The Digestive System - Part 1

The body can be subdivided into organ systems

Organ Systems

It is convenient to consider these organ systems on their own, but keep in mind that they are all interconnected

Digestive SystemThe alimentary canal is basically a long, twisted, muscular tube, through which food is moved by rhythmic contractions (peristalsis)

bolus

contraction

smooth musclerelaxes

smooth musclecontracts behind the

bolus of food, pushing it downward

smooth musclecontracts

behind the bolus of food,

pushing it downward

contraction

Specialized organs help to break down the food that we eat into nutrients that can then be delivered to the body’s cells

Digestive SystemThe alimentary canal is basically a long, twisted, muscular tube, through which food is moved by rhythmic contractions (peristalsis)

Digestive System

tongue

stomachliver

pancreasgall bladder

esophagus

large intestinesmall intestine

rectum

anus

salivary glands

The process of digestion can be broken down into three parts:

Digestion

Physical Digestion

Chemical Digestion

Absorption

Physical Digestion

Physical digestion breaks food into smaller pieces, thereby increasing the surface area for chemical reactionsThis starts on your plate when you use a knife to cut your food and continues in your mouth when you chewSpecialized tooth morphology assists in the physical breakdown

Physical Digestion

incisor canine premolar molar

chopping tearing crushing grinding2 1 2 3

Human Dental Formula

I-2/2 C-1/1 P-2/2 M-3/3

Rhythmic contraction of the esophagus moves the bolus from your mouth to your stomachThere is a sphincter (muscular valve) at the entrance to the stomachThe stomach is a muscular organ which contracts to mix its contents

Your tongue and the moisture in saliva allow you to form a “bolus” of chewed food which is easier to swallow

Physical Digestion

Bile is secreted into the duodenum and emulsifies fat

By the time it leaves the stomach the food has been liquified (chyme)

Physical Digestion

diaphragmesophagus

cardiac sphincter

epithelial cells

longitudinal musclecircular muscleoblique muscle

pyloric sphincter

duodenum(small intestine)

Physical Digestion

The fat found in chyme will tend to

clump together

Molecules of bile are hydrophilic on one

side and hydrophobic on the other

They are able to physically break down large fat globules into smaller fat droplets, thereby increasing

surface area

This reduces the surface area for enzyme action

lipase

fat globule