SC 1332 Study Guide Exam 2 Fall 2009

Chapter 17: the digestive system.

Introduction.
Digestion is the process of mechanically and chemically breaking down food so that they can become absorbed.
The digestive system consists of an elementary canal and several accessory organs that carry out the processes of digestion, propulsion, digestion, absorption, and defecation.

Gen. Characteristics of the elementary canal.
The wall the elementary tract consists of four layers.
The four layers of the elementary tract include mucosa, submucosa, muscular layer and the serosa.
Peristalsis is responsible for propelling movements.
The wall of the tube undergoes receptive relaxation just ahead of the peristaltic wave.
The tube is innervated by branches of the sympathetic and parasympathetic divisions of the autonomic nervous system.
Parasympathetic impulses generally increase digestive activities.
Sympathetic impulses generally inhibit digestive activities.
Sympathetic impulses contract certain sphincter muscles, controlling movements through the elementary canal.

The mouth.
The mouth is adapted to receive food and begin preparing it for digestion.
The mouth serves as an organ of speech and sensory perception.
Tonsils consists of lymphatic tissues.
Keith mechanically break food into smaller pieces, increasing the surface area exposed to digestive actions.

Salivary glands.
Salivary glands secrete saliva, which moistens food, helps bind food particles, begins chemical digestion of carbohydrates, makes taste possible, helps clean the mouth, and regulates pH in the mouth.
Salivary glands include cells that secrete digestive enzymes and mucus cells that secrete mucus.
Parasympathetic impulses stimulate the secretion of saliva.
The pharynx and the esophagus.

Swallowing occurs in three stages.
In phase 1 of swallowing food is mixed with saliva and forced into the pharynx.
In phase 2 of swallowing involuntary reflex actions move the food into the esophagus.
In stage III of swallowing peristalsis transports food to the stomach.
Swallowing reflexes momentarily inhibit breathing.
Circular muscle fibers in the distal end of the esophagus help prevent regurgitation of food from the stomach.

The stomach.
The lower esophageal sphincter serves as a valve between the esophagus and the stomach.
The pyloric sphincter serves as a valve between the stomach and small intestine.
Parasympathetic impulses and the hormone gastrin enhanced gastric secretion.

The three stages of gastric secretion are the cephalic, gastric and intestinal phases.
The presence of food in the small intestine reflexively inhibits gastrin secretions.
The stomach is not well adapted for absorption.
Mixing movements of the stomach aid in the production of chyme.
Peristaltic waves move chyme into the pyloric region.
The muscular wall of the pyloric region regulates chyme movements into the small intestine.
The rate of emptying depends on the fluidity of the chyme and the type of food present.
The upper part of the small intestine fills and then an enterogastric reflex inhibits peristalsis in the stomach.
Gastric goblet cells secrete mucus into the gastric lumen.
Parietal cells secrete intrinsic factor to aid in the absorption of vitamin B12.
Parietal cells secrete hydrochloric acid to aid in the digestion of proteins.
Chief cells secrete pepsinogen which is a precursor to pepsin.
Hydrochloric acid converts pepsinogen to pepsin.
Pepsin is a proteins splitting enzymes that digest nearly all types of dietary protein.
Gastrin increases secretory activity of gastric glands.
Somatostatin inhibit secretion of acid by parietal cells.
Cholecystokinin decreases secretory activity of gastric glands and inhibits gastric motility.

Pancreas.
Pancreatic juice contains enzymes that can split carbohydrates, proteins, fats, and nucleic acids.
Pancreatic juice has a high bicarbonate ion concentration that helps neutralize chyme and causes the intestinal contents to be alkaline.
Secretin from the duodenum stimulates the release of pancreatic juice that contains a few digestive enzymes but has a high bicarbonate ion concentration.
Cholecystokinin from the intestinal wall stimulates the release of pancreatic juice that contains a high concentration of digestive enzymes.

Liver.
The liver is a highly vascular organ enclosed a fibers capsule and divided into lobes.
Each lobe consists of hepatic lobules, the functional units of the liver.
Bile is the only liver secretion that directly affects digestion.
Bile pigments are products of red blood cell breakdown.
The gallbladder stores bile between meals.
Cholecystokinin from the small intestine stimulates bile release.
Bile salts emulsify fats and aid in the absorption of fatty acids, cholesterol, and certain vitamins.
Bile salts are reabsorbed in the small intestine.
Small intestine.
The small intestine extends from the pyloric sphincter to the large intestine.
The small intestine consists of the duodenum, jejunum and ileum.
The intestinal wall is lined with villi that greatly increase the surface area and aid in mixing and absorption.
Microvilli on the free ends of epithelial cells increase the surface area even more.
Intestinal glands are located between the villi.
Digestive enzymes embedded in the surfaces of the microvilli, split molecules of sugars, proteins, and fats.
Secretion is stimulated by gastric juice, chyme, and reflexes stimulated by distention of the small intestinal wall.
Blood capillaries in villi absorbed monosaccharides, amino acids, small chain fatty acids and glycerol.
Blood capillaries in villi also absorb water and electrolytes.
Fat molecules with larger chains of carbon atoms enter the lacteals of the villi.
Fatty acids with short carbon chains into the blood capillaries of the villi.
Over distention or irritation of the intestinal lining may stimulate a peristaltic rush and result in diarrhea.
The ileocecal sphincter controls movements of the intestinal contents from the small intestine into the large intestine.

Large intestine.
The large intestinal wall resembles the wall in other parts of the elementary canal.
The large intestine has little or no digestive function although it secretes mucus.
Mechanical stimulation and parasympathetic impulses control the rate of mucus secretion in the large intestine.
The large intestine absorbs water and electrolytes.
Many bacteria inhabit the large intestine, where the breakdown some on digestible substances, such as cellulose, and synthesize vitamins K., B12, thiamine, and riboflavin.
The large intestine forms and stores feces.
Feces consists of water, undigested material, mucus, and bacteria.
The color of feces is due to bile pigments that have been altered by bacterial action.

Diagram labeling.
Please be prepared to label the following: figure 17.3 which is found on page 667 of your textbook.
Please be prepared to label the following: figure 17.7 which can be found on page 671 of your textbook.
Please be prepared to label the following: figure 17.10 which is found on page 672 of your textbook.
Please be prepared to label the following: figure 17.20 which is found on page 682 of your textbook.
Please be prepared to label the following: figure 17.22 which is found on page 684 of your textbook.
Please be prepared to label the following: figure 17.24 which is found on page 686 of your textbook.
Please be prepared to label the following: figure 17.30 which is found on page 693 of your textbook.
Please be prepared to label the following: figure 17.35 which is found on page 696 of your textbook.

Chapter 18: nutrition and metabolism.

Why we eat.
Nutrients include carbohydrates, lipids, proteins, vitamins, and minerals.
Essential nutrients are required for health, and body cells cannot synthesize them.
Macronutrients include carbohydrates, lipids, and proteins.
Micronutrients are vitamins and minerals.

Water is also essential.
Hormones communicate from the gastrointestinal tract the hypothalamus to control appetite, and monitor fat stores.

Carbohydrates.
Polysaccharides, disaccharides, and monosaccharides are carbohydrates.
Cellulose is a polysaccharide human enzymes cannot digest.
Cellulose provides bulk that facilitates movement of intestinal contents.
Carbohydrates are absorbed as monosaccharides.
Enzymes in the liver catalyze reactions that convert fructose and galactose into glucose.
Oxidation releases energy from glucose.
Excess glucose is stored as glycogen or combined to produce fat.
Most carbohydrates supply energy.
Some carbohydrates are used to produce sugars.
Some cells require a continuous supply of glucose to survive.
If glucose is scarce, amino acids may react to produce glucose.
Glucose is blood sugar.
Glucose + Glucose = Maltose
Glucose + Fructose = Sucrose
Glucose + Galactose = Lactose
Lactase enzymatically separates lactose into glucose and galactose.
Maltase enzymatically separates maltose into 2 glucose molecules.
Sucrase enzymatically separates sucrose into glucose and fructose.

Lipids.
Lipids are organic compounds that supply energy and are used to build cell structures.
Cholesterol is mostly obtained and foods of animal origin.
Before fats can be used as energy sources, they must be broken down into glycerol and fatty acids.
Beta oxidation activates fatty acids and breaks them down into segments of two carbon atoms each.
Fatty acid segments are converted into acetyl CoA, which can then be oxidized in the citric acid cycle.
The liver regulates cholesterol level by synthesizing or excreting it.
Fat intake must be sufficient to carry fat soluble vitamins.

Protiens.
Proteins proteins are organic compounds that serve as structural materials, active enzymes, and provide energy.
Amino acids are incorporated into various structural and functional proteins, including enzymes.
During starvation, tissue proteins may be used as energy sources.
In an during digestion, proteins are broken down into amino acids.
Before amino acids can be used as energy sources, they must be deaminated.
The deaminated portions of amino acids can be broken down into carbon dioxide and water or used to produce glucose or fat.
All essential amino acids must be present at the same time in order for growth and repair of tissues to take place.
In healthy adults, the gain of protein equals the loss of protein, and a nitrogen balance exists.

Energy expenditures.
Energy is of prime importance to survival.
Energy may be obtained from carbohydrates, fats, or proteins.
The potential energy values of food are expressed in calories.
The amount of energy required vary from person to person.
Factors that influence energy requirements include basal metabolic rate, muscular activity, body temperature, and nitrogen balance.
Energy balance exist when caloric intake equals caloric output.
If energy balance is positive, body weight increases.
If energy balance is negative, body weight decreases.

Vitamins.
Vitamins are organic compounds that are essential for normal metabolic processes and cannot be synthesized by body cells in adequate amounts.
Fat soluble vitamins are carried in lipids and are influenced by the same factors that affect lipid absorption.
Fat soluble vitamins are fairly resistant to the effects of heat.
Fat soluble vitamins are not destroyed by cooking or food processing.
Vitamin A is an antioxidant required for production of visual pigments.
Vitamin D is a group of steroids.
Vitamin D can be produced from cholesterol in the skin.
Vitamin E is a fat soluble antioxidant area
vitamin K is used to produce prothrombin, which is required for blood clotting.
Vitamins ADE and K are fat soluble vitamins.
Water soluble vitamins include the B vitamins and vitamins C.
Vitamin B1 is thiamine.
Thiamine functions as a part of coenzymes that oxidize carbohydrates and synthesize essential sugars.
Vitamin B2 is riboflavin.
Riboflavin functions as part of several enzymes & Co. enzymes are essential to the oxidation of glucose and fatty acids.
Vitamin B3 is niacin.
Niacin functions as part of co-enzymes required for the oxidation of glucose and for the synthesis of proteins and fats.
Niacin can be synthesized from tryptophan.
Vitamin B5 is pantothenic acid.
Pantothenic acid functions as part of CoA.
Thus pantothenic acid is essential for energy releasing mechanisms.
Vitamin B6 is pyridoxine.
Vitamin B6 a group of compounds that function as co-enzymes and metabolic pathways that synthesize proteins, certain amino acids, antibodies, and nucleic acids.
Vitamin B12 is cyanocobalamin.
The cyanocobalamin molecule contains cobalt.
Vitamin B12 absorption is regulated by the secretion of intrinsic factor from the parietal cells.
Folic acid is a set of co-enzymes needed for the metabolism of certain amino acids, DNA synthesis, and the normal production of red blood cells.
Biotin is a coenzyme required for metabolism amino acids and fatty acids, and for nucleic acid synthesis.
Vitamin C is ascorbic acid.
Vitamin C is required for collagen production, the metabolism of certain amino acids, and iron absorption, backspace.
Vitamin C is not stored in large amounts.
Excess vitamin C is excreted in the urine.

Minerals.
Minerals are responsible for about 4% of body weight.
About 75% by weight of the minerals are found in bones and teeth as calcium and phosphorus.
Minerals are usually incorporated into organic molecules.
Some minerals are found in inorganic compounds or is free ions.
Minerals composed structure or materials, function in enzymes, and play vital roles in various metabolic processes.
Homeostatic mechanisms regulate mineral concentrations.
The physiologically active form of minerals is the ionized form.
Calcium is essential for forming bones and teeth, conducting nerve impulses, contracting muscle fibers, flooding blood, and activating various enzymes.
Phosphorus is incorporated into the salts of bones and teeth.
Phosphorus is also in the phospholipids of cell membranes, ATP, and phosphates of body fluids.
Potassium is concentrated inside cells potassium maintain the osmotic pressure, regulates pH, metabolizes carbohydrates and proteins, conducts nerve impulses, and contracts muscle fibers.
Most sodium is in extracellular fluids or is bound to the inorganic salts of bone.
The kidneys, under the influence of aldosterone, regulate the blood concentration of sodium.
Sodium helps maintain water balance.
Sodium is essential for conducting nerve impulses, contracting muscle fibers, and moving substances through cell membranes.
Chlorine acts with sodium to help maintain osmotic pressure, regulate pH, and maintain electronic balance.
Magnesium is abundant in the bones as phosphates and carbonates.
Magnesium functions in ATP production.
Magnesium functions in the breakdown of ATP to ADP.
A reserve supply of magnesium is stored in the bones.
Excess magnesium is excreted in the urine.
Iron is part of hemoglobin in red blood cells in myoglobin muscles.
A reserve supply of iron is stored in the liver, spleen, and bone marrow.
Copper is required for hemoglobin synthesis, bone development, melanin production, and myelin formation.
Copper is important for the proper development of collagen fibers.
Iodine is most highly concentrated in the thyroid gland.
Iodine is an essential component of thyroid hormones.
Iodine is often added to foods as I organized table salt.
Fluorine is incorporated into enamel and prevents dental caries.
Chromium regulates glucose utilization.