Digestion

Question 1

Define non-essential nutrient. What are some examples?

Answer 1

• 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.

Question 2

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

Answer 2

• 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.

Question 3

What are vitamins? List three roles of vitamins.

Answer 3

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

Question 4

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?

Answer 4

• 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.

Question 5

How is appetite controlled?

Answer 5

• 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.

Question 6

Why does starvation lead to breakdown of body tissue?

Answer 6

• 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.

Question 7

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

Answer 7

• 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.

Question 8

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

Answer 8

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.

Question 9

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

Answer 9

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

Question 10

What is the esophagus’ role in digestion?

Answer 10

Peristalsis from mouth to stomach

Question 11

What is the role of the stomach in digestion?

Answer 11

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

Question 12

What is the role of the gall bladder in digestion?

Answer 12

Storage and regulated release of bile

Question 13

What is the role of the pancreas in digestion?

Answer 13

Produces trypsin open, lipase, pancreatic amylase, maltose.

Question 14

What is the role of the liver in digestion?

Answer 14

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

Question 15

What is the role of the small intestine in digestion?

Answer 15

• 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.

Question 16

What is the role of the large intestine in digestion?

Answer 16

• 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.

Question 17

How is smooth muscle different from striated muscle?

Answer 17

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

Question 18

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

Answer 18

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

Question 19

What are essential nutrients? What are some essential nutrients?

Answer 19

• 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.

Question 20

Define peristalsis.

Answer 20

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.

Question 21

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

Answer 21

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

Question 22

What is the function of the pancreas?

Answer 22

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

Question 23

What happens to cellulose in digestion?

Answer 23

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

Question 24

What types of materials are absorbed into the intestinal villi?

Answer 24

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

Question 25

What is a lipoprotein? How is it formed?

Answer 25

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.

Question 26

Where does excess glucose end up?

Answer 26

Stored as glycogen in the liver.

Question 27

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

Answer 27

• 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.

Question 28

What is the role of gastrin?

Answer 28

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

Question 29

What is the role of secretin and somatostatin?

Answer 29

Inhibit gastrin secretion if stomach pH falls too low.

Question 30

Distinguish between endocrine and exocrine glands.

Answer 30

• Endocrine glands secrete directly into the bloodstream.

- Exocrine glands secrete into ducts.

Question 31

Define ductules, secretory cells, secretory vesicles, acini.

Answer 31

• 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.

Question 32

What do exocrine cells contain a lot of?

Answer 32

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

Question 33

Explain the role of acid in the stomach.

Answer 33

• 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.

Question 34

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

Answer 34

• 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.

Question 35

What are adaptations of the villi?

Answer 35

• 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.

Question 36

What is a stomach ulcer? What causes it?

Answer 36

• 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.

Question 37

What materials are egested?

Answer 37

• Dietary fiber
• Digested red blood cells
• Water

Question 38

Outline the role of dietary fiber?

Answer 38

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