And the dentin acts as the selectively permeable barrier.

而牙本质则作为选择性渗透的屏障。

Osmosis is the movement of something like water across a selectively permeable barrier.

渗透是指像水这样的东西跨越选择性渗透的屏障的运动。

It is working on a system that filters air through a selectively permeable membrane.

该公司正在研究一种通过选择性渗透膜过滤空气的系统。

Many of these boundaries that the cells form aren't absolute — instead, they're selectively permeable, allowing for some level of absorption, filtration, and excretion of substances.

细胞形成的许多边界不是绝对的——相反，它们是选择性渗透的，允许某种程度的吸收，过滤和排泄物质。

Usually, all plasma membranes are selectively permeable barriers which allow certain ions and molecules to pass in and out of the cell while preventing the movement of others.

通常来说，所有质膜都是选择性渗透的屏障，允许特定的离子与小分子进入或离开细胞，同时阻止其它离子或小分子的转运。

We also talked about how epithelial cells are polar, having both apical and basal sides, and are selectively permeable, and lastly we took a brief look at how our glandular epithelial tissue forms both out endocrine and exocrine glands.

我们还讨论了上皮细胞是如何极性的，具有顶端和基底两侧，并且具有选择性渗透性，最后我们简要了解了我们的腺上皮组织如何形成内分泌腺和外分泌腺。