Anatomy of a snake. <i>1</i> – esophagus, <i>2</i> – trachea, <i>3</i> – tracheal lungs, <i>4</i> – rudimentary left lung, <i>5</i> – right lung, <i>6</i> – heart, <i>7</i> – liver, <i>8</i> – stomach, <i>9</i> – air sac, <i>10</i> – gallbladder, <i>11</i> – pancreas, <i>12</i> – spleen, <i>13</i> – intestine, <i>14</i> – testicles, <i>15</i> – kidneys.
<a href="//commons.wikimedia.org/wiki/User:Uwe_Gille" title="User:Uwe Gille">Uwe Gille</a>
CC BY 2.5
<span class="int-own-work" lang="en">Own work</span>