Integumentary_System_TEACHER Study_Guide

Integumentary System Overview

Chapter 10 – "Skin Deep"

Layers of the Skin
1. Epidermis

  • Definition: The top layer of skin.

  • Characteristics:

    • Avascular Layer: Lacks blood vessels.

    • Composition: Made up of squamous epithelium.

  • Key Components:

    • Keratin: A protein that provides waterproofing properties to the skin. When epidermal cells die, they fill with keratin.

    • Melanocytes: Cells that produce and contain black pigment, contributing to skin color.

2. Dermis

  • Definition: The middle layer of skin, also known as corium.

  • Characteristics:

    • Contains blood and lymph vessels, nerve fibers, and accessory organs of the skin (glands).

    • Composed of connective tissue.

  • Key Components:

    • Fibroblasts: Cells that produce fibres in the dermal layer.

    • Collagen: A tough and flexible fibrous protein produced by fibroblasts, found not just in skin but also in bone, cartilage, tendons, and ligaments. Acts as a "glue" to hold the body's structures together.

    • Histiocytes: Phagocytic cells that engulf foreign substances; also referred to as macrophages.

    • Mast Cells: Respond to insult by producing and releasing:

    • Histamine: A chemical released in response to allergens, causing itching.

    • Heparin: An anticoagulant chemical released in response to injury, preventing blood clot formation.

    • Sebaceous (Oil) Glands: Secrete sebum, which lubricates the skin.

    • Sudoriferous (Sweat) Glands:

    • Apocrine: Produce and secrete a strong-smelling substance into hair follicles.

    • Eccrine: Produce and secrete water, salt, and waste as sweat.

    • Ceruminous Glands: Modified sweat glands in the ear canal that produce cerumen (earwax).

3. Hypodermis

  • Definition: Also known as the subcutaneous layer, it is the deepest layer of skin.

  • Characteristics:

    • Contains connective tissue.

    • Adipocytes: Cells that form fats, also known as lipids, providing insulation and energy storage.

Parts of the Hair Shaft
1. Cuticle

  • Description: Composed of one cell layer thick; appears scaly.

2. Cortex

  • Description: The main component of the hair shaft.

  • Characteristics:

    • Several cell layers thick.

    • Responsible for determining coat color, as it contains pigment.

3. Medulla

  • Description: The innermost component of the hair shaft.

4. Hair Root

  • Description: The portion of the hair below the skin surface, surrounded by the hair follicle.

5. Follicles

  • Definition: Tubes that hold hair fibers.

  • Characteristics: In the dermis, they expand to form a hair bulb where cells divide rapidly, pushing old cells toward the skin surface, causing them to harden and become pigmented.

6. Arrector Pili

  • Description: A tiny muscle attached to the hair follicle.

  • Function: Causes the hair to stand erect in response to cold temperatures or stress, commonly referred to as "raising hackles."

7. Piloerection

  • Definition: The condition of hair standing straight up, often triggered by environmental factors or emotional responses.