Topic 6.1 Flashcards
Produce an annotated diagram of the digestive system.
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Label the following diagram of the villi
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Label the following diagram of the small intestine.
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Peristalsis
- Involuntary contraction of circular and longitudinal muscles
- Move food in one direction only (away from mouth)
To where does the pancreas secrete enzymes?
- The pancreas secretes enzymes into the lumen of the small intestine
List the enzymes in pancreatic juice and their reactions
- Amylase (starch –> maltose)
- Lipase (triglycerides, phospholipids –> glycerol and fatty acids)
- Proteases (proteins/peptides –> amino acids)
Outline the function of mouth
- Voluntary control of eating and swallowing
- Mechanical digestion of food by chewing and mixing with saliva
- Chemical digestion of starch with amylase in saliva
Outline the function of saliva
- Lubricants
- Enzymes that start starch digestion (amylase)
Outline the function of esophagus
- Movement of food by peristalsis from the mouth to the stomach
Outline the function of small intestine
- Final stages of digesion of lipids, carbohydrates, proteins, and nucleic aics
- Neutralize stomach acid (in duodenum)
- Absoption of nutrients
What are the three parts of small intestine?
Duodenum, jejunum, ileum
Outline the function of pancreas
Secretion of lipase, amylase and protease
Outline the function of liver
Secretion of surfactants in bile to break up lipid droplets
Outline the function of Gall bladder
Storage and regulated release of bile
Outline the function of large intestine
- Reasbsorption of water
- Further digestion especially of carbohydrates by symbiotic bacteria
- Formation and storage of feces
Bolus
Grinded food (after chewing)
Describe the process of swallowing
- Soft palate moves backwards and up to seal the nasal passage
- Trachea moves up and under the epiglottis to prevent choking
Cardiac sphincter
- Separates the esophagus and stomach
- Helps to push food into stomach
- Prevent food from backflowing
Outline the function of stomach
- Mechanical digestion (churning and mixing with secreted water and acid)
- Kills foreign bacteria and other pathogens in food
- Initial stages of protein digestion
Describe the purpose of villi
- Increase surface area of epithelium
- Increase the efficiency of nutrient absorption
What does the villi absorb from the lumen?
- Monomers such as glucose, amino acids, fatty acids, nucleotides
- Mineral ions such as calcium, potassium, sodium
- Vitamins such as ascorbic acid
Describe how triglycerides are transported across the villus epithelium cells
- Digested into fatty acids and monoglycerides
- Absorbed into villus epithelium cells by simple diffusion
- Fatty acids are also absorbed by facilitated diffusion
- Once inside the cells, fatty acids and monoglycerides form triglycerides to ensure that they don’t diffuse back out into the lumen
Describe how triglycerides are transported across the lacteal
- Triglycerides coalesce with cholesterol to form droplets that is coated in phosopholipids and protein (lipoprotein)
- Released by exocytosis through the plasma membrane and enter the lacteal or blood capillaries
Describe how glucose is transported across the villus epithelium cells
- Polar and hydrophilic (cannot diffuse across)
- Sodium-potassium pumps creates a low concnetration of socium ions inside the cells (using ATP)
- Socium-glucose cotransporter proteins in the microvilli transfer a sodium ion and a glucose molecule together from the lumen into the cells
- Facilitated diffusion that depends on sodium concentration (established by active transport)
Describe how glucose is transported across the blood capillaries
- Glucose channels move the glucose from the cytoplasm to interstitial spaces and then blood capillaries
Why can’t we digest cellulose?
We don’t have the bacteria required to make cellulase (enzyme that digests cellulose)
