Grade 9 Lesson1

Living Things
and Their
Environment
Look around. Everything you see and
feel is a part of your environment. An
environment includes living things such
as plants, animals, people, and even the
tiniest of microbes.
The living portions of the environment
are called the biotic parts. The nonliving
portions, such as rocks, sunlight, and air,
are called the abiotic parts.
How do biotic parts
differ from abiotic
parts?
There are seven activities which make
organisms different from
non-living things.
Nutrition
Movement
Excretion
Growth
Reproduction
Sensitivity
Respiration
Take a breath in and hold it .
Wait several seconds and then
let it out.
Breathing is an involuntary event. How
often a breath is taken and how much air
is inhaled or exhaled are tightly
regulated by the respiratory center in the
brain.
Respiratory
System
The primary function of the respiratory system is to
deliver oxygen to the cells of the body’s tissues and
remove carbon dioxide, a cell waste product. The main
structures of the human respiratory system are the nasal
cavity, the trachea, and the lungs.
The Nose
The Nose
It is the external
protuberance of an internal
space, the nasal cavity.
The Pharynx
The Pharynx
The Pharynx can be divided into three
floors. The upper floor (nasopharynx) is
primarily a passageway for air and
secretions from the nose to the oral
pharynx.
The Pharynx
The middle floor of the pharynx connects
anteriorly to the mouth and is therefore
called the oral pharynx. It is delimited from
the nasopharynx by the soft palate, which
roofs the posterior part of the oral cavity.
The Pharynx
The lower floor of the pharynx is called the
hypopharynx. Its anterior wall is formed by
the posterior part of the tongue.
The Larynx
The Larynx
It is an organ of complex structure that
serves a dual function: as an air canal to the
lungs and a controller of its access, and as
the organ of phonation.
The Trachea
The Trachea
Below the larynx lies the trachea, a tube
about 10 to 12 cm long and 2 cm wide. Its
wall is stiffened by 16 to 20 characteristic
horseshoe-shaped, incomplete cartilage
rings that open toward the back and are
embedded in a dense connective tissue.
The Bronchi
The Bronchi
At its lower end, trachea divides in an
inverted Y into the two stem Bronchi, one
each for the left and right lung. The right
main bronchus has a larger diameter, is
oriented more vertically, and is shorter that
the left main bronchus.
The Bronchioles
The Bronchioles
In your lungs, the main airways(bronchi)
branch off into smaller and smaller
passageway – the smallest, called
Bronchioles, lead to tiny air sacs(alveoli).
The Alveoli
The Alveoli
The alveoli are where the lungs and the
blood exchange oxygen and carbon dioxide
during the process of breathing in and
breathing out. Oxygen breathed in from the
air passes through the alveoli and into the
blood and travels to the tissues throughout
the body.
The Lungs
The Lungs
The Lungs main role is to bring in air from
the atmosphere and pass oxygen into the
bloodstream.
The Diaphragm
The Diaphragm
The Diaphragm is a muscle that is domed
at the top and sits below the lungs. It
powers most of the work involved in
breathing.
We breathe a lot—roughly 15 times per minute on average.
Have you ever wondered how the process of breathing works
so smoothly?
Our lungs allow us to inhale the oxygen our body needs, but
they do much, much more. They also allow us to get rid of
carbon dioxide, the waste product created in the body, and
they play a vital role in singing, shouting and even giggling. In
this activity you will make a model of a lung and use it to
discover how air flows in and out of the lungs with ease
During inhalation, the diaphragm
descends creating a negative pressure
around the lungs and they begin to
inflate, drawing air from outside the
body.
The air enters the body through the
nasal cavity located just inside the nose.
As the air passes through the nasal
cavity, the air is warmed to body
temperature and humified by moisture
from the mucous membranes.
These processes help equilibrate the air
to the body conditions, reducing any
damage that cold, dry air can cause.
Particulate matter that is floating in the
air is removed in the nasal passages by
hairs, mucus, and cilia.
From the nasal cavity, air passes through
the pharynx (throat) and the larynx
(voice box) as it makes its way to the
trachea.
The trachea is lined with cells that have
cilia and secrete mucus. The mucus
catches particles that have been inhaled,
and the cilia move the particles toward
the pharynx.
Air enters the lungs through the primary
bronchi. The primary bronchus divides,
creating smaller and smaller diameter
bronchi called bronchioles.
The final bronchioles are the respiratory
bronchioles. Alveolar ducts are attached
to the end of each respiratory bronchiole.
At the end of each duct are alveolar sacs,
each containing 20 to 30 alveoli. Gas
exchange occurs only in the alveoli.
The medulla oblongata is the primary
respiratory control center. Its main
function is to send signals to the muscles
that control respiration to cause
breathing to occur.
There are two regions in the medulla
that control respiration:
• the Ventral respiratory group
• The Dorsal respiratory group
The pons is the other respiratory center
and is located underneath the medulla.
Its main function is to control the rate or
speed of involuntary respiration.
Gas Exchange
Is the delivery of oxygen from the lungs to
the bloodstream, and the elimination of
carbon dioxide from the bloodstream to the
lungs.
Gas Exchange
It occurs in the lungs between the alveoli
and a network of tiny blood vessels called
capillaries, which are located in the walls
of the alveoli.
Common Disorders of
Respiratory System
Most people take effortless breathing for
granted. When your lungs are healthy, they
expand easily into your chest cavity as you
inhale, taking in vital oxygen for your blood
to deliver throughout your body.
With each exhalation, your lungs deflate
and release carbon dioxide, a respiratory
waste product.
When you run to catch the bus or climb a
steep flight of stairs, your breathing
naturally adapts to meet the extra demand
on your heart and lungs.
Shortness of breath, also called dyspnea – a
feeling of extreme tightness in the chest,
difficulty breathing and what’s sometimes
referred to as “air hunger” – is a hallmark of
respiratory of disease.
Respiratory Diseases or Lung Diseases are
pathological conditions affecting the organs
and tissues that make gas exchange difficult
in air-breathing animals.

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Living Things

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