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Website:

websites.rcc.edu/halama

Lecture 2

Digestive System

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Lecture 3

1. Introduction

2. Digestive System

3. Nutrition Basics

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Introduction

Some Ecology

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Mr. Sun

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Nuclear Fusion

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Light energy from Sun…

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…radiates across space.

Light energy from Sun…

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…radiates across space.

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strikes the Earth’s surface… 9

A very small percentage…

Light Energy Absorbed…10

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Photosynthesis

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Energy stored here

Plants! Important!

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Consumers

Digestive System

• Begins the process of “harvesting” the solar

energy, and other things, contained within food.

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Digestive System

Breaks down ingested food (large molecules) into

small molecules, via mechanical and chemical means.

Digestive System

The material is absorbed by the body and used for

various functions where needed.

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Digestive System

• Begins the process of “harvesting” the solar

energy, and other things, contained within food.

• Breaks down ingested food (large molecules) into

small molecules, via mechanical and chemical

means.

• The material is absorbed by the body and used for

various functions where needed.

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Digestive System

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Digestive System, Five Functions

1. Breaks up food into small pieces

2. Transports food through the alimentary canal

(gut) via rhythmic muscular contractions

(peristalsis)

3. Secrets digestive enzymes to breakdown food

4. Absorbs nutrients into the bloodstream

5. Excretes solid wastes of digestion (whatever

is left over).

Digestive System

1. Mouth (Buccal Cavity)

2. Esophagus

3. Stomach

4. Small Intestines

5. Large Intestine (Colon)

6. Secretory Glands (Salivary Glands, Liver,

and Pancreas)

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Mouth

• Teeth, mechanical

breakdown:

• Salivary Glands - Saliva,

mixes with food and

begins chemical

breakdown.

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Teeth!

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Esophagus…

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Esophagus

• Connecting tube between the pharynx and

the stomach, or between pharynx and

intestine.

• Peristalsis

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Muscles

Contracted

Peristaltic Contractions – waves of rhythmic relaxation and

contraction of the muscles in the alimentary canal that move

along the canal and act to push the contents from the mouth

toward the rectum.

Muscles

Relaxed

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Esophagus Specialization:

Egg Eating Snake

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Stomach

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Stomach Cardiac Sphincter

Pyloric Sphincter

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Lining of the Stomach: Gastric Pits

Cells secrete Hydrochloric Acid (HCl)

Lining of the Stomach: Goblet Cells

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These cells secrete mucous - protects the

stomach lining

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Stomach

Cardiac Sphincter

Pyloric Sphincter

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When empty, the stomach is contracted and the lining is

“bunched up” into distinct folds called Rugae; when distended

with food, the rugae flatten out.

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Stomach - ingest Cardiac Sphincter,

Open

Pyloric Sphincter, Closed

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Cardiac Sphincter,

Closed

Pyloric Sphincter, Closed

Stomach - peristalsis

Chyme

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Gastroesophogeal Reflux Disease

(GERD)Cardiac Sphincter,

Open

Pyloric Sphincter, Closed

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Bird Stomach

ProventriculusGizzard

Sphincter Sphincter

Posterior EndAnterior End

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?

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Dinosaur

Gastroliths

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Intestines

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Intestines Serve Three Main

Functions:

1. Continues the digestive process begun by

the mouth and stomach

2. Selectively absorbs final products of

digestion

3. Moves the food through the system via

peristalsis.

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Intestine Regions

1. Small Intestine – where digestion and

nutrient absorption takes place.

2. Large Intestine (Colon):

A. Reabsorb water

B. Consolidate feces.

C. Synthesizes Vitamin K which is necessary for

blood clotting.

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Small Intestine:

Three Sections

1. Duodenum – chemical digestion

2. Jejunum – absorption

3. Ileum - absorption

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Duodenum

• shortest part of the small

intestine (~ 25 - 30 cm),

• site of most chemical digestion

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Duodenum

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Jejunum

• Jejunum - Second longest part

of the small intestine (~ 2 - 3

meters),

• Main site of nutrient

absorption in Small Intestine

• Most of the nutrients present in

food are absorbed by the

jejunum before being passed on

to the ileum for further

absorption.

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Ileum

• Ileum - longest part of

the small intestine (~ 2 -

4 meters),

• Absorbs vitamins (B12)

and water,

• And anything not

absorbed by the illium.

Absorption?

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Absorption?

Villi and Microvilli increase surface area!

~250 square meters (almost 2,700 square

feet) – the size of a tennis court!

Without Villi and Microvilli, surface area

would be about 15 -20 square feet.

Large Intestine (Colon)

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Large Intestine (Colon)

1. Primary Function – water absorption and

feces consolidation.

2. Vitamin K produced by bacteria

What about the appendix?

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A thin tube about four inches long, located at the junction of

the small intestine and large intestine in the lower right

abdomen.

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What about the appendix?

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Once thought to be a “vestigial” organ – an organ that once

served a purpose in our evolutionary past, but no longer

serves any function.

What about the appendix?

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NOW, is believed to serve an important function – a haven for

useful gut bacteria when illness flushes those bacteria from

the rest of the intestines.

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What about the appendix?

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Appendicitis - for unclear reasons, the appendix often becomes

inflamed, infected, and can rupture. This causes severe pain in

the right lower part of the belly, along with nausea and vomiting.

Secretory Organs

Salivary Glands, Liver, and

Pancreas

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Salivary Glands

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Saliva – enzymes that begin carbohydrate digestion

Liver and Gall Bladder

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Does lots of different stuff !

Produces Bile. Stored in the Gall Bladder. Bile

aids in fat digestion.

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Pancreas

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