Study Notes: The Integumentary System (Anatomy & Physiology)

The Integumentary System

Overview

The integumentary system is composed of the skin and its associated structures, including hair, nails, and glands. It serves as the body's primary barrier against environmental hazards, regulates temperature, and provides sensory information.

Epidermis

Cell Types of the Epidermis

• Keratinocytes: The most abundant cells in the epidermis. They produce keratin, a protein that provides the skin with its protective properties. Keratinocytes originate in the stratum basale and move upwards, becoming more keratinized and eventually dying as they reach the skin surface.

• Melanocytes: Located in the stratum basale, these cells produce melanin, the pigment responsible for skin color. Melanin also protects against UV radiation.

• Dendritic Cells: Found in the stratum spinosum, these cells are part of the immune system. They ingest foreign substances and help activate immune responses.

• Tactile Epithelial Cells (Merkel cells): Found in the stratum basale, these function as sensory receptors for touch.

Cell Junctions: Keratinocytes are tied together by desmosomes for strength and, in some layers, by tight junctions to hinder the movement of water between cells.

Dermis

Layers of the Dermis

• Papillary Layer: Made up of areolar connective tissue.

• Reticular Layer: Made up of dense irregular connective tissue.

Dermal Features

• Friction Ridges: Consist of epidermal ridges that lie on top of dermal ridges. These are responsible for fingerprints and enhance grip by increasing friction.

• Cleavage Lines: Tend to run longitudinally in the skin of the limbs and in circular patterns around the neck and trunk. These lines correspond to the orientation of collagen fibers and are important in surgical procedures.

Hair

Hair Shaft Shape

• Flat and Ribbonlike: Results in curly hair.

• Oval: Produces silky and wavy hair.

• Round: Leads to straight and coarse hair.

Hair Structure

• Medulla: The innermost layer, containing large cells and air spaces. It is the only part with soft keratin.

• Cortex: Surrounds the medulla, consisting of several layers of flattened cells.

• Cuticle: The outermost layer, heavily keratinized, providing strength and preventing matting.

Hair Follicles

• Composed of an inner epithelial root sheath and an outer connective tissue sheath. The hair bulb at the base contains the matrix, which produces hair.

• Arrector Pili Muscle: Attached to each follicle, causing hair to stand upright and creating goosebumps.

Hair Pigment

• Based on melanocytes. The melanocytes at the base of the follicle transfer pigment to cortical cells.

• Different concentrations of melanin determine hair color, ranging from blonde to brown to black.

• Red hair results from a related pigment called pheomelanin.

• Reduced melanin production, combined with air bubbles in the shaft, leads to gray or white hair.

Skin Cancer

Types of Skin Cancer

Type	Origin	Characteristics	Treatment
Basal Cell Carcinoma	Stratum basale cells	Most common, slow growing, rarely metastasizes	Surgical excision (99% cure rate)
Squamous Cell Carcinoma	Keratinocytes of stratum spinosum	Second most common, can metastasize	Removed surgically or treated with radiation
Melanoma	Melanocytes	Most dangerous, highly metastatic, resistant to chemotherapy	Early detection is critical

ABCDE Rule for Melanoma Detection

• Asymmetry (A): One half of the mole or pigmented spot does not match the other half.

• Border (B): The edges are irregular, ragged, or blurred.

• Color (C): The color is not uniform and may include shades of brown, black, tan, and sometimes red or blue.

• Diameter (D): The spot is larger than 6 millimeters (about the size of a pencil eraser).

• Evolving (E): The spot is changing in size, shape, or color.

Note: Early detection is crucial for survival, as melanoma can metastasize quickly. Regular skin checks are recommended.

Burns

Classification of Burns

Degree	Layers Affected	Symptoms	Healing
First-degree	Epidermis	Redness and pain	Heals within days
Second-degree	Epidermis and upper dermis	Blisters, pain	Requires weeks for healing
Third-degree	Full thickness (epidermis and dermis)	Gray-white, cherry red, or blackened skin; no pain (nerve endings destroyed)	Requires grafting and long-term care

Rule of Nines

• A method used to estimate burn extent/damage.

• The body is broken into 11 sections, each representing 9% of body surface area (except the genitals, which account for 1%).

Treatment & Risks

• Severe burns necessitate extra calories and nutrients for recovery.

• Infection is a major concern post-initial crisis, requiring antibiotics.

Additional info:

• Links to further reading on skin cancer prevention and sunscreen use are provided in the original material.

• Clinical applications include recognizing skin cancer warning signs and understanding burn management protocols.