Chapter 6 - Section 6.2 - Study Guide - Assess Your Learning Outcomes - Page 199: 3

A hair shaft consists of three primary regions from base to tip, as well as three layers from the core to the surface: **Three Regions of a Hair Shaft (Base to Tip):** 1. **Hair Bulb (Hair Root):** - The hair bulb is the base of the hair shaft, located within the hair follicle in the dermis of the skin. - It is the deepest part of the hair, where the hair originates and where it is anchored in the hair follicle. - The hair bulb contains actively dividing cells that produce new hair cells, leading to hair growth. 2. **Hair Shaft (Main Shaft):** - The hair shaft is the middle region of the hair that extends above the surface of the skin. - It is composed of layers of keratinized cells that have lost their nucleus and other organelles. - The hair shaft is the visible part of the hair and can vary in length, thickness, color, and texture depending on factors like genetics and location on the body. 3. **Hair Tip (Distal End):** - The hair tip is the free, pointed end of the hair shaft. - It is the farthest portion of the hair from the hair bulb. - The tip of the hair is often the oldest part and may show signs of wear and damage. **Three Layers of a Hair Shaft (Core to Surface):** 1. **Medulla:** - The medulla is the innermost layer of the hair shaft, and not all hairs have it. - It is composed of loosely packed cells and air spaces. - The presence and characteristics of the medulla can vary among different types of hair, and it may be absent in fine or light-colored hairs. 2. **Cortex:** - The cortex is the middle layer of the hair shaft and is the thickest part. - It contains long, parallel strands of keratin fibers that give the hair its strength, elasticity, and color. - The cortex also contains melanin, which determines the hair's pigmentation. 3. **Cuticle:** - The cuticle is the outermost layer of the hair shaft. - It consists of overlapping, scale-like layers of cells that form a protective barrier around the cortex. - The cuticle helps to protect the inner layers of the hair and plays a crucial role in maintaining the hair's moisture balance and overall health. These regions and layers of a hair shaft is important in various fields, including dermatology, cosmetology, and forensics, as they provide valuable information about hair structure, growth, and potential damage or alterations.

A hair shaft consists of three primary regions from base to tip, as well as three layers from the core to the surface: **Three Regions of a Hair Shaft (Base to Tip):** 1. **Hair Bulb (Hair Root):** - The hair bulb is the base of the hair shaft, located within the hair follicle in the dermis of the skin. - It is the deepest part of the hair, where the hair originates and where it is anchored in the hair follicle. - The hair bulb contains actively dividing cells that produce new hair cells, leading to hair growth. 2. **Hair Shaft (Main Shaft):** - The hair shaft is the middle region of the hair that extends above the surface of the skin. - It is composed of layers of keratinized cells that have lost their nucleus and other organelles. - The hair shaft is the visible part of the hair and can vary in length, thickness, color, and texture depending on factors like genetics and location on the body. 3. **Hair Tip (Distal End):** - The hair tip is the free, pointed end of the hair shaft. - It is the farthest portion of the hair from the hair bulb. - The tip of the hair is often the oldest part and may show signs of wear and damage. **Three Layers of a Hair Shaft (Core to Surface):** 1. **Medulla:** - The medulla is the innermost layer of the hair shaft, and not all hairs have it. - It is composed of loosely packed cells and air spaces. - The presence and characteristics of the medulla can vary among different types of hair, and it may be absent in fine or light-colored hairs. 2. **Cortex:** - The cortex is the middle layer of the hair shaft and is the thickest part. - It contains long, parallel strands of keratin fibers that give the hair its strength, elasticity, and color. - The cortex also contains melanin, which determines the hair's pigmentation. 3. **Cuticle:** - The cuticle is the outermost layer of the hair shaft. - It consists of overlapping, scale-like layers of cells that form a protective barrier around the cortex. - The cuticle helps to protect the inner layers of the hair and plays a crucial role in maintaining the hair's moisture balance and overall health. These regions and layers of a hair shaft is important in various fields, including dermatology, cosmetology, and forensics, as they provide valuable information about hair structure, growth, and potential damage or alterations.