Microanatomy of the GI tract 2

Question 1

epithelium type of oesophagus

Answer 1

Stratified squamous because its protective epithelium

Question 2

What’s the muscular layer like of the oesophagus (how does it change)

Answer 2

1st third: skeletal (voluntary)
Middle third: mixed
Last third: smooth (involuntary)

Question 3

Outer layer of oesophagus in thorax vs abdomen

Answer 3

Adventitia in thorax

Becomes serosa in last part beyond diaphragm (which allows it to secrete water to reduce friction)

Question 4

What is Barrats oesophagus and why does it occur

Answer 4

Metaplasia. Change from stratified to columnar in oesophagus due to repeated damage from gastric reflux

–> Happens because columnar epithelium is more likely to protect against acid in oesophagus

Question 5

What are rugae

Answer 5

Folds which increase the surface area and enable max contact between stomach contents and gastric mucosa

Question 6

What is the luminal surface of the stomach composed entirely of

Answer 6

Columnar epithelial mucous cells for protection

Question 7

What do gastric pits contain

Answer 7

Epithelial cell types which break down food

Question 8

What is the oblique muscle layer of the stomach used for

Answer 8

Facilitates the churning of the food in all directions

Question 9

What cells are there in gastric pits

Answer 9

Mucous cells
Parietal cells
chief cells
Enteroendocrine cells

Question 10

Where are and What do mucous cells produce

Answer 10

At the surface

-Produce mucus and bicarbonate (protect surface from acid and digestion)

Question 11

What are parietal cells

Answer 11

Produce HCl and intrinsic factor

Question 12

What are chief cells

Answer 12

Produce enzymes e.g. pepsinogen

Question 13

What are enteroendocrine cells

Answer 13

Produce hormones e.g. gastrin, serotonin, somatostatin, and VIP

Question 14

HOW do parietal cells produce HCl

Answer 14

By active transport of H+ and passive transport of Cl into the lumen. Stimulated by gastrin, Ach and histamine

Question 15

Why don’t antihistamines prevent the secretion of stomach acid production

Answer 15

Antihistamines target H2 receptors bu histamines in stomach are H2

Question 16

What bacteria cause gastric ulcers

Answer 16

H. Pylori

Question 17

How does H. Pylori cause gastric ulcers

Answer 17

Breaks down protective mucus layer. so not producing mucus so there is no protection from stomach acid. Acid eats down layers of stomach. Initiates acute inflammatory response and becomes chronic (damage and repair happening at the same time) and so a gastric ulcer forms

Question 18

How can you fix a gastric ulcer caused by H. Pylori

Answer 18

1) Get rid of the infection

2) give PPI to enable the mucus cells to grow back over the surface

Question 19

Why can H. pylori survive acidic conditions

Answer 19

Has an alkaline surface

Question 20

What are the distinguishing features of the duodenum

Answer 20

• Have Brunners glands in the submucosa

- Receives secretions from the liver and pancreas via pancreatic and bile ducts

Question 21

What are Brunners glands and why does the duodenum have them

Answer 21

Because pyloric sphincter allows control of release of chyme so with that comes a lot of HCl. You don’t want acidic attack in duodenum. Brunners glands release alkaline secretions which neutralise chyme when sphincter opens

Question 22

Distinguishing features of jejunum and why

Answer 22

Has lots of plicae and vili because lots of absorption takes place

Question 23

Distinguishing features of lieum and why

Answer 23

Peyers patches (prominent lymphoid tissue clusters that help do lymphoid surveillance) and shorter, sparser plicae and vili

Question 24

Folds in the small intestine in descending size and where they are found

Answer 24

Plicae (mucosa and submucosa)

Villi (mucosa)

Microvilli (on the surface of columnar epithelium) (enterocytes)

Question 25

What are villi lined with

Answer 25

Simple columnar epithelium

Question 26

what is the impact of the small intestine epithelium having a high cell turnover

Answer 26

If you damage small intestine, it will easily repopulate itself

Question 27

Function of enterocytes in the small intestine epithelium

Answer 27

Columnar cells with microvilli ABSORPTION Brush border enzymes aid digestion

Question 28

Function of goblet cells in small intestine epithelium

Answer 28

Secrete mucus (more numerous distally)

Question 29

Function of panted cells

Answer 29

Large cytoplasmic granules DEFENSINS Protect against infection

Question 30

Function of enteroendocrine cells in the small intestine

Answer 30

Triangular cells with small haloed granules. Secrete locally acting hormones regulating secretion and motility

Question 31

Where are brush border enzymes produced

Answer 31

Vili

Question 32

What is luminal digestion done by

Answer 32

chyme and pancreatic secretions mix to break down food into component parts

Question 33

What is membrane digestion done by

Answer 33

Brush border enzymes

Question 34

How are proteins digested

Answer 34

By stomach and in duodenum by pancreatic enzymes. Enterocytes have membrane peptide hydrolyses to finally break down proteins to amino acids

Question 35

How are carbohydrates digested

Answer 35

Salivary and pancreatic amylase converts starch to glucose and maltose. Membrane sacharridases form monosaccharides

Question 36

How are lipids digested

Answer 36

Broken down by bile to a fine emulsion of triglycerides then pancreatic lipases to monoglyceride and free fatty acids. In the enterocytes they are reconstituted to triglycerides and coated with phospholipid and protein for transport (as chylomicrons)

Question 37

How do amino acids and monosaccharides enter the blood

Answer 37

Enter the intestinal capillaries and are taken to the liver in the portal system

Question 38

Causes of malabsorption in the small intestine

Answer 38

- Insufficient pancreatic enzyme (e.g. CF) - Insufficient bile - Loss of small intestinal surface area - Lack of mucosal brush border enzymes

Question 39

What is celiac disease

Answer 39

Intolerance to gluten. Response to that is build up of lymphocytes in epithelial layer in villi. It is a chronic inflammatory response so the villi are damaged. You lose the villi gradually. Very important to exclude gluten from diet

Question 40

Manifestations of malabsorption

Answer 40

- Dairrhoea (water) and steatorrheoea (fat) - Haemopoietic (anaemia due to deficiency in iron, folate and B12. Bleeding due to vitamin K deficiency (fat soluble) - Skeletal (osteopenia (more porous bones) due to Ca, Mg, vit D and protein deficiency) - Endocrine (impotence, infertility, amenorrhea. Hyperparathyroidism due to low Ca and Via D) - Skin : oedema and dermatitis (vit A) - Nervous system: peripheral neuropathy (vit A and B12)

Question 41

Symptoms of coeliac disease in adults and children

Answer 41

Diarrhoea, abdominal distension, malnutrition -failure to thrive in children

Question 42

What cells do the large intestine contain and what do they do

Answer 42

goblet cells for lubrication Enterocytes: absorption Enteroendocrine cells and stem cells

Question 43

Why are there more goblet cells in the large intestine

Answer 43

More difficult to shift the solid waste so goblet cells lubricate it

Question 44

What is the colon specialised for

Answer 44

Water absorption

Question 45

What cells are numerous in the colon

Answer 45

Goblet cells

Question 46

What influences transit rate in the GI tract

Answer 46

Slower: Constipation due to dehydration/lack of fibre. Consquence can be diverticulosis Faster rate: IBS and diarrhoea Blocked: Obstruction

Question 47

What causes diverticulosis

Answer 47

Low fibre. Harder to move contents of bowel so puts pressure on bowel

Question 48

How does diverticulosis present

Answer 48

Inflammation/perforation of diverticula. Lower left quadrant pain and tenderness. Mild fever and raised WBC

Question 49

How to treat diverticulosis

Answer 49

Antibiotics and withhold solid food

Question 50

What is the obstruction of small bowel due to

Answer 50

mechanical obstruction or impairment of peristalsis (due to nerve or muscle damage e.g. after abdominal surgery)

Question 51

What does the obstruction of the small bowels result in

Answer 51

Distension and loss of fluids and electrolytes -Interruption of blood flow (strangulation due to increased pressure), necrosis and rapid bacterial growth, gangrene and perforation

Question 52

Symptoms of obstruction of small bowel

Answer 52

Pain, absolute constipation, abdominal distension and vomiting, no passing of stool, vomiting if they're trying to eat

Question 53

Two main inflammatory diseases of colorectal area

Answer 53

Crohn's disease and ulcerative colitis

Question 54

What are the two sphincters in the anal canal and are they involuntary or voluntary

Answer 54

Internal anal sphincter: smooth muscle thickening at the end of the rectum (involuntary) External anal sphincter: skeletal muscle- under voluntary control

Question 55

What epithelium is the rectum

Answer 55

Columnar epithelium

Question 56

venous supply of the anal canal

Answer 56

Haemorrhoidal plexi which can become distended due to congestion: piles