There are even anuses that come and go.

甚至还有会会消失的肛门。

But nature's full of exceptions, and strangely, some animals have lost their anuses.

但是自然界充满了例外，奇怪的是，有些动物失去了肛门。

As varied as the animal kingdom's anuses are, none of them have bones.

尽管动物王国的肛门种类繁多，但没有个肛门是有骨头的。

Brittle stars and many parasites had ancestors with anuses, but no longer have them.

海蛇尾和许多寄生虫的祖先有肛门，但在已经没有了。

Instead, from the gut, bacteria get to the rectum, anus and eventually colonizes the perineum, becoming part of the normal flora.

相反，细菌由道到达直、肛门，最终定居于会阴，成为正常菌群的部分。

Hemorrhoids are swollen veins near the anus and rectum, which can be painful and lead to itching and bleeding.

痔疮是肛门和直附近的肿胀静脉，会引起疼痛并导致痒和血。

Specialized tube feet can be used for feeding and respiration, though many sea cucumbers actually breathe through their anuses.

专门的管脚可用于进食和呼吸，尽管许多海参实际上是通过肛门呼吸的。

A sea cucumber is essentially a brainless, fleshy form surrounding a digestive tract, bookended by a mouth and an anus.

海参本质上是种无脑的肉质形式， 围绕着消化道，由嘴巴和肛门构成。

Treatment is typically surgical resection of the area that's lacking the nerve fibers, and then the healthy end is connected to the anus.

治疗疾病般行根治手术，切除神经纤维缺失的段，然后将剩余段健康的端连肛门。

The most widely-used definition of deuterostome has to do with how our mouths and — the SciShow comments’ favorite term — anuses develop.

最广泛使用的后口动物定义与我们的嘴巴和——SciShow 评论最喜欢的术语——肛门的发育方式有关。

Extending from the end of the ileum to the anus, it is divided into four parts: cecum, colon, sigmoid colon and rectum.

大末端延伸到肛门，并分为四个部分：盲，结，乙状结和直。

Certain species of crabs and pearlfish take advantage of this rhythmic action and, once the sea cucumber's anus is dilated, they shimmy in and take shelter.

某些种类的螃蟹和珍珠鱼利用这种有节奏的动作，旦海参的肛门扩张， 它们就会潜入并躲避。

It's obvious that reversing the other axes of the body, the back and belly, or the mouth and the anus, would have some serious evolutionary consequences.

很明显，反转身体的其他轴，背部和腹部，或嘴巴和肛门，会产生些严重的进化后果。

Unlike its cousin, ulcerative colitis, which only affects the large intestine, Crohn disease causes inflammation and tissue destruction anywhere along the gastrointestinal tract, from the mouth to the anus.

虽与溃疡性结炎同属炎症性病，但溃疡性结炎只侵犯大，而克罗恩病能引起胃道任何部位的炎症和组织破坏，上至口腔，下达肛门。

We — and all animals from the simplest worms on up the Tree of Life — are really just tubes, corridors of tissue running from a mouth to an anus.

我们——以及生命之树上最简单的蠕虫——实际上只是管子，嘴到肛门的组织走廊。

By loosening the attachments of internal tissues then quickly softening and contracting their muscles, many species are capable of shooting a wide range of organs out of their anuses.

通过松开内部组织的附着物，然后迅速软化和收缩它们的肌肉，许多物种都能够它们的肛门中射范围广泛的器官。

Now if we zoom into a cross-section of the rest of the gastrointestinal tract, anywhere from the esophagus till the anus, the walls are typically lined by the same four layers of tissue.

在，我们把其余消化道的横截面放大来看，即食管到肛管的部分，其管壁通常都由相同的四层组织构成。

In fact, the enteric nervous system, which is an extensive mesh-like network of neurons that controls your entire digestive tract from the esophagus to the anus, doesn't even require the brain at all.

事实上，道神经系统是个由神经元组成的网状网络，控制着食道到肛门的整个消化道，它甚至不需要大脑控制。

Anatomically, the digestive system consists of a 30-foot long, mucous membrane-lined tube beginning with the mouth, where food enters the body, and ending with the anus, where solid waste is excreted.

在解剖学上，消化系统由个30英尺长的内面由粘膜覆盖的管道组成，食物管道的起始处-口进入体内，固体代谢废物在管道的末尾处-肛门排泄去。

In fact, the enteric nervous system, which is an extensive mesh-like network of neurons that controls your entire digestive tract from the esophagus to the anus, doesn’t even require the brain at all.

事实上，神经系统是个广泛的网状神经元网络，控制着食道到肛门的整个消化道，它甚至根本不需要大脑。