Text of Digestive System 5.2 Investigate A&P of digestive system
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Digestive System 5.2 Investigate A&P of digestive
system
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Objectives Label the major organs on a diagram of the digestive
system Identify at least three organs that are located in the mouth
and aid in the initial breakdown of food Cite two functions of the
salivary glands Describe how the gastric juices act on food in the
stomach Explain how food is absorbed into the body by the villi in
the small intestine List at least three functions of the large
intestine List a t least four functions of the liver Explain how
the pancreas helps digest foods Describe at least five diseases of
the digestive system
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Digestive or GI system Physical and chemical breakdown of food
so that it can be taken into the bloodstream and used by body cells
and tissues. Alimentary canal plus accessory organs
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Alimentary canal Long, muscular tube that begins at the mouth
and includes the mouth (oral cavity), pharynx, esophagus, stomach,
small intestine, large intestine, and anus.
Mouth Buccal cavity Receives food- then food is tasted, broken
down physically by the teeth, lubricated and partially digested by
saliva, and swallowed
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Teeth Special structures in the mouth that physically break
down food by chewing and grinding. mastication
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Tongue Muscular organ that contains special receptors called
taste buds Sweet, salty, sour, and bitter sensations Aids in
chewing and swallowing
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Hard palate Bony structure that forms the roof of the mouth and
separates the mouth from the nasal cavity
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Soft palate Behind the hard palate, separates the mouth from
the nasopharynx Uvula- cone-shaped muscular structure, hangs from
the middle of the soft palate Prevents food from entering the
nasopharynx during swallowing
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Salivary glands Three pairs- parotid, sublingual, and
submandibular, produce saliva which lubricates the mouth during
speech and chewing and moistens food so it can be swallowed easily.
Contains an enzyme called salivary amylase which begins the
chemical breakdown of carbohydrates or starches into sugars.
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Pharynx Food chewed and mixed with saliva is called a bolus.
When swallowed the bolus enters the pharynx (throat). Carries both
food and air. Food-esophagus Air-trachea During swallowing
epiglottis closes over larynx to prevent bolus from entering
respiratory tract.
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Esophagus Muscular tube dorsal to trachea. Carries bolus to
stomach. Peristalsis- rhythmic, wavelike, involuntary movement of
muscles
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Stomach Enlarged part of alimentary canal. Receives food Mucous
membrane lining contains folds called rugae Rugae disappear as
stomach fills and expands Cardiac sphincter- circular muscle
between esophagus and stomach, closes after food enters to prevent
food from going back up.
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Stomach cont. Pyloric sphincter- circular muscle between
stomach and small intestine, keeps food in stomach until food ready
to enter small intestine. 2-4 hours Food converted into a semi
fluid material, called chyme, by gastric juices produced by glands
in stomach
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Stomach cont. Gastric juices- HCL and enzymes HCL kills
bacteria, facilitates iron absorption, and activates the enzyme
pepsin. Enzymes- lipases- starts the chemical breakdown of fats,
and pepsin- starts protein digestion Infants- enzyme rennin aids in
digestion of milk
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Small Intestine Chyme enters from stomach Coiled section of
alimentary canal 20 ft length and 1 inch diameter Duodenum (first
9-10 inches)- bile from the gallbladder and liver and pancreatic
juice from the pancreas enter this section through ducts or
tubes.
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Small Intestine Jejunum- 8 ft length- middle section
Ileum-final 12 ft connects with large intestine at the cecum.
Circular muscle called ileocecal valve separates the ileum and
cecum- prevents food from returning to ileum. Process of digestion
completed in small intestine Products of digestion absorbed into
bloodstream for use by cells
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Small intestine- intestinal juices Enzymes maltase, sucrase and
lactase- breakdown sugars Enzymes- peptidases- complete digestion
of proteins Enzyme Steapsin (lipase) aids in digestion of fat Bile
from liver and gall bladder emulsifies (physically breaks down)
fats.
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Small intestine- intestinal juices Pancreatic enzymes- amylase
(acts on sugars), trypsin and cymotrypsin (acts on proteins),
lipase or steapsin (acts on fats).
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Small intestine After food digested, absorbed into bloodstream
Walls of intestine lined with fingerlike projections called villi.
Villi contain blood capillaries and lacteals. Blood capillaries
absorb digested nutrients and carry them to liver where they are
stored or released into general circulation for use by body
cells.
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Small intestine Lacteals absorb most of digested fats and carry
them to the thoracic duct in lymphatic system which releases them
into circulatory system. When food completed passage through SI,
only wastes, indigestible materials, and excess water remain
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Large Intestine Final section of alimentary canal 5 ft long and
2 inch diameter
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Functions Absorption of water and remaining nutrients Storage
of indigestible materials until eliminated Synthesis and absorption
of some b-complex vitamins and vitamin K by bacteria present in
intestine Transportation of the waste products out of the
alimentary canal
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Sections Cecum 1 st Connects with ileum of small intestine
Contains a small projection called the vermiform appendix
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Colon Ascending colon continues up on right side of body from
cecum to lower part of liver Transverse colon extends across the
abdomen, below liver and stomach but above small intestine
Descending colon extends down the left side of the body Sigmoid
colon Connects with descending colon S-shaped section that joins
with the rectum
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Rectum Final 6-8 inches Storage area for indigestibles or
wastes Narrow canal called the anal canal which opens at a hole
called anus Fecal material or stool, the final waste product of
digestive process, expelled through this opening
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liver Largest gland in the body Accessory organ Under diaphragm
in upper right quadrant of abdomen
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Functions Secretes bile Used to emulsify or physically break up
fats Makes fats water soluble, which is necessary for absorption
Stores sugar in the form of glycogen glycogen is converted to
glucose Released into the bloodstream when additional blood sugar
is needed
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Functions cont. Stores iron and certain vitamins Produces
heparin (prevents blood clotting) Produces blood proteins such as
fibrinogen and prothrombin, which aid in clotting of the blood
Produces cholesterol Detoxifies substances such as alcohol and
pesticides, destroys bacteria that have been taken into the blood
from the intestine
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Gallbaldder Small muscular sac Under liver attached to it by
connective tissue Stores and concentrates bile (which it receives
from liver) When bile needed in digestive tract to emulsify fats,
it contracts and pushes the bile through the common bile duct into
duodenum
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Pancreas Fish-shaped organ located behind stomach Produces
pancreatic juices Juices enter duodenum through pancreatic duct
Contain enzymes to digest food Pancreatic amylase to break down
sugars Trypsin and chymotrypsin to break down prteins Lipase to act
on fats
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Pancreas cont. Produces insulin Secreted into the bloodstream
Regulates the metabolism or burning of carbohydrates to convert
glucose to energy
