I. RESPIRATION is the process of exchanging gasses between the atmosphere and the body.

II. Respiratory organs

A. Nose and nasal cavity (the hollow space behind the nose)

A. Moving air in and out of the lungs - Breathing / VENTILATION

B. Exchanging gasses between the lungs and blood - EXTERNAL RESPIRATION

C. Exchanging gasses between the blood and body cells - INTERNAL RESPIRATION

D. Using O2 and making CO2 (waste) - Cellular respiration

1. The SEPTUM divides the nasal cavity into right and left portions.

B. Sinuses are air filled spaces that are continuous with the nasal cavity. They are filled with mucous membranes.

2. Pseudostratified epithelium (with mucous secreting goblet cells) lines the cavity.

a. Mucous traps dust, bacteria and other particles.

b. Cilia move trapped particles along to be swallowed where they can be killed by stomach acid.

3. Air is warmed as it passes over blood vessels in mucous membranes.

C. The PHARYNX is inferior to the nasal cavity. It is a passageway for food moving to the esophagus and air moving to the lungs. IT helps to produce sounds.

D. The LARYNX is inferior to the pharynx and superior to the trachea.

1. It is made of muscles and cartilage.

2. The EPIGLOTTIS is a flap-like structure that prevents food from entering the trachea.

3. The vocal cords are in the larynx. Sound is made from air being forced between folds causing them to vibrate.

E. The TRACHEA (windpipe) extends into the thoracic cavity and splits into the left and right BRONCHI.

1. It is lined with mucous membranes that trap particles and send them to the pharynx to be swallowed.

2. 20 c-shaped pieces of hyaline cartilage line the trachea to prevent it from collapsing.

3. Muscle tissue between the cartilage gives the trachea elasticity.

F. The BRONCHIAL TREE is made up of the branching airways that lead from the trachea to the microscopic air sacs in the lungs.

G. The LUNGS are spongy organs located in the thoracic cavity. They are enclosed by the diaphragm.

1. PLEURAL MEMBRANES line the lungs.

1. It branches with the right and left primary bronchi, and after much more branching eventually ends in the alveolar ducts, sacs, and alveoli.

2. The alveoli have very thin walls so that gasses can diffuse in and out of them.

2. The space between the plural membranes and the other body organs is called the PLEURAL CAVITY. It is lined with mucous membranes that lubricate the lungs to reduce friction from breathing.

III. Mechanisms for breathing

A. INSPIRATION (inhalation) occurs because of air pressure differences between the environment and the lungs.

Pressure Volume Pressure Volume

1. Air pressure and volume are inversely related.

2. During an inhale, the diaphragm and INTERCOSTAL MUSCLES ( between ribs) contract and expand the chest cavity, lowering the pressure below the outside air pressure causing air to rush into the lungs.

3. During an exhale, the diaphragm and intercostal muscles relax and the chest cavity gets smaller. This increases the pressure in the chest cavity above the outside air pressure. Air from the lungs (high pressure) flows out of the airways to the outside air (low pressure).

IV. Respiratory volume and capacities (see pages 749-750)

Air Moveme

nt

Mechanism Function

Coughing Deep breath is taken, glottis is closed, and air is forced against the closure; suddenly the glottis is opened and a blast of air passes upward

Clears lower respiratory passages

Sneezing Same as coughing, except air moving upward is directed into the nasal cavity by depressing the uvula

Clears upper respiratory passages

Laughing Deep breath is released in a series of expirations

Expresses happiness

Crying Same as laughing Expresses sadness

V. Non-respiratory air movements

Air Moveme

nt

Mechanism Function

Hiccuping Diaphragm contracts spasmodically while glottis is closed

No useful function known

Yawning Deep breath is taken Ventilates a larger proportion of the alveoli and aids oxygenation of the blood

Speech Air is forced through the larynx, causing vocal cords to vibrate; words are formed by lips, tongue, and soft palate

Vocal communication

VI. Breathing is controlled by the respiratory center in the brainstem

VII. Factors that affect breathing

Factors Receptors Stimulated

Response Effect

Stretch of tissues

Stretch receptors in visceral pleura, bronchioles, and alveioli

Inhibits inspiration

Prevents over inflation of the lungs during forceful breathing

Low blood pressure (O2)

Chemoreceptors in carotid and aortic bodies

Increases alveolar ventilation

Increases blood oxygen concentration

High blood pressure (CO2)

Chemosensitive areas of the respiratory center

Increases alveolar ventilation

Decreases blood carbon dioxide concentration

VII. Alveolar gas exchanges

A. Alveoli are microscopic air sacs clustered at the ends of the distal ends of respiratory tubes. They are surrounded by very thin membranes in contact with blood vessels.

B. Gasses diffuse from the alveoli to the blood vessels.