lungs


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Related to lungs: lung cancer

infanticide

Forensic medicine The active or semi-passive killing of a viable conceptus > 20 gestational wks, which breathes spontaneously. See Battered child syndrome, Child abuse. Cf Stillbirth.
Infanticide, diagnosis of  
'Hard' criteria
•  Comparison of gastric fluid composition with that of a toilet bowel-active drowning
•  Peural surfaces with petechiae Seen in induced suffocation, most significant when coupled with hematomas and petechiae on the mouth and epiglottis; the lingual frenulum may be torn and the lips bruised, indicating active attempts to suffocate infant.
•  Lungs Stillbirth lungs are not aerated and do not float
•  Edematous foam on nostrils An indicator of active breathing
•  Meconium Resuscitation of a true stillborn may push meconium into the perianal region, but extensive staining of the placenta and umbilical cord is due to antenatal stress
'Soft' criteria
•  Denial of pregnancy If the woman is obese or a dullard, she may not know she was pregnant
•  Rigor mortis A finding that is poorly appreciated in neonates
•  Impression of the body in soil, blood, or fomites, requiring diligent and timely scene investigation
•  Maceration of skin A finding typical of stillbirth
•  Putrefaction Stillborns do not putrefy as they have sterile bowels
•  Umbilical cord A cut cord indicates active intervention-time undetermined; an intact cord is consistent with stillbirth
•  Determination of age Viability, most fetuses born before 18 wks of gestation die despite resuscitative efforts, age is determined by skeletal dating, antenatal studies corroborating fetal death, eg Spaulding sign of in utero death characterized by overlapping cranial bones  

lungs

The paired, air-filled, elastic, spongy organs occupying each side of the chest and separated by the heart and the central partition of the chest known as the mediastinum. Each lung is surrounded by a double-layered membrane called the PLEURA. The function of the lungs is continuously to replenish the oxygen content of the blood and to afford an exit path from the blood for carbon dioxide and other unwanted gases. The right lung has three lobes and the left two. An air tube (BRONCHUS) and a large artery and vein enter each lung on its inner aspect and these branch repeatedly as they pass peripherally. The smallest air passages end in grape-like clusters of air sacs, the alveoli, the walls of which are very thin and contain the terminal branches of the blood vessels. In this way the air comes into intimate contact with the blood so that interchange of gases can readily occur.

ventilation

in physiology and medicine, refers to pulmonary ventilation, the movement of air in and out of the lungs, whether during normal breathing, or by artificial means. total ventilation or minute volumeE (or I) is the volume breathed out (or in) in litres per minute: the tidal volume multiplied by the number of breaths per minute. May be measured, e.g. by collecting the expired gas over a known time (Douglas bag method), or by integrating inspired or expired airflow with respect to time (by pneumotachograph). The effective component, alveolar ventilationA, refers to that which reaches the regions of the lungs where gas exchange occurs, and is equal to the total ventilation minus dead space ventilationD. Normally, at rest, A : D = 2:1 or typically, E - D = A, 6 - 2 = 4 L.min-1. When ventilation increases in exercise, the dead space is unchanged, so D rises only in proportion to the rise in frequency of breaths, but E rises relatively more as tidal volume also increases. See also artificial ventilation, dead space, lung volumes and capacities.

pulmonary function tests

tests for assessment of the function of the lungs ( aka respiratory function tests) to aid diagnosis of respiratory disease and assess effectiveness of treatment. Includes methods for measuring lung volumes and gas transfer. In sport, primarily used in the diagnosis and monitoring of treatment of asthma, especially exercise-induced asthma; WADA guidelines have now set criteria based on such tests, whereby an athlete may use certain inhaled medication. See also blood gases.
Lung volumes.

lung volumes

measurements made as part of pulmonary function tests; the volumes that move in and out during the normal breathing cycle, and with deliberate additional effort, can be measured directly by spirometry with the subject breathing through a closed circuit in and out of a cylinder inverted over water, or into a vitalograph, or by pneumotachograph; the residual volume can be measured only indirectly by dilution methods (usually with helium) or by whole body plethysmography. See also ventilation. See figure and table overleaf .
Table 1: Lung volumes
VT (TV)Tidal volumeVolume of inspired/expired air moving in and out with each breath
IRV
ERV
Inspiratory and expiratory reserve volumesUsed when tidal volume increases above that at rest
VCVital capacityVolume that can be inspired/expired after full expiration/inspiration
FEV1Forced expiratory volume in 1sVolume exhaled in the first second, with maximal effort after full inspiration
FRCFunctional residual capacityVolume remaining in the lungs at end-expiration; decreases as tidal volume increases
RVResidual volumeRemains after a maximal expiratory effort; cannot be exhaled
TLCTotal lung capacityVital capacity + residual volume

breathing

the regular inflation and deflation of the lungs, serving the purpose of respiratory gas exchange aka pulmonary ventilation . Breathing and its pattern - the depth and frequency of breaths - are controlled by a group of neurons in the brain stem, and vary in response to changes in afferent information from several sites, notably the chemoreceptors (sensitive to changes in oxygen, CO2 and pH in arterial blood, and to the pH in the brain) and from muscles and joints (which signal changes in activity). The output from this 'respiratory centre' regulates, via the phrenic nerves, the frequency and strength of contraction of the diaphragm, which accounts alone for breathing at rest. With increasing demand, the intercostal muscles contribute additional lung inflation/deflation by their action on the size and shape of the ribcage, assisted when breathing is deepest by the accessory muscles of respiration, including neck, chest and abdominal muscles. See also apnoea, dyspnoea, ventilation.
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