y 發問於 科學及數學生物學 · 1 十年前

primary sexual characteristics

成日講secondary sexual characteristics?咁乜係primary sexual characteristics?

2 個解答

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  • Schan
    Lv 6
    1 十年前
    最愛解答

    Hope this helps you:

    Secondary Sexual Characteristics:

    ==In humans==

    [[Sexual differentiation]] begins during [[gestation]], when the [[gonads]] form. General habitus and shape of body and face, as well as sex hormone levels, are similar in prepubertal boys and girls. As [[puberty]] progresses and sex hormone levels rise, obvious differences appear.

    Male levels of [[testosterone]] directly induce growth of the [[penis]], and indirectly (via [[Dihydrotestosterone|Dihydrotestosterone (DHT)]]) the [[prostate]]. [[Estradiol]] and other hormones cause [[breast]]s to develop in females. However, fetal or neonatal [[androgen]]s may modulate later breast development by reducing the capacity of breast tissue to respond to later estrogen.

    In males, testosterone directly increases size and mass of muscles, vocal cords, and bones, enhancing strength, deepening the voice, and changing the shape of the face and skeleton. Converted into DHT in the skin, it accelerates growth of androgen-responsive facial and body hair. Taller stature is largely a result of later puberty and slower epiphyseal fusion.

    In females, breasts are the most obvious manifestation of higher levels of [[estrogen]], but estrogen also widens the pelvis and increases the amount of body fat in hips, thighs, buttocks, and breasts. Estrogen also induces growth of the [[uterus]], proliferation of the [[endometrium]], and [[menstrual cycle|menses]].

    In humans, secondary sex characteristics include:

    * [[Male]]

    ** [[abdominal hair|abdominal]] and [[chest hair]]

    ** more hair on other parts of body

    ** more [[facial hair]]

    ** on average, larger hands and feet than women

    ** broader shoulders and chest

    ** heavier skull and bone structure

    ** greater [[muscle]] mass and physical strength

    ** a prominent [[Adam's apple]] and deep [[human voice|voice]]

    ** [[fat]] deposits mainly around the [[human abdomen|abdomen]] and [[waist]] (apple shape)

    ** coarser skin texture

    * [[Female]]

    ** enlarged [[breast]]s

    ** on average, lower height than men

    ** wider in [[hip (anatomy)|hip]]s than in [[shoulder]]s

    ** less [[facial hair]]

    ** functional [[mammary gland]]s

    ** more [[subcutaneous fat]]

    ** fat deposits mainly around the [[buttocks]], [[thigh]]s and [[hip (anatomy)|hip]]s (pear shape)

    ** smoother skin texture

    ****************************************************************************

    Primary Sexual Characteristics:

    A sex organ, or primary sexual characteristic, narrowly defined, is any of those anatomical parts of the body (which are not always bodily organs according to the strict definition) which are involved in sexual reproduction and constitute the reproductive system in a complex organism; namely:

    Male: penis (notably the glans penis), prepuce, testicles, scrotum, prostate, seminal vesicles, epididymis, Cowper's glands

    Female: vulva (notably the clitoris and labia), vagina, cervix, uterus, Fallopian tube, ovaries, Skene's gland, Bartholin's glands.

    The Latin term genitalia, sometimes anglicized as genitals, is used to describe the sex organs, and in the English language this term and genital area are most often used to describe the externally visible sex organs, known as primary genitalia or external genitalia: in males the penis and scrotum, in females the vulva.

  • 1 十年前

    Secondary sex characteristics are traits that distinguish the two sexes of a species, but that are not directly part of the reproductive system. Some have argued that in general they evolved to give an individual an advantage over its rivals in courtship. They are opposed to the primary sexual characteristics: the sex organs.

    第二性徵,並非指性器官,而是指辨別出男性或女性的某些生理上的特徵。青春期的少男少女們第二性徵即開始發展,兩性身體儀表逐漸改變。第二性徵和第一性徵所關聯的生殖功能並沒有直接的關係。但是它的出現使男女兩性互相吸引。所以第二性徵是間接的影響生殖作用。

    男性的第二性徵:陰毛出現,於十三歲至十五歲發展成熟;腋下的毛及臉部的汗毛及鬍鬚在十五歲之後開始發展。因為皮下組織增加,皮膚及毛孔變粗,顏色由透明變為粗黃色,皮脂腺功能活躍,與毛囊在同一位置,導致這些腺體功能適應不良,而長出青春痘。腋窩的汗腺開始長大,分泌量亦增多。肌肉發達,臂及腿變粗,肩膀變寬,力量亦增強。身高、體重增加迅速。聲音發生變化,音調至少降低八音度,變成低沈,聲量加強。

    女性的第二性徵:由於骨盤的發育及皮下脂肪增加,使臀部發展為渾圓而且寬大。乳房變大變圓,通常在十歲左右開始發展,大約要過三年乳頭才能外突。陰毛必須在臀部及乳房發展後才會增多。少女們月經初潮之後,腋毛開始出現,腋窩的汗腺增大,腋下汗液較多,皮脂腺發展使少女們也會長青春痘。聲音也起變化,不過沒有男性的聲音變化明顯,肌肉增加快速,肩膀也加寬,比較男性稍不明顯。(沙依仁)

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