RespirationYear 10 Human Biology 2015

Respiratory System

• The respiratory system is made up of various parts and organs:•Nasal Cavity Pharynx•Larynx Trachea•Bronchi Bronchioles•Alveoli Lungs•Diaphragm Intercostals

Respiratory System

The Lungs

• Located in the thoracic cavity• Fills up most of the thoracic cavity• Thoracic cavity consists of:•Rib cage (and intercostal muscles) at the sides•Diaphragm below•Mediastinum is the space between the lungs

The Lungs

The Alveoli - Structure

• Tiny clusters of air sacs making up the lungs

• Thin membraneous walls only 1 cell thick

• Covered by a dense network of capillaries

• Total surface area of approx. 50-80m2

• Make up the bulk of what we know as “the lungs”

The Alveoli - Functions

• These are the functional units of respiration

• Site of gaseous exchange between respiratory and circulatory systems

• Oxygen passes through the thin alveoli walls and into the bloodstream through the thin capillary walls

• Carbon dioxide moves from blood to lungs in the same way

Breathing, Respiration and Gas Exchange

• Breathing is the process of moving air into and out of the lungs

• Respiration takes place at a cellular level whereby cells take in oxygen and excrete carbon dioxide

• Gas exchange takes place in the blood system and is when the blood exchanges oxygen for carbon dioxide via the alveoli (lungs)

The Mechanics of Breathing

• Breathing is also called ventilation• Respiration is not the same as breathing• Air flows from places of higher pressure to

places of lower pressure• Pressure in the lungs constantly varies

Changing Pressure in the Lungs

• To decrease pressure in the lungs we need to increase the volume of the lungs

• If the same amount of air is spread over a larger area then pressure will decrease

• To increase the volume of the lungs the thoracic cavity needs to get larger

Changing Pressure in the Lungs

• The volume of the thoracic cavity can be increased by:

• Contracting the external intercostals and flattening the diaphragm

Inspiration

• The process of taking air into the lungs• It is also called inhalation

• For air to go into the lungs the pressure inside the lungs must be less than the pressure outside the body

Inspiration

Changing Pressure in the Lungs

• To increase pressure in the lungs we need to decrease the volume of the lungs

• If the same amount of air is spread over a smaller area then pressure will increase

• To decrease the volume of the lungs the thoracic cavity needs to get smaller

Expiration

• The movement of air out of the lungs• It is also called exhalation

• For air to go out of the lungs the pressure inside the lungs must be more than the pressure outside the body

Expiration

Changing Pressure in the Lungs

• The volume of the thoracic cavity can be decreased by:

• Contracting the internal intercostals and relaxing the diaphragm so it becomes dome-like

Changing Pressure in the Lungs

Breathing Process

• Normal, quiet inspiration primarily involves the diaphragm changing the thoracic volume

• Heavier inspiration is where the intercostals come into play a bit more

• Normal, quiet expiration is a passive process involving overall muscle relaxation

• Forceful expiration is where the intercostals actively contract to lower the rib cage

Respiratory Volume

• The lungs are measure in terms of the volume of air they can hold.

• Respiratory volumes tell how well a person’s lungs are functioning.

• A spirometer is used to measure respiratory volume.

Respiratory Volume

• TOTAL LUNG CAPACITY

• Total amount of air that the lungs can hold is called the total lung capacity

• Total lung capacity is about 6L for men and 4.4L for women.

Respiratory Volume

• RESIDUAL VOLUME

• Not all the air can be forced out of the lungs no matter how hard you exhale

• The volume of air left in the lungs after maximal expiration is the residual volume

Respiratory Volume

• TIDAL VOLUME

• A certain amount of air enters and leaves the lungs with each breath

• This is known as the tidal volume• HINT: It ebbs and flows just like the tide • It is about 150mL during quiet breathing

Respiratory Volume

• DEAD SPACE

• A certain amount of air does not actually get to the alveoli during breathing

• It remains in the nasal cavity, trachea, bronchi and bronchioles.

• The inside of these organs is called the dead space

Respiratory Volume

• VITAL CAPACITY

• Take in as much air as you can then forced as much out as possible

• The total amount of air that can be forced out of the lungs in this way is called the vital capacity

• It can be measured using a vitalograph

Suggested activities

• Bell jar• Lung Volume prac (Balloons)• Pluck demonstration