GI Tract: Fine-tuning revision Flashcards by Neil Srivastava

Does bile contain digestive enzymes

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Does bile contain conjugated or unconjugated bilirubin

Conjugated ONLY

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How does storage and concentration of bile in the gallbladder affect bile pH?

It DECREASES pH

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Difference in the type of saliva secreted in serous and mucous glands

Serous is very WATERY (remember serous is a mixture of water and amylase)

Mucous is very thick and viscous (needed for lubrication)

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Where is iodide mainly excreted

In the saliva

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What cation can be found in the saliva

Calcium ions

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What is the pH of saliva

6-7 (NEUTRAL)

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What happens to the rate of saliva secretion when vomiting is about to take place

It increases in order to buffer the contents before it can cause any damage

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Where is the swallowing reflex centre

Medulla oblongata

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Is the swallowing reflex more effective standing or laying down

Standing because we then have the assistance of gravity

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What needs to happen to iron before it can be absorbed at the duodenum

It needs to be reduced by HCL from trivalent ferric iron to divalent ferric iron

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What cleaves pepsinogen to pepsin

HCL

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Is vitamin C stored in the liver?

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Where is vitamin C excreted

In the kidneys

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How does ingestion of fibres influence bowel movement

It stimulates peristaltic waves by adding ‘bulk’ to the food residues

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How are mucosal cells protected from gastric juices

Due to a coating of mucous which is IMPREGNATED with HCO3-

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How will an increase in body fat affect body water volume

Will reduce it

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Is saliva essential for digestion?

Nope, enzymes like ptyalin and HCL only assist digestion and can be carried out by chymotrypsin and trypsin in the duodenum

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Where is calcium mainly absorbed

Duodenum

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Do fatty acids get absorbed in the capillaries

They can do if they are small enough. Most will move in via lymphatics (lacteals) if they are too big and need to be esterified and packaged into chylomicrons

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Where is cholesterol mainly excreted

In the bile (think HDL)

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What factor will cause an increase in the risk of gallstone development

An increase in cholesterol: Bile salts and Cholesterol: Lecithin ratios

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Will an increase in Bile salts: Cholesterol or Lecithin: Cholesterol increase the risk of gallstone formation

No, these favour micelle formation which reduces chances of gallstones forming

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Can removal of the stomach impair iron absorption

Yes because it can only be absorbed at the duodenum as divalent ferric iron

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What symptoms can I expect to see in Hepatic Jaundice

Low prothrombic levels Low fibrinogen levels in the blood Low albumin levels

What papillae have no taste buds

FILLIFORM FUNGIFORM CIRCUMVALLATE FOLATE

Name the three branches of the coeliac trunk

- Left gastric artery - Common hepatic artery - Splenic artery

Is the duodenum retro or intraperitoneal

Retroperitoneal

Where is Meckel's diverticulum located

It is an appendix-like structure that is found at the ileum

Describe absorption of amino acids and glucose at the SMALL INTESTINES

They are moved into the intestinal epithelial cells by SECONDARY ACTIVE TRANSPORT with Na+

What ion moves into the intestinal epithelial cell with sodium ions

Cl-

How does Cl- enter the intestinal epithelial cell

Counter-transport with HCO3- ions

How does the Na+ and Cl- move out of the intestinal epithelial cells and into the interstitial

Na+/k+ ATPase Cl- ion channels

What other way does Na+ enter the intestinal epithelial cell

Na+/H+ ATPase

What two major ions are secreted in the large intestines and ileum

HCO3- and Cl-

Where is HCO3- absorbed , why and how

At jejunum and duodenum ``` H+ is exchanged with Na+ H+ reacts with HCO3- to give H2CO3 H2CO3 -> H2O + CO2 CO2 is re-absorbed and expired H20 remains in chyme ``` Prevents pH from becoming too high

Define Amphipathic

A compound that shows both lipophilic + hydrophilic properties

Where are meissner's plexus located

In gut submucosa

Where is Auerbach's plexus located

Between the two layers of the muscularis propria

What is the head of the pancreas supplied by

Inferior pancreaticoduodenal artery branch of the superior mesenteric artery

How does liver function affect the body if it fails

Increased size of male breasts as oestrogens and progesterones will not get conjugated Increased unconjugated bilirubin Increased tendancy to bleed

Why is dividing the vagal nerve supply to the stomach helpful for treating peptic ulcers

Less ACh released so less gastrin acidity

How will removing the pyloric antrum affect peptic ulcers

Reduce them as this removes a lot of the G cells in the stomach, reducing HCL release

What receptors do histamine bind to

H2 receptors

When does urobilin in the urine get darker

When exposed to light

Where are chymotrypsin and trypsin produced

Pancreas

Why can liver failure result in more salt and water retention

Because it is needed to conjugate aldosterone which won't be able to function at the liver properly otherwise

Can liver failure lead to oedema? If so, why?

Yes, because less albumin will be produced

What receptors does ACh bind to at the stomach

M1 - muscarinic receptors

How does portal hypertension affect vascular resistance through the sinusoids

Increases it

How does portal hypertension affect blood flow through the liver

Decreases it as blood flow will be diverted straight to the central vein as opposed to circulating around the sinusoids for a while

How will portal hypertension affect the volume of fluid in the peritoneal cavity

Increase it as there will be a higher hydrostatic pressure so more filtration will take place

What is D3 also known as

Cholecalciferol

What is D2 also known as

Ergocalciferol

What is the main source of vit D

UV rays

What do we have in our skin that starts off production of D3

7-Dehydrocholesterol

What is 7-dehydrocholesterol

Inactive precursor of D3

What happens to 7-dehydrocholesterol

It reacts with UV rays to produce cholecalciferol

What wavelength of UV is needed for activation of D3 to take place in the skin

270-300nm (optimal between 295 to 297nm)

Can we overdose from vit D with a lot of exposure from the skin?

Nope

Wht happens to vit D at the liver

converted to calcidiol

What happens to calcidiol at the kidney

Converted to calcitriol

What is the formula for calcidiol

25(OH)D

What is the formula for calcitriol

1,25(OH)2D

Where does vit D act

Intestines, Kidneys + Bone

Where is glucose absorped at the GI tract

Duodenum and small intestines

What part of the brain co-ordinates the vomiting reflex

Medulla Oblongata

What obstruction is vomiting indicative of

High intestinal obstruction

When does muscle tone in the oesophagus increase

Gastrin secretion to prevent reflux of gastric contents

When does muscle tone in the oesophagus decrease

During pregnancy - increases occurance of heart burn

What secretion causes disaccharides to be broken down

Intestinal secretions

What secretion causes triglycerides to be broken down

Pancreatic secretions

What secretions causes breakdown of nucleic acids

Pancreatic secretions

What compound causes contraction of the oesophageal-gastric sphincter

Gastrin

At what vertebral level is the gastro-oesophageal junction at

T11

What needs to happen to all carbohydrates before they can be absorbed by the body

They need to be broken down in to monosaccharides first

What happens to carbohydrates in the mouth

They are broken down by Ptyalin - an alpha amylase

What gland secretes ptyalin

Parotid Glands

What is the optimal pH that ptyalin works at

6.7

What happens to carbohydrates at the small intestines

The 1-4 glycosidic bonds of the carbohydrates are broken down but 1-6 glycosidic bonds are preserved

What are the end-products of digestion of the 1-4 glycosidic bonds in carbohydrates

- Maltose - Maltotriose - Alpha limit dextrins

What are alpha-limit dextrins

These are branched units with 8 units in total

What happens to maltose, maltotriose and alpha limit dextrins in the duodenum

They are broken down by oligosaccharidases in the microvilli: Maltase Lactase Sucrase Alpha-limit dextrase This produce monosaccharides

Name the three major monosachharides

- Glucose - Galactose - Fructose

How is Galactose absorbed

Galactose and glucose share the same SGLT co-transporter so compete with each other to be absorbed Galactose then moves from the intestinal epithelial cells into the interstitium via facilitated diffusion through GLUT channels

How does Fructose absorption differ from galactose absorption

Fructose has a different transporter - GLUT

Where are most carbohydrates absorbed

Duodenum

Where are these carbohydrates then moved from the duodenum

Into the hepatic portal vein and then on to the liver

What three things happen to glucose in the liver

- Glycogenesis - Production of glucose - Glycolysis

Why does glycolysis take place in the liver

- Production of alpha-glycerol phosphate and fatty acids that are needed to form triglycerides

How are alpha-glycerol phosphates produce from glycolysis of glucose

Reduction of dehydroxyacetone phosphate

What happens to triglycerides produced in the liver

They are placed into VLDLs

What are VLDLs

Lipoproteins that contain more fat than proteins

Why do lipoprotein lipases have to breakdown VLDLs as they circulate in the blood

Because they are too big to move through the capillary wall

How long do glycogen stores last for

12 Hours

How long do lipids last for in the body

3 months

When does protein become a source of energy

During prolonged starvation

How much of the body's total energy requirement is contributed to by the liver and the brain

40%