Funtional anatomy and histology of the upper GI tract

Question 1

Identify the three types of lingual papilla

Answer 1

A: filiform papillae. elongated projections of connective tissue covered with highly keratinised stratified equamous epithelium. No taste buds

B: fungiform papillae. mushroom shaped projections. They project above the filiform papilla, visible as small spots to the naked eye. Tastebuds present in the stratified squamous epithelium. More near the tip of the tongue.

C: vallate papillae. large dome shaped structures in the mucosa anterior to the sulcus terminalis. 8-12 in the tongue. Surrounded by invagination lines with stratified squamous epithelium that contains numerous taste buds

Question 2

Describe the structures highlighted.

Answer 2

Taste buds.

Consists of three principal cell types:
Neuroepithelial (sensory) cells contain taste receptors
Supporting cells
Basal cells (stem cells)

Blue arrow: taste pore, small opening onto the epithelial surface

Question 3

How can you distinguish between mucus and serous salivary glands histologically?

Answer 3

A. Mucus acini: tubular cells, light staining

B. Serous acini: spherical cells, darker staining

Question 4

Identify the salivary gland

Answer 4

Parotid gland

Has completely serous acini

Numerous narrow intercalated ducts

Nuclei dark staining and basally located

Question 5

Identify the salivary gland

Answer 5

Sublingual galnd

Mainly mucus glands

large collecting duct

Low numbers of serous acini

Question 6

Identify the salivary gland

Answer 6

Submandibular gland

Mixed gland, mostly serous

Less extensive intercalated ducts

Question 7

Describe the basic structure of the alimentary canal

Answer 7

A: Mucosa, consisting of lining epithelium, underlying connective tissue (lamina propria), muscularis mucosa (smooth muscle)

B. Submucosa, consists of dense irregular connective tissue

C. Muscularis externa, consists of an inner layer of circular muscle and an outer layer of longitudinal muscle

D. Serosa, serous membrane layer of sinple squamous epithelium. Continuous with mesentery in intraperitoneal organs.

Question 8

Label the floor of the oral cavity

Answer 8

Question 9

State 3 functions of the oral cavity

Answer 9

• it is the inlet for digestive system involved with the initial processing of food, which is aided by secretions from salivary glands;
• it manipulates sounds produced by the larynx and one outcome of this is speech;
• it can be used for breathing because it opens into the pharynx, which is a common pathway for food and air.

Question 10

Main sensory nerve that innervates the oral cavity

Answer 10

Trigeminal nerve (and branches)
 Cranial nerve V

Question 11

Role of maxillary nerve [V2]

Answer 11

Innervtes upper parts of the cavity, including the palate, upper teeth, upper lip and cheek

Question 12

Role of mandibular nerve [V3]

Answer 12

Sensory innervation: lower part or oral cavity - teeth and oral part of the tongue, lower lip and cheek

Motor innervation: muscles of mastication

Question 13

Label the muscles of the tongue

Answer 13

Question 14

Innervation of the tongue

Answer 14

Sensory:
Glossopharyngeal nerve [CN IX] - innervates posterior 1/3 of the tongue (pharyngeal part) and carries sensory information about taste and general sensation.

Lingual nerve - branch of mandibular nerve [CN V3] general sensation from the oral part of the tongue,mucosa on the floor of the oral cavity and gingiva associated with the lower teeth. Also carries parasympathetic and taste fibers from the oral part of the tongue that are part of the facial nerve

Facial nerve [CN VII] - carries sensory information about taste from the oral part of the tongue to the CNS

Motor:
Most muscles of the tongue are innervated by the hypoglossal nerve [CN XII] except for the palatoglossus which is innervated by the vagus nerve [CN X]

Question 15

Sense of taste

Answer 15

Glossopharyngeal nerve [CN IX]

Lingual nerve [CN V3 branch]

Facial nerve [CN VII]

Question 16

State the function of the highlighted structures

Answer 16

Buccinator: Forms wall of the oral cavity (cheek). Holds cheeks against the alveolar arches and keeps food between the teeth when chewing, involved in facial expression.
Motor innervation [CN VII], Sensory innervation [CN V3]

Orbicular oris: Lies within lips around oropharynx. Enables shape of lips to change, keeps mouth clsoed during swallowing.

Hyoid bone: connects floor of the oral canvity with pharynx and larynx. Involved in swallowing.

Hyoglossus: extrinsic muscle of the tongue. Depresses the tongue

Mylohyoid: provides structural support to the oral cavity, depresses mandible and opens mouth, elevates hyoid bone during swallowing,

Question 17

Muscles of mastication (4)

Answer 17

Masseter: elevates mandible

Temporalis: Elevation and retraction of mandible

Medial pterygoid: Elevation and lateral movements of mandible

Lateral pterygoid: Protrusion and lateral movenents of mandible

Also…
Orbicularis oris: narrows mouth and closes lips

Buccinator: Contraction of the buccinator presses the cheek against the teeth. This keeps the cheek taut and aids in mastication by preventing food from accumulating between the teeth and the cheek.

Question 18

Functions of saliva (4 points)

Answer 18

Solvent - taste and absorption

Lubrication - mastication, blous formation, articulation

Digestion - starch triglycerides

Protection - rinse, anti-abrasion, buffer, controls bacterial flora

Question 19

What are the 8 components of saliva?

Answer 19

Ions - Na, K, Ca, F, Mg, PO₄, HCO₃
Mucin
Digestive enzymes
Antibacterial agents (lysozyme, lactoferrin)
Immunoglobulins
Phosphoproteins
Blood group factors

Question 20

Identify the labelled structures

Answer 20

Question 21

Function of the palate

Answer 21

Hard palate: bony plate covered by mucosa. Separates the nasal cavity from the oral cavity.

Soft palate: continues posteriorly from the hard palate and acts as a valve that can be depressed to help close the oropharyngeal isthmus or elevated to separate the nasopharynx from the oropharynx.

Question 22

What are the roles of levator palati and tensor palati muscles?

Answer 22

Levator palati: elevates the soft palate above its neutral position

Tensor palati: tenses the soft palate, opens pharyngeotympanic tube (middle ear) during yawning and swallowing

Question 23

Describe the skeletal structure of the palate

Answer 23

Palatine processes from the maxilla make up the anterior 2/3 of the hard palate

L-shape palatine bones also contribute to the roof of the oral cavity.

Sphenoid and temporal bones provide attachments for muscles of the hard and soft palate.

Question 24

Role of pharyngeal constrictor muscles

Answer 24

Narrow or constrict the pharyngeal cavity. When the constrictor muscles contract sequentially during swallowing they move the bolus of food through the pharynx and into the oesophagus

Question 25

Describe the structure of the pharyngeal wall

Answer 25

The pharyngeal wall is formed by skeletal muscles and by fascia. Gaps between the muscles are reinforced by the fascia and provide routes for structures to pass through the wall. Muscles areattached to the pharyngeal raphe posteriorly while the anterior line of attachment is discontinuous.

Question 26

Describe the changes in the muscle layer of the oesphagus along its length.

Answer 26

Upper third - skeletal muscle Middle third - mixed skeletal and smooth muscle Lower third - smooth muscle

Question 27

Describe the organisation of the oesphageal wall

Answer 27

Mucosa: non-keratinised stratified squamous epithelium lamina propria muscularis mucosa Submucosa: containing mucus secreting glands and submucosal nerve plexus Muscularis externa: Circular muscle Longitudinal muscle Adventitia

Question 28

Describe the structure of the lower oesophageal sphincter

Answer 28

The lower oesophageal sphincter is a physiological sphincter that prevents reflux of acidic gastric contents back into the oesophagus. There is no thickening of circular muscle, mucosal folds act as a physiological valve which can be closed by circular muscle. Sphincter is formed by the angle of the cardia of the stomach (gastrooesophageal angle). Mucosal folds at gastro-oesophageal junction, compression by the right crux of the diaphragm and intra-abdominal pressure.

Question 29

Describe the oral phase of swallowing (5 points)

Answer 29

Voluntary phase (1s) Respiration inhibited Bolus formed on the tongue hyoid bone, floor of the mouth and tongue move superoposteriorly Soft palate elevates and closes nasopharynx Bolus propelled into the oropharynx

Question 30

Describe the Pharyngeal phase of swallowing

Answer 30

Involuntary (1 sec) Glottis closes Larynx elevates Epiglottis folds posteroinferiorly Cricopharyngeus relaxes Peristaltic wave propels bolus of food into oesophagus

Question 31

Describe the oesophageal phase of swallowing

Answer 31

Involuntary (10 secs) Cricopharyngeus regains tone and palate relaxes. Larynx falls, glottis opens and respiration recommences. Peristaltic wave moves oesophagus to stomach. Secondary and tertiary waves may occur to clear residue.

Question 32

State the venuous drainage of the oesophagus Why is this clinically significant?

Answer 32

The blood supply of the oesophagus is segmented. Upper third (cervical part) drains to the inferior thyroid veins Middle third (thoracic part) drains into the azygous and hemiazygous veins Lower third (abdominal part) drains to the left gastric vein In cases of oesophageal cancer, can affect where cancer presents and also give an indication of what sites the cancer may have metastasised to.

Question 33

Describe the arterial supply to the oesophagus

Answer 33

Arterial supply of the esophagus is segmental The branches of the inferior thyroid artery provide arterial blood supply to the upper third of the oesophagus The paired aortic esophageal arteries or terminal branches of bronchial arteries supply the thoracic esophagus. The left gastric artery and a branch of the left phrenic artery supply the LES and the most distal segment of the esophagus. The arteries supplying the esophagus end in an extensive, dense network in the submucosa.

Question 34

How is the transition from oesophageal to gastric mucosa identified?

Answer 34

Z-line Change from squamous to columnar epithelium at the gastro-oesophageal junction creates a zig-zag 'Z-line'

Question 35

Describe the location and function of the submandibular gland

Answer 35

Lies along the body of the mandible. Duct arises from between mylohyoid and hyoglossus. Submandibular duct and opens into Lingual nerve passes into the floor of the mouth. Carries touch and temperature sensation from anterior 2/3 of tongue, close to 3rd molar tooth. Parasympathetic supply from chorda tympani lie in submandibular ganglion. (travels via lingual nerve) Controls salivation.

Question 36

Parotid gland

Answer 36

Largest salivary gland. Lies between the ramus of the mandible and the styloid and mastoid process of the temporal bone. Anterior to external acoustic meatus. Enclosed in investing fascia of the neck. Parotid duct passes from lower tragus to lateral corner of the mouth. Pierces buccinator to enter into the vestibule of the oral cavity opposite the 2nd molar tooth. Arterial supply for external carotid and superficial temporal arteries. Veins drain to retromandibular veins. Lymphatics drain to superficial and deep cervical nodes.

Question 37

Infection of the parotid gland

Answer 37

Infection of the gland causes inflammation parotitis Severe pain occurs because the sheath limits swelling. Pain often worse during chewing because enlarged gland is wrapped around the ramus of the mandible. Parotid papilla become red. Tooth pain. Can cause pain in auricle, external acoustic meatus, temporal region and TMJ because auriculotemporal nerve (Branch of CN V3) also supplies these regions.

Question 38

Paralysis of genioglossus

Answer 38

Genioglossus is responsible for protrusion of the tonue. When muscle is paralysed, the tongue mass shifts posteriorly, obstructing the airway and presenting the risk of suffocation. Important in anaesthesia

Question 39

Innervation of the mandibular teeth

Answer 39