GI PBL 1 Flashcards
What makes up the upper GI tract?
The oesophagus, the stomach and the duodenum
How long is the oesophagus?
Roughly 25cm
What is the function of the oesophagus?
To transport food from the pharynx to the stomach
Where does the oesophagus originate?
The inferior border of the cricoid cartilage (C6)
Where does the oesophagus finish?
The stomach at the level T11
What is the oesophagus made up of?
The adventitia, muscular layer, submucosa and mucosa
What is the adventitia?
The outer layer of connective tissue
What is the muscular layer?
An external layer of longitudinal muscle and an internal layer of circular muscle
What types of muscle make up the outer layer of muscle?
Superior third: Voluntary striated muscle
Middle third: voluntary striated and smooth muscle
Inferior third: smooth muscle
What is the mucosa?
Non-keratinised stratified squamous epithelium
What type of epithelium line the stomach?
Columnar epithelium
How is food transported through the oesophagus?
peristalsis
What is peristalsis?
Rhythmic contractions of the muscle which moves food down the oesophagus
What are the oesophageal sphincters?
Upper and Lower oesophageal sphincters
What is the function of the oesophageal sphincters?
They help to prevent the entry of air and the reflux of gastric contents
What type of sphincter is the UOS?
A striated muscle sphincter
Where is the UOS?
The junction between the pharynx and the oesophagus
What muscle produces the UOS?
The cricopharyngeal muscle
Is the UOS usually constricted or relaxed?
Constricted to prevent the entrance of air into the oesophagus
What type of sphincter is the LOS?
A physiological sphincter - it doesn’t have a specific sphincter muscle
Where is the LOS located?
The gastro-oesophageal junction (between the stomach and the oesophagus situated to the left of the T11 vertebra)
How is the LOS formed?
- The oesophagus enters the stomach at an acute angle
- The walls of the intra-abdominal section of the oesophagus are compressed when there is a positive intra-abdominal pressure
- The folds of mucosa present aid in occluding the lumen at the gastro-oesophageal junction.
- The right crus of the diaphragm has a pinch-cock effect
When is the LOS relaxed?
During peristalsis to allow food to enter the stomach
What supplies blood to the thoracic portion of the oesophagus?
branches of the thoracic aorta and the inferior thyroid artery
What is the venous drainage of the oesophagus?
branches of the azygous veins and the inferior thyroid vein
What supplies blood to the abdominal portion of the oesophagus?
Left gastric artery (branch of the coeliac trunk) and left interior phrenic artery
What is the venous drainage of the abdominal portion of the oesophagus?
- portal circulation via the left gastric vein
- systemic circulation via the azygous vein
What is the innervation of the oesophagus?
- the oesophageal plexus combination of parasympathetic and sympathetic nerve fibres
What are the four main divisions of the stomach?
cardia, fundus, body, pylorus
What is the cardia?
The area that surrounds the superior opening of the stomach at the T11 level
What is the fundus?
The rounded often gas filled portion superior to and left of the cardia
What is the body of the stomach?
The large central portion inferior to the fundus
What is the pylorus of the stomach?
the area that connects the stomach to the duodenum
What is the pylorus divided into?
The pyloric antrum and the pyloric sphincter
What is the stomach wall composed of?
Serosa, muscularis, submucosa and mucosa
What are the layers of the muscularis
Oblique, circular and longitudinal
What is the function of the muscularis
The layers of muscle contract rhythmically to break up food in the stomach
What is the submucosa made up of?
Made up of connective tissue and a vascular plexus
What is the function of the submucosa
Allows the mucosa to move freely over the deeper structures
What is the mucosa?
the deepest layer of the stomach made up of three layers
What are the three layers of the stomach mucosa?
Epithelium, lamina propria, muscularis mucosae
Why is the internal surface of the stomach folded?
To form millions of gastric pits
What is the lamina propria?
Loose connective tissue that lies between the muscularis mucosae and the outer layer
What does the lamina propria of the stomach contain?
Capillaries, lymphatic vessels and nerves and gastric glands
What is the muscularis mucosae of the stomach?
A thin layer of smooth muscle that lies between the lamina propria and submucosa
What is the function of the muscularis mucosae in the stomach?
when it contracts, it compresses the gastric glands and helps to push their contents into the stomach
Where does the greater omentum hang from?
The greater curvature of the stomach
What is the function of the greater omentum?
Has many lymph nodes and can adhere to inflamed areas so helps minimise the spread of infections
Where is the lesser omentum found?
It is continuous with the peritneal layers of the stomach, it attaches to the liver
What is the function of the lesser omentum?
To attach the stomach and duodenum to the liver