Human Bio Chapter 15 (Zool 1020)
__________ occurs when the pressure of the stomach contents overwhelms the sphincter at the lower end of the esophagus, causing a burning sensation behind the breastbone.
Heartburn
_______________ is released from the small intestine into the bloodstream and is carried back to the small intestine, where it causes the release of intestinal juices. At the same time, the small intestine releases a second hormone, secretin, which stimulates the release of sodium bicarbonate from the pancreas into the small intestine to help neutralize the acidity of chyme. A third hormone from the small intestine is cholecystokinin (ko¯'lı˘-sı˘s-to¯-kı¯-nı˘n), which causes the pancreas to release its digestive enzymes and the gallbladder to contract and release bile.
Vasoactive intestinal peptide
3 parts of the small intestine
duodenum, jejunum, ileum
Chyme from the stomach enters the duodenum, the first region of the small intestine, in squirts, so that only a small amount enters the small intestine at one time. Digestive juices also enter the duodenum from the pancreas and liver. However, most chemical digestion and absorption occur in the __________ and the __________.
jejunum and the ileum
The muscle layers churn the food until it is liquefied, mix the resulting liquid with enzymes, and propel the food along the GI tract in a process called __________.
peristalsis
The primary function of the stomach is to _____.
store and digest food
What is the primary role of the large intestine in digestion?
Absorbs ions, water, and vitamins to maintain homeostasis
Digestion of starch begins in the mouth with what enzyme?
Amaylase
___________, a mixture of water, ions, cholesterol, bile pigments, and bile salts, plays an important role in the mechanical digestion of fats, which assists lipase in chemically digesting fats.
Bile
Which of the following hormones functions to stimulate the release of digestive enzymes from the pancreas? Vasoactive intestinal peptide Gastrin Secretin Cholecystokinin
Cholecystokinin
True or false? Water-soluble nutrients are absorbed into the lacteals, whereas lipid-soluble nutrients are absorbed into the blood capillaries.
False
The pancreas, liver, and gallbladder are not part of the __________.
GI tract
The substance present in stomach secretions that does the most damage in heartburn is _____.
HCl
What does the liver do?
It produces bile which neutralizes stomach acid and emulsifies fat; it also monitors blood contents
__________ is the more technical name for what we have been calling fat.
Lipid
What are the complexes of glycerol, fatty acids, and bile salts formed in the lumen of the small intestine called?
Micelles
Along most of its length, the walls of the GI tract have four basic layers. What are those layers from innermost to outermost?
Mucosa, submucosa, muscularis, serosa
__________, an invisible film of bacteria, mucus, and food particles, promotes tooth decay because it holds the acid against the enamel.
Plaque
Chemical digestion of proteins is confined to which combination of organs in the digestive system?
Stomach and small intestine
What is the salivary gland that is below the tongue?
Sublingual
What are the fingerlike projections along the surface of the small intestine called?
Villi
Saliva also contains an enzyme, salivary __________, that begins to chemically digest starches into shorter chains of sugar.
amylase
Extending from the cecum is another slender, wormlike pouch, called the ___________.
appendix
The __________ has no digestive function. Some scientists believe it plays a role in the immune system, which protects the body against disease.
appendix
Pancreatic juice drains from the pancreas into the pancreatic duct, which fuses with the common __________ from the liver just before entering the duodenum of the small intestine.
bile duct
The tongue moves food into position for crushing and grinding by the teeth, to mix it with saliva, and to shape it into a small, soft mass, called a __________, that is easily swallowed.
bolus
The microvilli form a fuzzy surface, known as a __________ border.
brush
The crown of the tooth (the part visible above the gum line) is covered with enamel, a nonliving material hardened with __________ salts.
calcium
As substances are absorbed from the small intestine, they cross only two cell layers: the epithelial cells of the villi and the wall of either a __________ or a lacteal.
capillary
The __________ is a pouch that hangs below the junction of the small and large intestines.
cecum
The root of the tooth (the part below the gum line) is covered with a calcified, yet living and sensitive connective tissue referred to as __________.
cementum
Vasoactive intestinal peptide is released from the small intestine into the bloodstream and is carried back to the small intestine, where it causes the release of intestinal juices. At the same time, the small intestine releases a second hormone, secretin, which stimulates the release of sodium bicarbonate from the pancreas into the small intestine to help neutralize the acidity of chyme. A third hormone from the small intestine is _____________________, which causes the pancreas to release its digestive enzymes and the gallbladder to contract and release bile.
cholecystokinin (ko¯'lı˘-sı˘s-to¯-kı¯-nı˘n)
Certain lipids, including __________, are essential components of all cell membranes; some are used in the construction of myelin sheaths that insulate nerve fibers.
cholesterol
When a micelle contacts an epithelial cell of a villus, the products of fat digestion easily diffuse into the cell. Within an epithelial cell, the glycerol and fatty acids are reassembled into triglycerides, are mixed with cholesterol and phospholipids, and are coated with special proteins, thus becoming part of a complex known as a _________________.
chylomicron (kı¯lo¯mi´-krän)
This additional mechanical digestion occurs as the food is churned and mixed with secretions produced by the glands of the stomach until it is a soupy mixture called __________.
chyme
The largest region of the large intestine, the __________, is composed of the ascending colon on the right side of the abdomen, the transverse colon across the top of the abdominal cavity, and the descending colon on the left side.
colon
Teeth are alive. In the center of each tooth is the pulp, which contains the tooth's life-support systems—blood vessels that nourish the tooth and nerves that sense heat, cold, pressure, and pain. Surrounding the pulp is a hard, bonelike substance, called __________.
dentin
The primary function of the small intestine is to _____.
digest and absorb nutrients
The __________ system consists of a long, hollow tube, called the gastrointestinal (GI) tract, into which various accessory glands release their secretions
digestive
After leaving the stomach, chyme enters the _____.
duodenum
Chyme from the stomach enters the __________, the first region of the small intestine, in squirts, so that only a small amount enters the small intestine at one time. Digestive juices also enter the duodenum from the pancreas and liver. However, most chemical digestion and absorption occur in the jejunum and the ileum.
duodenum
The bile salts __________ fats; that is, they keep fats separated into small droplets that disperse in liquid. This separation exposes a larger combined surface area to lipase, making the chemical digestion and absorption of fats faster and more complete.
emulsify
The pancreatic __________ and intestinal enzymes break nutrients into their component building blocks: proteins to amino acids, carbohydrates to monosaccharides, and triglycerides (a type of lipid) to fatty acids and glycerol.
enzymes
When we swallow, food is pushed from the mouth, through the pharynx, and into the __________, the tube that connects the pharynx to the stomach.
esophagus
Human proteins contain 20 different kinds of amino acids. The 9 amino acids that the body cannot synthesize—called __________ amino acids—must be supplied by the diet.
essential
Three nutrients—__________, __________, and __________—can provide energy.
fats (lipids), carbohydrates, and proteins
After it is produced by the liver, bile is stored, modified, and concentrated in a muscular, pear-shaped sac called the ___________.
gallbladder
The lining of the stomach has millions of gastric pits, within which are __________ glands containing several types of secretory cells.
gastric
Distention of the stomach by swallowed food, along with the presence of partially digested proteins, stimulates cells in the stomach lining to release the hormone __________.
gastrin
The _______________ begins at the mouth and continues to the pharynx, esophagus, stomach, small intestine, and large intestine.
gastrointestinal (GI) tract
The region of the palate closest to the front of the mouth, the ______________, is reinforced with bone.
hard palate
Blood flows from the small intestine to the liver through the _____, then from the liver to the inferior vena cava through the _____.
hepatic portal vein; hepatic vein
Although not related to the digestive function of the stomach, a very important material secreted by the gastric glands is ________________, a protein necessary for the absorption of vitamin B12 from the small intestine.
intrinsic factor
When the mixture of pepsin and HCl, called gastric __________, is released into the stomach, the pepsin begins the chemical digestion of the protein in food.
juice
The core of each villus is penetrated by a network of capillaries and a __________, which is a lymphatic vessel.
lacteal
Without bile, one would be unable to digest _____ completely.
lipids, found in butter and fried foods
Bile is produced by the __________, is stored in the gallbladder, and acts in the small intestine.
liver
The largest internal organ in the body
liver
The GI tract begins at the mouth and continues to the pharynx, esophagus, stomach, small intestine, and large intestine. The hollow area of the tube through which food and fluids travel is the __________.
lumen
The products of fat digestion, glycerol and fatty acids, combine with bile salts in the small intestine, creating particles called ___________.
micelles (mī-selz′)
The absorptive epithelial cells covering the surface of each villus contain thousands of microscopic projections, referred to as ___________, that increase the surface area of the small intestine by another 20 times.
microvilli
Which of the following gives the correct order of the organs that food passes through in the digestive system?
mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus
Mechanical digestion begins in the _____, and chemical digestion begins in the _____.
mouth;mouth
The innermost layer of the GI tract is the moist, mucus-secreting layer called the __________.
mucosa
In most sections of the GI tract, the ____________ is a double layer of smooth muscle.
muscularis
The __________ is responsible for movement of materials through the GI tract and for mixing ingested materials with digestive secretions.
muscularis
In the esophagus, small intestine, and large intestine, peristalsis is produced by the two layers of muscle in the __________.
muscularis The third of the basic layers of the GI tract, Muscles are in layers, each laying a different way.
A __________ is a substance in food that provides energy; becomes part of a structure; or performs a function in growth, maintenance, or repair.
nutrient
The roof of the mouth is the __________.
palate
The __________ is an accessory organ that lies behind the stomach, extending from the small intestine toward the left side of the body.
pancreas
Chyme from the stomach enters the duodenum, the first region of the small intestine, in squirts, so that only a small amount enters the small intestine at one time. Digestive juices also enter the duodenum from the _________ and __________. However, most chemical digestion and absorption occur in the jejunum and the ileum.
pancreas and liver
Although both the small intestine and the pancreas contribute enzymes, most of the digestion that occurs in the small intestine is actually performed by __________ enzymes.
pancreatic
What is the salivary gland that is in front of the ears?
parotid
Once activated by HCl, pepsinogen becomes __________, a protein-digesting enzyme.
pepsin
Certain secretory cells produce hydrochloric acid (HCl), which kills most of the bacteria swallowed with food or drink. Hydrochloric acid also breaks down the connective tissue of meat and activates __________, which is secreted by other cells in the gastric glands.
pepsinogen
Food is moved along the esophagus and all the rest of the GI tract by rhythmic waves of muscle contraction called __________.
peristalsis
The __________, which is the passageway commonly called the throat, is shared by the respiratory and digestive systems.
pharynx
The entire lining of the small intestine is __________, like an accordion, into circular folds. These circular folds increase the surface area for absorption and cause chyme to flow through the small intestine in a spiral pattern. The spiral flow helps mix the chyme with digestive enzymes and increases its contact with the absorptive surfaces. Covering the entire lining surface are tiny 1 mm projections called villi (singular, villus).
pleated
The tongue functions to _____.
position food for chewing and swallowing
The small intestine, the __________ site of absorption in the digestive system, is extremely effective at its task because it is long and has several structural specializations that vastly increase its surface area.
primary
What does the pancreas do?
produces enzymes for digestion, It secretes juices that raise the pH of the small intestine
Vasoactive intestinal peptide is released from the small intestine into the bloodstream and is carried back to the small intestine, where it causes the release of intestinal juices. At the same time, the small intestine releases a second hormone, __________, which stimulates the release of sodium bicarbonate from the pancreas into the small intestine to help neutralize the acidity of chyme. A third hormone from the small intestine is cholecystokinin (ko¯'lı˘-sı˘s-to¯-kı¯-nı˘n), which causes the pancreas to release its digestive enzymes and the gallbladder to contract and release bile.
secretin
The __________ is a thin layer of epithelial tissue supported by connective tissue, wraps around the GI tract.
serosa
The tongue is a large __________ muscle studded with taste buds.
skeletal
The __________ intestine has two major functions: chemical digestion and absorption.
small
Toward the back of the mouth is the ______________, which consists only of muscle and prevents food from entering the nose during swallowing.
soft palate
Bands of circular muscle called __________ guard the openings at each end of the stomach and regulate the release of food to the small intestine.
sphincters
What does the gallbladder do?
stores and concentrates bile
Three pairs of salivary glands—the __________ (below the tongue), __________ (below the jaw), and __________ (in front of the ears)—release their secretions, collectively called saliva, into the mouth.
sublingual, submandibular, parotid
What is the salivary gland that is below the jaw?
submandibular
The __________ consists of connective tissue containing blood vessels, lymph vessels, and nerves.
submucosa
The large intestine has four regions:
the cecum, colon, rectum, and anal canal
The __________ increase the surface area of the small intestine tenfold.
villi
the entire lining of the small intestine is pleated, like an accordion, into circular folds. These circular folds increase the surface area for absorption and cause chyme to flow through the small intestine in a spiral pattern. The spiral flow helps mix the chyme with digestive enzymes and increases its contact with the absorptive surfaces. Covering the entire lining surface are tiny 1 mm projections called ________________.
villi (singular, villus)
