Download Mechanical Digestion in Stomach

The Human Digestive
System
What is digestion?
 The process of breaking down foods
into molecules the cells of the body
can use.
Where does digestion occur?
The gastrointestinal tract
(AKA- alimentary canal)
Muscular tube approx. 9 meters long!
Organs of the Alimentary Canal
and their accessory organs
Mechanical vs. Chemical
Digestion
 Mechanical Digestion= The physical
breakdown of food into smaller pieces
 Chemical Digestion= Breaking the bonds
in food to change the chemical nature of it
Mouth
(Buccal Cavity)
 Mechanical
Digestion
(mastication)
- Teeth break down
food
- Tongue manipulates
food against the hard
palate (bony roof of
mouth) and contains
bumps (papillae) that
provide friction for
moving food around.
- The frenulum
connects the tongue
to the floor of the
mouth.
Mouth cont.
 Chemical Digestion
- Salivary glands that line the mouth produce saliva.
- Saliva moistens food particles, binds them
together, allows tasting, helps to cleanse the mouth
and teeth, and begins carbohydrate digestion.
- Saliva is a mixture of water, mucus and an
enzyme called amylase (breaks down carbs).
- The mucus lubricates and holds the food together
forming a ball called a “bolus”.
INTERESTING FACT:
Halitosis results when food particles accumulate in
the mouth and bacteria flourish. Saliva helps wash
away these food particles.
Three pairs of Salivary Glands
1-1.5 L / day for
digestion
lubrication (swallowing)
moistening (tasting)
 Parotid – lateral
side of face, anterior
to ear – watery
saliva
 Submandibular –
floor of mouth
Sublingual –
inferior to tongue –
thick saliva
Pharynx
 The pharynx connects the nasal and oral
cavities with the larynx and esophagus
and is divided into a nasopharynx (top
portion), oropharynx (middle portion), and
largyngopharynx (bottom portion).
 Sensory receptors in the pharynx sense
food, which triggers swallowing reflexes.
Esophagus
 When food is swallowed it passes
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Peristalsis
the pharynx and into the
esophagus.
The esophagus is a muscular tube
approx. 10 inches long.
What type of muscle lines the
esophagus?
Contractions and relaxations of
these muscles move the bolus
down the esophagus. This process
is called- PERISTALSIS
Peristalsis is very effective= Can
drink upside down
Cardiac Sphincter
• Circular muscle that opens to allow food to pass
from the esophagus into the stomach.
• What if the cardiac sphincter doesn’t work
properly?
 Gastroesophageal reflux disease- GERD
 A condition in which the liquid content of the
stomach regurgitates (backs up or refluxes) into
the esophagus. The liquid can inflame and
damage the lining of the esophagus. The
regurgitated liquid usually contains acid and
pepsin that are produced by the stomach.
Achalasia
 The term achalasia means "failure to
relax" and refers to the inability of the
cardiac sphincter to open and let food
pass into the stomach. Also, the muscle
that lines the esophagus does not contract
properly. As a result, patients with
achalasia have difficulty in swallowing
food.
Stomach
The stomach is divided into the cardiac,
fundus, body, and pylorus regions.
E CS
SI
C
PS
P
B
F
Stomach
• Mechanical Digestion in Stomach
- The stomach is lined with smooth muscle.
This lining is folded and the folds are called
rugae. Smooth muscle of the stomach
twists and turns the stomach, physically
breaking down food.
- If the stomach is empty, then it growls.
This is due to the sounds made by the
contractions of the muscles.
A Real Stomach!!!
Stomach cont.
 Chemical Digestion
- Innermost
lining of the stomach is a mucous
membrane that has openings called gastric pits.
- Gastric pits are the openings through which
secretions are released into the stomach.
- These secretions (called gastric fluid) include:
mucus, pepsinogen (breaks down proteins), and
hydrochloric acid.
- The mucous coating of the stomach protects it
from the acid. If it breaks down = ULCER!
- Food usually stays in the stomach for 3-4
hours.
- The mixture produced from
mechanical/chemical digestion is called chyme
(fats, sugars, vitamins, minerals, and proteins).
Small Intestine
 Pyloric sphincter = Circular muscle that opens to allow
chyme into the small intestine from the stomach. It
allows approx. 5-15 ml in at a time.
 The lengthy small intestine receives secretions from the
pancreas and liver. The small intestine functions to
complete digestion of the nutrients in chyme, absorb the
products of digestion, and transport the remaining
residues to the large intestine.
 If stretched out, the small intestine is 21 feet long! It is
held together by a thin tissue layer called mesentery.
 The 3 parts of the small intestine include:
1st = Duodenum (10 inches)
2nd= Jejunum (8 feet)
3rd= IIleum (13 feet)
Mesentery of Small Intestine:
Liver and Gall Bladder
 Liver
- Large brownnish-red organ to the right of the
stomach
- Makes bile (important in fat digestion)
 Gall bladder
- Stores the bile made by the liver
- Bile travels from the liver to the gall bladder through
the common hepatic duct and cystic duct.
- When chyme is present in the small intestine
(duodenum), the gall bladder releases bile through
the cystic duct to the common bile duct which dumps
into the small intestine at the duodenum.
Human Digestion: Small Intestine
Gall Bladder Removal
 Why?
 Quick video of a removal
Pancreas
 The pancreas secretes pancreatic fluid
into the small intestine (duodenum). This
helps breakdown the chyme.
 Pancreatic fluid leaves the pancreas
through the pancreatic duct. The
pancreatic duct joins the common bile duct
just before it enters the small intestine.
Absorption in
the Small
Intestine
 Digestion products are
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absorbed into the
circulatory system
through blood and lymph
vessels.
The lining of the jejunum
and illeum has
extensions called villi
that increase surface
area.
Inside the villi are
capillaries and lacteal
(lymph vessels).
Fatty acids enter lacteals
Other substances diffuse
into capillaries and
carried to cells of the
body
Celiac Disease
 Celiac disease is when the small intestine
lining (villi) is damaged and absorption of
nutrients is hindered.
 The damage is due to a reaction to eating
gluten, which is found in wheat, barley,
rye, and possibly oats.
 The immune system incorrectly attacks villi
because of the gluten they are absorbing.
Large Intestine
 Once the remaining food enters the large
intestine, it moves toward the anus by
contractions of the smooth muscle in the lining
of the large intestine.
 The large intestine consists of the cecum (pouch
at the beginning of the large intestine), colon
(ascending, transverse, descending, and
sigmoid regions), the rectum, and the anal
canal.
 As the matter moves through the large intestine,
water is absorbed into the capillaries in the
lining. This makes the matter more solid.
 The solid material is called feces.
Large Intestine
What is Feces??
 Feces is composed of undigested material,
water, electrolytes, mucus, and bacteria.
 The color of feces is due to the action of
bacteria on bile pigments.
 The odor of feces is due to the action of
bacteria.
 What can we learn from our poop? Color,
smell, consistency, curvature?
What goes in must come out!
Diverticulitis
 Diverticulosis happens when pouches (diverticula ) form
in the wall of the colon . If these pouches get inflamed or
infected (with feces), it is called diverticulitis. Diverticulitis
can be very painful.
 Doctors aren't sure what causes diverticula in the colon.
They think that a low-fiber diet may play a role. Without
fiber to add bulk to the stool, the colon has to work
harder than normal to push the stool forward. The
pressure from this may cause pouches to form in weak
spots along the colon.
 Diverticulitis happens when feces get trapped in the
pouches (diverticula). This allows bacteria to grow in the
pouches. This can lead to inflammation or infection.
Facts at a Glance
 The average person eats 3 pounds of food
a day. That's 1,095 pounds a year!
 An adult stomach holds 5 cups.
 35 million glands produce acid in the
stomach. The acid can dissolve a razor
blade in one week!
 The body uses energy efficiently. (900
miles to the gallon!)
Our own food breakdown factory!
Why do we need our urinary
system?
• To remove (excrete) metabolic waste
from the bloodstream and carry it out of
the body in the form of urine
– Metabolism: Cells breaking down
compounds for energy
• To regulate the water content in the
body
Functions of the organs of the
human urinary system
 Kidneys- Where blood is filtered and
urine is produced
 Ureter- Narrow tube connected to each
kidney that carries urine to the urinary
bladder
 Urinary bladder- A muscular sac that
stores urine and contracts to release
urine
 Urethra- The tube that carries urine
from the bladder out of the body
Organs of the human
urinary system
Kidney
Renal
vein
Renal
artery
Ureter
Urinary
bladder
Urethra