1. Level Part 1 Body Systems Chapters 37-43

2. A. Levels of Organization
The human body is organized in several levels, from the simplest to the most complex:
(1) Cells – the basic unit of life
(2) Tissues – clusters of cells performing a similar function
(3) Organs – made of tissues that perform one specific function
(4) Organ Systems – groups of organs that perform a specific purpose in the human body
The purpose of the 11 organ systems is for the human body to maintain homeostasis.

3. B. The 11 Human Body Systems
The 11 human body systems are as follows:
1. Nervous system
2. Respiratory system
3. Excretory system
4. Muscular system
5. Endocrine system
6. Lymphatic (immune) system
7. Integumentary system
8. Digestive system
9. Skeletal system
10. Circulatory system
11. Reproductive system

4. B. The 11 Human Body Systems
A. Cells within each of the 11 body systems:
1. Have the exact same DNA
2. Somatic cells have 46 chromosomes
3. Different genes are expressed so cells have different structure and function
i. Example: Blood, and muscle cells, all have the same DNA, but have different structure, function and purpose.
4. Gamete (sex) cell have 23 chromosomes

5. B. The 11 Human Body Systems
1. Systems that interact to perform regulation
a. Endocrine system
b. Excretory system
c. Integumentary system
2. Systems that interact to perform nutrient absorption
a. Digestive system
3. Systems that interact to perform reproduction
a. Reproductive system
c. Circulatory system
4. Systems that interact defend from injury or illness
a. Respiratory system
b. Nervous system
c. Muscular system
d. Nervous system
e. Circulatory system
f. Respiratory system
b. Circulatory system
b. Endocrine system
d. Skeletal system
e. Integumentary system
f. Immune system
g. Endocrine system

6. C. The Digestive System I. Overview
1. Purpose: To convert food particles into simpler molecules that can be absorbed into the bloodstream and used by the body
2. Digestive system process:
II. Major Organs and their Functions:
1. Mouth:
a. Chew and grind up food.
b. Saliva also begins the chemical breakdown.
2. Pharynx: passage from the mouth to the larynx and esophagus
3. Esophagus: pipe connecting mouth to stomach.

7. C. The Digestive System
4. Stomach:
a. Secretes acid that breakdowns of food.
b. Once the food is broken down and mixed with digestive juices, it is called chyme.
5. Pancreas: Produces the hormone insulin that regulates blood sugar levels.
6. Liver: produces bile, which breaks down fats in foods
7. Gallbladder: pouch-like organ that stores bile for future use
8. Small Intestine:
a. After digestion, the chyme enters the small intestine through villi (folded surfaces), where it is absorbed into the bloodstream.
9. Large Intestine: removes water from the chyme and gets the waste (feces) ready for excretion

8. C. The Digestive System
9. Large Intestine: Home to a vast population of bacteria.  
A. Beneficial bacteria in the gut:
1. Break down undigested food
2. Neutralize harmful by-products of food breakdown.
3. Aid the absorption of nutrients
4. Produce certain vitamins such as Vitamin K, needed for blood clotting.

9. C. The Digestive System

10. D. The Excretory System 1. Kidneys :
I. Overview
Purpose: to rid the body of wastes, including excess water and salts
Renal system: ( 5 minutes)
II. Major Organs and Their Functions
1. Kidneys :
a. Waste-laden blood enters the kidney and the kidney filters waste products; waste products travel out of the kidney as urine.
b. Eventually they travel through the ureter to the urinary bladder.
2. Rectum: solid (food) waste travels out of the body through the rectum.
3. Skin: sweat glands remove excess water and salts from the body.
4. Lungs: expel the waste gas carbon dioxide.

11. D. The Excretory System The Renal System