Gastro - Upper GI Tract

Question 1

What is the main function of the GI system?

Answer 1

Digest the food and break it down into macromolecules, which are then absorbed.

Question 2

Describe two methods of food absorption

Answer 2

They can be absorbed into the blood stream or directly into the lymphatic system

Question 3

Describe the structures of the upper GI tract and its development

Answer 3

The oesophagus and stomach as they arise from the fore gut and the other fore gut structures are the liver, the pancreas, the gall bladder and a portion of the billary system.

Question 4

Describe the structures of the mid GI tract and its development

Answer 4

The mid gastrointestinal tract arises from the midgut and consists of all the small intestine and a portion of the large intestine as well, including a portion of the transverse colon

Question 5

Describe the structures of the lower GI tract and its development

Answer 5

The hind gut gives rise to the lower gastrointestinal tract, this consists of the entire colon, the rectum and the anus.

Question 6

Describe the overall histology of the GI tract

Answer 6

Mucosa, sub mucosa and a muscularis layer, there will be possibly a series of an adventitious layer as well.

Question 7

The mucosa consists of

Answer 7

The mucosa consists of epithelium and it consists of muscularis mucosa

Question 8

What does the submucosa consist of

Answer 8

In addition to some loose connective tissue that’s called lamina propria, sub mucosa consists mainly of connective tissue with the nerve plexus, which are important for peristalsis and various other functions of the gastrointestinal tract.

Question 9

What does the muscularis layer consist of

Answer 9

The muscularis layer is further divided into two types of muscle, inner the circular muscle layers and the outer longditudinal layers

Question 10

Describe the contents of the oral cavity

Answer 10

There are 32 teeth in total, 8 incisors, 4 canines, 8 premolars and 12 molars two major muscles in chewing, masseter and temporalis and parotid, submaxillary and sublingual glands secreting amylase and lipase

Question 11

What is the function of the tongue

Answer 11

The tongue is an extremely muscular organ, and it has the function of moving the food around the mouth and mixing it with saliva In order for the food to be lubricated so it can then be pushed into the pharynx,

Question 12

What is the oesophagus and how can it be divided

Answer 12

The oesophagus is a very strong muscular tube which propagates the food bolus from the pharynx into the stomach oesophagus is likely can be seen as two anatomical parts or can be classified anatomically in two ways

Question 13

Describe the ways of oesophageal division

Answer 13

the first way is you divide the oesophagus into the parts of the body cavity that it runs through. So there’s a cervical part consisting of a few cm in the neck, the predominant thoracic and the abdominal oesophagus consisting of a few cm in the abdomen

during endoscopy the oesophagus can be divided with the measurement is started from the incisors. The upper one third of the oesophagus is up to 24 centimetres, which is usually at the level of the KORINA. The middle third is 24-32 cm from the incisors. And the lower oesophagus is 32-40 cm from incisors

Question 14

describe the major histological features of the cells of the Oesphagus and why this is important

Answer 14

The oesophageal epithelium is non keratinising squamous epithelium. This is extremely important because it prevents against the wear and tear and from acid reflux which can cause significant damage to the oesophagus
The oesophagus also consists of mucus secreting gland which can lubricate the food bolus as it passes through the oesophagus

Question 15

what are the sphincters and the Z line

Answer 15

The oesophagus has two sphincters the upper true and the controversial lower oesophageal sphincter the anatomy of the low oesophagus is quite unique. There is a line called the Z line, and this is an important feature because this is where the pale pink mucosa of the squamous epithelium meets the red mucosa of the gastric epithelium.

Question 16

Describe barrets oesophagus

Answer 16

the epithelium of the lower oesophagus undergoes a change that’s known as metaplasia. When that happens, you get gastric mucosa and extending into the oesophagus.

Question 17

Describe the two muscularis layers

Answer 17

the inner circular muscular muscle, and outer longitudinal. The circular muscle layer has a segmental rule, so it allows the soft the food to remain the oesophagus in certain segments for some time. And the longitudinal layer pushes the bolus and propagates it caudally or distally and allows that food bolus to move downwards.

Question 18

Describe the cancerous findings of the oesophagus

Answer 18

About three or four decades ago were mainly squamous cell cancers arising from the squamous epithelium of the oesophagus. But now we increasingly see adenocarcinomas arising from metaplastic epithelium of the gastroesophageal junction.

Question 19

How does cancerous change occur?

Answer 19

The theory for it is that prolonged acid exposure causes inflammation of the lower oesophagus that prolong acid damage, causes the squamous epithelium to change and become columnar epithelium, which is protective against the acid damage and that persistent metaplasia. The change the epithelium then makes these cells unstable, which causes high dysplasia, and then this dyplastic epithelium then becomes cancerous.

Question 20

How can the diaphragm protect against reflux

Answer 20

the diaphragm itself pinches the lower sphincter and prevents acid reflux

Question 21

Describe a hernia observed as a consequence of the diaphragm

Answer 21

In a hiatus hernia, this opening of the diaphragm becomes larger, the portion of the stomach slips into the chest and, causes prolonged exposure of the lower oesophagus to the acid,.

Question 22

Give an anatomic reason as to how reflux is protected against

Answer 22

The other ways by which this acid reflux is prevented is the anatomical position of the gastroesophageal junction in relation to the stomach lies at an angle, because of that angle, acid reflux is prevented. There are other ligaments that suspend the gastroesophageal junction at an acute angle on the pharyngoesophageal ligaments, and these prevent acid reflux as well.

Question 23

Why are there folds?

Answer 23

The reason as to why the stomach has numerous folds is just to increase the surface area of the epithelium of the gastro intestinal tract so that the more amount of digestion and more amount of absorption can occur In the gastrointestinal tract.

Question 24

What is swallowing and what are its phases

Answer 24

Swallowing is a coordinated peristaltic movement that’s extends down from the pharynx through the oesophagus into the stomach to push the food bolus down in a painless and well coordinated manner. Consisting of an oral phase, pharyngeal phase and upper and lower oesophageal phases

Question 25

What is the function of the stomach

Answer 25

The stomach breaks down food into smaller particles through the secretion of acid and a protein called pepsin. It pulls the food down and keeps the food in the stomach so that the digestion can occur efficiently and properly. And because of it’s so high acid content, it can also kill bacteria and parasites and prevent them from going down the gastro intestinal tract and causing various diseases.

Question 26

Describe the anatomical regions of the stomach

Answer 26

The stomach can be divided anatomically into various sections. The part that is just below the gastroesophageal junction is called the Cardium. A large bulbous bit at the tip of the stomach is called a fundus. The majority of the stomach is known as the body of the stomach. There is the distal stomach that’s called the antrum. And then there is a very small outlet that’s called the Pyloric Canal and a sphincter.

Question 27

What does the stomach secrete

Answer 27

The stomach secretes mucus , acid, and a protein called pepsin, which is activated by HCL secretion cleaved from pepsinogen.

Question 28

How is stomach epithelia not damaged by low ph

Answer 28

Ph of stomach is low at 1-2 where the epithelium would be completely destroyed, but a mucus layer coats the epithelium and prevents that acid from eroding the epithelium itself.

Question 29

Describe the role of the circular muscle layer

Answer 29

The circular muscle layer is largely responsible for segmentation, where the stomach or even the small bowel retain its contents for a longer period of time Within a certain segment between two parts which are contracting.

Question 30

Describe the role of the longitudinal muscle layer

Answer 30

the longitudinal muscle layer is the one that actually moves the content of gastro intestinal tract along to from one part to another part.

Question 31

Function of chief cell

Answer 31

The chief cell is the protein secreting cell, which secretes Pepsinogen cleaved by HCL to pepsin, just like any other protein secreting cell It’s got abundant endoplasmic reticulum and Golgi apparatus,, these are the intracellular structures that are largely involved in protein synthesis and protein secretion.

Question 32

Functions of parietal cell and cellular character

Answer 32

In order to undertake its function of secreting hydrochloric acid requires a lot of ATP. And that’s why this particular cell is rich in mitochondria. There is a pump called a hydrogen Potassium ATPase which is a pump that’s largely responsible for secretion of the hydrochloric acid into the lumen of the stomach.

Question 33

How is HCL secreted

Answer 33

The hydrochloric acid is secreted into tubular vesicles which, then fuse with the membrane of the cell and then secrete the hydrochloric acid into the lumen of the stomach

Question 34

Describe the use of the NaK pump in HCL secretion

Answer 34

There is a sodium potassium pump that brings in potassium into the parietal cell and secretes out sodium. This potassium is important because this potassium is part of the hydrogen potassium ATPase which then secretes the hydrochloric acid. So as the potassium leaves the cell, as potassium gets reabsorbed from the lumen, the hydrogen leaves the cell.

Question 35

How is HCL secreted

Answer 35

Hydrogen comes from breakdown of H2CO3 into carbonic acid and bicarbonate by carbonic anhydrase. These hydrogen ions are the ones that go into the hydrogen potassium ATPase pump and get secreted into the gastric lumen. The potassium, in addition, which is being exchanged back into the cell combines with chloride ions and get secreted back into the lumen. The stomach thus secretes a fluid rich in hydrochloric acid as well as potassium.

Question 36

Where does Co2 come from

Answer 36

Carbon dioxide comes from the capillaries and mixes with water to form the hydrogen ions and bicarbonate.

Question 37

what would happen if you blocked the effect of carbonic anhydrase

Answer 37

if you blocked the effect of carbonic anhydrase, then you would not have any hydrogen ions because they would not then combined with the CO to form the bicarbonate ions and hydrogen ions

Question 38

how does the whole process of hydrochloric acid secretion start

Answer 38

The hydrochloric acid secretion is stimulated from H histamine receptors. These histamine receptors are found on the surface of the parietal cell. So when histamine gets released from different triggers, that histamine then gets activated with the receptor that lies in the cell.

Question 39

Describe the other major hormone in Gastric acid secretion

Answer 39

gastrin is secreted by the G cells. And these are found mainly in the antrum, the G cells. just like histamine thr gastrin is another stimulator of HCL. Causes the parietal cells to secrete hydrochloric acid

Question 40

Describe the first phase of gastric secretion

Answer 40

The cephalic phase where the mere sight or smell of food causes a gaseous secretion, and these stimuli come via vagus nerves, and the vagus nerve then stimulates the parietal cell through acetylcholine and acetylcholine, then activates the whole mechanism of the formation or HCL also stimulated by H and G

Question 41

Describe the second phase of gastric secretion

Answer 41

gastric phase food comes into the stomach and there are stretch receptors and chemo receptors, which causes the secretion of acid. The signal goes to the brain. From there, it comes back via the vagus nerves, just like it did in the cephalic phase and that causes secretion of hydrochloric acid.

Question 42

Describe the third phase of gastric secretion

Answer 42

There is a further intestinal phase when the food reaches the duodenum two things happen in intestinal phase. There is an inhibitory inhibition of gastric acid, but also the stimulation of gastric acid. The main function is that when the food or chyme with the presence of lipids reaches into the intestine, the signal comes via the vagus nerves, and that causes an inhibition of the secretion of gastric hydrochloric acid and pepsin, too. And this is through different inhibitory hormones and peptides, gastric inhibitory peptide, cholestyramine and secretin . And this is the way in which gastric secretion is suppressed when partially digested food enters the gut

Question 43

Treatment for ulcer disease

Answer 43

Surgery for ulcer disease is something that is hardly ever practised in modern upper gastro intestinal surgery because Two types of drugs that have been developed. One of them is histamine receptor blockers, which block the histamine receptor. And these are rimetidine and cimetidine. They block the gastrin receptor and they prevent acid secretion. And more importantly and recently, the proton pump inhibitors, the hydrogen potassium, ATPase, pump inhibitors that prevent acid formation. And these medications are completely revolutionise the treatment of ulcer disease And they are the mainstay of treatment for acid reflux as well