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Grade 11 University Biology – Unit 4 Animal Systems
Human Respiratory System
Section 11.1 Pages 442-449
Humans can only survive for a few minutes without oxygen. Unlike water and food, gases cannot be stored easily in
living tissue. Like all mammals, humans must exchange gas with their surroundings on a continual basis. Humans
take in oxygen and release carbon dioxide in a process called RESPIRATION.
One way to measure your fitness is to calculate the maximum amount of oxygen that your body can use when you
perform a very strenuous activity (e.g., running). In theory, you can consume a greater quantity of oxygen in a set
time if your level of fitness is high. VO2MAX is an estimate of the maximum amount of oxygen, in millilitres, that a
person can use in one minute per kilogram of weight while breathing air at sea level. VO2MAX over 35 mL/kg/min is
considered good for females ages 13-19, while a VO2MAX over 45 mL/kg/min is good for males ages 13-19.
VO2MAX Formula
VO2MAX = (Speed X 0.172) / 10.4
Example
You run a distance of 400 m in 90 seconds. What is your VO2MAX?
Speed = 400 m / 90 s
= 400 m / 1.33 min
VO2MAX = (301 X 0.172) / 10.4
= 62.2 mL/kg/min
= 301 m/min
Humans are large, warm-blooded mammals called ENDOTHERMS. Endotherms have a very high oxygen demand.
This demand is met by the structures of the Human Respiratory System.
Air usually enters the respiratory system through the NOSTRILS. Dust and other unwanted particles are trapped by
tiny hairs and a layer of mucus that line these passages. The incoming air is also warmed and moistened in this
region.
At the back of the throat, air passes through the TRACHEA or windpipe to the lungs. A flap-like structure called the
EPIGLOTTIS is located at the top of the trachea to prevent food from entering the lungs during food swallowing.
Inhaled air moves through the trachea into two BRONCHI, and then, into a network of smaller tubes called
BRONCHIOLES.
The inner linings of the trachea, bronchi and bronchioles are covered with CILIA and contain mucus-producing
GOBLET CELLS. The mucus traps particles such as dust, bacteria and pollen that are carried out of the lungs by the
sweeping action of the cilia.
In the lungs, the bronchioles become smaller and smaller until they reach tiny air sacs called ALVEOLI. In the alveoli,
gas exchange occurs between the air and blood. Each lung has about 150 million alveoli. The total surface area of
all the alveoli is about 80 m2 – about 40X the surface area of your skin.
CAPILLARIES surround each cluster of alveoli. Blood entering the network has a low oxygen concentration and a
high carbon dioxide concentration. This blood passes through the capillary network where oxygen gas DIFFUSES
from the air space within the alveoli, through the single-celled walls of the alveoli and capillaries into the blood.
Carbon dioxide moves in the opposite direction. Thus, blood leaving the capillary network is high in oxygen and low in
carbon dioxide.
There are two stages of breathing:

INSPIRATION (inhaling) where air is moved into the lungs, and

EXPIRATION (exhaling) where air if forced out of the lungs.
Air will always move from an area of HIGH PRESSURE to an area of LOW PRESSURE. If air pressure in the lungs
is less than the air pressure outside, air moves into the lungs. During inspiration, the DIAPHRAGM contracts and
moves downward while the RIB CAGE expands upward and outward by the action of EXTERNAL INTERCOASTAL
MUSCLES. The increase in volume of the chest cavity lowers the air pressure in the lungs allowing air to move
inward.
The LUNGS are the major organ of the respiratory system.
Lungs are filled with air spaces. They are designed so large amounts of the membrane that lines the
lungs are exposed to the air we inhale. The lungs have a total surface area about 40X greater than the
total surface area of our skin.
The respiratory passages are lined with MUCOUS MEMBRANES that warm and moisten the air, and at
the same time, filter out dust, pollen and bacteria. The moist surface aids in the diffusion of oxygen
through the cell membranes and into the blood system.
To increase surface area, the lungs have air sacs called ALVEOLI. Adult humans have 300 million alveoli
with a total surface area about the size of half a tennis court.
The TOTAL LUNG VOLUME is about 6 litres. Yet, we can only exhale 5 litres. This is called VITAL
CAPACITY. The one litre of air remaining in the lungs is called the RESIDUAL VOLUME
Task

Complete the following definitions
Term
Definition
Tidal Volume
Inspiratory Reserve Volume
Expiratory Reserve Volume
Vital Capacity
Residual Volume
Diffusion Gradient
Respiration
Inspiration
Expiration
Gas Exchange
Ventilation

Make a chart in your notes summarizing the four types of respiratory surfaces in animals (Page 444, Table
11.1)
Homework
Page 444, Questions 1-6
Page 449, Questions 1, 3-4, 6-12
Grade 11 University Biology – Unit 4 Animal Systems
Respiratory System – Lungs
Adapted from: National Geographic. 1997. Human Body 1
TRC 612 H87 KIT
What do you know about...
 The organs that make up the RESPIRATORY SYSTEM?
 How oxygen reaches our blood?
TASK
You will
 Determine the vital air capacity of your lungs
Materials
 3.5 L plastic water bottle
 0.5 m of plastic tubing per student
 Sink or large, deep pan
 500 mL graduated beaker
 Permanent marker
 Water
NOTE: If you have asthma or other breathing problems, you may not wish to participate.
Methods
 Using the graduated beaker, measure 200 mL of water
 Add water to the plastic water bottle marking the level of 200 ml on the outside of the bottle using
the marker
 Repeat these steps to add another 200 ml of water
 Repeat until the bottle is completely full of water
 Fill the sink or pan with water until it is ½ full
 Cap the mouth of the plastic bottle
 Turn the plastic bottle upside down and carefully place it into the sink / pan so that the bottle
opening is under water. When you uncover the bottle opening, no air should enter the bottle
 Slip one end of the tubing into the opening of the bottle. DO NOT raise the opening of the bottle
above the surface of the water. You may need to hold the bottle to ensure the tubing stays in the
bottle and the bottle does not tip
 Fill your lungs to capacity (...as much air as possible)
 Place the other end of the tubing in your mouth
 Hold your nose closed with one of your hands
 Blow out all the air you can from your lungs into the tubing. This air should displace the water in
the plastic bottle
 Measure the volume of air expelled by reading the 200 mL graduations on the side of the bottle
 Record the volume in Data Table 1
 Refill the bottle and repeat the full experiment 2X recording the air volume each time
 Calculate the average Vital Capacity of your lungs
Data Table 1. Lung Capacity Data Chart
Trial Number
Your Vital Capacity (mL)
Your Partner’s Vital
Capacity (mL)
Class Average Vital
Capacity (mL)
1
2
3
Average
Questions
1. What did you learn about Vital Capacity from the experiment?
2. Offer TWO reasons why a person might have a smaller than average Vital Capacity.