Chapter 12, part 1

Cardio-Respiratory System

Functions of the Respiratory System

• Bring air from the atmosphere to the lungs

• Transfers oxygen into the blood

• Removes carbon dioxide from the blood

• Expels heat and water vapour in the air breathed out

• Allows the vocal cords to create speech as air is breathed out

Respiratory Anatomy

• The major organ is the lung• Air from the atmosphere enters the body through

the mouth/nose, then passes through the pharynx and larynx (voice box) before entering the trachea (windpipe). This divides into 2 bronchi (one to each lung) and they further subdivide into bronchioles. These empty the air into the alveoli (air sacs) where gas exchange with the blood occurs.

The lungs

Nasal cavity

Trachea

BronchusAlveoliBronchioles

Lungs

Diaphragm

Left Lung - Bronchiole - Alveolus

Mechanics of Breathing

• Breathing in is technically called inspiration while breathing out is called expiration

• Breathing is caused by changing the size of the chest cavity

• It takes effort to enlarge the chest cavity. The diaphragm contracts (pulling downward) and the intercostal (between the ribs) muscles help pull the ribcage outward.

Mechanics of Breathing Cont.

• With the chest cavity enlarged the air pressure inside the lungs decrease and causes air to be sucked in.

• Breathing out happens when the diaphragm and intercostal muscles relax. The chest cavity gets smaller increasing the air pressure and forcing air out of the lungs.

Intercostal Muscles Diagram

External Intercostal

Muscles

Internal Intercostal

Muscles

Diaphragm

Lung Volumes

• Each minute a person breathes, they move approximately 9 Litres of air in and out of their lungs.

• The amount of air a person can inhale and hold or exhale varies according to: body size, state of health and activity level.

Vital capacity readingsfor adolescent male and

female students

Boys (litres) Girls (litres)

Ranking 12 years 15 years 12 years 15 years

Top 10% 3.65 5.5 3.6 4.25

Mid-range

3.0 4.5 2.9 3.6

Lowest 2.15 3.15 2.05 2.6

Definitions

• Respiration rate – number of breaths per minute• Tidal volume – the amount of air breathed in and

out normally• Minute ventilation – the amount breathed in and

out in one minute (ventilation = tidal volume x respiratory rate

• Vital Capacity – the maximum amount of air you can breathe out after breathing in

• Oxygen uptake (VO2) – the amount of oxygen used by the body in one minute

• Maximal oxygen uptake (VO2max) – the maximum amount of oxygen your body can use in one minute. This is the best indicator of how aerobically fit someone is

• Residual volume – the amount left in the lungs after breathing out all you can

• Inspiratory reserve capacity – the amount you can breathe in after a normal breathe in

• Expiratory reserve capacity – the amount you can breathe out after a normal breathe out

What Happens During Exercise?- Breathing rate (or respiration) increases

- under normal conditions, adult respiration rate is about 12 breaths/min.– under high intensity exercise conditions, this can reach 35–40 breaths/min.

- Tidal volume (TV) increases– at rest this is around 0.5 L/min.– under high intensity exercise conditions, this can reach around 4–5 L/min.

- Ventilation increases- at rest this is approximately 7.5 L/min- under high intensity exercise conditions, this can reach around 150 L/min

- Vital capacity (VC) remains the same– this lung volume remains the same during one acute exercise session.– it can be reduced by asthma and other respiratory problems such as the common cold, bronchitis or emphysema.

- Oxygen uptake increases– at rest the average amount of oxygen that an individual can take into the body is about 3-4 mL/kg/min.– under sub-maximal exercise conditions this can increase to around 30–50 mL/kg/min.

Complete Checkpoint Questions 1-4 on page 288