Oesophagus Flashcards
What is the oral cavity bound by anatomically?
Teeth to the front and the sides, the tongue to the bottom and the hard and soft palates to the top and the oropharynx to the rear
What is the massater muscle? What does it do and where is it found
Largest jaw muscle, responsible for biting action an lateral to the molars
What digestive enzymes are found in the mouth?
Linguinal lipase and salivary amylase - first stage of fat and carb digestion respectively
What are the two categories of muscles found in the tongue
Intrinsic and extrinsic
What are intrinsic tongue muscles for?
fine motor control of the tongue, such as enunciating specific sounds, or for moving food from one part of the mouth to another
What are extrinsic tongue muscles for?
gross movements of the tongue, such as in, out, up and down. This is especially useful to assist mechanical digestion, by pounding the food bolus against the hard palate at the roof of the mouth
What are the key functions of the tongue?
speech, eating and taste (salt, sweet, bitter, sour, umami)
What positions are the oesophageal sphincter and the epiglottis at at rest?
upper oesophageal sphincter. At rest, the oesophageal sphincter is tonically active and the epiglottis is in the upright position
What happens to theoesophageal sphincter and the epiglottis during swallowing?
epiglottis coming down to cover the entrance to the trachea as the bolus of food moves through the pharynx, and the upper oesophageal sphincter relaxes allowing it to flow into the oesophagus
What is the oesophagus?
conduit tube connecting the oral cavity and the stomach
Where does the oesophagus pass through
the thorax places it in close proximity to key structures such as the heart, lungs and major blood vessels
What are the two muscles that the upper oesophageal sphincter is made up of?
Constrictor pharynges medius and constrictor pharynges inferior
What does the constrictor pharyngeal medius have a commonality with
circular muscle layer of the GI tract
What does the constrictor pharyngeal inferior have a commonality with
longitudinal muscle layer
How long approx is the eoesophgus in a typical adult male?
25cm
What muscles are the different parts of the oesophgus made out of
the upper oesophagus is composed of skeletal muscle only, and the lower oesophagus is smooth muscle only. The middle third is a mixture of the two as the proportion of skeletal muscle tapers along its length
What two parts are the lower oesophageal sphincter made out of?
Internal and external component
What is the internal component built into?
circular smooth muscle of the oesophageal wall
What is the external component formed by?
the right crus of the diaphragm (voluntary control)
What kind of pressure is the oesophagus and the stomach usually under
oesophagus is under negative pressure most of the time, whereas the stomach is under positive pressure.
What epithelium makes up the lining of the oesophagus
non-keratinised stratified squamous cells
What quality does the epithelia of the oesophagus need to have
robust wear-and-tear lining to protect the oesophagus from a variety of ingested foods, ranging from smooth to abrasive, hot, cold and acidic
What kind of epithelial cells are found in the lower oesophageal sphincter?
Simple columnar epithelia bc different conditions - resist stomach acid
How does the epithelial cell change in the oesophagus happen?
Within the sphincter along a jagged line called the z line
What are the 4 stages of swallowing
Stage 0 - oral phase
Stage 1 - pharyngeal phase
Stage 2 - Upper oesophageal phase
Stage 3 - Lower oesophageal phase
What happens in the oral phase?
Chewing and saliva help to prepare the bolus for swallowing. Both oesophageal sphincters are constricted.
What happens in the pharyngeal phase?
As the food bolus moves to the back of the pharynx the pharyngeal musculature helps to guide it towards the oesophagus. Both oesophageal sphincters open.
What happens in the upper oesophageal phase?
The upper sphincter closes, and superior rings of circular muscle contract as inferior rings dilate. Sequential contractions of longitudinal muscle help guide the food down the gullet.
What happens in the lower oesophageal phase
As food passes through the lower sphincter that too closes, and the peristaltic wave continues to push food into the stomach.
