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Flashcards in Digestion Deck (38)
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Define non-essential nutrient. What are some examples?

-A nutrient replaceable with another for the same purpose or because they can be synthesized by the body from another nutrient.
-Glucose, starch, and other carbohydrates are non-essential nutrients.


What is the chemical nature of minerals? Explain iodine as an essential mineral.

-Minerals can be distinguished from vitamins by their chemical nature; minerals are chemical elements, usually in ionic form.
-Iodine is needed by the thyroid gland for synthesis of the hormone thyroxin. Thyroxin stimulates metabolic rate and ensures energy release is adequate. Thus, without iodine, the metabolism slows and there is insufficient energy released.


What are vitamins? List three roles of vitamins.

-Chemically diverse carbon compounds which cannot be synthesized by the body.
-Vitamins act as co-factors for enzymes, anti-oxidants, and hormones.


How many of the amino acids are essential and what occurs if there is a shortage of these essential amino acids? What are two essential fatty acids?

-9 of the amino acids are essential. Insufficient amounts of them result in poor human development and upkeep.
-Omega-3 and Omega-6 are necessary fatty acids in the development of the brain and eye and cannot be synthesized by the body.


How is appetite controlled?

-Hypothalamus of the brain is responsible for the feeling of satiation.
-Small intestine release hormone PYY3-36 when it contains food. Pancreas secretes insulin when the blood glucose concentration is too high. Adipose tissue secretes the hormone leptin when fat storage increases.
-The hypothalamus receives these proteins and reduces the desire to eat.


Why does starvation lead to breakdown of body tissue?

-Absence of dietary intake of energy sources-> body accesses glycogen storage.
-When no glucose available, body breaks down muscle tissue to use resulting amino acids for energy-> amino acids sent to liver to be converted to glucose and so muscles lose mass from amino acids.


Why is digestion necessary? Why are enzymes necessary in digestion?

-Digestion is necessary as it allows for absorption of materials.
-Enzymes are necessary as they catalyze reactions breaking down food to make digestion easier by lowering the activation energy of these reactions.


What is the alimentary canal? What organs are not part of the alimentary canal but are connected by ducts?

The alimentary canal is the passage along which food passes through the body from mouth to anus. The pancreas, liver, and gall bladder are connected by ducts.


What is the mouth's role in the digestive system?

-Food enters.
-Mechanical digestion via mastication.
-Salivary amylase breaks down starches with saliva and mucous.


What is the esophagus' role in digestion?

Peristalsis from mouth to stomach


What is the role of the stomach in digestion?

-Mechanical digestion by churning.
-Produces pepsinogen which turns into pepsin by HCl which together break down peptides. Mucous protects stomach from HCl.


What is the role of the gall bladder in digestion?

Storage and regulated release of bile


What is the role of the pancreas in digestion?

Produces trypsin open, lipase, pancreatic amylase, maltose.


What is the role of the liver in digestion?

-Secretion of surfactants in bile to break up lipid droplets.
-Synthesis of bile.


What is the role of the small intestine in digestion?

-Absorption of nutrients.
-Trypsinogen converted into trypsin which breaks down peptides further.
-Lipase, pancreatic amylase, maltase used to break down lipids, amylose, and maltose into digestible nutrients.
-Bile salt used to maintain pH.


What is the role of the large intestine in digestion?

-Reabsorption of water and some further absorption of ions and other nutrients.
-Formation of egest into feces in the rectum.
-Egestion of waste products via anus.


How is smooth muscle different from striated muscle?

-Smooth muscle is made up of relatively short cells, not elongated fibers.
-They perform small, low-level continuous work.


Describe the two types of smooth muscle found in the intestines.

-Circular muscles behind food contracts to prevent food being pushed up.
-Longitudinal muscles where food is located moves it along the gut.


What are essential nutrients? What are some essential nutrients?

-Essential nutrients are those nutrients which cannot be synthesize by the body and thus must be included in one's diet.
-Amino acids, some unsaturated fatty acids, some minerals, calcium, vitamins, and water are some essential nutrients.


Define peristalsis.

The involuntary constriction and relaxation of the muscles of the intestine or another canal, creating wave-like movements that push the contents of the canal forward.


In what order from the lumen outwards do the tissue layers go?

Lumen-> villi-> mucosa-> sub-mucosa-> circular muscle-> longitudinal muscle-> serosa


What is the function of the pancreas?

-Secretes insulin and glucagon into the blood.
-Secretes enzymes into the lumen of the small intestine.
-Synthesizes hormones.


What happens to cellulose in digestion?

Passes onto the large intestine as one of the main components of dietary fiber.


What types of materials are absorbed into the intestinal villi?

Monosaccharides, amino acids, fatty acids, nucleotide bases, mineral ions, vitamins.


What is a lipoprotein? How is it formed?

Group of soluble proteins that combine with and transport fat or other lipids in the blood plasma. It is formed by the coalescence of triglycerides with cholesterol and are coated in phospholipids and proteins.


Where does excess glucose end up?

Stored as glycogen in the liver.


How are the nervous system and hormones used in controlling the volume and content of gastric juices?

-Sight or smell of food causes the brain to send nerve impulses via the vagus nerve from the medulla. Gland cells in the stomach are stimulated to secrete components of gastric juice.
-If chemoreceptors detect peptides or stretch receptors detect stomach dissension, impulses are sent to the brain which then sends messages to the endocrine cells of the duodenum, telling them to secrete gastrin, secretin and somatostatin.


What is the role of gastrin?

Stimulates secretion of gastric acid and pepsinogen by two types of exocrine gland cells in the stomach wall.


What is the role of secretin and somatostatin?

Inhibit gastrin secretion if stomach pH falls too low.


Distinguish between endocrine and exocrine glands.

-Endocrine glands secrete directly into the bloodstream.
-Exocrine glands secrete into ducts.


Define ductules, secretory cells, secretory vesicles, acini.

-Ductules are minute ducts.
-Secretory cells are pancreatic cells which prude necessary enzymes and hormones
-Secretory vesicles secrete enzymes and hormones into the lumen
-Acini are collections of secretory cells which form pancreatic ducts.


What do exocrine cells contain a lot of?

-Extensive rER for enzyme synthesis.
-Many mitochondria to produce ATP for protein synthesis and other activities.
-Many vesicles necessary for transport of zymogen particles.


Explain the role of acid in the stomach.

-HCl secreted by parietal cells of the stomach.
-HCl disrupts the extracellular matrix that holds cells together in tissues. Leads to denaturing of proteins, exposing the polypeptide chains.
-Pepsin released as inactive pepsinogen by chief cells so that secretory cells are not digested.
-Pepsinogen broken down into active pepsin by HCl.
-Pepsin hydrolysis the bonds of polypeptides, breaking down the food in the stomach.


What is the function of villi, the blood capillary, the lacteal?

-Villi increase the surface area for absorption in the small intestine.
-The blood capillary absorbs nutrients from the lumen and takes them into the bloodstream
-Lacteal is a duct at the villain center which conducts fats away from the villus after absorption into the lymphatic system.


What are adaptations of the villi?

-Epithelium is one cell thick for short diffusion of molecules from lumen into the blood
-Many mitochondria to provide the relatively high amounts of ATP necessary for active transport
-Microvilli increase the surface area for absorption even furthermore
-Protein channels in Microvilli to facilitate active transport
-Tight junctions which knot the epithelial cells together, preventing presence of interstitial spaces such that nutrients can't move across epithelial cells.


What is a stomach ulcer? What causes it?

-Open sores on the stomach
-Caused by colonies of bacterium that attack the lining of the stomach, allowing gastric acid to escape and causes the sores.


What materials are egested?

-Dietary fiber
-Digested red blood cells


Outline the role of dietary fiber?

-Faster rate of transit through the large intestine
-Reduces risk of cancer, hemorrhoids, and appendicitis
-Slows sugar uptake