Transcript Digestion - POLYTECH High School

From Intake to Output
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The body cannot use food in its original form
◦ The pieces are too large
◦ Some foods, such as fats, cannot be absorbed by
the bloodstream
◦ Overall foods are too complex for the body to use
without being broken down first
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The process of digestion is:
◦ Physical or mechanical – teeth, chewing, peristalsis
◦ Chemical – enzymes
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Alimentary canal
◦ An approximately 30-foot long tube running from
the mouth to the anus
◦ Includes the mouth, throat, esophagus, stomach,
small intestine, large intestine, and anus
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Accessory organs
◦ Aid the digestive process by reducing food
mechanically and chemically to a simple form that
the body can use
◦ Includes the teeth, tongue, salivary glands,
pancreas, liver, and gallbladder
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Mouth →
Pharynx →
Esophagus →
Stomach →
Small intestine →
Large intestine →
Rectum →
Anus
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Primary role – to help digest food by reducing
its size through chewing (physical digestion)
 Also aids in chemical digestion by mixing food with
saliva, which contains enzymes
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The mouth moves food to the back of the
throat; called the pharynx
 At this point a cartilaginous lid called the epiglottis
closes over the larynx to keep food out of the trachea
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Food passes through the pharynx into the
esophagus
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A food delivery tube that descends through
the mediastinum and the diaphragm into the
stomach
Swallowing moves the food down the
esophagus to the stomach
A sphincter muscle is located where the
esophagus joins the stomach
◦ This muscle opens to allow food to enter the
stomach
◦ It then closes to prevent the food and stomach acid
from flowing back up the esophagus
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Primary role – Storage and to continue
reducing the size of the food
◦ The stomach goes through contractions of its
smooth muscles in order to grind food into smaller
and smaller particles
◦ Acid, mucous, and enzymes are introduced in the
stomach
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The stomach moves the finer food particles to
the pyloric region of the stomach, which
pushes it to the small intestine
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A coiled tube about 22 feet long where a
majority of the digestion takes place
◦ Broken into 3 sections
 Duodenum
 Jejunum
 Ileum
◦ Coiled in order to increase its surface area
 Provides more surface for glands to secrete enzymes
for digestion
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Lined with 4-5 million villi
◦ Finger-like projections that help to mix food with
enzymes and to move it along to the large intestine
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Primary role – to absorb water and
electrolytes or salts
A 5-foot tube similar to the small intestine
◦ Differs in that it has no villi and absorbs no
nutrients
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Has sections
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Ascending colon – goes up right side
Transverse colon – goes across abdomen
Descending colon – goes down the left side
Sigmoid colon – end of large intestine; delivers
leftovers to the rectum
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Last stop in the digestive pathway
Where all undigested food, known as feces,
goes to be eliminated
The rectum contains 2 sphincter valves,
known as the anus, that remain tightly closed
except during defecation
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Body’s largest gland
Secretes bile to help the body digest fats
Also helps to filter toxic chemicals from the
venous blood as it travels back to the heart
Spleen
◦ assists the liver by removing damaged blood cells
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Produces a fluid with 3 enzymes that breaks
down food
Also secretes insulin
◦ Without insulin, sugar collects in the blood instead
of reaching tissues, which causes diabetes
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Pear-shaped sac located on the underside of
the liver (green)
Receives most of the liver’s bile and stores it
until needed
Sends bile to the small intestine when needed
to break down fatty foods
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Teeth – Grinds food into smaller, more
manageable particles for digestion
Tongue – Contains glands that secrete
enzymes and helps to move the food to the
pharynx
Salivary glands – Secrete salivary amylase, the
first enzyme involved in digestion
◦ Can’t taste food without this enzyme
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Fluids that come through the body must also
be digested and filtered
The urinary system is responsible for filtering
fluids and eliminating excess acids and salts
The body’s cells discharge all waste into the
bloodstream
The blood carries the acids and salts to the
kidneys for filtration
The kidneys filter the blood, then return the
filtered fluid back to the bloodstream
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The kidneys continue to filter the leftover
fluid and send it along to the ureter
The ureter is a long tube that descends to the
urinary bladder
The bladder is a hollow muscular organ with
a sphincter muscle on its lower section
Once the bladder fills, the body triggers the
sphincter to relax and the liquid waste is
eliminated as urine
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1. What is the pathway of digestion?
2. What are the organs of the alimentary
canal?
3. What are the accessory organs of
digestion?
4. What is physical digestion?
5. What is chemical digestion?
6. Why does the body need to go through
digestion of food?
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7. Be able to define the following:
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Epiglottis
Peristalsis
Pyloric region
Duodenum
Jejunum
Ileum
Enzyme
Gland
Villi
Pharynx
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8. Know the role of the following in digestion:
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Mouth, teeth, tongue
Esophagus
Stomach
Small intestine
Large intestine, including the 4 regions
Rectum
Liver
Pancreas
Gallbladder
Kidneys