Domain 2.13Anatomy and Physiology

Skin And Subcutaneous Tissue And Common Diseases

Last updated June 16, 2026

Overview

Welcome to your study guide for the Integumentary System (Skin). As a Medical Assistant, you are often the first person to see a patient's skin condition during the intake process.

Why is this critical for your role?

  • Infection Control: Many skin conditions (like Impetigo or Scabies) are highly contagious. Recognizing them immediately helps you protect yourself, the provider, and other patients.
  • Patient Intake: You must be able to describe lesions accurately in the patient's chart using professional terminology (e.g., "macule" instead of "spot").
  • Procedure Preparation: You will assist with procedures like biopsies, suture removals, and wound care.

This guide covers the anatomy of the skin, how to describe what you see, and the specific diseases you need to know for the certification exam.

1. Anatomy of the Integumentary System

The Integumentary system is the largest organ system in the body. Its primary functions are protection (barrier against pathogens), temperature regulation (sweating/shivering), and sensation.

The Three Layers

Layer Description Key Structures & Functions
Epidermis The superficial (outermost) layer. • Avascular (no blood vessels).
• Keratin: A protein that makes skin tough and water-repellent.
• Melanocytes: Produce Melanin, which gives skin its color and protects against UV radiation.
Dermis The "true skin" (middle layer). • Contains blood vessels, nerve endings, hair follicles, and glands.
• Collagen & Elastin: Proteins giving skin strength and flexibility.
Hypodermis (Subcutaneous) The deepest layer. • Composed of Adipose (Fat) and connective tissue.
• Function: Insulation, shock absorption, and anchors skin to underlying muscle.

Glands of the Skin

  1. Sudoriferous Glands: Produce sweat to regulate body temperature.
  2. Sebaceous Glands: Produce sebum (oil) to keep skin soft and prevent bacteria growth. These glands are connected to hair follicles.

Exam Tip: Remember Sebaceous = Sebum (Oil). When these get blocked, it causes Acne.

2. Describing Skin Lesions (Terminology)

You cannot diagnosis a patient, but you must document their physical appearance accurately.

Term Definition Example Condition
Macule Flat, discolored spot on the skin (cannot be felt). Freckle, Flat Mole.
Papule Small, solid, raised bump (can be felt). Pimple, Wart, Insect bite.
Vesicle Small blister containing clear fluid. Chickenpox, Herpes Simplex.
Pustule Elevated lesion containing pus (purulent material). Acne, Impetigo.
Crust Dried blood, serum, or pus (a scab). Healing wound, Impetigo.
Scale Flaking of the skin's surface (dead epidermal cells). Psoriasis, Dandruff.
Fissure Linear crack in the skin extending into the dermis. Athlete's foot, dry heels.
Ulcer Open sore or lesion that extends to the dermis. Decubitus ulcer (bed sore).

3. Common Diseases and Conditions

This section covers the specific conditions required for the exam. You need to know the cause (pathology), what it looks like (signs), and how it is managed.

A. Viral Infections

1. Herpes Dermatitis (Herpes Simplex Virus - HSV-1)

  • Definition: A viral infection caused by HSV-1 (distinct from HSV-2, which is usually genital). primarily affecting the mouth and lips.
  • Signs & Symptoms: Painful vesicles (blisters) on the lips ("cold sores" or "fever blisters"). These vesicles rupture and form a yellow crust.
  • Pathophysiology: The virus lies dormant in the nerve ganglia and reactivates during stress, illness, or sun exposure.
  • Treatment: Antiviral medications (e.g., Acyclovir, Valacyclovir). These shorten outbreaks but do not cure the virus.

2. Herpes Zoster (Shingles)

  • Definition: A painful viral infection caused by the reactivation of the Varicella-Zoster Virus (the same virus that causes Chickenpox).
  • Risk Factors: History of Chickenpox, age > 50, weakened immune system.
  • Signs & Symptoms:
    • Pain, burning, or tingling appears before the rash.
    • A rash of vesicles appears in a band-like pattern on one side of the body (follows a dermatome/nerve path). It does not cross the midline of the body.
  • Treatment: Antiviral medications and pain management.
  • Prevention: The Shingrix vaccine is recommended for adults over 50.

Exam Tip: If a question asks about a painful rash that wraps around one side of the torso, the answer is Herpes Zoster (Shingles).

B. Bacterial Infections

3. Impetigo

  • Definition: A highly contagious superficial bacterial infection, usually caused by Staphylococcus aureus or Streptococcus pyogenes. Common in children.
  • Signs & Symptoms:
    • Red sores, usually around the nose and mouth.
    • The sores rupture and form a characteristic honey-colored crust.
  • Treatment: Topical or oral antibiotics.
  • MA Role: Strict contact precautions. Instruct parents/patients not to share towels or bedding.

4. Cellulitis

  • Definition: An acute, spreading bacterial infection of the dermis and subcutaneous tissues.
  • Signs & Symptoms: The affected area (often the leg) becomes red (erythema), swollen (edema), warm to the touch, and tender. Fever may be present.
  • Risk Factors: Diabetes, breaks in the skin (cracks, insect bites), poor circulation.
  • Treatment: Oral or intravenous (IV) antibiotics. Marking the border of redness with a pen helps track if the infection is spreading or receding.

5. Acne Vulgaris

  • Definition: Chronic inflammation of the sebaceous glands and hair follicles.
  • Pathophysiology: Follicles become plugged with sebum and dead skin cells. Propionibacterium acnes bacteria multiply in the clogged pore.
  • Signs & Symptoms: Comedones (blackheads/whiteheads), papules, pustules, and sometimes nodules/cysts.
  • Treatment: Topical retinoids, benzoyl peroxide, antibiotics (tetracycline), or isotretinoin (Accutane) for severe cases.

C. Parasitic Infestations

6. Scabies

  • Definition: A contagious skin infestation caused by the itch mite (Sarcoptes scabiei).
  • Signs & Symptoms:
    • Intense itching, especially at night.
    • Thin, irregular burrow tracks made up of tiny blisters or bumps on the skin.
    • Common sites: Between fingers, wrists, waist, genitals.
  • Transmission: Prolonged skin-to-skin contact.
  • Treatment: Prescription scabicide cream (Permethrin) applied from the neck down and left on for 8-14 hours. All household members usually need treatment.

7. Pediculosis (Lice)

  • Definition: Infestation with lice (tiny, wingless, blood-sucking insects).
    • Pediculosis capitis: Head lice.
    • Pediculosis corporis: Body lice.
    • Pediculosis pubis: Pubic lice ("crabs").
  • Signs & Symptoms: Intense itching. Visible nits (lice eggs) attached firmly to the hair shaft near the scalp.
  • Treatment: OTC or prescription shampoos (pediculicides). Nits must be removed with a fine-tooth comb.

D. Inflammatory and Chronic Conditions

8. Atopic Dermatitis (Eczema)

  • Definition: A chronic, relapsing inflammatory skin condition. It is often associated with a triad of allergies: Eczema, Asthma, and Hay Fever.
  • Signs & Symptoms: Red, itchy, dry skin. Often called "the itch that rashes" because scratching makes it worse. Common in the creases of elbows and knees.
  • Treatment: Moisturizers (emollients) to repair the skin barrier; topical corticosteroids for flare-ups.

9. Psoriasis

  • Definition: A chronic autoimmune disease that speeds up the growth cycle of skin cells.
  • Signs & Symptoms:
    • Thick, red patches of skin covered with silvery scales (plaques).
    • Most common on elbows, knees, scalp, and lower back.
    • Pitting of the fingernails.
  • Pathophysiology: T-cells attack healthy skin cells by mistake.
  • Treatment: Topical corticosteroids, phototherapy (light therapy), biologic injections.
  • Mnemonic: The S in PSoriasis stands for Silvery Scales.

10. Alopecia

  • Definition: The partial or complete loss of hair where it normally grows.
    • Alopecia Areata: Autoimmune patchy hair loss.
    • Androgenic Alopecia: Male or female pattern baldness (genetic/hormonal).
  • Signs & Symptoms: Round patches of smooth skin without hair (Areata); receding hairline (Androgenic).
  • Treatment: Minoxidil (Rogaine), corticosteroids (for autoimmune types), hair transplant.

Exam Tip: Alopecia = Hair Loss. Think "A-low-pecia" -> The hair level is low.

4. Wounds and Burns

Wound Classifications

  • Abrasion: Superficial scraping of the epidermis (e.g., a "road rash" or skinned knee).
  • Laceration: A deep cut or tear in the skin, often with irregular edges.
  • Puncture: A deep, narrow wound caused by a sharp object (e.g., stepping on a nail). High risk of Tetanus.
  • Contusion: A bruise; bleeding under the skin caused by blunt force trauma. Skin remains intact.

Burn Classifications

You must be able to identify the severity of a burn based on appearance.

Degree Layer Affected Key Symptoms
1st Degree (Superficial) Epidermis only Redness, pain, mild swelling. No blisters. (e.g., Sunburn).
2nd Degree (Partial-thickness) Epidermis + Dermis BLISTERS, intense pain, redness, swelling.
3rd Degree (Full-thickness) All layers + Subcutaneous Waxy, white, or charred/black appearance. No pain (nerve endings destroyed).

5. Clinical Applications for the MA

Diagnostic Tests

  • Culture and Sensitivity (C&S): A swab of a wound or pustule is sent to the lab to identify the bacteria (Culture) and which antibiotic will kill it (Sensitivity).
  • Fungal Scraping (KOH Prep): Skin scales are scraped onto a slide and mixed with Potassium Hydroxide (KOH) to look for fungal spores under a microscope.
  • Allergy Testing: Patch testing applied to the back to identify triggers for contact dermatitis.

Healing Factors

Wound healing is delayed by:

  • Poor Circulation: (e.g., Peripheral Artery Disease).
  • Diabetes: High blood sugar impairs immune function.
  • Smoking: Nicotine constricts blood vessels, reducing oxygen flow to the wound.
  • Infection: Presence of purulent drainage (pus).

6. Final Key Takeaways

  • Honey-Colored Crust = Impetigo.
  • Silvery Scales = Psoriasis.
  • Unilateral (One-sided) Blistering Rash = Herpes Zoster (Shingles).
  • Varicella-Zoster Virus causes both Chickenpox (primary) and Shingles (reactivation).
  • Sebaceous Glands produce oil (sebum); blockage causes Acne.
  • Sudoriferous Glands produce sweat.
  • Scabies involves intense itching at night and burrow tracks.
  • 2nd Degree Burn is characterized by Blisters.
  • Keratin makes skin water-repellent; Melanin provides color/UV protection.
  • Subcutaneous Layer (Hypodermis) contains Adipose (fat) tissue.