The Digestive System

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33

• The Digestive System

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Learning Outcomes (cont.)

• 33.1 Describe the organs of the alimentary canal
  and their functions.
• 33.2 Explain the functions of the digestive
  systems accessory organs.

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Learning Outcomes (cont.)

• 33.3 Identify the nutrients absorbed by the
  digestive system and where they are absorbed.
• 33.4 Describe the causes, signs and symptoms,
  and treatments of various common diseases and
  disorders of the digestive system.

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Introduction

• Digestion mechanical and chemical breakdown of
  foods
• Organs of digestion
• Alimentary canal organs form a pathway extending
  from the mouth to the anus
• Accessory organs

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Characteristics of the Alimentary Canal

• Mucosa
• Epithelial tissue
• Secretes enzymes and mucus
• Absorbs nutrients
• Submucosa loose connective tissue, blood
  vessels, glands, and nerves

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Characteristics of the Alimentary Canal

• Muscular layer
• Smooth muscle
• Contracts to move materials through the canal
• Serosa or peritoneum
• Visceral peritoneum
• Parietal peritoneum

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Characteristics of the Alimentary Canal (cont.)

• Movements
• Churning mixes substances
• Peristalsis moves substances

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The Mouth

• Buccal cavity
• Mechanical digestion
• Starts chemical digestion
• Cheeks hold food in mouth
• Lips judge temperature of food

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The Mouth (cont.)

• Tongue
• Mixes and holds food between teeth
• Contains taste buds
• Lingual frenulum
• Lingual tonsils

• Palate
• Hard palate
• Soft palate
• Uvula
• Lymphatic tissue
• Palatine tonsils
• Pharyngeal tonsils or adenoids

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The Mouth (cont.)
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The Mouth (cont.)

• Salivary glands
• Cells
• Serous watery fluidand amylase
• Mucous
• Parotid gland
• Submandibular gland
• Sublingual gland

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The Mouth (cont.)

• Teeth decrease size of food particles
• Incisors
• Cuspids or canines
• Bicuspids and molars

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Pharynx

• Functions
• Connects nasal cavity with oral cavity for
  breathing
• Pushes food into esophagus

• Divisions
• Nasopharynx
• Oropharynx
• Laryngopharynx

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Pharynx (cont.)

• Swallowing
• Soft palate rises uvula covers opening between
  nasal and oral cavity
• Epiglottis covers larynx keeps food out
• Tongue presses against roof of mouth, forcing
  food into oropharynx

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Pharynx (cont.)

• Swallowing
• Muscles in pharynx contract forcing food toward
  esophagus
• Esophagus opens
• Muscles of pharynx push food through cardiac
  sphincter

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The Esophagus

• Connects pharynx to stomach
• Esophageal hiatus
• Cardiac sphincter
• Circular band of muscle
• Controls movement of food into stomach

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The Stomach

• Absorbs
• Alcohol
• Water
• Some fat-soluble drugs

• Rugae folds of the inner lining
• Functions
• Receives food
• Mixes bolus with gastric juices ? chyme
• Starts protein digestion
• Moves food into small intestine

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The Stomach

• Sections
• Cardiac region
• Fundus
• Pyloric sphincter controls movement into the
  small intestine

• Body
• Pylorus

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The Stomach

• Lining gastric glands
• Cells mucous, chief, and parietal
• Stimulated by
• Parasympathetic nervous system
• Gastrin made by the stomach
• Inhibited by cholecystokinin (CCK) made by the
  small intestine

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The Small Intestine

• Functions
• Digestion
• Absorption of nutrients

• Sections
• Duodenum
• Jejunum
• Ileum
• Mesentery

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The Small Intestine (cont.)

• Stimulated by
• Parasympathetic nervous system
• Stretching of the intestinal wall

• Microvilli
• Intestinal glands
• Mucus and water
• Enzymes
• Peptidases
• Sucrase, maltase, and lactase
• Intestinal lipase

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The Small Intestine (cont.)

• Absorbs most nutrients
• Wall contracts to mix and propel chyme
• Ileocecal sphincter controls movement of chyme
  into cecum of the large intestine

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The Large Intestine

• Cecum
• Vermiform appendix
• Ascending colon

• Transverse colon
• Descending colon
• Sigmoid colon

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The Rectum and Anal Canal

• Rectum off sigmoid colon
• Anal canal
• End of rectum
• Anus

• Feces left-over chyme
• Defecation reflex
• Stimulated by mass movements
• Relaxation of anal sphincters

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Apply Your Knowledge
1. Matching ___ Buccal cavity A. Saliva ___
Roof of mouth B. Mouth ___ Grind
food C. Bolus ___ Adenoids D. Palate ___ Water,
enzymes, and mucus E. Bicuspids ___ Mass of food
mixed with saliva and mucus F. Pharyngeal gland
ANSWER
B
D
E
F
A
B
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Apply Your Knowledge
2. What are the functions of the stomach?
ANSWER The stomachs functions are to receive
the bolus of food, mix it with gastric juice,
start protein digestion, and move food into the
small intestine. It also absorbs alcohol, water,
and some drugs.
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Apply Your Knowledge
Super!
3. Matching ___ Vermiform appendix A. Feces ___
Crosses the abdomen B. Ascending colon ___ Up
right side of abdomen C. Anal canal ___ S-shaped
tube D. Defecation reflex ___ Down left side of
abdomen E. Sigmoid ___ Leftover
chyme F. Transverse colon ___ Last section of
rectum G. Cecum ___ Allows anal sphincters to
relax H. Descending colon
ANSWER
G
F
B
E
H
A
C
D
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Characteristics of the Digestive Accessory Organs

• Part of livers function store vitamins and
  iron

• The Liver
• Hepatic lobules
• Smaller divisions of lobes
• Macrophages
• Hepatocytes bile
• Hepatic portal vein

To Liver
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The Liver (cont.)

• Hepatic duct
• Bile from liver
• Merges with cystic duct and forms common bile
  duct
• Common bile duct delivers bile to duodenum

To Liver
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The Gallbladder

• Only function is to store bile
• Cholecystokinin stimulates gallbladder to release
  bile
• Bile salts
• Break up large fat globules
• Increase absorption of fatty acids, cholesterol,
  and fat-soluble vitamins

To Gallbladder
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The Liver (cont.)
Back
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The Pancreas

• Acinar cells produce pancreatic juice
• Pancreatic amylase
• Pancreatic lipase
• Nucleases
• Trypsin, chymotrypsin, and carboxypeptidase

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The Pancreas (cont.)

• Releases bicarbonate ions into duodenum
• Stimulated to release enzymes by
• Parasympathetic nervous system
• Secretin and cholecystokinin

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Apply Your Knowledge
1. What is the route of bile through the liver
and gallbladder?
ANSWER Bile is made in the hepatocytes and
leaves the liver through the hepatic duct. The
hepatic duct merges with the cystic duct from the
gallbladder to form the common bile duct, which
delivers bile to the duodenum.
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Apply Your Knowledge
2. What are the pancreatic enzymes and what do
they do?

• ANSWER They are
• Pancreatic amylase digests carbohydrates
• Pancreatic lipase digests lipids
• Nucleases digest nucleic acids
• Trypsin, chymotrypsin, and carboxypeptidase
  digest proteins

Good Job!
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The Absorption of Nutrients

• Nutrients necessary food substances
• Carbohydrates
• Proteins
• Lipids
• Vitamins
• Minerals
• Water

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The Absorption of Nutrients (cont.)

• Carbohydrates
• Starches polysaccharides
• Simple sugars
• Monosaccharides and disaccharides
• Excess glucose stored as glycogen
• Cellulose provides fiber or bulk

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The Absorption of Nutrients (cont.)

• Lipids
• Used to make energy when glucose levels are low
• Triglycerides
• Most abundant
• Excess stored in adipose tissue
• Cholesterol essential for cell growth and
  function

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The Absorption of Nutrients (cont.)

• Protein
• Requirements vary
• Used for growth and tissue repair

• Vitamins
• Fat-soluble
• Water-soluble
• Minerals
• Found in bones and teeth
• Used to make enzymes, cell membranes, and
  proteins

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Apply Your Knowledge
True or False ___ Carbohydrates are starches,
simple sugars, and cellulose. ___ Excess glucose
is stored in the gallbladder as glycogen. ___
Triglycerides are the least abundant lipids ___
Linoleic acid is an essential fatty acid. ___ A,
D, E and K are water-soluble vitamins. ___
Minerals are used by cells to make enzymes.
ANSWER
T
liver
F
most
F
T
Impressive!
fat-soluble
F
T
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Aging and the Digestive System

• Decreased
• Motility
• Absorption
• Ability to detoxify blood
• More likely to develop ulcers and cancers

• Sense of taste altered
• Dietary changes due to
• Isolation
• Depression

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Common Diseases and Disorders
Disease/Disorder Description
Appendicitis Inflammation of the appendix can be life-threatening if not treated promptly
Cirrhosis Chronic liver disease normal tissue is replaced with nonfunctional scar tissue
Cholelithiasis (gall stones) Hard deposits of cholesterol or bilirubin in the gall bladder
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Common Diseases and Disorders
Disease/Disorder Description
Colitis Inflammation of the large intestine can be acute or chronic
Colorectal cancer Arises from lining of rectum or colon curable if treated early
Constipation Difficult defecation
Crohns disease Inflammatory bowel disease typically effects small intestine
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Common Diseases and Disorders (cont.)
Disease/Disorder Description
Diarrhea Watery and frequent feces usually self-limiting
Diverticulitis Inflammation of diverticula Diverticulosis diverticula with no inflammation
Gastritis Inflammation of the stomach lining upset stomach
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Common Diseases and Disorders (cont.)
Disease/Disorder Description
Heartburn Gastroesophageal reflux disease (GERD) stomach acids push into esophagus
Hemorrhoids Varicose veins of rectum or anus
Hepatitis Inflammation of the liver various types
Hiatal hernia Portion of stomach protrudes into the chest through an opening in the diaphragm
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Common Diseases and Disorders (cont.)
Disease/Disorder Description
Inguinal hernia Portion of large intestine protrudes in the inguinal canal (where thigh and trunk meet) or, in males, into the scrotum
Oral cancer Usually involves the lips or tongue but can occur anywhere in the mouth tends to spread rapidly
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Common Diseases and Disorders (cont.)
Disease/Disorder Description
Pancreatic cancer Fourth leading cause of cancer deaths in the U.S.
Stomach cancer Commonly in cardiac portion of the stomach occurs more frequently in Japan, Chili, and Iceland
Stomach ulcers Breakdown in lining of the stomach
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Apply Your Knowledge
Matching ___ Inflammation of the large
intestine A. Heartburn ___ Inflammatory bowel
disease B. Hemorrhoids ___ Watery and frequent
feces C. Constipation ___ Difficult
defecation D. Crohns disease ___ Inflammation of
the stomach lining E. Colitis ___ Inflammation of
pouches in the intestinal wall F. Diarrhea ___
GERD G. Gastritis ___ Varicose veins of
rectum H. Diverticulitis
D
F
C
G
H
A
B
Nice Job!
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In Summary

• 33.1 The pathway of food through the alimentary
  canal starts with the mouth and continues
  through the pharynx, esophagus, stomach, small
  intestine, large intestine, and anal canal.

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In Summary (cont.)

• 33.2 The accessory organs to the digestive
  system include the liver, gallbladder, and
  pancreas.
• 33.3 Nutrients absorbed by the body include
  carbohydrates, proteins, lipids, vitamins,
  minerals, and water. Most of the absorption
  takes place in the small intestine.

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In Summary (cont.)

• 33.4 There are many common diseases and
  disorders of the digestive system with varied
  signs, symptoms, and treatments.

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End of Chapter 33
Take all that is given whether wealth, love or
language nothing comes by mistake and with good
digestion all can be turned to health. George
Herbert