RESPIRATORY SYSTEM

• The cardiovascular and respiratory systems share responsibility for supplying the body with oxygen and disposing of carbon dioxide.
• Respiratory system organs oversee the gas exchanges that occur between the blood and the external environment.
• The nose, whether “button” or “hooked” in shape, is the only externally visible part of the respiratory system.
• During breathing, air enters the nose by passing through the nostrils, or nares.
• The interior of the nose consists of the nasal cavity, divided by a midline nasal septum.
• Olfactory receptors for the sense of smell are located in the mucosa in the slitlike superior part of the nasal cavity, just beneath the ethmoid bone.
• The lateral walls of the nasal cavity are uneven, owing to three mucosa-covered projections, or lobes.
• The conchae greatly increase the surface area of the mucosa exposed to the air and the air turbulence in the nasal cavity.
• The nasal cavity is separated from the oral cavity below by a partition.
• Anteriorly, where the palate is supported by bone, the hard palate is the part of the palate that is bony and the soft palate is the unsupported posterior part.
• Crying is an emotionally induced mechanism that involves the release of air in a number of short expirations.
• Hiccups are sudden inspirations resulting from spasms of diaphragm, initiated by irritation of diaphragm or phrenic nerves, which serve diaphragm.
• Yawning is a very deep inspiration, taken with jaws wide open, that ventilates all alveoli, with some alveoli remaining collapsed during normal quiet breathing.
• Cleft palate, a genetic defect, results in breathing difficulty as well as problems with oral cavity functions, such as nursing and speaking.
• The nasal cavity is surrounded by a ring of paranasal sinuses located in the frontal, sphenoid, ethmoid, and maxillary bones.
• Nasolacrimal ducts, which drain tears from the eyes, also empty into the nasal cavities.
• Rhinitis, an inflammation of the nasal mucosa, can be caused by cold viruses and various allergens.
• Sinusitis, or sinus inflammation, is difficult to treat and can cause marked changes in voice quality.
• Surfactant cells produce a lipid (fat) molecule called surfactant, which coats the gas exposed alveolar surfaces and is very important in lung function.
• The major function of the respiratory system is to supply the body with oxygen and to dispose of carbon dioxide.
• Respiration consists of four distinct events: Pulmonary ventilation, External respiration, Respiratory gas transport, and Internal respiration.
• Pulmonary ventilation, or breathing, is a mechanical process that depends on volume changes occurring in the thoracic cavity.
• When the inspiratory muscles contract, the size of the thoracic cavity increases during inspiration.
• As the dome-shaped diaphragm contracts inferiorly, the superior inferior dimension (height) of the thoracic cavity increases during inspiration.
• Contraction of the external intercostals lifts the rib cage and thrusts the sternum forward, which increases the antero-posterior and lateral dimensions of the thorax during inspiration.
• The lungs adhere tightly to the thorax walls (because of the surface tension of the fluid between the pleural membranes), so they are stretched to the new, larger size of the thorax during inspiration.
• Intrapulmonary volume, or the volume within the lungs, increases during inspiration, causing the gases within the lungs to spread out to fill the larger space.
• The resulting decrease in gas pressure in the lungs during inspiration produces a partial vacuum (pressure less than atmospheric pressure outside the body), which causes air to flow into the lungs.
• Air continues to move into the lungs until the intrapulmonary pressure equals atmospheric pressure during inspiration.
• Expiration, or exhalation, is largely a passive process in healthy people that depends more on the natural elasticity of the lungs than on muscle contraction.
• If the respiratory passageways are narrowed by spasms of the bronchioles, expiration becomes an active process known as asthma.
• If the alveoli are clogged with mucus or fluid, expiration becomes an active process known as chronic bronchitis or pneumonia.
• Sinus headache occurs when the passageways connecting the sinuses to the nasal cavity are blocked with mucus or infectious matter, the air in the sinus cavities is absorbed, resulting in a partial vacuum and a sinus headache localized over the inflamed area.
• Hypoventilation or hyperventilation can dramatically change the amount of carbonic acid in the blood.
• Carbonic acid increases dramatically during hypoventilation and decreases substantially during hyperventilation.
• Acidosis or alkalosis occurs when the buffering ability of the blood is overwhelmed.
• Apnea, the cessation of breathing, can occur as a result of hyperventilation, often brought on by anxiety attacks.
• Cyanosis may occur if breathing stops for an extended time.
• Homeostatic imbalance can be caused by respiratory disorders such as chronic obstructive pulmonary disease (COPD) and lung cancer.
• COPD and lung cancer are examples of disorders that are “living proof” of the devastating effects of cigarette smoking on the body.