Body SystemsDigestive

FunctionBreak down food into molecules to obtain

energy that the body needs: (ATP)

4 steps involved:

1. Ingestion- take food in2. Digestion- break down food3. Absorption- keep molecules body needs4. Elimination- get rid of waste

Digestion can occur in 2 waysMechanical- physical break down of the food-

occurs in the mouth using your teeth and also in the stomach due to churning.Purpose -- increase the surface area so more

sites are available for the enzymes to act upon.Chemical- enzymes break the bonds

in the food. This occurs in the mouth, stomach and small intestine.

Food Pathways We will follow the path of food beginning in the mouth until it reaches the point of elimination.MouthPharynxEpiglottisEsophagusStomachSmall intestine

Pancreas

http://www.youtube.com/watch?v=Z7xKYNz9AS0

LiverGallbladder

Large Intestine

Rectum

MouthSite of mechanical digestion. Teeth break

food into smaller pieces to increase surface area for the enzymes to work.

Have different teeth for different food types.Salivary glands release saliva to mix with

food. Contains SALIVARY AMYLASE- enzyme which breaks down carbohydrates.

Saliva also acts as lubricant to help food go down the esophagus.

Act of chewing and tongue form food into BOLUS before it is swallowed.

SwallowingWhen food is swallowed a small flap of tissue

called the EPIGLOTTIS covers the trachea (air pipe which leads to lungs) so food goes down the correct tube.

Esophagus-Muscle(smooth) covered tube that connects mouth to the stomach

Food is moved down the esophagus by waves of muscle contraction called PERISTALSIS

The Mouth and Pharynx

Peristalsis http://health.howstuffworks.com/adam-200088.htm

StomachMuscular pouchMechanical digestion- churning Chemical digestion-pepsin digests proteinsOther gastric juices and HCl (pH of 2)

digest the food (break the bonds between the molecules) and turns food into a soupy liquid called CHYME

Sphincter- acts as valves to let food into stomach

Stomach is covered in thick mucous to prevent HCL damage.

Takes 2-4 hrs for food to leave the stomach

Esophagus and Stomach

The Small Intestine6 meters longPyloric valve-valve between stomach

and small intestinesMade of 3 sections:

Duodenum ,Jejunum, and IleumMain site of absorptionPancreas-adds sodium bicarbonate

(NAHCO3) to balance PHAdditional enzymes added here from

small intestine, pancreas, liver and gall bladder

Small intestine

Structure of small intestineThe Small Intestine

isn’t a smooth tube- it has little finger like projections called villi and micro villi that help increase the surface area of the small intestine that allow for increased absorption.

The Accessory OrgansLiver and Gall Bladder

PancreasLiver produces

BILEBile helps digest

fat by surrounding the fat droplets so they break into smaller particles. (Emulsification)

Gall Bladder stores bile and delivers it when needed

Secrets enzymes for digestion (Pancreatic Juice)

Secretes Sodium Bicarbonate to balance PH in intestines

(Produces insulin-and glucagon to lowers and raise blood glucose levels)

Digestive EnzymesActive Site Enzyme Effect on food

Mouth SalivaryAmylase

Breaks down starches

Stomach Pepsin Breaks down proteins

Small intestine (from pancreas)

Trypsin

Amylase

Lipase

Continues the breakdown of proteinsContinues the breakdown of starchBreaks down fats

Small intestine

SucraseMaltaseLactaseLipasePeptidase

Breaks down remaining disaccharides into monosaccharidesBreaks down fatsBreaks down dipeptides into amino acids

Large IntestineMain function- Absorb waterProduce vitamin K with the help

of E. Coli bacteria that live in the large intestine

1.5 meters longTakes 18-24 hrs for waste to reach hereRectum-Storage of waste until it is

eliminatedTotal time for digestion and elimination -24-

33 hrs.

NutritionEnergy in food is measured in Dietary

Calories (Big C)1 Calorie = 1000 caloriesAverage American teenager needs to take in

2200-2800 Calories per day6 basic nutrients:

carbohydrates, fats, proteins, vitamins, minerals ,and water

CarbohydratesBread, pasta, fruitsMain source of energy for our bodyBreak down complex sugars into simple

sugars (glucose)Use glucose for ATP productionStore excess in liver as glycogen. Some gets

converted to fats for storage.1g carb = 4 Calories

FatsDairy, meats, nutsProvides energy and building blocks for your

CELL MEMBRANE (phospholipids) and hormones

Fats are broken down into fatty acids and glycerol

1g fat= 9 Calories

ProteinMeat, beans, eggsRaw material for growth, repairs skin

and muscleAlso used in transport and regulatory

functions such as hemoglobin and insulin.Broken down into the individual amino acids

(20 essential) to make enzymes, antibodies, hormones

Also need Nitrogen to make DNA and RNA for mitosis and protein production

1g protein = 4 Calories

Vitamins Vitamins are organic molecules that help to

regulate body processes-Vitamins used to maintain growth and

metabolism.Needed in small amountsTwo kinds- fat soluble- D, E, K, A

Can be stored in bodyand water soluble.- B1, B2, B6, B12, C,

Niacin, Folic Acid, Biotin, Choline, Pantothenic AcidCan not be stored in body.

MineralsInorganic nutrients that the body needs.Minerals used for building material or in

cellular reactions. Need small amountsInorganic substances like

Fe, Ca, Na, Cl, Mg, P, K, S, I

WaterFacilitates reactions and maintains

homeostasis

Makes up the bulk of blood, lymph and body fluids

Average person needs to take in at least 1 liter /day

Loose water through urine, sweating and exhalation

2000 Calories