The Science of Digestion

7/29/2019 The Science of Digestion

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The Science of Digestion


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What is Digestion?

Organisms need nutrients in order to survive and thrive.

The act of absorbing food and delivering it to the

individual cells in a useable form is the basis for

digestion.


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What is Digestion?

In single celled organisms the primary mode of food absorption is

pinocytosis. Food is absorbed into the cell and then broken down

to be used to produce energy.

In multi celled organisms the process is much more complex

individual cells are specialized and unable to absorb food in the

same fashion as single celled organisms. Instead they use a

specialized digestive system that breaks down food and relies onthe circulatory system to deliver useful substances to individual

cells to be absorbed.


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The digestive system

There are several processes and anatomical structures involved in

digestion. In order to fully understand digestion we must first

examine these processes

The pathway by which food travelsthe digestive tract

The mechanical movement of this food through this tract

The chemical digestion of food

The rolls of the digestive organsdigestive tract, liver, pancreas

and gall bladder


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Reproduced with permission from http://www.uclan.ac.uk/facs/health/nursing/sonic/scenarios/scenario1GITlecture.htmMarch 28th 2005

The Human Digestive System
http://www.uclan.ac.uk/facs/health/nursing/sonic/scenarios/scenario1GITlecture.htmhttp://www.uclan.ac.uk/facs/health/nursing/sonic/scenarios/scenario1GITlecture.htm


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The Tube System

This digestive model functions on what can be

simplified as a large tube arrangement.

This Tube system is separated by a series of

sphincterswhich are essentially openings

controlled by muscles through the system.


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The Tube System

There are four main sphincter muscles along the alimentary

canal that aid in digestion:

The cardiac sphincter, between the esophagus and thestomach, opens at the approach of food, which is then swept

into the stomach by rhythmic peristaltic waves

The pyloric sphincter controls the opening from the stomach

into the duodenum. It is usually closed, opening only for amoment when a peristaltic wave passes over it.

Two anal sphincters, internal and external, control the anus,

allowing the evacuation of feces.


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The Tube System

This system functions on the idea of compartmentalization,where different compartments are capable of specificfunctions allowing concentration gradients of biologicalsubstances for digestion.

For Example The concentration of HCl in the Stomachwhich if allowed to flow through the system would ultimately

break down much of the bodies tissues.

Compartmentalization allows the concentration of these fluidsin one compartment and the neutralization of them in anotherin order to efficiently process ingested foods.


9/20Reproduced from McGraw-Hill Ryerson Biology 11 1st edition 2001

Structure & Function

of the Human

Digestive Tract


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The Mouth

Type a detailed list of the items you needed to complete your

experiments.

Be specific about the amounts used.


Food enters the body through the mouth. Here it is shredded by the teeth

and mixed with salivary amylase and lingual lipase to commence starch

and fat digestion.


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The Esophagus

Food passes from the mouth to the stomach

via the esophagus which is about 24 cm long.

The esophagus is lined with longitudinal and

circular muscles along its length which is

lubricated with Mucin, secreted by tubular

glands found in the back of the throat.

These muscles work to push the food into the

stomach after swallowing.


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The Stomach

The stomach is a muscle lined sack

that contains glands that secrete

gastric juices that aid in the

physical and chemical breakdown

of food.

The stomach contains an oblique

layer of muscles that work to

physically break down food into a

thick liquid known as chyme



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The Small Intestine



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The Small Intestine

Type a brief summary here of what you discovered based on the

results of your experiments. You need to indicate whether or not the

data supports the hypothesis and explain why or why not.



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The Small Intestine

Vili in the small intestine have a

fine layer of microvili designed to

further increase the surface area, and

thus the rate of nutrient absorption.

Intestinal glands are found between

the vili which are designed to secrete

intestinal juices keeping the

intestinal environment ideal for

absorption by the body.



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The Large Intestine

The Large intestine transports

undigested food and water and

dissolved minerals are absorbed

aided by intestinal bacteria.

The bacterias by products are

vitamin B-12 and K along with

various amino acids, which are all

beneficial and absorbed by the

body.

The remaining digested food, also

known as feces passes into the

rectum and is passed through the

anus.Reproduced with permission from http://www.uclan.ac.uk/facs/health/nursing/sonic/scenarios/scenario1GITlecture.htmMarch 28th 2005


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Food Movement - Peristalsis

Food is not simply pushed through the digestive

system, instead the various forms of food are moved

through muscle contraction.

This muscle contraction in tubular compartments is

called peristalsis and describes a contraction wave

type movement.

Peristalsis is not only used to mechanically movefood forward but also to churn and mix digestive

juices into the chyme.


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The Living Model

Image Source: http://www.sdmesa.sdccd.net/~bbrothers/Pages/Digestive_Flat_model.htm March 28, 2005


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The Living Model

Image retrieved from http://library.thinkquest.org/15401/learn_idiagram_dig.html March 28, 2005

Diaphragm

Gallbladder

Liver

Pancreas

Small

Intestine

Stomach


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The Science of DigestionSenior Biology

Appleby College

C. Watt

V1. 2005-03-29

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The Science of Digestion