FINAL - Digestion Flashcards
Outline why food needs to be digested.
- Macromolecules must be broken down into smaller molecules so they are small enough to be absorbed into your bloodstream
Explain how starch is digested.
- Hydrolyzed into maltose in the small intestine by amylase produced by the pancreas
Explain how proteins are digested.
- Hydrolyzed into peptides in the stomach by pepsin produced by the gastric glands
- Hydrolyzed into amino acids in the small intestine by protease produced by the pancreas
Explain how fats are digested.
- Hydrolyzed into glycerol and fatty acids in the small intestine by lipase produced by the pancreas
Explain the nervous and hormonal mechanisms that control the secretion, volume, and content of gastric sections.
- Smell/sight of food causes brain to send nerve impulses via vagus nerve to medulla
- glands in stomach secrete gastric juice
- chemo- / stretch receptors in stomach wall detect food
- releases gastrin hormone; stimulates secretion of acid
Outline the roles of the stomach.
- Produces acid to break down molecules
- Churns food in mechanical digestion
- Produces protease/pepsin to digest proteins
Outline the roles of HCl in the stomach.
- Kills bacteria
- Activates pepsin into pepsinogen for protein digestion
- Maintains low pH of stomach
Outline the causes, consequences, and treatment of stomach ulcers.
Cause: Helicobacter pylori infection
Cons: digestion of stomach lining by HCl (stomach ulcers), inflammation
Treatment: PPIs, antacids to decrease acidity
Outline the use of PPI’s to reduce stomach acid secretion.
- Acidity achieved by proton pumps
- PPIs bind irreversibly to proton pumps
- Lowers amount of acid produced
Describe how the structure of a villus is adapted to its function.
Function: Efficient absorption of nutrients in the small intestine
Epithelial cells - surround each villus (decreases diffusion distance for nutrients into bloodstream)
Rich Capillary Network - large concentration gradient (between blood and the fluid in the small intestine)
allows for rapid absorption of nutrients
Lacteals - Absorb lipids (into lymphatic system – transports fats, drains tissues of excess fluids)
Intestinal crypts - release juices that act as ‘carrier fluids’ for nutrients
Describe the method of transport used to absorb the products of starch digestion in the small intestine.
Facilitated diffusion - movement through channel proteins
Describe the method of transport used to absorb the products of protein digestion in the small intestine.
Active transport - against concentration gradient using proton pumps
Describe the method of transport used to absorb the products of lipid digestion in the small intestine.
Endocytosis - by means of vesicles (lipoprotein particles)
Distinguish between exocrine and endocrine glands (with regard to their structure and function)
Exocrine glands - secretes substances through ducts / secretory cells to an epithelial surface (salivary glands, gastric glands)
Endocrine glands - secretes hormones into the bloodstream (liver)
Outline the benefits of a diet rich in fiber.
- Prevents constipation
- Decreases hunger so less obesity
- Ensures correct movement of food through intestines
- Decreased risk of colon cancer
State which substances are egested by the human body.
BELCH
Bile pigments
Epithelial cells
Lignin
Cellulose
Human microflora
Outline the effects of the cholera toxin.
- V. cholerae produces toxin
- Toxin causes ions to be pumped into small intestine
- Drawing water thru osmosis into intestine
- Leading to dehydration, diarrhea, vomiting
Explain how the pancreas maintains homeostatic levels of glucose in the blood.
- Homeostasis is the maintenance of a constant internal environment
- Negative feedback controls glucose levels
- Pancreas produces hormones that regulate levels of glucose
- If glucose lvls are high, beta-cells produce insulin
- Insulin causes cells to take up glucose (lowers lvls)
- Liver stores excess glucose as glycogen
- If blood/glucose levels are low, alpha-cells produce glucagon
- Glucagon causes liver two break down glycogen into glucagon (increases lvls)
Explain the causes, consequences, and treatment of Type I diabetes.
Cause: Autoimmune reaction, beta cells of pancreas become destroyed
Cons: high blood sugar, glucose in urine
Treat: insulin injections
Explain the causes, consequences, and treatment of Type II diabetes.
Cause: obesity, lack of exercise
Cons: desensitized to insulin
Treat: consume complex carbs for gradual release of glucose into blood, eat more high fiber foods to satisfy appetite but not get absorbed, reduce intake of fats to reduce weight.
Outline the dual supply of blood to the liver.
- It is blood from hepatic artery and hepatic portal vein
- Blood in hepatic artery provides oxygen to liver
- Hepatic vein carries blood rich in nutrients from intestines
- Allows glucose to be stored and released in response to hormones
Explain how the liver regulates nutrient levels in the blood (including nutrients that are stored by the liver).
- Liver stores glucose as glycogen (iron is also stored)
- Releases glucose under influence of insulin or glucagon depending on blood/glucose levels
- Kupffer cells break down red blood cells by phagocytosis
- Hemoglobin slept into heme/globin
- Iron from heme carried to bone marrow
- Excess cholesterol converted to bile salts
Explain how the liver breaks down and recycles the components of erythrocytes (red blood cells).
- Erythrocytes rupture after 120 days
- Kupffer cells in sinusoids of the liver
- Kupffer cells ingest erythrocytes
- Hemoglobin split into heme and globin groups
- Heme group broken down into iron and bilirubin
- Irons stored in liver / Bilirubin becomes part of bile
Outline the production of bile and the causes and consequences of jaundice.
- Erythrocytes broken down in liver
- Heme group converted to bilirubin
- Bilirubin transferred to bile and eliminated in feces
- Jaundice;
Caused: by blockage of bile ducts
Cons: liver does not excrete bilirubin, bilirubin accumulates in the blood
