12 - GI: Mouth to Esophagus - Mastication and Deglutition

What are the 5 organs of the alimentary canal? (not accessory)

- Esophagus

- Stomach

- Small intestine (duodenum, jejunum, ileum)

- Large intestine

- Anal canal

What are the 6 accessory organs of the gastrointestinal system?

- Mouth

- Teeth

- Salivary glands

- Liver

- Gallbladder

- Pancreas

What are the 6 basic processes of the GI system?

1. Ingestion (eating food)

2. Secretion (secreting enzymes via glands)

3. Motility (mixing and propulsion of food and secretions)

4. Digestion (digesting food particle into small food molecules)

5. Absorption (absorbing small food molecules into bv + lymphatic vessel)

6. Defecation (poop!)

What is mastication and deglutition?

Mastication = chewing

Deglutition = swallowing

What area constitutes the oral cavity?

Space between the gums and teeth to the fauces (passages) as part of the pharynx

What are the structures in the oral cavity?

Superior + inferior labial frenulum - holds lipgs together, prevents excess movement

Hard + soft palate - located top of mouth, consists of bony part of skull and muscles respectively

Uvula - located in center of mouth, contains irritant and touch receptors that activate the vomiting reflex

Lingual frenulum - holds tongue together

Submandibular gland - located at bottom of tongue, produces saliva reflex

Cheek - prevents food from "falling out"

Teeth - crushes food

Gums

Tongue

What are the 5 primary tastes sensed by the taste buds?

1. Sweet

2. Bitter

3. Salty

4. Sour

5. Umami (savory) via MSG

What are the 4 different taste buds found on the papillae?

1. Vallate papillae - 12 papillae, consisting of 100-300 taste buds (valley)

2. Fungiform papillae - scattered over tongue, each containing 5 taste buds (mushroom)

3. Foliate papillae - located in lateral margins of tongue, degenerate in childhood (why we hate vegetables during childhood)

4. Filiform papillae - tactile sensations and friction (helps generate a bolus)

What cell generates an action potential based on taste in the taste buds?

Gustatory receptor cell, sends AP to gustatory center in brain

What is the motor (including glands) and sensory function of the facial nerve CN VII in the mouth?

Motor Function

Controls secretions from sublingual and submandibular gland

Controls muscles of facial expression

Sensory Function

Responsible for taste/gustation sensation in the anterior 2/3rds of the tongue

What is the motor (including glands) and sensory function of the glossopharyngeal nerve CN IX in the mouth?

Motor Function

Controls secretions from parotid salivary gland

Sensory Function

Responsible for taste/gustation sensation in the posterior 13rd of the tongue

What is the sensory function of the vagus nerve CN X in the mouth?

Responsible for taste/gustation sensation in the thorat and the tongue

What is the motor and sensory function of the trigeminal nerve CN V in the mouth?

Motor Function

Controls muscles of mastication in the mouth

Sensory Function

Conveys tactile sensations from the tongue

Conveys sensations in the tooth (ex: tooth ache)

What is the motor function of the hypoglossal nerve CN XII in the mouth?

Controls intrinsic and extrinsic muscles of the tongue

What are the four different types of teeth in the mouth and what are their functions?

1. Incisors -> cutting (4 in front)

2. Canines -> tearing (2 beside incisors)

3. Premolars -> crushing (4 in front of molars)

4. Molars -> grinding (6 in the back)

How many dentitions do humans have?

Two dentitions

-> Deciduous (falling out/baby teeth)

-> Permanent (after deciduous teeth fall out)

How many teeth does the mouth contain?

32 teeth in full set, 16 on top, 16 on bottom

What holds teeth in place, and what are they made out of?

Teeth are held in place by periodontal ligaments, which are composed of collagen, which require vit C. (scurvy)

What is the role of enamel in the teeth?

Hardest substance in teeth and the body, consists of 95% calcium salts, harder than bone (bone = 50% calcium salts), protects the teeth

What is the role of dentin in the teeth?

Hard substance in the teeth, consists of 70% calcium salts, harder than bone (bone = 50% calcium salts), protects the teeth

What is the role of pulp in the teeth?

Connective tissue of the teeth, supplied by neurovascular bundle (nerves + bvs)

What structures are involved in mastication in the mouth?

Muscles of mastication

Teeth, tongue, cheeks, and lips (crushes + maneuvers food, prevents food from falling out of mouth)

Salivary glands (chemical digestion), includes sublingual, submandibular, and parotid glands

What is the role of the sublingual gland in the mouth? Which nerves is it innervated by?

Secrets...

mucin - mucous gland, teachers mouth

lipase - digests lipids, activated in the stomach

Innervated by CN VII Facial Nerve and SNS

What is the role of the submandibular gland in the mouth? Which nerve is it innervated by?

Secrets...

Serous - "water"

Amylase - breakdown starch, minor player

Innervated by CN VII facial nerve

What is the role of the parotid gland in the mouth? Which nerve is it innervated by?

Secrets...

Serous - "water"

Amylase - breakdown starch, major player

Innervated by CN XI Glossopharyngeal nerve

What are the 4 intrinsic muscles of the tongue? What is their role and what nerve are they innervated by?

Muscles inside of the tongue, helps change shape of the tongue to aid in speech and swallowing, consists of skeletal muscle which are controlled voluntarily

1. Superior longitudinal muscle

2. Inferior longitudinal muscle

3. Transverse muscles (make tongue thinner)

4. Vertical muscles (flatten tongue)

Innervated by hypoglossal nerve CN XII

What are the 4 extrinsic muscles of the tongue? What is their role and what nerve are they innervated by?

Muscles outside of the tongue, helps shape food into a bolus and maneuver food for mastication and swallowing

1. Hyoglossus (Retraction + depression)

2. Genioglossus (Protrusion -> stick out tongue)

3. Styloglossus (Elevation)Wh

Innervated by the hypoglossal nerve CN XII

Which extrinsic muscle of the tongue allows you to stick it out?

Genioglossus -> innervated by hypoglossal nerve CN XII

What are the 2 muscles of facial expression? What is their role and what nerve are they innervated by?

Responsible for facial expression by having an action on the cheek, lips and mouth

1. Buccinator (integrity of cheek)

2. Orbicularis oris (closes lips)

Innervated by the facial nerve CN VII

What are the 4 muscles of mastication? What is their role and what nerve are they innervated by?

Responsible for moving the mandible against the maxilla (Mandible-> chew <-Maxilla) to assist in chewing and talking

1. Temporalis (crunches with mandible)

2. Masseter (talking + chewing)

3. Lateral pterygoid (protrusion of mandible)

4. Medial pterygoid (moving jaw side to side)

Innervated by trigeminal nerve CN V

What are two kinks in the passageway of the esophagus that requires a slight deviation from it's route?

Kink #1 -> bifurcation of the trachea

Kink #2 -> left atrium of the heart

What structures does the esophagus pass by?

Extends from oropharynx, through neck and mediastinum (thorax), passes through esophageal hiatus of diaphragm to enter the abdominal cavity

What are the four layers of the esophagus and their roles?

1. Mucosa -> secretes mucous, consists of nonkeratinized stratified squamous epithelium, lamina propria, and muscularis mucosa

2. Submucosa -> consists of smooth muscle and nerves that control mucosa

3. Muscularis -> generates peristaltic contractions

4. Adventitia -> connects esophagus to surrounding tissues

What two muscles coordinate with each other to generate peristaltic contractions?

Circular muscle - contracts to pinch the tube, migrates with the bolus through the esophagus

Longitudinal muscle - contraction shortens the tube/esophagus ahead of the bolus

What is peristalsis?

Responsible for propelling a bolus from the mouth to the stomach

What are the three phases of degluttition?

1. Voluntary - Food is forced to oral cavity by tongue

2. Pharyngeal - Involuntary swallowing (some voluntary control -mostly skeletal muscles), closure of muscles to protect key structures, relaxation of upper esophageal sphincter to allow food into esophagus

3. Esophageal - Food propelled to stomach via peristaltic contractions, lower esophageal sphincter relaxes

What occurs during the voluntary phase of degluttition?

Bolus of food created in mouth is forced towards the back of the oral cavity by the tongue

What occurs during the pharyngeal phase of deglutition?

Beginning of involuntary swallowing, bolus is pushed to oropharynx. This causes the oropharynx to stretch, eliciting a reflex via brain deglutition center.

This reflex causes...

1. the soft pallet and uvula to close, protecting the nasal cavity, 2. the epiglottis to close of the trachea, protecting the trachea. 3. the upper esophageal sphincter to relax, allowing food into the esophagus

What occurs during the esophageal phase of deglutition?

Peristaltic contractions performed by circular and longitudinal muscle pushes to bolus of food towards the stomach. Once it reaches the stomach, the esophageal stretch causes the lower esophageal sphincter to relax, allowing food into the stomach

What is the role of the tongue in deglutition?

Push bolus of food into pharynx

What is the role of the uvula and soft pallet in deglutition?

Protects nasal cavity during swallowing, prevents bolus from entering

What is the role of the epiglottis in deglutition?

Protects trachea during swallowing, prevents bolus from entering

What is the role of the esophagus in deglutition?

Generates peristaltic contractions to push bolus from oral cavity to stomach

What is the role of the upper and lower esophageal sphincters?

Upper esophageal sphincter - relaxes upon stretch to allow food from pharynx into esophagus

Lower esophageal sphincter - relaxes upon stretch to allow food from esophagus into stomach, closes afterwards to prevent HCl acid of stomach to damage mucous lining of esophagus