When a mammal breathes in, the concentration of oxygen is higher in the alveolus than in the red blood cells. Therefore, oxygen leaves the alveolus and enters the red blood cells. When a mammal breathes out, the opposite happens. The concentration of carbon dioxide is lower in the alveolus than in the red blood cells, so carbon dioxide leaves the red blood cells, enters the alveolus, and is exhaled.
w ɛ n WORD_BOUNDARY ʌ WORD_BOUNDARY m æ m ə l WORD_BOUNDARY b ɹ iː ð z WORD_BOUNDARY ɪ n ð ə WORD_BOUNDARY k ɑ n s ə n t ɹ eɪ ʃ ə n WORD_BOUNDARY ʌ v WORD_BOUNDARY ɑ k s ɪ d̠ʒ ə n WORD_BOUNDARY ɪ z WORD_BOUNDARY h aɪ ə ɹ ɹ WORD_BOUNDARY ɪ n ð ɪ WORD_BOUNDARY æ l v ɪ oʊ l ə s WORD_BOUNDARY ð ʌ n WORD_BOUNDARY ɪ n ð ə WORD_BOUNDARY ɹ ɛ d WORD_BOUNDARY b l ʌ d WORD_BOUNDARY s ɛ l z WORD_BOUNDARY ð ɛ ɹ f ɔ ɹ WORD_BOUNDARY ɑ k s ɪ d̠ʒ ə n WORD_BOUNDARY l iː v z WORD_BOUNDARY ð ɪ WORD_BOUNDARY æ l v ɪ oʊ l ə s WORD_BOUNDARY æ n d WORD_BOUNDARY ɛ n t ə ɹ z WORD_BOUNDARY ð ə WORD_BOUNDARY ɹ ɛ d WORD_BOUNDARY b l ʌ d WORD_BOUNDARY s ɛ l z WORD_BOUNDARY w ɛ n WORD_BOUNDARY ʌ WORD_BOUNDARY m æ m ə l WORD_BOUNDARY b ɹ iː ð z WORD_BOUNDARY aʊ t WORD_BOUNDARY ð ɪ WORD_BOUNDARY ɑ p ə z ɪ t WORD_BOUNDARY h æ p ə n z WORD_BOUNDARY ð ə WORD_BOUNDARY k ɑ n s ə n t ɹ eɪ ʃ ə n WORD_BOUNDARY ʌ v WORD_BOUNDARY k ɑ ɹ b ə n WORD_BOUNDARY d aɪ ɑ k s aɪ d WORD_BOUNDARY ɪ z WORD_BOUNDARY l oʊ ə ɹ ɹ WORD_BOUNDARY ɪ n ð ɪ WORD_BOUNDARY æ l v ɪ oʊ l ə s WORD_BOUNDARY ð ʌ n WORD_BOUNDARY ɪ n ð ə WORD_BOUNDARY ɹ ɛ d WORD_BOUNDARY b l ʌ d WORD_BOUNDARY s ɛ l z WORD_BOUNDARY s oʊ WORD_BOUNDARY k ɑ ɹ b ə n WORD_BOUNDARY d aɪ ɑ k s aɪ d WORD_BOUNDARY l iː v z WORD_BOUNDARY ð ə WORD_BOUNDARY ɹ ɛ d WORD_BOUNDARY b l ʌ d WORD_BOUNDARY s ɛ l z WORD_BOUNDARY ɛ n t ə ɹ z WORD_BOUNDARY ð ɪ WORD_BOUNDARY æ l v ɪ oʊ l ə s WORD_BOUNDARY æ n d WORD_BOUNDARY ɪ z WORD_BOUNDARY ɛ k s h eɪ l d WORD_BOUNDARY