10.2 Structure and Function of the Digestive System

Question 1

Organisms that are too big to diffuse nutrients and water for survival must have ___________

Answer 1

a digestive system

Question 2

What are the 4 stages of food processing?

Answer 2

Ingestion
Digestion
Absorption
Elimination

Question 3

what kind of specialized organ does a sea anenome have?

Answer 3

digestive sac

Question 4

what kind of specialized organ does a nematode have?

Answer 4

digestive tract

Question 5

explain ingestion

Answer 5

Ingestion is the act of eating or drinking.

Question 6

explain digestion

Answer 6

Digestion is the process of breaking food down into molecules that are small enough for the body to absorb

Question 7

mechanical digestion

Answer 7

(chewing) chops and grinds food into
smaller pieces, increasing its surface area.

Question 8

chemical digestion

Answer 8

breaks the chemical bonds within the large
molecules of carbohydrates, fats, and proteins and produces smaller molecules during hydrolysis

Question 9

hydrolysis

Answer 9

process that breaks bonds in food molecules by adding water to them in the presence of specific
enzymes

Question 10

if a protein was a macromolecule, what would the components be? (what would the protein-digesting enzymes turn it into)

Answer 10

amino acids

Question 11

if fat was a macromolecule, what would the components be? (what would the fat-digesting enzymes turn it into)

Answer 11

glycerol and fatty acids

Question 12

give an example of chemical digestion

Answer 12

protein (macromolecule) uses protein digesting enzymes to turn into amino acids

Question 13

give an example of a chemical digestion with fat

Answer 13

fat (macromolecule) uses fat digesting enzymes to turn into glycerol and fatty acids

Question 14

explain absorption

Answer 14

-occurs in the small intestine, where the cells absorb small molecules, such as amino acids and simple sugars
-from the small intestine, the molecules enter the circulatory system
-the molecules are transported in the blood to body cells, where they join to make bigger molecules or are broken down to provide energy
-if there are more molecules than are needed
immediately, they are converted to fat for storage

Question 15

explain elimination

Answer 15

Elimination is the process of removing from the digestive tract any undigested materials.

-These materials travel through the large intestine and are eliminated as feces.

Question 16

In more complex animals, digestion occurs in a tube called

Answer 16

an alimentary canal

Question 17

alimentary canal

Answer 17

-digestive tract with two openings, a mouth and
an anus.
-food enters through the mouth at one end of the canal and is churned and mixed as it travels along the tube
-further along the tube, nutrients are absorbed from the digested food and then the wastes are disposed of through the anus

Question 18

Why is an alimentary canal more
efficient than a digestive sac for obtaining nutrients from food?

Answer 18

because an alimentary canal has more specialized regions for processing food

Question 19

Another name for the alimentary canal is the _______

Answer 19

gastrointestinal tract
or GI tract

Question 20

The length of an animal’s alimentary canal is often correlated with _____

Answer 20

diet

Question 21

In general, herbivores and omnivores have ___ alimentary canals, relative to their body size, than carnivores.

Answer 21

longer

Question 22

Why do herbivores and omnivores have longer alimentary canals than carnivores?

Answer 22

Vegetation is more difficult to digest than meat because it contains cell walls. A longer alimentary
canal provides more time for digestion and more surface area for absorption of nutrients

Question 23

What are two advantages of a longer alimentary canal?

Answer 23

provides more time for digestion and more surface area for absorption of nutrients

Question 24

Most animal species
process food in specialized organs, an adaptation that avoids the risk of __________

Answer 24

self-digestion

Question 25

In humans, six main organs make up the alimentary canal:

Answer 25

the mouth, pharynx, esophagus, stomach, small
intestine, and large intestine

Question 26

Accessory glands and organs include:

Answer 26

the salivary glands, pancreas, liver, and gallbladder

Question 27

function of accessory glands and organs in the alimentary canal

Answer 27

secrete digestive juices into the alimentary canal

Question 28

the mouth

Answer 28

-Beginning of digestion
-Teeth and tongue: mechanical digestion
-Incisors, cuspids, bicuspids cut into and tear food
-Molars grind food into a paste
-Salivary glands secrete saliva
-Watery liquid that contains digestive enzymes,
mucus, and other chemicals

Question 29

Composition of saliva

Answer 29

1.) Enzymes :
-Amylase
-breaks down chemical bonds in starches to form
sugars
-Lysozyme
-helps fight infection by digesting cell walls of
bacteria

2.) Mucus
-coats and lubricates food

3.) Buffers
-protects teeth from acidic foods (swings in pH)

Question 30

Pharynx

Answer 30

-Upper part of the throat
Shared by digestive and respiratory system

-The tongue pushes chewed up food (bolus) down the throat

-Epiglottis: cartilaginous flap seals off the airway
-prevents food from moving into the
passageway as it passes through the pharynx
into the esophagus

Question 31

bolus

Answer 31

food that has been chewed and mixed in the mouth with saliva

Question 32

epiglottis and function

Answer 32

Epiglottis: cartilaginous flap seals off the airway

-prevents food from moving into the passageway as it passes through the pharynx into the esophagus

Question 33

esophagus

Answer 33

-Long, muscle-encased tube
Connects pharynx to stomach

-Gravity is not the reason your food travels downward

-Peristalsis: muscle contractions
-contract in a wave like fashion forcing bolus into
the stomach

-Once food is in the stomach, a valve called a sphincter closes the esophagus, preventing stomach contents from going back up the esophagus

-If the muscle opens at an inappropriate time, acid from the stomach can flow backward, causing heartburn

Question 34

peristalsis

Answer 34

when food is pushed through the esophagus by a series of muscle contractions

Question 35

sphincter

Answer 35

Once food is in the stomach a valve called a sphincter closes the esophagus, preventing stomach contents from going back up the esophagus

Question 36

what happens if the sphincter muscle opens at an inappropriate time?

Answer 36

acid from the stomach can flow backward causing heartburn

Question 37

mechanical vs. chemical digestion

Answer 37

Mechanical Digestion
-physical change
-chops and grinds food into smaller pieces
-increases surface area

Chemical digestion
-chemical change
-breaks the chemical bonds within the large molecules of carbohydrates, fats and proteins
-produces smaller molecules during hydrolysis

Question 38

give an example of a polymer and monomer in chemical digestion

Answer 38

polymer (fat)
monomers (glycerol and fatty acids)

Question 39

if amino acid is a monomer in a chemical digestion, what is the polymer

Answer 39

protein

Question 40

stomach

Answer 40

-Elastic, muscular sac
-Cardiac/lower esophageal and pyloric
-Mechanical and chemical digestion
-Contains accordion-like folds, is elastic (can stretch)

Question 41

mechanical digestion in the stomach

Answer 41

-Muscles in the stomach wall churn the food
-This action turns the bolus into a nutrient-rich
liquid called chyme
-force into small intestine
-pyloric sphincter regulates flow of chyme
-typically, it takes 2-6 hours for the stomach to empty

Question 42

chyme

Answer 42

the acidic fluid which passes from the stomach to the small intestine, consisting of gastric juices and partly digested food

Question 43

chemical digestion in the stomach

Answer 43

Gastric Juice:
secreted when you see, smell, or taste food; a message from your brain stimulates gastric glands
secreted by glands in the stomach lining.

-HCl: breaks down cells in food and kills bacteria
-Pepsin: enzyme that breaks large protein -
molecules
-Mucus: lubricates the stomach and prevents the
stomach from digesting itself
-Every 3 days, enough new stomach cells are created to replace the entire stomach

Question 44

gastric juice

Answer 44

-secreted when you see, smell, or taste food; a message from your brain stimulates gastric glands
-secreted by glands in the stomach lining

Question 45

hydrochloric acid

Answer 45

HCl: breaks down cells in food and kills bacteria

Question 46

pepsin

Answer 46

enzyme that breaks large protein molecules

Question 47

mucus

Answer 47

-lubricates the stomach and prevents the stomach from digesting itself
-every 3 days enough new stomach cells are
created to replace the entire stomac

Question 48

absorption

Answer 48

-Cells absorb monomers
-Amino acids, simple sugars

-Small intestine 🡪 diffuse to blood in circulatory
system

1.) go to body cells
2.) join to make polymers OR
3.) broken down to provide energy

-If there are more molecules than are needed, they are converted to fat for storage

Question 49

small intestine

Answer 49

-Chyme enters through pyloric sphincter
-moves via peristalsis (6m long, 2.5cm in diameter)
-3-5 hr process
-Absorption of most nutrients
-Digestion in 1st part (duodenum) absorption in rest

Question 50

what 3 structures make up the small intestine?

Answer 50

duodenum, illeum and jejunum

Question 51

duodenum

Answer 51

-U-shaped structure and is the shortest and the widest of all of the sections

-Pancreatic and bile ducts open into the duodenum making it extremely important for further chemical and mechanical breakdown of partially digested food.

Question 52

jejunum

Answer 52

-2.5 m long and contains more folds and intestinal glands than the duodenum
-Breaks down remaining proteins and carbohydrates

Question 53

illeum

Answer 53

-3m long contains fewer and smaller villi
-To absorb nutrients as well as to push remaining undigested material into the large intestine

Question 54

function of small intestine

Answer 54

absorption

Question 55

small intestines- villi form

Answer 55

-Finger-like projections inside intestines
-Each villus has microvilli
-Contain capillaries and lymph vessels (lacteals – carry fluid away)

Question 56

lacteals

Answer 56

carry fluid away

Question 57

small intestines- villi function

Answer 57

-Fatty acids and glycerol are absorbed by intestinal cells, they are recombined into fats and then transported into the lymph vessel

-Sugars and amino acids are absorbed into the bloodstream via the blood vessels in each villus

-From the bloodstream they travel to the liver where most nutrients are converted into other useable forms

-Liver detoxifies and cleanses materials before entering the heart

Question 58

the large intestine (colon)

Answer 58

-Undigested food passes cecum to here
-Food passes by appendix which contains white
blood cells and thusly, we think has an immune
function
-absorbs rest of water
-Between sm. and lg. intestine, 90% of water ingested is reclaimed
-As water is absorbed the remains of the digested food becomes more solid
-Wastes move along colon via peristalsis (12-24 hours)
-Undigested food material is called feces
-Feces are stored in the final portion of the colon called the rectum
-2 sphincters (1 voluntary, 1 involuntary)
regulate the opening of the anus

Question 59

what happens after the water is absorbed in the large intestine?

Answer 59

-As water is absorbed the remains of the digested food becomes more solid
-Wastes move along colon via peristalsis (12-24 hours)
-Feces are stored in the final portion of the colon called the rectum

Question 60

duodenum

Answer 60

The first section of the small intestine

Question 61

bile

Answer 61

-Bile is a yellow or greenish alkaline liquid produced outside of the small intestine by the body’s largest internal organ, the liver.
-Bile is stored in a sac-like structure called the
gallbladder until it is secreted into the duodenum. –Although bile contains no enzymes, it has substances that help prepare fats for hydrolysis

Question 62

pancreatic juice

Answer 62

-Pancreatic juice is a clear alkaline liquid that neutralizes the acidic chyme and contains enzymes
that further break down carbohydrates, proteins, and fats.
-Pancreatic enzymes, along with enzymes secreted by the lining of the small intestine, complete the chemical digestion of food.

Question 63

completing digestion in the small intestine

Answer 63

-carbohydrates are broken down to form sugars, which provide your cells with a source of energy
-these sugars are also a source of chains of carbon atoms that your body can use to construct other molecules containing carbon.
-The complete digestion of proteins results in amino acids that your cells use to build proteins
-The complete digestion of fats results in molecules of fatty acids and glycerol.
-Your cells use these molecules to build fats.

Question 64

villi

Answer 64

-The wall of the small intestine is folded into many small, finger-like projections called villi (singular, villus).
-The cells lining each villus have microscopic projections called microvilli

Question 65

lymph vessels

Answer 65

-Lymph vessels are structures that carry fluid away
from cells.
-After fatty acids and glycerol are absorbed by intestinal cells, these building blocks are recombined into fats that are then transported
into the lymph vessel

Question 66

Undigested food material and
other waste products are called

Answer 66

feces

Question 67

Feces are stored in the final portion of
the colon, the _______, until they can be eliminated

Answer 67

rectum

Question 68

what is the cause of gas in the digestive system

Answer 68

results from swallowed air or the breakdown
of undigested food in the colon

Question 69

endoscopy

Answer 69

-a narrow tube is inserted into the throat and passed into the esophagus, stomach, and upper intestine
-a small camera in the narrow tube enables the doctor to see the internal structures and to identify abnormalities
-Sometimes, the tube has tiny scissors that are used to cut a small piece of tissue for viewing under a microscope.

Question 70

what is the cutting procedure using an endoscopy called?

Answer 70

biopsy

-used to determine if the cells are normal and can also identify the presence of the Helicobacter pylori bacteria, which burrow into the stomach wall and cause inflammation

Question 71

colonoscopy

Answer 71

-During a colonoscopy, a thin, lighted tube with an attached camera is inserted through the rectum
-If an unusual growth is detected, the doctor may choose to perform a biopsy.
-If the biopsy indicates that the cells are abnormal or cancerous, it is sometimes possible to surgically remove those cells during the diagnostic procedure

Question 72

Gastroesophageal reflux disease (GERD)

Answer 72

Gastroesophageal reflux disease occurs when acid
from the stomach spills back up into the esophagus
so frequently that it harms the lining of the
esophagus.

Question 73

diagnosis and treatment for Gastroesophageal
reflux disease (GERD)

Answer 73

-Since smoking, drinking alcohol, and excess eating
seem to make this condition worse, doctors suggest that they be avoided.
-Antacids are prescribed to neutralize the stomach acid.
-Sometimes surgery is needed to strengthen the muscle that sits at the junction between the esophagus and the stomach.

Question 74

ulcer

Answer 74

-If the stomach lining is broken down it becomes
irritated by gastric acid.
-The gastric acid can also spill into other parts of the digestive system and irritate the tissues of nearby organs.
-Sores found in the stomach lining, esophagus or the upper small intestine are called peptic ulcers

Question 75

diagnosis + treatment of ulcers

Answer 75

-In order to properly diagnose an ulcer, a doctor may order a number of diagnostic tests including a blood test, feces or stool test, barium X-ray, and endoscopy.
-Barium is a white metallic liquid that coats the
digestive system and makes the ulcer more visible
in the radiograph produced by the X-ray.
-The blood and stool tests are used to identify the presence of H. pylori bacteria, the cause of most ulcers.

Question 76

Inflammatory bowel disease (IBD)

Answer 76

-In inflammatory bowel disease, the intestines become irritated and inflamed and develop many ulcers, causing abdominal pain and diarrhea.
-Two common inflammatory bowel diseases are ulcerative colitis and Crohn’s disease.
-Ulcerative colitis is found in continuous sections of the intestine and rectum.
-Crohn’s disease may occur anywhere in the digestive tract.

Question 77

diagnosis + treatment of Inflammatory bowel disease (IBD)

Answer 77

-The exact cause of inflammatory bowel disease
is still being researched.
-It is thought that the presence of foreign substances in the intestines may cause the body to attack itself in order to rid itself of the foreign invaders.
-This allergic type of reaction causes inflammation, which results in the development of ulcers.

Question 78

Constipation

Answer 78

-Constipation occurs when peristalsis moves the feces along too slowly or when the colon absorbs too much water and the feces become too compacted.
-Constipation is usually a temporary condition
resulting from a diet that does not include enough
plant fibre.
-Constipation sometimes results from surgery, medication, air travel, and pregnancy.

Question 79

diagnosis + treatment of constipation

Answer 79

To prevent constipation:
*Eat a healthy diet that contains a lot of fibre, such as fruit, vegetables, and grains.
-Fibre adds softness and bulk to the waste in the colon.
-As a result, the waste can pass through the colon more easily.
* Get plenty of exercise.
* Drink at least 1 L of water every day

Question 80

Diarrhea

Answer 80

-If the lining of the colon is irritated — by a viral or
bacterial infection, for instance — the colon is less
effective in reclaiming water, and diarrhea may
result.
-Severe diarrhea can cause dehydration and
become life-threatening without treatment.

Question 81

diagnosis + treatment of diarrhea

Answer 81

A healthy patient usually recovers from diarrhea
within several days, given enough clean water
and nutritious food. However, diarrhea can also
be a symptom of more serious disease, such as
infl ammatory bowel disease.

Question 82

Compare and contrast the terms “mechanical
digestion” and “chemical digestion”:
(a) in the mouth

Answer 82

MD-teeth
CD- saliva + enzymes

Question 83

Compare and contrast the terms “mechanical
digestion” and “chemical digestion”:
(b) in the stomach

Answer 83

MD- churns and mixes food
CD-enzymes break food smaller

Question 84

How is a bolus formed?

Answer 84

After ingestion, the solid hard materials are broken down into smaller pieces or chewed with the help of teeth. These food materials get mixed with the digestive juice called saliva secreted from the salivary gland by the movement of the tongue. Thus, this moist mixture forms ball-like structures called a bolus.

Question 85

What happens during hydrolysis?

Answer 85

a process that breaks bonds
in food molecules by adding water to them in the presence of specific
enzymes

Question 86

(a) Define peristalsis.
(b) Describe its role in the digestive system

Answer 86

-food is pushed through the esophagus by a series
of muscle contractions

-forces the bolus of food toward the stomach

Question 87

What is chyme?

Answer 87

mechanical digestion turns the bolus into an acidic, nutrient-rich liquid called chyme

Question 88

(a) What is bile?
(b) What is the role of bile in digestion?

Answer 88

Bile is a yellow or greenish alkaline
liquid produced outside of the small intestine by the body’s largest internal organ, the liver

-has substances that help prepare fats for hydrolysis and separates small fat droplets, which enables digestive enzymes to break down the fats more efficiently

Question 89

Explain the process of chemical digestion in
the duodenum

Answer 89

-As chyme enters the duodenum, it mixes with several digestive juices (e.g. bile)

-Bile is stored in a sac-like structure called the
gallbladder until it is secreted into the duodenum.

-Although bile contains no enzymes, it has substances that help prepare fats for hydrolysis.

-Fats tend to clump together, making it difficult for enzymes to reach the molecules.

Bile separates small fat droplets, which enables digestive enzymes to break down the fats more efficiently

Question 90

(a) State four locations where sphincters are
found in the digestive system.
(b) What is the role of a sphincter?

Answer 90

1) where the stomach and esophagus meet (cardiac)
2) where the duodenum and stomach meet (pyloric)
3) where the small intestine meets the large intestine (ileocecal)
4) end of anus (anal sphincter)

-circular muscles that open and close passages in the body to regulate the flow of substances

Question 91

anal sphincter

Answer 91

internal anal sphincter prevents uncontrolled movement of contents through the anus

Question 92

pyloric sphincter

Answer 92

opens to allow partially digested food to pass from the stomach into the duodenum where it will be exposed to bile and other digestive enzymes

Question 93

malfunction of pyloric sphincter can cause…

Answer 93

A malfunction of the pyloric sphincter can cause bile (a digestive enzyme produced by the liver) to back up into the stomach and sometimes the esophagus. Symptoms of bile reflux are indistinguishable from those of acid reflux.

Question 94

ileocecal sphincter

Answer 94

involuntary sphincter located where the small intestine and large intestine (colon) meet.

There is not much known about this sphincter. It is thought to regulate the movement of partially digested food from the ileum (the last section of the small intestine) to the large intestine.

Question 95

anal sphincter

Answer 95

regulates defecation (the evacuation of stool from the body).

The anal sphincter has both inner and outer muscles:

The inner sphincter is involuntary and prevents stool from leaking out.
The outer sphincter is predominantly voluntary and allows you to pass or hold stool on demand.

Question 96

malfunction of anal sphincter can cause…

Answer 96

loss of bowel control

Question 97

cardiac sphincter

Answer 97

closes the esophagus and prevents the contents of the stomach from flowing back into the esophagus

Question 98

malfunction of cardiac sphincter can cause…

Answer 98

If the muscle opens at an inappropriate time, such
as caused by overeating, acid from the stomach
can flow backward into the esophagus, creating
a burning sensation called heartburn.

Question 99

(a) Carbohydrates are broken down to form_____ , which provide your cells with_________ .

Answer 99

sugars; a source of energy

Question 100

Proteins are broken down to form _____ that
your cells use to _____.

Answer 100

amino acids; build proteins

Question 101

Fats are broken down to produce
molecules of _______and_____ that your cells
use to build _______.

Answer 101

fatty acids; glycerol; fats

Question 102

How do the villi and microvilli maximize the
ability of the intestine to absorb nutrients?

Answer 102

The cells on the villi are packed full of tiny hairlike structures called microvilli. This helps increase the surface of each individual cell, meaning that each cell can absorb more nutrients.

Question 103

What is a major function of the large intestine?

Answer 103

absorbs remaining water

Question 104

(a) What is a colonoscopy
(b) Why is it important?

Answer 104

During a colonoscopy, a thin, lighted tube with an attached camera is inserted through the rectum

If an unusual growth is detected, the doctor may choose to perform a biopsy that can remove cancerous cells

Question 105

What does the abbreviation “GERD” stand for?

Answer 105

Gastroesophageal reflux disease (GERD)

Question 106

(a) What is an ulcer?
(b) What causes an ulcer?

Answer 106

-Sores found in the stomach lining, esophagus or the upper small intestine are called peptic ulcers.

-If the stomach lining is broken down it becomes
irritated by gastric acid. The gastric acid can also
spill into other parts of the digestive system and
irritate the tissues of nearby organs.

Question 107

peptic ulcers

Answer 107

Sores found in the stomach lining, esophagus or the upper small intestine are called peptic ulcers.

Question 108

explain why saliva is a very important
bodily fluid

Answer 108

Saliva contains special enzymes that help digest the starches in your food (amylase breaks down starches into sugars, which your body can more easily absorb + lingual lipase, which breaks down fats)

it also moistens the mouth for comfort, lubricates as you chew and swallow, and neutralizes harmful acid

Question 109

Why might an individual with gallbladder
disease have difficulty digesting ice cream?

Answer 109

-produces bile that helps break down fats through hydrolysis and since ice cream is full of fat, it won’t be able to properly digest it