The process in which food is broken down into smaller molecules that can be absorbed into the body and are usable by cells Five Main Digestive Processes Ingestion Eat Intaking ID: 908739
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Slide1
DIGESTION
Slide2What is digestion?
The process in which food is
broken down
into smaller molecules that can be absorbed into the body and are usable by cells.
Slide3Slide4Five Main Digestive Processes
Ingestion
– Eat;
Intaking of food into Digestive TractMovement – Food travels down digestive tract.
Digestion
– Large molecules
Small molecules (mechanical or chemical).
Absorption
– Transporting digested nutrients to cells in the body.
Egestion
– Removal of materials (waste) from food that the body cannot digest.
Slide5The “Taste Map”: All Wrong
Do you taste different components of taste with different parts of your tongue?
Slide6Tongue Papillae
Circumvallate
papillae
Slide7Taste Test!
You will be tasting flavoured candies. Yummy
Catch! – You have to PLUG YOUR NOSE!
One student = facilitator, other = taster
Facilitator chooses
1
candy (don’t show the taster!), unwrap it while the taster has their eyes closed and put it in their hands.
60 seconds (keep your nose plugged!) – describe sensations and try to determine the flavour of the candy. Guess again after the min is up. THEN unplug your nose... Switch roles and repeat.
**Remember keep the flavour a secret until the end**
Slide8Taste
What is the difference between taste and flavour?
Does smell affect taste?
If your sense of taste is impaired, it is possible your appetite might decrease. What things might decrease your sense of taste?Cigarettes, illness, medications, vitamin deficiencies
Slide9Why do we eat??
Slide10Nutrients!
Body needs energy to do work.
Nutrients include
CarbohydratesProvide energy (growth, warmth, movement
).
Proteins
For growth of cells and
tissues.
Repair of damaged tissues.
Source of energy if carbohydrates and fats
unavailable.
Slide11Nutrients cont…
Fats
Provide energy
Two times that of carbohydrates
Nutrients help
in our growth,
by keeping us healthy,
by repairing our cells and tissues,
by giving us energy.
Slide12Enzymes : their role
Enzymes are used to digest
food.
Carbohydrase / AmylaseCarbohydrates to Simple
sugars.
Protease
Proteins to Amino
acids.
Lipase
Fats to Glycerol and Fatty
acids.
Slide13A) Importance of the Digestive System
Humans/Animals need a digestive system in order to obtain nutrients for energy.
Digestive system will:
E.g. Cracker (starch) Glucose (used by our cells in the body)
Large Complex Molecules
Small, simple molecules
Breaks down
Slide14Anatomy of Digestive System
How long do you think the digestive system is?
From mouth to anus, is on average 6-9 meters in length! (that’s 21-23 feet long)
1) Mouth: 15 cm2) Pharynx: 15 cm3) Esophagus: 35 cm4) Stomach: 30 cm5) Duodenum: 25 cm6) Jejunum: 2.5 meters
7) Ileum: 3 meters
8) Colon: 1.5 meters
9) Rectum: 15cm
*How can such a long system fit into our bodies?!
Slide15B) Organization of Digestive Tract
From mouth to anus, is on average, 6-9 m or 21-23 ft long.
Organs are divided into two categories:
Gastrointestinal Tract (G.I.)Continuous tube from mouth to anus.Includes: Mouth, esophagus, stomach, small intestine, large intestine, rectum, anus.
Accessory Organs
Lie outside the G.I tract.
Produce secretions that help in digesting food.
Include: Teeth, tongue, salivary glands, liver, pancreas, gall bladder, (appendix).
Slide16Food must be mechanically and chemically reduced before it can be absorbed across the intestinal wall.
Slide17Two Types of Digestion
Mechanical Digestion:
The physical break down of food into digestible chunks.E.g. Chewing with teeth.Chemical Digestion: Chemical break down of food to a form that can be absorbed (usually by the blood stream).E.g. Enzymes cleaving substrates.
Slide18Slide19Teeth
Primary teeth vs. secondary teeth
Slide20Anatomy of a Tooth
Slide21Tooth
Enamel –
White outer
part of the tooth. Is mostly made of calcium phosphate, a rock-hard mineral.Dentin – has living cells, is porous, and is like bone (softer than enamel)Pulp – the softer, living inner structure of teeth. Blood vessels and nerves run through the pulp.
Slide22Cementum
– connective tissue (bone like) that binds the root of the tooth to the gums and jawbone.
Crown – area of tooth that is visible (enamel)
Neck – Where the crown meets root. Covered by gingiva (gums)Root – the anchor of the tooth
Slide23Tooth aches
500 species of bacteria inhabit the mouth.
Certain bacteria thrive on sugar, and produce lactic acid which destroys tooth enamel.
Streptococcus mutans
Slide24Teeth Questions
What are three types of teeth? What are they used for?
Why do Cavities Hurt?
Analyzing the teeth of animals is a good indication of their diet. Explain why. SciShow Videos Why do we have baby teeth? Why is flouride good for our teeth?Why do we have to brush our teeth? List the two main reasons.
Slide25Root Canal
https://
www.youtube.com/watch?v=jHHn52KhBkQ
https://www.youtube.com/watch?v=YDs-848-u-U
Slide26Ingestion and mastication
Slide27Mouth (aka Oral cavity)
Only part of the alimentary canal involved in ingestion
Mechanical digestion (chewing) and chemical digestion (enzymes in saliva) start here
Slide28Slide29Tongue
Made up of groups of muscles that run in different directions. This gives the tongue its flexibility.
Mixes food with saliva to form a mass of wet food called a bolus.
Initiates swallowing by pushing bolus towards the pharynx
Slide30Slide31Tongue continued
The top layer of the tongue is covered with a layer of bumps called papillae
Papillae helps grips food and contains taste buds
Slide32Slide33Taste buds
C
an detect the following tastes:
Sweet SaltySour Bitter Umami
Slide34Why is the tongue important in choosing the kinds of food you eat?
Tastes has a homeostatic function
Promotes the intake of nutritious foods that your body needs
Protects you body from possible dangersExample: Natural poisons and spoiled foods tastes bitter
Slide35Babies response to sour taste
http://
www.dailymail.co.uk/news/article-2392574/Photographers-April-Maciborka-David-Wile-capture-toddlers-reactions-trying-lemon-time.html
Slide36Check Your Understanding!
What is the tongue? What function does it perform?
How many different tastes can the tongue detect? What are the tastes?
What kind of homeostatic function does your tongue serve? Explain.
Slide37Salivary Glands
There are three types of salivary glands:
1. Parotid Glands
2. Submandibular Glands3. Sublingual Glands
Slide38Salivary Glands continued
Serous cells produce amylase – splits starch and glycogen into
disaccharides
Slide39Salivary Glands continued
Mucous cells produce mucus – lubrication during swallowing
Slide40The
submandibular
salivary glands
are
the
squirters
used in “
gleeking
”!
Slide41“
Gleeking
”
with
submandibular
gland at base of lingual
frenulum
Slide42Swollen parotid gland
in child with viral
mumps
. This virus can also infect the testes.
Slide43Parasympathetic
innervation
stimulates
salivary gland secretion (anticipation of tasty food).
Sympathetic stimulation
inhibits
normal secretion, which is why
people
who are frightened experience the sensation of a dry mouth.
Slide44Check Your Understanding!
Describe the chemical digestion that occurs in the mouth
Mucus is found in saliva. What might its function be?
Slide45Movement!!
Slide46Swallowing
Voluntary
Tongue pushes bolus to back of throat (Pharynx)
Epiglottis closes off the trachea and food travels down esophagus
Slide47Pharynx
The junction between nasal and oral cavity, part of the throat
Slide48Esophagus
Esophagus is made of
smooth muscle
that becomes stretched to help food bolus move along.Causes a wavelike contraction called PERISTALSIS.
Reverse peristalsis
= Vomiting
Slide49The wall of the
esophagus
contains both skeletal and smooth
muscle.
Slide50Slide51Slide52Can you drink upside down?
Slide53Can you drink upside down?
Questions:
Is gravity needed to make fluids come down the
esophagus?Can we drink while we stand on our head?How does food go down the esophagus into the stomach?
Why did the fluid not flow out of the mouth when drinking upside down?
What is the muscle action called, which pushes food into the stomach?
Slide54Movement cont.
Smooth muscle contractions also move food through the rest of the digestive tract.
Slide55Slide56Movement cont.
Smooth muscle contractions also move food through the rest of the digestive tract.
Slide57Digestion / Absorption
Slide58Sphincter
A sphincter is a ring of muscle that controls the passage of material.
Relaxed = open, Contracted = closed
At the junction of esophagus and stomach is the cardiac sphincter (AKA Lower Esophageal Sphincter). Stops stomach contents from going into esophagus
Slide59At the junction of stomach and duodenum is the pyloric sphincter. Regulates movement of stomach contents from stomach
small intestine.
Slide60Slide61Draw This!
Slide62Heart Burn
Caused by a cardiac sphincter that doesn’t tighten as it should
stomach acid into esophagus
Often
happens when
too much food in the stomach (overeating) or to much pressure on the stomach (obesity, pregnancy)
Certain foods act as a trigger (relaxes the sphincter or causes more acid production
smoking causes both!)
Slide63The Stomach
Site of initial protein digestion and food storage.
Smooth muscle contractions cause ingested food to be crushed, ground, and mixed, liquefying it to form
Chyme
Slide64Gastric Pits
Slide65Gastric Pits
Stomach contains GASTRIC PITS that have
GLANDS
and MUCUS cells.Glands contain:Parietal cells – secrete HCl (hydrochloric acid)Chief cells – secrete pepsinogen, the zymogen (inactive) form of the digestive enzyme pepsin.(Pepsinogen
Pepsin under
low pH)
Slide66Pepsin breaks down proteins into short amino acid chains
Slide67G cells – secretes gastrin, a hormone.
Gastrin stimulates the secretion of
HCl
and aids in stomach motility. It’s released in response to stomach stretching or the presence of proteins in the stomach. It is inhibited by HCl in the stomach. What kind of feedback is this??
Slide68Slide69The J-shaped
stomach
stores food (the
semi-digested
mass is called
chyme
), initiates the digestion of proteins, has only
minimal
absorption, and moves materials on to the small intestine.
Slide70Absorption
Some water, specific vitamins and alcohol
Slide71Stomach Composition
The stomach has four layers that surrounds the space called the lumen.
Mucosa
SubmucosaMuscle layer
Serosa
The stomach has folded membranes on the inside called
Rugae
allows stomach to expand
Slide72Why doesn’t the stomach digest itself?
Mucus cells in the gastric pits secrete a thick layer of mucus which protects the walls of the stomach
also secrete bicarbonate solution which neutralizes stomach acid (acid base reaction)
Slide73Peptic Ulcers
Slide74Peptic Ulcer
Most commonly caused by bacterial infection
Helicobacter pylori
NSAIDS (non-steroidal anti-inflammatory drugs) aspirin and IBProfen
Smoking
Alcohol
Genetics
Slide75A Very Famous Stomach!
Alexis St. Martin, 1822
https://
www.youtube.com/watch?v=pqgcEIaXGME
Slide76Mechanical vs Chemical recap
Mechanical – churning of stomach
Chemical :
HCl denatured proteins and kills ingested bacteriaPepsin begins protein digestion
Slide77Slide78Liver & Gall Bladder
Liver produces Bile
mainly water and some bile salts
Bile is stored in the Gall Bladder the gall bladder absorbs water making the bile more concentratedBile releases into duodenum via bile duct
Slide79Bile Salts
Emulsify Fats (Emulsify -
To
make a suspension of small globules of one liquid in a second liquid in which the first will not mix)
Slide80Bile continued
Mechanical digestion:
Emulsification – bile salts break down fat globules into smaller droplets so that they can be digested by enzymes.
Purpose – To increase surface area!
Slide81Slide82Check your understanding
What is the function of the 2 sphincters in the stomach
What role does each cell in the gastric pit play?
Describe the chemical digestion that occurs in the stomachWhat is the main purpose of bile salts. Explain.
Slide83Other Liver Functions
Regulate blood glucose levels (stores glycogen)
Breakdown and synthesis of lipids and fats
Protein breakdown and amino acid synthesisStores vitamins (A, B12, D) and ironBreaks down hormones, antibiotics, and other toxic substances (detoxifier)Breaks down the by-products of RBC recycling
Note** these are main functions. Liver is thought to do about 500 separate functions
Slide84Gall Stones
Crystalline mass formed from bile pigments, cholesterol, and calcium salts.
Cause severe pain and blockage of bile duct
Slide85Slide86Slide87Liver Cirrhosis
Most commonly caused by alcohol,
hepatits
B, hepatits C, and fatty liver disease. Gradual build up of scar tissue that replaces normal tissueLeads to liver failure
Slide88Ethyl alcohol is toxic to the liver
Slide89Healthy Liver
Slide90Liver cirrhosis
Note extensive scarring
Slide91Cirrhosis of the liver
Chronic alcoholism
will typically lead to damage of the liver characterized by
scarring. The
damaged liver often turns an orange color. This damage of the liver is called “
cirrhosis
”.
Slide92Jaundice
One of the by-products of RBC destruction is bilirubin (yellow color)
The liver filters out bilirubin from blood, and excretes in bile.
If liver is failing, or bile duct is blocked, bilirubin builds up in body, causing jaundice a yellowing of skin and whites of eyes.
Slide93Slide94Slide95Gastrointestinal Disorder Project
So now that you know (almost) a lot about the normal functioning of the digestive system, it’s time to investigate some disorders!
Slide96Plagiarism
Source all the materials you use!
In University if caught plagiarizing you will automatically receive a zero on the assignment with the potential of receiving a failing grade in the course or a suspension from the University!
Slide97http://www.youtube.com/watch?v=yQHx9WEfT-Y&safe=active
Slide98Small Intestine
Small Intestine is 7 meters in length
Three
parts to small intestine:Duodenum – first 25-30 cm. - Area of most digestion.Jejunum Ileum
Slide99When
chyme
enters the small intestine it stimulates the release of secretin and
cholecystokinin by the duodenum walls.Secretin regulates pH inhibits gastric HCl production and stimulates bicarbonate ion secretion (pancreas) Cholecystokinin causes release of bile (gall bladder) and digestive enzymes (pancreas).
Slide100Pancreas
Secretes pancreatic juice into the duodenum
Slide101Slide102Pancreatic juice contains:
Bicarbonate
–
changes pH of chyme from highly acidic (pH 2) to weakly basic (pH 8)
Important pH for pancreatic enzymes to function
Slide103Enzymes
lipase - breaks
down triglycerides into fatty acids and glycerol.
Slide104Protease – to digest proteins
Amylase – to digest carbohydrates
Slide105Insulin
Glucagon
Regulation of
blood glucose levels
Slide106Check your understanding!
What accessory gland produces a secretion with no digestive enzymes
?
What kinds of foods are broken down by the pancreas?Most enzymes are secreted as zymogens (inactive), why do you think that is?
Slide107Check your understanding!
Explain two functions of pancreatic fluid.
Someone recently has had a cholecystectomy, a surgical procedure to remove his gall bladder. Now he must take medication to prevent diarrhea. Why would the removal of the gall bladder cause diarrhea?
Slide108Mesentery
Tissue that supports the intestinal tract.
A double layer of connective tissue in which blood vessels, nerves, lymphatics and other structures are contained.
Slide109Mesentery
Thin walls of small intestine with
blood
supply.
Slide110Slide111Slide112Adhesions
often form following abdominal surgery or after an abdominal infection (peritonitis).
Slide113Slide114Peritonitis
can also follow
a penetrating
abdominal
injury.
Slide115Small Intestine
Made up of three parts:
Duodenum
JejunumIleum
Slide116Slide117Slide118Segmentation
Smooth muscle contractions
in both
directions that mix and further break down contents of small intestine (chyme)Is this mechanical or chemical digestion?
Slide119Absorption
The small intestine absorbs the majority of nutrients
such as
The breakdown products of CarbohydratesProteinFatsVitamins
by active and passive mechanisms
Slide120Intestinal
villi
Slide121Slide122Each
villus
contains blood capillaries and a lymph capillary (lacteal). Each villus is covered with microvilli.
Slide123Villi – tiny, finger-like projections on the walls of the small intestine
Microvilli – “brush border”
further increases surface area
Slide124Within villi structures are blood vessels that carry the absorbed nutrients to the rest of the body
Also contain in the villi are structures called lacteal, which absorbs fats to be delivered into the bloodstream
Slide125The Colon (AKA large intestine)
Slide126Main Functions of the Large Intestine
Water
absorption
Absorption of vitamins produced by bacteriaMass movements (defecation) – removes undigested food
Slide127Chemical Digestion
Indigestible food matter (e.g. cellulose) is digested by enteric
bacteria (ex. E. Coli)
that thrive in the large intestine. These bacteria produce vitamin K and some B vitamins.
Slide128Appendix
Vestigial organ
has lost function but retained structure
However, some scientists now think it does serve a function stores good bacteria to help repopulate gut after infection.
Slide129http://www.flickr.com/photos/moonjazz/3530268320/
Slide130Endoscopic view of appendix
Cecum
Slide131Rectum
Connected to the sigmoid colon of the large intestine
Damp Mass of indigestible food remaining in large intestine is called FECES.
Temporarily stores feces before elimination (egestion)
Slide132Anus
The ending portion of the gastrointestinal tract in which feces (undigested food matter) leaves the body
Anal sphincter controls opening of anus.
Slide133Bowel Movement
Receptors in the walls of the large intestine give the central nervous system (brain) signals when a
bowel movement
is needed.Some substances stimulate the bowel movements like caffeine.
Slide134Defecation
to eliminate
feces.
Slide135Summary
Slide136Digestion Time Summary
Digestion takes different lengths of time depending on the food being consumed. F
or healthy adults, it's usually between 24 and 72 hours.
Mouth
(
20 sec
)
Starch
is digested to maltose by carbohydrase /
amylase.
Esophagus
(
10 sec
)
Muscles squeeze
food along the canal.
Stomach (
2-6 hours
)
Gastric juice mixes
food when stomach churns.
Small intestine (5 hours)
Intestinal juice contains enzymes that complete the digestion process.
Large intestine and anus (min of 24 hours)
Undigested food reaches the large intestine
Lots of water is removed and taken back into the body
Slide137Washing your hands is essential!
(Return to regular notes booklet for this)
BacteriaFood poisoningParasitesWorms (Tapeworms)* All can be transferred through the mouth!
Slide138Slide139The Bacteria in your Gut?
Good, bad or ugly?
Good √
E.coli helps you digest food that you could not digest otherwise.
Bad √
The bacteria that help you out, also produce
flatulence
as a by-product. Gas is a normal part of digestion.
Ugly
√
Some bacteria cause
food poisoning
, resulting in severe stomach cramps, vomiting and diarrhea.
Slide140Slide141More important stuff...
Our bodies make two hormones that contribute to homeostasis.
GASTRIN: Releases gastric juice (
HCl) and relaxes gastric sphincter.SECRETIN: Help release bicarbonate ions that neutralize HCl.Our pancreas also helps with homeostasis in regulating blood glucose.
Slide142Slide143Insulin and Glucagon in Digestive System
Two hormones secreted by pancreas.
Work with liver to control level of glucose in body (blood).
Insulin released after meal allows cells to become permeable to glucose. Excess glucose stored by liver as glycogen.
Can change back to
glucose
if blood glucose becomes too low Glucagon