Essentials of Human Anatomy & Physiology

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Seventh EditionElaine N. Marieb

Chapter 14The Digestive System and

Body Metabolism

Main Functions:1. Digestion: Breakdown of

ingested food

2. Absorption: Passage of nutrients into the blood

3. Metabolism: Production of cellular energy (ATP)

Organs of the Digestive System

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Figure 14.1

Organs of the Alimentary Canal

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Oral Cavity

∙ Pharynx

∙ Esophagus

∙ Stomach

∙ Small intestine

∙ Large intestine

∙ Anus

Contains:

tongue and teeth- used in mechanical digestionsalivary glands- secretes saliva, used in chemical digestion

Oral Cavity (Mouth)

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Figure 14.2a

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Mechanical digestion: breaking down food into smaller pieces, so they can more easily be chemically digested; ∙Mixing of food in the mouth by teeth and

tongue∙Churning of food in the stomach∙Segmentation in the small intestine

Mechanical Digestion in Mouth

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Teeth mash and pull apart food material; the tongue pushes material around;

food that leaves the mouth is known as “bolus”

Figure 14.2a

Chemical Digestion: breaking down macromolecules into smaller pieces via enzymes.

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salivary glands: saliva-producing glands

saliva: a watery substancethat containsenzymes,mucus, andantibiotic molecules

3facts vid: http://quietyoutube.com/watch?v=bYudf5iSJ_M&app=desktop

Chemical Digestion

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amylase: enzyme in saliva that breaks chemical bonds in carbohydrate macromolecules (starches in food)

Figure 14.2a

Chemical Digestion

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enzyme: protein molecules that speed up/slow down chemical reactions1.2 vid: https://www.youtube.com/watch?v=r1ryDVgx0zw

Chemical Digestion

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amylase: enzyme in saliva that breaks down carbohydrates into simple sugars (glucose, maltose, etc.)

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carbohydrates: macromolecules made up of carbon, hydrogen, and oxygen atoms (in a 1:2:1 ratio);

a polysaccharide (polymer) made up of monosaccharides (monomers): Ex. glucose & fructose

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carbohydrates: chemically digested starting in the mouth, this polymer category includes starches and fiber

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salivary amylase

Detecting Carbohydrates

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reagent: a substance that is used to test for the presence of another substance by causing a chemical reaction with it

Benedict’s Solution serves as an indicator of monosaccharides in a substance.

Detecting Carbohydrates

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If there are sugar molecules in

a substance,

then the blue indicator will turn

orange-red.

Oral cavity ->Pharynx->Esophagus

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Serves as a passageway for air and food

Figure 14.2a

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The epiglottis is a small flap that opens and closes to prevent food from entering the trachea.

∙ Swallowing food triggers it to close covering the opening to the trachea.

EsophagusRuns from pharynx to stomach through the diaphragm

Moves food toward stomach peristalsis (slow rhythmic squeezing)

Passageway for food only (respiratory system branches off after the pharynx)

-Layers of Alimentary Canal Organs

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Figure 14.3

peristalsis: rhythmic muscular contractions that squeeze food through the esophagus to the stomach

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chyme: mixture of stomach fluids andfood produced in the stomach bycontracting stomach muscles

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stomach: large muscular sac that conducts mechanical and chemical disgestion;

End product of stomach digestion = chyme, sent to the small intestine

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Stomach Anatomy

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Acid reflux!

∙ Ulcers are caused when the stomach acids and enzymes begin digest the stomach itself.

∙ H.Pylori is a bacteria known to cause ulcers.

∙ Blood tests can reveal the presence of H. Pylori

∙ Endoscopy is used to look for ulcers.

Stomach Anatomy

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small intestine: the body’s major digestive organ;

Interior wall is lined with villi;

Site of nutrient absorption into the blood

Chemical Digestion: breaking down macromolecules into smaller pieces via enzymes.

Chemical Digestion: breaking down macromolecules into smaller pieces via enzymes.

Chemical Digestion: breaking down macromolecules into smaller pieces via enzymes.

enzymes: proteins that speed up decomposition chemical reactions;breaks down food into smaller pieces, to aid in absorption of nutrients

-amylase in the mouth-pepsin in the stomach

Absorption in the Small Intestinevilli: finger-like structures that increase surface area

-Contains a network of blood vessels and lymphatic vessel

-Enzymes break down food molecules. When small enough, molecules diffuse through cell membrane and nutrients are transported through the blood.1video: http://quietyoutube.com/watch?v=AJ1wKsmBPvA

6.2http://quietyoutube.com/watch?v=32gNePkj1_4

Large Intestine

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organ that removes water from the undigested materials that pass through it

Large Intestine

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Figure 14.8

colon: Ascending, transverse, descending, S-shaped tube (synonym for large intestine)

rectum: last 6-8 inches of the large intestine

anus: external body opening, containing

two sphincters

Accessory Digestive Organs

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∙ Salivary glands∙ Teeth∙ Pancreas∙ Liver∙ Gallbladder

PancreasProduces enzymes that break down all categories of food.

∙ Enzymes are secreted into the duodenum of the small intestine

∙ Alkaline fluid introduced with enzymes neutralizes acidic chyme

∙ Endocrine (hormone) products of pancreas

∙Insulin

∙Glucagons

Liver

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∙ Largest gland in the body

∙ Digestive role:produces bile.

∙ Has four lobes

organs360: https://www.youtube.com/watch?v=zs5_oQxCsaM

Bile

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∙ Produced by cells in the liver∙ Components that “digest” non

enzymatically

(typically fats)

Role of the Liver in Metabolism

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∙ Several roles in digestion∙ Detoxifies drugs and alcohol∙ Degrades hormones∙ Produce cholesterol, blood proteins

(albumin and clotting proteins)∙ Plays a central role in metabolism

Gall Bladder

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-Sac under liver

-From the liver, bile stored enters the small intestine at the duodenum

-Bile is introduced in the presence of fatty food