Download Study guide ch 22 digestion

Study Guide Chapter 22
1. Know the components of the human alimentary canal in sequence.
2. Describe mechanical and chemical digestion that takes place in the human digestive system.
a. Mechanical digestion: the physical breakdown of food by the chewing of food in the
mouth with the aid of the teeth and the churning of the stomach.
b. Chemical digestion: hydrolysis reactions and digestive enzymes that breakdown food
i. Enzymes that break down carbohydrates into simple sugars (e.g. amylase
breaks down starch)
ii. Proteases – enzymes (e.g. pepsin) that break down proteins into amino acids
iii. Lipases – enzymes that break down fats into glycerol & fatty acids after their
emulsification with bile (which breaks down fat globules into droplets)
3. What are these biological food molecules ultimately broken down into at the end of digestion?
a. Carbohydrates: polysaccharides into simple sugars
b. Proteins into amino acids
c. Fats/oils into glycerol and fatty acids
4. Define/explain peristalsis in relation to the human alimentary canal.
5. Oral cavity (mouth): Food is ingested; it is mechanically broken down by teeth and chemically
broken down by amylase; it includes the teeth, tongue and saliva produced by salivary glands.
6. What does saliva contain and what are its functions?
a. Saliva consists of mainly water with slippery glycoproteins (mucins) secreted from 3
pairs of salivary glands.
b. It softens & lubricates food for swallowing; protects the lining of the mouth
c. Amylase begins chemical breakdown of starch.
d. Has bacteria killing enzymes and antibodies that protects mouth from infection
7. What is the function of the tongue? It tastes food, shapes it into a ball and pushes it to the
back of the mouth (which triggers the swallowing reflex)
8. What is the pharynx? Common muscular cavity for food and air; connects oral cavity to the
esophagus and to the larynx (respiratory pathway to lungs).
9. What is the role of the epiglottis? A flap of cartilage that blocks off the respiratory passage to
the larynx when one is swallowing. The swallowing reflex elevates the larynx, so it meets the
epiglottis and directs food to the esophagus.
10. What is the esophagus? A long muscular tube that propels food to the stomach via peristalsis;
secretes mucus to protect itself from abrasion and lubricates food during its passage.
11. Know about esophageal sphincters and the pyloric sphincter. They are rings of circular
muscle that surround the esophagus at the top and at the bottom (lower esophageal sphincter
or LES); also at the lower end of the stomach (pyloric sphincter).
a. The lower esophageal sphincter controls the passage of food into the stomach. It also
keeps food and stomach acids from sloshing up into the esophagus.
b. The pyloric sphincter controls the passage of food out of the stomach into the small
intestine.
12. What is the stomach? An expandable muscular sac, which mechanically (by churning) and
chemically breaks down food& water (2L); stores and gradually releases food into the small
intestine; peristaltic waves moves food through the stomach and into the small intestine (2-6
hours to empty after a meal); also there is some absorption of water and alcohol into the
bloodstream.
13. How is food mechanically broken down in the stomach? Muscular walls of smooth muscle
produce churning contractions that disrupt large pieces of food bolus.
14. How is food chemically broken down in the stomach? Gastric glands secrete gastric juice, which
contains:
a. HCL: produces a highly acidic stomach pH (pH 2); the acidic pH opens cells & kills
microbes.
b. Pepsinogen is secreted and is converted to its active form, pepsin, by the acidic pH;
pepsin is a protease (a protein digesting enzyme) that breaks proteins into peptides &
amino acids
c. Mucus: is secreted to lubricate & protect stomach cells from self-digestion
15. Chyme: a thick acidic liquid composed of partially digested food and digestive secretions
produced in the stomach and transported to the small intestine
16. What is the small intestine? A long (20 ft) coiled, narrow tube (2.5 cm) with a large surface
area & it is the major organ where chemical food digestion and nutrient absorption into the
bloodstream occurs. The first part, the duodenum, is where most chemical digestion occurs.
a. Completes carbohydrate digestion into simple sugars
b. Completes protein digestion into amino acids
c. Fat digestion via bile (fat emulsifier) and lipases (fat digesting enzymes)
17. The small intestine receives digestive secretions that aid in the digestion of chyme from. In
response to chyme, hormones produced by the duodenum stimulate release of bile from the
liver and digestive juices from the pancreas.
a. Liver and gall bladder – the liver makes bile (an emulsifier of fats; aids in fat
digestion), which it stores & concentrates in the gall bladder.
b. Pancreas – provides pancreatic juice: sodium bicarbonate buffers or neutralizes the
acidic chyme in the small intestine; pancreatic amylase (starch digestion); pancreatic
lipases (lipid digestion); and pancreatic proteases (protein digestion)
c. Also note: Epithelial cells that line the intestinal wall have digestive enzymes
embedded in their plasma membranes or they are secreted into the lumen; they
complete digestion into monomers
i. Peptidases- break protein peptides into amino acids
ii. Disaccharides- break disaccharides into monosaccharides or simple sugars
18. Where does most chemical digestion occur in the small intestines? Duodenum (the first part of
the small intestine).
19. What about the structure of the small intestine facilitates nutrient absorption? Describe the
process.
a. Nutrient absorption is facilitated by an increased surface area produced by folds in the
intestinal lining and the finger-like projections (called villi) that carpet the folds. In
addition the individual epithelial cells (on the surface of villi) have microvilli, which
also increases the surface area for nutrient absorption.
b. Each villus has an associated blood supply of capillaries and single lymph lacteal
(lymphatic vessel), providing a means for nutrients to enter the bloodstream.
c. Once nutrients cross the plasma membranes of microvilli, they are now inside the body
where the blood stream and lymph (fluid in lymphatic vessels) carry them away to
distant cells.
20. How do lipid monomers enter the blood stream? While most nutrients enter via blood
capillaries, lipid components do not. Once the breakdown products of fat diffuse into the cell
lining of the intestinal wall, they are converted into chylomicron particles (resynthesized fats
coated with proteins), which are exported out of the basal ends of the epithelial cells and the
move into the lymphatic lacteal. The chylomicron travel within the lymphatic system, which
eventually enters the circulatory system through the thoracic duct.
21. What is the structure of the large intestine? A shorter (5 ft), but wider (5 cm) coiled tube than
the small intestine that consists of the colon (most of the large intestine) and the rectum (the
final 6 inches) that leads to the anus (opening from which feces is eliminated)
22. What is the function of the colon?
a. It receives the digestive leftovers (mixture of water, minerals, indigestible fiber, and
small amounts of unabsorbed protein and fat) from the small intestine.
b. The cell wall of the colon absorbs vitamins produced by bacteria that flourish there,
water and minerals.
c. The colon concentrates the remaining material (mostly indigestible wastes) into-semisolid feces (which will be eliminated)
d. The colon then transports the waste to the rectum where it is stored until it is eliminated
(defecation) from the anus.
23. Why is proper nutrition important?
a. It provides fuel (energy) for cellular work; carbohydrates, lipids (fats) and protein can
all be broken down through cellular respiration to make ATP.
b. The monomers of the foods we eat (amino acids, simple sugars, fatty acids and glycerol)
can be used to build organic molecules that the body needs [they provide the materials
for building molecules].
c. There are some substances that the body needs for its proper function (nutrients) that it
can’t make itself from other molecules (essential); these substances are essential
nutrients, meaning that we need to get them from our diet
24. Describe the essential nutrients. (I may give you specific examples on the quick review)
a. Essential amino acids – 8 of them (required for protein production)
b. Vitamins – essential organic molecules needed in very small amounts for normal
growth and development; water-soluble and lipid soluble types
c. Minerals – essential chemical elements from inorganic compounds (e.g. Calcium for
bone and tooth formation, muscle contraction and nerve impulse transmission)
d. Essential fatty acids – are required to produce lipids the body needs.