D. Mouth, Pharynx, Esophagus

What are the functions of the mouth in digestion?

Chops food into smaller pieces, mixes it with saliva, forms a slippery bolus, and initiates swallowing. Sensory stimulation triggers the cephalic phase of digestion (feedforward control).

What is the cephalic phase?

A feedforward control phase where sight, smell, or thought of food activates digestive processes in anticipation of food intake.

What glands secrete saliva?

Parotid, sublingual, and submandibular glands.

What are the main components of saliva? What are their functions?

• Mucus (lubricates food & facilitates formation of bolus)

• Water (moistens food and dissolves molecules to facilitate chemoreception)

• Bicarbonate or HCO3 (Neutralizes acids and bacterial metabolites)

• Lysozyme (Kills bacteria to maintain health of gums and teeth)

• Amylase (Digestion of polysaccharides)

• Lipase (Digestion of triglycerides)

Why is saliva important for taste?

It dissolves food molecules so they can interact with taste chemoreceptors.

How is saliva secretion controlled? Which control has the stronger response?

• By both parasympathetic and sympathetic nervous systems

• Parasympathetic has a stronger effect. NO hormonal control.

What is Sjögren's syndrome and how does it affect digestion?

An autoimmune disease that damages salivary glands, causing dry mouth, impaired taste, and difficulty chewing.

How is chewing controlled?

Voluntary action with reflex coordination from brainstem pattern generators and mechanoreceptor input.

What triggers the swallowing reflex?

Pressure receptors in the pharynx stimulated by food or drink pushed by the tongue.

What is the swallowing center and where is it located?

A group of brainstem nuclei in the medulla oblongata that coordinates swallowing reflexes.

What are the steps of swallowing?

a) Tongue pushes the bolus back to the pharynx
b) Soft palate elevates to prevent food from entering the nasal passage
c) Epilogttis covers the glottis to prevent food or liquid from entering the trachea
d) Food goes down the esophagus

What happens to prevent food from entering the nasal cavity during swallowing?

The soft palate elevates to seal off the nasal passage.

What prevents food from entering the trachea during swallowing?

The epiglottis covers the glottis and the glottis itself closes due to raised larynx.

What is peristalsis? What is it adjusted by and what does this adjustment do?

A wave-like muscle contraction that moves food down the esophagus to the stomach.

It's adjusted by afferent inputs which give a secondary peristalsis

What are the two esophageal sphincters?

Upper esophageal sphincter (skeletal muscle) and lower esophageal sphincter (smooth muscle).

What is secondary peristalsis?

Additional peristaltic waves triggered if a food bolus remains in the esophagus.

What prevents backflow from the stomach into the esophagus?

The lower esophageal sphincter and abdominal pressure balance help maintain a barrier.

What is gastroesophageal reflux (acid reflux)?

A condition where stomach acid enters the esophagus due to a weak lower esophageal sphincter.

What is GERD triggered by?

1. Smoking

2. Alcohol

3. Caffeine

4. Big meal

What are the complications of GERD?

1. Ulcer
2. Scarring
3. Obstruction
4. Esophageal perforation

What causes heartburn?

Irritation of the esophageal walls by hydrochloric acid from the stomach during acid reflux.

Why is acid reflux common during pregnancy?

Increased abdominal pressure and upward displacement of the esophagus through the diaphragm.