The Integument Overview of the Integumentary System Organization

The Integument

Overview of the Integumentary System

Organization of the Epidermis: Figure 5– 2

Layers of the epidermis are known as “strata”

Layers of the Epidermis Top: Free surface of skin - stratum corneum - stratum lucidum - stratum granulosum - stratum spinosum - stratum germinativum Bottom: Basal lamina

A note on thick vs. thin skin • Thick skin has an extra layer (lucidum) but that is NOT the reason that it is thicker than thin skin. • Real reason is the other layers are thicker in thick skin than in thin skin.

The Dermis • Deeper part of cutaneous layer • Located between epidermis and subcutaneous layer • Anchors epidermal accessory structures (hair follicles, sweat glands) • Has 2 components: – outer papillary layer – deep reticular layer

The Papillary Layer • Consists of areolar tissue • Contains smaller capillaries, lymphatic vessels, and sensory neurons • Has dermal papillae projecting between epidermal ridges

The Reticular Layer • Consists of dense irregular connective tissue • Contains larger blood vessels, lymph vessels, and nerve fibers • Contains collagen and elastic fibers

Integumentary Accessory Structures • Hair, hair follicles, sebaceous (oil) glands, sweat glands, and nails: – are derived from embryonic epidermis – are located in dermis – project through the skin surface

The Hair Follicle • Is located deep in dermis • Is made of epidermal tissue (with connective tissue around the outside) • Produces nonliving hairs • Is wrapped in a dense connective-tissue sheath • Base is surrounded by sensory nerves

Hair

Structures of Hair and Follicles Figure 5– 9 a

Accessory Structures of Hair • Arrector pili: – involuntary smooth muscle – causes hairs to stand up – produces “goose bumps” • Sebaceous glands: – lubricate the hair – control bacteria

Inside the Follicle Figure 5– 9 b

Exocrine Glands in the skin • Sebaceous glands and follicles (oil glands): – holocrine glands – secrete sebum • Sweat glands: – merocrine glands – watery secretions

Types of Sebaceous Glands • Sebaceous glands: – associated with most hair follicles (on head and body) • Sebaceous follicles: – discharge directly onto skin surface – found on face and trunk – when clogged acne

Sebaceous glands

Types of Sweat Glands • Apocrine: – found in armpits, around nipples, and groin • Merocrine: – more numerous, widely distributed on body surface – especially on palms and soles (thick skin) Both are actually merocrine

“Apocrine” Sweat Glands • Merocrine secretions, not apocrine • Associated with hair follicles in groin, nipples, and axillae (armpits) • Become active at puberty • Produce sticky, cloudy secretions (thick sweat) that breaks down and causes odor

Merocrine Sweat Glands • Also called eccrine glands: – coiled, tubular glands – discharge directly onto skin surface – sensible perspiration for cooling (thin sweat) – water, salts, and organic compounds

Sweat Glands of the Skin Merocrine Apocrine

Epidermis What to look for: • Usually darkest between stratum germinativum and stratum granulosm (granulosm often a dark meandering line) • Keratinized cells (s. corneum) often lift off the underlying layers • S. germinativum along basal lamina, along with melanocytes

Dermis: Papillary vs. Reticular layer

What to look for • Papillary layer – has ridges – is areolar – Just under basal lamina • Reticular layer – much thicker – Dense irregular CT • Hypodermis – Loose CTP

More skin

Merocrine sweat gland • What to look for – Found in most skin – Coiled, tubular – Small lumens in cross section – Have duct that goes all the way to the epidermal surface and ends in sweat pore – Smaller than apocrine, don’t extend as deep into dermis

Apocrine sweat gland What to look for: • Associated with hair follicle • Only in nipples, groin, armpit • Large lumens • Deeper in dermis than merocrine

Apocrine sweat gland

Hair with sebaceous glands and arrector pilli

Hair What to look for: • Follicles are rarely complete • Can often see root, papilla at base of hair • Arrector pilli muscle at an angle • Associated glands (which are? )

Sebaceous glands

Sebaceous glands What to look for: • Associated with hair follicle • Found most everywhere hair follicles are found in skin • Look like cauliflower (maybe? )

Sebaceous follicle

Sebaceous follicle What to look for: • Also look like cauliflower • Found on face and trunk only • NOT associated with hair follicle • Have duct that opens onto skin surface