Mucins

Water (correct)

Which enzyme in saliva is responsible for breaking down polysaccharides?

Protease

Lipase

Lactase

Amylase (correct)

What is the primary function of bicarbonate ions in saliva?

Neutralizing acids (correct)

Lubricating the mouth

Moistening food

Enhancing taste

Why is saliva considered hypotonic?

It has more water than solutes. Signup and view all the answers

What happens to sodium (Na+) and chloride (Cl-) ions as saliva flows from acini to ducts?

They are reabsorbed from the saliva. Signup and view all the answers

Which function of saliva contributes to oral hygiene?

Keeps the mouth clean Signup and view all the answers

What role do pacesetter cells play in the gastrointestinal tract?

They regulate the rate of rhythmic contractions. Signup and view all the answers

Which layer of the GI tract wall contains the myenteric plexus?

Muscularis externa Signup and view all the answers

What are the intrinsic nerve plexuses of the gastrointestinal tract known as?

Enteric nervous system Signup and view all the answers

Which of the following is the primary function of the outer longitudinal muscle layer?

Contraction to propel contents Signup and view all the answers

Where are pacesetter cells located in relation to the smooth muscle layers?

Between circular and longitudinal smooth muscle Signup and view all the answers

What is the key physiological role of the submucous plexus in the GI tract?

Controlling secretion and blood flow Signup and view all the answers

Which part of the GI wall structure is responsible for protecting the underlying tissues?

Serosa Signup and view all the answers

What distinguishes the muscularis mucosa from other muscle layers in the GI tract?

It allows for local movements of the mucosa. Signup and view all the answers

Which of the following functions does NOT involve intrinsic nerve plexuses?

Direct control of heartbeat Signup and view all the answers

The serosa is primarily composed of which type of tissue?

Connective tissue Signup and view all the answers

What is the primary function of the lower esophageal sphincter (LES)?

To prevent gastric reflux Signup and view all the answers

In the event of achalasia, what is the main issue with the lower esophageal sphincter?

It fails to relax during swallowing Signup and view all the answers

What role does the soft palate play during the pharyngeal phase of swallowing?

It prevents reflux of food into the nasopharynx Signup and view all the answers

Which of the following best describes the swallowing process?

An all-or-none reflex that occurs sequentially Signup and view all the answers

What is one potential treatment option for achalasia?

Surgery to relax the LES Signup and view all the answers

Which muscular activity occurs during the oral phase of swallowing?

Forceful placement of the bolus by the tongue Signup and view all the answers

What triggers the swallowing reflex?

The presence of food in the pharynx Signup and view all the answers

What happens if there is no peristalsis present in the esophagus?

The LES remains closed to prevent reflux Signup and view all the answers

During which phase does the larynx move forward and upward?

Pharyngeal phase Signup and view all the answers

What is the primary function of the uvula in the oral cavity?

Seals off the nasal passage during swallowing Signup and view all the answers

Which of the following is NOT a role of the tongue?

Produces saliva Signup and view all the answers

What is defined as improper or abnormal contact of teeth?

Malocclusion Signup and view all the answers

What is the first step in digestion?

Mastication Signup and view all the answers

What is the major purpose of chewing?

To grind and mix food with saliva Signup and view all the answers

What role does saliva play in digestion?

It prepares the distal GIT for food Signup and view all the answers

Where are the salivary glands located relative to the oral cavity?

Outside the oral cavity Signup and view all the answers

Which function is NOT associated with the teeth during chewing?

Secretion of digestive enzymes Signup and view all the answers

What term describes the proper alignment of upper and lower teeth?

Occlusion Signup and view all the answers

What is one reflexive response during chewing?

Increase in salivary secretions Signup and view all the answers

What type of motility is primarily responsible for the mixing of food with digestive juices in the GI tract?

Segmentation Signup and view all the answers

Which muscle type controls the rapid transit region of the GI tract?

Involuntary smooth muscle Signup and view all the answers

What is the role of peristalsis in the GI system?

Forward movement of contents Signup and view all the answers

Which of the following correctly describes the control of motility at the ends of the GI tract?

Voluntary only Signup and view all the answers

What type of movement occurs during the process of segmentation?

Mixing and churning Signup and view all the answers

What distinguishes the structural differences in the GI tract wall?

Number of tissue layers Signup and view all the answers

Which region of the GI tract has slow transit characteristics?

Small intestine Signup and view all the answers

What type of muscle is primarily responsible for the voluntary control of defecation?

Skeletal muscle Signup and view all the answers

What basic function does the GI system perform when it exposes contents to the surfaces of the GI tract?

Mixing Signup and view all the answers

Which statement about GI motility is true?

Smooth muscle contracts under involuntary control. Signup and view all the answers

Study Notes

Swallowing

The esophagus is guarded at both ends by sphincters:
- Upper esophageal sphincter (UES)
- Lower esophageal sphincter (LES)
When the LES fails to relax during swallowing, the bolus of food does not enter the stomach. This is called achalasia.
Achalasia can be treated with surgery, drugs to inhibit tone, Botox, or Ca2+ channel blockers.
Swallowing is a sequentially programmed "all or none" reflex.

Phases of Swallowing

Oral phase: When a bolus of food is forced by the tongue to the rear of the mouth to the pharynx.
Pharyngeal phase: The soft palate is pulled upwards to prevent reflux of food into the nasopharynx. The vocal cords pull together, and the larynx moves forward and upward.

Esophageal Phase

The esophagus is divided into a rapid transit region and a slow transit region.
Mixing and the action of digestive juices and enzymes occur in the slow transit region.

GI system

There are 4 main tissue layers of the digestive tract wall:
- Mucosa
- Submucosa
- Muscularis externa
- Serosa
The muscularis externa is made up of two layers:
- Outer longitudinal muscle
- Inner circular muscle
The myenteric plexus is located between the longitudinal and circular muscle in the muscularis externa layer.
The myenteric and submucosal plexuses make up the enteric nervous system.

Motility

Contraction of smooth muscle in the walls of the GI tract is involuntary.
Motility at either end of the GI tract involves skeletal muscle (chewing, swallowing and defecation) and is voluntary.
There are two types of motility in the GI tract:
- Peristalsis: forward movement
- Segmentation: mixing movement

Oral Cavity

Teeth are involved in mastication (chewing).
Malocclusion is improper/abnormal contact of teeth.
Occlusion is when upper and lower teeth fit together when jaws are closed.
The main purposes of chewing:
- Grind & mix food with saliva
- Reflexly ↑ secretions to prepare the distal GIT for food (increase not only salivary, but also gastric and pancreatic secretions).

Saliva

Saliva is produced by 3 pairs of salivary glands located outside the oral cavity.
Saliva is composed of:
- Mostly H2O
- Some electrolytes
- Salivary proteins:
  - Amylase: breaks down polysaccharides into maltose (2 glucose units).
  - Mucus: facilitates swallowing, moistens food, and provides lubrication.
Functions of Saliva:
- Solvent for molecules to stimulate taste buds
- Aids speech
- Keeps teeth and mouth clean
- Contains HCO3- buffers to help neutralize acids from food and bacteria in the mouth.
Isotonic saliva has the same composition as plasma.
Hypotonic saliva has a lower osmolarity than plasma.
Ducts are relatively impermeable to H2O.
Na+ and Cl- are reabsorbed while K+ and HCO3- are added.

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Description

This quiz explores the anatomy and physiology of swallowing, including the roles of the esophageal sphincters and the distinct phases of swallowing. It also covers swallowing disorders like achalasia and the treatment options available. Test your knowledge on the gastrointestinal system's intricacies related to swallowing.