Chapter 6 - Section 6.2 - Study Guide - Assess Your Learning Outcomes - Page 199: 2

Hair can be categorized into various types based on its growth, structure, and function. Three primary kinds of hair, including fetal and adult types, are: 1. **Lanugo Hair (Fetal Hair):** - **Appearance:** Lanugo hair is very fine, soft, and downy. It is usually unpigmented or very lightly pigmented, appearing almost translucent. - **Distribution:** Lanugo hair covers the entire body of a developing fetus, including the face, back, and limbs. - **Function:** Lanugo hair primarily serves as an insulating layer to keep the developing fetus warm in the womb. It also helps to protect the delicate fetal skin from the amniotic fluid. 2. **Vellus Hair (Peach Fuzz):** - **Appearance:** Vellus hair is fine, short, and barely noticeable. It is often referred to as "peach fuzz" due to its soft texture. - **Distribution:** Vellus hair is distributed over most of the body, including the face, arms, and legs. It covers areas where terminal hair (described next) is not present. - **Function:** Vellus hair serves mainly as a thermal insulator and provides a light protective barrier for the skin. It is not involved in temperature regulation to the same extent as terminal hair. 3. **Terminal Hair:** - **Appearance:** Terminal hair is thicker, coarser, and darker than vellus hair. It has a more noticeable pigment and is often longer. - **Distribution:** Terminal hair is found in regions such as the scalp, eyebrows, eyelashes, armpits, pubic area, and on the chest, back, and limbs (in varying degrees). It also includes beard hair in men. - **Function:** The primary function of terminal hair is to provide more substantial protection, sensory functions (e.g., eyelashes protect the eyes), and sometimes sexual dimorphism (e.g., facial hair in men). It also plays a role in regulating body temperature. Throughout a person's life, the type and distribution of hair can change. For example, in childhood, vellus hair may be more prevalent, while during puberty, hormonal changes can lead to the development of terminal hair in various regions, such as the face and pubic area. The presence and characteristics of hair can vary among individuals and are influenced by genetics, hormones, and other factors.

Hair can be categorized into various types based on its growth, structure, and function. Three primary kinds of hair, including fetal and adult types, are: 1. **Lanugo Hair (Fetal Hair):** - **Appearance:** Lanugo hair is very fine, soft, and downy. It is usually unpigmented or very lightly pigmented, appearing almost translucent. - **Distribution:** Lanugo hair covers the entire body of a developing fetus, including the face, back, and limbs. - **Function:** Lanugo hair primarily serves as an insulating layer to keep the developing fetus warm in the womb. It also helps to protect the delicate fetal skin from the amniotic fluid. 2. **Vellus Hair (Peach Fuzz):** - **Appearance:** Vellus hair is fine, short, and barely noticeable. It is often referred to as "peach fuzz" due to its soft texture. - **Distribution:** Vellus hair is distributed over most of the body, including the face, arms, and legs. It covers areas where terminal hair (described next) is not present. - **Function:** Vellus hair serves mainly as a thermal insulator and provides a light protective barrier for the skin. It is not involved in temperature regulation to the same extent as terminal hair. 3. **Terminal Hair:** - **Appearance:** Terminal hair is thicker, coarser, and darker than vellus hair. It has a more noticeable pigment and is often longer. - **Distribution:** Terminal hair is found in regions such as the scalp, eyebrows, eyelashes, armpits, pubic area, and on the chest, back, and limbs (in varying degrees). It also includes beard hair in men. - **Function:** The primary function of terminal hair is to provide more substantial protection, sensory functions (e.g., eyelashes protect the eyes), and sometimes sexual dimorphism (e.g., facial hair in men). It also plays a role in regulating body temperature. Throughout a person's life, the type and distribution of hair can change. For example, in childhood, vellus hair may be more prevalent, while during puberty, hormonal changes can lead to the development of terminal hair in various regions, such as the face and pubic area. The presence and characteristics of hair can vary among individuals and are influenced by genetics, hormones, and other factors.