The Digestive System

What is the Digestive System?• The digestive system is the organ system

which takes in food, digests it and excretes the remaining waste

• The system is made up of the digestive tract organs and the accessory organs

• In animals, it is essentially a long tube with a beginning and an end.

• As animals become more complex, so do their digestive systems.

The Amoeba – An example of a simple digestive system.

The Earthworm – An example of a simple but long digestive system

The Frog – an example of a digestive system similar to humans, but less complex

The Cow – an example of a digestive system specially designed for a specific food intake

The Human Digestive System

• The entire length of the digestive tract is lined with epithelial tissue

• Some of the cells in the tissue secrete mucous which helps protect the tract from digestive enzymes and allow the food to pass smoothly along the tube.

The Path of Food – Digestive OrgansThe Mouth

• Two types of digestion occur here:

1. Mechanical Digestion – teeth chewing food.

2. Chemical Digestion – saliva starts to break down food.

The Tongue• small cells called

chemosensory receptor cells allow us to taste our food (sweet, sour, salty, bitter)

• tiny bumps called papillae are also known as your taste buds

Epiglottis• A trap door which

belongs to both the respiratory system and the digestive systems.

• Swallowing triggers its closing over the trachea to prevent food and fluids from draining into our lungs.

Esophagus• A muscular canal running from

the oral cavity to the stomach.

• The tongue pushes a 'bolus' of food into the esophagus to start it on its way to the stomach.

• Peristalsis is the name used to describe the muscle contractions to push food along the tract.

Stomach• Primary function is to break

down bolus using hydrochloric acid, so it can be absorbed by the small intestine.

• The mucous membrane

protects the stomach from the acid.

• The pylorus region is where the contents are emptied into the intestine.

 

Gall Bladder

• Food doesn't touch this organ it is the storage tank, for bile.

• Bile is a greenish-yellow fluid used to help emulsify fats.

• Concentrated bile is released into the small intestine from the common bile duct.

Small Intestine• responsible for continuing to break down

of food into liquid form. • Primary site of nutrient absorption!• nutrients are absorbed through tiny

protrusion in the intestine called villi. • the mostly digested contents start to be

transformed into feces as it is moved along by peristalsis.

Large Intestine

• storage and elimination of waste left-overs

• As the nutritional fluids are absorbed and transferred out to the bloodstream, the contents get more solid and compact.

Rectum• temporary storage for

feces. • receptors from the

nervous system which tell the body to defecate.

The Path of Food – Accessory Organs

Appendix• Little is understood about this

structure that extends from the first section of the large intestine.

• Sometimes a piece of food gets stuck in there, or it gets blocked by stool causing an infection called an appendicitis

Liver• Food doesn't actually pass through

this organ.

• Instead, this organ secretes bile that is passed along to the gall bladder for concentration and storage.

Pancreas• Sugar control board!• If your blood sugar gets too high,

insulin is released• If your sugars are low, glucagon is

released into the blood stream. • Both insulin and glucagon are

produced by the pancreas