Anatomy & Physiology: The Unity of Form and Function, 7th Edition

Published by McGraw-Hill Education
ISBN 10: 0073403717
ISBN 13: 978-0-07340-371-7

Chapter 6 - Section 6.2 - Study Guide - Assess Your Learning Outcomes - Page 199: 5

Answer

A hair follicle is a complex structure with two primary layers: the inner root sheath and the outer root sheath. Additionally, there are specialized nerve endings and smooth muscle associated with the hair follicle. Here's an overview of these components: **1. Inner Root Sheath (IRS):** - **Composition:** The inner root sheath is composed of three layers: - **Henle's Layer:** This is the outermost layer of the inner root sheath. It consists of flattened, keratinized cells. - **Huxley's Layer:** Located beneath Henle's layer, Huxley's layer is also composed of flattened, keratinized cells. - **Cuticle of the IRS:** This is the innermost layer of the inner root sheath and is made up of overlapping scale-like cells. - **Function:** The inner root sheath plays a role in guiding the newly formed hair shaft as it grows from the hair bulb. It surrounds and protects the developing hair. **2. Outer Root Sheath (ORS):** - **Composition:** The outer root sheath is made up of several layers of epithelial cells. - **Function:** The outer root sheath surrounds the inner root sheath and provides structural support to the hair follicle. It helps anchor the follicle in the surrounding skin. **Specialized Nerve Endings Associated with a Hair Follicle:** - **Nerve endings called Merkel cells or Merkel nerve endings** are specialized sensory receptors found in the skin around hair follicles. They are associated with the sense of touch and play a role in detecting pressure and texture. These nerve endings are sensitive to mechanical stimulation and help in sensory perception. **Smooth Muscle Associated with a Hair Follicle:** - **Arrector Pili Muscle:** Each hair follicle is connected to a tiny smooth muscle called the arrector pili muscle. This muscle is attached to the hair follicle on one end and to the dermis of the skin on the other. When this muscle contracts, it causes the hair to stand upright, a phenomenon commonly known as "goosebumps." The contraction of the arrector pili muscle is usually involuntary and can occur in response to various stimuli, such as cold or emotional responses like fear or excitement. In summary, a hair follicle consists of two main layers, the inner root sheath (composed of Henle's layer, Huxley's layer, and the cuticle of the IRS) and the outer root sheath. Specialized nerve endings called Merkel cells are associated with hair follicles and are involved in touch perception. Additionally, the arrector pili muscle, a small smooth muscle, is connected to each hair follicle and controls the hair's position.

Work Step by Step

A hair follicle is a complex structure with two primary layers: the inner root sheath and the outer root sheath. Additionally, there are specialized nerve endings and smooth muscle associated with the hair follicle. Here's an overview of these components: **1. Inner Root Sheath (IRS):** - **Composition:** The inner root sheath is composed of three layers: - **Henle's Layer:** This is the outermost layer of the inner root sheath. It consists of flattened, keratinized cells. - **Huxley's Layer:** Located beneath Henle's layer, Huxley's layer is also composed of flattened, keratinized cells. - **Cuticle of the IRS:** This is the innermost layer of the inner root sheath and is made up of overlapping scale-like cells. - **Function:** The inner root sheath plays a role in guiding the newly formed hair shaft as it grows from the hair bulb. It surrounds and protects the developing hair. **2. Outer Root Sheath (ORS):** - **Composition:** The outer root sheath is made up of several layers of epithelial cells. - **Function:** The outer root sheath surrounds the inner root sheath and provides structural support to the hair follicle. It helps anchor the follicle in the surrounding skin. **Specialized Nerve Endings Associated with a Hair Follicle:** - **Nerve endings called Merkel cells or Merkel nerve endings** are specialized sensory receptors found in the skin around hair follicles. They are associated with the sense of touch and play a role in detecting pressure and texture. These nerve endings are sensitive to mechanical stimulation and help in sensory perception. **Smooth Muscle Associated with a Hair Follicle:** - **Arrector Pili Muscle:** Each hair follicle is connected to a tiny smooth muscle called the arrector pili muscle. This muscle is attached to the hair follicle on one end and to the dermis of the skin on the other. When this muscle contracts, it causes the hair to stand upright, a phenomenon commonly known as "goosebumps." The contraction of the arrector pili muscle is usually involuntary and can occur in response to various stimuli, such as cold or emotional responses like fear or excitement. In summary, a hair follicle consists of two main layers, the inner root sheath (composed of Henle's layer, Huxley's layer, and the cuticle of the IRS) and the outer root sheath. Specialized nerve endings called Merkel cells are associated with hair follicles and are involved in touch perception. Additionally, the arrector pili muscle, a small smooth muscle, is connected to each hair follicle and controls the hair's position.
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