It More Than Just a Gut Feeling
The Digestive System
TAKS
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Objective 2 – The student will
demonstrate an understanding of
living systems and the
environment.
TEKS Science Concepts
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3 The student uses critical thinking and scientific problem solving to make informed
decisions. The student is expected to:
(B) evaluate promotional claims that relate to biological issues such as product labeling
and advertisements;
9 The student knows metabolic processes and energy transfers that occur in living
organisms. The student is expected to:
(A) compare structures and functions of different types of biomolecules such as
carbohydrates, lipids, proteins, and nucleic acids;
(C) investigate and identify the effects of enzymes on food molecules; and
10 The student knows that, at all level of nature, living systems are found within other
living systems, each with its own boundary and limits. The student is expected to:
(A) interpret the functions of systems in organisms including circulatory, digestive,
nervous, endocrine, reproductive, integumentary, skeletal, respiratory, muscular,
excretory, and immune;
(B) compare the interrelationships of organ systems to each other and to the body as a
whole;
11 The student knows that organisms maintain homeostasis. The student is expected
to:
(C) analyze the importance of nutrition, environmental conditions, and physical
exercise on health
Engage
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Watch this digestive system clip with
gold medalist Bonnie Blair from PBS
video Universe Within.
Explore
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Digestion Simulation
As a result of participating in this simulation, you will
learn the structures and the functions of the digestive
system.
Overall Digestive System Function
Breaks up food physically and chemically.
Stores food for a short period of time.
Absorbs the digested foods and passes them into the
circulatory system.
Stores and eliminates undigested food from the body.
Explain
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What are the two main types of
digestion?
Physical/Mechanical: The physical
breakdown of food by non-enzyme
means.
Chemical: The use of enzymes to
breakdown food.
List in Order the Pathways of Food
Through the Digestive System.
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The Mouth
Pharynx
Esophagus
Stomach
Small Intestine
Large Intestine
Rectum
Anus
Oral Cavity
Oral Cavity (Mouth)
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What type of digestion occurs in the mouth?
Both physical and chemical digestion takes place
Tongue – taste
manipulates food
prepares food for swallowing by forming
into a ball (bolus)
Saliva is secreted
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Moistens
Protects mouth from abrasion
Buffer against acids
Kills some bacteria
What enzyme is secreted in saliva?
Salivary Amylase
Enzyme that begins digestion of carbohydrates
Pharynx
Pharynx
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Commonly call the throat
Intersection of GLOTTIS and opening
of the esophagus (gullet) is found here
EPIGLOTTIS is a flap that closes the
glottis when the act of swallowing
occurs (Closes the Trachea)
Esophagus
Esophagus
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Does any digestion occur here?
What is the word that describes the movement
that pushes the food down toward the
stomach?
Connects PHARYNX and the STOMACH
Peristalsis – wave-like contractions of smooth
muscles that push food down toward the
stomach
Cardiac Sphincter – esophagus and stomach
connect
Stomach
Stomach
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J Shaped organ that Stores and digests food.
GASTRIC JUICES - pH of 1-2
Enzyme: pepsin which acts on proteins.
HCl is needed to activate pepsin from its inactive
form pepsinogen.
Gastrin – Horomone secreted to regulate gastric
juices.
Mucus covers the inner lining to prevent the acid
from eating the tissue.
The PYLORIC SPHINCTER or pylorus connects the
stomach to the small intestine and closes off the
stomach at its posterior end.
Small Intestine
Small Intestine
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Most breaking down of macromolecules
occurs here.
6 meters in length
Smaller diameter than the large intestine
Divided into 3 sections:
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Duodenum (first 25 cm)
Jejunum
Ileum
Digestion in Small Intestine
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Acid chyme enters duodenum
Intestinal wall releases a hormone –
SECRETIN-signal pancreas to release a basic
solution to neutralize the acid.
CHOLECYSTOKININ (CCK)- released to
signal the gall bladder to release bile and the
pancreas to release digestive enzymes
ENTEROGESTRONE-secreted to slow down
peristalsis
Absorption and Distribution of
Nutrients
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VILLI – small finger-like projections that
increase the surface area
MICROVILLI – even smaller finger-like
projections on the VILLI
LACTEAL – large lymph vessel found on
each villus (Absorbs FAT)
Capillaries – small blood vessels found on
each villus (Absorbs all nutrients EXCEPT Fat)
Villi and Microvilli
Accessory Organs
Small Intestine Accessory
Organs
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Pancreas, Liver, and Gall Bladder
Add digestive enzymes, juices, and
hormones to the small intestine
These chemicals help break down
protein, fat and carbohydrates
Liver, Pancreas, and Gall
Bladder
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Liver produces bile which is needed to help
digest fat.
Gall bladder stores the bile.
Pancreas (Endocrine and Exocrine function)
produces enzymes need to finish digesting the
main organic foods. It also produces insulin.
Pancreas and Gall Bladder
LIVER
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Regulates the contents of the blood.
All blood contents enter the Liver via the
HEPATIC PORTAL VEIN.
Large Intestine Alone
Large Intestine (Colon)
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Main function of the COLON is to reabsorb water
from the small intestinal material.
CECUM – T junction that connects the colon to
the small intestine
APPENDIX – attached at the end of the cecum.
Stores solid waste in the area called the rectum.
Bacteria (E. coli) live in this area of the body.
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Produce odor, and Vitamin K
Large Intestine w/Small
Elaborate
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Is Terry Better?
You will relate two different types of cloth (Terry and Cotton) to the increased
surface area of the small intestine.
Goldfish Swallowing
You will write a creative story describing what happens to a goldfish in three
distinct parts. Part 1: As it passes your lips to the cardiac sphincter. Part 2:
As it passes through the cardiac sphincter until it reaches the place where the
duodenum becomes the jejunum. Part 3: From the jejunum until it exits the
body.