Digestion

2006-2007

Animal andHuman

Digestion

Digestive System – Objectives

Describe and understand the basic functions of the primary components of the digestive system.

Compare the functions and locations of the digestive organs in man and animals.

Differentiate between and identify digestive systems of man and animals.

Digestion Digestion is the breakdown

of large, complex organic molecules into smaller components that can be used by the body.

Molecules need to be small enough to diffuse across plasma membranes.

HUMAN DIGESTION

Four Components of Digestion Ingestion – this is the consumption of

or taking in of nutrients. Digestion – the chemical breakdown of

large organic molecules into smaller components by enzymes.

Absorption – the transport or delivery of digested nutrients to body tissues.

Egestion – the elimination of food waste materials from the body.

Ingestion

Food enters the human digestive tract through the mouth or oral cavity.

Humans are considered chunk feeders because they consume chunks of food that are then mechanically broken down.

Mouth Teeth

mechanically break down food into small pieces. Tongue mixes food with saliva (contains amylase, which helps break down starch).

Epiglottis is a flap-like structure at the back of the throat that closes over the trachea preventing food from entering it.

Mouth

Esophagus Approximately 10” long Functions include:1. Secrete mucus

2. Moves food from the throat to the stomach using muscle movement called peristalsis

If acid from the stomach gets in here that’s heartburn.

Esophagus: muscular tube that connects mouth to stomach–Peristaltic waves send feed down the

esophagus, (muscle contractions).–Reverse Peristalsis = blowing chunks–The cardia, located at the end of the

esophagus prevents feed in the stomach from coming back into the esophagus. ( non-ruminants only)

Stomach J-shaped muscular bag that

stores the food you eat, breaks it down into tiny pieces.

Mixes food with digestive juices that contain enzymes to break down proteins and lipids.

Acid in the stomach kills bacteria.

Food found in the stomach is called chyme.

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Small Intestine Small intestines are roughly

7 meters long

Lining of intestine walls has finger-like projections called villi, to increase surface area.

The villi are covered in microvilli which further increases surface area for absorption.

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Small Intestine Nutrients from the food pass

into the bloodstream through the small intestine walls.

Absorbs:– 80% ingested water– Vitamins– Minerals– Carbohydrates– Proteins– Lipids

* Secretes digestive enzymes14

Large Intestine

About 5 feet long Accepts what small

intestines don’t absorb

Rectum (short term storage which holds feces before it is expelled).

Large Intestine

Functions– Bacterial

digestion• Ferment

carbohydrates

• Protein breakdown

– Absorbs more water

– Concentrate wastes

Accessory Organs

Not part of the path of food, but play a critical role.

Include: Liver, gall bladder, and pancreas

Liver

Directly affects digestion by producing bile–Bile helps digest fat

• filters out toxins and waste including drugs and alcohol

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Gall Bladder

Stores bile from the liver, releases it into the small intestine.

Fatty diets can cause gallstones

Pancreas

Produces digestive enzymes to digest fats, carbohydrates and proteins

Regulates blood sugar by producing insulin

Understanding the Digestive Systems

Ruminants Non-ruminants

A RUMINANT ANIMAL

Has four distinctive compartments in

its stomach, which swallows its food

essentially unchewed, regurgitates, and

chews it thoroughly and reswallows it

again.

Examples include cattle, sheep, goats,

deer, rhinos, and elk.

Rumination (regurgitation) After rumen if full, it lies down to ruminate

(chew its cud)

Cattle spend from 5-7 hours ruminating, broken up into 6-8 periods

Regurgitation is the process of forcing the feed back into the mouth for chewing

Done through a series of muscular contractions and pressure in the rumen and reticulum

A NONRUMINANT ANIMAL

Has a single compartment in its

stomach, which swallows its

food after chewing and does not

regurgitate its food.

Examples include pigs,

humans, bears, and dogs.

Nonruminant Digestion

food is

swallowed

directly into

the single

stomach

compartment

it is mixed

with digestive

juices

What do animals need to live? Animals make energy

using:– food– oxygen

Animals build bodies using:– food for raw materials

• amino acids, sugars, fats, nucleotides

– ATP energy for synthesis

O2

food

ATP

mitochondria

How do animals get their food?

filter feeding living in your food

fluid feeding bulk feeding

Getting & Using Food Ingest

– taking in food Digest

– mechanical digestion• breaking up food into smaller pieces

– chemical digestion• breaking down food into molecules

small enough to be absorbed into cells

• enzymes Absorb

– absorb nutrients across cell membranes• diffusion• active transport

Eliminate – undigested material passes out of body

intracellulardigestion

extracellulardigestion

Different diets; different bodies Adaptations of herbivore vs. carnivore

– teeth– length of digestive system– number & size of stomachs

Teeth Carnivore

– sharp ripping teeth

– “canines” Herbivore

– wide grinding teeth

– molars Omnivore

– both kinds of teeth

Length of digestive system

Herbivores & omnivores– long digestive

systems– harder to digest

cellulose (cell walls)• bacteria in

intestines help Carnivores

– short digestive systems

– protein easier to digest than cellulose

appendix

Fun Facts

• HOW LONG ARE YOUR INTESTINES? At least 25 feet in an adult. Be glad you're not a full-grown horse -- their coiled-up intestines are 89 feet long!

• Food drying up and hanging out in the large intestine can last 18 hours to 2 days!

• In your lifetime, your digestive system may handle about 50 tons!!

Write the name of each colored organ:

Green: Red: Pink: Brown: Purple: Green: Yellow:

How’d you do? Green: Esophagus Red: Stomach Pink: Small

Intestine Brown: Large

Intestine Purple: Liver Green: Gall Bladder Yellow: Pancreas

Great Job!