Download Biology 12 Human Biology – The Digestive System Chapter 21

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 main sites of physical digestion in your body?
Mouth is the first with teeth breaking food into small pieces.
Stomach breaks lumps of food by the muscle contraction in three different directions
_Bile separates fat particles from each other – called emulsification.
What is the main site of chemical digestion in your body? First section of small intestine called
duodenum.
Where does most absorption occur? Last section of small intestine absorbs nutrients and the
large intestine absorbs water and vitamins.
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.
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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?
______________________________________________________________________________
Biology 12: Digestive system
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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 oesophagus 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?
___________________________________
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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?
The pancreas secretes bicarbonate which neutralises the acidic gastric juices.
Where is bile
i) made? _____Liver_______
ii) stored? Gall bladder
iii) mixed with food? _____duodenum _____
What does bile do? Breaks chunks of fat and oil into smaller droplets.
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The pancreas produces a juice pancreatic juice, which contains four important enzymes; name
the enzyme which hydrolyzes:
i) starch ____pancreatic amylase___to produce more disaccharides. _______
ii) protein ___trypsinogen is activated to form _trypsin __to produce dipeptides
or short polypeptides ______
iii) fat (lipids) ______lipase__to produce fatty acids and glycerol__
iv) nucleic acids ________nuclease___to produce nucleotides______
This table summarizes the enzymes that hydrolyze polymers in the small intestine:
Give two ways that the small intestine is adapted for digestion?
1. Large surface area from which enzymes are secreted. ________
2. Smooth muscle layers contract to facilitate peristalsis to force food through the small intestine.
As a result of digestion (hydrolysis) what are the following foods finally broken down into?
i) starch __monosaccharides - glucose_, fructose and galactose________
ii) protein ___________amino acids
iii) fat __________fatty acids and glycerol
iv) nucleic acids _______nucleotides_and finally nitrogenous bases, pentose
sugars and phosphates.
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Digestion in the small intestine takes place in the first section called the duodenum.
Absorption of nutrients takes place in the rest of the small intestine: Why must food be digested
before it can be absorbed?
__________The food molecules must be small enough to move through the epithelial lining of
the small intestine and into the bloodstream and then into the tissues of the body.
Give six ways in which the wall of the small intestine is adapted to absorb digested food.
1. Villi and
2. micro villi increase surface area for absorption
3.
4.
5.
6.
7.
The fold in the wall of small intestine increase the surface area
The small intestine is very long.
Well supplied by blood capillaries to collect the nutrient molecules.
Lined with mucous to protect the epithelium from chemicals
Smooth muscle facilitates peristalsis.
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8. What is the main function of the colon? Large Intestine
1. Absorption of water.
2. Absorption of vitamins and minerals (potassium, iron, magnesium, manganese, calcium,
iodine, sodium, zinc)
3. Production of vitamins. For example vitamin K.
_____________________________________
Why is roughage (or dietary fibre - cellulose) important in the human diet?
1. Provides bulk for elimination of digestive waste
2. Provides nutrient for vitamin producing bacteria.
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?
_________Produce vitamin K necessary for blood clotting. _______
_produce folic acid - necessary for a healthy nervous system
Produce B vitamins
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?
___The liver filters the blood and
detoxifies alcohols, drugs such as
painkillers, amphetamines, chemicals such
as preservatives, colorants. _Smooth
Endoplasmic reticulum detoxifies the
blood. ___
b) nutrients such as amino acids and
glucose picked up from the intestine?
__Excess Glucose is converted to
glycogen by insulin and stored in liver or goes on to muscles via blood stream. Amino acids may
be processed in the liver or continue in the blood stream. The hepatic portal vein carries blood
from the small intestine to the liver. __
c) iron and fat-soluble vitamins (A, D, E, K, and B12)?
____The liver stores these.
d) plasma proteins?
_The liver produces plasma proteins, blood proteins, eg. Fibrinogen, globulins and albumins. Fibrinogen
for blood clotting. Globulins for immunity and albumin to maintain osmotic pressure in the blood.
Also called serum 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:
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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? __Ammonia_
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?
_Blood carries the urea to the kidneys where it is excreted as part of the urine.
______________________________________________________________________________
_________________________________________________________________________
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. Bile salts are produced from cholesterol and they emulsify fats into smaller droplets to
increase surface area for enzyme breakdown
2. Bile pigments are produced from the haemoglobin of old red blood cells. (bilirubin)
Bilirubin count is measured in newborns to monitor the activity of their liver.
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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
Pepsin
(a protease)
Trypsin
(a protease)
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
Polypeptides
dipeptides
pancreas
secretes
bicarbonate
to
neutralise
acidic
chime so
that
trypsinogen
converts to
trypsin
Lipase
Pancreatic
Amylase
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Nuclease
Name of
enzyme
Name of
Secretion
Name of
Related
Gland
Peptidases
Location
of Gland
Substrate
Product
Notes
dipeptides
Maltase
From the two lists below, match each structure with its correct function.
__c___ Salivary glands
a. produces enzymes which pass into the duodenum
__e___ esophagus
b. controls the passing of feces
___j__ stomach
c. produce saliva
__h___
pyloric sphincter
__g___
duodenum
__k___
small intestine
d. is where most water is absorbed
e. carries food from the mouth to the
stomach
f. stores bile
__l___ bile duct
g. receives juices from the gall bladder and
pancreas
___a__ pancreas
h. controls the amount of food leaving the stomach
__f___ gall bladder
i. stores waste feces for several hours
__d___
colon
Biology 12: Digestive system
j. produces hydrochloric acid
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__i___ rectum
k. is where most digested food is absorbed
__b___ 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?
It secretes digestive enzymes which reach the duodenum via the
pancreatic duct. Exocrine glands have ducts. This allows enzymes
and bicarbonate to be secreted into the duodenum.
What do we mean when we say that the pancreas is an endocrine gland?
Endocrine glands are ductless and the pancreas secretes insulin as
well as glucagon directly into the blood stream via capillaries that
flow through it.
What is the source gland for insulin? (ie. Which endocrine gland produces insulin?)
___The pancreas and the cells in it that secrete insulin are called the
Islets of Langerhans made up of specialised cells called beta cells. ___
Biology 12: Digestive system
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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:
What is the STIMULUS for the release of the insulin? __increase in blood glucose
level_____
Where are the RECEPTOR cells? ___Beta cells in the pancreas____________
What is the CONTROL CENTRE? The liver because it takes up the glucose and
converts it to glycogen. The overall control of all hormone secretion occurs in the
hypothalamus in the brain.
What are the EFFECTORS and what do they do?
The liver and body cells (mainly muscle) which take up the glycogen for storage.
________________________________________________________________________
_____
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What is the RESPONSE? _____Insulin secretion increases to convert glucose to
glycogen. __
Why do we refer to this process as NEGATIVE FEEDBACK?
__As soon as the insulin increases the glucose level will drop and if it
drops too low then glucagon will be secreted by the alpha cells to
convert glycogen back to glucose.
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?
__By converting glycogen back to glucose until the optimum level for glucose in the
blood is 100mg/ 100ml
If the pancreas does not secrete enough insulin, the person has _Diabetes 1or type I__.
This condition is treated with __insulin injections. _____________.
If the body secretes enough insulin, but the body cells do not respond to the insulin, the
person has ____Diabetes II or Type II____. This condition is treated with
______controlled diet.
In both types of diabetes, the person’s urine contains large quantities of
____glucose____.
Draw a graph to
combined effects
glucagon on the
in your blood over
Biology 12: Digestive system
show the
of insulin and
level of glucose
time:
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