4.5 毛发
章节大纲
-
Fashion Statement
::时时声明This blue and green spikey hairstyle makes quite a fashion statement. Many people spend a lot of time and money on their hair, even if they don’t have an exceptional hairstyle like this one. Besides its display value, hair actually has important physiological functions.
::这种蓝色和绿色的刺青发型在时尚方面做了相当可观的陈述。 许多人花很多时间和金钱在头发上,即使他们没有像这般的特殊的发型。 除了显示价值外,头发实际上还有重要的生理功能。What is Hair?
::头发是什么?Hair is a filament that grows from a hair follicle in the dermis of the skin. It consists mainly of tightly packed, keratin-filled called keratinocytes . The is covered with hair follicles, with the exception of a few areas, including the mucous membranes, lips, palms of the hands, and soles of the feet.
::毛发是一种丝状的丝状纤维,从皮肤皮质的毛囊中长出来,主要由紧身包扎的、填满氯酸盐的乳腺细胞组成,上面盖有毛囊,只有少数地区除外,包括粘膜、嘴唇、手掌和脚底。Structure of Hair
::毛发结构结构The part of the hair located within the follicle is called the hair root. The root is the only living part of the hair. The part of the hair that is visible above the surface of the skin is the hair shaft. The shaft of the hair has no biochemical activity and is considered dead.
::毛发部位在毛发管中,毛发部位被称为毛根。根部是毛发中唯一活的部位。毛发部位在皮肤表面上可以看到的部分是毛管。毛发管没有生化活性,被视为已死亡。Follicle and Root
::玻璃和根Hair growth begins inside a follicle (see the figure ). Each hair follicle contains cells that can keep dividing, which allows hair to grow. The stem cells can also regrow a new hair after one falls out. Another structure associated with a hair follicle is a sebaceous gland that produces oily sebum . The sebum lubricates and helps to waterproof the hair. A tiny arrector pili muscle is also attached to the follicle. When it contracts, the follicle moves, and the hair in the follicle stands up.
::毛发生长开始于毛囊内(见图 ) 。 每个毛发囊中含有可以保持分裂的细胞, 允许头发生长。 干细胞也可以在头发掉出来后再长出新的头发。 与毛发囊相关的另一结构是产生油性精液的细毛状腺。 纤维润滑剂和帮助为毛毛防水。 微小的气压肌肉也附在卵囊上。 当它收缩时, 卵泡运动, 以及毛发在卵囊中站立起来 。A hair follicle has a sebaceous gland and an arrector pili muscle.
::毛发毛囊长有沙发状腺 和肌肉Shaft
::遮盖The hair shaft is a hard filament that may grow very long. Hair normally grows in length by about half an inch a month. In cross-section, a hair shaft can be divided into three zones, called the cuticle , cortex, and medulla.
::发道是一条长长的硬丝。 头发通常每月长约半英寸。 在交叉切口中, 发道可以分为三个区, 叫做切口、 皮层 和 medula 。-
The
cuticle
(or outer coat) is the outermost zone of the hair shaft. It consists of several layers of flat, thin keratinocytes that overlap one another like shingles on a roof. This arrangement helps the cuticle repel
. The cuticle is also covered with a layer of
, just one molecule thick, which increases its ability to repel water. This is the zone of the hair shaft that is visible to the eye.
::切片(或外衣)是毛发管的最外部区域,由几层平坦、薄的乳腺细胞组成,它们相互重叠,如屋顶上闪烁。这种安排有助于切片反射。切片还被一层,只有一个分子厚的层覆盖,这增加了其排水能力。这是眼中可见的毛管区域。 -
The
cortex
is the middle zone of the hair shaft, and it is also the widest part. The cortex is highly structured and organized, consisting of
keratin
bundles in rod-like structures. These structures give hair its mechanical strength. The cortex also contains
melanin
, which gives hair its color.
::皮层是毛发轴的中间部分,也是最宽的部分。皮层结构严密,组织严密,由棒状结构中的氯拉丁捆包组成。这些结构使毛发具有机械强度。皮层还含有梅兰尼,它有毛发的颜色。 -
The
medulla
is the innermost zone of the hair shaft. This is a small, disorganized, and more open area at the center of the hair shaft. The medulla is not always present. When it is present, it contains highly pigmented cells full of keratin.
::发道最深处是发道的最深处。 这是一个小的、组织松散的、更开放的发道中心区域。 发道中心并不总有中风。 当它出现时, 它含有高色细胞, 充斥着氯硝酸盐。
Characteristics of Hair
::毛发的特征Two visible characteristics of hair are its color and texture. In adult males, the extent of balding is another visible characteristic. All three characteristics are genetically controlled.
::毛发的两个明显特征是颜色和质地。在成年男性中,秃头的程度是另一个明显的特征。所有这三个特征都受到基因控制。Hair Color
::毛发颜色All natural hair colors are the result of melanin , which is produced in hair follicles and packed into granules in the hair. Two forms of melanin are found in human hair: eumelanin and pheomelanin. Eumelanin is the dominant pigment in brown hair and black hair, and pheomelanin is the dominant pigment in red hair, as you can see pictured . Blond hair results when you have only a small amount of melanin in the hair. Gray and white hair occur when melanin production slows down, and eventually stops.
::所有天然的毛发颜色都是美兰素的产物,它以毛发毛囊制成,并装在毛发中的颗粒中,在人的头发中发现了两种形式的美兰素:eumelain和pheomelanin。欧梅兰宁是棕色头发和黑发中的主要色素,而黄麻宁是红发中的主要色素,正如你可以看到的。在头发中只有少量的美兰素时,金发的结果就会是。在梅兰尼生产减速并最终停止时,灰白的和灰色的头发就会出现。Naturally red hair gets its color mainly from the pigment pheomelanin.
::自然红头发的颜色 主要是色素黄蜂的颜色Hair Texture
::毛发质Hair exists in a variety of textures. The main aspects of hair texture are the curl pattern, thickness, and consistency.
::毛发存在于各种纹理中,毛发纹理的主要方面是卷曲、厚度和一致性。-
The shape of the hair follicle determines the shape of the hair shaft. The shape of the hair shaft, in turn, determines the curl pattern of the hair. Round hair shafts produce straight hair. Hair shafts that are oval or have other shapes produce wavy or curly hair (pictured
).
::毛发囊的形状决定毛发管的形状。 毛发轴的形状反过来决定毛发卷曲模式。 圆发轴产生直发。 毛发轴是奥瓦尔形的, 或有其他形状的毛发产生卷状或卷发( 图画 ) 。 -
The size of the hair follicle determines the thickness of hair. Thicker hair has greater volume than thinner hair.
::毛囊的大小决定毛发的厚度。 -
The consistency of hair is determined by the hair follicle volume and the condition of the hair shaft. The consistency of hair is generally classified as fine, medium, or coarse. Fine hair has the smallest circumference, and coarse hair has the largest circumference. Medium hair falls in between these two extremes. Coarse hair also has a more open cuticle than thin or medium hair does,
which causes
it to be more porous.
::毛发的稳定性取决于毛发卷卷的体积和毛发管的状况。毛发的稳定性一般被归类为细、中或粗糙。毛发的宽度最小,毛发的宽度最大。中度头发介于这两个极端之间。毛发的开阔性也比薄或中度头发的开阔性要强,这导致毛发的松散性更大。
Curly hair has a differently shaped shaft than straight hair.
::卷发的形状跟直发不一样Functions of Hair
::毛毛的函数In humans, one function of head hair is to provide insulation and help the head retain heat. Head hair also protects the skin on the head from damage by UV light.
::在人体中,头发的一个功能是提供绝缘和帮助头部保持热量。头发还保护头部的皮肤免受紫外光的破坏。The function of hair in other locations on the body is debated. One idea is that body hair helps keep us warm in cold weather . When the body is too cold, arrector pili contract and cause hairs to stand up, trapping a layer of warm air above the epidermis . However, this is more effective in mammals that have thick hair or fur than it is in relatively hairless human beings.
::身体上其它地方的毛发功能是辩论的。 一种想法是身体毛在寒冷的天气中能让我们保持温暖。 当身体太冷时, 气管皮质会让毛发起立, 将一层温暖的空气困在皮层之上。 但是,在毛厚或毛皮相对不毛的哺乳动物中,这比在相对没有毛的人中更有效。Human hair has an important sensory function, as well. Sensory receptors in the hair follicles can sense when the hair moves, whether it moves because of a breeze, or because of the touch of a physical object. The receptors may also provide sensory awareness of the presence of parasites on the skin.
::人体发型也具有重要的感官功能。 毛发泡中的感应受体在发型移动时可以感知到,无论发型是因风而动,还是因身体物体的触碰而动。 受体也可以提供对皮肤上寄生虫存在的感应意识。Some hairs — such as the eyelashes — are especially sensitive to the presence of potentially harmful matter. The eyelashes grow at the edge of the eyelid and can sense when dirt, dust, or another potentially harmful object is too close to the eye. The eye reflexively closes as a result of this sensation. The eyebrows also provide some protection to the . They protect the eyes from dirt, sweat, and rain. In addition, the eyebrows play a key role in nonverbal (see the photo ). They help express emotions such as sadness, anger, surprise, and excitement.
::有些毛发,如眼睫毛,对潜在有害物质的存在特别敏感,眼睫毛在眼皮边缘长,当泥土、灰尘或其他潜在有害物体离眼睛太近时,可以感觉到,眼睛由于这种感觉而反射关闭,眉毛也为眼睛提供某种保护,保护眼睛免受泥土、汗水和雨雨的影响,眉毛在非语言中起着关键作用(见照片),有助于表达悲伤、愤怒、惊喜和兴奋等情绪。This young child is using his eyebrows to good effect to convey his displeasure.
::这个小孩子用眉毛来表达他的不满。Hair in Human Evolution
::人类进化中的毛发Among mammals, humans are nearly unique in having undergone significant loss of body hair during their evolution. Humans are also unlike most other mammals in having curly hair as one variation in hair texture. Even non-human (see the photo ) all have straight hair. This suggests that curly hair evolved at some point during human evolution.
::在哺乳动物中,人类在进化过程中的毛发大量丧失,这几乎是独一无二的。 与其他大多数哺乳动物不同,人类的卷发是发质的一种变异。 即使是非人类(见照片 ) , 也都有直发。 这表明卷发在进化过程中的某个时刻会演变。Like other non-human primates, this tamarin monkey has straight hair.
::像其他非人类灵长类动物一样, 这只塔马林猴子有直发。Loss of Body Hair
::身体毛毛损失One hypothesis for the loss of body hair in the human lineage is that it would have facilitated cooling of the body by the evaporation of sweat. Humans also evolved far more sweat glands than other mammals, which is consistent with this hypothesis, because sweat evaporates more quickly from less hairy skin. Another hypothesis for human hair loss is that it would have led to fewer parasites on the skin. This might have been especially important when humans started living together in larger, more crowded social groups.
::人类家族中丧失毛发的一个假设是,它会通过汗水蒸发促进身体冷却。 人类也比其他哺乳动物进化得更多,这与这一假设是一致的,因为汗水从毛发较少的皮肤中蒸发得更快。 另一种人类毛发损失的假设是,它会导致皮肤寄生虫减少。 当人类开始生活在更大、更拥挤的社会群体中时,这一点可能尤其重要。These hypotheses may explain why we lost body hair, but they can’t explain why we didn’t also lose head hair and hair in the pubic region and armpits. It is possible that head hair was retained because it protected the scalp from UV light. As our bipedal ancestors walked on the open savannas of equatorial Africa, the skin on the head would have been an area exposed to the most direct rays of sunlight in an upright hominid. Pubic and armpit hair may have been retained because they served as signs of sexual maturity, which would have been important for successful mating and .
::这些假设或许可以解释我们为什么失去了头发,但无法解释为什么我们没有同时在阴部和毛皮中失去头发和头发。 头发之所以被保留,可能是因为它保护头皮免受紫外光照射。 当我们的双峰祖先在赤道非洲开阔的热带草原上行走时,头部的皮肤本来会暴露在光线最直接的光线下,一个直立的幽灵中。 紫外和毛发可能保留下来,因为它们是性成熟的迹象,这对成功交配和交配很重要。Evolution of Curly Hair
::卷毛的演变Greater protection from UV light has also been posited as a possible selective agent favoring the evolution of curly hair. Researchers have found that straight hair allows more light to pass into the body through the hair shaft via the follicle than does curly hair. In this way, human hair is like a fiber optic cable. It allows light to pass through easily when it is straight, but it impedes the passage of light when it is kinked or coiled. This is indirect evidence that UV light may have been a selective agent leading to the evolution of curly hair.
::防止紫外线光线的更大保护也被假定为有利于卷发进化的一种可能的选择性诱因。 研究人员发现,直发比卷发通过卷发管通过卷发管进入身体的亮度要高。 这样,人的头发就像一条光纤电缆。 它让光线在直线时很容易穿透,但当光线被抚动或缠绕时,它会阻碍光的通过。 这是间接的证据,表明紫外线可能是导致卷发进化的选择性诱因。Social and Cultural Significance of Hair
::毛发的社会和文化意义Hair has great social significance for human beings. Body hair is an indicator of biological sex, because hair distribution is sexually dimorphic. Adult males are generally hairier than adult females, and facial hair in particular is a notable secondary male sex characteristic. Hair may also be an indicator of age. White hair is a sign of older age in both males and females, and male pattern baldness is a sign of older age in males. In addition, hair color and texture can be a sign of ethnic ancestry.
::毛发对人类具有重大的社会意义。身体毛发是生理性的一个指标,因为毛发分布是性畸形的。成年男性一般比成年女性长,面部毛是男性的次要性特征。毛发也可能是年龄的一个指标。白发是男性和女性年龄较大的标志,男性秃头是男性年龄较大的标志。此外,毛发颜色和纹理也可能是民族血统的标志。Hair also has great cultural significance. Hairstyle may be an indicator of social group membership. For example, long stylized bangs were very common for “emos” of all genders in the 2000s and early 2010s. Head shaving has been used in many times and places as a punishment, especially for women. On the other hand, in some cultures, cutting off one’s hair symbolizes liberation from one’s past. In other cultures, it is a sign of mourning. There are also many religious-based practices involving hair. For example, the majority of Muslim women hide their hair with a headscarf. Sikh men grow their hair long and cover it with a turban. Amish men (like the one pictured ) grow facial hair only after they marry — but just a beard, and not a mustache.
::头发也具有巨大的文化意义。 发型可能是社会团体成员的一个标志。 比如,2000年代和2010年代初期,所有性别的“化身”都非常常见长期僵化的爆炸。 头剃头在很多时候和场所都被用作惩罚手段,尤其是女性。 另一方面,在某些文化中,割掉头发象征着从过去解放出来。 在其他文化中,它是一种哀悼的象征。 也有许多宗教习俗涉及头发。 比如,大多数穆斯林妇女用头巾遮住头发。 锡克族男子长头发,用头巾遮住头发。 美男子(像一幅图片一样 ) 只有在结婚后才能长出面部毛发 — — 但只是胡子,而不是胡子。This style of facial hair is adopted by most Amish men after they marry.
::大部分阿米什人结婚后都采用这种面部毛发的风格。Summary
::摘要-
Hair is a filament that grows from a hair follicle in the dermis of the skin. It consists mainly of tightly packed, keratin-filled cells called keratinocytes. The human body is almost completely covered with hair follicles.
::毛发是一种丝状纤维,从皮肤皮肤皮质的毛发囊中长出来,主要由紧凑的、填满氯酸盐的细胞组成,称为乳腺细胞,人体几乎完全被毛发囊覆盖。 -
The part of a hair that is within the follicle is the hair root. This is the only living part of a hair. The part of a hair that is visible above the skin surface is the hair shaft. It consists of dead cells.
::毛发在毛发囊中的部分是毛根。 这是毛发中唯一活的部分。 在皮肤表面上方可见的毛发部分是毛管, 它由死细胞组成 。 -
Hair growth begins inside a follicle when stem cells within the follicle divide to produce new keratinocytes. An individual hair may grow to be very long.
::毛发的生长始于卵块内部,因为卵块分裂中的干细胞会产生新的乳腺细胞。 单发可能长得非常长。 -
A hair shaft has three zones: the outermost zone called the cuticle; the middle zone called the cortex; and the innermost zone called the medulla.
::发道有三个区域:最外边称为切口的区域;中间称为皮层的区域;最内端称为中层的区域。 -
Genetically controlled, visible characteristics of hair include hair color, hair texture, and the extent of balding in adult males. Melanin (eumelanin and/or pheomelanin) is the pigment that gives hair its color. Aspects of hair texture include curl pattern, thickness, and consistency.
::毛发的遗传、可见特征包括毛发颜色、毛质和成年男性秃头的程度。梅拉宁(eumelainin和/或phemelainin)是发色的色素。毛质的各个方面包括卷发、厚度和一致性。 -
Functions of head hair include providing insulation and protecting skin on the head from UV light. Hair everywhere on the body has an important sensory function. Hair in eyelashes and eyebrows protects the eyes from dust, dirt, sweat, and other potentially harmful substances. The eyebrows also play a role in nonverbal communication.
::头毛的功能包括提供绝缘,保护头部的皮肤不受紫外光照射。 身体上任何地方的毛都有重要的感官功能。 眉毛和眉毛可以保护眼睛免受灰尘、泥土、汗水和其他潜在有害物质的伤害。 眉毛在非语言交流中也有作用。 -
Among mammals, humans are nearly unique in having undergone significant loss of body hair during their evolution, probably because sweat evaporates more quickly from less hairy skin. Curly hair also is thought to have evolved at some point during human evolution, perhaps because it provided better protection from UV light.
::在哺乳动物中,人类在进化过程中出现大量毛发流失,这几乎是独一无二的,原因可能是汗水从毛皮较少的皮肤中蒸发得更快。 卷发也被认为在人类进化过程中的某个时刻有所演变,或许是因为它提供了更好的保护,使其免受紫外光的影响。 -
Hair has social significance for human beings,
because it is
an indicator of biological sex, age, and ethnic ancestry. Human hair also has cultural significance.
H
airstyle may be an indicator of social group membership, for example.
::头发对人类具有社会意义,因为它是生物性别、年龄和种族血统的指标,人的头发也具有文化意义,例如,发型可能是社会群体成员的指标。
Review
::回顾1. Compare and contrast the hair root and hair shaft.
::1. 比较和对比发根和发道。2. Describe hair follicles.
::2. 描述毛细。3. Identify the three zones of a hair shaft.
::3. 标明毛管的三个区。4. Explain variation in human hair color.
::4. 解释人类发色的变异。5. What factors determine the texture of hair?
::5. 何种因素决定头发的纹理?6. Describe two functions of human hair.
::6. 描述人类头发的两个功能。7. What hypotheses have been proposed for the loss of body hair during human evolution?
::7. 对于人类进化过程中人体毛发的丧失提出了哪些假设?8. Discuss the social and cultural significance of human hair.
::8. 讨论人类头发的社会和文化意义。9. Describe one way in which hair can be used as a method of communication in humans.
::9. 说明可将头发用作人类交流方法的一种方式。10. Explain why people don't have hair on the palms of their hands, but can have hair on the backs of their hands.
::10. 解释为什么人们手掌上没有毛,但可以手背有毛。11. Explain why waxing or tweezing body hair — which typically removes hair down to the root — generally keeps the skin hair-free for a longer period of time than shaving, which cuts hair off at the surface of the skin.
::11. 解释为什么通常将头发脱到根部的毛发打蜡或理发,通常比剃毛在皮肤表面剪掉毛的剃须,在较长的时间内保持皮肤无毛。12. True or False: Eyelashes can have a sensory function.
::12. 真实或虚假:眼睫毛可产生感官功能。13. True or False: Blond hair differs from brown hair primarily because it has a different kind of melanin.
::13. 真实或假:棕色头发与棕色头发不同,主要是因为棕色头发有不同种类的梅兰宁。14. Curly hair ____________________.
::14. 卷发a. comes from round follicles
::a. 来自圆柱体b. often has an oval shaft
::b. 经常有一个oval井c. protects against damage from UV light
::c. 防止受到紫外光的损害d. B and C
::d. B和C15. Hair consists mainly of _______________________.
::15. 毛发主要由____________________ 组成。a. melanocytes
::a. 脑膜炎b. keratinocytes
::b. 中子二亚二氮细胞c. epidermocytes
::c. 皮下细胞d. hirocytes
::d. 高细胞管Explore More
::探索更多Do you wonder what causes male pattern baldness? Watch this short video to find out.
::你想知道是什么导致男性秃头吗?T wo to four percent of the population suffers from trichotill o mania, or hair pulling syndrome. Learn more here:
::2%至4%的人口患有三氯硝基苯甲醚或拉发综合症。 -
The
cuticle
(or outer coat) is the outermost zone of the hair shaft. It consists of several layers of flat, thin keratinocytes that overlap one another like shingles on a roof. This arrangement helps the cuticle repel
. The cuticle is also covered with a layer of
, just one molecule thick, which increases its ability to repel water. This is the zone of the hair shaft that is visible to the eye.
