GI S1 (Done)

Question 1

Breifly describe the major function of the GI tract

Answer 1

Food (a complex mix of large molecules) is processed into a:

• Sterile
• Isotonic
• Neutral

Solution of:

• Small sugars
• Amino acids
• Small Lipids
• Other small molecules

Ready for absorption and excretion

AKA Digestion

Question 2

In order what are the smaller processes involved in digestion?

Answer 2

Initial physical disruption

Ingestion and transport to storage

Initial chemical disruption and suspension (chyme)

Disinfection

Controlled release of chyme

Dilution and neutralisation

Completeion of chemical breakdown

Absorption of nutrients and electrolytes

Final absorption of water and electrolytes

Excretion

Question 3

What are the major functions of the mouth?

Include brief descriptions of how each process works

Answer 3

Mastication

Protection with saliva:

Wetting

Bacteriostatic

Alkaline High Ca2+

Start digestion:

Salivary amylase

Swallowing:

Formation of bolus

Entrance to oesophagus

Question 4

What are the major function of the oesophagus?

Answer 4

Transport of bolus of food to stomach

Question 5

What are the major functions of the stomach?

Include brief descriptions of how each process works

Answer 5

Storage:

Expands/relaxes to accomodate food

Initial disruption:

Contracts rhythmically to mix and disrupt food/chyme

Secretes acid and proteolytic enzymes to break down tissues and disinfect

Deliver chyme to duodenum

Question 6

What are the major functions of the duodenum?

Include a brief description of how this process works

Answer 6

Changes Chyme:

Draws water from ECF to dilute chyme

Enzymes added from Liver and Intestine

Alkali added to the chyme from Liver and Pancreas

Question 7

What are the major functions of the small intestine?

Include brief descriptions of how each process works

Answer 7

Absorption of nutrients and electrolytes:

Fluid passes through slowly

High surface area

Epithelial cells absorb molecules actively and passively (often coupled to Na+ absorption)

Pass absorbed material into portal vein

Absorbs majority of water (1.5L)

Question 8

What are the major functions of the Large intestine

Answer 8

Final absorption of water (0.15L)

Slow transit

Forms faeces which accumulate in sigmoid and descending colon

Question 9

What are the major functions of the rectum?

Answer 9

Accepts faeces periodically propelled into rectum

Urge to defecate

Controlled relaxation of sphincters and expulsion of faeces

Question 10

Label the boxes

Answer 10

From top left anticlockwise:

Parotid salivary gland

Submandibular salivery gland

Sublingual salivary gland

Oral cavity

Pancrease

Liver

Gallbladder

Duodenum

Common bile duct

Transverse colon

Ascending colon

Descending colon

Cecum

Appendix

Rectum

Anus

Samll intestine (Ileum)

Pancreatic duct

Stomach

Oesophagus

Tongue

Pharynx

Question 11

What are the 4 layers of the GI tract wall?

Give a very brief description of each

Answer 11

Mucosa:

Epithelium and thin layer of muscularis mucosae

Submucosa:

Fibroelastic tissue with vessels, nerves, leucocytes and fat cells

Muscularis externae:

Inner circular and outer longitudinal layerss of smooth muscle with the myenteric plexus between

Serosa/Adventitia:

Thin outer covering of connective tissue

Question 12

What is the purpose of variations in the wall structure of the GI tract?

Answer 12

Provide adaptations for specific functions whilst remaining a continuous hollow tube

Question 13

Describe how the GI tract balances content added and absorbed in the gut

Answer 13

Addition:

We at 1Kg of food a day

Add about 1.5L of saliva

Add about 2.5L of gastric secretions

Add up to 9L of water and alkali in duodenum

Total - 14L

Absorption:

Small intestine absorbes about 12.5L of fluid

Large intestine abosrbs about 1.35L

Leaves 0.15Kg of Faeces

Question 14

What factors of gut function reguire control and how is control acheived?

Answer 14

Motility and secretion must be controlled

Range of mechanisms:

• Neural
• Paracrine
• Endocrine

Question 15

How is the gut controlled neurally?

Answer 15

Somatic:

Ingestion and excretion

Autonomic:

Parasympathetic most significant

Post ganglionic neurones for plexuses (Enteric nervous system)

Co-ordinates secretion and motility

Range of neurotransmitters

Question 16

Give examples of chemicals involved in paracrine control of the gut

Answer 16

Histamine in stomach

Various vasoactive substances

Question 17

How is Endocrine control involved in gut processes?

Answer 17

Produces its own hormones which travel in the blood within the gut

Range of hormones controlling:

Secretion of stomach acid

Alkali secretion from liver and pancreas

Enzyme secretion

Question 18

Give a brief description of Dysphagia

Answer 18

Difficulty swallowing

Can be due to musculature or neurological problems or malignancy

Tumours of the oesophagus are squamous cell carcinoma high up and adenocarcinoma lower down

Question 19

Give a brief description of acid reflux

Answer 19

Sphincter between oesophagus and stomach weakens and acid refluxes into oesophagus causing irritation and pain

Question 20

Give a brief description of Barret’s oesophagus

Answer 20

Metaplasia of lower squamous epithelium to gastric columnar to protect against acid reflux

Question 21

Give a brief description of oesophageal varices

Answer 21

Portal venous system is overloaded due to cirrhosis, blood is diverted to the oesophagus throught connecting vessels

This leads to dilation of the submucosal veins in the lower oesophagus

Question 22

Give a brief description of peptic ulceration

Answer 22

Area of damage to stomach or duodenal mucosa

Usually due to irritation from gastric acid

H. Pylori is a common cuse as it leads to a breakdown of the protective mucous layer in the stomach

Question 23

Give a brief description of pancreatitis

Answer 23

Inflammation of pancreas cuaing considerable pain

Characterised by release of amylase into bloodstream

Question 24

Give a brief description of jaundice

Answer 24

Build up of bilirubin in the blood due to pre-hepatic, post-hepatic and hepatic causes

Prehepatic:

excess haemoglobin breakdown

Hepatic:

Liver cells unable to process bilirubin

Post-Hepatic:

Obstructive, due to obstruction of bile duct causing a back up of bile (causing liver damage)

Question 25

Give a brief description of gallstones and a commonly associated symptom

Answer 25

Precipitation of bile acids and cholesterol in the gallbladder

Movement within the gallbladder or stones blocking the bile duct may lead to Biliary colic a painful condition produces by frustrated peristaltic waves trying to shift the stone

Tumours of the pancreas may also bock the bile outflow

Question 26

Give a brief description of appendicitis

Answer 26

Inflammation of appendix often due to lymphoid hyperplasia or faeocaliths

Presents as pain in right side which localises to right lower quadrant (Specifically McBurney’s point - 1/3 of the distance from ASIS to umbilicus)

Question 27

What is peritonitis?

Answer 27

Inflammation of peritoneum

Question 28

Give a brief description of haemorrhoids

Answer 28

Vascular structures in the anal canal that aid in stool control

Con become swollen and inflammed

Pain, itchiness and haemoatochezia are associated

Question 29

Give a brief description of Prolapse in regards to the GI tract

Answer 29

Prolapse is when an organ ‘falls out of place’

E.g. Rectum can prolapse

Question 30

Give a brief description of a diverticulum

Answer 30

High pressure in the colon produces an outpouching to form a hollow

Commonest in the sigmoid colon due to blood supply

Question 31

Give a brief description of a Meckel’s diverticulum

Answer 31

Pouch in the lower part of the intestine

A vestigial remnant of the yolk sac

Can produce gastric mucosa which may then produce gastric acid, causing irritation