G1Tract

Question 1

What is digestion

Answer 1

Mechanical and enzymatic process whereby ingested food is converted into simpler soluble molecules that can be absorbed

Question 2

What are the 3 main nutrients that are enzymatically digested

Answer 2

Lipids carbohydrates and proteins.

Question 3

What are the specific classes of enzymes responsible for breakdown of macro moles

Answer 3

Amylase breakdown starch
Lipase breakdown lipids
Protease preaksdown proteins
DNAase/RnAase breaks down nuclei acids

Question 4

Enzymatic zymogen

Answer 4

Digestive enzymes especially proteases are produced initially as inactive precursors called pro-enzymes or more commonly zymogens
Activation of zymogen is achieved by cleavage of a portion of the enzyme which inhibits catalytic core of protein

Question 5

How does the food move along GI tract

Answer 5

Peristalsis is the mechanism that allows the food movement along the GI tract it is enabled by the muscles fibres surrounding the digestive tract

Question 6

Peristalsis receiving segment

Answer 6

Contraction of the long muscle and relaxation of the circular muscle widens the lumen prepares the receiving segment for forward moving food content

Question 7

Peristalsis propulsive segment

Answer 7

Contraction of circular muscle relaxation of longitudinal muscles squeeze the lumen and push food forward

Question 8

What is a gland

Answer 8

An organ in the human or animal body which secretes particular chemical substances for use in the body
Endocrine for discharge into surroundings exocrine outside the body eg sweat

Question 9

Salivary glands 1

Answer 9

Parotid salivary glands
Submandibular salivary gland
Sublingual salivary glands

Question 10

Salivary glands 3

Answer 10

Saliva is necessary to maintain the moisture of the oral mucosa and lubricator the food to facilitate chewing and swallowing
Salivary glands also produce amylase to initiate start of digestion
Salivarya also contains immunoglobin for immune survaeillance
Lysozyme to kill bacteria

Question 11

The pharynx

Answer 11

A complex muscular organ
Keeps air and digestive tracts separate
Directs food into oesophageal

Question 12

What is Bolus

Answer 12

The chewed food mixed to saliva is called bolus

Question 13

The stomach

Answer 13

Mechanical digestion of food mediated by muscles
Dry. Acidic secrition of HCI
Secrete the important enzyme pepsin which digests proteins
Pepsin is produced as zygmogen only activated in acidic environment

Question 14

Stomach acidification parietal/ oxyntic cells

Answer 14

Water and carbon dioxide are combines to carbonic acid which dissociates to generate H+ and bicarbonate
Bicarbonate is exported in exchange for chloride
Chloride and potassium ions are exported in gastric lumen by conductance channels
Hydrogen ions are exported in gastric lumen by conductance channels
Hydrogen ion are actively pumped out into gastric lumen in exchange for potassium through the action of proton pump potasssium recycled
Energy comsuming process

Question 15

Why is there stomach acid

Answer 15

Activates the enzyme pepsin needed for protein digestion
Kills harmful bacteria and parasites that are ingested with food
Stimulates pancreas to produce digestive fluids enzyme to further breakdown food
Secretin is a hormone secreted in response to acid in intestine which occurs when acidic stomach passes through the pylorus secretin stimulates activity of pancreatic duct cells

Question 16

The pancreas

Answer 16

1.5 L of pancreatic fluids produced every day thise fluids poured into the intestine during digestion these fluids counteract stomach acidity
Pancreatic fluids contain many digestive enzymes for enzymatic digestion of food function linked to exocrine

Question 17

The liver

Answer 17

Production of bile which is stored in the gallbladder the main organ for storing glucose
Storage of lipids and vitamins
Metabolisms of hormones metabolism of drugs
The main functional cells of liver are hepatocyytes

Question 18

The bile

Answer 18

Produced by hepactocytes store in gallbladder secreted in the intestine
Complex solution contains several molecules and ion
Bile acids help absorption and dietary lipids
Waste products of liver detoxification
Bilirubin
Heavy metals
Chemically modified drugs eg antibiotics

Question 19

Bilirubin

Answer 19

Haemoglobin transport oxygen using an haem group
•New red blood cells are generated to replace the old ones
omale – 4.7 to 6.1 million cells per microlitre (cells/mL)
ofemale – 4.2 to 5.4 million cells/mL
•What happens to the old red cells?
•They are eaten by macrophages in a process called phagocytosis (to be discussed…)
•Macrophages are cells of the immune system (to be discussed)
•The haem group of haemoglobin is “opened up” and generates:
oIron (Fe2+), which is recycled
oBiliverdin
•Biliverdin is reduced to bilirubin and released into the circulation
•The liver removes bilirubin from the blood and releases it into the bile for excretion (after chemical modification

Question 20

Bile salts

Answer 20

4 kinds colic deoxycholic chenodeoxycholic and lithocholic
Bile salts and acids can be synthesised from cholesterol, or extracted from bloodstream by liver
When they reach small intestine they act as detergents to emulsify fat and prepare them for absorption pancreatic and intestinal fat splitting enzymes and absorption

Question 21

The pyloric sphincters

Answer 21

Muscular rings control the unidirectional flow of food and digestive juices through GI tract only fragments lower then 2mm can pass through the sphincter

Question 22

What is chyme

Answer 22

Acidic mix of partially digester food and digestive enzymes that reach intestine

Question 23

What is the function of the intestine

Answer 23

Small intestine digestion and absorption of nutrients
Large intestine e absorbtio. Of water

Question 24

Small intestine general concepts

Answer 24

Small intestine cannot absorb complex molecules complex molecules are digested into single monomers for absorption
2 step process luminal digestion and brush border digestion

Question 25

Glucose absorption

Answer 25

Glucose and galactose uptake at the lumen achieved by glucose transporter
Active transport against glucose concentration
Is powered electrochemical. Na+ gradient enabled by nk pump

Question 26

Lactose intolerance

Answer 26

Lactose is a disaccharide glucose nd galactose
Found in milk
Before weaning the enzyme lactase cleaves the lactose in its monomer constituents to enable intestinal absorption after weaning lactase levels decrease but in some individuals they maintain lactate levels
When lactate is not digested it reaches the colon where it is metabolised by bacteria and reduces water absorption by osmotic imbalances individuals with no lactase hav3 symptoms such as diahorrea vomiting an£ abdominal pain

Question 27

Lipids

Answer 27

Main enzymes responsible for lipid digestion are gastric and pancreatic lipase
Bike produced in liver enhances solubilisation and absorption of lipids in small intestine

Question 28

Lipid digestion and absorption

Answer 28

Begins in oral cavity with lingual lipase most of the digestion is however due to pancreatic lipases in pancreas lipids are hydrophobic

Question 29

Triglycerides

Answer 29

Normal level <150 mg/dl
Levels > 200. Are associated with arteriosclerosis Conakry artery disease and stroke

Question 30

Water absorption

Answer 30

Water absorbed by osmosis enterocytes actively absorb sodium chloride sodium actively absorbed in the colon by sodium channels chloride ions exchanged for bicarbonate ion across electrochemical gradient nacl moves from lumen insterstitualmm space and circulation creates osmotic pressure allows water to flow lateral intercellular spaces by osmosis and reach capillaries
1.5 lires of water a day

Question 31

Bilirubin 2

Answer 31

Bacteria in the gut metabolize bilirubin to urobilinogen
•Urobilinogen can be partially reabsorbed by the gut into the circulation
•Reabsorbed urobilinogen is filtered by the kidney and excreted in the urine, or
•It is removed by the liver and released in the bile once again

Question 32

Jaundice

Answer 32

Jaundice is a yellowish colouring of the skin and sclera of the eyes
•It is due to an accumulation of bilirubin in the body
•Normal blood bilirubin concentration is 0.5mg/dL or lower
•Bilirubin blood levels superior to 1.5mg/dL could start jaundice
•Causes of jaundice:
–Haemolysis
–Obstruction of the bile ducts
–Dysfunctional liver
•Jaundice is often a sign of liver damage