Download The Digestive System

Introduction
 The digestive system is
used for breaking down
food into nutrients
which then pass into the
circulatory system and
are taken to where they
are needed in the body.
Introduction
 There are four stages to
food processing:
1. Ingestion: taking in food
2. Digestion: breaking
down food into nutrients
3. Absorption: taking in
nutrients by cells
4. Egestion: removing any
leftover wastes
The Human Digestive System
 Begins when food enters
the mouth.
 It is physically broken
down by the teeth.
 It is begun to be
chemically broken down
by amylase, an enzyme
in saliva that breaks
down carbohydrates.
The Human Digestive System
 The tongue moves the
food around until it
forms a ball called a
bolus.
 The bolus is passed to
the pharynx (throat) and
the epiglottis makes sure
the bolus passes into the
esophagus and not down
the windpipe!
The Human Digestive System
 The bolus passes down
the esophagus by
peristalsis.
 Peristalsis is a wave of
muscular contractions
that push the bolus
down towards the
stomach.
The Human Digestive System
 To enter the stomach,
the bolus must pass
through the lower
esophageal sphincter, a
tight muscle that keeps
stomach acid out of the
esophagus.
The Human Digestive System
 The stomach has folds
called rugae and is a big
muscular pouch which
churns the bolus
(Physical Digestion) and
mixes it with gastric
juice, a mixture of
stomach acid, mucus
and enzymes.
The Human Digestive System
 The acid kills off any
invading bacteria or
viruses.
 The enzymes help break
down proteins and
lipids. Chemical
Digestion.
 The mucus protects the
lining of the stomach
from being eaten away
by the acid.
The Human Digestive System
 The stomach does do
some absorption too.
 Some medicines (i.e.
aspirin), water and
alcohol are all absorbed
through the stomach.
 The digested bolus is
now called chyme and it
leaves the stomach by
passing through the
pyloric sphincter.
The Human Digestive System
 Chyme is now in the
small intestine.
 The majority of
absorption occurs here.
 The liver and pancreas
help the small intestine
to maximize absorption.
 The small intestine is
broken down into three
parts:
The Human Digestive System
1.


Duodenum
Bile, produced in the
liver but stored in the
gall bladder, enters
through the bile duct.
It breaks down fats.
The pancreas secretes
pancreatic juice to
reduce the acidity of
the chyme.
The Human Digestive System
2. Jejunum


The jejunum is where
the majority of
absorption takes place.
It has tiny fingerlike
projections called villi
lining it, which
increase the surface
area for absorbing
nutrients.
The Human Digestive System

Each villi itself has tiny fingerlike projections called
microvilli, which further increase the surface area for
absorption.
The Human Digestive System
3. Ileum

The last portion of the
small intestine is the
ileum, which has fewer
villi and basically
compacts the leftovers
to pass through the
caecum into the large
intestine.
The Human Digestive System
 The large intestine (or
colon) is used to absorb
water from the waste
material leftover and to
produce vitamin K and
some B vitamins using
the helpful bacteria that
live here.
The Human Digestive System
 All leftover waste is
compacted and stored at
the end of the large
intestine called the
rectum.
 When full, the anal
sphincter loosens and
the waste, called feces,
passes out of the body
through the anus.
Liver
 the liver has over 500 functions, four being
fundamental:
 production of bile
 storage of glucose in the form of glycogen ( fat if
glycogen limits exceeded), conversion of galactose and
fructose to glucose
 detoxification of the blood (makes enzymes to break
down toxins; ex: alcohol, caffeine, nicotine, barbiturates,
poisons, excess hormones)
 deamination of amino acids – removing nitrogen,
producing ammonia and eventually urea (excreted by
the kidneys)
Gallbladder
 is lodged in one of the lobes of the liver
 a light muscular bag that stores and releases bile
 why store bile? We eat large quantities of fats at a time,
so having a store of bile is useful but can lead to
problems – bile salts can crystallize in the gallbladder
forming gallstones

back to digestion….
 the combination of hormones and the presence of
certain foods leads to the secretion of pancreatic
enzymes, bile, and intestinal enzymes (maltase, lactase,
sucrase and enterokinase), all of which are active in the
slightly basic pH of the duodenum
 the villi of the small intestine are specialized to absorb
the molecules of digestion:
 large surface area
 transport proteins on the epithelial cells move amino
acids, glucose, water soluble vitamins, etc. by facilitated
diffusion and active transport into the capillary system,
then on to the liver immediately for processing
 electrolytes by diffusion, water by osmosis
 fatty acids and glycerol are absorbed into the epithelial
cells and are repackaged as triglycerides
 being hydrophobic, they are packaged into protein
packs to enable their transport through the body
 the packaged fats are absorbed into the lacteals in the
interior of the villi, and are transported through the
body’s lymphatic system
 fat soluble vitamins will move with fats into lacteals for
absorption in the body
Accessory Organs:
Pancreas
 a soft tubular gland that lies just behind the stomach,
and is connected to the duodenum by two ducts
 has both a exocrine (secretory) and endocrine
(hormonal) function
 its exocrine functions are to secrete digestive enzymes
and sodium bicarbonate to neutralize the stomach acid
and establish a pH of 7.1-8.2 which will not only
neutralize the enzyme pepsin, but activate the
pancreatic enzymes
 Pancreatic Enzymes:
 pancreatic amylase: digest carbohydrates  maltose
 trypsin: protein digestion: peptides  smaller peptides





(activated by enterokinase, secreted by the intestinal
wall)
chymotrypsin: protein digestion: peptides  smaller
peptides (activated by trypsin)
peptidase: peptides  smaller peptides and amino
acids
pancreatic lipase: digests fats into fatty acids and
glycerol
ribonuclease: digests RNA to nucleotides
deoxyribonuclease: digests DNA to nucleotides
 it receives two separate blood supplies
 via the portal vein – bringing freshly absorbed nutrients
from the small intestine
 via the hepatic artery – bringing oxygenated blood from
the lungs/heart
 bile
 each day, the liver secretes between 800 – 1000 mL of
bile
 bile is stored in the gallbladder for release on demand
into the small intestine
 consists of water, bile salts, cholesterol and bile
pigments (made from bilirubin – yellow in colour)
 bile acts as an emulsifier, breaking large fat globules into
small ones, allowing lipase more surface area for
digestion
Digestion and Homeostasis
 The endocrine, nervous,
digestive and circulatory
systems all work together
to control digestion.
 Before we eat, smelling
food releases saliva in
our mouths and gastrin
in our stomachs which
prepares the body for a
snack.
The Hormone Gastrin
Secretions of the Digestive Tract
Secretion
Site of production
Function
saliva
mouth
contributes to starch digestion via salivary
amylase; lubricates the inside of the mouth to
assist in swallowing
mucus
mouth, stomach, small
intestine, and large intestine
protects the cells lining the innermost portion of
the digestive tract; lubricates food as it travels
through the digestive tract
enzymes
mouth, stomach, small
intestine, and pancreas
promote digestion of food masses into particles
small enough for absorption into the
bloodstream
acid
stomach
promotes digestion of protein
bile
liver (stored in gall bladder)
suspends fat in water, using bile salts,
cholesterol, and lecithin to aid digestion of fats in
small intestine
bicarbonate
pancreas and small intestine
neutralizes stomach acid when it reaches the
small intestine
hormones
stomach, small intestine, and stimulate production and/or release of acid,
pancreas
enzymes, bile, and bicarbonate; help to regulate
peristalsis
Digestion and Homeostasis
 A large meal activates
receptors that churn the
stomach and empty it
faster.
 If the meal was high in
fat, digestion is slowed,
allowing time for the fat
to be broken down.
 Hence why we feel fuller
after eating a high fat
meal.
Digestive Disorders
Digestive Disorders
 Disorders of the digestive system and its accessory
organs include:





ulcers,
inflammatory bowel disease,
hepatitis,
cirrhosis,
and gallstones.
 All disorders that affect digestion, including eating
disorders, can seriously damage overall health by
depriving the body cells of the nutrients they need
to survive.
Questions to Answer
 Where are Fat Soluble vitamins absorbed? Where are
the other vitamins absorbed? What are the fat soluble
vitamins?
 Describe the relationship between the organs in the
digestive tract.
 What are the benefits of having stomach stapling?
What are the risks?
 Summarize chemical digestion of macromolecules.
 Explain how glucose levels are affected after meals.
Include the effects of different foods.
Making Healthy Food Choices
Good Nutrition + Exercise = Health
Digestive Summary
 Food passes through the digestive tract—the mouth,
pharynx, esophagus, stomach, small intestine, and
large intestine—during physical digestion.
 The accessory organs—the salivary glands, liver, gall
bladder, and pancreas—supply chemicals that also
contribute to the digestion of food as it passes through
the digestive tract.
 The stomach supplies chemicals to aid digestion as
well as generating physical contractions to physically
break down food.
 The food is eventually liquefied into soluble units that
can pass through cell membranes for transport via the
circulatory system to all the cells in the body.
 The waste materials from the digestive process leave
the body via the large intestine.
Gastritis
Chronic Hepatitis
Cirrhosis
Jaundice
GERD
GERD
GERD
Peptic Ulcer
Peptic Ulcer
Peptic Ulcer
Travel Brochure Project
The Body System Travel Agency has just hired you to give tours through the
Digestive system. Their first task is to create a travel brochure to highlight
the "trendy" spots and exciting activities the systems contain. Also mention
any dangers or precautions that tourists should be aware of when visiting
each system (Diseases and other issues associated with the digestive
system).
• Use a 8x10 piece of paper to make this brochure.
• Include: ALL major parts and functions of digestive system – include 8
places/spots that are a must do activity for the family- ex: spa, beach,
amusement park, museum, ruins, etc…
•Must have at least 3 diseases / issues with digestion to avoid
• Must be in color! Must have pictures!
• May be hand drawn or done on computer
Rubric
 All major parts of digestive system included: 40 points
 Functions of each system included: 40
 At least two diseases/ issues: 10
 Color with pictures: 10