6.1 Digestion Flashcards
Two major organs groups in digestive system
Alimentary canal: food actually passes (esophagus, stomach, small / large intestine
Accessory organs: aid in digestion but don’t trasnport food (salivary glands, pancreas, gall bladder, liver)
Explain the components of alimentary canal and their functions
- esophagus: connects oral cavity and stomach, food with saliva via peristalsis is moved down
- stomach: temporary storage, food is mixed by churning, protein digestion begins, lined with gastric pits which release digestive juices
- small intestine: long highly folded tube, food substaces absorbed, epithelium invaginations - villi
- large intestine: water and dissolved minerals absorbed
Explain the accessory organs and their functions
- salivary glands: secrete saliva for chemical breakdown in mouth (amylases - starch)
- pancreas: secrete enzymes into small intestine (amylases, lipases), secrete hormones for blood sugar regulation (insulin, glucagon)
- liver: uses substances absorbed by small intestine to compose new compounds (detoxification, haemoglobin breakdown, bile production, metabolism, storage - glycogen)
- gall bladder: stores bile (emulsification of fats) produces by liver, via bile duct released into small intestine (fats absorbed in small intestine into lacteals inside villi)
Mechanical vs chemical digestion
Mechanical: food physically broken down into smaller pieces - chewing, churning (stomah), segmentation (small intestine)
Chemical: food is broken down by chemical agent action - saliva (salivary glands - enzymes), stomach juice (gastric glands- enzymes and pH), bile (bile salts intearct with fats - emusification into small droplets - available for lipase)
Explain peristalsis vs segmentation
Peristalsis - mechanism of movement in esophagus, stomach, small / large intestine
Continous segmentation of longitudinal smooth muscle - rynthmically contract and relax - food _moved unidirectionall_y along the alimentary canal
Segmentation - contractions of circular smooth muscle - moves chyme (food paste) in both directions for greater mixing with digestive juices
Where are most of enzymes produced
In the PANCREAS
Explain digestion of each macromolecule
CARBOHYDRATES: begins in mouth, amylase from salivary glands and pancreas - further digestion in small intestine (enzymes immobilised in epithelium), humans don’t have cellulase
PROTEINS: begins in the stomach - proteases (acidic), smaller proteins digested in small intestine - endopeptidases (neutral)
FATS: begins in intestines - bile emulsification, small droplets digested by lipases (secreted by pancreas)
NUCLEIC ACIDS: pancrease releases nucleases
What are the main tissues of small intestine?
- serosa: protective layer
- muscle layer: longitudinal (peristalsis) and circular (segmentation) muscles
- submucosa: connective tissue separating muscle and innermost layer
- mucosa: highly folded innner layer which absorbs nutrients from intestine lumen into the blood stream and lacteal
Features of villi
How are nutrients absorbed by villi?
Between epithelial cells tight junctions - nutrients can pass only through specific membrane transport machanisms
- co-transport: active translocation is coupled with passive movement - glucose + am a are co-transported by active Na+ translocation
- facilitated diffusion: channel proteins - located near immobilised enzymes - localised concentration gradient - fructose, vitamins
- osmosis: water uptake
- simple diffusion: hydrophopic may diffuse - fats - straight into lacteals
- bulk transport: pinocytosis - in intestines vesicles can form to absorb fluids with dissolved nutrients
What is the digestion sequence of starch?
STARCH - amylose (linear) or amylopectin (branched)
- in mouth machanically and chemically - salivary amylase, in intestines - pancreatic amylase = amylose -> maltose, amylopectin -> dextrin = both digested by maltase (hydrolysis) which is fixed on the epithelium of small intestine +> glucose used for ATp or stored as glycogen in liver
How does the pancreas control blood sugar?
Pancreas secretes amylase in exocrine glands to intestine for primary digestion of starch - secretes insulin and glucagon hormones by endocrine glands into blood
Insulin (stimulates glycogen formation -liver and adipose) and glucagon (stimulates glycogen breakdown) regulate blood sugar levels
How can digestion be modelled?
By dialysis tubing - selective by size - small pass, large dont
