The Human Respiratory System

l Breathing is the process by which oxygen in the air is brought into the lungs and into close contact with the blood, which absorbs it and carries it to all parts of the body. At the same time the blood gives up waste matter (carbon dioxide), which is carried out of the lungs with the air breathed out.

l This process, called cellular respiration, takes place in the mitochondria

l We breathe 12 to 15 times a minute, allowing

oxygen to enter, and carbon dioxide to exit our bodies.

Respiratory System Parts

The air we breathe The air we inhale is :

– Nitrogen (N2) 78%

– Oxygen (O2) 21%

– Carbon Dioxide (CO2) 0.04%

– Other gases < 1%

The air we exhale is:

– Nitrogen (N2) 78%

– Oxygen (O2) 16%

– Carbon Dioxide (CO2) 5%

– Other gases <1%

Nasal & Oral Cavity

The Nasal Cavities •  The nasal cavities have 3

functions: o  Filtering- Microscopic hairs

called cilia cover the surface and trap dirt.

o  Warming- ridges in cavity called turbinates increase surface area and contact with capillaries full of blood to warm air.

o Humidify- mucus secreted by glands adds moisture to the air

sinus sinus

Hard palette Soft palette uvula Opening to ear

vestibule

The Pharynx •  Used by both the digestive and

respiratory system for the passage of air or food.

•  Found at back of the mouth and connects with nasal cavity.

•  The PHARYNX (throat) collects incoming air from the nose and passes it downward to the trachea (windpipe).

Larynx (voice box)

•  Made mainly of cartilage

•  Joins the trachea to the pharynx

•  The epiglottis closes when food is swallowing blocking the the airway.

•  The larynx contains the vocal cords that vibrate when air is forced through

Trachea •  The trachea connects the

larynx to the bronchi •  It is in front of the esophagus. •  It has cartilage rings that

keep it rigid and keep it from collapsing.

larynx

bronchus

trachea

Lungs

Collapsed esophagus

trachea

Cartilage rings

Cilia in the Trachea

• Cilia are hair-like projections that line the trachea

• They help to sweep dirt and mucus out of the lungs

The lungs l  There are 2 lungs

which are not identical.

l The right one has 3 lobes

l The left one has 2

lobes

bronchioles

bronchi

trachea •  The trachea splits up into two bronchi tubes.

•  The bronchi tubes split

up, like tree branches, and get smaller and smaller inside the lungs to form the bronchiole.

Bronchi Tubes and Bronchiole

Bronchi Tubes and Bronchiole •  The bronchiole keep getting smaller and smaller

until they finally end with small air sacs called alveoli.

Alveoli l The alveoli fill up with air/oxygen when you

breath in. l The alveoli are surrounded by many tiny blood

vessels called capillaries. l The walls of your alveoli (and capillaries) are so

thin that the oxygen or carbon dioxide can pass through them, traveling right into, or out of your blood stream.

Diaphragm l The diaphragm is a sheet of muscle

extending across the bottom of the rib cage

l When it contracts in lowers into the abdomen, it

lowers the pressure in the lungs to suck in air l When it relaxes, it rises back up under the ribs

and the air is forced out of the lungs (also due to a change in pressure)

The Respiratory system Ribs & sternum Rises when intercostal muscles contract

Diaphragm Contracts and lowers

Volume of thoracic cavity and lungs

Volume increases

Air pressure in lungs Pressure decreases

Displacement of air Air enters system

Ribs & sternum Raises when intercostal muscles relax

Diaphragm Relaxes and rises

Volume of thoracic cavity and lungs

Volume decreases

Air pressure in lungs Pressure increases

Displacement of air Air exits system

Inhaling

Exhaling

The mechanics of inhaling and exhaling

Gas Exchange- Inhale

l While inhaling, the alveoli are filled with air. l As the lungs are higher in oxygen concentration

than in the blood, the oxygen diffuses (a movement of particles) through the alveolar membrane into the blood and attaches to the red blood cells (RBC’s).

Gas Exchange- Exhale

l When the blood has a higher carbon dioxide concentration than the lungs, the carbon dioxide diffuses through the alveolar membrane into the lungs where it is excreted (process of eliminating waste) as we exhale.

Respiratory System Conditions

1) Bronchitis:

l an inflammation of the membranes of the bronchial tubes

2) Asthma: l  an allergic response

characterized by the constriction (narrowing) of the bronchial tubes

l  can be caused by many different factors

l  medications and inhalers are used to open up the respiratory passages

3) Emphysema: l  a general deterioration

of the lungs l  alveoli are enlarged

and stiff (and can't function) which reduce the lung capacity for air

4) Pneumonia: l  a condition where the alveoli become

filled with fluid, preventing the normal exchange of gases

Fun Facts

l Carbon dioxide does not burn or support combustion.

l Because of this property, it is used in some fire extinguishers.