In this view of the rib cage the downward slope of the lower ribs from the midline outwards can be clearly seen. This allows a movement similar to the "pump handle effect", but in this case, it is called thebucket handle movement.
Breathing
The muscles of breathing at rest: inhalation on the left, exhalation on the right. Contracting muscles are shown in red; relaxed muscles in blue. Contraction of thediaphragm generally contributes the most to the expansion of the chest cavity (light blue). However, at the same time, the intercostal muscles pull the ribs upwards (their effect is indicated by arrows) also causing therib cage to expand during inhalation (see diagram on another side of the page). The relaxation of all these muscles during exhalation causes the rib cage and abdomen (light green) to elastically return to their resting positions. Compare these diagrams with the MRI video at the top of the page.
The muscles of forceful breathing (inhalation and exhalation). The color code is the same as on the RIGHT. In addition to a more forceful and extensive contraction of the diaphragm, the intercostal muscles are aided by the accessory muscles of inhalation to exaggerate the movement of the ribs upwards, causing a greater expansion of the rib cage. During exhalation, apart from the relaxation of the muscles of inhalation, the abdominal muscles actively contract to pull the lower edges of the rib cage downwards decreasing the volume of the rib cage, while at the same time pushing the diaphragm upwards deep into the thorax.
Thelungs do not inflate themselves; they expand only when thethoracic cavity volume increases.[6][7] Inmammals this expansion is produced mainly by contraction of thediaphragm and, to a lesser extent, by contraction of theintercostal muscles, which lift therib cage. During forcefulinhalation accessory muscles may augment thepump-handle andbucket-handle movements of the ribs to further increase chest volume. At rest exhalation is largely passive as inhalatory muscles relax and the elastic recoil of the lungs and chest wall returns the chest to its resting position. At this resting point the lungs contain thefunctional residual capacity(about 2.5–3.0 L in an adult human).[8]
During heavy breathing (hyperpnea), such as with exercise, exhalation also involves active contraction of the abdominal muscles, which pushes the diaphragm upward and reduces end-exhalatory lung volume. Even at maximum exhalation a normal mammal retains residual air in the lungs.[8]
Inhaled air is warmed and moistened by the wet, warm nasal mucosa, which consequently cools and dries. When warm, wet air from the lungs is breathed out through the nose, the cold hygroscopic mucus in the cool and dry nose re-captures some of the warmth and moisture from that exhaled air. In very cold weather the re-captured water may cause a "dripping nose".
Air is ideally inhaled and exhaledthrough the nose.[9] Thenasal cavities — divided by thenasal septum and lined with convolutedconchae — expose inhaled air to a large mucosal surface so it is warmed and humidified and particulate matter is trapped by mucus before reaching the lower airways. Some of the heat and moisture are recovered during exhalation when air passes back over cooler, partially dried mucus.[8][10]
Below the upper airways the mammalian respiratory system is commonly described as arespiratory ortracheobronchial tree. Larger conducting airways branch repeatedly into smaller bronchi and bronchioles; in humans there are on average about 23 branching generations. Proximal divisions transmit air, while terminal divisions (respiratory bronchioles, alveolar ducts and alveoli) are specialized for gas exchange. The trachea and major bronchi begin outside the lungs and most branching occurs within the lungs until the blind-ended alveoli are reached. This arrangement produces anatomicaldead space — the volume of conducting airways (about 150 ml in an adult) that does not participate ingas exchange.[8][11]
The primary purpose of breathing is to refresh alveolar air so gas exchange between alveolar air and pulmonary capillary blood can occur bydiffusion. This diffusion of gases occurs through the utilization of the thin respiratory membrane, which is composed of alveolar epithelium, capillary endothelium and the basement membrane that come together to form a blood-gas barrier.[12] After exhalation the lungs still contain thefunctional residual capacity; on a typical inhalation only a relatively small volume of new atmospheric air mixes with the FRC, so alveolar gas composition remains fairly constant across breaths. Pulmonary capillary blood therefore equilibrates with a relatively steady alveolar gas composition, andperipheral andcentral chemoreceptors sense gradual changes in dissolved gases rather than rapid swings. Homeostatic control of breathing thus centers on arterial partial pressures of CO₂ and O₂ and on maintaining bloodpH.[8]
Breathing rate and depth are regulated byrespiratory centers in the brainstem that receive input fromcentral andperipheral chemoreceptors. Centralchemoreceptors in themedulla are particularly sensitive topH and CO₂ in the blood andcerebrospinal fluid; peripheral chemoreceptors in theaortic andcarotid bodies are sensitive primarily to arterial O₂. Information from these receptors is integrated in thepons andmedulla, which adjust ventilation to restore blood gas tensions (for example, returning arterial CO₂ toward normal duringexercise). Motor nerves, including thephrenic nerves to the diaphragm, convey respiratory center outputs to the muscles of breathing. Although breathing is primarily automatic, it can be voluntarily modified forspeaking,singing,swimming, or breath-holding training;conscious breathing techniques may promote relaxation. Reflexes such as the diving reflex alter breathing and circulation during submersion to conserve oxygen.[8][13][14][15][16][17][18]
Following on from the above diagram, if the exhaled air is breathed out through the mouth in cold andhumid conditions, thewater vapor willcondense into a visiblecloud ormist.
Inhaled air is by volume 78%nitrogen, 20.95% oxygen and small amounts of other gases includingargon, carbon dioxide,neon,helium, andhydrogen.[19]
The gas exhaled is 4% to 5% by volume of carbon dioxide, about a hundredfold increase over the inhaled amount. The volume of oxygen is reduced by about a quarter, 4% to 5%, of total air volume. The typical composition is:[20]
In addition to air,underwater divers practicingtechnical diving may breathe oxygen-rich, oxygen-depleted or helium-richbreathing gas mixtures. Oxygen andanalgesic gases are sometimes given to patients under medical care. The atmosphere inspace suits is pure oxygen. However, this is kept at around 20% of Earthbound atmospheric pressure to regulate the rate of inspiration.[26]
Atmospheric pressure decreases with the height above sea level (altitude) and since the alveoli are open to the outside air through the open airways, the pressure in the lungs also decreases at the same rate with altitude. At altitude, a pressure differential is still required to drive air into and out of the lungs as it is at sea level. The mechanism for breathing at altitude is essentially identical to breathing at sea level but with the following differences:
The atmospheric pressure decreases exponentially with altitude, roughly halving with every 5,500 metres (18,000 ft) rise in altitude.[27] The composition of atmospheric air is, however, almost constant below 80 km, as a result of the continuous mixing effect of the weather.[28] The concentration of oxygen in the air (mmols O2 per liter of air) therefore decreases at the same rate as the atmospheric pressure.[28] At sea level, where theambient pressure is about 100 kPa, oxygen constitutes 21% of the atmosphere and the partial pressure of oxygen (PO2) is 21 kPa (i.e. 21% of 100 kPa). At the summit ofMount Everest, 8,848 metres (29,029 ft), where the total atmospheric pressure is 33.7 kPa, oxygen still constitutes 21% of the atmosphere but its partial pressure is only 7.1 kPa (i.e. 21% of 33.7 kPa = 7.1 kPa).[28] Therefore, a greater volume of air must be inhaled at altitude than at sea level in order to breathe in the same amount of oxygen in a given period.
During inhalation, air is warmed and saturated withwater vapor as it passes through the nose andpharynx before it enters the alveoli. Thesaturated vapor pressure of water is dependent only on temperature; at a body core temperature of 37 °C it is 6.3 kPa (47.0 mmHg), regardless of any other influences, including altitude.[29] Consequently, at sea level, thetracheal air (immediately before the inhaled air enters the alveoli) consists of: water vapor (PH2O = 6.3 kPa), nitrogen (PN2 = 74.0 kPa), oxygen (PO2 = 19.7 kPa) and trace amounts of carbon dioxide and other gases, a total of 100 kPa. In dry air, thePO2 at sea level is 21.0 kPa, compared to aPO2 of 19.7 kPa in the tracheal air (21% of [100 – 6.3] = 19.7 kPa). At the summit of Mount Everest tracheal air has a total pressure of 33.7 kPa, of which 6.3 kPa is water vapor, reducing thePO2 in the tracheal air to 5.8 kPa (21% of [33.7 – 6.3] = 5.8 kPa), beyond what is accounted for by a reduction of atmospheric pressure alone (7.1 kPa).
Thepressure gradient forcing air into the lungs during inhalation is also reduced by altitude. Doubling the volume of the lungs halves the pressure in the lungs at any altitude. Halving the sea level air pressure (100 kPa) results in a pressure gradient of 50 kPa but doing the same at 5500 m, where the atmospheric pressure is 50 kPa, a doubling of the volume of the lungs results in a pressure gradient of the only 25 kPa. In practice, because we breathe in a gentle, cyclical manner that generates pressure gradients of only 2–3 kPa, this has little effect on the actual rate of inflow into the lungs and is easily compensated for by breathing slightly deeper.[30][31] The lowerviscosity of air at altitude allows air to flow more easily and this also helps compensate for any loss of pressure gradient.
All of the above effects of low atmospheric pressure on breathing are normally accommodated by increasing the respiratory minute volume (the volume of air breathed in —or out — per minute), and the mechanism for doing this is automatic. The exact increase required is determined by therespiratory gases homeostatic mechanism, which regulates the arterialPO2 andPCO2. Thishomeostatic mechanism prioritizes the regulation of the arterialPCO2 over that of oxygen at sea level. That is to say, at sea level the arterialPCO2 is maintained at very close to 5.3 kPa (or 40 mmHg) under a wide range of circumstances, at the expense of the arterialPO2, which is allowed to vary within a very wide range of values, before eliciting a corrective ventilatory response. However, when the atmospheric pressure (and therefore the atmosphericPO2) falls to below 75% of its value at sea level, oxygenhomeostasis is given priority over carbon dioxide homeostasis. This switch-over occurs at an elevation of about 2,500 metres (8,200 ft). If this switch occurs relatively abruptly, the hyperventilation at high altitude will cause a severe fall in the arterialPCO2 with a consequent rise in thepH of the arterial plasma leading torespiratory alkalosis. This is one contributor tohigh altitude sickness. On the other hand, if the switch to oxygen homeostasis is incomplete, thenhypoxia may complicate the clinical picture with potentially fatal results.
Typical breathing effort when breathing through a diving regulator
Pressure increases with the depth of water at the rate of about oneatmosphere – slightly more than 100 kPa, or onebar, for every 10 meters. Air breathed underwater bydivers is at the ambient pressure of the surrounding water and this has a complex range of physiological and biochemical implications. If not properly managed, breathing compressed gasses underwater may lead to severaldiving disorders which includepulmonary barotrauma,decompression sickness,nitrogen narcosis, andoxygen toxicity. The effects of breathing gasses under pressure are further complicated by the use of one or morespecial gas mixtures.
Air is provided by adiving regulator, which reduces the high pressure in adiving cylinder to the ambient pressure. Thebreathing performance of regulators is a factor when choosing a suitable regulator for thetype of diving to be undertaken. It is desirable that breathing from a regulator requires low effort even when supplying large amounts of air. It is also recommended that it supplies air smoothly without any sudden changes in resistance while inhaling or exhaling. In the graph, right, note the initial spike in pressure on exhaling to open the exhaust valve and that the initial drop in pressure on inhaling is soon overcome as theVenturi effect designed into the regulator to allow an easy draw of air. Many regulators have an adjustment to change the ease of inhaling so that breathing is effortless.
Other breathing disorders includeshortness of breath (dyspnea),stridor,apnea,sleep apnea (most commonlyobstructive sleep apnea),mouth breathing, andsnoring. Many conditions are associated with obstructed airways. Chronic mouth breathing may be associated with illness.[32][33]Hypopnea refers to overlyshallow breathing;hyperpnea refers to fast and deep breathing brought on by a demand for more oxygen, as for example by exercise. The termshypoventilation andhyperventilation also refer to shallow breathing and fast and deep breathing respectively, but under inappropriate circumstances or disease. However, this distinction (between, for instance, hyperpnea and hyperventilation) is not always adhered to, so that these terms are frequently used interchangeably.[34]
A range ofbreath tests can be used to diagnose diseases such as dietary intolerances.Arhinomanometer uses acoustic technology to examine the air flow through the nasal passages.[35]
The word "spirit" comes from theLatinspiritus, meaning breath. Historically, breath has often been considered in terms of the concept of life force. TheHebrew Bible refers to God breathing the breath of life into clay to make Adam a living soul (nephesh). It also refers to the breath as returning to God when a mortal dies. The terms spirit,prana, the Polynesianmana, the Hebrewruach and thepsyche in psychology are related to the concept of breath.[36]
Intai chi,aerobic exercise is combined with breathing exercises to strengthen thediaphragm muscles, improve posture and make better use of the body'sqi. Different forms ofmeditation, andyoga advocate various breathing methods. A form ofBuddhist meditation calledanapanasati meaning mindfulness of breath was first introduced byBuddha. Breathing disciplines are incorporated into meditation, certain forms of yoga such aspranayama, and theButeyko method as a treatment for asthma and other conditions.[37]
Common cultural expressions related to breathing include: "to catch my breath", "took my breath away", "inspiration", "to expire", "get my breath back".
A young gymnast breathes deeply before performing his exercise.
Certain breathing patterns have a tendency to occur with certain moods. Due to this relationship, practitioners of various disciplines claim that they can encourage the occurrence of a particular mood by adopting the breathing pattern that it most commonly occurs in conjunction with. For instance, and perhaps the most common recommendation is that deeper breathing which utilizes the diaphragm and abdomen more can encourage relaxation.[13][38] Practitioners of different disciplines often interpret the importance of breathing regulation and its perceived influence on mood in different ways. Buddhists may consider that it helps precipitate a sense of inner-peace, holistic healers that it encourages an overall state of health[39] and business advisers that it provides relief from work-based stress.
During physical exercise, a deeper breathing pattern is adapted to facilitate greater oxygen absorption. An additional reason for the adoption of a deeper breathing pattern is to strengthen the body's core. During the process of deep breathing, the thoracic diaphragm adopts a lower position in the core and this helps to generate intra-abdominal pressure which strengthens the lumbar spine.[40] Typically, this allows for more powerful physical movements to be performed. As such, it is frequently recommended when lifting heavy weights to take a deep breath or adopt a deeper breathing pattern.
^Hall, John (2011).Guyton and Hall Textbook of Medical Physiology (12th ed.). Philadelphia, Pennsylvania: Saunders/Elsevier. p. 5.ISBN978-1-4160-4574-8.
^Pocock, Gillian; Richards, Christopher D. (2006).Human physiology: the basis of medicine (3rd ed.). Oxford: Oxford University Press. p. 311.ISBN978-0-19-856878-0.
^Pocock, Gillian; Richards, Christopher D. (2006).Human physiology: the basis of medicine (3rd ed.). Oxford: Oxford University Press. p. 320.ISBN978-0-19-856878-0.
^Pocock, Gillian; Richards, Christopher D. (2006).Human physiology: the basis of medicine (3rd ed.). Oxford: Oxford University Press. p. 316.ISBN978-0-19-856878-0.
^Levitzky, Michael G. (2013).Pulmonary physiology (Eighth ed.). New York: McGraw-Hill Medical. p. Chapter 1. Function and Structure of the Respiratory System.ISBN978-0-07-179313-1.
^Williams, Peter L; Warwick, Roger; Dyson, Mary; Bannister, Lawrence H. (1989).Gray's Anatomy (Thirty-seventh ed.). Edinburgh: Churchill Livingstone. pp. 1172–1173,1278–1282.ISBN0443-041776.
^Gilroy, Anne M.; MacPherson, Brian R.; Ross, Lawrence M. (2008).Atlas of Anatomy. Stuttgart: Thieme. pp. 108–111.ISBN978-1-60406-062-1.
^Kia, Nakisa; Bajaj, Tushar (2023).Histology: Respiratory Epithelium. National Library of Medicine: StatPearls Publishing. NBK541061.
^Thornton SJ, Hochachka PW (2004)."Oxygen and the diving seal".Undersea Hyperb Med.31 (1):81–95.PMID15233163. Archived from the original on 11 December 2008. Retrieved14 June 2008.
^Pedroso, F. S.; Riesgo, R. S.; Gatiboni, T; Rotta, N. T. (2012). "The diving reflex in healthy infants in the first year of life".Journal of Child Neurology.27 (2):168–71.doi:10.1177/0883073811415269.PMID21881008.S2CID29653062.
^Phillips, Michael; Herrera, Jolanta; Krishnan, Sunithi; Zain, Mooena; Greenberg, Joel; Cataneo, Renee N. (1999). "Variation in volatile organic compounds in the breath of normal humans".Journal of Chromatography B: Biomedical Sciences and Applications.729 (1–2):75–88.doi:10.1016/S0378-4347(99)00127-9.PMID10410929.
^abcTyson, P.D.; Preston-White, R.A. (2013).The weather and climate of Southern Africa. Cape Town: Oxford University Press. pp. 3–10,14–16, 360.ISBN978-0-19-571806-5.
^Diem, K.; Lenter, C. (1970).Scientific Tables (7th ed.). Basle, Switzerland: Ciba-Geigy. pp. 257–8.
^Koen, Chrisvan L.; Koeslag, Johan H. (1995). "On the stability of subatmospheric intrapleural and intracranial pressures".News in Physiological Sciences.10 (4):176–8.doi:10.1152/physiologyonline.1995.10.4.176.
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