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CHAPTER

33

The Digestive

System

© 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part.

Learning Outcomes (cont.)

33.1 Describe the organs of the alimentary canal and their functions.

33-2

33.2 Explain the functions of the digestive system’s accessory organs.


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.

33-3


33-4

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


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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• Muscular layer

– Smooth muscle

– Contracts to move materials through the canal

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• Serosa or peritoneum

– Visceral peritoneum

– Parietal peritoneum



(cont.)

• Movements

– Churning ~ mixes substances

– Peristalsis ~ moves substances

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33-8

The Mouth

• Buccal cavity

• Mechanical digestion

• Starts chemical digestion

• Cheeks – hold food in mouth

• Lips – judge temperature of food

The Mouth


33-9

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

The Mouth


33-11

The Mouth (cont.)

• Salivary glands

– Cells

• Serous – watery fluid and amylase

• Mucous

– Parotid gland

– Submandibular gland

– Sublingual gland


33-12

The Mouth (cont.)

• Teeth – decrease size of food particles

– Incisors

– Cuspids or canines

– Bicuspids and molars


Pharynx

• Functions

– Connects nasal cavity with oral cavity for breathing

• Divisions

– Nasopharynx

– Oropharynx

– Laryngopharynx

– Pushes food into esophagus

33-13

Pharynx


33-14

Pharynx (cont.)

Swallowing

1.

Soft palate rises; uvula covers opening between nasal and oral cavity

2.

Epiglottis covers larynx – keeps food out

3.

Tongue presses against roof of mouth, forcing food into oropharynx

Pharynx


Pharynx (cont.)

Swallowing

4.

Muscles in pharynx contract – forcing food toward esophagus

5.

Esophagus opens

6.

Muscles of pharynx push food through cardiac sphincter

33-15

Pharynx


33-17

The Esophagus

• Connects pharynx to stomach

• Esophageal hiatus

• Cardiac sphincter

– Circular band of muscle

– Controls movement of food into stomach

Upper

Esophagus

Lower

Esophagus


The Stomach

• Rugae – folds of the inner lining

• Absorbs

– Alcohol

– Water

– Some fat-soluble drugs

• Functions

– Receives food

– Mixes bolus with gastric juices  chyme

– Starts protein digestion

– Moves food into small intestine

33-18

Stomach


The Stomach

• Sections

– Cardiac region

– Fundus

– Body

– Pylorus

• Pyloric sphincter – controls movement into the small intestine

33-19

Stomach


33-20

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

Stomach


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The Small Intestine

• Functions

– Digestion

– Absorption of nutrients

• Sections

– Duodenum

– Jejunum

– Ileum

• Mesentery

Small

Intestine


The Small Intestine (cont.)

• Microvilli

• Intestinal glands

– Mucus and water

– Enzymes

• Peptidases

• Sucrase, maltase, and lactase

• Intestinal lipase

– Stimulated by

• Parasympathetic nervous system

• Stretching of the intestinal wall

33-23


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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33-26

The Large Intestine

• Cecum

• Vermiform

• Transverse colon

• Descending colon appendix • Sigmoid colon

• Ascending colon

Large

Intestine


33-27

The Rectum and Anal Canal

• Rectum – off sigmoid colon

• Feces – left-over chyme

• Anal canal

– End of rectum

– Anus

• Defecation reflex

– Stimulated by mass movements

– Relaxation of anal sphincters

Rectum &

Anal Canal


Apply Your Knowledge

1. Matching: ANSWER:

A. Saliva

B. Mouth

C. Bolus

D. Palate

E. Bicuspids

___ Mass of food mixed with saliva and mucus F. Pharyngeal gland

33-29



2. What are the functions of the stomach?

ANSWER: The stomach’s 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.

33-30



3. Matching: ANSWER:

Super!

A. Feces

B. Ascending colon

C. Anal canal

D. Defecation reflex

E. Sigmoid

F. Transverse colon

G. Cecum

H. Descending colon

33-31


33-32

Characteristics of the Digestive Accessory

Organs

• The Liver

– Hepatic lobules

• Smaller divisions of lobes

• Macrophages

• Hepatocytes – bile

– Hepatic portal vein

– Part of liver’s function

~ store vitamins and iron

To Liver


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

33-33


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

33-34


The Pancreas

• Acinar cells produce pancreatic juice

– Pancreatic amylase

– Pancreatic lipase

– Nucleases

– Trypsin, chymotrypsin, and carboxypeptidase

33-36


33-37


The Pancreas (cont.)

• Releases bicarbonate ions into duodenum

33-38

• Stimulated to release enzymes by

– Parasympathetic nervous system

– Secretin and cholecystokinin



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.

33-39



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

33-40

Good Job!


33-41

The Absorption of Nutrients

• Nutrients – necessary food substances

– Carbohydrates

– Proteins

– Lipids

– Vitamins

– Minerals

– Water


The Absorption of Nutrients (cont.)

• Carbohydrates

– Starches ~ polysaccharides

– Simple sugars

• Monosaccharides and disaccharides

• Excess glucose stored as glycogen

– Cellulose – provides fiber or bulk

33-42



• 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

33-43



• Vitamins

– Fat-soluble

– Water-soluble

• Protein

– Requirements vary

– Used for growth and tissue repair

• Minerals

– Found in bones and teeth

– Used to make enzymes, cell membranes, and proteins

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33-45


True or False:

ANSWER: liver most fat-soluble


33-46

Aging and the Digestive System

• Decreased

– Motility

– Absorption

– Ability to detoxify blood

• Sense of taste altered

• More likely to develop ulcers and cancers

• Dietary changes due to

– Isolation

– Depression


Common Diseases and Disorders

Disease/Disorder Description

Appendicitis

Cirrhosis

Inflammation of the appendix; can be life-threatening if not treated promptly

Chronic liver disease; normal tissue is replaced with nonfunctional scar tissue

Cholelithiasis (gall stones)

Hard deposits of cholesterol or bilirubin in the gall bladder

33-47


Common Diseases and Disorders


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

Crohn’s disease Inflammatory bowel disease; typically effects small intestine

33-48


Common Diseases and Disorders (cont.)


Diarrhea

Diverticulitis

Gastritis

Watery and frequent feces; usually self-limiting

Inflammation of diverticula

Diverticulosis – diverticula with no inflammation

Inflammation of the stomach lining; “upset stomach”

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33-50



Heartburn

Hemorrhoids

Gastroesophageal reflux disease (GERD); stomach acids push into esophagus

Varicose veins of rectum or anus

Hepatitis

Hiatal hernia

Inflammation of the liver; various types

Portion of stomach protrudes into the chest through an opening in the diaphragm




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

33-51




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

33-52



Matching:

ANSWER:

A. Heartburn

B. Hemorrhoids

C. Constipation

D.

Crohn’s disease

E. Colitis

G. Gastritis

H. Diverticulitis

33-53


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.

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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.


In Summary (cont.)

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

33-56


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

33-57


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• Nutrients – necessary food substances

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