Digestive System

" This is the crappiest lecture I have ever given "

Body cavity (coelom) - Where your internal organs go.

          Thoracic cavity - Contains heart and lungs.

          Diaphragm - A sheet of muscle that separates the 2 cavities and aids in breathing.

          Abdominal cavity - Contains most of the remaining organs, most of which makes up the digestive system.

* Ingestion - Eating food

* Digestion - breaking down food into its basic parts (monomers).

* Absorption - Transporting digested materials from the digestive tract over to the circulatory system then to all the cells of the body.

* Elimination - Getting rid of undigested material.

Mouth - The teeth break food down into smaller bits. pH = 7

          Salivary glands - (Accessory Organ) Produce saliva which helps moisten the food. Also contains an enzyme which starts to break down starch into simple sugars.

Uvula - Hangy downy thing that covers the entrance to the nasal cavity.

Pharynx - Where the respiratory and digestive tracts split.

Epiglottis - Covers the opening to the trachea when food is swallowed.

Esophagus - Connects the pharynx to the stomach.

          Peristalsis - Rhythmic contractions that push food through the digestive tract.

Cardiac Sphincter - A round muscle to separate the esophagus from the stomach. Opening to the stomach.

Stomach - A storage pouch. Holds about a quart(1 liter). Undergoes peristalsis

          Gastric pits - Are pits in the wall of the stomach. Secrete 3 things.

                    Mucus - Which protects the wall of the stomach

                    Hydrochloric acid   HCL - Makes the stomach a pH of 2. Also activates pepsin

                    Pepsin - Once activated by HCL starts protein breakdown.

Pyloric sphincter - A round muscle to separate the stomach from the small intestine. Opening at the bottom of the stomach.

Chyme - Food that has been churned by the stomach from 30 minutes to 6 hours.

Small intestine - This is where most digestion and absorption occurs and is about 20 feet long (9 feet in a living person). pH = 8

Pancreas - (Accessory Organ) Dumps digestive enzymes and sodium bicarbonate (pH = 8) into the small intestine to finish digestion of the different foods.

          Sodium bicarbonate - Makes the stomach basic - 8

Liver - (Accessory Organ) Produces bile (about 1.5 liters a day)

          Bile - Emulsifies fat

                    Emulsifier - Breaks up or disperses big fat globs into smaller droplets of fat.

          Gall bladder - (Accessory Organ) Bile is stored here

          Glycogen - How the liver stores excess sugar.

Villi and Microvilli - Folds and smaller folds that increase the surface area of the small intestine about 600x (about the size of a tennis court).

Large Intestine (Colon) - Reabsorbs water and salt and makes feces. Bacteria in the large intestine provide us with vitamin K.

          Appendix - Used to digest cellulose.

          Feces - Undigested waste to be eliminated.

Anus - Has 2 sphincters - the internal one is involuntary and the external one is voluntary.

RDA-Recommended dietary allowance - Average daily level of nutrient intake sufficient to meet the nutrient requirements of nearly all healthy people.

Food groups - Similar types of foods/nutrients

BMR - Basal metabolic rate - The number of calories we burn while resting.

Obesity - Being more than 20% heavier than the average person of the same sex and height.

          BMI - Body Mass Index - 25 = Overweight; 30 or more = Obese.


Vertebrates have a: Mouth --> Pharynx --> Esophagus --> Stomach --> Small Intestine --> Large Intestine --> Anus.


Diet:                      Typical         Recommended

Protein                    16 %                 12 %

Carbohydrates         46 %                 58 %

Fats                        38 %                 30 %


RDA for Protein:

Men (154 lbs) = 56 g

Females (120 lbs) = 44 g


1 slice of roast beef = 25 g

1 glass of milk = 8 g


BMR: Males = 1,600 - 1,800 kcal / day

Females = 1,300 - 1,500 kcal / day









































Return to Greg Sievert's GB 100 Syllabus
Last updated on 7 January 2018