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Clinical Anatomy Course > 12. Alimentary Tract > Flashcards

12. Alimentary Tract Flashcards

1
Q

Where is the oral cavity?

A
  • The oral cavity is situated immediately inferior to the nasal cavities, and is formed of a roof, floor and two walls.
  • The anterior region of the cavity communicates with the external environment via the oral fissure (mouth), and posteriorly, the cavity communicates with the oropharynx.
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2
Q

What forms the roof of the oral cavity?

A
  • Hard palate anteriorly (palatine process of the maxilla and horizontal plate of the palatine)
  • Soft palate posteriorly.
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3
Q

What forms the floor of the oral cavity?

A
  • Tongue
  • Openings of submandibular and sublingual salivary glands
  • Mylohyoid muscles
  • Geniohyoid muscles
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4
Q

What forms the walls of the oral cavity?

A
  • Buccinator muscle (CN VII) externally
  • Lined internally by non-keratinised stratified squamous epithelium (oral mucosa)
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5
Q

What is the oral vestibule?

A

The part of the oral cavity in front of the teeth.

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6
Q

What controls the size of the oral fissure?

A
  • Orbicularis oris
  • Buccinator
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7
Q

What structure passes through the buccinator muscle?

A

Parotid duct

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8
Q

What is the innervation to the hard and soft palates?

A
  • Hard palate -> Maxillary branch of the trigeminal nerve (CN 5)
  • Soft palate -> Glossopharyngeal nerve (CN 9)
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9
Q

What is the innervation to the floor of the oral cavity?

A

Mandibular nerve of trigeminal nerve (CN 5) -> Lingual branch

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10
Q

What is the soft palate continuous with?

A
  • Continuous with the wall of the pharynx
  • Joined to the tongue and pharynx by the palatoglossal and palatopharyngeal arches
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11
Q

Describe movements of the soft palate.

A
  • During chewing it is pulled down against the posterior part of the tongue (by palatoglossus) to separate the mouth from the oropharynx
  • During swallowing it is pulled up and tensed (levator and tensor palati) to separate the oropharynx from the nasopharynx.
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12
Q

What is the oropharyngeal isthmus and how is it controlled?

A
  • The boundary between the oral cavity and the oropharynx
  • It can be opened and closed by moving the soft palate
  • Palatoglossus pulls the soft palate down to close the junction between the oral cavity and oropharynx during chewing
  • During swallowing, the soft palate is pulled up (levator and tensor palati) to separate the oropharynx from the nasopharynx
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13
Q

Summarise the innervation of the oral cavity.

A

Roof:

  • Hard palate -> Maxillary branch of trigeminal (CN 5)
  • Soft palate -> Glossopharyngeal nerve (CN 9)

Floor, lower teeth and cheeks:

  • Mandibular branch of trigeminal (CN 5) -> Lingual

Tongue:

  • Anterior 2/3rd sensation -> Mandibular branch of trigeminal (CN 5)
  • Anterior 2/3rd taste -> Chorda tympani of facial nerve (CN 7)
  • Posterior 1/3rd -> Glossopharyngeal nerve (9)
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14
Q

How many teeth do adults have?

A

32

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15
Q

What are the different types of teeth?

A
  • Incisors -> Thin, cutting edges.
  • Canines -> Single, prominent cones.
  • Premolars -> Bicuspid teeth.
  • Molars -> Three cusped teeth.
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16
Q

Pain can be referred to the teeth from where?

A

Maxillary sinus

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17
Q

What innervates the intrinsic and extrinsic muscles of the tongue?

A

Hypoglossal nerve, except the palatoglossus, which is innervated by the vagus nerve.

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18
Q

Where is the mylohyoid muscle and what is its function?

A
  • Passes from the mandible to the hyoid bone, reinforcing the floor of the mouth.
  • When it contracts, it elevates the hyoid and the tongue.
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19
Q

What important structures attach to the mandible?

A
  • Tongue (via the genioglossus muscle)
  • Mylohyoid muscle (attaches to the mandible and hyoid)
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20
Q

What is a consequence of mandibular fractures?

A
  • Patients with bilateral mandibular body fractures are especially at risk for tongue base prolapse – the fracture may cause the fractured symphysis to slide posteriorly towards the oropharynx, along with the tongue attached to it via its anterior insertion, causing oropharyngeal obstruction in the supine patient.
  • This is a medical emergency as the airway is likely to be compromised.

Summary: Respiratory obstruction can occur with bilateral mandible fracture.

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21
Q

For each salivary gland, draw the location, innervation and ducts.

A
  • Parotid gland
    • Posterior to the cheeks and anterior to the external ear
    • Stensen’s (parotid) duct -> Pierces the buccinator, to drain into the oral cavity adjacent to the second upper molar tooth
    • Innervated by glossopharyngeal nerve via otic ganglion
  • Submandibular gland
    • Submandibular triangle of the neck, beneath the floor of the oral cavity
    • Wharton’s (submandibular) duct -> Drains into the oral cavity through 1-3 orifices at the base of the frenulum of the tongue
    • Innervated by facial nerve via chorda tympani and submandibular ganglion
  • Sublingual gland
    • Floor of the oral cavity, under the tongue
    • Multiple sublingual ducts -> Drain into the sublingual folds under the tongue
    • Innervated by facial nerve via chorda tympani and submandibular ganglion
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22
Q

What nerve and ganglion does innervation to the parotid salivary glands occur via?

A
  • Nerve: Glossopharyngeal nerve
  • Ganglion: Otic ganglion
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23
Q

What nerve and ganglion does innervation to the submandibular and sublingual salivary glands occur via?

A
  • Nerve: Chorda tympani of facial nerve
  • Ganglion: Submandibular ganglion
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24
Q

What is the blood supply to each of the salivary glands?

A
  • Submandibular and sublingual -> Facial artery
  • Parotid -> Posterior auricular and superficial temporal arteries
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25
Q

What structures pass through the parotid gland?

A
  • Facial nerve
  • Major vessels (check what thrse are)
26
Q

What structures are closely related to the submandibular gland?

A

Facial artery loops over the submandibular gland

27
Q

Which nerve may be damaged by surgery or tumours of the parotid gland?

A

Facial nerve

28
Q

Describe salivary stones.

A
  • Stones can form in the major salivary glands and their ducts, causing blockage of salivary outflow, particularly causing pain and swelling at mealtimes.
  • Blockage is most commonly seen in the submandibular and parotid ducts.
  • The papillae of the salivary ducts are the last narrow points before reaching the oral cavity, and are therefore where small stones are often found.
  • Stones are formed of mucus, debris and calcium.
29
Q

What parts of the mandible do you need to know about?

A
  • Body
  • Ramus
  • Coronal process
  • Condylar process
30
Q

Describe the temporo-mandibular joint.

A

The articulating surfaces are:

  • Head of mandible
  • Glenoid fossa of temporal bone

Within each part of the joint, an articular disc separates the joint into upper and lower joint cavities. The upper joint cavity is a sliding joint, allowing the protrusion and retrusion of the mandible. The lower joint cavity primarily acts as a hinge joint, but some rotation is permitted. This is associated with the grinding motion of the teeth during chewing.

31
Q

What type of joint is the temporomandibular joint?

A

Bicondylar joint

32
Q

What movements are possible at the temporomandibular joint?

A
  • Protrusion/retrusion
  • Opening/closing
  • Lateral movements
  • This is associated with the grinding motion of the teeth during chewing.
33
Q

What muscles controlling jaw movements do you need to know?

A

Opening:

  • Digastric -> Depresses jaw
  • Lateral pterygoid -> Protracts the head of the mandible for wide opening

Closing:

  • Masseter
  • Temporalis
  • Medial pterygoid

Lateral movements:

  • Medial pterygoid
  • Lateral pterygoid
34
Q

What is the function of the digastric muscle?

A

Depresses the jaw during opening

35
Q

What are the attachments and function of the masseter muscle?

A
  • Origin: Zygomatic arch
  • Insertion: Mandible
  • Function: Closes the jaw
36
Q

What are the attachments and function of the temporalis muscle?

A
  • Origin: Temporal bone
  • Insertion: Coronoid process of mandible
  • Function: Closes the jaw
37
Q

What are the attachments and function of the medial pterygoid muscle?

A
  • Origin: Sphenoid, palatine and maxillary bones
  • Insertion: Medial surface of ramus of mandible
  • Function: Closes the jaw and lateral movements
38
Q

What are the attachments and function of the lateral pterygoid muscle?

A
  • Origin: Sphenoid bone
  • Insertion: Condyle of mandible
  • Function: Opening (Pulls head of mandible forward) and lateral movements
39
Q

What is the motor innervation to the muscles of mastication?

A

Mandibular branch of trigeminal nerve (CN 5)

40
Q

What nerve passes through the mandible? What is its function?

A
  • Inferior alveolar nerve (a branch of the mandibular branch of the trigeminal nerve)
  • Passes through the mandibular canal via the mandibular foramen on the inner aspect of the mandible
  • Innervates the lower teeth and gives off the mental nerve that supplies the skin of the chin and lower lip
41
Q

How can dislocation of the temporomandibular joint occur? How can it be reduced?

A
  • TMJ dislocation occurs when the condylar process moves anterior of the articular eminence and fails to return to its normal position.
  • This can occur during over-opening of the mouth
  • Manual reduction involves depression of the mandible by pushing down on the molars to enable the condylar process to return to the joint
42
Q

What are the three parts of the pharynx?

A
  • Nasopharynx
  • Oropharynx
  • Laryngopharynx

Note how the larynx is continuous with the trachea, while the laryngopharynx is continuous with the oesophagus.

43
Q

What is the pharynx?

A

The pharynx is the superior, expanded portion of the alimentary tract, responsible for directing food towards the oesophagus during swallowing.

44
Q

Where is the nasopharynx and what does it contain?

A
  • Located between the base of the skull and the soft palate.
  • Contains:
    • Eustachian (at level of inferior nasal concha)
    • Adenoid tonsils
45
Q

Where is the oropharynx and what does it contain?

A
  • Extends from the soft palate to the superior border of the epiglottis.
  • Contains:
    • Palatine tonsils (within the tonsillar fossa)
    • Lingual tonsils (at the base of the tongue)
    • Superior pharyngeal constrictor
46
Q

Where is the laryngopharynx and what does it contain?

A
  • From the superior part of the epiglottis to the inferior border of the cricoid cartilage at the level of C6.
  • Contains:
    • Middle and inferior pharyngeal constrictors
47
Q

What are the pharyngeal constrictors?

A

The muscles that make up the walls of the pharynx:

  • Superior constrictor muscle -> Found in oropharynx
  • Middle and inferior constrictor muscles -> Found in laryngopharynx
48
Q

What is the cricopharyngeal sphincter and what is its function?

A
  • A muscle just below the cricoid cartilage in the laryngopharynx
  • It is tonically contracted at rest but it relaxes during swallowing to allow food to pass
49
Q

What is the retropharyngeal space?

A
  • A space in the mid-line posterior to the pharynx and oesophageal posterior walls that extends from the base of the skull to the thoracic spine.
  • The space normally contains areolar fat and lymph nodes (above the hyoid bone).
  • Posterior to the retropharyngeal space is the so called “Danger Space”, which extends from the skull base to the posterior mediastinum.
50
Q

What is the significance of the retropharyngeal space?

A

Spread of infection:

The direct communication of the danger space with the posterior mediastinum, and the free communication with the left and right sides, means that infection of this space, from sources such as retropharyngeal abscesses, from can directly spread to the thorax, causing life threatening sepsis.

51
Q

Where is the pharyngo-tympanic tube and what does it connect?

A
  • It is found in the nasopharynx at the level of the inferior meatus.
  • It connects it to the middle ear
52
Q

Summarise the movements of the mouth, tongue, soft palate and pharynx during chewing and swallowing.

A
  • The muscles of mastication facilitate the chewing, cutting and grinding of ingested food into a semi-solid bolus.
  • Soft palate is pulled down against the posterior part of the tongue by palatoglossus -> This separates the mouth from the oropharynx

Voluntary stage:

  • Extrinsic tongue muscles elevate tongue and compress bolus against hard palate.
  • Intrinsic tongue muscles create a trough in the back of the tongue that force the bolus into the oropharynx.

Involuntary stage:

  • Soft palate is pulled up by the levator veli palatini (vagus nerve) and tensor veli palatini (mandibular branch of trigeminal) -> This seal off the nasopharynx from the oropharynx.
  • The pharynx then widens.
  • The larynx is elevated by the suprahyoid group of muscles -> This closes the larynx by causing the epiglottis to close over its inlet.
  • Cricothyroid sphincter relaxes to allow food to enter.
  • Superior, middle and inferior pharyngeal constrictor muscles (vagus nerve) forces food into the oesophagus.
53
Q

What muscles elevate the soft palate during swallowing and what is their innervation?

A
  • Levator veli palatini (vagus nerve)
  • Tensor veli palatini (mandibular branch of trigeminal)
54
Q

What happens to the larynx during swallowing?

A
  • Larynx is elevated by the suprahyoid group of muscles.
  • This closes the larynx by causing the epiglottis to close over its inlet.
55
Q

What innervates the pharyngeal constrictor muscles?

A

Vagus nerve

56
Q

Describe the gag reflex.

A
  • Afferent: Glossopharyngeal nerve detects posterior pharyngeal wall pressure
  • Efferent: Vagus nerve causes rapid elevation of the soft palate and contraction of the pharyngeal muscles.

This is a consensual reflex, meaning the soft palate elevates in a symmetrical manner regardless of the side touched.

57
Q

In general, differentiate between the function of the vagus and glossopharyngeal nerves in the neck region.

A
  • Glossopharyngeal nerve -> Sensory to oropharynx
  • Vagus nerve -> Motor to palate, pharynx and larynx, Sensory to larynx
58
Q
A
59
Q

What are the tonsils you need to know about?

A
  • Palatine tonsils
  • Pharyngeal tonsils (a.k.a. adenoids)
60
Q

Describe tonsillitis.

A
  • Tonsillitis describes inflammation of the tonsils due to infection.
  • Patients complain of sore throat and difficulty swallowing.
  • Most cases of tonsillitis are viral and so should be managed with pain relief, hydration and lozenges.
  • Antibiotics should only be given if the tonsillitis is likely to be bacterial in nature: a lack of cough, pus on the tonsils, fever above 38°C and swollen neck lymph nodes all increase the likelihood of the infection being bacterial.
  • If tonsillitis becomes a recurrent problem, patients can undergo a surgical excision of the tonsils (tonsillectomy).
61
Q
A

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