有關肺部一問

when we breathe in (inspiration), the diaphragm muscle contracts and become flattened, the external intercostal muscles also contract to move the rib cage upwards and outwards. both will cause an increase in thoracic volume. the pressure in thoracic cavity decrease and become lower than atmospheric pressure. Thus air from atmosphere rush into the lungs and the lung is inflated.

when we breath out (expiration), the diaphragm muscle relax and cause it become dome-shaped. the external interconstal muscle also relax and cause the rib cage move inwards and downwards. both cause a decrease in thoracic volume. the pressure in thoracic cavity increase and become higher than the atmospheric pressure. thus air is forced out from the lungs and the lung become deflated.

athletes' lungs aren't bigger, but their tidal volume and vital capacity will be larger than us due to their training. so they can breathing volume will be greater to facilitate gaseous exchange (O2 and CO2) to support the energy need for and remove wastes from exercise.

從外界空氣中吸入氧，使氧氣進入肺部血液，再運輸到身體各部份使用。另一方面，肺部血液裏的二氧化碳則滲透到氣泡裏，再排出體外。


橫隔膜幫助呼吸人的肺臟普遍右肺寬而短，左肺窄而長。兩肺之間有心臟和大血管、氣管、食道等器官。肺的下面被膈與腹腔臟器隔開。

肺的表面有漿膜（即臟胸膜），光滑、濕潤。肺柔軟而有彈性，肺內含有空氣，呈海綿狀。肺的顏色隨年齡和職業而有所不同，新生兒的肺為淡紅色；成人由於不斷吸入塵埃，沉積於肺而呈暗灰並有黑色斑點；老年人顏色更黑。


[編輯] 呼吸原理
外肋間肌 收縮 放鬆
內肋間肌 放鬆 收縮
肋骨和胸骨移動方向 外、上 內、下
橫隔膜肌 收縮 放鬆
橫隔膜 扁平 拱形
胸腔容量 大 小
胸腔壓力 小 大
肺部 擴張 縮小
肺內氣壓 低 高
效果 吸氣 呼氣


[編輯] 中醫
中醫認為「肺主氣，心主血，氣為血之帥」、「肺朝百脈，助心行血」，指肺能使百脈之氣血如潮水般有規律地週期運行。


[編輯] 其他動物的肺臟
爬蟲類動物的肺像一個大氣泡(bellows)一樣；
鳥類的肺又名循環肺；
魚類的肺只能讓血單向的流動。

2007-04-13 16:54:40 補充：
In air-breathing vertebrates, respiration occurs in a series of steps. Air is brought into the animal via the airways — in reptiles, birds and mammals this often consists of the nose; the pharynx; the larynx; the trachea (also called the windpipe);

2007-04-13 16:55:40 補充：
the bronchi and bronchioles; and the terminal branches of the respiratory tree. The lungs of mammals are a rich lattice of alveoli, which provide an enormous surface area for gas exchange. A network of fine capillaries allows transport of blood over the surface of alveoli.

2007-04-13 16:55:49 補充：
Oxygen from the air inside the alveoli diffuses into the bloodstream, and carbon dioxide diffuses from the blood to the alveoli, both across thin alveolar membranes.