Oesophagus

Question 1

How many incisors, canines, premolars and molars do adult humans have?

Answer 1

8 I, 4 C, 8 PM, 12 M

Question 2

What is the massater muscle?

Answer 2

Largest jaw muscle responsible for biting action.

Question 3

What are the digestive enzymes present in saliva?

Answer 3

Lingual lipase and salivary amylase.

Question 4

What does mixing of food and saliva create?

Answer 4

A bolus that can be swallowed into the stomach when right size and consistency

Question 5

The tongue is formed of 2 classified types of muscle. Describe them.

Answer 5

Intrinsic muscles - responsible for fine motor control.

Extrinsic muscles - responsible for gross motor control (particularly useful in mechanical digestion - pushes bolus against hard roof palate).

Question 6

How do we ensure food goes down the right hole?

Answer 6

Rest - oesophageal sphincter is tonically active and epiglottis is in upright position (oesophagus mostly collapsed at rest).

Swallowing - epiglottis covers entrance of trachea (bolus moves through pharynx). Upper oesophageal sphincter relaxes - allows bolus to flow into oesophagus

Question 7

Which 2 muscles compose the upper oesophageal sphincter?

Answer 7

1. Constrictor pharyngeal medius - commonality with GI tract circular muscle layer
2. Constrictor pharynges inferior - commonality with longitudinal muscle layer

Question 8

Upper 1/3, middle 1/3, lower 1/3 of oesophagus. How do they vary?

Answer 8

Skeletal -> skeletal and smooth muscle -> smooth muscle

Question 9

How long is the oesophagus roughly?

Answer 9

25cm

Question 10

Is the oesophagus under voluntary control, despite the presence of skeletal muscle?

Answer 10

NO

Question 11

Which 2 portions compose the lower oesophageal sphincter?

Answer 11

1. Internal component - built into circular smooth muscle of oesophageal wall
2. External component - formed by right crus of the diaphragm

Question 12

Oesophagus is under what pressure most of the time? What about the stomach?

Answer 12

Oesophagus = negative

Stomach - positive

Question 13

Describe the epithelial lining of the oesophagus.

Answer 13

Non-keratinised stratified squamous cells from upper to lower oesophageal sphincter.

At lower oesophageal sphincter, epithelial cells are simple columnar epithelia.

CHANGE OCCURS AT Z-LINE

Question 14

Why does the lower oesophageal sphincter become simple columnar?

Answer 14

To cope with different conditions (e.g. resistance to strong stomach acid).

Question 15

What are the stages of swallowing?

Answer 15

Stage 0 = oral phase. Chewing/saliva help prepare bolus for swallowing. Both oesophageal sphincters are constricted.

Stage 1 = Pharyngeal phase. Food bolus moves to back of pharynx - pharyngeal musculature helps guide it towards the oesophagus. Both oesophageal sphincters are open.

Stage 2 = Upper oesophageal phase. Upper sphincter closes, superior circular muscle rings contract and inferior rings dilate. Sequential contractions of longitudinal muscle guide food down the gullet.

Stage 3 = Lower sphincter also closes. Peristaltic wave continues to push food into stomach.

Question 16

The oesophageal phase is controlled centrally.

Answer 16

T.

Question 17

What is the lower sphincter composed of?

Answer 17

Local smooth muscle and skeletal muscle of the diaphragm

Question 18

Where does the myenteric plexus lie?

Answer 18

Superficial to circular smooth muscle layer

Deep to longitudinal muscle layer