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，但现在已经没有。

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

管动物王国的肛门种类繁多，但没有一个肛门是有骨头的。

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

但是自然界充满例外，奇怪的是，有些动物失去肛门。

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

相反，细菌由肠道达直肠、肛门，最终定居于会阴，成为正常菌群的一部分。

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

痔疮是肛门和直肠附近的肿胀静脉，会引起疼痛并导致瘙痒和出血。

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，管许多海参实际上是通过肛门呼吸的。

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

治疗疾病一般行根治手术，切除神经纤维缺失的肠段，然后将剩余肠段健康的一端连肛门。

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

海参本质上是一种无脑的肉质形式， 围绕着消化道，由嘴巴和肛门构成。

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

后口动物最常用的定义与我们的嘴巴和——科学秀评论区最爱的术语——肛门是如何发育有关。

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

大肠从回肠末端肛门，并分为四个部分：盲肠，结肠，乙状结肠和直肠。

We've talked before about just how mysterious and confusing the history of anus evolution is, and so we were excited to hear this news.

我们之前讨论过肛门进化史是多么神秘和令人困惑，所以听这个消息我们非常兴奋。

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.

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

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，一旦海参的肛门扩张， 它们就会潜入并躲避。

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，从嘴肛门的组织走廊。

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.

现在，我们把其余消化道的横截面放大来看，即从食管肛管的部分，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，肠道神经系统是一个由神经元组成的网状网络，控制着从食道肛门的整个消化道，它甚至不需要大脑控制。

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，许多物种都能够从它们的肛门中射出范围广泛的器官。

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，消化系统由一个30英尺长的内面由粘膜覆盖的管道组成，食物从管道的起始处-口进入体内，固体代谢废物在管道的末尾处-肛门排泄出去。

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，肠神经系统是一个广泛的网状神经元网络，控制着从食道肛门的整个消化道，它甚至根本不需要大脑。

The rectum serves as a reservoir for feces. It terminates in the lower opening of the gastrointestinal tract, the anus, which is the external opening through which feces are released from the body.

直肠作为粪便的容器，终止于胃肠道的下部开口，即肛门，肛门是粪便从身体排出的外部开口。