Digestive System

Question 1

Describe the structure and position of the gall bladder

Answer 1

Pear shaped, beneath the liver, approximately 10cm long, connected to the liver by connective tissue. Similar to the digestive tract in structure however does not have a submucousal layer. Epithelial layer arranged into rugae.

Question 2

What is the function of the gall bladder?

Answer 2

Absorb water from the bike making it 10x more concentrated than when it was produced in the liver. Mucus is secreted into the Nile which is stored until required by the digestive tract.

Question 3

Outline the movement of bile through the gall bladder.

Answer 3

Bile enters the gall bladder from the liver through the cystic duct and exits by the same route. Secretion of bile from the gall bladder into the duodenum is controlled neurally and hormonally. The stimulation of the vagus nerve causes the release of hormones secretin and CCK. when fats are present in chyme entering the duodenum and the hormones are present the gall bladder contracts to secrete bile into the small intestine.

Question 4

What is the duodenum?

Answer 4

The first part of the small intestine immediately beyond the stomach.

Question 5

What is chyme?

Answer 5

Thick semi fluid mass of partially digested food that is formed in the intestines and stomach during digestion.

Question 6

What is bile and what is it made of?

Answer 6

It’s function it to aid the digestion of fats in the duodenum. It is composed of bile acids, bile pigments, bile salts and cholesterol. Alkaline. Green yellow colour.

Question 7

Outline the blood and nerve supply to the bile duct

Answer 7

Cystic artery supplies the gall bladder and bile ducts with oxygenated blood and the cystic vein drains away deoxygenated blood. Nerve supply from the autonomic nervous system.

Question 8

Describe the location of the bile ducts

Answer 8

Hepatic ducts leave the liver through the portal fissure and join to form the common hepatic duct.
Cystic duct from the gall bladder joins the common hepatic duct to form the common bile duct which passes behind the head of he pancreas.
This then joins the main pancreatic duct before it enters the duodenum through the hepato pancreatic sphincter

Question 9

What are the three accessory structure of the gastrointestinal system?

Answer 9

The liver
The gall bladder
The pancreas

Question 10

Describe the general features of the liver

Answer 10

Largest gland in the body weighing on average 1.5 kg.
Essential to life and can continue to work even when a large portion of it has been damaged.
Situated in the upper right section of the abdominal cavity the right hypochondriac region under the diaphragm.
Partially protected by the lower ribs.

Question 11

What is the peritoneum?

Answer 11

Continuous transparent membrane which lines the abdominal cavity and covers the abdominal organs

Question 12

Describe the macrostructure of the liver

Answer 12

Covered completely in peritoneum
Anatomically divided into right and left lobes by the falciform ligament.
The falciform is attached to the under surface of the diaphragm and holds the liver in position.
The ligamentum teres extends from the falciform ligament down to the umbilicus which is a remnant of the umbilical vein present in the foetus.
The portal fissure is a structure situated on the posterior surface of the liver where vessels and nerve fibres enter and leave.

Question 13

Describe the microstructure of the liver

Answer 13

Composed of hepatic lobules formed from hepatocytes
Central sinusoid located in each lobule
Sinusoids carry venous and arterial blood which come into contact with the hepatic lobules.
Kupffer cells line the walls of sinusoids. They are specialised cells which destroy worn out blood cells, bacteria and toxins.
Surrounding lobules are canals carrying a branch of the portal vein, hepatic artery and small bile duct.

Question 14

How much bile is produced daily and where is it stored?

Answer 14

750ml-1L of bile daily in an adult. Stored in the gall bladder.

Question 15

What happens to the majority of bile salts?

Answer 15

They are reabsorbed in the ileum and returned to the liver is the portal vein to be recycled.

Question 16

What is bilirubin?

Answer 16

The main bile pigment in the liver.
Product of the breakdown of red blood cells.
Hepatocytes process fat soluble bilirubin produced by haemolysis and change it to water soluble bilirubin.
This can then be broken down in the digestive system and excreted in the faeces or the renal system.

Question 17

What are the three functions of the liver?

Answer 17

Metabolism
Storage
Secretion

Question 18

Outline the livers role with regards to storage

Answer 18

Stores vitamins and elements iron and copper. Also store glucose as glycogen.

Question 19

Outline the livers role with regards to secretion

Answer 19

Bile is produced by her liver and secreted from the gall bladder into the digestive tract to aid the breakdown of fats. Urea is formed in the liver from waste products such as ammonia and carbon dioxide which is excreted in the urine.

Question 20

Outline the livers role with regards to metabolism

Answer 20

The liver regulates blood sugar levels by converting glucose to glycogen in response in insulin and glycogen to glucose in response to glucagon.
It mobilises stored fat for use by body cells.
The liver detoxifys drugs and poisons as well as deactivating hormones no longer needed in the body.
Heat is a by product of these metabolic processes. Liver helps to maintain core body temperature which is essential for metabolism to work at an optimum rate.

Question 21

Outline the blood and nerve supply to the liver

Answer 21

The hepatic artery supplies the liver with oxygenated blood and the portal vein brings nutrient enriched blood directly from the digestive organs.
Hepatic veins drains intone inferior vena cava.
The autonomic nervous system controls the liver function.

Question 22

Describe the appearance of the pancreas

Answer 22

Soft, grey pink gland, 15cm long.

Consists of an expanded head tucked into the surge of the duodenum, a body and a narrow tail lying behind the stomach.

Question 23

Where is the pancreas located

Answer 23

Transverse lie, across posterior abdominal wall behind the stomach

Question 24

Describe the movement of secretions from the pancreas

Answer 24

Secretions are passed along two ducts, one of which joins the common bile duct before entering the duodenum and the other entering the duodenum directly.
Pancreatic duct - common bile duct then duodenum
Accessory duct - straight into duodenum

Question 25

Describe the exocrine tissue of the pancreas

Answer 25

Forms the majority of the pancreas
Consists of lobules containing alveoli lined with secretory cells. Each alveoli drains into a duct which join together to leave the lobules into the 2 central ducts.

Question 26

Describe the endocrine tissue of the pancreas

Answer 26

Found throughout the pancreas in small collections of specialised cells called the islets of langerhans.
Islets contain alpha and beta cells.
Alpha cells secrete glucagon, a hormone which converts glycogen to glucose when blood sugar levels are low.
Beta cells secrete insulin, a hormone which converts glucose to glycogen when blood sugar levels are high.

Question 27

Describe the pancreatic juice and its function

Answer 27

Approx 1500ml produced daily by exocrine glands
Contains water, salts, sodium bicarbonate and enzymes.
Sodium bicarbonate gives the kancreatic juice alkaline pH which is necessary for enzymes to act on chyme in the duodenum.
Regulation of pancreatic juice is neural and hormonal.

Question 28

What is the function of the pancreas

Answer 28

Exocrine glands in the pancreas produce pancreatic juice which contain enzymes for the breakdown of nutrients.

Question 29

List examples of enzymes that are found in the pancreatic juice

Answer 29

Trypsin and chymotrypsin digest proteins.
Pancreatic amylase digests carbohydrates
Pancreatic lipase digests fats

Question 30

Outline the blood and nerve supply to the pancreas

Answer 30

Splenic and mesenteric arteries and veins supply and remove blood from the pancreas.
Nervous control is by the autonomic nervous system

Question 31

What causes most of the physiological changes in the gastrointestinal system in pregnancy?

Answer 31

Relaxation of the smooth muscle because of progesterone

Question 32

What is the digestive system responsible for?

Answer 32

Breaking down ingested food and fluids into molecules small enough to be absorbed in the blood stream.
Removing waste products from the body.

Question 33

Describe how the digestive system is altered in pregnancy

Answer 33

Increased levels of hormones in the body
This does not prevent sufficient nutrients from being absorbed however it can lead to discomfort for the woman which is aggravated by the growing uterus in the abdomen.

Question 34

How are nutrients obtained in the foetus?

Answer 34

Via the placenta. Digestive organs are patent and become functional after birth

Question 35

Outline the microstructure of the digestive tract

Answer 35

Mucosa
Submucosa
Muscle layer
Serosa