G1Tract Flashcards
What is digestion
Mechanical and enzymatic process whereby ingested food is converted into simpler soluble molecules that can be absorbed
What are the 3 main nutrients that are enzymatically digested
Lipids carbohydrates and proteins.
What are the specific classes of enzymes responsible for breakdown of macro moles
Amylase breakdown starch
Lipase breakdown lipids
Protease preaksdown proteins
DNAase/RnAase breaks down nuclei acids
Enzymatic zymogen
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
How does the food move along GI tract
Peristalsis is the mechanism that allows the food movement along the GI tract it is enabled by the muscles fibres surrounding the digestive tract
Peristalsis receiving segment
Contraction of the long muscle and relaxation of the circular muscle widens the lumen prepares the receiving segment for forward moving food content
Peristalsis propulsive segment
Contraction of circular muscle relaxation of longitudinal muscles squeeze the lumen and push food forward
What is a gland
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
Salivary glands 1
Parotid salivary glands
Submandibular salivary gland
Sublingual salivary glands
Salivary glands 3
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
The pharynx
A complex muscular organ
Keeps air and digestive tracts separate
Directs food into oesophageal
What is Bolus
The chewed food mixed to saliva is called bolus
The stomach
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
Stomach acidification parietal/ oxyntic cells
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
Why is there stomach acid
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
The pancreas
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
The liver
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
The bile
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
Bilirubin
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
Bile salts
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
The pyloric sphincters
Muscular rings control the unidirectional flow of food and digestive juices through GI tract only fragments lower then 2mm can pass through the sphincter
What is chyme
Acidic mix of partially digester food and digestive enzymes that reach intestine
What is the function of the intestine
Small intestine digestion and absorption of nutrients
Large intestine e absorbtio. Of water
Small intestine general concepts
Small intestine cannot absorb complex molecules complex molecules are digested into single monomers for absorption
2 step process luminal digestion and brush border digestion
