G.I. Physiology 2

Question 1

What supplies the liver?

Answer 1

Hepatic Artery (oxygenated blood) and the portal vein (absorbed nutrients)

Question 2

Where is the liver found?

Answer 2

Right hypochondrium and epigastric region extending into the left hypochondrium

Question 3

What is the falciform ligament derived from?

Answer 3

The ventral mesentery of the embryo

Question 4

What exits and enters through the porta hepatis?

Answer 4

Enter - hepatic arteries, portal vein and a small hepatic nerve plexus
Exit - hepatic ducts (x2) and lymphatic vessels

Question 5

What divides the liver into left and right lobes?

Answer 5

The fossae for the gallbladder and the inferior vena cava.

Question 6

What constituents make up the portal vein?

Answer 6

The superior and inferior mesenteric veins and the splenic vein

Question 7

Describe the levels at which the liver metabolises/detoxifies substances originating from the portal circulation.

Answer 7

2 levels
1 - Physical. Blood arriving at the liver percolates among cells of macrophage lineage, known as Kupffer cells. These are phagocytic and remove materials from portal blood, including bacteria
2 - Biochemical. Hepatocytes have a broad range of enzymes that metabolise and modify both endogenous and exogenous toxins so that the products are more water soluble and less susceptible to re-uptake
Phase 1 reaction (oxidation, hydroxylation, and other reactions catalysed by cytochrome P450 enzymes) followed by Phase 2 reactions that conjugate the resulting products with another molecule, such as glucaronic acid, sulfate, amino acids or glutathione, to promote their excretion.

Question 8

What are the main functions of the liver?

Answer 8

Bile Production
Storage
Nutrient interconversion
Detoxification
Phagocytosis
Synthesis

Question 9

Name the components of bile.

Answer 9

Bilirubin
Cholesterol
Lipids
Fat soluble hormones
Lecithin

Question 10

What hormones/systems are involved in bile secretion?

Answer 10

Parasympathetic nervous system acts through vagus nerve increase bike secretion from liver.
Secretin released in duodenum increase bile secretion by increasing water and bicarbonate ion content of bile.
CCK stimulates gallbladder contractions to release bile into duodenum.
Bile salts also have a positive feedback system

Question 11

What can the liver hepatocytes store?

Answer 11

Glucose in the form of glycogen
Lipids
Vitamins A, B12, D, E and K
Copper
Iron

Question 12

Define Liver Cirrhosis.

Answer 12

Cirrhosis is late stage scarring (fibrosis) of the liver caused by many forms of liver diseases and conditions, such as hepatitis, viruses, toxins/drugs, inherited conditions and chronic alcoholism. Each time the liver is injured, it tries to repair itself. In the process, scar tissue forms.

Question 13

What are the signs and symptoms of Liver Cirrhosis.

Answer 13

Fatigue
Bleeding easily
Bruising easily
Itchy skin
Jaundice
Ascites 
Loss of appetite
Nausea
Swelling of the legs
Weight loss
Hepatic Encephalopathy
Spider angioma
Palmar Erythema
Testicular atrophy in men
Dilated vessels
Sparse body hair
Muscle wasting

Question 14

Name the 4 tunics of the gallbladder.

Answer 14

• Inner Mucosa - folded into rugae that allow the gallbladder to expand
• Lamina Propria
• Muscularis - layer of smooth muscle that allows the gallbladder to contract
• Outer covering of serosa

Question 15

What is the arterial supply to the gallbladder?

Answer 15

The cystic artery from the right hepatic artery (a branch of the hepatic artery proper).

Question 16

How does the gallbladder protect itself from bile, which is an irritant?

Answer 16

It releases prostaglandins. When gallstones become lodged in the bile duct, it is the lack of prostaglandin that causes this to be so painful and the area becomes extremely irritated.

Question 17

Name the 3 types of Jaundice, describe them and give examples of what causes them.

Answer 17

• Pre-hepatic jaundice - the disruption happens before bilirubin has been transported from the blood to the liver. Caused by things such as sickle cell anaemia, resorption haematoma and haemolytic anaemia.
• Hepatic Jaundice - the disruption happens inside the liver; it’s caused by conditions such as Gilbert’s syndrome, viral (hepatitis, EBV), autoimmune disease, drugs, cirrhosis or other liver damage.
• Post-hepatic Jaundice - the disruption prevents the bile (and the bilirubin inside it) from draining out of the gallbladder and into the digestive system. It’s caused by things such as gallstones or head of pancreas tumours.

Question 18

List some modifiable and non-modifiable risk factors for Gallstones.

Answer 18

Non modifiable:

• Family History
• Genetic Disposition
• Ethnic Background
• Female Sex
• Age

Modifiable:

• Obesity/Metabolic Syndrome/Diabetes Mellitus/Dyslipidaemia
• Drugs - Ceftriaxone, Octreotide, Thiazide Diuretics, Female Sex Hormones
• Reduced Physical Activity
• Rapid Weight Loss
• TPN
• Diet
• Underlying Disease: Cirrhosis, Crohn’s Disease

Question 19

How long does it take for material to pass through the large intestine?

Answer 19

18-24 Hours

Question 20

What are the main cell types in the mucosa of the large intestine and which predominates.

Answer 20

Similar to small intestine;

• Absorptive
• Goblet
• Granular

Goblet cells predominate.

Question 21

Name the different muscle types of the anal sphincters.

Answer 21

Internal Anal Sphincter = Smooth Muscle

External Anal Sphincter = Skeletal Muscle

Question 22

What is the blood supply to the large intestine?

Answer 22

Superior Mesenteric Artery gives rise to:

• Ileocolic artery -> anterior and posterior cecal artery and appendicular artery
• Right colic artery
• Middle Colic artery

Inferior Mesenteric Artery gives rise to:

• Left colic artery
• Sigmoid arteries
• Superior rectal artery

Question 23

What is the main difference between Crohn’s Disease and Ulcerative Colitis?

Answer 23

Crohn’s Disease can affect any of the G.I. tract, where as ulcerative colitis just affects the colon and the rectum.