Download The Digestive System

The Digestive System
S
Digestive System
S  The Digestive System is responsible for the
mechanical and chemical break down of food
so it can be taken in to the blood stream and
used by body cells and tissues.
S  Digestion begins in the mouth with the
mechanical break down of food and ends in
the large intestine with absorption
Alimentary Canal
S  Long muscular tube
S  Begins at the mouth and ends at the anus
S  Accessory organs: salivary glands, tongue,
teeth, liver, gallbladder, pancreas
Digestive
System
A collection of
structures that work
together to break
down food for
nutrients and energy
Mouth, Buccal, or Oral Cavity
S  Receives food as it enters the body
S  Actions in the mouth
S  Teeth: break down food by grinding
it down
S  Tongue: allows for taste, and aids
with chewing and swallowing
S  Hard palate: separates mouth from
nasal cavity
S  Soft palate: has uvula which blocks
food from entering the nasopharynx
Mouth or Buccal Cavity
S  Saliva Purpose:
S  Salivary Glands:
S  3 pairs of glands:
S  Parotid, sublingual, and
submadibular
S  Produces saliva
S  Lubricates the mouth during
speech and chewing
S  Moistens food so it can be
swallowed easily
S  Also contains enzyme that
speeds up the chemical
breakdown of carbohydrates
or starches
Pharynx or Throat
S  Carrier for both air and food
S  Carries food bolus to the esophagus
S  When bolus swallowed, epiglottis closes to
prevent food from entering respiratory tract
Esophagus
S  Muscular tube dorsal to the trachea
S  Carries bolus to stomach
S  Peristalsis moves food toward stomach
S  Peristalsis is rhythmic, wavelike
involuntary movement of it’s muscles
Stomach
S  Receives food from esophagus
S  Mucous membrane lining contains
rugae
S  Cardiac sphincter: small muscle
that keeps food from returning to
esophogus
S  Pyloric sphincter: small muscle
that keeps food from entering
small intestine until the appropriate
time
S  Food remains in stomach about 2–
4 hours
Stomach
S  Gastric Juices:
S  Juices contain enzymes:
S  Produced by glands in the
S  Lipase: breaks down fat
stomach
S  Converts food into semifluid
material called chyme
S  Juices contain hydrochloric acid
that kills bacteria, facilitates
absorption of iron, and activates
pepsin
S  Pepsin: breaks down protein
S  In infants contains renin that
helps to digest milk
S  Not present in adults
Small Intestine
S  About 20 feet long; 1 inch in
diameter
S  Receives food from the stomach in
the form of chyme from stomach
S  Small intestine
S  Duodenum: first 9-10 inches,
receives bile from gall bladder
and liver, and pancreatic juice
from pancreas
S  Jejunum: Middle 8 feet
S  Ileum: final 12 feet, connects
with large intestine
Small Intestine
S 
Absorbs products of digestion into blood stream for cells to use
S 
Intestinal juices: series of enzymes that break down sugars and proteins
S 
Bile: Comes from gall bladder and liver to emulsify and break down fats
S 
Pancreatic juice: Contains the enzymes that complete digestion of sugars, lipids, and
proteins
S 
Villi: Contain blood capillaries that absorb the nutrients in to the blood stream
S 
Villi also have lacteals that pick up fats and carry them to thoracic duct in the
lymphatic system, which releases them in to the circulatory system
S 
When food has finished its journey through the small intestine, only wastes,
indigestible materials, and excess water remain
Large Intestine
S  About 5 feet long; 2 inches in
diameter
S  Functions:
S  Absorb water and remaining
nutrients
S  Storage of indigestible waste
to be eliminated
S  Transportation of waste
S  Absorption and production of
vitamin B complex and
vitamin K
Large Intestine
S  3 parts:
S  Cecum: first section
S  Connects with small intestine
S  Contains appendix
S  Transverse Colon
S  Descending Colon
S  Sigmoid Colon: attaches to the
rectum
S  Colon: 3 parts
S  Rectum: Final 6-8 inches
S  Ascending colon
S  Stores waste
S  Has a narrow canal called the
anus, where waste exits body
Liver
S  Largest gland in the
body
S  Accessory organ
for digestive
system
S  Location: upper
right quadrant
Liver Functions
S  Secretes Bile: emulsify fat and
physically breaks down fats
S  Makes fats water soluable
S  Stores Iron and certain vitamins
S  Produces heparin which prevents
clotting
S  Stores sugar in the form of
S 
S  Releases sugar in blood stream
S  Produces cholesterol
glycogen: which is converted to
glucose
when sugar is needed
Produces fibrinogen and
prothrombin which aids in
clotting of blood
S  Detoxifies substances like
alcohol, pesticides, and destroys
bacteria
Gallbladder
S  Small muscular sac
S  Location: under the liver
S  Stores and concentrates bile
S  Bile needed to emulsify fats
Pancreas
S  Fish-shaped organ located behind the
stomach
S  Produces pancreatic juices to digest food
S  Produces insulin which is secreted into the blood stream; regulates burning of
carbohydrates to convert glucose to energy
Pancreas