Chapter 12 Gas Exchange in Humans Summary Bk2 Ch12 Gas Exchange in Humans/1 Table 1: Features and functions of human system (Section 12.1; Fig. 12.3) Structure Feature Function Nostrils A pair of openings on the nose For air to enter and leave the system Nasal cavity Pharynx Sensory cells on the surface Separated from the mouth cavity by the palate Detects chemicals in the air to give the sensation of smell Allows and chewing at the same time A common passage for air (into the larynx) and food (into the oesophagus) Larynx (the voice box ) (Fig. 12.4) Trachea (the windpipe ) and Bronchi Bronchioles (Fig. 12.6) Air sacs (Fig. 12.6) Lungs A box-like structure at the beginning part of the trachea Consists of several cartilages surrounding an opening called glottis There is a flap of cartilage called epiglottis above the larynx With two elastic membranes called vocal cords There are special muscles in the throat The trachea divides into two bronchi The walls are supported by incomplete rings of cartilage (also called C-shaped cartilages) Each bronchus branches into a network of small air tubes called bronchioles in each lung The bronchioles end in numerous tiny, thin-walled structures called air sacs or alveoli The air sacs are covered by a dense network of blood capillaries A pair of large spongy organs in the thoracic cavity Three lobes in the left lung; two lobes in the right lung Pink in colour because of the large amount of blood capillaries Covers the glottis during swallowing to prevent food from entering the trachea Produce voices by vibration when exhaled air passes through the glottis Control the tension of the vocal cords to produce voices of different pitches The right bronchus leads to the right lung, and the left bronchus leads to the left lung They keep the tubes open all the time to allow air to pass through Gas exchange takes place inside the air sacs Gas exchange takes place between air in the air sacs and blood in the capillaries 1
Thoracic cavity Thoracic cage (Fig. 12.7) Diaphragm Spongy because of the large number hollow and thin-walled air sacs Each lung is surrounded by a double layer of pleural membranes; the inner one in contact with the lung; the outer one in contact with the thoracic wall An air-tight pleural cavity is found between the inner and the outer pleural membranes, filled with pleural fluid The thoracic cage at the top and along the sides The diaphragm at the bottom The vertebral column at the back Ribs with intercostal muscles along the sides The sternum in the front A sheet of elastic tissue with strong muscles around its edge Table 2: Keeping the incoming air warm, moist and clean (Section 12.1; Fig. 12.10) Feature The surface of the nasal cavity is richly supplied with blood capillaries The lining of the nasal cavity, trachea and bronchi contains mucus-secreting cells which secrete a sticky fluid called mucus There is fine hair inside the nostrils There are mucus secreting cells on the lining of the nasal cavity The inner surface of the trachea and bronchi is covered with a ciliated epithelium with fine, hair-like structures called cilia; there are also mucus-secreting cells that secrete mucus Bk2 Ch12 Gas Exchange in Humans/2 The pleural membranes secrete pleural fluid The pleural fluid acts as a lubricant to reduce friction between the lungs and the rib cage during An air-tight cavity, allowing to take place 1. Enclosing and protecting the lungs 2. Contraction and relaxation of intercostal muscles lead to Contraction and relaxation of diaphragm muscles lead to Function The blood in the capillaries warms the incoming air The mucus moistens the incoming air It filters and traps large dust particles They secrete mucus that traps dust particles and bacteria Dust particles and bacteria in air are further trapped by the mucus, and are then swept by the beating of the cilia up to the pharynx where they are swallowed or coughed up Table 3: Composition of inhaled and exhaled air and changes inside the lungs (Section 12.2) Gas Inhaled air / Atmospheric air (%) Exhaled air (%) Change inside the lungs Oxygen 21 16 Taken up by the lungs Carbon dioxide 0.03 4 Released by the lungs 2
Bk2 Ch12 Gas Exchange in Humans/3 Nitrogen 78 78 No change Other gases 1 1 No change Water vapour variable saturated Released by the lungs Table 4: Gas exchange in the air sacs (Section 12.2; Fig. 12.16) Oxygen Concentration in air Relatively high Relatively low Concentration in blood entering the lungs Relatively low Relatively high Carbon dioxide Direction of diffusion Diffuses from air to blood Diffuses from blood to air The process of diffusion Concentration in blood leaving the lungs Function of the blood stream Importance of Oxygen first dissolves in the film of water covering the inner surface of the air sacs; it then diffuses across the walls of the air sacs and the capillary into the blood; most oxygen will combine with the haemoglobin inside the red blood cells Relatively high Keeps blood of low oxygen content entering the lungs, and blood of high oxygen content leaving the lungs, so that exchange of oxygen is continuous Maintains a high oxygen level in the air sacs so that gas exchange occurs continuously Carbon dioxide diffuses from the blood into the air sacs Relatively low Keeps blood of high carbon dioxide content entering the lungs, and blood of low carbon dioxide content leaving the lungs, so that exchange of carbon dioxide is continuous Maintains a low carbon dioxide level in the air sacs so that gas exchange can occur continuously Table 5: Adaptations of the air sacs for gas exchange (Section 12.2) Feature Air and blood are separated by two very thin walls; the wall of the air sacs and the capillary wall are only one cell thick The air sacs are very large in number The inner surface of the air sacs is covered with a film of water The air sacs are surrounded by a dense capillary network Function Gases can diffuse through them rapidly They provide a large surface area for gas exchange by diffusion Oxygen in the air can dissolve in it and diffusion can then take place This gives a rich supply of blood and allows rapid uptake of oxygen and removal of carbon dioxide 3
Bk2 Ch12 Gas Exchange in Humans/4 Table 6: Mechanism of (ventilation) (Section 12.3; Fig. 12.20) Inhalation / Inspiration Exhalation / Expiration / Breathing in / Breathing out Diaphragm muscles Contract Relax Shape of diaphragm Flattened Dome-shaped Intercostal muscles Contract Relax Movement of rib cage Upwards and outwards Downwards and inwards Volume of thoracic cavity and lungs Increases Decreases Air pressure inside thoracic cavity Decreases Increases Movement of air Air drawn into lungs Air forced out of lungs Table 7: The rate and depth of (Extension Study) (Section 12.4) Rate of Depth of Meaning The number of breaths within a period of time, usually expressed as the number of breaths in a minute The volume of air breathed in after an exhalation Methods of measurement Connects a data logger to a rate sensor (consisting of a belt and a pressure sensor), and wraps the belt around the chest, the pressure sensor measures the changes in pressure in the belt as the chest expands and constricts in (Practical 12.6) Records the number of breaths within a time period with the help of a stop watch (Practical 12.7) By using a spirometer By air out into a graduated container filled with water Table 8: The effects of exercise on (Extension Study) (Section 12.4) From rest to exercise From exercise to rest Energy needed for muscular activities Increases Decreases Rate of respiration Increases Decreases Rate of oxygen consumption Increases Decreases Rate of production of carbon dioxide Increases Decreases Rate of Increases Decreases Depth of Increases Decreases 4
Bk2 Ch12 Gas Exchange in Humans/5 Glossary gas exchange 氣體交換 5, 147 the exchange of gases (oxygen and carbon dioxide) between environment and organism through the respiratory surface system 呼吸系統 148 the body system in which organs are specialized for exchange of gases with the surroundings; in mammal, it composed of a pair of lungs connected to the atmosphere through a series of cavities and tubes air sac 肺泡 149, 151 alveolus (pl. alveoli), 肺泡 149 see air sac bronchiole 小支氣管 149, 151 bronchus 支氣管 149, 150 larynx 喉 121, 149 small sac-like cavity at the ends of the tracheoles in lungs; site of gas exchange between air and blood small air-conducting tube of lung, arising as branch of a bronchus, terminating in alveolus the tube that branches out from the trachea into the lung the organ to produce voice in most vertebrates, which is located between the trachea and the base of the tongue nasal cavity 鼻腔 149 cavity inside the nostril, lined with blood vessels and olfactory cells (cells for the sensation of smell); function is to warm and humidify inspired air, to clean and filter inspired air, and to sense the smell in the environment nostril 鼻孔 149 the external openings of the nose or respiratory organ pharynx 咽 120, 149 trachea 氣管 120, 149 the part of the alimentary canal of vertebrate which leads from the back of the mouth to the opening to oesophagus a tube connecting the throat to the lungs 生物與四周環境之間, 通過呼吸表面交換氣體 ( 氧和二氧化碳 ) 的過程 身體系統之一, 當中包括專門負責與四周環境進行交換氣體的器官 ; 在哺乳動物中包括一對肺, 肺經一連串的空腔與管道連接到大氣 肺部支氣管末端的細小囊狀空間, 是身體的血液與空氣之間進行氣體交換的位置 --- 肺內細小空氣通道管, 為支氣管的分支, 延伸至肺泡 從氣管分支出, 延伸至肺部的管道 大部分脊椎動物的發聲器官, 位處支氣管與舌頭的底部之間 鼻孔以內的空腔, 鼻腔壁佈滿血管和毛髮, 並會分泌黏液, 將吸入的空氣過濾, 並使其變得和暖 濕潤和清潔, 同時亦有嗅覺細胞, 負責感應環境的氣味 鼻子或呼吸器官對外的開口 脊椎動物消化道的一部分, 範圍由口的後方一直至食道的開口部分 連接喉嚨與肺部的管道 5
Bk2 Ch12 Gas Exchange in Humans/6 cartilage 軟骨 150, 294 epiglottis 會厭 121, 150 glottis 聲門 121, 150 skeletal tissue of vertebrates; covers the ends of the bones to reduce friction between the surfaces of bones during movement a flap-like structure protecting the opening of the larynx in mammals, so that food and drink will not get into the trachea during swallowing is the opening leading to the trachea, situated at the back of the pharynx palate 150 the roof of the mouth cavity of vertebrates, include the soft palate and hard palate sensory cell 感覺細胞 150, 227 the receptor that receives stimuli, such as light, vibration, heat and pressure vocal cord 聲帶 150 membrane-like structure in the larynx, vibrates to produce sound thoracic cavity 胸腔 151 cavity between the neck and waist region in terrestrial vertebrates; in mammals this cavity is separated from the abdomen by the diaphragm diaphragm 橫膈膜 152 a sheet of muscle that separates the thorax and abdomen; aids in intercostal muscle 肋間肌 152 muscle between the ribs, its contraction and relaxation brings out movement of the rib cage pleural cavity 胸膜腔 152 a large cavity in the thoracic cavity occupied by the lung pleural fluid 胸膜液 152 a fluid secreted by the pleural membranes; acts as a lubricant for reducing friction between the lungs and the rib cage during pleural membrane 胸膜 152 a thin layer of membrane surrounding the lungs; secretes pleural fluid into the pleural cavity 脊椎動物的骨骼組織 ; 覆蓋骨的末端以減低活動時骨面之間的摩擦 瓣狀結構, 保護哺乳動物在喉的入口處, 吞嚥時防止食物和飲品進入支氣管 支氣管的入口, 位處咽的後面 脊椎動物口腔的頂部, 包括軟和硬 負責接收刺激的感受器, 一般會接觸的刺激有光 震盪 熱和壓力 咽的膜狀結構, 其振動導致發出聲音 陸生脊椎動物的頸和腰之間的空腔 ; 哺乳動物的胸腔與腹部之間有橫膈膜將兩者分隔 分隔胸與腹的一片肌肉, 有助呼吸的進行 肋骨之間的肌肉, 肌肉的收縮和鬆弛會導致肋骨籃的移動 胸腔內肺佔據的大型空腔 由胸膜腔分泌的液體, 作為潤滑劑, 以減低呼吸時肺與肋骨籃所產生的摩擦 包圍肺的薄膜層, 分泌胸膜液進入胸膜腔 6
Bk2 Ch12 Gas Exchange in Humans/7 rib 肋骨 152 the bone forming the thoracic cage, protecting the heart and lung; dorsal end of the rib is attached to the thoracic vertebrae and the ventral end is attached either to the sternum, other ribs or no attachment rib cage 肋骨籃 152 the enclosing structure formed by the ribs and the bones to which they are attached sternum 胸骨 152 the vertical piece of bone on the ventral side of the body, connected with ribs vertebral column ciliated epithelium cilia (sing. cilium) 脊柱 152, 259, 296 a series of bones that extend from the head to the tail along the back of the body of vertebrate, enclosing the spinal cord 纖毛上皮 153 a layer of cells covered with cilia, lining at the surface of internal passages, the cilia beat periodically to bring about continuous movement of substances 纖毛 153 short hair-like structure projected from the surface of certain cells exhalation 呼氣 154 the act of pushing air from the lungs 構成胸籃的骨, 負責保護心臟和肺 肋骨的背端連接胸椎, 腹端連接胸骨或其他肋骨, 或不附在任何構造之上 由肋骨和與其連接的骨所圍起的構造 位於身體前方垂直的骨, 與肋骨連接 從脊椎動物的頭部一直延伸至尾部的一連串骨, 位於背部, 包圍脊髓 在體內管腔表面的一層被纖毛覆蓋的細胞層, 纖毛週期性地擺動, 不斷地帶動物質的移動 從部分細胞表面伸出的細小 毛髮狀構造 從肺部擠出空氣的動作 expiration 呼氣 154 see exhalation --- inhalation 吸氣 154 the act of drawing air into the lungs 將空氣抽入肺部的動作 inspiration 吸氣 157 see inhalation --- deoxygenated blood gas exchange surface 缺氧血 158 the blood in which haemoglobin have released oxygen 呼吸表面 158 the surface through which the body exchanges gases with the surroundings haemoglobin 血紅蛋白 70, 158, 189 oxygenated blood the red, iron-containing pigment in red blood cells; combines with oxygen and transports it to the tissues 含氧血 158 the blood in which oxygen is bound to the haemoglobin, blood in the pulmonary vein is of highest oxygen content 載有釋出了氧的血紅蛋白的血液 身體與四周環境進行氣體交換的表面 紅血球裡含鐵質的紅色色素 ; 負責氧氣結合並將氧氣運送到組織 含豐富氧的血液, 尤其是肺靜脈的血液, 氧分子與血液中的血紅蛋白結合 7
Bk2 Ch12 Gas Exchange in Humans/8 artificial respiration 人工呼吸 160 a procedure used to restore or maintain respiration in a person who has stopped ; the method uses mechanical or manual means to force air into and out of the lungs in a rhythmic fashion ventilation 換氣 161 the process of moving air into or out of the lung pneumothorax 氣胸 169 accumulation of air or gas in the pleural cavity, occurring as a result of disease or injury, or sometimes induced to collapse the lung in the treatment of tuberculosis and other lung diseases depth of rate of 呼吸深度 170 the volume of air breathed in following an exhalation 呼吸率 170 usually expressed in terms of the number of breaths in a minute spirometer 肺量計 170 an instrument for measuring the volume of air entering and leaving the lungs residual volume 餘氣量 174 the volume of air remains in the lungs after a strongest exhalation tidal volume 潮氣量 174 the volume of air inhaled and exhaled at each breath total lung capacity 總肺量 174 the total amount of air that can be present inside the lungs of a person; is the sum of the vital capacity and the residual capacity vital capacity 肺活量 174 the total amount of air displaced when one breathes in and out as deeply as possible carcinogenic 致癌的 176 concerning or containing a carcinogen (substance or agent that causes cancer) emphysema 肺氣腫 176 a lung disease in which the air sacs are destroyed and the remaining air sacs become larger, results in decrease vital capacity and increased airway resistance tar 焦油 176 a black, solid residue of tobacco smoke containing by-products of combustion 恢復或維持病人呼吸的步驟 : 當病人停止呼吸時, 利用人手或機械, 把空氣有節奏地泵入與抽出病人的肺部 空氣抽入及抽出肺部的過程 由疾病或受傷所引起, 是由於空氣或氣體在胸膜腔積聚, 是致 醫生間中亦會應用到氣胸現象來使病人的肺下陷, 以治療結核病和其他的肺病 緊接呼氣後所吸入的空氣量 通常以每分鐘的呼吸次數作表示 量度進出肺的空氣體積的儀器 盡力呼氣後肺內所剩下的空氣的體積 每次呼吸時吸入與呼出的空氣體積 人體肺內可容納的空氣總量, 是肺活量與餘氣量的總和 在最深的一次呼吸之後, 可以吸入或呼出的最大空氣容量 含有會致癌的物質的, 或與引發癌症有關的 肺病的一種, 由於部分肺泡受破壞, 以致其他肺泡增大, 肺活量下降, 而通氣的管道的阻力增加, 長期會致命 燃燒煙草時, 煙霧中的黑色固體副產物 8
Bk2 Ch12 Gas Exchange in Humans/9 coronary heart disease 冠心病 90, 180 a structural or functional abnormality of the heart, or of the blood vessels supplying the heart, that impairs the normal pumping action of the heart 心臟或為心臟供血的血管中出現結構性或功能性的病變, 令心臟無法維持正常的泵壓活動 9