Digestive System

DigestionProcess of breaking down food

into usable materials

Mouth

Mechanical Digestion- physically breaking food down into smaller pieces, increases surface area so digestive juices and enzymes have more area to interact with our food

Carried out by our teeth cutting, crushing and chewing our food. Also aided by our tongue(muscle) which helps to mash and initiate the swallowing response

Mouth

Chemical Digestion- the changing of complex food molecules (Carbohydrates, Starches, Proteins) into simpler substances that can be absorbed into our blood stream and used by our cells.

MouthChemical digestion begins in the

mouth, saliva acts on starches beginning to break them into simple sugars. Saliva also helps to soften and lubricate our food for its trip through the digestive tract

Amylase is the enzyme in our saliva that begins chemical digestion. It breaks starches down into simple sugars

MouthOur teeth, tongue and saliva

work on the food we eat to create a soggy ball of food and saliva called a bolus. When the bolus is moved to the back of the mouth the swallowing response is triggered.

Mouth

When the bolus is swallowed it is passed from the mouth to the esophagus.

The mouth is about 11cm long.

Esophagus

The esophagus is a 25cm tube that’s connects the mouth to the stomach. It is one of two tubes in the throat, the other is the trachea which leads to our lungs. The epiglottis covers the trachea when we swallow to keep food and liquids from entering our lungs.

Esophagus

If food gets lodged or stuck in the back of the throat before the epiglottis, choking can occur.

Esophagus

Food is moved down the esophagus by muscular contractions called peristalsis, a squeezing motion that pushes food through our digestive system.

Peristalsis

Wave-like contractions of smooth muscle that line our digestive tract to keep food moving through our digestive system.

Smooth muscle is muscle that we do not consciously control, so digestion is an involuntary response.

Esophagus

At the end of the esophagus is a valve that keeps food and digestive juices from the stomach from backing up into the esophagus. These valves are circular muscles called sphincters

EsophagusIf stomach acid comes up past the

sphincter muscle into the esophagus you may experience pain often called heartburn. Heartburn has nothing to do with your heart, but because the pain seems to be where the heart is it was originally called heartburn. In bad cases stomach acid can actually begin to eat at the esophagus.

StomachThe stomach is a 22cm long organ

surrounded by three layers of smooth muscle. Each layer of muscle runs in a different direction to make sure our food is thoroughly mashed. The mashing of the stomach muscles is a type of ________________ digestion.

StomachThe stomach wall contains many

glands that secrete digestive juices and mucus. Mucus is needed to protect the stomach wall from the acids and digestive enzymes needed to chemically break down our food.

Stomach

If the glands do not produce enough mucus to keep the stomach wall covered the digestive juices will begin eating at the stomach wall causing an ulcer

StomachThe Stomach’s digestive juice is made up of

Hydrochloric Acid (HCl) and an enzyme called pepsin. These two compounds work together to chemically digest proteins.

Stomach contains HCl and pepsin to digest proteins.

The work of the stomach muscles and digestive juices turn the food we eat into Chyme.

Small IntestineChyme enters the small intestine a

little at the time through the pyloric sphincter. The first portion of the small intestine is very important and has been named the duodenum. The duodenum is the first 25cm of the small intestines. In this section of the small intestine most chemical digestion occurs.

Small IntestineIn the duodenum, bile from the liver

and gallbladder as well as Pancreatic Juice from the pancreas go to work to finish digesting our food.

Pancreatic Juice- basic to neutralize stomach acid, packed with enzymes to digest carbohydrates, proteins and fats

Small Intestine

Pancreas secretes about 1.5 liters of pancreatic juice a day.

Without the enzymes in the pancreatic juice our bodies would not be able to break down the foods we eat and get the nutrients we our body needs.

Small Intestine

Our Liver produces bile, which is stored and concentrated in the gall bladder.

Also in the duodenum bile is added to the chyme from our stomach to break down fats.

Bile is a lot like dish soap, it breaks large fat molecules into smaller fat globules. These now smaller fat globules are broken down further by bile and pancreatic juices.

Small Intestine

Fats are broken down into fatty acids and glycerol that can be absorbed into the blood stream and used by our cells.

The rest of the 690 cm long small intestine is lined with folds containing villi and microvilli.

Villi and microvilli are small finger like straws that absorb the digested nutrients into our bloodstream.

Small IntestineAbsorption- process in which digested

nutrients pass through the wall of the small intestine into the bloodstream.

The small intestine is responsible for absorbing the nutrients from our digested food.

Large Intestine The large intestine is a 152 cm long, its

job is to remove water and minerals from the undigested food.

The large intestine doesn’t produce any enzymes because all of the food that can be digested has been broken down.

Large IntestineThe Large Intestine is also referred to

as the colon.At the end of the large intestine is 14

cm vault called the rectum.The rectum stores and compacts

undigested food, called feces, until it can be eliminated through the anus.

Review

The Mouth carries out mechanical digestion and chemically digests carbohydrates and starches using the enzyme amylase that’s in our saliva

The Stomach carries out mechanical digestion by mashing our food with 3 layers of muscle

Chemically the stomach uses gastric juice made up of HCl and pepsin to digest proteins

Review

The Small Intestine is responsible for most chemical digestion in our body

The duodenum or first 25cm of the small intestine is where bile and pancreatic juice chemically digest carbohydrates, fats, and proteins.

The rest of the small intestine is full of villi that absorb the digested nutrients into our bloodstream

Review

Materials that were not digested or absorbed in the small intestine or passed to the large intestine.

The large intestine absorbs water and minerals from the undigested matter (feces) and compacts it for excretion through the anus.

Review

CarbohydratesStarches and sugars are broken down by amylase to simple sugars like glucose that can be used by our cells for energy

ProteinProtein is broken down by gastric juice in the

stomach to amino acids so our cells can build the proteins our body needs

Review

FatsFats are broken down by bile and pancreatic

juice into lipids, glycerol, and fatty acids that can be used for energy, cushioning and insulation in our body.

Test

Students need to be able to:Label a diagram of the digestive systemIdentify the function of each organ and which

nutrient group is digested Identify which enzyme or digestive juice breaks

down each nutrient