The Integumentary System

• Layers beneath the skin

– Subcutaneous layer

– Deep fascia

• Functions of the Skin

– Protection

– Water resistance

– Temperature regulation

– Vitamin D synthesis

– Sensations

– Immunity

– Social signaling

· The Epidermis

– Stratum Germinativum

§ Stem cells

§ Melanocytes

§ Merkel cells

– S. Spinosum

§ “Pre-keratinocytes”

§ Melanocytes

§ Langerhans cells

– S. Granulosum

– S. Lucidum

§ Keratinocytes in both granulosum and lucidum

– S. Corneum

§ Dead keratinocytes

· The Dermis

– Reticular layer

§ Dense irregular CT

§ Provides strength and elasticity

– Papillary layer

§ Areolar CT

§ Contains cap’s and sensory neurons for epidermis

§ Arranged as dermal papillae

· Pigmentation of Skin

– Melanin

– Carotene

– Hemoglobin

· Epidermal Derivatives

– Hair Follicles and Hair

– Skin Glands

· Hair

– Function

§ Protection

§ Touch Sensation

– Structure

§ Root

§ Shaft

§ Bulb

– Hair Follicle

§ Sheath of epithelial cells

§ Surrounds root

§ Merges with bulb

– Associated structures

§ Dermal papilla

§ Sebaceous glands

§ Arrector pili

– Growth Cycle

§ 2-5 yrs: growth stage

§ 2 yrs: resting stage

– Skin Glands

§ Sebaceous glands

o Secrete sebum

o Help to protect hair and skin

§ Merocrine (eccrine) sweat glands

o BT control

o Excretion

o Protection

§ Apocrine sweat glands

o Secrete pheromones?

§ Mammary glands

§ Ceruminous glands

· Skin Sensory Receptors

– Free nerve endings

– Pacinian corpuscles

– Meissner’s corpuslces

Lines of Cleavage