Nutrition Chapter 3
Large Intestine: Appendix
(a blind sac about the size of your little finger) located that the beginning of the large intestine.
Large Intestine: Lleocecal Valve
(another sphincter muscle) is located at the beginning of the large intestine.
Mouth: Bolus
A bolus is a portion; with respect to food the amount swallowed at one time. Bolos = lump
Secretions of Digestion: Hydrolysis
A chemical reaction in which one molecule is split into two molecules, with hydrogen (H) added to one and a hydroxyl group (OH) to the other (from water, H2O) hydro = water lysis = breaking
Catalyst
A compound that facilitates chemical reactions without itself being changed in the process.
Gastrointestinal (GI) Tract
A flexible muscular tube that extends from the mouth, through the esophagus, stomach, small intestine, large intestine, and rectum to the anus.
Secretions of Digestion:
A neutral pH is 7, bile and pancreatic juice are more basic (alkaline) than acidic, and gastric juice is very acidic.
Dehydration
A person with chronic diarrhea or excessive vomiting is at risk for dehydration.
Mouth: Pharynx
A short tube that is shared by both the digestive system and the respiratory system.
The enormous surface of the small intestine facilitates nutrient absorption. Nutrients can be absorbed through:
Active Transport- requires energy to move substances across a cell membrane (glucose and amino acids).
Large Intestine:
Also called the colon.
Carbohydrase
An enzyme that hydrolyzes carbohydrates.
Lipase
An enzyme that hydrolyzes lipids.
Protease
An enzyme that hydrolyzes proteins.
Mouth: What affects a food's flavor
Aroma, appearance, texture, and temperature also affect a food's flavor.
Large Intestine:
As the intestinal contents pass to the rectum, the colon withdraws water, leaving semisolid waste. The rectum muscle acts as a safety device along with the two sphincters of the anus.
Small Intestine:
At the beginning of the small intestine the chyme bypasses the opening from the common bile duct, which is dripping fluid from two organs outside the GI tract, the pancreas and the gallbladder. Chyme pass through 3 segments of the small intestine (duodenum, jejunum, and ileum).
The Circulatory Systems: Vascular (blood) System
Blood delivers oxygen and nutrients and removes carbon dioxide and waste. Water soluble nutrients and small fats are routed to the liver before being transported to the cells.
Liver
Body organ that detoxifies harmful substances that are ingested.
Goblet Cells
Cells of the GI tract (and lungs) that secrete mucus.
Cholecystokinin
Chief function is to trigger the release of bile, slow GI mobility (protein and fat take longer to digest than carbohydrates), and trigger the release of pancreatic fluid.
Muscular Action of Digestion: Peristalsis
Circular and longitudinal muscles work together passing the intestinal contents along. Rate and intensity of contractions vary depending on the part of the GI tract and if food is present.
Peristalsis
Contractions in GI tract muscles that move food through the digestion process.
Constipation
Eating high fiber foods and drinking plenty of fluids can help alleviate ____________.
Secretions of Digestion:
Enzymes are proteins that facilitate the making and breaking of bonds in chemical reactions.
The enormous surface of the small intestine facilitates nutrient absorption. Nutrients can be absorbed through:
Facilitated Diffusion- utilizes a carrier to move substances across a cell membrane (water-soluble vitamins).
Muscular Action of Digestion: Peristalsis
Factors that may interfere with peristalsis are stress, medicines, and medical conditions.
The Circulatory Systems: Lymphatic System
Fat soluble nutrients enter the lymphatic system, bypass the liver at first and eventually enter the vascular or blood circulatory system.
Anatomy of the Absorption System: Preparing Nutrients for Transport
Fat-soluble vitamins and larger fats form chylomicrons and are released into the lymphatic system. They bypass the liver at first.
Villi
Finger-like projections from the folds of the small intestine. They select and regulate nutrients absorbed.
The Circulatory Systems: Lymphatic System
Fluid moves from one portion of the body to another as muscles contract and create pressure here and there. Ultimately, much of the lymph collects in the thoracic duct behind the heart. The thoracic duct opens into the subclavian vein, where the lymph enters the blood stream.
Anatomy of the Absorption System:
Food combining is a myth that emphasizes separating food for digestive purposes. ex: fruit/meat
Secretions of Digestion:
Gastric glands secrete gastric juice (target organ stomach). Gastric juice is a mixture of water, enzymes, and hydrochloric acid.
Health and the GI Tract:
Homeostasis- maintenance or constant internal conditions. (homeo = the same, stasis = staying) ex: blood chemical, temperature, and blood pressure
Health and the GI Tract:
Hormones act as chemical messengers, sometimes regulate enzymes. Each hormone travels to one or more specific target tissue or organ, where it elicits a specific response to maintain homeostasis.
Secretions of Digestion:
Hydrochloric acid uncoils protein; Enzymes breakdown protein; The function of mucus in the stomach is to protect the stomach cells from gastric juices.
The Final Stage:
In the colon, intestinal bacteria ferment some fibers, producing water, gas, and small fragments of fat that provide energy for the cells of the colon. The colon retrieves all material that the body can recycle such as water and dissolved salts.
Lumen
Inner space within the GI tract. It is continuous from one end to the other.
Ciliac Disease
Involves autoimmune response to gluten in foods.
Secretions of Digestion:
Liver produces bile and secretes it to the gallbladder for storage, until it is needed. Gallbladder secretes bile into the small intestine. Bile is not an enzyme, it is an emulsifier. Bile emulsifies fat so that enzymes can break it down.
Mouth
Location where the process of digestion begins.
Health and the GI Tract:
Non-disease causing bacteria in the intestines are sometimes referred to as flora.
Muscular Action of Digestion: Peristalsis
Peristalsis pushes the digestive contents along.
Health and the GI Tract:
Prebiotics are foods that are used as foods by intestinal bacteria.
Health and the GI Tract:
Probiotics are bacteria found in the GI tract that can be beneficial to health (bacteria in yogurt like Lactobacillus)
Mouth: Mastication
Process of chewing.
Enzymes
Proteins that are essential for breaking down foods chemically.
Homeostasis
Refers to the body's overall plan to keep things "relatively the same"
Secretin
Responds to acidic chyme in the small intestine and is secreted from the duodenal wall. It stimulates the pancreas to release bicarbonate-rich juices into the small intestine to neutralize the acidic chyme.
Gastrin
Responds to food in the stomach and is secreted from the stomach wall. It stimulates stomach glands and hydrochloric acid is secreted into the stomach.
Secretions of Digestion:
Salivary glands secrete saliva. Saliva contains water, salts, mucus, and enzymes. Digestion of carbohydrates begin in the mouth. Saliva also protects the teeth, linings of the mouth, esophagus, and stomach from substances that might cause damage.
Muscular Action of Digestion:
Segmentation is contractions of circular muscles that contract and squeeze contents to mix the chyme and promote close contact with the digestive juices and absorption cells of the intestinal walls before letting the contents move slowly along.
The enormous surface of the small intestine facilitates nutrient absorption. Nutrients can be absorbed through:
Simple Diffusion- allows substances to cross a cell membrane without energy (water or small lipids).
Mouth: Savory
Some scientist also include the savory associated with monosodium glutamate, sometimes called savory or it's Asian name, umami.
Muscular Action of Digestion:
Sphincter contractions periodically open and close passageways. This prevents reflux and controls the pace of the GI contents. re = back flux = flow
Mouth: Four basic taste sensations
Sweet, sour, bitter, and salty.
Know this:
Table 3-1 page 75
Secretions of Digestion:
The cells of the intestinal wall also possess digestive enzymes on their surfaces. These enzymes also act on all three energy nutrients.
Esophagus to the Stomach:
The esophagus has a sphincter muscle at each end.
The Circulatory Systems: Vascular (blood) System
The hepatic portal vein directs blood from the GI tract to the liver.
The Circulatory Systems: Vascular (blood) System
The hepatic portal vein takes blood from the liver to the heart. the liver protects against toxic substances.
Esophagus to the Stomach: Lower Sphincter
The lower esophageal sphincter (also called the cardiac sphincter because of its proximity to the heart) is located at the entrance of the stomach and closes behind the bolus.
The Circulatory Systems: Lymphatic System
The lymphatic system has no pump (heart); lymph circulates between cells of the body and collects into tiny vessels.
Absorption:
The majority of absorption occurs in the small intestine. The small intestine is 10 feet long and has a surface area equivalent to a tennis court.
Secretions of Digestion:
The pancreas contributes pancreatic juice by way of ducts leading into the duodenum. This pancreatic juice contains enzymes that act on all three energy nutrients. The pancreatic juice also contains sodium bicarbonate, which is basic of alkaline, the opposite of the stomach's acid, which neutralizes the acidic chyme.
Digestion
The process by which food is broken down into absorbable units. Digest- take apart
Mouth
The process of digestion begins in the mouth.
Mouth: What affects a food's flavor
The sense of smell is thousands of times more sensitive than the sense of taste.
Muscular Action of Digestion:
The stomach has the thickest walls and is the strongest muscle of all the GI tract organs. 3 layers of muscle: circular, longitudinal, and diagonal.
Esophagus to the Stomach:
The stomach retains the bolus for a while in the upper portion. In small amounts the stomach transfers the bolus to the lower portion. The food is grinded into a semi-liquid mass called chyme. Chyme is released through the pyloric sphincter, which opens into the small intestines and then closes behind the chyme.
Esophagus to the Stomach: Upper Sphincter
The upper esophageal sphincter opens when swallowing. The bolus slides down the esophagus, which passes through a hole in the diaphragm to the stomach.
Absorption
The uptake of nutrients by the cells of the small intestine for transport into either the blood or the lymph. Absorb- suck in
The Circulatory Systems: Vascular (blood) System
The vascular (or blood) circulatory system is a closed system of vessels through which blood flows continuously and the heart serves as the pump.
The Circulatory Systems:
This includes the vascular system and the lymphatic system.
Microvilli
Tiny, hair-like projections on each cell of every villus that can trap nutrient particles and transport them into the cells. Enzymes and "pumps"
Secretions of Digestion:
To break down foods into nutrients requires secretions from five different organs: salivary glands, stomach, pancreas, liver (via gallbladder), and the small intestine. These secretions bring an abundance of water and variety of enzymes.
Mouth: Epiglottis
To bypass the entrance to the lungs, the epiglottis closes off the airway so that choking doesn't occur when swallowing.
Crypts
Tubular glands that lie between the intestinal villi and secrete intestinal juices into the small intestine. Secretion of intestinal juices.
The Final Stage:
Undigested residues such as fibers are not absorbed. They continue through the digestive tract, carrying some minerals, bile acids, additives, and contaminants out of the body. This semisolid mass helps exercise the intestinal muscles and keep them strong enough to perform peristalsis efficiently. Fiber also retains water accounting for the consistency of the stools.
Health and the GI Tract:
Vitamins can be produced by bacteria, but the amount is insufficient to meet the body's total need for these vitamins.
Anatomy of the Absorption System: Preparing Nutrients for Transport
Water-soluble nutrients and small products of fat digestion are released into the bloodstream. They are guided to the liver.
Secretions of Digestion: ASE
Word ending in ASE denotes an enzyme. Enzymes are often identified by the organ they come from and the compounds they work on. ex: Gastric Lipase- stomach enzymes acts on lipids ex: Pancreatic Lipase- comes from pancreatic, acts on lipids
