Nutrition Chapter 3

ulcerative colitis

-A chronic inflammation of the large intestine, resulting in ulcers in the lining of the colon -Tends to run in families -Afflicts both men and women, beginning between the ages of 15 and 30 -There is no known cause or cure. -Treatment includes drug therapy and surgery

celiac disorder

-A genetic disorder that causes damage to the small intestine when foods containing gluten are consumed -Causes the small intestinal villi to flatten out, causing nutrient malabsorption -It is caused by an abnormal reaction to the protein gluten, found in rye, wheat, and barley. -Symptoms: Reoccurring abdominal bloating Cramping and/or gas Diarrhea Foul-smelling stools Weight loss anemia bone or joint pain

liver

-A major player in the digestion, absorption, and transport of nutrients -Is essential in carbohydrate metabolism -Produces proteins -Manufactures bile salts that are used to digest fats -Is the site of alcohol metabolism Removes and degrades toxins and excess hormones

chemical digestion aided by...

-Aided by digestive enzymes and other substances -Regulated by hormones -Completed by the time the food reaches the large intestine

pancreas

-Endocrine function—releases hormones to maintain blood glucose levels -Exocrine function—secretes digestive enzymes into the small intestine

heartburn (esophageal problem)

-The lower esophageal sphincter doesn't close properly, allowing HCl from the stomach to flow into the esophagus. -Chronic heartburn and stomach acid reflux are typical of gastroesophageal reflux disease (GERD). -Factors generally associated with GERD include: -Chocolate, fatty foods, coffee, soda, onions, garlic -Smoking, being overweight or obese, drinking alcohol, wearing tight-fitting clothing, eating large evening meals, reclining after eating -Dietary changes, behavior modification, antacids, prescription drugs, or surgery may help.

fluid absorption occurs in the large intestine

-The majority of nutrients have been absorbed when chyme enters the large intestine. -Water and salt are absorbed in the large intestine. -The same mechanisms used in the small intestine are also used in the large intestine. -Water — passive diffusion -Sodium — active transport

esophagus

-The only function of the esophagus is to transport food and fluids to the stomach. -There are two sphincters in the esophagus: -Upper esophageal sphincter: Allows the bolus of food to enter the esophagus -Lower esophageal sphincter (LES): Allows the bolus of food to enter the stomach

small intestine

-The small intestine consists of three segments: -Duodenum: 10 in long -Jejunum: 8 ft long -Ileum: 12 ft long -Mechanical and chemical digestion take place in the small intestine. -The surface of the small intestine is lined with villi, which help maximize absorption. -The contact time in the small intestine is 3-10 hours, depending on the food eaten.

three conditions must be present for enzymes to work

1.)The compatible enzyme and nutrient must both be present. -Enzymes are compatible only with a specific compound or nutrient (substrate). -Named according to the substrate they act upon, plus the suffix -ase -Example: Sucrase hydrolyzes sucrose 2.) The pH of the surrounding environment must fall within the correct range. -Enzymes are most active and efficient within a certain range of acidity and alkalinity. -Outside of that range the enzyme activity is decreased or halted. 3.)The temperature of the environment must be optimal. -Enzyme activity is slowed with too low a temperature and halted when the temperature is too high.

absorption

: The process of moving nutrients from the gastrointestinal (GI) tract into the circulatory system

organs of gastrointestinal tract

A 23-foot-long muscular tube comprised of the organs of the digestive tract Five organs make up the GI tract: Mouth Esophagus Stomach Small intestine Large intestine Sphincters allow food to pass from one organ to the next. Accessory organs outside the GI tract aid in digestion. They include the liver, pancreas, and gallbladder.

mechanical digestion

Breaking down food through chewing, grinding, squeezing, and moving food through the GI tract by peristalsis and segmentation

chemical digestion

Breaking down food through enzymatic reactions

Gastric inhibitory peptide (GIP)

Inhibits gastric motility and stomach secretions

gastrin

Stimulates HCl production and the release of gastric enzymes

secretin

Stimulates the pancreas to release bicarbonate to the small intestine; pH is raised

Cholecystokinin (CCK)

Stimulates the pancreas to release lipase and the gallbladder to release bile; slows down gastric motility

elimination

The excretion of undigested and unabsorbed food through the feces

transport

The process of moving absorbed nutrients throughout the body through the circulatory and lymph systems

digestion

process of breaking down food into individual moleules small enough to be absorbe through the intestinal wall

ulcers

-A sore or erosion in the lining of the lower region of the stomach or upper part of the duodenum -Helicobacter pylori, a bacterium, is often involved in the creation of ulcers. -Common symptoms are vomiting, fatigue, bleeding, general weakness, and burning pain. -Treatment can include prescription drugs, dietary changes, and/or surgery. -An untreated ulcer can result in peritonitis, scar tissue that can obstruct food and cause vomiting and weight loss, and greater risk for stomach cancer.

enzymes

-Enzymes are proteins that drive the process of digestion. -They catalyze (or speed up) hydrolysis, the chemical reaction that uses water to split chemical bonds of digested foods. -Three conditions must be present for enzymes to work:

celiac disease 2

-How serious is celiac disease? -Increased risk for osteoporosis, diminished growth, seizures -Diagnosis is made with a blood test and tissue biopsy of the small intestine. -How is it treated? -Follow a gluten-free diet. -Eliminate all foods that contain wheat. -Include: milk, meat, eggs, fruits, vegetables, rice, potatoes, beans, millet, amaranth -Moderate amounts of oats (up to ¼ c) may be tolerated.

constipation

-Infrequent passage of dry, hardened stools -Often due to insufficient fiber or water intake -Exercise, normal eating patterns, and proper rest can help resolve constipation. -Laxatives should be used sparingly, as they can cause dehydration, salt imbalances, and laxative dependency. -Colon cleansing (enema) is not recommended as a treatment.

flatulence

-Intestinal gas, which needs to be released 10 to 20 times a day -Caused by: -Foods high in fiber and starch -Eating quickly -Drinking carbonated beverages -Lack of exercise -Smoking

nervous system

-Lets you know when you need to eat and drink, and when to stop -Extrinsic nerves: communicate changes in the GI tract and stimulate motility. -Intrinsic nerves: receive the message from the extrinsic nerves and respond by stimulating the release of digestive juices. -Hormones work with nerves to communicate feelings of hunger and fullness. -Ghrelin — hormone of hunger -Peptide YY — signals that you have eaten or are full

large intestine cont'd

-Bacteria in the colon ferment some undigested and unabsorbed carbohydrates into simpler compounds, methane gas, carbon dioxide, and hydrogen. -Fermented fiber produces short-chain fatty acids. -In the large intestine, 1 liter of fluid material is gradually reduced to 200 grams of brown fecal material. -The intestinal matter passes through the large intestine in 12-70 hours, depending on the person's health, age, diet, and fiber intake.

irritable bowel syndrome (IBS)

-Changes in colon rhythm -Those with IBS experience an overresponse to colon stimuli, resulting in alternating patterns of diarrhea, constipation, and abdominal pain. -The exact cause is not known. -Treatment includes increased dietary fiber, stress management, and prescription drugs.

gallbladder disease

-Diagnosed most frequently in women and older Americans -Obesity and rapid weight loss are contributing factors. -An unhealthy gallbladder can create gallstones. -Stones are formed from cholesterol in the gallbladder or bile duct. -Treatment includes surgery for gallbladder removal, prescription medication, shock-wave therapy, or a combination of therapies. -The body eventually adapts to the removal of the gallbladder by secreting bile directly into the duodenum.

belching

-Generally caused by swallowing amounts of air -Usually happens as a result of eating too fast, drinking carbonated beverages, or anxiety -Can also occur without any act of swallowing

hormones in the GI tract

-Hormones regulate digestion by controlling -The release of gastric and pancreatic secretions -Peristalsis -Enzyme activity -Enterogastrones are produced and secreted by the cells lining the stomach and small intestine. -They influence GI motility, stomach emptying, gallbladder contraction, intestinal absorption, and hunger. -Release of hormones is stimulated by the types of food passing through the digestive tract.

how do hormones and the nervous system regulate digestion?

-The endocrine and nervous systems work together to coordinate digestion, absorption, and excretion of waste products. -Digestion runs smoothly when the endocrine system communicates with the nervous systems built into the GI tract. -Digestion is also controlled by the enteric nervous system, a meshwork of nerve fibers that innervate the GI tract, pancreas, and gallbladder. -The enteric nerves monitor stomach contractions after eating and the secretions of the cells in the GI tract.

how are nutrients transported throughout the body?

-Nutrients are absorbed into the bloodstream or lymphatic system. -Water-soluble nutrients are absorbed into the cardiovascular system through the hepatic portal vein to the liver. -Carbohydrates, amino acids, and water-soluble vitamins -Fat-soluble nutrients are absorbed into the lymphatic system. -Fat-soluble vitamins, long-chain fatty acids, and proteins are too large to be transported via the capillaries. -The waste products that remain after nutrient absorption are removed by the excretory system. -The kidneys filter the blood, allowing waste products to be concentrated in the urine and excreted.

majority of absorption takes place in the small intestine

-Passive diffusion: Nutrients move from high concentration to low concentration; no energy is required. -Facilitated diffusion: Nutrients move from high concentration to low concentration with the help of a carrier protein; no energy is required. -Active transport: Nutrients move from low concentration to high concentration with the help of a carrier protein; energy is required. -Endocytosis: Cell forms a vesicle to surround and engulf a nutrient.

gallbladder

-Receives bile from the liver via common hepatic duct -Concentrates bile -Releases bile into small intestine via common bile duct

Crohn's disease

-Similar to ulcerative colitis, but ulcers can occur throughout the GI tract -There is no known cause or cure. -Treatment includes drug therapy and possibly surgery.

large intestine cont'd again (anus)

-Stool is propelled through the large intestine until it reaches the rectum, the 8-inch portion of the large intestine. -The anus is the opening of the rectum, or end of the GI tract. -The final stage of defecation is under voluntary control. -It is also influenced by age, diet, prescription medications, health, and abdominal muscle tone.

hemorrhoids

-Swelling of the veins of the rectum and anus -Can lead to bleeding, itching, and/or pain -The cause is unknown. Contributing factors include straining to pass dry stools, pregnancy, constant constipation or diarrhea, and aging. -Treatment includes increased dietary fiber and fluid intake. -Some symptoms (itching and pain) can be relieved through use of creams, ice packs, and soaking in a warm bath. -Severe cases may require surgery.

gastroenteritis (stomach flu)

-Symptoms can include nausea, vomiting, diarrhea, and abdominal cramping. -Treat symptoms through rest, rehydration, and eating soft foods. -Foodborne illness: Consuming food or drink contaminated with a pathogenic microbe can cause vomiting, abdominal cramps, diarrhea, and fever. -Most are self-limiting and require rest and rehydration.

Diarrhea

-The passage of watery, loose stools more than three times a day -Generally the result of bacterial, viral, or parasitic infections that cause food and fluids to pass too quickly through the colon -Chronic diarrhea may be the sign of a more serious problem. -Untreated diarrhea can lead to malnutrition. -Diarrhea can lead to dehydration and potentially death, particularly in children and the elderly. -Treated with fluid and electrolyte replacement

stomach

-The stomach mixes food with various gastric juices to chemically break it down into smaller pieces. -Mechanical digestion occurs in the stomach as the muscles of the stomach mix, churn, and push the contents with gastric juices. -Chyme is the semiliquid, partially digested food mass that leaves the stomach and enters the small intestine. -Approximately 1 tsp of chyme leaves the stomach and enters the small intestine every 30 seconds. -The pyloric sphincter is the gateway for chyme to enter the small intestine from the stomach. -stomach - fundis - outer layer, pylori - lower half, cardiac - upper half

colon cancer

-The third-leading cause of cancer death -One of the most curable cancers if detected early -It begins with polyps on the lining of the colon that are often small, benign, and can be surgically removed. -Polyps can develop into cancerous tumors if not detected early. -Treatment includes radiation, chemotherapy, or surgery. -Survival rates vary depending on age, treatment response, and stage of cancer diagnosis.

esophageal cancer

-This is one of the most common cancers of the digestive tract. -Sufferers are typically males over age 50 living in urban areas who smoke and drink heavily. -Treatment can include surgery, radiation, and chemotherapy

large intestine

-absorbs water and some nutrients -Chyme enters the large intestine through the ileocecal valve. -Large intestine has three segments: -Cecum -Colon -Rectum -Site of water, sodium, potassium, and chloride absorption -Bacteria produce vitamin K, thiamin, riboflavin, biotin, and vitamin B12. -Only biotin and vitamin K can be absorbed.

digestion begins in the mouth

-mechanical and chemical digestion take place in mouth -saliva -Dissolves small food particles -Contains the enzyme amylase, which begins to break down carbohydrate -In adults no other chemical digestion takes place in the mouth Once food has been adequately chewed and moistened, the tongue rolls it into a bolus and it enters the pharynx to be swallowed.

simple diffusion

-moving nutrients from high concentration to a lower concentration

active transport

-requires ATP, goes against the energy gradient, low to high concentration

segmentation

-shifts food back and forth along the GI tract in the intestines and adds chemical secretions -allows contact with surface of small and large intestines and increases absorption

peristalsis

-squeezes food forward through the GI tract -mechanical digestion

facilitated diffusion

-transport and channel proteins, nutrient passes through channel protein