Biology 12
Human Biology – The Digestive System Chapter 21
Vocabulary
absorption, anaerobic bacteria, anus, appendix, bile, capillary, cardiac sphincter, chemical
digestion, digestive enzyme, digestive tract, duodenum, emulsification, epiglottis,
esophagus, gall bladder, gastric juice, hydrochloric acid (HCl), insulin, intestinal juice,
lacteals, large intestine (colon), lipase, liver, maltase, microvillus, nuclease, pancreas,
pancreatic amylase, pancreatic juice, pepsin, pepsinogen, peptidase, peristalsis, pH,
pharynx, physical digestion, protease, pyloric sphincter, rectum, salivary amylase,
salivary gland, salivary juice/saliva, small intestine, sodium bicarbonate, stomach,
swallowing, trypsin, villus
It is expected that students will:
C1
Analyse the functional inter-relationships of the structures of the digestive system
C1.1
C1.2
C1.3
C1.4
C1.5
C1.6
identify and give a function for each of the following:
– mouth
– tongue
– teeth
– salivary glands
– pharynx
– epiglottis
– esophagus
– cardiac sphincter
– stomach
– pyloric sphincter
– duodenum
– liver
– gall bladder
– pancreas
– small intestine
– appendix
– large intestine (colon)
– rectum
– anus
describe swallowing and peristalsis
identify the pancreas as the source gland for insulin, and describe the function of
insulin in maintaining blood sugar levels
list at least six major functions of the liver
explain the role of bile in the emulsification of fats
describe how the small intestine is specialized for chemical and physical digestion
and absorption
Biology 12: Digestive system
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C1.7
C1.8
C1.9
C2
describe the structure of the villus, including microvilli, and explain the functions
of the capillaries and lacteals within it
describe the functions of anaerobic bacteria in the colon
demonstrate the correct use of the dissection microscope to examine the various
structures of the digestive system
Describe the components, pH, and digestive actions of salivary, gastric, pancreatic,
and intestinal juices
C2.1
C2.2
C2.3
C2.4
C2.5
C2.6
relate the following digestive enzymes to their glandular sources and describe the
digestive reactions they promote:
– salivary amylase
– pancreatic amylase
– proteases (pepsinogen, pepsin, trypsin)
– lipase
– peptidase
– maltase
– nuclease
describe the role of water as a component of digestive juices
describe the role of sodium bicarbonate in pancreatic juice
describe the role of hydrochloric acid (HCl) in gastric juice
describe the role of mucus in gastric juice
describe the importance of the pH level in various regions of the digestive tract
Biology 12: Digestive system
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This diagram illustrates the main stages of digestion:
What is the difference between physical and chemical digestion? _________________________
______________________________________________________________________________
______________________________________________________________________________
What are the two main sites of physical digestion in your body?
_____________________________________________________________________________
What is the main site of chemical digestion in your body? ______________________________
Where does most absorption occur? ________________________________________________
Biology 12: Digestive system
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During chemical digestion, polymers are hydrolyzed to monomers before they can be absorbed
into the blood. Label the following diagram to show the hydrolysis of the four main groups of
organic polymers:
Biology 12: Digestive system
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Label the parts of the human digestive system on the following diagram:
mouth, salivary glands, pharynx, epiglottis, esophagus, cardiac sphincter, stomach, pyloric
sphincter, duodenum, liver, gall bladder, pancreas, small intestine, appendix, large intestine
(colon), rectum, anus.
Biology 12: Digestive system
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Here is a diagrammatic layout of the digestive system. Label the various parts.
mouth, salivary glands, esophagus, cardiac sphincter, stomach, pyloric sphincter, duodenum,
liver, gall bladder, pancreas, small intestine, appendix, large intestine (colon), rectum, anus.
Biology 12: Digestive system
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https://www.youtube.com/watch?v=b20VRR9C37Q overview of digestion
Digestion in the mouth
Mechanical digestion involves
______________________________________________________________________________
_____________________________________________________________________________
Chemical digestion in the mouth involves ___________________________ ________________.
Saliva contains water together with two other important substances. What are they?
__________________________________________________________________
What are the main functions of saliva? (3)
__________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
http://www.factmonster.com/dk/encyclopedia/mouth
Biology 12: Digestive system
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The following diagram illustrates the stages in the swallowing reflex. Label the following
structures:
tongue, nasal cavity, pharynx, glottis, epiglottis, trachea, esophagus, esophageal
sphincter, bolus of food
Indicate where on the diagram peristalsis is taking place.
http://www.d.umn.edu/~mmizuko/video/whole.mov
What normally keeps the esophagus closed when you are not swallowing?
______________________________________________________________________________
What prevents food from entering the trachea when you swallow?
______________________________________________________________________________
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This diagram illustrates the passage of food from your throat to your stomach and through the
intestines. Describe this process:
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
Label the diagram:
Biology 12: Digestive system
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What do we call the lump of food that travels down the esophagus and enters the stomach?
______________________________________________________
What is the function of the cardiac sphincter? __________________________________
_______________________________________________________________________
What is the function of the pyloric sphincter? __________________________________
_______________________________________________________________________
Approximately how long does food stay in the stomach? _____________ hours
Name one digestive enzyme produced by the stomach wall, and the type of food substance it
helps to break up?
__________________________________________________________________
The stomach also produces acid. What is this acid for?
__________________________________________________________________
__________________________________________________________________
How is the stomach wall protected from the acid?
__________________________________________________________________
How does the muscle in the wall of the stomach help digestion?
__________________________________________________________________
__________________________________________________________________
What do we call the material that leaves the stomach and enters the duodenum?
________________________________
Biology 12: Digestive system
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Biology 12: Digestive system
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Label this
diagram
showing the
organs
associated
with the first
part of the
small
intestine:
The digestive enzymes of the small intestine work best in alkaline conditions; how, therefore, is
the acid from the stomach neutralised when it enters the duodenum?
__________________________________________________________________
__________________________________________________________________
Where is bile
i) made? _______________________________________
ii) stored? ________________________ ______________
iii) mixed with food? ________________________ _____
What does bile do? _______________________________________________
__________________________________________________________________
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The pancreas produces a juice which contains four important enzymes; name the enzyme which
hydrolyzes:
i) starch ______________________________________________
ii) protein _____________________________________________
iii) fat ________________________________________________
iv) nucleic acids _______________________________________
This table summarizes the enzymes that hydrolyze polymers in the small intestine:
Give two ways that the small intestine is adapted for digestion?
______________________________________________________________________________
______________________________________________________________________________
As a result of digestion (hydrolysis) what are the following foods finally broken down into?
i) starch ____________________________________________________
ii) protein __________________________________________________
iii) fat ______________________________________________________
iv) nucleic acids ______________________________________________
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Absorption of nutrients takes place in the rest of the small intestine: Why must food be digested
before it can be absorbed?
__________________________________________________________________
__________________________________________________________________
Give six ways in which the wall of the small intestine is adapted to absorb digested food.
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
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What is the main function of the colon? ____________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
Why is roughage (or dietary fibre - cellulose) important in the human diet?
______________________________________________________________________________
______________________________________________________________________________
The large intestine (colon) contains a very large population of anaerobic bacteria. In fact 1/3 of
your feces is bacteria. E. coli is a common bacterium in your colon. Your body actually has more
bacterial cells in and on it than it has human cells! What are some benefits of these bacteria to
your body?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
Annotate this diagram:
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How does the liver act as the ‘gatekeeper of the blood’ with respect to:
a) toxins such as alcohol picked up from the intestine?
__________________________________
__________________________________
__________________________________
__________________________________
__________________________________
__________________________________
b) nutrients such as amino acids and
glucose picked up from the intestine?
__________________________________
______________________________________________________________________________
______________________________________________________________________________
c) iron and fat-soluble vitamins (A, D, E, K, and B12)?
______________________________________________________________________________
d) plasma proteins?
______________________________________________________________________________
__________________________________________
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Why is this system called ‘hepatic portal’ and what is its value to the successful functioning of
the organism?
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Annotate this diagram that shows the relationship between the liver and the small/large intestines
with the associated blood vessels:
Biology 12: Digestive system
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The liver can convert amino acids into glucose if glucose levels are low. What toxic nitrogenous
waste molecule is produced from the deamination of the amino acids? __________________
The liver then converts the ammonia into another nitrogenous waste called urea. Which is more
toxic, ammonia or urea? __________________________ by how much? _________________
How does the body rid itself of the urea produced by the liver and other body cells?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
The liver also produces bile, which it sends to the gall bladder for storage prior to secreting it
into the duodenum. What are the two major components of the bile, and what is the main
function of each?
1. ___________________________________________________________________________
______________________________________________________________________________
2. ___________________________________________________________________________
______________________________________________________________________________
Biology 12: Digestive system
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Complete the following table of digestive glands and their secretions:
Name of
enzyme
Salivary
Amylase
Name of
Secretion
Saliva
Name of
Related
Gland
Salivary
Glands
Location
of Gland
3 separate
pairs of
glands;
beneath
tongue,
beneath
lower jaw,
side of face
in angle of
jaw
Substrate
Starch
Product
Maltose
Notes
-functions
best at
neutral pH
-saliva also
contains
water and
mucus for
lubrication
Pepsin
(a protease)
Trypsin
(a protease)
Lipase
Pancreatic
Amylase
Nuclease
Biology 12: Digestive system
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Name of
enzyme
Name of
Secretion
Name of
Related
Gland
Location
of Gland
Substrate
Product
Notes
Peptidases
Maltase
From the two lists below, match each structure with its correct function.
_____ Salivary glands
a. produces enzymes which pass into the duodenum
_____ esophagus
b. controls the passing of feces
_____ stomach
c. produce saliva
_____ pyloric sphincter
d. is where most water is absorbed
_____ duodenum
e. carries food from the mouth to the stomach
_____ small intestine
f. stores bile
_____ bile duct
g. receives juices from the gall bladder and
pancreas
_____ pancreas
h. controls the amount of food leaving the stomach
_____ gall bladder
i. stores waste feces for several hours
_____ colon
j. produces hydrochloric acid
_____ rectum
k. is where most digested food is absorbed
_____ anus
l. takes bile from the gall bladder to the duodenum
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Glucose Homeostasis
What do we mean when we say that the pancreas is an exocrine gland?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
What do we mean when we say that the pancreas is an endocrine gland?
______________________________________________________________________________
______________________________________________________________________________
What is the source gland for insulin? (ie. Which endocrine gland produces insulin?)
______________________________________________________________________________
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The set point for blood glucose is about 100 mg/100 mL of blood. This is the concentration that
the body tries to maintain. It does this by a process of NEGATIVE FEEDBACK.
Study the following negative feedback diagram to see how insulin affects glucose homeostasis:
Biology 12: Digestive system
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What is the STIMULUS for the release of the insulin? _________________________________
Where are the RECEPTOR cells? _________________________________________________
What is the CONTROL CENTRE? _______________________________________________
_____________________________________________________________________________
What are the EFFECTORS and what do they do? ____________________________________
_____________________________________________________________________________
_____________________________________________________________________________
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What is the RESPONSE? __________________________________________________
Why do we refer to this process as NEGATIVE FEEDBACK?
________________________________________________________________________
________________________________________________________________________
If the blood glucose level drops too low (for example, after you have not eaten for a
while), how does your body bring the level back up to the SET POINT again?
________________________________________________________________________
________________________________________________________________________
If the pancreas does not secrete enough insulin, the person has _____________________.
This condition is treated with _______________________________________________.
If the body secretes enough insulin, but the body cells do not respond to the insulin, the
person has ____________________________________. This condition is treated with
__________________________________________________________. In both types of
diabetes, the person’s urine contains large quantities of __________________________.
Draw a graph to show the combined effects of insulin and glucagon on the level of
glucose in your blood over time:
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