It contains microscopic, fluid-filled tubules that run from the pulp to the underside of the enamel.

它包含微小的、充满液体的小管，从牙髓一直牙釉质下层。

ADH affects the last two-thirds of these tubes, called the distal convoluted tubule and the collecting ducts.

ADH作用于这些小管的终末2/3部分，即小管和集合管。

If your enamel is worn away, your dentin and its tubules can be exposed.

如果你的牙釉质被磨掉了，你的牙本质和它的小管就会暴露出来。

And this is showing us the digestive tubules of these animals.

这向我们展示了这些动物的消化管。

Macula densa cells are located in the distal convoluted tubule and they can sense when levels of sodium and chloride are low.

致密斑位于小管，可以感受钠和氯水平降低。

As the filtrate leaves the Bowman's capsule it flows into the renal tubule, which is surrounded by the peritubular capillaries.

滤液离开肾小囊后流入肾小管，后者被管周毛细血管网包围。

Some substances are removed from blood through the peritubular capillary network into the distal convoluted tubule or collecting duct.

有些物质通过管周毛细血管网从血液中移出，进入小管或集合管。

These are basically molds of the insides of your kidney’s tubules, and they can be a sign of kidney disease.

这些基本上是肾小管内部的霉菌，它们可能是肾脏疾病的征兆。

So when ADH is low, most of the water flows through the the distal convoluted tubule and the collecting duct, giving us diluted urine.

所以当血中ADH水平低时，大部分水就顺小管和集合管排出体外，尿液也就被稀释。

Within each kidney, there are about 1 million nephrons, and each nephron is made up of a renal corpuscle and a renal tubule.

每个肾约有100万个肾单位，每个肾单位由肾小体、肾小管组成。

Typically intrarenal AKI's due to damage to the tubules, the glomerulus, or the interstitium —the space between tubules.

通常，肾性AKI是由于肾小管、肾小球或间质空间（肾小管间的空间）损坏所致。

These tubules are important for sensory nerves as well, which use them to travel through the dentin from the pulp to the dentin-enamel junction.

牙本质中的小管对感觉神经也很重要，因为感觉神经可以通过它们从牙髓达本釉质交界处。

This allows sodium to move from the tubule into the cell, and then to get pumped into the blood by the sodium-potassium pumps.

这可以使钠离子从管腔移入细胞中，然后被钠钾离子泵泵入血中。

And at this point the distal tubule and collecting ducts of the nephron can either reabsorb or secrete potassium depending on what the body needs.

这时，小管和肾单位导管会根据需要重吸收或者分泌钾离子。

It's called a cast because it stays in essentially the same cylindrical shape as the tubule.

它被称为管型，是因为它基本上与小管保持相同的圆柱形状。

Now, before we dive too far in here, let's re-draw the nephron so that the structure of the renal tubule is a little more accurate.

现在，趁还没有学得更深，我们来画一个肾单位，让肾小管的结构更加精确。

This external balancing act is largely taken care of by the kidneys, where excess potassium is secreted into a renal tubule and excreted in the urine.

肾在外钾平衡起主要作用，它可以把多余的钾分泌肾小管中，然后从尿排出。

The odontoblasts have long processes, or arms, that lay within tiny tubules in the dentin - like an octopus sticking it's arms through a block of cement.

成牙质细胞有长长的突起，或者说长臂，伸入牙本质中的小管，就像章鱼的触角伸进水泥块被困住一样。

Now, that calcium's still in the lumen, but parathyroid hormone also affects the distal convoluted tubule and increases calcium reabsorption.

这时，钙仍然在腔内，但甲状旁腺激素也会影响小管，增加对钙的再吸收。

These pumps drive potassium from the blood into the cells and from there it flows down its concentration gradient into the tubule to be excreted as urine.

这些泵驱使钾从血液进入细胞内，细胞内的钾离子再顺浓度梯度进入肾小管，以尿液形式排泄。