Lecture 2 - 3: The Digestive System

What is digestion?

Process of breaking down large food molecules to smaller ones to be absorbed into the blood stream

What is the function of the mouth?

Mechanical breakdown of food: begins chemical digestion of carbohydrates

What is the function of the stomach?

Mechanical digestion: muscle of stomach walls churn food

Chemical digestion: pepsin breaks down protein

What is the function of the esophagus?

Connects mouth to stomach and peristalsis moves food down tube

What is the function of the small intestine?

• absorbs nutrients into the blood stream

• Substances are absorbed due to the presence of villi, glucose, amino acids and vitaminS

What is the function of the colon?

Absorption of water and makes vitamins (large intestines)

What is the function of the anus?

Wastes exit the body

What are some of the roles of the liver?

• Stores glucose as glycogen

• Detoxifies certain poisons

• Controls amount of organic substances in the blood

• Produces bile

• Emulsifies fat

What is the function of the pancreas’s ?

• secretes enzymes and sodium bicarbonate

• Lowers the acidity of food leaving the stomach to ph8

• Produces insulin

What is the function of the gall bladder?

Stores blue from the liver

Describe the variety of teeth a herbivore has

Incisors: sharp

Molars and pre-molars: flattened to grind

Diastema: gap between incisors and teeth

Describe the variety of teeth a carnivore has

Canines: long sharp and curved

Incisors: short and pointed

Molars and pre-molars: sharp, blade shaped

Compare the diets and alimentary canals of herbivores and carnivore’s

Herbivores

• eat plants: eat cellulose so they have a lingering digestive tract in order to digest

• Much longer caecum

Carnivores

• similar digestive tract

• Shorter caecum and digestive tract

What are the 4 stages of food processing?

1. Ingestion - takes food in

2. Digestion - breaking into small pieces

3. Absorption - digested food moves into blood

4. Assimilation - digested food being incorporated or used by cells

5. Elimination - removal of undigested food

Where are carbohydrates digested?

Start in mouth, but primarily in small intestine

What are the different types of digestion?

Mechanical: physical breakdown of food. Teeth (grinding) Stomach muscles (churning and contracting)

Chemical: enzymes breakdown polymers to monomers (saliva and stomach acid)

What enzymes breaks down proteins and into what?

Proteases → amino acids

What enzymes breaks down large carbohydrates and into what?

amylases - monosaccharides, disaccharides, glucose

What enzymes break down lipids and into what?

Lipases → fatty acids and glycerol

What enzymes breaks down nucleic acids and into what?

Nucleoases → nucleotides

What is the alimentary canal?

Digestive track from the mouth to the anus

How does food travel through the alimentary canal?

Peristalsis

What is paristalsis?

Muscles contracting and relaxing moving food along the digestive system

What is the Epiglottis?

A cartilage covered with mucus to stop food from entering the trachea when swallowing

What is the enzyme found in the stomach?

Pepsin

Non digested fat particles and digested fats pass into this structure ___

Lacteal of villi in the small intestine

The type of blood vessel that is closely associated with villi

Capillary

The first part of the small intestine

Duodenum

The last part in the small intestine

ileum

How does the structure of the villi of the small intestine help it absorb digested food effectively?

It has folds that increase the surface area and are very thin, so diffusion occurs quickly

The are associated with capillaries and lacteals so the digested molecules can be absorbed into the blood stream quickly