章节大纲

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    Would you believe this is a close-up of your hair and scalp?
    ::你相信这是你头发和头皮的缝合吗?

    Well, maybe not yours. But some other person's. Hair is an integral part of the integumentary system . And although many people may lose some or all of the hair on top of their heads, they still have hair on their arms and legs that perform important functions.
    ::也许不是你的,但其他人的。头发是内脏系统的一部分。虽然许多人头顶上可能掉掉一些或全部头发,但他们的手臂和腿上仍然有毛,可以发挥重要的功能。

    Nails and Hair
    ::指甲和头发

    Nails are made up of specialized epidermal . Fingernails and toenails contain a tough called keratin and are actually a type of modified hair. The nail grows from the nail bed, which is thickened to form a lunula (or little moon), as shown in  Figure . Cells forming the nail bed are linked together to form the nail. There are no nerve endings in the nail.
    ::指甲由专门的上皮瘤组成。指甲和脚趾甲中含有一种硬的、叫做Keratin的发型,实际上是一种改良型的发型。指甲从指甲床长出来,如图所示,指甲床变厚,形成月亮(或小月亮)。指甲床的细胞与钉子相连。指甲没有神经末端。

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    The parts of the nail. The lunula is also called the little moon, and the eponychium is also called the cuticle.
    ::指甲的部分。月球也叫小月亮, 也叫切片。

    The fingernail generally serves two purposes. It serves as a protective plate and enhances sensation of the fingertip. The protection function of the fingernail is commonly known, but the sensation function is equally important. The fingertip has many nerve endings in it, allowing us to receive volumes of information about objects we touch. The nail acts as a counterforce to the fingertip, providing even more sensory input when an object is touched. When your fingertip presses down on an object, the pressure exerted by the solid fingernail provides additional input.
    ::指甲一般有两个目的:作为保护板,提高指尖的感官。指甲的保护功能是众所周知的,但感官功能同样重要。指甲有许多神经末端,可以接收关于我们接触的物体的大量信息。指甲作为指尖的反力,在触摸物体时提供更感官的输入。当指甲压到物体时,坚固的指甲施加的压力提供了额外的输入。

    Nails are made up of many different parts, as shown in Figure :
    ::指甲由许多不同部分组成,如图2所示:

    • The free edge is the part of the nail that extends past the finger, beyond the nail plate.
      ::自由边缘是指甲的部分 指甲伸过指尖 超越指甲板
    • The nail plate is what we think of when we say “nail:” the hard and translucent portion that is composed of keratin.
      ::指甲板是当我们说“钉子 : ” 时我们所想到的。 硬和半透明部分由氯丁烷组成。
    • The lunula is the crescent-shaped, whitish area of the nail bed (when visible).
      ::指甲床是指甲床(当可见时)的新月形的、刻度的角形区域。
    • The eponychium, or cuticle , is the fold of skin at the end of the nail.
      ::或 指甲末端是皮肤的折叠

    Nails grow at a rate of about 1 cm every 100 days. Fingernails require 4 to 6 months to regrow completely, and toenails require 12 to 18 months. Actual growth rate is dependent upon age, season, level, and hereditary factors. This growth record can show the history of recent health and physiological imbalances and has been used as a diagnostic tool since ancient times.
    ::指甲的生长速度每100天大约为1厘米。 指甲需要4至6个月才能完全再生,脚趾甲需要12至18个月。 实际增长率取决于年龄、季节、水平和遗传因素。 这一增长记录可以显示最近的健康和生理失衡的历史,并且从古以来就一直被用作诊断工具。

    Major illness will cause a deep horizontal groove to form in the nails. Discoloration, thinning, thickening, brittleness, splitting, grooves, spots, lines, receded lunula, or changes in the shape of the nail can indicate illness in other areas of the body, nutrient deficiencies, drug reaction or poisoning, or a physical injury to the nail or nail bed.
    ::主要疾病会导致在指甲中形成深横向角角。 涂色、薄化、厚化、易碎、分裂、沟槽、斑点、线条、退缩的指甲或指甲形状的改变可以表明身体其他领域的疾病、营养缺乏、药物反应或中毒,或指甲或指甲床的身体伤害。

    Hair
    ::毛发

    A hair follicle and hair.

    A hair follicle and hair.
    ::毛发和头发

    Hair is a filamentous fiber that is found only on mammals . The main component of hair is the tough protein keratin. Hair emerges from the epidermis , although it grows from hair follicles deep in the dermis , as shown in  Figure . The hair of non-human mammal is commonly called fur.
    ::毛发是一种丝状纤维,只存在于哺乳动物身上。毛发的主要成分是硬质蛋白氯酸盐。毛发从皮皮中出现,尽管发毛是从皮肤深处的毛囊中长出来的,如图所示。非人类哺乳动物的毛发通常被称为毛。

    Humans have three different types of hair:
    ::人类有三种不同的发型:

    • Lanugo is the fine hair that covers nearly the entire body of fetuses .
      ::拉努戈是毛发 几乎覆盖整个胎儿的身体。
    • Vellus hair is the short, fine "peach fuzz" body hair that grows in most places on the except for the palms of the hands and the soles of the feet.
      ::除了手掌和脚底的掌掌之外, 在大部分地方生长的毛发。
    • Terminal hair is the fully developed hair that is generally longer, coarser, thicker, and darker than vellus hair.
      ::发型是完全发育成熟的发型,一般长、粗、厚、暗比维勒斯发型长。

    Different parts of the human body have different types of hair. From childhood onward, vellus hair covers the entire human body except on the lips, the palms of hands, the soles of feet, the navel, and scar tissue . The density of the hairs (in hair follicles per square centimeter) varies from one person to another.
    ::人类身体的不同部分有不同种类的毛发。 从童年起,除嘴唇、手掌、脚底、腹部和疤痕组织外,微风毛覆盖整个人体。 毛发的密度(每平方厘米毛囊)因人而异。

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    Magnification of a human hair. The hair shaft is composed of dead, keratin-filled (keratinized) skin cells that overlap each other like the shingles or tiles on a roof. You can see the overlapping cells in this image.
    ::人体毛发的放大作用。毛发轴由死细胞组成, 填满了氯酸盐的皮肤细胞, 相互重叠, 就像屋顶上的闪烁或瓷砖。 您可以在此图像中看到重叠的细胞 。

    What is the function of hair? In people, hair serves to insulate, protect, and sense the immediate surroundings. Insulation serves to conserve heat. The hair on your head insulates your body from heat loss. Eyelashes and eyebrows protect the from , dirt, and other irritants. Nose hairs act as a physical barrier to any particles or microorganisms that might be in the air we breathe.
    ::头发的功能是什么?在人身上,头发用来隔绝、保护和感知周围环境。绝缘用来保护热量。你的头上的头发可以使身体免受热量流失的伤害。眼睫毛和眉毛可以保护身体不受尘土和其他刺激物的伤害。鼻毛可以作为我们呼吸的空气中任何颗粒或微生物的物理屏障。

    Curly hair has a different biological structure than straight hair, which is shown in  Figure . It tends to be much drier than straight hair because the oils secreted into the hair shaft by the sebaceous glands can more easily travel down the shaft of straight hair. People with very curly hair may find that this hair type can be dry, hard to manage, and often frizzy.
    ::卷发的生理结构与直发不同,如图所示。它往往比直发更干燥,因为被塞巴塞的腺体渗入发道的油更加容易从直发的轴中穿行。 卷发卷发的人可能会发现这种发型可能干燥、难以管理,而且往往会毛骨悚然。

    Individual hairs have periods of growth and dormancy . During the growth portion of the cycle, hair follicles are long and bulbous, and the hair grows out at about a third of a millimeter per day. After three to six months, body hair growth stops (the pubic and armpit areas have the longest growth period). The follicle shrinks, and the root of the hair grows rigid. Following a period of dormancy, another growth cycle starts, and a new hair eventually pushes the old one out of the follicle from beneath. Head hair, by comparison, grows for a long duration and to a great length before being shed. Terminal hair is genetically programmed to be straight, curly, or wavy, and it tends to change over time.
    ::个体毛发有生长期和居住期。 在周期增长期中,毛发毛囊长且发泡,头发每天生长约三分之一毫米。在三到六个月后,身体毛发会停止生长(阴部和毛间生长期最长 ) 。 毛发缩缩缩和毛发根会变得僵硬。 过了一段时间的睡期后,又一个生长周期开始,新的头发最终将旧的毛发从下面推出。 相比之下,头发长长长,在脱胎前长到很长的长度。 末期头发的基因程序是直的、卷毛的或卷毛的,并会随着时间的变化而改变。

    Hair color is the result of pigmentation due to the presence of different forms of melanin . In general, the more melanin present, the darker the hair color; the less melanin present, the lighter the hair color. A person's hair color may also change over time and may be more than one color at a time.
    ::发色是色素的产物,因为有不同形式的美兰素。一般而言,美兰素越多,发色就越暗;美兰素越少,发色就越轻。一个人的发色也会随时间变化,一次可能不止一个颜色。

      

     

    Summary
    ::摘要

    • Nails are made up of specialized epidermal cells. They serve as protective plates and enhance sensation of the fingertips.
      ::指甲由专门的上皮细胞组成,作为保护板,提高指尖的触觉。
    • Hair is a filamentous fiber that is found only on mammals. In people, hair serves to insulate, protect, and sense the immediate surroundings.
      ::毛发是一种丝状纤维,只存在于哺乳动物身上。在人类中,毛发起到隔绝、保护和感知周围环境的作用。

    Review
    ::回顾

    1. What affects the rate of growth for nails?
      ::钉子的增长率受到什么影响?
    2. What are the three types of hair found on humans?
      ::人类身上发现的三种发型是什么?
    3. What is the main component of hair and nails?
      ::毛发和钉子的主要成分是什么?
    4. Describe the growth cycle of hair.
      ::描述毛发生长周期。