I. BASIC FUNCTIONS OF THE DIGESTIVE TRACT A. Digestionprocess
of altering the physical state and chemical composition of food so
that the bodys cells can use it B. Absorptionprocess by which small
digested molecules pass through the cells of the intestinal tract,
entering the blood and lymph 1
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II. ANATOMY OF DIGESTIVE SYSTEM A. Components 1. Alimentary
Canal Mouth Pharynx Esophagus Stomach Small intestine Large
intestine 2. Accessory Organs Salivary glands Liver Gallbladder
Pancreas 2
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Alimentary Canal 3
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B. Wall Structure of Alimentary Canal 1. Alimentary canal is a
muscular tube, 30 feet long, and located in the ventral body
cavity. 2.Has the same four layers throughout: a. Mucosa Innermost
layer b. Submucosa Loose CT with blood vessels, glands, lymph
vessels, and nerves c. Muscularis mucosa 2 layers of smooth muscle
d. Serosa Outermost layer (visceral peritoneum) 5
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Wall of the Alimentary Canal 6
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C. Movement of the tube 2 Basic Movements: 1. Mixingmixes food
with juices secreted by the mucosa of the stomach 2. Propelling
movementsperistalsis (wavelike contractions that force food along
the digestive tube) MixingPeristalsis 7
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D. Oral Cavity 1. Mouth Receives food Prepares food for
digestion (breaks food into small particles and mixes it with
saliva) 2. Tongue Mostly muscle Anchored to midline of the floor of
the mouth by the frenulum Covered with papillae which contain taste
buds Movement aids in mixing food and saliva and moving food toward
the rear of the mouth 8
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3. Palate Forms roof of the mouth Consist of hard anterior part
(hard palate) and soft posterior part (soft palate)
Uvulacone-shaped projection that hangs down from soft palate and
pulls upward when swallowing to prevent food from entering the
nasal cavity 4. Tonsils Masses of lymphatic tissue 3 tonsil masses:
a. palatine b. pharyngeal (adenoids) c. lingual 9
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Oral Cavity 10
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Tonsils 11
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5. Teeth 2 sets a. primary (deciduous)20 b. secondary
(permanent)32 F(x): mastication (chewing) 4 types of teeth: a.
incisorsfront teeth for biting b. caninecone-shaped for tearing
food c. bicuspidsfor grinding food particles d. molarsfor grinding
food particles 12
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4 Types of Teeth 13
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Consists of: a. crownpart above gum b. rootanchored to bone by
cementum and periodontal ligament c. enamelcovers crown --hardest
substance in body d. dentinunder enamel --like very hard bone e.
pulp cavityunder dentin --contains blood vessels, nerves, and CT
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Tooth 16
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E. Salivary Glands 1. F(x): To secrete saliva which moisten
food and begins carbohydrate digestion Cleanses mouth and teeth
Dissolves food for taste 2. Consists of serous cells which produce
amylase (enzyme that breaks down starch and glycogen) and mucous
cells which secrete mucus for lubrication 3. 3 major pairs of
salivary glands a. parotidsin front of and below each ear b.
submandibularin floor of mouth c. sublingualon floor of mouth under
tongue 17
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Salivary Glands 18
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F. Pharynx 1. Common to digestive and respiratory tracts 2.
Divided into 3 areas: a. nasopharynxpassage for air during
breathing b. oropharynxpassageway for food and air c.
laryngopharynxopens into larynx and esophagus 3. F(x): Swallowing
(deglutition) -Voluntary but becomes involuntary as swallowing
reflex is initiated -Involves chewing and bolus (ball of partially
digested food) formation 19
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Pharynx 20
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G. Esophagus 1. Collapsed tube about 10 inches long that
connects pharynx and stomach 2. Mucous glands keep it moist and
lubricated H. Stomach 1. Anatomy J shaped pouch-like organ just
under the diaphragm in the upper left portion of abdominal cavity
Inner mucosa forms folds called rugae 21
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2. F(x): Receive food Mix food with gastric juice Initiate
protein digestion Limited absorption Transport partially digested
food to small intestine 3. Divided into 4 regions: a. cardiacnear
esophageal opening b. fundustemporary storage area c. body d.
pylorusenters small intestine 22
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Stomach 23
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4. Mucosa is thick with many gastric glands. 5. Gastric glands
contain 3 types of secretory cells: a. goblet cellssecrete mucus b.
chief cellssecrete digestive enzyme- pepsinogen (inactive form of
pepsin which digest proteins) c. parietal cellssecrete hydrochloric
acid (HCl) and intrinsic factor 24
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Gastric Gland (Lining of Stomach) 25
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6. F(x) of gastric gland secretions: a. mucusprotection b.
HClconverts pepsinogen to pepsin c. intrinsic factoraids in
absorption of vitamin B 12 in small intestine 7. Regulation of
Gastric Secretion Under nerve and hormone control Gastrin (stomach
hormone) increases release of gastric juices 8. Substances absorbed
in stomach: water glucose alcohol aspirin lipid-soluble drugs
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9. Mixing and Emptying of Stomach Mixing produces chyme
(semisolid paste) and peristalsis moves it to the pylorus Rate of
emptying depends on the type of food present Liquids pass through
rapidly Solids remain until well mixed with gastric juices Fatty
food remains the longest Carbohydrates pass through the fastest
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PANCREAS 28 A. Structure 1.Elongated, flattened organ 2.Extends
horizontally across the posterior abdominal wall in the C-shaped
curve of the duodenum 3.Pancreatic secretions enter the
duodenum(small intestine) through the pancreatic duct 4.
Heterocrine Gland (endocrine and exocrine) 5. Exocrine Component
functions in digestion Pancreatic acinar cells -make up most of the
pancreas -produce pancreatic juice
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Pancreas 29
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LIVER 30 A. Structure 1. Macroscopic Reddish-brown in color
Enclosed in a fibrous capsule Well supplied with blood vessels
Located in the upper right side of the abdominal cavity inferior to
the diaphragm Divided into 2 lobes (large right lobe and smaller
left lobe) 2. Microscopic Each lobe is separated into many tiny
hepatic lobules (functional unit of liver) Each lobule has many
hepatic (cuboidal) cells radiating outward from a central vein
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Liver 31
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32 Functions of the Liver 1. Carries out the metabolism of
carbohydrates, lipids, and proteins 2. Storage Stores glycogen
(animal starch), iron, blood, and vitamins A, D, B 12 3. Blood
filtering Removal of damaged red blood cells and foreign
substances
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III. GALLBLADDER 33 A. Structure 1. Pear-shaped sac on the
inferior surface of the liver 2. Lined with epithelial cells 3.Wall
contains a strong, muscular layer 4. Connects to cystic duct which
joins with the common hepatic duct to form the common bile duct
which empties into the duodenum B. Functions 1.Store bile
2.Concentrate bile by reabsorbing water 3.Release bile into small
intestine
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34 Gallstones 1. Crystals formed from cholesterol in bile 2.
Can block bile flow, cause pain, and result removal of
gallbladder
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SMALL INTESTINE 35 A. Structure 1.Tubular organ about 20 feet
long 2.Joins the stomach at the pyloric sphincter 3.Joins the large
intestine at the ileocecal junction 4.3 Divisions: duodenum~10
inches long and 2 in. in diameter (fixed) jejunum~8 feet long
ileum~12 feet long 5. Jejunum and ileum are suspended by the
mesentery (tissue containing blood vessels, nerves, and lymphatic
vessels that supply the intestinal wall)
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38 Functions of the Small Intestine 1. Completes digestion 2.
Absorbs products of digestion 3. Receives secretions from pancreas
and liver 4. Transports residues to large intestine
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V. LARGE INTESTINE 39 A. Structure 1. 5 feet long 2. 4
Divisions of Large Intestine a. Cecum First 2-3 inches Blind pouch
to which is attached the vermiform appendix (lymphatic tissue which
has no digestive function) Opening between ileum and cecum
controlled by ileocecal valve
41 c. Rectum From colon to anal canal d. Anal Canal Last 1-2
inches of large intestine Anus -opening on distal end of anal canal
-controlled by 2 sphincter muscles: internal anal sphincter--
involuntary external anal sphincter-- voluntary
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Large Intestine 42
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43 B. Functions of the Large Intestine 1. secrete mucus 2.
reabsorb water and electrolytes 3. store and eliminate waste
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44 C. Feces 1. Solid waste 2. Undigested or unabsorbed material
3. 75% water 4. Color due to bile pigments 5. Odor from bacterial
activity