Transcript Digestive System Notes

DIGESTIVE SYSTEM NOTES
 Directions:
 Read each slide & take notes as you would in
class.
 Study the diagrams throughout & pay
particular attention to highlighted regions.
You will need to know these structures for the
quiz.
 Any underlined terms WILL be on the quiz, so
notate accordingly in your notes!
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The Digestive System Functions
 Ingestion
 taking in food
 Digestion
 breaking food down both physically & chemically
 Absorption
 movement of nutrients into the bloodstream
 Defecation
 rids the body of indigestible waste
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Organs of the Digestive System
 Two main groups:
 Alimentary canal
 AKA gastrointestinal tract or GI tract
 continuous coiled hollow tube
 Accessory digestive organs
 Teeth
 Salivary glands
 Liver
 Gall bladder
 Pancreas
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Organs of the Alimentary Canal
 Mouth
 Pharynx
 Esophagus
 Stomach
 Small intestine
 Large intestine
 Anus
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Organs of the Digestive System – Book page 470
Figure 14.1
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Mouth Physiology
 Mastication (chewing) of food
 Bolus
 Mixture of masticated food & saliva in mouth
 Initiation of swallowing by the tongue
 Allows for the sense of taste
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Mouth (Oral Cavity) Anatomy
Figure 14.2a
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Esophagus Anatomy and Physiology
 Anatomy
 About 10 inches long
 Runs from pharynx to stomach through the
diaphragm
 AKA “Food Chute”
 Physiology
 Conducts food by peristalsis (smooth muscle
contractions to propel food)
 Passageway for food only (respiratory system
branches off to trachea after the pharynx)
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Stomach Anatomy
 Located on the left side of the abdominal cavity
 Food enters stomach from the esophagus at the
cardioesophageal sphincter
 Food empties from the stomach into the small
intestine at the pyloric sphincter (valve)
 When empty, stomach collapses inward on itself
& its mucosa (inner layer) form large folds called
rugae
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Stomach Anatomy
Figure 14.4a
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Stomach Physiology
 Temporary storage tank for food
 Site of food breakdown
 Pepsin = enzyme that breaks down protein in the
stomach
 Chyme = mixture of food & gastric juices in the
stomach
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Small Intestine
 The body’s major digestive organ
 Site of nutrient absorption into the blood
 Sections/subdivisions of the small intestine:
 Duodenum
 Attached to the stomach
 Curves around the head of the pancreas
 Jejunum
 Attaches anteriorly to the duodenum
 Ileum
 Extends from jejunum to large intestine
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Small Intestine Anatomy
 Peyer’s Patches
 Collections of lymphatic tissue found on the
intestines to prevent bacteria from spreading to
bloodstream
 Microvilli
 Tiny projections of the plasma membrane that
increases surface area for absorption
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Small Intestine Anatomy
Figure 14.7c
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Large Intestine
 Functions:
 Gets rid of indigestible waste
 Reduces water loss
 Larger in diameter, but shorter in length, than the
small intestine
 Frames the internal abdomen
 No villi present
 Haustra
 Pocket-like sacs resulting from bands of
muscle in intestinal wall
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Large Intestine Anatomy
 AKA “Colon”
 4 Sections:
 Ascending —travels up right side of abdomen
 Transverse —travels across the abdominal
cavity
 Descending —travels down the left side
 Sigmoid —enters the pelvis
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Large Intestine
Figure 14.8
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Large Intestine Anatomy
 Rectum & Anal Canal—downward descent of
colon in pelvis
 Anus —opening of the large intestine
 External anal sphincter—formed by skeletal
muscle and under voluntary control
 Internal involuntary sphincter—formed by
smooth muscle
 These sphincters are normally closed except
during defecation
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Large Intestine
Figure 14.8
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Accessory Digestive Organs
 Teeth
 Salivary glands
 Pancreas
 Liver
 Gallbladder
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Teeth
 Function is to masticate (chew) food
 Humans have two sets of teeth:
 Deciduous (baby or “milk”) teeth
 20 teeth are fully formed by age two
 Permanent teeth
 A full set is 32 teeth
 Some people do not have wisdom teeth
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Salivary Glands
 Three pairs of salivary glands empty secretions
into the mouth:
 Parotid glands
 Submandibular glands
 Sublingual glands
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Salivary Glands
Figure 14.1
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Saliva
 Mixture of mucus and serous fluids
 Helps to form a food bolus
 Contains salivary amylase to begin starch
digestion in the mouth
 Dissolves chemicals so they can be tasted
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Pancreas
 Produces a wide spectrum of digestive enzymes
that break down all categories of food
 Releases enzymes into small intestine
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Pancreas
Figure 14.1
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Liver
 Largest gland in the body
 Located on the right side of the body under the
diaphragm
 Produces Bile
 Secreted by gall bladder
 Digests lipids (fats)
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Liver
Figure 14.1
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Gallbladder
 Sac found on posterior side of liver
 Secretes bile for lipid digestion
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Appendix
 Located on your lower right side at the beginning
of the colon
 Usually twisted so ideal location for bacteria to
accumulate & multiply
 Appendicitis = inflammation of the appendix
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Spleen
 Located on your left side lateral to the stomach
 Filters blood
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Accessory Organs
Figure 14.1
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