McKenzie
Health Science 20
NAME:_________________
Lesson 13.2 Anatomy and Physiology of the Digestive System
Objectives:
1. Identify the organs of the digestive system and explain their functions.
2. Describe how food is digested and absorbed.
Saskatchewan Outcome:
“I can analyze the anatomy and physiology of a healthy human”
Saskatchewan Indicators:
“I can describe the anatomy (structure) and physiology (function) of the digestive system”
Before this lesson, try to answer the following questions:
1. Can you live without a gallbladder?
ANSWER:____________________________________________________________________
2. Describe how food is digested and absorbed?
ANSWER:____________________________________________________________________
Key Terms:
 Absorption
 Chime
 Emulsification
 Gastrointestinal tract
 Large intestine
 Rectum
References:
 Notes & handouts
 Textbook Pages: 459 – 478
 Study Guide Pages: 198 – 201






Alimentary canal
Colon
Esophagus
Gingiva
Mechanical breakdown
Small intestine






Chemical breakdown
Defecation
Gallbladder
Ingestion
Propulsion
stomach
McKenzie
Health Science 20
NAME:_________________
13.2 The Digestive System
Health Science 20 - The Digestive System - Chapter Notes

In a nutshell...
The body uses a variety of small molecules (amino acids, fatty acids,
glucose) for its metabolic needs. Food is mechanically and chemically
broken down into these molecules during digestion, after which they can be
taken up by body cells through the separate process of absorption.

Food travels in a one-way path from mouth to esophagus to stomach to
small intestine to large intestine to anus.

Organs and structures in the digestive system are specialized for specific
functions in digestion.

Digestive enzymes are specific hydrolytic enzymes that have a preferred
temperature and pH.

Proper nutrition is necessary to health.

_________________: the mechanical and chemical breaking
down of ingested food into particles, then into molecules
small enough to move through epithelial cells and into the internal environment.

_________________: the passage of digested nutrients from the gut lumen into the blood or
lymph, which distributes them through the body.

_________________: the expulsion of indigestible residues from the body.

During digestion:

_________________ are broken down into ______________,

_________________ are broken down into ______________,

_________________ are broken down into _____________ and _________ _________,

_________________ are broken down into ______________.

Digestion is an ____________________ process. It occurs within the _____________, which runs
from the ____________ to the ___________.

Digestion is achieved through the cooperation of a number of body parts and organ systems, and
its coordination depends on the actions of several key HORMONES.
McKenzie
Health Science 20
NAME:_________________
Mouth: The Grinder
Digestion begins in the mouth!
The mouth receives food, chews it up (mechanical digestion), moistens it (lubricates), and
starts to digest any starch in the food (chemical digestion).
Two main functions:
1) ________________ digestion:
-
Increases __________________________ for chemical digestion
-
Makes the food ______________ and ______________ to swallow.
-
Once food has been chewed => ______________
2) ________________ digestion:
-
_________________________ in saliva breaks down ____________________
-
Salivary amylase is a _______________ enzyme that breaks down ___________
into ______________ (a disaccharide of glucose).
-
Saliva also _______________ the food, making it _______________ to swallow.
-
Three sets of _______________________ that produce saliva
o
________________ (below ears)
o
________________ (below tongue)
o
________________ (under upper jaw)
Swallowing
1.
Swallowing is a ___________ __________ (requires no conscious thought).
2.
the ___________ __________ __________ __________ to cover openings to nose (nasopharyngeal
openings).
3.
___________ __________ __________ __________ under a flap of tissue called the epiglottis, blocking its
opening. When food goes down the "wrong way" it goes into the trachea, and is then coughed back up.
4.
The opening to the Larynx (larynx = “voice box”) is called the “glottis.” This opening is COVERED when the
trachea moves up. It gets covered by a flap of tissue called the EPIGLOTTIS.
This is why you can’t _____________ and ___________ at the same time.
McKenzie
Health Science 20
NAME:_________________
Esophagus: The Chute

When food (BOLUS) is passed through the back of the mouth and swallowed, the first region it
enters is called the ___________, which is simply the region between mouth and esophagus
where ___________ takes place.

food has ______________________ to go ---> down the ______________

Esophagus: a ___________ ___________ ___________that extends from pharynx to stomach.

The inner surface lined with mucus membranes. This layer is
attached by connective tissue to a layer of smooth muscle containing
both circular and longitudinal muscle.

Bolus moves down the esophagus through ___________ (rhythmical
contractions of the esophageal muscles).

Bolus passes the ___________ ___________ to enter the
___________.

Sphincters function like ___________ and prevent ___________ ___________.

Normally, this sphincter prevents food from moving up out of
Esophagus
stomach, but when vomiting occurs, a ___________ ___________
___________causes the sphincter to relax and the contents of the
stomach are propelled outward.
I.e. PUKING = _______________ _______________
McKenzie
Health Science 20
NAME:_________________
Stomach: The Acid Dunk Tank

is a ______________________, ______________________ ___________ that lies on left side of the body
beneath the diaphragm.

can stretch to hold about half a gallon (___________) of solids and/or liquids in an average adult.

___________ ___________ of ___________ contract to churn and mix its contents

“hunger pains” are felt when an empty stomach churns.

The mucus lining of the stomach contains inner ___________ ___________ which produce ___________
___________.

Gastric juice contains _________________ and ___________ (hydrochloric acid).

___________, a hydrolytic enzyme, breaks down proteins into smaller chains of amino acids called peptides

HCl gives stomach a pH of ~3. Highly corrosive. This kills bacteria in food and helps break it down. This is also
the ___________ pH for pepsin

___________ ___________ of ___________ is secreted by the mucosal cells

___________ the stomach from the ___________ acid.

if HCl does penetrate, pepsin starts to digest the stomach lining  ___________

An Ulcer = an ___________ ___________ on the wall of the stomach).

___________ ___________ gastric juice cause ulcers

___________ (excessive nervous stimulation) can cause over-secretion of gastric juices.

#1 cause of ulcers = ___________ _____________ (Helicobacter pylori)
 The bacteria impairs the ability of cells to produce mucus. Most ulcers can now be
cured with antibiotics.

after 2 - 6 hours (depending on the type of food), the food has been turned into a semi-liquid food mass called
___________ ___________

The stomach empties the CHYME into the first part of the small intestine (called the duodenum).

This emptying of the stomach is controlled by the ___________ ___________at the bottom of the stomach.
McKenzie
Health Science 20
NAME:_________________
Small Intestine: The Food Processor

Most ___________ and ___________ of nutrients takes place in the small intestine.

Divided into three zones: the ___________, ___________, and ___________.

is about ___________ meters long (~20 feet),
compared to ___________ meters (~ 5 feet) for
the large intestine.



Liver
The first ___________ cm of small intestine
called the _______________.
The duodenum plays a major role in digestion.
 Receives _____________ from the
___________ and __________.
Stomach
Gall Bladder
Pancreas
Duodenum
Jejunum

These secretions break down
___________ and ___________,

produces ______________ ____________ as well.

These secretions break down other ______________
Illium
the Liver produces ____________which is sent to the duodenum via a ____________ from the
________ ____ ____________ (where bile is ____________).

____________ contains emulsifying agents called ____________ ____________, which break
down fat into smaller ____________ ____________.

____________ sends ____________ ____________into duodenum
through the ____________ duct

the juice contains ____________ and ____________ ____________
____________ (NaHCO3)

NaHCO3 makes the juice ____________ ____________ (pH ~ 8.5).
This is the ____________ pH for pancreatic enzymes.
 It _______________ the acid chyme and make the small
intestine pH basic
Add bile salts
(emulsifier)
Emulsifier coats
outside of droplets
Large Droplets of Fat
Large fat droplets have now been
broken up into smaller fat droplets
McKenzie


Health Science 20
NAME:_________________
pancreatic juice contains ____________ ____________ including:

pancreatic amylase (digests starch to maltose)

trypsin (digests protein to peptides)

lipase (digests fat droplets to glycerol & fatty acids).
Note: the pancreas also has an _______________ function.

produces the hormones ____________ and ____________.

Insulin is a hormone that causes glucose in the blood to be taken up by cells (i.e.
____________ blood sugar).

Insulin and Glucagon are produced by different cells ( cells in “islets of
Langerhans”) in the pancreas than the ones that make pancreatic juice.

Insulin is released directly into the blood, and it travels to target cells throughout the body.

People who don’t produce insulin or enough insulin, or who lack insulin receptors
on target cells, suffer from ______________.

Glucagon works opposite to insulin. Glucagon ____________ blood glucose levels.
McKenzie

Health Science 20
NAME:_________________
walls of the duodenum and small intestine are lined with millions of __________________
____________ that produce juices containing enzymes that ____________ the digestion of protein
and starch.

secretions from the interstitial glands contain digestive enzymes:

peptidases digest peptides to amino acids.

maltase digests maltose (a disaccharide) to glucose.

Other enzymes to digest other disaccharides.
For example, lactase digests lactose (the sugar in milk_.
Comprehensive Summary of DIGESTIVE ENZYMES
 the breakdown of food (fats, carbohydrates, proteins) into molecules small enough to be absorbed requires
the action of specific enzymes.

each enzyme has ____________ where it works, and a ____________ and ______________
range in which it can operate

all are ______________ ___________ that catalyze a reaction of the substrate with __________.

The Principal Digestive Enzymes!
McKenzie

Health Science 20
NAME:_________________
The ____________ of the small intestine is well related to its ____________ of ____________.
1. it is ____________ with
____________ walls to
<-- 20 feet long! -->
____________ ____________
2. surface area further increased
by presence of finger-like projections called ____________
(a single one is called a “villus”. Interstitial glands are at the base of
each villi.
3. villi are lined with columnar cells coated with ____________Each villi
contains blood vessels and lymph vessels (lacteal).
 ____________ takes place across the wall of each villus ---> this can
happen passively or actively. Recall that active transport across cell
membranes requires ATP. The nutrient can now enter the blood or the
lymphatic system, depending on what type it is.

arteriole side of
capillary network
lacteal (absorbs
fats)
venule side of
capillary network
columnar cells
with microvilli
Interstitial Gland
____________ ____________and ____________ are absorbed across the
villi, are recombined into fat molecules in the epithelial cells of the
villus. The fats then move into the ____________ of each villus and
enter the ____________ ____________.

____________ and ____________ ____________ enter the ____________ through the capillary
network.

The blood vessels from the villi in the small intestine merge to form the ____________
____________ ____________which leads to the ____________.
The lining of the small intestine is not smooth; it is long and convoluted.
The convoluted lining
itself,
under
closer
examination, is shown to
consist of millions of
finger-like
projections
called villi (singular =
villus)
Lining of each villus made of columnar epithelial
cells, that have microvilli (folds of cell
membrane) across which nutrients are absorbed.
McKenzie
Health Science 20
NAME:_________________
The Liver: The Filter
 a critically important organ in digestion & homeostasis
FUNCTIONS OF THE LIVER
1. ____________ __________________ from red blood cells to break down products
(bilirubin and biliverdin) which are excreted along with bile salts in bile.
2. Produces ____________, which is stored in the
Underside of liver showing gall bladder
gallbladder before entering the small intestine, where
bile salts emulsify fats.
3. Detoxifies ____________ by removing and
metabolizing poisonous substances.
4. Stores ____________ as ____________ after eating and
breaks down glycogen to glucose to maintain the
glucose concentration of blood between eating
periods.
5. Produces ____________ from the breakdown of amino acids.
6. Makes ____________ ____________ from amino acids.
McKenzie
Health Science 20
NAME:_________________
Large Intestine: The Dehydrator
 consists of ____________ and ____________ (the
rectum is the last 20 cm of the colon). Opening of
rectum is called ____________.
 colon has 3 parts (____________,____________, and
____________)
Main Functions

________________ of _____________from
Transverse
Colon
Ascendin
g Colon
Descendin
g Colon
indigestible food matter (feces)

____________ of certain vitamins

feces also contains bile pigments, heavy metals,
and billions of E. coli.
Rectum
Cecum
Appendix
Anus

Parasites

Provide a valuable service for us.

____________ ____________ some indigestible food

During this process they produce ____________, ____________, and other ____________
____________ that are in turn absorbed by the colon.
Complete the Lesson
1. Read p. 459 – 478 in your textbook
2. Complete the “Check Your Understanding” Questions on p. 462, 466,
470, and 475
3. Correct your “Before this lesson” answers
4. Complete #1-9, p. 478
5. Study Guide pages 198, 200, and 201 (handout)
