1. 3.2 – Human Organs & Systems
Circulatory, Digestive, Respiratory, Nervous, Skeletal, Muscular, Immune, Endocrine, Reproductive, Urinary, Integumentary

2. Main Function of Each System
1. Circulatory System  transports blood, nutrients, gases & wastes
2. Respiratory System  controls breathing and exchanges gases in the lungs
3. Digestive System  takes in food, breaks it down, absorbs nutrients and removes waste
4. Urinary System  removes liquid wastes
5. Nervous System  detects changes in the environment and sends signals to parts of the
body to respond
6. Skeletal System  supports, protects, & works with muscles to move parts of the body
7. Muscular System  works with bones to move parts of the body
8. Immune System  defends against infection
9. Endocrine System  makes & releases hormones to keep systems working properly
10. Reproductive System  produces offspring
11. Integumentary System  creates a waterproof barrier around body (skin, hair, nails)

3. Circulatory System Picks up and transports oxygen & nutrients to cells
See Figure 3.20A on p. 100
Picks up and transports oxygen & nutrients to cells
Carries wastes to kidneys for elimination from the body
Heart contractions produce pressure so that blood can move around the body
Heart valves close after blood is pushed through them to prevent blood from flowing backwards
Arteries carry oxygenated blood
Veins carry deoxygenated blood and wastes like CO2 that need to be removed from body
remember the exception! (explained in the video)
artery = away from heart
vein = towards heart

5. Remember…
Blood flows through the 4 chambers of the heart & through the lungs before being dispersed through the body

6. Blood in the Heart & Lungs
Blood returning from the body is deoxygenated
carries CO2 waste from cellular respiration
Blood returning from the lungs is oxygenated
bright red due to the high O2 content
See Figure 3.20B on p. 100

7. The Path of Blood in the Body
Blood from body:
Vena cava 
Right atrium 
Right ventricle 
Pulmonary arteries 
Lungs 
Pulmonary veins 
Left atrium 
Left ventricle 
Aorta 
Blood circulates to body

9. Capillaries
KAP-ill-air-eez
These are networks of very thin blood vessels (1 epithelial cell thick!)
They deliver oxygen & nutrients and pick up waste materials from tissues in every organ in the body
Trace the path of blood with your finger, starting at one point and returning to it

11. Quiz time! Name the 2 major functions of the circulatory system.
Name the 4 main chambers of the heart.
What do the valves in the heart do?
With a partner, explain the path that blood takes through the body from your fingertip or your toe, back to that same body part.
What are capillaries? What do they do?

12. The Same, but Different
Read the top half of p Then with a partner, answer the following questions.
1. a) What is the difference between an open and closed
system with regards to circulation?
b) Give an example of an animal that would have an
open system, and one that would have a closed one.
2. How is a fish’s heart different from a human’s?
3. a) How many chambers does an amphibian’s heart
have?
b) What does this mean then?

13. Respiratory System Consists of the lungs & airways
Responsible for gas exchange (O2 in, CO2 out)
Is connected to the circulatory system so that it can exchange gases in the blood (through capillaries)
The diaphragm is a muscle that contracts when you breathe
allows room for your lungs to expand so they can take in air
rib cage moves up & out, causing air to be pulled into your body through your nose or mouth

15. Use Your Nose!
The air your breathe in passes by epithelial cells in your nasal cavity
cells have tiny, hair-like projections called cilia
they also secrete mucus
Both cilia & mucus keep foreign particles like allergens, bacteria, and toxins out of your body

16. Pharynx  Trachea  Bronchi
Air moves from the pharynx (throat) to your trachea
a small flap called the epiglottis opens and closes so no food ends up in the trachea
From the trachea, the single pipe splits into two, called bronchi
each bronchi goes to a lung

17. Bronchi  Bronchioles  Alveoli
Bronchi then branch out into smaller tubes called bronchioles
bronchioles are embedded within the lung tissue
Bronchioles divide into tiny sacs called alveoli
Capillaries surround the alveoli
it is here that gas exchange takes place
See Figure 3.26 on p. 104

18. Alveoli Tiny clusters of air sacs in the lung (sing. = alveolus)
have a very thin epithelial layer
gases can cross, but bacteria and other harmful substances cannot
O2 and CO2 are exchanged with blood in the capillaries
O2 to RBC from alveoli
CO2 to alveoli from RBC
RBCs contain hemoglobin, which binds O2 so that it can be carried through the body

19. Alveoli are the tiny heroes of the respiratory system!

20. Alveoli       Mouth
When your diaphragm & chest muscles relax, you exhale
CO2 in the alveoli is released into the air in the opposite way O2 came in
When CO2 levels get too high, breathing rate increases so CO2 can be expelled quicker

21. The Same, but Different… again
Birds, reptiles, & amphibians have lungs just like humans do
these creatures have an effective gas exchange system, but it is different than ours
Instead of alveoli, fish have gills
Read over Figure 3.28 on p and summarize with a classmate how gills perform gas exchange just like alveoli in humans

22. Quiz… yahoo!!
Trace the path of a breath of air in through your nose and out through your mouth.
Why should you always breathe in through your nose?
What is the structure in the lung where gas exchange takes place? Name 2 gases that are exchanged with blood in capillaries here.
Why does your breathing rate increase when you’re exercising?

23. Systems Interactions
How are the circulatory & respiratory systems related?
Name the structures in each system that work together so humans can get the nutrients they need to their cells to survive. Think small.
If you had to have one system but not the other, which of the 2 we studied today could you live without?