2 Oesophagus Flashcards
XQ: Which muscle is responsible for the biting action? (closing of jaw)
A: massater muscle- largest jaw muscle
XQ: What happens to the small bits of food after the teeth have cut them up? Enzymes? (2) What’s created? What happens to it?
A: Small pieces of food are mixed with saliva, an aqueous secretion with digestive enzymes. Specifically, lingual lipase and salivary amylase, which for the first stage of fat and carbohydrate digestion respectively.
The mixing of food and saliva creates a bolus that can be swallowed into the stomach once it is the right size and consistency.
XQ: What are the 2 types of tongue muscle?
A: 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
Q: The oral cavity leads to two different places (the lungs and the stomach). How do you ensure we get food to the correct destination? (2) Other end? Describe these structures. What happens during swallowing? Control?
A: epiglottis and the upper oesophageal sphincter
lower oesophageal sphincter
both are tonically active at rest (epiglottis is in the upright position) -> closed
the 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
have a swallowing centre in medulla which initiates swallowing and allows relaxation of upper sph. -> have stretch receptors that react to bolus = involuntary enteric NS
Q: What is the role of the oesophagus? Where is it? Beginning? End?
A: connects pharynx and stomach= conduit for food, drink and swallowed secretions
-most resides in thorax and small part in abdomen
C5, T10
Q: Describe the oesophagus epithelium. (3) Suited to? Covered in? Contains?
A: -non keratinising stratified squamous
- suited to wear and tear function (extreme temp and texture)
- lubricated by mucous secreting glands and saliva
glands project through it
Q: Which type of muscle makes the oesophagus? Function? Controlled by? How does muscle type change as you go down the oesophagus?
A: circular smooth (outside is longitudinal)
- peristalsis (movement that allows food to move down): part before bolus contracts and part just after relaxes -> (if not all food is taken in one go, get second wave of peristalsis)
- enteric nervous system
the upper oesophagus is composed of skeletal muscle only (under voluntary control), 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.
Q: What is the oesophagus in close proximity to? (3) How is it placed within the body?
A: in close proximity to key structures such as the heart, lungs and major blood vessels
at first is behind trachea then in front of aorta then part that connects it to stomach is in abdomen
Q: What makes the upper oesophageal sphincter? (2) Commonality with? Lower? (2) Control?
A: 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
made of diaphragm and curvature of stomach
- 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)
Q: How does the stomach and oesophagus vary in terms of pressure?
A: oesophagus is under negative pressure most of the time, whereas the stomach is under positive pressure.
Q: What structure is present where the stomach and oesophagus meet? role? Describe it.
A: gastro-oesophageal junction- prevent reflux (via diaphragm)
zigzag pattern showing clear separation- epithelial transition: from stratified to simple columnar
Q: What are the stages of swallowing? (4) Describe.
A: 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.
