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The Digestive System
Chapter 15
15.1
Functions: mechanical and
chemical breakdown of food
*absorption of nutrients
Consists of alimentary canal
and accessory organs
Wall of the Alimentary Canal
15.2 Characteristics of the Canal
1. Mucosa - protects tissues and carries absorption
2. Submucosa - glands, blood vessels, nerves
3. Muscular Layer - smooth muscle tissue, circular &
longitudinal fibers, pushes food (PERISTALSIS)
4. Serosa (serous layer) - visceral perioneum, outer covering
of the tube, lubricates surfaces (serous fluid)
Mixing Movements
Mixing Movements – rhythmic contractions that mix food
with digestive juices
Propelling Movements – rings of muscles contract and
relax to push food down the canal (PERISTALSIS)
Anatomy of the mouth
• Mouth – begins digestion by reducing size of
particles (chewing) and mixing with saliva
• Tongue – moves food during chewing, connects
to the floor of the mouth via the frenulum,
contains papillae (taste buds)
• Palate – forms roof of oral cavity (hard and soft),
uvula at back of the mouth
• Palatine tonsils – back of the mouth/throat,
organs that protect against infection
• Teeth – primary vs. secondary teeth;
incisors, cuspids, bicuspids (premolars),
molars
Teeth
Incisors
Cuspid (canine)
Bicuspids
Molars
Anatomy of the Mouth
Anatomy of a Tooth
• Crown – projects above the gums
• Root – anchored to the alveolar
process of the jaw
• Enamel – made of calcium salts,
hardest substance in body (outer
surface)
• Dentin – similar to bone, surrounds
tooth’s central cavity
• Blood vessels and nerves extend
through the tooth via the root canal
Tooth Decay
METH
MOUTH
ROOT CANAL
Salivary Glands
Serous cells produce amylase –
splits starch and glycogen into
disaccharides
Mucous cells produce mucus –
lubrication during swallowing
1. Parotid Glands
2. Submandibular Glands
3. Sublingual Glands
Pharynx
• Pharynx – nasal and oral cavitiesnasopharynx, oropharynx,
laryngopharynx
Esophagus
• Esophagus – moves to the
stomach, penetrates the
diaphragm at the esophageal
hiatus
• Lower esophageal sphincter
(cardiac sphincter) - prevent
food and chemicals from moving
up out of stomach
STOMACH MUSCLES:
• J-shaped, pouchlike organs that hangs inferior to the diaphragm, 1 liter
capacity
• 3 sets of stomach muscles: longitudinal, oblique, circular
Greater and Lesser Curvature
Stomach
Four main parts of the
stomach
1. Cardiac (esophageal opening,
cardiac sphincter)
2. Fundic (temporary storage
area, lies slightly above the
cardiac region)
3. Body (central area of the
stomach)
4. Pyloric (pyloric sphincter controls emptying of the
stomach into the sm.
Intestine)
Stomach Lining
• Lining of the stomach is a mucous membrane – with small openings called
gastric pits, containing gastric glands
• Gastric Juice - contain enzymes that break down food
– pepsin
• Chyme – paste of food molecules after its been broken down by the
movement of stomach and gastric juices, it is released from the pyloric
sphincter valve into the first portion of the small intestine – duodenum
• Rugae – folds within the stomach, increase surface area
Mucus prevents stomach
from digesting itself
PANCREAS
• Has endocrine and exocrine functions
• Secretes pancreatic juice as well as
insulin to break down sugars
• Pancreatic juice – digests fats, breaks down
nucleic acids into nucleotides
Liver
BILIARY SYSTEM – functions to create bile used in
digestion; liver, gall bladder and ducts
LIVER- has large right lobe and small left lobe
Hepatic portal vein – delivers blood to the liver
Liver - ducts and vessels
• Hepatic portal vein – delivers blood to the
liver
Liver Functions
• Functions:
• maintains normal concentration
of blood glucose
• breakdown of lipids and fats
• protein metabolism (forming
urea synthesizing plasma
proteins such as clotting factors,
converting amino acids)
• stores iron and vitamins
• destroys damaged red blood cells
• removes toxic substances from
the blood
• secretes bile
Remember Bili Lights?
Using bili lights is a therapeutic procedure performed on newborn or
premature infants to reduce elevated levels of bilirubin. If blood levels
of bilirubin become too high, the bilirubin begins to dissolve in the body
tissues, producing the characteristic yellow eyes and skin of jaundice.
Bile – yellowish-green liquid
secreted from hepatic cells (when
bile pigments build up in blood,
skin turns green, a condition called
jaundice).
The hepatic duct joins the cystic
duct to form the common bile duct,
which empties into the duodenum
Bile aids in digestion, bile salts
break down fat globules into
smaller droplets – emulsification
Small Intestine
*tubular organ that extends from the
pyloric sphincter, many loops and coils,
fills much of the abdominal cavity
*receives secretions from the pancreas and
liver, completes digestion of nutrients and
chime, absorbs
1. Duodenum - first part of the small
intestine
2. Jejunum – second part, ~2.2 m
3. Ilium – third part, longest ~3.3 m
*jejunum and ilium are continuous
Small Intestine cont.
• Mesentery – supports the coils of the
small intestine, contains blood
vessels to carry nutrients away
• Greater Omentum – peritoneum
membrane that drapes like an apron
over parts of the system
Intestinal Villi – increase surface
area for absorption
*the main function of the small
intestine is to secrete chemicals to
break down food and carry away these
nutrients in the blood (absorption)
Greater Omentum
a "curtain-like" membrane that covers the
intestines, stores fat and lays like a drape
Greater Omentum
Large Intestine
1. Cecum – beginning of the large
intestine, pouchlike, closed end
called the vermiform appendix
(ileocecal valve)
2. Colon – ascending / transverse /
descending / sigmoid
3. Rectum – stores waste before it
is expelled from the body
4. Anal canal - ends in the anus,
muscular sphincter which controls
the exit of waste
Function of Large Intestine
• Functions –
• secretes mucus to protect the wall against abrasion;
• re-absorbs water and passes along material that was not
digested;
• contains intestinal flora (bacteria to break down cellulose, also
produce intestinal gas)
Mass movements – large portions of the colon contract to move
material through it, 2-3 times a day usually after eating
The main job is
WATER
REABSORPTION...
How to Make Fake Poop...
LABEL THIS!
1. esophagus
2. liver
3. stomach
4. pyloric sphincter
5. duodenum
6. pancreas
7. jejunum
8. ileum
9. cecum
10. appendix
11. ascending colon
12. descending colon
13. sigmoid colon
14. anus
Nutrition
Disorders of the Digestive System
GERD
Gastroesophageal
reflux disease
Dysentery or Diarrhea
HEPATITIS A, B, C
Hepatitis A is caused by eating food and drinking water
infected with a virus called HAV. While it can cause swelling
and inflammation in the liver, it doesn't lead to chronic, or life
long, disease. Almost everyone who gets hepatitis A has a full
recovery, but may need hospitization
Hepatitis B is caused by the virus HBV. It is spread by contact
with an infected person's blood, semen, or other body fluid.
And, it is a sexually transmitted disease (STD).
Information on Hepatitis B
Some people never develop symptoms, others develop chronic
symptoms that stay with them their whole life.
Hepatitis C is caused by the virus HCV. It is spread the same
way as hepatitis B, through contact with an infected person's
blood, semen, or body fluid (see above).
Like hepatitis B, hepatitis C causes swelling of the liver and
can cause liver damage that can lead to cancer. Most people
who have hepatitis C develop a chronic infection. This may
lead to a scarring of the liver, called cirrhosis.
Blood banks test all
donated blood for
hepatitis C, greatly
reducing the risk for
getting the virus from
blood transfusions or
blood products.
Crohn’s Disease
IBS - Irritable Bowel Syndrome
STOMACH ULCERS
Lactose
Intolerance
Inability to digest
milk, can cause
stomach upset
Appendicitis
Hernia
intestines
poke through
abdominal
muscles
When people with celiac
disease eat foods or use
products containing gluten,
their immune system responds
by damaging or destroying villi
Without healthy villi, a person
becomes malnourished, no
matter how much food one
eats.
Gallstones (Cholelithiasis)
Gallstones are made from cholesterol and other
things found in the bile. They can be smaller than a
grain of sand or as large as a golf ball.
Gastric Bypass Surgery
Colon Cancer
Colonoscopy is a screening technique to detect cancer.
See Katie Couric's Colonoscopy