Digestive System A closer look. Digestive Processes In order for our bodies to use the food we eat...

Digestive System

A closer look

Digestive Processes

In order for our bodies to use the food we eat to grow, energize, and repair our cells, 5 digestive processes have to occur.

These include: Ingestion Movement Digestion Absorption Egestion (excretion)

Digestive Processes

These processes occur at different locations along the digestive tract, which is a continuous tube from mouth to anus.

We are going to discuss what happens at each site as we go through the stages.

It will be useful to copy the following concept map and to keep adding to it as we add more details to help you stay organized.

NOTE: This should be a straight line in your notes

Mouth/

Throat

Esophagus

StomachSmall

Intestine

Large

Intestine

Rectum/

AnusTeeth

Salivary Glands

Tongue

Includes organs which perform digestion tasks:Digestive Tract (Gastrointestinal Tract, G. I.

Tract) includes: mouth, esophagus, stomach, small intestine, large intestine or colon, and anus.

Accessory Structures include:, tongue, salivary glands, liver, gall bladder and pancreas.

Digestive System

Digestion

The process in our bodies that breaks down food for use by our cells. This is done in two ways:Mechanical: our teeth chewing through the food

Chemical: enzymes breakdown food into absorbable molecules.

Mouth (where it all begins)

Four main parts of the mouth Teeth Tongue Salivary Glands Hard and Soft

Palates

Uvula

Hard Palate

Mouth

Teeth (Chewing) Mechanical Digestion Are covered by enamel,

the hardest structure of the body

Their movements slice, tear, grind and mix food

Incisors: snap off pieces of food

Canine: tearing pieces apart

Premolars & molars: grind food to a paste How many teeth in adult

humans?

Tongue

Floor of oral cavityComposed of voluntarily controlled muscle

tissueRole: Guides food during chewing and

swallowingMajor taste buds are embedded here.

Salty, sweet, sour, bitter

Salivary Glands

Release saliva in response to the smell, taste, and thought of food

First example of chemical digestion: Contains Amylase: an enzyme that begins

breakdown of starch into simple sugars, like glucose or table sugar.

Interesting Fact: We secrete about 1-2L of saliva per day!

Hard & Soft Palates

Separate mouth from nasal cavity, so food doesn’t go up your nose!Located at the roof of your mouth.

Uvula (dangles)Just beneath the soft palatePrevents food from entering nasal

passages by raising up.

Hard Palate Soft Palate

Epiglottis

Trachea

TongueUvula

Recap (Mouth)

Food enters Teeth rip, tear, and chew into smaller pieces to

swallow At the same time, Salivary Glands are stimulated

to release saliva which contains amylase. Tongue pushes bolus to back of pharynx (throat)

and the uvula elevates, closing off the nasal passage. The bolus now pushes the epiglottis which closes the opening of the larynx, preventing the food from entering the wrong tube, which results in choking

Esophagus

Muscular tube which extends from pharynx (throat) to the stomach

Swallowing initiates peristalsis, a wave of contraction which initiates just above the “bolus” (substance) and moves it towards the stomach.

This movement also occurs in the stomach and in the intestines.

http://pennhealth.com/health_info/animationplayer/

Esophagus

Secretes mucus (along with the rest of the digestive tract)

This lubricant decreases the likelihood of the esophagus getting damaged by any sharp edges from the food entering. Mucus also protects esophagus from acid and

enzymes in gastric juice if reflux were to occur.http://digestive.niddk.nih.gov/ddiseases/pubs/gerd/


Mouth/

Throat

Esophagus

StomachSmall

Intestine

Large

Intestine

Rectum/Anus

TeethSalivary Glands

Tongue

Mechanical: Chewing

Chemical: Starch/Amylase

Mechanical: Peristalsis

Stomach

Separated from esophagus by the Gastro esophageal sphincter

Expandable muscular J-shaped sac that can hold up to 2-4 liters of food and liquid

Secretes mucous to protect lining cellsContents are held in the stomach by the

pyloric sphincter, ring of circular muscle, which separates the stomach from upper small intestine

Stomach

3 Functions Stores food and releases it

gradually into the small intestine

Assist in mechanical breakdown of food by peristalsis and contractions of muscular walls

Chemical breakdown of food by enzymes and other substances.

Stomach

Secretions (continued) Gastrin: hormone that stimulates secretion of

Hydrochloric acid (HCl) Pepsinogen: inactive form of enzyme is

activated by HCl and transformed into pepsin which helps breakdown proteins into amino acids (smaller units).

Stomach

Food is gradually converted into a thick liquid called chyme which consists of partially digested food and digestive secretions.

Chyme is propelled towards small intestineThe Pyloric sphincter lets a teaspoon of

chyme into the small intestine during each contraction

Takes around 2-6 hours to empty stomach


Mouth/

Throat

Esophagus

StomachSmall

Intestine

Large

Intestine

Rectum/Anus


Tongue

Mechanical: Chewing

Chemical: Starch



Mechanical: Muscle Contractions

Chemical: Pepsin (Proteins), HCl

Small Intestine (S. I.)

Narrow tube (1-2 inches in diameter)

Longest part of digestive tract

Split into three parts: duodenum, jejunum, and the ileum

Function: to digest food into small molecules and absorb into blood stream and lymph vessels.

Small Intestine (S. I)

Helped by three other sources:1. Liver: Has many

functions in our bodies. In digestion, it produces bile which is stored in the gall bladder, then released in the S. I.

Bile is made up of bile salts, water, and other salts and assist in the breakdown of lipids.

http://zap.intergate.ca/images/liver%20image.jpg


2. Gall Bladder stores bile until it’s needed for digestion

http://www.nlm.nih.gov/medlineplus/ency/imagepages/19260.htm


3. Pancreas Located between stomach and

S. I. Cells produce pancreatic juice

which neutralizes the acidic chyme it receives from the stomach

Digests carbohydrates, proteins, and lipids

Contains water, sodium bicarbonate, and many enzymes

YouTube - Pancreas - "Weird Al" Yankovic


Small Intestine (S. I)

Pancreas (cont’d) Enzymes include:

Amylase Carbohydrates Lipase Lipids Proteases Proteins and peptides


Specialized cells within the wall complete the process. At the same time, nutrients are absorbed into the blood stream.

The numerous folds and projections, called villi, give the internal surface area a much larger surface for absorption.http://www.udel.edu/biology/Wags/histopage/wagnerart/

anaglyphpage/anaglyph.html


The area of absorption is also increased by the millions of microvilli.


Mouth/

Throat

Esophagus

StomachSmall

Intestine

Large

Intestine

Rectum/Anus


Tongue

Mechanical: Chewing

Chemical: Amylase-Starch



Peristalsis (3 layers)

Chemical: Pepsin-Proteins

HCl: pH-2

(gastric juices)

Chemical: Amylase-CH2O

Lipase-Lipids

Proteases-Proteins


Bile emulsifies lipids

Macro & micronutrients absorbed

Alcohol absorbed

Are We There Yet?

Almost…

While the nutrients are being absorbed by these cells, chyme is being mixed back and forth by segmentation movements within the small intestine.

When absorption is complete, undigested material moves into the large intestine.

Large Intestine (L. I.)

Is about 5 feet long and 3

inches in diameter in adults Two parts:

Colon (for most of its length)

Rectum: the final 6”

Receives leftovers of digestion: water mixture, undigested fat and proteins, indigestible fibers



Contains large populations of bacteria that thrive on the unabsorbed nutrients and are also responsible for synthesizing important vitamins for the body (B12, riboflavin, K).

Remaining water, salts, and vitamins are reabsorbed by cells in the L. I.


Mouth/

Throat

Esophagus

StomachSmall

Intestine

Large

Intestine

Rectum/Anus


Tongue

Mechanical: Chewing

Chemical: Amylase-Starch



Peristalsis (3 layers)

Chemical: Pepsin-Proteins

HCl: pH-2

(gastric juices)

Chemical: Amylase-CH2O

Lipase-Lipids

Proteases-Proteins


Bile emulsifies lipids

Macronutrients absorbed

Remaining water, salts and vitamins absorbed


Leftover material is condensed into semisolid feces which are transported to the rectum by peristaltic movements.

Expansion of the rectum stimulates the urge to defecate which is initiated voluntarily after age 2.

The Facts About Poop

The Facts About Poop

Digestive System A closer look. Digestive Processes In order for our bodies to use the food we eat...

Documents

Transcript of Digestive System A closer look. Digestive Processes In order for our bodies to use the food we eat...