Respiratory System

Functions

• Gas exchange = respiration [series of events that includes ventilation, external respiration, transport of gases & internal respiration]

• Regulation of blood pH = reliant on CO2 levels

• Voice production = in larynx

• Olfaction = sense of smell : CN I

• Protection = mucus membranes, cilia

terminology

• Respiration = exchange of carbon dioxide and oxygen between atmosphere and body cells

– External respiration – exchange of gases at level of lungs

– Internal respiration – exchange of gases at tissue level

• Ventilation = breathing• inspiration – inhalation• expiration -exhalation

Upper respiratory tract = nose, sinuses, pharynx & larynx

Lower respiratory tract = trachea, bronchial tree & lungs

Nose – nasal bones and cartilage

Nasal cavity is separated by septum [formed by vomer & perpendicular plate of ethmoid]

Rhinitis = inflammation of nasal mucusa & excessive mucus production. Can be caused by virus, bacteria or irritants.

Sinuses: air filled cavities

Reduce the weight of the skull

Produce mucus

Influence voice quality – act as resonating chambers

Pharynx = throat. Nasophayrnx – posterior to the nasal cavity and extend to uvula. Oropharynx – posterior to the oral cavity extends from uvula to the hyoid bone. Laryngopharynx – from hyoid bone to the larynx

Larynx [also known as the voice box] Passageway for air.

9 cartilages: hyaline except for epiglottis, which is elastic.

During swallowing, epiglottis covers respiratory tract

Thyroid cartilage [Adam's apple] Vocal cords- vestibular folds /false

vocal cords, help to keep particles out of respiratory tract. True vocal cords – controlled by muscles that change tension for speaking. Opening between true cords is called glottis.

Trachea = windpipe. Supported by 15-20 ‘C’ shaped rings

Lined with a pseudostratified columnar epithelium similar to nasal passages. Has ciliary escalator

Divides into the right and left bronchi

The bronchial tree begins after the last tracheal ring – the carina. The right bronchi is shorter and more vertical. The bronchi branch into smaller and more numerous branches. The smallest bronchi are called bronchioles. They lead to the alveolar ducts – which terminate in the air sacs known as alveoli. Bronchioles are primarily composed of smooth muscle.

Alveoli are primarily simple squamous epithelium. This allows rapid diffusion of oxygen and carbon dioxide. Area of gas exchange = external respiration.

The lungs contain the bronchial tree and alveoli. They are soft and spongy. The lungs are encased by a double layered serous membrane called the pleura. The left has the ‘cardiac notch’.

terminology

• Respiration = exchange of carbon dioxide and oxygen between atmosphere and body cells

– External respiration – exchange of gases at level of lungs

– Internal respiration – exchange of gases at tissue level

• Ventilation = breathing

inspiration – inhalation

expiration -exhalation

Breathing is dependant on muscle movement and air pressure

Oxygenated air rushes down tract to the alveolar sacs where external respiration occurs. The exchange of gases is driven by CO2 diffusion.

External Respiration

Gases are transported by the blood. RBCs are primarily responsible for O2 transport, and the plasma transports the majority of the CO2.

Hemoglobin + Oxygen Oxyhemoglobin

Hb + O2 HbO2

Oxyhemoglobin --- Hemoglobin + Oxygen

HbO2 Hb + O2

Carbon Dioxide + Hemoglobin Carbaminohemoglobin

CO2 + Hb HbCO2

Carbon Dioxide is transported:

70% in the plasma as bicarbonate ions [ driven by carbonic anhydrase enzyme carried by RBCs]

23% combines with Hb to form HbCO2

7% dissolves in the plasma and is carried as CO2