皮肤

Lesson Objectives
::经验教训目标

• Describe the layers of the skin.
  ::描述皮肤的层层。

• Identify functions of the skin.
  ::皮肤识别功能 。

• Explain what you can do to help keep your skin healthy.
  ::解释一下你能做些什么来保持皮肤健康。

Lesson Vocabulary
::词汇表课程

• dermis
  ::皮肤

• epidermis
  ::皮下皮下皮

• hair follicle
  ::毛发

• sweat gland
  ::出汗克

Introduction
::导言

Whoa! It's really hot. Your skin gets warm and you start to sweat. The sweat is pouring out of you. Sweating is your body's way of keeping you from getting too warm.   
::哇,好热啊,你的皮肤变暖了,你开始出汗了 汗流出来了,汗流出来了

Skin is a major organ. It helps to protect you. It is the outer covering of your body. 
::皮肤是主要的器官 有助于保护你 这是你身体的外罩

Skin Structure
::皮肤结构

From the outside, the skin looks plain and simple. You can see a closer look in  Figure   . Can you believe your eyes? There is nothing plain or simple about skin. A single square inch of skin contains about 20 blood vessels. There are also hundreds of sweat glands.
::从外表看,皮肤看起来简单明了。您可以在图中看到更近的外观 。 您能否相信您的眼睛? 皮肤没有简单明了的外观 。 一平方英寸的皮肤含有大约20个血管, 还有数百个汗腺 。

Your skin is filled with nerve endings. This is what enables you to feel things. When you feel something rough or smooth, you can thank your skin. Your skin also contains tens of thousands of cells that produce pigment. Pigment is what gives your skin its color. Clearly, there is much more to skin than meets the eye! 
::你皮肤上充满了神经末端。这能使你感觉东西。当你感到粗糙或光滑时,你可以感谢你的皮肤。你的皮肤上还有成千上万个产色的细胞。颜料使你的皮肤染上颜色。显然,皮肤比眼睛多得多。

The skin is only about 2 mm thick. Although it is very thin, it consists of two distinct layers. These layers are called the epidermis and the dermis. You can see both layers and some of their structures in  Figure   . 
::皮肤只有大约2毫米厚。 虽然皮肤很薄, 但由两层不同的层组成。 这些层被称为皮层和皮层。 您可以在图中看到两层和部分结构 。

Epidermis
::流行病

The epidermis is the outer layer of skin. There are no blood vessels, nerve endings, or glands in this skin layer. Though it may not seem like it, this layer of skin is very active. It is constantly being renewed. How does this happen?
::皮层是皮肤的外层。 皮层中没有血管、 神经末端或腺。 虽然表层看起来不像, 但皮肤的这一层非常活跃。 它不断更新。 怎么会这样呢 ?

1. The cells at the bottom of this layer are always being produced. 
   ::此层底部的单元格总是在生成中 。

1. The new cells slowly move up to the surface. 
   ::新的细胞慢慢地向上移动到表面。

1. By the time the cells reach the surface, they have died. It's true, the outermost layer of your skin is dead. Don't worry, this is what forms the protective layer. This outer layer is even waterproof. 
   ::当细胞到达表面时,它们就死了。确实,你的皮肤最外层是死的。别担心,这就是保护层。这个外层甚至是防水的。

1. Dead cells are gradually falling off. As they are shed, they are replaced by other dead cells. 
   ::死细胞正在逐渐消失,随着它们被挖出,被其他死细胞所取代。

The epidermis also contains cells that give skin its color. These cells are what produces the brown pigment in skin. Everyone’s skin has about the same number of these cells. However, these cells of people with darker skin produce more pigment. The amount of pigment depends on two things. Some of it depends on what you inherit from your parents. It also depends on how much sunlight strikes your skin. The more light that hits your skin, the more tanned you get. 
::皮层外皮还包含给皮肤颜色带来颜色的细胞。 这些细胞是产生皮肤棕色色的产物。 每个人的皮肤与这些细胞的数量大致相同。 然而,这些皮肤更深的人的细胞产生更多的色素。 色素的数量取决于两件事。 其中一部分取决于你从父母那里继承什么。 也取决于阳光如何照射你的皮肤。 皮肤受到的光线越大,皮肤就越黑。

Dermis
::底底环

The dermis is the inner layer of skin. The dermis has blood vessels and nerve endings. The nerve endings explain why your skin is sensitive. You can sense pain, pressure, and temperature.
::皮肤是皮肤的内层。 皮肤有血管和神经末端。 神经末端解释了为什么皮肤敏感。 您可以感觉到疼痛、 压力和温度 。

Ouch! You cut your finger and it starts to bleed. What has happened? If your skin bleeds, it means you have cut the dermis layer and damaged blood vessels. The cut really hurts. It hurts because of the nerve endings in this skin layer.
::哎哟!你割伤了手指,它开始流血。发生了什么事?如果你的皮肤流血,这意味着你割伤了皮肤层,损坏了血管。伤口真的很痛,因为皮肤层的神经末端而痛。

The dermis also contains hair follicles and two types of glands. You can see some of these structures in  Figure   .
::皮肤还含有毛发泡和两种腺。您可以在图中看到其中的一些结构。

• Hair follicles are structures where hairs originate. Each hair grows out of a follicle. Hair passes up through the epidermis. It then extends above the skin surface.
  ::毛发是毛发发源的结构,每根毛发都从毛发中长出来,头发通过皮皮穿透,然后延伸到皮肤表面。

• Oil glands produce an oily substance. The oil is secreted into hair follicles. Then it makes its way along the hair to the surface of the skin. This oil waterproofs the hair and skin. It helps prevent them from drying out.
  ::油 腺 产生 油状 物质 、 油 藏在 毛囊 中 、 沿着 毛发 到 皮肤 表面 、 防油 、 防油 、 防止 干燥 。

• Another type of gland produces sweat. Sweat contains excess water, salts, and other waste products. Sweat travels up through the layers of the skin to the surface. 
  ::另一类腺产生汗,羊毛含有过量的水、盐类和其他废物,从皮肤的层层流到表面。

Skin Functions
::皮肤外貌函数

You couldn’t survive without your skin. It has many important functions. The main function of the skin is controlling what enters and leaves the body. It prevents the loss of too much water from the body. It also prevents bacteria and other microorganisms from entering the body. 
::没有皮肤就无法生存。 它有许多重要的功能。 皮肤的主要功能是控制进入和离开身体的东西。 它能防止身体中过多的水流失。 它还能防止细菌和其他微生物进入身体。

The skin helps maintain a constant body temperature. It keeps the body cool in two ways. Sweat from sweat glands in the skin evaporates to cool the body. Blood vessels in the skin dilate, or widen. This action increases blood flow to the body surface. This allows more heat to reach the surface. The heat is then able to radiate off the body. The opposite happens to retain body heat. Blood vessels in the skin constrict, or narrow. This decreases blood flow to the body surface. This reduces the amount of heat that reaches the surface. When this happens, less heat can be lost to the air.
::皮肤有助于保持恒定的身体温度。 它以两种方式使身体保持冷却。 皮肤中从汗腺中蒸发, 以冷却身体。 皮肤中的血容器会膨胀, 或扩大。 此动作会增加到身体表面的血流。 这样可以增加到表面的热量。 这样热量就可以从身体中辐射出来。 正好相反, 保持体温。 皮肤收缩或窄小的血容器会保持体温。 这会减少血液流到身体表面的热量。 这样会减少到达表面的热量。 如果发生这种情况, 空气会少点热量。

Lesson Summary
::经验教训摘要

• The skin consists of two distinct layers. The skin has an outer layer called the epidermis and an inner layer called the dermis. The epidermis is constantly being renewed. Dead cells on the surface are shed. This layer produces the pigment that gives skin its color. The dermis contains blood vessels, nerve endings, hair follicles, and oil and sweat glands.
  ::皮肤由两层不同的层组成。 皮肤有外层, 叫做皮层, 内层, 叫做皮层。 皮层不断更新。 表面的死细胞被挖出来。 皮层产生颜色色素。 皮层包括血管、 神经末端、 毛发、 油和汗腺。

• The skin prevents loss of water from the body. It keeps out microorganisms. Blood vessels get bigger and smaller to enable the release of sweat. By doing so, skin helps maintain a constant body temperature.
  ::皮肤防止了身体水的流失,防止了微生物的流失; 血管变大,变小,以释放出汗; 皮肤有助于保持恒定的体温。

Lesson Review Questions
::经验回顾问题

Recall
::回顾

1. Outline how the epidermis is constantly being renewed.
   ::概括一下后皮是如何不断更新的。

1. Identify functions of the skin.
   ::皮肤识别功能 。

1. How do oil glands and sweat glands help us?
   ::油腺和汗腺如何帮助我们?

Apply Concepts
::应用概念

4. Why does it usually hurt to cut the skin but not the hair or nails?
   ::为什么剪伤皮肤却不剪头发或指甲 通常会痛呢?

Think Critically
::仔细仔细思考

5. Compare and contrast the epidermis and dermis.
   ::比较和对比皮皮和皮皮。

Points to Consider
::需要考虑的要点

You can see all the organs of your integumentary system because they cover the outside surface of your body. Most of the organs of your other body systems are hidden inside your body. For example, your skeletal system is completely hidden by your skin and other tissues.
::您可以看到您体内的所有器官, 因为它们覆盖了您身体的外部表面。 您身体中的其他器官大部分隐藏在您身体中。 比如, 您的骨骼系统 完全隐藏在您的皮肤和其他组织中 。

1. What organs do you think make up the skeletal system?
   ::你认为什么器官构成骨骼系统?

1. What are some of the functions of the skeletal system?
   ::骨骼系统的一些功能是什么?