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The DIGESTIVE System

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Title: The DIGESTIVE System


1
The DIGESTIVE System
2
1
3
Digestion
  • The breaking down of food by both mechanical and
    chemical means
  • Mechanical Digestion - various movements of the
    alimentary canal that aid in chemical digestion
  • Grinding of teeth to soften food
  • Churning of food by smooth muscles to mix with
    digestive enzymes
  • Chemical Digestion - series of catabolic
    reactions that break down large molecules into
    smaller molecules

4
Saliva would be considered
iRespond Question
Multiple Choice
F
A.) mechanical digestion
B.) chemical digestion
C.)
D.)
E.)
5
Absorption
  • The passage of digested food from the alimentary
    canal into the cardiovascular and lymphatic
    systems for distribution to body cells

6
Defecation (Excretion)
  • The elimination of indigestible substances from
    the alimentary canal

7
Ingestion
  • Taking food into the body (EATING)

8
Movement (Propulsion)
  • Passage of food along the
  • alimentary canal

9
2
10
Types of Digestion
  • Chemical digestion is the chemical breakdown of
    larger nutrient molecules to smaller ones which
    can be absorbed and used by the body.
  • Mechanical digestion is the physical breakdown of
    food into smaller pieces.

11
3
12
Gastrointestinal Tract (Alimentary Canal)
  • A continuous tube running through the ventral
    body cavity extending from the mouth to the anus
  • Organs of the Alimentary Canal
  • mouth - pharynx - esophagus
  • stomach - S. intestine - L. intestine
  • Accessory Organs
  • teeth - tongue
  • salivary glands - liver
  • gallbladder - pancreas

13
  • Structures of the Digestive System

14
Mouth(Oral or Buccal Cavity)
  • Cheeks
  • Lips (Labia)
  • Vestibule
  • Hard Palate
  • Soft Palate
  • Uvula
  • Tongue
  • Papillae
  • Lingual Frenulum

15
Oral Cavity
16
Pharynx
  • Also called the throat.
  • Serves as a passageway for food and air.
  • Also helps in the formation of words.

17
Esophagus
  • Muscular tube located posterior to the trachea
  • About 10 inches long
  • Does not participate in digestive processes -
    simply a transport corridor
  • Food is pushed through the esophagus by
    peristaltic action
  • Forces food down into the stomach
  • Esophageal hiatus - opening in the diaphragm for
    the esophagus

18
Food moves down the esophagus by way of
iRespond Question
Multiple Choice
F
A.) gravity
B.) peristalsis
C.) halstral churning
D.)
E.)
19
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20
Lining of the Esophagus
21
Stomach
  • J-shaped enlargement of the digestive tract
    located just below the diaphragm
  • Superior portion - continuation of the esophagus
  • Inferior portion empties into the duodenum
  • Position and size of the stomach varies from
    individual to individual

22
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23
Histology of the Stomach
  • Composed of the same four tissue types as the
    other structures of the alimentary canal
  • When the stomach is empty the mucosa lie in large
    folds called rugae
  • mucosa contains millions of tiny openings called
    gastric pits that open into gastric glands
  • Secretes digestive enzymes and a fluid called
    gastric juice (2-3 liter per day)

24
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25
Histology of the Stomach
26
Small Intestine
  • The next part of the alimentary canal.
  • Divided into three sections the duodenum,
    jejunum, and ileum.
  • In the duodenum, chemical digestion is completed.
  • The majority of nutrients are absorbed in the
    jejunum and ileum.

27
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28
Large Intestine
  • The last part of the alimentary canal.
  • Responsible for the absorption of water,
    compaction of feces, and the production of
    Vitamin K.

29
Accessory Organs
  • The accessory organs include the liver,
    gallbladder, pancreas, and salivary glands which
    will be discussed in more detail later on in this
    unit.

30
4
31
Salivary Glands
  • Paired accessory structures that lie outside the
    oral cavity
  • Secrete their contents (saliva) into ducts that
    empty into the mouth
  • Parotid Glands - underneath the ears
  • Submandibular Glands - under the mandible
  • Sublingual Glands - under the tongue

32
Salivary Glands
33
Saliva
  • Fluid secreted by the salivary glands
  • 99.5 water
  • .5 solutes
  • chlorides - bicarbonates - sodium
  • potassium - phosphates - urea
  • uric acid - globulin -mucin
  • serum albumin
  • Salivary amylase - digestive enzyme
  • begins carbohydrate digestion in the mouth
  • Lysozyme - destroys bacteria in the mouth

34
Digestion in the Mouth
  • Mechanical Digestion
  • Chewing (Mastication)
  • Tongue manipulates the food
  • Teeth grind up the food and mix it with saliva
  • The result of mechanical digestion is a soft
    flexible mass of food called a bolus
  • Chemical Digestion
  • Salivary amylase initiates the breakdown of
    carbohydrates

35
5
36
Teeth
  • Accessory structures of the digestive system
  • Deciduous teeth (baby teeth) - 20
  • Permanent teeth - 32
  • Incisors (8) - 4 on top, 4 on bottom
  • chisel shaped - front of mouth
  • Canines (4) - 2 on top, 2 on bottom
  • sharp pointed tearing teeth
  • Premolars (8) - 4 on top, 4 on bottom
  • Molars (12) - 6 on top, 6 on bottom
  • broad, flat, crushing teeth

37
Teeth
38
Portions of the Tooth
  • Crown - exposed portion of the tooth above the
    gum line
  • Neck - constricted junction line in the tooth
    between the crown and the root
  • Root - one to three projections of the tooth that
    are embedded in the sockets of the alveolar
    processes of the mandible and maxillae

39
Tooth Structures
40
Dental caries
41
Composition of Teeth
  • Enamel - outermost portion of the tooth, protects
    the tooth from wear and tear
  • the hardest substance in the body
  • Dentin - calcified connective tissue that gives
    the tooth its basic shape and rigidity
  • Pulp Cavity - large cavity enclosed by the dentin
    that is filled with pulp
  • Cementum - a bone-like substance that covers the
    dentin of the root

42
Periodontal Ligament
  • An area of dense fibrous connective tissue
    attached to the socket walls and the cemental
    surface of the roots of the teeth
  • Anchors teeth in position
  • Serves as a shock absorber when chewing

43
6
44
Swallowing (Deglutition)
  • Moving food from the mouth to the stomach
  • Voluntary Stage - bolus is moved through the
    mouth into the oropharynx
  • Pharyngeal Stage - involuntary passage of the
    bolus through the pharynx and into the esophagus
  • Esophageal Stage - involuntary passage of the
    bolus through the esophagus and into the stomach

45
Swallowing
46
Deglutition
47
7
48
Features of the Stomach
  • Cardiac Region where the stomach is connected
    to the esophagus.
  • Fundus the rounded, superior area of the
    stomach that acts as a temporary storage for
    food.
  • Body the large, central portion of the stomach
    below the fundus.

49
The term for chewing is
iRespond Question
Multiple Choice
F
A.) segmentation
B.) haustral churning
C.) maceration
D.) mastication
E.)
50
The top of the stomach is the
iRespond Question
Multiple Choice
F
A.) fundus
B.)cardiac region
C.) pylorus
D.)
E.)
51
fundus
52
Body of stomach
53
Features of the Stomach
  • Pylorus the narrow, inferior region of the
    stomach.
  • Rugae the folds in the stomach that allow for
    stretching of the stomach with the intake of
    food.
  • Pyloric Sphincter the one-way valve located
    between the stomach and the duodenum.

54
Structures of the Stomach
55
pylorus
56
Pyloric spincter
57
Stomach Structures
58
8
59
Secretory Cells of the Gastric Glands
  • Chief Cells
  • Digestive enzymes
  • Pepsinogen activated by HCl and converted to
  • Pepsin
  • Parietal Cells
  • HCl
  • Intrinsic Factor (absorption of Vitamin B12)
  • Goblet Cells
  • Secrete mucus to protect the stomach mucosa from
    the acidic environment

60
Which cell secrete HCL
iRespond Question
Multiple Choice
F
A.) chief cells
B.) parital cells
C.) goblet cells
D.)
E.)
61
Gastric Gland
62
GastricGland
63
Mechanical Digestion in the Stomach
  • Several minutes after food enters, the stomach
    generates mixing waves that churns the food
    inside - maceration
  • Food mixes with gastric juices and is converted
    into a thin liquid called chyme

64
Chemical Digestion in the Stomach
  • Cephalic Phase - reflexes initiated by sensory
    receptors in the head
  • sight - smell - taste
  • thought of food
  • Gastric Phase - sensory receptors in the
    alimentary canal and stomach initiate nervous and
    hormonal chemical digestive processes
  • Intestinal Phase - secretion of stomach enzymes
    that removes nutrients from food

65
Absorption in the Stomach
  • Does not participate in the absorption of food
    molecules into the blood
  • However, can absorb some substances through the
    stomach wall
  • Water
  • Weak glucose concentrations
  • Electrolytes
  • Certain drugs (aspirin)
  • Alcohol

66
Which of the folllowing would NOT be absorbed by
the stomach?
iRespond Question
Multiple Choice
F
A.) water
B.) sugar
C.) protein
D.) drugs
E.)
67
9
68
Pancreas
  • Oblong gland that lies posterior to the greater
    curvature of the stomach
  • Connected by ducts to the duodenum
  • Composed of clusters of glandular epithelial
    cells
  • Two main types of Pancreatic Cells
  • Pancreatic Islets-Islets of Langerhans (1)
  • Hormones insulin, glucagon, somatostatin
  • Acini Cells (99)
  • Digestive pancreatic enzymes

69
Pancreas
70
pancreas
71
Pancreatic Juice
  • Alkaline mixture of fluid and digestive enzymes
    from the acini cells
  • Pancreatic digestive enzymes
  • Pancreatic amylase - carbohydrate digestion
  • Pancreatic lipase - fat digestion
  • Chymotrypsin-Trypsin-Carboxypeptidase -
    protein digestion
  • Nucleases - nucleic acid digestion
  • Regulated by the intestinal hormones secretin and
    cholecystokinin

72
Which enzyme helps with the absorption of
carbohyrates?
iRespond Question
Multiple Choice
F
A.) tripsin
B.) amylase
C.) lipase
D.)
E.)
73
10
74
Liver
  • Located just under the diaphragm on the right
    side of the body
  • Largest organ of the abdominal-pelvic cavity
  • Weighs about 1.4 kgs (3 lbs)
  • Called the chemical factory of the body
  • Completely covered by the peritoneum and a dense
    layer of connective tissue beneath the peritoneum

75
Anatomy of the Liver
  • Right Lobe - largest lobe of the liver
  • Located on the lateral-right side of the body
  • Caudate Lobe - posterior portion of right lobe
  • Quadrate Lobe - inferior portion of right lobe
  • Left Lobe - smaller, medial lobe of the liver
  • Falciform Ligament - separates the right and left
    lobes of the liver and anchors it to the
    diaphragm and anterior abdominal wall

76
R lobe of liver
77
L lobe liver
78
Liver and Pancreas
79
Lobules of the Liver
  • Smaller functional units of the liver
  • Hepatocytes in the lobules produce and secrete a
    yellowish, brownish, or olive green liquid called
    bile (1 quart daily)
  • Composed of bile salts and pigments, lecithin,
    and several ions
  • pH of 7.6 - 8.6
  • Excretory product and digestive secretion
  • Assists in the breakdown of fat molecules
    (emulsification)
  • Principle bile pigment is bilirubin

80
The breakdown of fat is called?
iRespond Question
Multiple Choice
F
A.) peristalsis
B.) maceration
C.) emulsification
D.) segmentation
E.)
81
Functions of the Liver
  • Metabolism of carbohydrates, fats, and proteins
  • Removal of drugs and hormones
  • Excretion of bile
  • Synthesis of bile salts
  • Storage of vitamins, minerals, and food molecules
  • Phagocytosis of old worn out red and white blood
    cells
  • Activation of Vitamin D

82
Which is NOT a function of the liver
iRespond Question
Multiple Choice
F
A.) activation of vit D
B.) absorption of CHO, fats, proteins
C.) makes bile
D.) formation of blood
E.)
83
The Gallbladder
  • A pear shaped sac about 7 - 10 cm long
  • Located on the inferior surface of the liver
  • Stores and concentrates bile until it is needed
    by the small intestine for the emulsification of
    fat

84
Gallbladder
85
gallbladder
86
Bile Pathway
87
11
88
The Small Intestine
  • Duodenum - the beginning of the small intestine
    where it attaches to the stomach
  • First 6 inches
  • Jejunum - the portion of the small intestine
    right after the duodenum
  • Normally about 8 ft. long
  • Ileum - the final portion of the small intestine
  • About 12 ft. long
  • Ileocecal valve

89
jejunum
90
ileum
91
The Small Intestine
92
Wall of Duodenum
93
Villi in Duodenum
94
Chemical Digestion of the Small Intestine
  • Complex series of chemical events that results in
    the breakdown of carbohydrates, fats, and
    proteins
  • Result of the collective effort of pancreatic
    juice, bile, and intestinal juice which contain
    digestive enzymes
  • Results in absorption - passage of digested
    nutrients into the blood or lymph

95
Mechanisms to Increase Absorption by the Small
Intestines
  • Folds in the intestinal walls of the mucosa layer
    of tissue (Plicae Circulares)
  • Villi arrangement of tissue of mucosa layer
  • Lacteals - blood capillaries and lymphatic
    vessels associated with each villi
  • Microvilli arrangement of epithelial cells of the
    mucosa

96
Plicae Circulares
97
Villi of Small Intestine
98
Villi with Lacteal
99
Lining of Ileum
100
Absorption in the Small Intestine
  • 90 of absorption takes place within the small
    intestine
  • Remaining 10 occurs in the stomach and large
    intestine
  • Absorption of nutrients occurs through the villi
    by means of
  • diffusion - facilitated diffusion
  • osmosis - active transport

101
Small Intestine Absorption
102
Nutrient Absorption
103
Additional Components of the Small Intestine
  • Intestinal Juice - slightly alkaline secretion
    (pH 7.6) secreted by intestinal glands
  • rapidly absorbed by the villi and provides a
    mechanism for absorption of substances in chyme
  • Peyers Patches - lymphatic glands of the small
    intestine
  • Brunners Glands - mucus secreting glands of the
    small intestine

104
Mechanical Digestion of the Small Intestine
  • Segmentation - localized contraction of muscles
    of the small intestine in areas containing food
  • Rate of about 12 - 16 contractions/minute
  • Sloshing of chyme back and forth within the
    intestinal lumen
  • Peristalsis - rhythmical contraction of muscles
    of the small intestines that propels chyme
    through the intestinal tract

105
What is the order of the small intestines?
iRespond Question
Multiple Choice
F
A.) jejunum, duodenum, ileum
B.) ileum, duodenum, jejunum
C.) duodenum, jejunum, ileum
D.)
E.)
106
12
107
The Large Intestine
  • About 1.5 m (5 ft) in length
  • Cecum - beginning of the large intestine
  • Vermiform appendix
  • Colon - large tube-like portion of large
    intestine
  • Ascending colon - Transverse colon
  • Descending colon - Sigmoid colon
  • Rectum
  • Anal Canal
  • Anus

108
cecum
109
Ascending colon
110
Transverse colon
111
Descending colon
112
Large Intestine Structures
113
Functions of the Large Intestine
  • Completion of absorption
  • Reabsorption of water
  • Manufacture of certain vitamins
  • Formation of feces
  • Expulsion of feces from the body

114
Which is not a function of the large intestine
iRespond Question
Multiple Choice
F
A.) major absorption
B.) water absorption
C.) formation of vitamins
D.)
E.)
115
Histology of the Large Intestine
  • Walls of the large intestine contain no villi or
    permanent circular folds in the mucosa layer
  • Epithelial tissue layer contain numerous goblet
    cells (secretes mucus)
  • Lubricates the colonic contents as it passes
    through the large intestine

116
  • Haustra - series of characteristic pouch like
    structures that run the entire length of the
    colon
  • Teniae Coli - bands of smooth muscle that are
    arranged longitudinally along the length of the
    colon
  • Anal Columns - parallel ridges of mucosa in the
    anal canal which reduces friction with feces
    during defecation

117
Large Intestine Histology
118
Large Intestine Histology
119
Mechanical Digestion in the Large Intestine
  • Haustral Churning - the relaxation and
    contraction of the individual segments of the
    colon
  • Peristalsis - rhythmical contraction of the colon
    that moves the contents along through the length
    of the colon
  • Mass Peristalsis - a strong peristaltic wave that
    begins about the middle of the transverse colon
    and drives the colonic contents into the rectum

120
Chemical Digestion in the Large Intestine
  • Last stage of digestion
  • Due to bacterial action in the large intestine
  • Bacteria ferment any remaining carbohydrates and
    release hydrogen, carbon dioxide, and methane gas
  • Also converts any remaining proteins into amino
    acids
  • Absorbs any remaining water and electrolytes

121
Feces Formation in the Large Intestine
  • By the time chyme has remained in the large
    intestine for 3 - 10 hours it has become a solid
    or semi-solid and is known as feces
  • Consists of water, inorganic salts, sloughed off
    epithelial cells, products from bacterial
    decomposition, and indigestible parts of food

122
Defecation
  • The emptying of the rectum
  • Diarrhea - frequent defecation of liquid feces
  • Constipation - infrequent or difficult defecation

123
Parietal peritoneum
124
13
125
Digestive System Diseases and Homeostatic
Imbalances
126
Appendicitis
  • Inflammation of the vermiform appendix
  • Can be caused by an obstruction of the lumen of
    the appendix by fecal material, a foreign body,
    stenosis, kinking of the organ, or carcinoma

127
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128
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129
Cirrhosis of the Liver
  • Distorted or scarred liver tissue due to chronic
    inflammation
  • Commonly caused by hepatitis, chemical exposure,
    parasites, and alcoholism
  • Symptoms include jaundice, bleeding, edema, and
    increased sensitivity to drugs and chemicals

130
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131
Tumors of the Digestive System
  • Can occur in all areas of the digestive system
  • Can be malignant or benign
  • Colorectal Cancer
  • 3rd most common cause of cancer for both males
    and females
  • Overall mortality rate is over 60
  • Factors contributing to colorectal cancer include
    genetic predisposition, diet high in fat,
    protein, insufficient dietary fiber, and low
    calcium and selenium in the diet

132
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133
Gall Stones
  • Crystallization of bile in the gallbladder
  • Can block the bile duct causing intense pain
  • Usually treated with gall stone dissolving drugs,
    lithotripsy, or surgery

134
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135
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136
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137
Hepatitis
  • Inflammation of the liver
  • Can be caused by viruses, drugs, and certain
    chemicals including steroids and alcohol
  • Many different types of Hepatitis including
  • Hepatitis A (Infectious Hepatitis)
  • Hepatitis B (Serum Hepatitis)

138
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140
Hepatitis A
  • Infectious hepatitis
  • Caused by Hepatitis A virus
  • Spread by fecal contamination of food, clothing,
    toys, eating utensils, etc.
  • Generally a mild disease of children and young
    adults
  • Characterized by anorexia, malaise, jaundice,
    nausea, diarrhea, fever, and chills

141
Hepatitis B
  • Serum hepatitis
  • Caused by the Hepatitis B virus
  • Transmitted by sexual contact, contaminated
    syringes, transfusion equipment, saliva, tears,
    and puncture wounds in the skin
  • Can produce cirrhosis and possibly cancer of the
    liver

142
Obesity
  • Clinically classified as obese if
  • gt 30 of projected body weight as determined
    height and frame size
  • doesnt factor in Body Composition
  • Currently over 50 of U.S. population is
    clinically classified as obese
  • 14 of all male cancers linked to obesity
  • 20 of all female cancers linked to obesity

143
  • U.S. surgeon general has said Obesity is the
    second most serious threat to the health of
    Americans
  • A serious risk factor for
  • Heart Disease - Diabetes
  • Hypertension - Cancers
  • Respiratory Disorders
  • Endocrine Disorders
  • Gastrointestinal Disorders
  • Urinary and Reproductive System Disorders

144
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145
Peptic Ulcers
  • Crater like lesions that develop in the
    gastrointestinal tract
  • Gastric Ulcers ---gt Stomach
  • Duodenal Ulcers ---gt Duodenum
  • Commonly caused by hypersecretion of gastric
    juices and acids
  • Contributing factors include stress, cigarette
    smoking, certain foods, some medications, and
    bacterial infections

146
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147
Cleft lip and palate
148
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