2- Oesophagus Flashcards
Describe adult teeth
Adult humans have 32 teeth in total.
8 incisors
4 canines
8 premolars
12 molars
What is the muscle in the jaw responsible for biting action
Massater
2 enzymes in saliva
lingual lipase and salivary amylase,
What are the 2 types of tongue muscle
Intrinsic muscles - responsible for fine motor control of the tongue, such as enunciating specific sounds, or for moving food from one part of the mouth to another.
Extrinsic muscles - responsible 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.
How is food stopped from going into the airways
This is achieved by the epiglottis and the upper oesophageal sphincter. At rest, the oesophageal sphincter is tonically active and the epiglottis is in the upright position.
What 2 muscles make up the upper oesophageal sphincter
Constrictor pharyngeal medius - which has commonality with the circular muscle layer of the GI tract
Constrictor pharynges inferior - which has commonality with the longitudinal muscle layer
What is the muscle composition of the oesophagus
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.
How long is the oesophagus
25cm
What are the 2 components of the lower oesophageal sphincter
The internal component - which is built into the circular smooth muscle of the oesophageal wall
The external component - which is formed by the right crus of the diaphragm (voluntary control)
Describe the epithelium in the oesophagus
The epithelial lining of the oesophagus is an arrangement of non-keratinised stratified squamous cells, which forms a robust wear-and-tear lining
At the lower oesophageal sphincter, where the epithelial cells are arranged as simple columnar epithelia. This is to address the different conditions these epithelia need to tolerate (i.e. resistance against strong stomach acid).
This epithelial change occurs within the sphincter along a jagged line called the z-line.
4 phases of swallowing
Stage 0: The oral phase. Chewing and saliva help to prepare the bolus for swallowing. Both oesophageal sphincters are constricted.
Stage 1: 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.
Stage 2: 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.
Stage 3: Lower oesophageal phase. As food passes through the lower sphincter that too closes, and the peristaltic wave continues to push food into the stomach.
