DS: Pharynx And Oesophagus

Question 1

What is the pharynx?

Answer 1

Common passageway for foods, liquids and air. Transports boluses from the oral cavity to the oesophagus.

Question 2

What are the 3 distinct regions of the pharynx?

Answer 2

1. Nasopharynx
2. Oropharynx
3. Laryngopharynx

Question 3

What is the role of the nasopharynx in the digestive system?

Answer 3

The nasopharynx plays no part in the digestive system and is mainly involved in the respiratory system and the movement of air through the oral cavity to the lungs.

Question 4

What are the roles of the oropharynx and laryngopharynx in the digestive system?

Answer 4

Involved in food transportation from the oral cavity to the oesophagus, and eventually the stomach.

Question 5

Describe the structure of the oropharynx and laryngopharynx

Answer 5

Lined by stratified squamous epithelium and the lamina propria has a rich supply of mucous-secreting glands to lubricate the pharynx and aid in the movement of food boluses. The external musculature has 3 layers of skeletal muscle (pharyngeal constrictor muscles) that aid in deglutition.

Question 6

What is degluition?

Answer 6

Swallowing

Question 7

What is mastication?

Answer 7

Chewing

Question 8

What are the 3 layers of skeletal muscle (pharyngeal constrictor muscles) found in the pharynx?

Answer 8

1. Superior pharyngeal constrictor
2. Middle pharyngeal constrictor
3. Inferior pharyngeal constrictor

Question 9

Briefly describe the process of deglutition

Answer 9

Deglutition is initiated involuntarily but then proceeds automatically once the food bolus reaches the back of the oral cavity, near the oropharynx.

Question 10

What muscles assist the pharyngeal constrictor muscles during deglutition?

Answer 10

Tensor veil palatini and legatos veil palatini

Question 11

What is the general role of the veil palatini muscles in deglutition?

Answer 11

Temporarily block off the nasopharynx to prevent entry of food into the nasal cavity and respiratory tract

Question 12

Describe the action of the veil palatini muscles during deglutition

Answer 12

The tensor veli palatini tenses the soft palate and by doing so, assists the levator veli palatini in elevating the palate to occlude and prevent entry of food into the nasopharynx during swallowing. The tensed palate consequently provides a stable platform for elevation of the pharynx during swallowing by the pharyngeal muscles.

Question 13

What are the 2 phases of deglutition?

Answer 13

1. Voluntary (Buccal) phase

2. Involuntary phase

Question 14

Describe the voluntary phase of deglutition

Answer 14

Food boluses propelled towards the oropharynx which stimulates mechanoreceptors on the uvula, palatoglossal arch, palatopharyngeal arch, and the posterior pharyngeal wall.

Stimulation of the mechanoreceptors activates sensory afferent neurons in cranial nerve IX (9). Action potentials (APs) are sent from the cranial sensory neurons to the swallowing centre in the nucleus tractus solitarius (NTS) located in the medulla and lower pons. The sensory input is processed in the NTS and a response is coordinated.

The NTS activates adjacent motor nucleus ambiguus (NA) which sends APs via cranial nerves IX (9) and X (10), to the skeletal muscles involved in deglutition, to carry out the command of the NTS.

Question 15

When does the voluntary phase of deglutition begin and end?

Answer 15

Begins with the ingestion of food. Ends shortly after the tongue compresses a food bolus against the hard palate, retracts and propels the bolus towards the oropharynx; involuntary process from then on.

Question 16

What is the NTS?

Answer 16

Nucleus Tractus Solitarius

Question 17

What is the role of the NTS in deglutition?

Answer 17

Receives input from the environment with regards to the presence of a food bolus in the pharynx, and coordinates a response in order to facilitate deglutition.

Question 18

What is the NA?

Answer 18

Nucleus Ambiguous

Question 19

What is the role of the NS?

Answer 19

Carry out the commands of the NTS by sending out APs via cranial nerves, to carry out the process of deglutition

Question 20

Describe the involuntary phase of deglutition

Answer 20

Respiratory centres in the CNS are inhibited to stop breathing momentarily; elevation of the soft palate and uvula closes the nasopharynx to prevent the movement of air into the stomach, and to prevent food entering the nasal cavity.

The larynx is raised and the epiglottis folds over the opening in the larynx to the respiratory tract.

Food moves through the pharynx, towards the oesophagus, via constrictions of the pharyngeal constrictor muscles.

The upper oesophageal sphincter is released to allow movement of the food from the pharynx to the oesophagus.

Question 21

What initiates the involuntary phase of deglutition?

Answer 21

Contractions of the superior pharyngeal constrictor muscle

Question 22

What is the UOS and what is its function?

Answer 22

Upper Oesophageal Sphincter; facilitates and regulates the movement of the food bolus from the pharynx to the oesophagus.

Question 23

How does the food bolus move through the oesophagus?

Answer 23

The bolus moves through the oesophagus via persistalsis, distension of the oesophageal wall due to approaching food bolus near the stomach.

Question 24

What is the LOS and what is its function?

Answer 24

Lower Oesophageal Sphincter; facilitates and regulates the movement of the food bolus into the stomach, and helps prevent against stomach acid reflux.

Question 25

Describe the difference in the epithelial as the junction between the oesophagus and the stomach

Answer 25

The epithelia changes from stratified squamous epithelium to simple columnar epithelium

Question 26

What is dysphagia?

Answer 26

Dysphagia is a common complication of neurological disorders such as amyotrophic lateral sclerosis (ASL). ALS is caharacterised by the selective death of motor neurons (MNs) in the brain cortex, brain stem (NA) and the somatic nervous system.

Question 27

What are the 2 forms of peristalsis that are used to propel food through the oesophagus?

Answer 27

1. Primary peristalsis

2. Secondary peristalsis

Question 28

How do primary and secondary peristalsis differ?

Answer 28

Primary peristaltic waves begin from the superior pharyngeal constrictor muscles, where as secondary peristaltic waves are in response to food getting stuck in the oesophagus following primary peristalsis or acid reflux content from the stomach.

Question 29

What is the oesophagus?

Answer 29

The oesophagus is a muscular tube that extends from the laryngopharynx to the stomach, and is specialised for the transport of food and liquids from the upper digestive tract to the stomach.

Question 30

Describe the gut wall of the oesophagus

Answer 30

Stratified squamous epithelium which is protective and resists mechanical abrasion from food boluses.

The mucosa and submucosa of the empty oesophagus form longitudinal folds that flatten out when food is present. The submucosa contains mucous-producing oesophageal glands that lubricate the oesophagus and aid in the movement of the food boluses. More glands near the stomach to protect tissue against against acid reflux from the stomach.