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

2. Skin = cutaneous membrane = integument = epidermis + dermis
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 ft.2
Weighs ~ 9 lbs.
Every square inch contains ~ 15 feet of blood vessels, 12 feet of nerves, 650 sweat glands, 100 oil glands, sensory receptors, over 3 million cells.
Entire epidermis regenerates every days!

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

5. Deep to dermis is the hypodermis
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 of Epidermis

9. Stratum basale (deepest layer)
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 – Langerhans cells
Stratum granulosum (granular layer)
3-5 rows of flattened keratinocytes (produce keratin)

10. Stratum lucidum (clear layer)
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
Melanin
The pigment, melanin, is produced by melanocytes in the stratum basale.
Color is yellow to brown to black
Melanocytes have 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

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

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

15. Most superficial dermal layer
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. Reticular layer Thicker than papillary layer
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. Why do surgeons make incisions along these lines?
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. Appendages of the Skin:
Skin and Body Membranes: Integumentary System, Anatomy
Appendages of the Skin:
Hair & Nails

23. Hair Produced by hair bulb matrix
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. Root the part of hair enclosed in the follicle.
Skin and Body Membranes: Skin appendages, hair
Root the part of hair enclosed in the follicle.
Shaft the part of hair projecting from the surface of the scalp or skin

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

28. Flat shaft = curly/kinky hair Oval shaft = wavy hair
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. Associated Hair Structures
Skin and Body Membranes: Skin appendages, hair
Associated Hair Structures
Hair follicle
Dermal and epidermal sheath surround hair root
Arrector pili muscle
Smooth muscle that surrounds hair follicles and contracts when cold or frightened
Sebaceous gland
Sweat gland

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

31. Nails Heavily keratinized, scale-like modifications of the epidermis.
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. Nail Structures Free edge Body Root of nail
Skin and Body Membranes: Skin appendages, nails
Nail Structures
Slide 4.22
Free edge
Body
Root of nail
Nail folds -skin folds that border nail
Cuticle -thick proximal nail fold
Lunula –white crescent
Figure 4.9