Skin Anatomy and Functions Quiz

Integumentary System - Overview

• The integumentary system is made up of skin, glands, hair, nails, and other structures
• It contacts the external environment, acting as a barrier against the outside world.
• It's the body's largest organ, covering approximately 2 square meters (22 square feet) and weighing 4.5-5 kg (16% of body weight).

Learning Outcomes

• Describe the structure and layers of the skin and its function, including the epidermis, dermis, and subcutaneous layer.
• Describe the supporting layer of the skin.
• Explain the basis for skin color function and variation.
• Describe the structure and functions of the accessory structures of the skin (hair, skin glands, and nails).
• Discuss the function of the skin.

Structure of the Skin

• The skin has three major layers:
  • Epidermis
  • Dermis
  • Subcutaneous layer or hypodermis

Epidermis

• It's the outermost layer of skin and is avascular.

• It's composed of keratinized stratified squamous epithelium.

• It's divided into 4-5 layers:

  • Stratum corneum
  • Stratum lucidum (only in thick skin)
  • Stratum granulosum
  • Stratum spinosum
  • Stratum basale

• Stratum corneum:

  • Most superficial layer.
  • Consists of dead cells (squames).
  • Continuously shed and replaced.
  • Waterproof barrier against light, heat, bacteria, and chemicals.

• Stratum lucidum:

  • Present only in thick skin (e.g., palms and soles).
  • Thin, clear, and translucent layer.
  • Located between the stratum granulosum and stratum corneum.
  • Several rows of flat, dead cells.

• Stratum granulosum:

  • Keratinization begins here.
  • Contains keratin and lamellar granules.

• Stratum spinosum:

  • Layer of 8-10 keratinocytes.
  • Provides strength and flexibility to the skin.
  • Contains dendritic cells to aid immune response.

• Stratum basale:

  • Deepest layer of the epidermis.
  • Close to the basement membrane and blood supply.
  • Contains stem cells for new cell formation.
  • Contains melanocytes & tactile epithelial cells (sensory receptors).
  • Melanocytes produce melanin.

Epidermis (Clinical Applications)

• Dandruff: Excess keratinized cells shed from the scalp.
• Psoriasis: Chronic skin disorder characterized by rapid keratinocyte division and movement through epidermal strata.
• Skin cancer: Prolonged UV exposure can lead to three types:
  • Basal cell carcinoma
  • Squamous cell carcinoma
  • Malignant melanoma
• Skin graft: A patch of healthy skin transferred from a donor site in the same individual, used to replace injured skin.

Dermis -

• Contains: blood vessels, lymphatic vessels, nerves, hair follicles, and glands.
• Functions:
  • Maintains temperature stability.
  • Prevents dehydration.
• It has two regions:
  • Papillary region
  • Reticular region

Dermis (Continued)

• Papillary region:

  • Located just beneath the epidermis.
  • Contains blood vessels, free nerve endings, hair follicles, dermal papillae, and Meissner corpuscles (touch receptors).

• Reticular region:

  • Dense irregular connective tissue.
  • Contains collagen and elastic fibers, adipose cells, hair follicles, sebaceous (oil) glands, and sudoriferous (sweat) glands.
    • Provides strength, extensibility (ability to stretch), and elasticity (ability to return to its normal shape after stretching).

• Clinical Application:

  • Stretch marks (striae):
  • Results from overstretched dermis, causing elastic fiber rupture. Usually associated with pregnancy or obesity.
  • Lines of cleavage: Predominant direction of underlying collagen fibers, useful in minimizing scarring in plastic surgery.
  • Fingerprints: Epidermal ridges reflecting dermal papillae contours.

Subcutaneous Layer (Hypodermis)

• Not part of the skin.
• Attaches the skin to underlying tissues and organs.
• Contains blood vessels and nerves in transit.
  • Lamellated (Pacinian) corpuscles: Nerve receptors that detect pressure applied to the skin.

Subcutaneous Layer - Functions

• Fat storage area for energy reserve.
• Path for blood vessels and nerves.
• Pressure receptor area.
• Cushion: Protecting underlying organs from shocks and injuries.
• Insulation: To maintain body temperature.

Sensory Receptors

• The skin contains various sensory receptors to detect different tactile (touch) sensations.
  • Light touch, pressure, vibration, itch, and tickle.
• Types located superficially:
  • Merkel discs
  • Free nerve endings
  • Meissner corpuscles
• Types located deeply:
  • Pacinian corpuscles

Layers of Skin (Clinical Application)

• Burns: Classify burns based on the depth of tissue damage, leading to different treatments.

Skin Color

• Melanin: Pigment produced by melanocytes in the stratum basale (deepest layer of the epidermis); responsible for most skin color variation. - Exposure to UV light increases melanin production.
• Hemoglobin: Oxygen-carrying pigment in red blood cells; affects skin color, contributing to the pink or red coloration of the skin.
• Carotene: Yellow-orange pigment found in the stratum corneum, dermis, and subcutaneous layer (carrots, egg yolk).

(Skin Color - Clinical Application)

• Freckles: Accumulation of melanin in patches due to exposure to sunlight; a genetic trait.
• Erythema: Skin redness due to capillary engorgement with blood resulting from skin injury, heat, infection, inflammation, or allergic reaction.
• Jaundice: Yellow pigmentation of the skin and whites of the eyes due to bilirubin buildup; often indicates liver problems.
• Pallor: Skin paleness due to low blood flow, a condition associated with shock or anemia.
• Albinism: Congenital absence or partial absence of melanin, which causes changes in hair, skin, and eye color.
• Vitiligo: Chronic skin disorder causing depigmented patches in affected areas due largely to factors coupled with autoimmune disease.
• Nevi (moles): Chronic, benign lesions (non-cancerous growths) of the skin; composed of cells in the epidermis which are melanocytes and typically are non-cancerous.
• Malignant melanoma: A cancerous lesion occurring in the dermis that results from cells within the melanocytes.

Tattooing and Body Piercing

• Tattooing: Permanent coloration of the skin using foreign pigments injected into the dermis.
• Body piercing: Insertion of jewelry through an artificial opening in the skin; potentially causing infection and allergic reactions.

Accessory Structures of the Skin

• Hair: - Shaft - Root - Hair matrix - cells that produce hair - Hair follicle – surrounds hair root - Hair follicle receptor - Arrector pili muscle - Sebaceous and sudoriferous (sweat) glands
  • Nails: Hard, keratinized structures of the epidermis.

Hair (Continued)

• Types:
  • Lanugo: Fine, non-pigmented fetal hair.
  • Vellus: Fine, non-pigmented hair that replaces lanugo after birth and is scattered over the body, not as conspicuous.
  • Terminal: Course, pigmented hair; appearing on the head, eyebrows, lashes, axillary, and pubic areas.
• Functions: - Protection - Thermoregulation - Sensory perception.
• Clinical applications
  • Hair loss (alopecia)
  • Hair removal (electrolysis)
  • Excessive hair growth (hirsutism)
• Hair color:
  • Melanin
    • Gray hair - less melanin production
    • White hair - Air bubbles in hair shaft.
• Hair growth:
  • Growth cycle: Growing stage & resting stage (affected by illness, diet, stress, etc.)

Skin Glands

• Sebaceous glands:
  • Connected to hair follicles
  • Produce sebum (oil);
  • Moistens, waterproofs, softens the skin, inhibits bacterial growth
  • Activity increases at puberty
  • Blockage leads to blackheads and acne
• Sudoriferous (sweat) glands
  • Eccrine sweat glands:
    • Distributed throughout the body
    • Produce watery sweat that regulates body temperature via evaporation.
    • Activated by sympathetic nerves
    • Eliminate urea.
    • Start functioning after birth
  • Apocrine sweat glands:
    • Located in the axilla, groin, and areola
    • Secrete a viscous sweat
    • Not a factor in thermoregulation
    • Start functioning at puberty
    • Involved in body odor due to interaction with bacteria

Ceruminous Glands

• Located in external auditory canal
• Produce cerumen (earwax).
• Provides a sticky barrier that impedes the entrance of foreign bodies and insects.
• Prevents bacteria and fungi from entering.
• Prevents excessive drying via waterproofing the canal.

Clinical Applications - Skin Glands

• Acne: Inflammation of sebaceous glands due to bacteria colonization, overproduction of sebum, and blockage of follicles.

Functions of the Skin

• Regulates body temperature
• Stores blood
• Protects body from external environment
• Detects cutaneous sensations
• Secretes and absorbs substances
• Synthesizes vitamin D

Test your knowledge on the layers of the skin, the functions of various glands, and the anatomy involved in hair growth. This quiz covers essential concepts such as melanin production, sebaceous glands, and the role of different types of hair. Perfect for students in dermatology or those interested in skincare.