Chapter 3 (Nutrition)
main roles of the organs of the GI tract:
(1) break food down into its smallest components; (2) absorb the nutrients; (3) prevent microorganisms or other harmful compounds consumed with food from entering the tissues of the body
Powerful Digestive Secretions:
-hydrochloric acid (HCl), -various enzymes -mucus -intrinsic factor (needed for -vitamin B12 absorption) -stomach hormone gastrin
How long do the cells that line the gastrointestinal tract typically function?
3-5 days
gastrin
A digestive hormone produced in the stomach that stimulates digestive activities and increases motility and emptying.
Epiglottis
A flap of tissue that seals off the windpipe and prevents food from entering.
Secretin
A hormone secreted by the small intestine (duodenum) in response to low pH (e.g., from stomach acid). It promotes the release of bicarbonate from the pancreas to act as a buffer.
Ghrelin
A hunger-arousing hormone secreted by an empty stomach
Gallbladder
A muscular sac attached to the liver that secretes bile and stores it until needed for digestion
esophagus
A muscular tube that connects the mouth to the stomach.
hydrochloric acid (HCl)
A powerful acid made in the stomach that has digestive functions. It also helps to kill microorganisms and lowers the pH in the stomach.
Bile
A substance produced by the liver that breaks up fat particles. This dilute liquid consists of water, bile acids (and/or salts), various fats including cholesterol, and pigments. Bile is released from the gallbladder into the small intestine through the bile duct.
Bolus
A term used to describe food after it has been chewed and mixed with saliva
What bacteria in the colon play a role in producing what vitamins?
B vitamin biotin and vitamin K
Chyme
Bolus of food, that is semi liquid and contains digestive secretions.
What is the autoimmune disorder that damages the walls of the small intestine when gluten is consumed?
Celiac disease
lymphatic system
Composed of a network of vessels, ducts, nodes, and organs. Provides defense against infection.
Difficult swallowing, or dysphagia
Difficult swallowing, or dysphagia, can have mechanical causes such as tumors, scar tissue, obstruction, cancer, trauma, or other barriers in the throat. Dysphagia can also result from nerve damage or a stroke.
Enzymes
Digestive enzymes speed up the chemical reactions that break apart food particles into smaller, unbound nutrients that can be easily absorbed. All macronutrients—carbohydrates, fats, and proteins—are broken down by their own specific enzymes without changing or consuming the enzymes in the process
Gingivitis and Periodontal Disease
Gingivitis is an early form of periodontal disease that involves gum swelling, bleeding, and oral pain. Periodontal disease is an inflammation of the gums that leads to multiple dental diseases. It is caused by infections or by plaque that adheres to the surface of the teeth.17 Periodontitis results in a gradual loss of teeth as they loosen or partially separate from the gums and jawbone
What is the most common cause of peptic ulcers?
Helicobacter pylori bacterium
Which intestinal disorder is characterized by the colon overresponding to normal stimuli, which causes alternating patterns of constipation and diarrhea?
Irritable bowel syndrome (IBS)
enterohepatic circulation
Process that allows bile to be reused up to 20 times. Bile is unlike any other juices because it can be reused.
Gallstones
Small crystals that form from bile in the gallbladder.
When blood glucose levels are too low, what does the body do to increase glucose levels in the blood?
The pancreas releases glucagon
Cholecystokinin
This powerful hormone also stimulates the pancreas to secrete digestive enzymes, controls the pace of digestion, and contributes to meal satisfaction.
circulatory system
Transports oxygen, waste, nutrients, hormones, heat, etc... around the body
Segmentation
a "sloshing" motion that thoroughly mixes food with chemical secretions in the small intestine. Segmentation is different from peristalsis in that food is shifted back and forth along the small intestine to increase the time food comes into contact with the intestinal walls.
colon cancer
a malignant tumor of the colon
stomach
a muscular organ that continues mechanical digestion by churning and contracting to mix food with digestive juices
passive diffusion
a process in which nutrients are absorbed due to a concentration gradient. When the concentration is greater in the GI tract than inside the intestinal cell, the nutrient is forced across the cell membrane. This simple process doesn't require energy or a special protein carrier to help the nutrient to cross inside the intestinal cell.
Cecum:
a small, pouchlike area that has the appendix hanging from one end
Saliva
a watery fluid that will help soften the food you are about to eat
What is the main cause of heartburn?
a weak gastroesophageal sphincter
Important functions of the large intestine:
absorption of water, production of a few vitamins, absorption of important electrolytes, and the formation and storage of fecal material
enzymes produced by pancreas
amylase, which digests carbohydrate; lipase, which digests fat; precurors to the enzymes trypsin, chymotrypsin, and carboxypeptidase, which digest protein
celiac disease
an inherited autoimmune disorder characterized by a severe reaction to foods containing gluten
Pancreas
an organ about the size of your hand that produces hormones, including the two blood glucose-regulating hormones, insulin and glucagon. It also produces digestive enzymes and bicarbonate that are delivered into the small intestine through the pancreatic duct. Bicarbonate neutralizes the acid found in the chyme (raises the pH), creating a neutral environment. This protects certain enzymes that would otherwise become inactivated in an acidic environment.
gastroesophageal reflux disease (GERD)
backflow of contents of the stomach into the esophagus, often resulting from abnormal function of the lower esophageal sphincter, causing burning pain in the esophagus
Salivary amylase begins the digestion of ________ in the ________.
carbohydrate; mouth
Segment of the large intestine:
cecum, colon, and rectum
complete digestion of chyme requires:
chemical secretions, including hormones, enzymes, and bile
Anus
connected to the rectum and controlled by two sphincters: an internal and an external sphincter. Under normal conditions, the anal sphincters are closed. Periodically, the anal sphincters will relax, stool will enter the anal canal, and defecation will occur. The final stage of defecation is under our voluntary control and influenced by age, diet, prescription medicines, health, and abdominal muscle tone.
endocrine system
consists of a series of glands, including the pancreas, the pituitary, the thyroid, and the adrenal glands, that release hormones into the bloodstream. The hormones regulate growth, reproduction, metabolism, and the cells' use of absorbed nutrients
gastrointestinal (GI) tract
consists of the mouth, esophagus, stomach, small intestine, and large intestine
Pendular movement (constrictive wave)
constrictive wave that involves both forward and reverse movements and enhances nutrient absorption in the small intestine. Together, these three actions move chyme at a rate of 1 centimeter per minute.3 Depending on the amount of food and the type of food consumed, the contact time in the small intestine is about 3 to 6 hours.
Active transport
different from both passive and facilitated diffusion. In this form of absorption, digested nutrients are absorbed from a low to a high concentration. This process requires both a carrier and energy to shuttle nutrients across the cell membrane.
epiglottis function
directs food to continue down esophagus and not trachea
The _________ system releases hormones into the bloodstream to regulate cellular use of absorbed nutrients.
endocrine
Amylase
enzyme that breaks down starch
Protease
enzyme that digests protein
gastric lipase
enzyme to digest fat
The compounds that help break down foods during digestion by speeding up chemical reactions are called _____.
enzymes
The protective tissue that covers the trachea during swallowing and prevents choking is the _____.
epiglottis
Glycogen
excess carbohydrate that is stored in your liver and muscle
Deudenum
first part of the small intestine
digestive process
food is softened with moisture and heat, and then broken down into smaller particles by chewing and exposure to enzymes.
One of the most common digestive conditions involving the esophagus is ________.
heartburn
mucus
helps lubricate the food, helps it stick together, and protects the inside of the mouth
The name of the secretion produced in the stomach that helps break down protein and activates pepsin is _____.
hydrochloric acid (HCl)
gastroenteritis
inflammation of the stomach and intestines
Crohn's Disease
inflammatory bowel disease, is the general name for diseases that cause swelling in the intestines. Crohn's disease can affect any area of the GI tract, from the mouth to the anus, but it typically affects the ileum. The swelling can cause pain and diarrhea. Bleeding from the rectum, weight loss, and anemia are just some of the symptoms that can occur. Though there isn't a cure for Crohn's disease, medication, nutritional and dietary supplements, and/or surgery are currently used to manage the disease.
lumen
interior of the intestinal tract
Mechanical digestion
involves chewing, grinding, and breaking food apart and then moving it through, the GI tract
Chemical digestion
involves digestive juices and enzymes breaking down food into absorbable nutrients that are small enough to enter the cells of the GI tract, blood, or lymph tissue.
liver
is the largest organ in the body. It is so important that you couldn't survive without it. The liver produces about 500 to 1,000 milliliters (about 2 pints) of bile each day13 and helps regulate the metabolism of carbohydrates, fats, and protein. The liver also stores several nutrients, including vitamins A, D, and E; the minerals iron and copper; and glycogen, the storage form of glucose.
Accessory Organs
liver, gallbladder, pancreas
small intestine
long, narrow, coiled chamber in the abdominal cavity. Consists of 3 segments: - duodenum -shortest, the primary site for food digestion within the human body - jejunum - ileum - longest
Most fats and fat-soluble nutrients are absorbed and carried through the ______ system.
lymphatic
Esophageal cancer
malignant tumor of the esophagus
During digestion, what process or action breaks food down into smaller units that can be absorbed by the body?
mechanical and chemical processes
jejunum and ileum segments of the small intestine are where:
most of the absorption of digested nutrients takes place
In what order do the organs of the gastrointestinal tract digest and absorb nutrients?
mouth, esophagus, stomach, small intestine, large intestine
absorption
nutrients are absorbed through the walls of the intestines and into the body's two transport systems: the circulatory and lymphatic systems. They are then taken to the liver for processing before moving on to their destination.
Peristalsis
occurs throughout the GI tract and helps mix food with digestive secretions and propel the mixture from the esophagus through the large intestine.
Endocytosis
occurs when whole proteins, such as immunoglobulin from breast milk, are absorbed intact by the cell membrane
Which accessory organ makes and secretes digestive enzymes and bicarbonate into the small intestine?
pancreas
accessory organs of the digestive system
pancreas, liver, and gallbladder—that aid in digestion by secreting digestive juices through ducts into the small intestine
Once digested nutrients reach the small intestine, they are absorbed by three methods:
passive diffusion, facilitated diffusion, active transport
Pharynx (throat)
performs the swallowing action that passes food from the mouth into the esophagus
Microvilli
projections that increase the cell's surface area
pepsin
protein-digesting enzyme, that enhances the absorption of minerals, breaks down the connective tissue in meat, and destroys some ingested microorganisms
The sphincter that connects the stomach to the small intestine is called the ________.
pyloric sphincter
The sphincter that separates the stomach from the duodenum is the _____.
pyloric sphincter
Hormones
released from endocrine glands scattered throughout the lining of the stomach and the small intestine, don't digest food, but regulate the activity of other cells
Gastrin
released to signal the rest of the GI tract to prepare for digestion. Gastrin stimulates the stomach to release HCl, increases gastric motility and emptying, and increases the tone of the LES. Gastrin also causes the release of gastric secretions that contain the enzyme gastric lipase.
LES (lower esophageal sphincter)
ring of muscles between the esophagus and the stomach
gastroesophageal sphincter
separates the esophagus from the stomach
facilitated diffusion
similar to passive diffusion in that nutrients are absorbed from a high to a low concentration and the process does not require energy. But facilitated diffusion does require a specialized protein to carry the nutrients across the cell membrane
Most of the digestion and absorption of food occurs in the ________.
small intestine
Peptic ulcers
sores that affect the mucous membranes of the digestive system
heartburn (pyrosis)
temporary inflammation of the esophagus due to reflux of stomach acid - if the gastroesophageal sphincter doesn't close once the food has entered the stomach. If the sphincter doesn't close contents may flow back into the esophagus and irritate its lining.
Rectum
the final eight-inch portion of the large intestine, where it is stored. When stool distends the rectum, the action stimulates stretch receptors, which in turn stimulate the defecation reflex. This causes nerve impulses of the rectum to communicate with the rectum's muscles. The end result is relaxation of the internal sphincter of the anus.
Colon
the largest portion of the large intestine. The colon includes the ascending, transverse, descending, and sigmoid regions. These regions are relatively long and straight. Most of the vitamin production and absorption of water and electrolytes occur within the first half of the colon. The last half of the colon stores fecal matter.
borborygmus
the rumbling noise caused by the movement of gas in the intestine
excretory system
the system that removes waste from your body and controls water balance
What is the purpose of the gallbladder?
to concentrate and store bile
ileocecal sphincter
which serves as the gateway to its next digestive destination, the large intestine
