Respiratory system facts:

• 1,500 mi of airways• 300 to 500 million alveoli w/ total surface area of

about one side of a tennis court• 616 miles of capillaries

Functions of the Respiratory System

• Warm, moisten, and filter air• External, internal, and cellular

respiration• Homeostasis of gases and ph• Production of sound (vocal folds)

Lungs

• Fill thoracic cavity• Separated by mediastinum and heart• Upper part = apex• Lower part = base• Base fits snugly over diaphragm• Lung tissue porous and spongy – it floats• R lung = larger and shorter (displaced by the

liver) and has 3 lobes• L lung = smaller (displaced by heart) and has 2

lobes

Respiratory Movements

• 1 inspiration + 1 expiration = 1 respiration• Normal adult = 14 – 20 respirations / min• Age dependent - newborn = 40 – 60 / min• Increases with exercise, body temperature, certain diseases• Sleep = respirations ↓• Emotion can ↑ or ↓

Pulmonary Ventilation (Breathing)

• Inspiration – Intercostal muscles lift ribs outward, sternum rises and the diaphragm

contracts and moves downward – this increases the volume of the lungs (creating negative pressure) and air rushes down pressure gradient into lungs

• Expiration– Opposite action takes place– Exhalation is a passive process

Diaphragm

• Large dome-shaped muscle that contracts rhythmically, continually, and most of the time, involuntarily.

Pleura

• Thin, moist slippery serous membranes surround the lungs• Each lung is enclosed in double-walled sac• Visceral pleura attached to lung; parietal attached to thoracic cavity• Space is pleural cavity – filled with pleural fluid to prevent friction

Nasal cavity and SinusesNasal turbinates• Essential for functional breathing• Guide, heat, humidify and filter air• Ciliated pseudostratified columnar

epithelia• Contain thermoreceptors• Chemoreceptors (for olfaction) in

superior turbinates

Nasal sinuses• Air filled-cavities• Create vocal resonance• Heat inhaled air

Pharynx

• The throat• Common passageway for air and food• ~5” long• Divided into:

– Nasopharynx– Oropharynx– Laryngopharynx

When food is swallowed, the cartilaginous epiglottis closes over the opening to the larynx, preventing food from entering the lungs.

Larynx

• Voice box• Triangular chamber below

the pharynx• Within the larynx are vocal

folds (glottis)• Adam’s Apple

Vocal fold video

Trachea

• Windpipe• ~4 ½” long• Walls are alternate bands of membrane and C

shaped rings of hyaline (glassy) cartilage – to keep trachea open

• Lined with ciliated pseudostratified columnar mucous membranes

• Coughing and expectoration gets rid of dust-laden mucous

Bronchi and bronchioles

• Lower end of trachea divides into R and L bronchus• As they enter lungs, subdivide into bronchial tubes and bronchioles• Bronchi – similar to trachea with ciliated simple columnar mucous membrane

and hyaline cartilage

• Bronchial tubes – cartilaginous plates (instead of C-shaped rings).

• Bronchioles – thinner walls of smooth muscle, lined with ciliated epithelium. Hyaline cartilage changes to smooth muscle in bronchioles and simple cuboidal cells transition to simple squamous epithelial cells.

• Alveolar ducts – small branches that terminate into 2 or 3 alveolar sacs.

• Gas exchange occurs in both the alveolar ducts and alveolar sacs.

• “Conducting zone”• Upper and lower respiratory passages• Ciliated pseudostratified columnar

• “Respiratory zone”• Mostly simple squamous• Site of gas exchange

• Respiratory bronchioles• Alveolar ducts• Alveolar sacs

Alveoli• Composed of a single layer of epithelial tissue• Alveoli are covered internally by a surfactant produced

by simple cuboidal cells. • Inner surfaces covered with surfactant – to keep alveoli

from collapsing• Each alveolus surrounded by capillaries• O2 and CO2 exchange takes place between the alveoli

and capillaries (diffusion)• Oxygen and carbon dioxide must be

absorbed in water to diffuse across alveolar/capillary membranes

• Macrophages patrol alveolar surfaces and consumer foreign material

Inhaled air

Oxygen 21%

Water vapor .05%

Nitrogen 79%

Carbon dioxide .02%

Exhaled air

Oxygen 16%

Water vapor 6.2%

Nitrogen 74%

Carbon dioxide 4%

• Oxygen is the MOST critical substance needed by the body for survival.– We can only live about 4-6 minutes without oxygen.

• Clinical death – the moment breathing and heartbeat stop

• Biological death – when brain cells die, irreversible after 6 – 10 minutes

• Constant removal of carbon dioxide is just as important for survival – maintains homeostasis

• Cellular respiration – oxygen combines with stored nutrients in cells to release energy, carbon dioxide, and water.

• Respiratory system supplies oxygen and removes carbon dioxide

• Carbon dioxide leaves enters blood as carbonic acid and is dissolved into plasma as bicarbonate

• Carbonic anhydrase (in RBCs) catalyzes disassociation of hydrogen ion to form bicarbonate

• Increase of hydrogen ions decreases ph (increases acidity) of blood

• Carbonic anhydrase again catalyzes bicarbonate into carbon dioxide in the lungs

• Carbon dioxide is then released in the lungs

• Drop in blood's pH stimulates chemoreceptors in the carotid and aortic bodies in the blood system to send nerve impulses to the respiration center in the brain causing increased respiration.

• Hyperventilation – response to accumulated CO2 in blood or panic state• Rapid clearing of CO2• Can result in respiratory alkalosis • Paper bag rebreathing is ineffective and dangerous when confused with

heart attack or asthma symptoms

• Hypoventilation – (respiratory depression) inadequate ventilation• Build-up of CO2• Can lead to respiratory acidosis• Neurons are particularly susceptible to acidic conditions• Common cause of death from many recreational drugs

• Mammalian diving reflex– Present in all mammals but exhibited strongest in aquatic mammals– Thermoreceptors on face respond to cold water causing bradycardia,

vasoconstriction, and other responses that allow extended periods of oxygen deprivation while under water.

– This is the reflex that allows some individuals, especially children, to be resuscitated after hours of oxygen deprivation while submerged in cold water.

• Yawning– CO2?– Stretching?– Alertness?– Brain temperature?– Emotions/mood/appetite?– Anxiety?– Empathy?– Territorialism?