Chapter 4 Skin and Body Membranes Anatomy

1. Chapter 4Skin and Body MembranesAnatomy Essentials of Human Anatomy & Physiology, 7th ed. by Elaine N. Marieb

2. Skin and Body Membranes: Integumentary System, Anatomy • Skin = cutaneous membrane = integument = epidermis + dermis • Integumentary System = Skin + skin derivatives • Skin derivatives • Sweat glands • Oil glands • Hairs • Nails

3. Skin = Integument • Covers 15-20 ft.2 • Weighs ~ 9 lbs. • Every square inch contains ~ 15 feet of blood vessels, 12 feet of nerves, 650 sweat glands, 100 oil glands, 1500 sensory receptors, over 3 million cells. • Entire epidermis regenerates every 25-45 days!

4. Skin and Body Membranes: Integument • Epidermis – outer layer • Stratified squamous epithelium • Avascular • Often keratinized (hardened by keratin) • Dermis • Dense irregular connective tissue

5. Skin and Body Membranes: Integument • Deep to dermis is the hypodermis • Not part of the skin • Anchors skin to underlying organs • Composed mostly of adipose tissue

7. Skin and Body Membranes: Integumentary System, Anatomy Figure 4.4

8. Layers ofEpidermis

9. Skin and Body Membranes: Layers of Epidermis • Stratum basale(deepest layer) • Cells undergoing mitosis • Lies next to dermis • Contains two cell types: keratinocytes & melanocytes • Stratum spinosum(spiny layer) • Keratinocytes mature, filling cells with keratin protein • Phagocytic white blood cells – Langerhanscells • Stratum granulosum(granular layer) • 3-5 rows of flattened keratinocytes(produce keratin)

10. Skin and Body Membranes: Layers of Epidermis • Stratum lucidum(clear layer) • Occurs only in thick, glaborous (hairless) skin • Stratum corneum(outermost layer) • Shingle-like dead cells filled with keratin • 5-50 cell layers thick, depending upon location The stratum corneum is thickest in the soles of the feet. It’s thinnest in the eyelids.

12. Skin and Body Membranes: Epidermis • The pigment, melanin, is produced by melanocytes in the stratum basale. • Color is yellow to brown to black • Melanocyteshave cellular extensions, called dendrites that weave between the cells of the stratum basale and spinsoum. The keratinocytes absorb melanin from the dendrites, and skin is evenly colored…usually. • Amount of melanin produced depends upon genetics and exposure to sunlight Melanin

13. Skin and Body Membranes: Integumentary System, Anatomy Figure 4.4

14. Dense, irregular connective tissue • Thickness varies • Two layers: • papillary & • reticular Dermis

15. Skin and Body Membranes: Dermis • Papillary layer • Most superficial dermal layer • Capillaries which provide nutrients to the avascular epidermis through diffusion • Sense receptors: pain receptors (free nerve endings) & touch receptors (Meissner’s corpuscles) • Projections called dermal papillae

16. Skin and Body Membranes: Dermis, papillary layer • As the epidermis layers superficially to the dermis, the pattern of dermal papillae is amplified. Your fingerprints, handprints, and footprints are the pattern of your dermal papillae!

17. Skin and Body Membranes: Dermis • Reticular layer • Thicker than papillary layer • Blood vessels (arterioles, venules) help maintain body temperature homeostasis • Sweat and oil glands • Deep pressure receptors – Pacinian corpuscles • Connective tissue fibers: Collagen & Elastin

18. Skin and Body Membranes: Integumentary System, Anatomy

19. Skin and Body Membranes: Dermis, reticular layer Separation of bundles of collagen fibers form lines of cleavage in the skin. (Langer’s cleavage lines) Why do surgeons make incisions along these lines?

21. Skin and Body Membranes: Integumentary System, Anatomy Figure 4.4

22. Skin and Body Membranes: Integumentary System, Anatomy Appendages of the Skin: Hair & Nails

23. Skin and Body Membranes: Skin appendages, hair • Hair • Produced by hair bulb matrix • Consists of hard keratinized epithelial cells • Melanocytes provide pigment for hair color • Composed of a root & shaft Figure 4.7c

25. Skin and Body Membranes: Skin appendages, hair Rootthepart of hair enclosed in the follicle. Shaftthepart of hair projecting from the surface of the scalp or skin

26. Skin and Body Membranes: Skin appendages, hair • Central medulla • Cortex surrounds medulla • Cuticle on outside of cortex (heavily keratinized) Shaft Figure 4.7b

28. Skin and Body Membranes: Skin appendages, hair The shape of the hair shaft determines the macroscopic appearance of the hair. Flat shaft = curly/kinky hair Oval shaft = wavy hair Round shaft = straight hair

29. Skin and Body Membranes: Skin appendages, hair • Hairfollicle • Dermal and epidermal sheath surround hair root • Arrectorpili muscle • Smooth muscle that surrounds hair follicles and contracts when cold or frightened • Sebaceous gland • Sweat gland Associated Hair Structures

30. Skin and Body Membranes: Integumentary System, Anatomy Figure 4.4

31. Skin and Body Membranes: Skin appendages, nails • Nails • Heavily keratinized, scale-like modifications of the epidermis. • Only two layers of epidermis extend beneath the nail bed: stratum basale& stratum spinosum • Lack of pigment makes them colorless

32. Skin and Body Membranes: Skin appendages, nails Slide 4.22 Figure 4.9 • Free edge • Body • Root of nail • Nail folds -skin folds that border nail • Cuticle -thick proximal nail fold • Lunula –white crescent Nail Structures