the skin

What are the two main layers of the skin?

The epidermis and the dermis.

What lies beneath the dermis and is not considered part of the skin?

The subcutaneous layer (hypodermis), composed of areolar and adipose connective tissue.

What are the main components of the skin system?

Skin, nails, hair, sweat glands, sebaceous glands

what are the layers of the skin from deepest to outermost

1. Stratum Basale (Basal Layer)

2. Stratum Spinosum (Spiny Layer)

3. Stratum Granulosum (Granular Layer)

4. Stratum Lucidum (Clear Layer) – Only in thick skin

5. Stratum Corneum (Horny Layer)

Stratum Basale

• Contains keratinocytes that continuously divide to produce new cells.

• Contains melanocytes, which produce the pigment melanin.

• Contains Merkel cells, which are involved in touch sensation.

• Cells in this layer are mitotically active, ensuring constant renewal of the epidermis.

Stratum spinosum

• contains several layers of keratinocytes and dendritic cells

• Provides strength and flexibility to the skin.

Stratum Granulosum

• A thin layer of flattened keratinocytes containing dark-staining granules

stratum lucidum

• A thin, translucent layer found only in thick skin (e.g., palms of hands and soles of feet). It provides protection.

Stratum corneum

• The outermost layer of the epidermis, composed of dead, flattened keratinocytes called corneocytes.

• Forms a protective barrier against environmental damage, pathogens, and water loss.

What is the difference between thick and thin skin?

Thick skin has all five epidermal layers and no hair follicles or sebaceous glands, while thin skin lacks the stratum lucidum and contains hair follicles and sebaceous glands.

What are the two layers of the dermis?

The papillary layer and the reticular layer

What type of connective tissue is in the papillary layer

Areolar connective tissue

What does the reticular layer contain?

Dense irregular connective tissue, hair follicles, sebaceous glands, sweat glands, nerves, and blood vessels.

Name four key functions of the skin

Thermoregulation, protection, sensation, water balance

How does the skin contribute to vitamin D synthesis?

UV light converts 7-dehydrocholesterol into vitamin D3, which is later converted to its active form

How does the skin protect against microbes and toxins?

It acts as a physical barrier, with keratinized cells and immune cells (Langerhans cells).

What are the two types of sweat glands?

Eccrine and apocrine glands

Where are eccrine sweat glands most common, and what do they do?

Found all over the body, especially on palms and soles; they help with thermoregulation.

Where are apocrine glands found, and when do they become active?

Found in the axillae, groin, and genital areas; become active at puberty

What is the function of sebaceous glands

They secrete sebum, which lubricates and waterproofs the skin

What is the function of the arrector pili muscle?

Causes hair to stand up (goosebumps) in response to cold or fear

What part of the hair contains actively dividing cells

The hair matrix.

What are nails derived from?

keratin

What role do dermal blood vessels play in thermoregulation

They constrict to retain heat and dilate to release heat

What are Meissner’s corpuscles sensitive to?

Light pressure and low-frequency vibration

What do Pacinian corpuscles detect?

Deep pressure and high-frequency vibration

What are the four stages of wound healing

• Haemostasis – Cut blood vessels bleed into the wound, introducing clotting factors and immune cells.

• Inflammation – Blood clot forms, leukocytes clean the wound.

• Proliferation – Blood vessels regrow, and granulation tissue forms.

• Remodelling – Epithelium regenerates, and connective tissue fibrosis occurs.

What is granulation tissue?

Vascular connective tissue that forms deep in a wound to support healing

What is the primary factor that determines skin tone?

Melanin production

How does melanin protect the skin?

It absorbs UV radiation and reduces DNA damage

What are the effects of sunburn on the skin?

• Redness, pain, itching, mild edema (first-degree burn).

• Blistering and more severe pain if it reaches the dermis (second-degree burn).

What does chronic UV exposure lead to?

Accelerated skin aging and increased skin cancer risk

What are the ABCDE signs of melanoma

• Asymmetry – Uneven shape.

• Border – Irregular, notched edges.

• Color – Uneven pigmentation.

• Diameter – Larger than 6mm.

• Evolving – Changes in size, shape, or symptoms

Why are babies more prone to temperature issues?

• Less active sebaceous glands → Prone to dry skin.

• High body surface area → More heat loss (hypothermia).

• Immature sweat glands → Poor heat dissipation (hyperthermia).

What changes occur in skin during puberty?

• Increased sebaceous gland activity → Oily skin.

• Activation of apocrine sweat glands → Body odour.

• Development of coarser hair

How does aging affect skin

• Thinner epidermis → Less protection.

• Reduced collagen & elastin → Wrinkles.

• Decreased sebaceous gland activity → Dry, cracked skin.

• Decreased vitamin D production.