Ch.5 The Integumentary System

What is the largest organ of the body?

Skin (~7% of body weight)

Thickness of skin?

1.5–4.4 mm.

What are the layers of the skin?

Epidermis (outer), Dermis (inner), Hypodermis (deep, areolar & adipose tissue; not technically skin).

Main functions of the skin?

Protection, temperature regulation, excretion, vitamin D production, sensory reception.

Function of melanocytes?

Basal layer; secrete melanin (pigment).

Function of tactile (Merkel) cells?

Basal layer; touch receptors connected to nerves.

Function of dendritic (Langerhans) cells?

Stratum spinosum; immune defense, transport antigens.

Stratum basale?

Melanocytes + tactile cells.

Stratum spinosum?

Spiny appearance; dendritic cells present.

Stratum granulosum?

Waterproofing glycolipids; cells too far from blood supply.

Stratum lucidum?

Only in thick skin (palms, soles).

Stratum corneum?

Thick, dead keratinocytes; provides protection.

Is epidermis vascular?

No, it’s avascular but innervated.

Two layers of dermis?

Papillary → dermal papillae & ridges (fingerprints, grip).
Reticular → dense irregular CT, 80% of dermis, vascular plexuses regulate temperature.

Special features of dermis?

Cleavage lines (collagen separation) and flexure lines (palms, wrists, soles, fingers, toes).

Function of hypodermis?

Connects skin to underlying structures, insulation, fat storage.

Does fat distribution differ by sex?

Yes, males vs. females.

Main pigments in skin?

Melanin (from tyrosine), carotene (yellow/orange), hemoglobin (pink tone in low melanin).

Nails?

Hard keratin, modification of epidermis.

Hair?

Dead keratinized cells; root (in skin) vs. shaft (above skin).

Hair follicle features?

Extends into dermis, contains bulb & root plexus (sensory nerves).

Sebaceous glands?

Secrete sebum (oil); lubricates skin/hair; holocrine secretion.

Types of sweat glands?

Eccrine → true sweat, most numerous; Apocrine → axillary, anal, genital; musky odor (pheromone-like); Modified → ceruminous (earwax), mammary (milk).

1st degree burn?

Only epidermis affected.

2nd degree burn?

Epidermis + upper dermis; blisters form.

3rd degree burn?

Full thickness destroyed; skin appears white/red/black.

Basal cell carcinoma?

Most common, least malignant.

Squamous cell carcinoma?

From stratum spinosum keratinocytes.

Melanoma?

Most dangerous; originates from melanocytes.

ABCDE rule for melanoma?

A – Asymmetry, B – Border irregularity, C – Color variation, D – Diameter >6 mm, E – Evolving (changes).

Fetal skin features?

Lanugo (fine hair), vernix caseosa (sebaceous secretion).

Aging skin features?

Thinner, less elastic, more damage, common inflammations.