1. Chapter 5 *Lecture Outline
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2. Chapter 5 Outline Structure and Function of the Integument Epidermis
Hypodermis
Accessory Organs
Repair and Regeneration
Aging and Development

3. Intro to the Integument
Integument = skin
largest organ (7% to 8% of body weight)
two layers
epidermis: superficial layer of stratified squamous epithelium
dermis: deeper layer of areolar and dense irregular connective tissues
hypodermis (not part of the skin) lies under dermis, mostly adipose connective tissue

4. The Integument Figure 5.1 Hair shaft Sweat pore Epidermis
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Hair shaft
Sweat pore
Epidermis
Epidermal ridge
Dermal papilla
Papillary
layer
Arrector pili muscle
Sebaceous (oil) gland
Dermis
Sweat gland duct
Reticular
layer
Merocrine sweat gland
Sensory nerve fiber
Apocrine sweat gland
Vein
Artery
Subcutaneous
layer
Adipose connective tissue
Hair follicle
Sensory
receptors
Areolar
connective tissue
Figure 5.1

5. Integument Functions Protection Prevention of H2O loss
Temperature regulation
Metabolic regulation
Immune defense
Sensory reception
Excretion/Secretion

6. The Epidermis Most superficial layer Avascular
Keratinized stratified squamous epithelium
keratin is a water-insoluble protein
4 to 5 layers (strata) of distinct cell types

7. Epidermal Strata From deep to superficial (as they grow):
stratum basale
stratum spinosum
stratum granulosum
stratum lucidum (found only in thick skin)
stratum corneum

8. Stratum Basale Only layer that undergoes mitosis
One layer of cells adjacent to the dermis
keratinocytes: most abundant; produce keratin to waterproof the skin
melanocytes: cells with long, branched cytoplasmic processes; produce a pigment (black, brown, or yellow) that absorbs UV light to prevent DNA damage, reducing some forms of skin cancer
tactile cells: sense touch

9. Cells of the Stratum Basale
Figure 5.2

10. Melanocytes
Figure 5.4

11. Stratum Spinosum Several layers thick
Daughter cells from the stratum basale
differentiate into nondividing (may see a rare mitotic cell), highly specialized keratinocyte
Epidermal dendritic cells
phagocytes that engulf invading pathogens

12. Cells of the Stratum Spinosum
Figure 5.2

13. Stratum Granulosum Three to five layers of keratinocytes
cytoplasm fills with keratin filaments
organelles begin to degrade
fully keratinized cells are dead but strong and water-insoluble

14. Stratum Granulosum Cells
Figure 5.2

15. Stratum Lucidum Thin, translucent region, two to three layers thick
Present only in thick skin such as sole of feet and palms of hands
Cells lack organelles, filled with eleidin
transparent, intermediate product of keratin maturation

16. Cells of the Stratum Lucidum
Figure 5.2

17. Stratum Corneum Most superficial layer of epidermis
Thickness varies from a few to 30 layers thick depending on location on the body
Comprised solely of dead keratinocytes
sloughed off by abrasion = dust

18. Cells of the Stratum Corneum
Figure 5.3

19. Epidermal Variation: Skin Color
Skin color is determined by three pigments:
hemoglobin: blood pigment; causes light complexions to look pink (or blue)
melanin: pigment produced by melanocytes; increases in people exposed to more UV light
carotene: yellow-orange pigment from food that builds up in the skin

20. Abnormal Skin Colors

21. Epidermal Variation: Skin Markings
Nevus: localized overgrowth of melanocytes
a.k.a. mole
Hemangioma: proliferation of blood vessels
may disappear (strawberry) in childhood or may persist (port-wine) through adulthood
Friction ridges: folds of epidermis/dermis on fingers, palms, soles, and toes for grasping
cause us to leave fingerprints

22. Fingerprints
Figure 5.5

23. The Dermis Lies deep to the epidermis
Two layers of connective tissues:
Papillary: superficial
Reticular: deeper
mainly collagen fibers
contains blood vessels, glands, hair follicles, nail roots, sensory nerve endings, and smooth muscle

24. The Dermis
Figure 5.6

25. The Papillary Layer Directly below stratum basale cells of epidermis
dermal papillae and epidermal ridges interlock, increasing the surface area between epidermis and dermis
dermal papillae contain capillaries that supply nutrients to the avascular epidermal cells

26. The Reticular Layer Forms majority of the dermis
Comprised mainly of dense irregular connective tissue with large bundles of collagen fibers, blood vessels, glands, hair follicles, and nerves
collagen bundles help connect dermis to underlying hypodermis

27. Lines of Cleavage
Lines in the deep dermis formed by the orientation of collagen bundles
importance to surgeons: incisions across these lines heal more slowly than incisions along the lines

28. Lines of Cleavage Figure 5.7 An incision perpendicular to
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An incision
perpendicular to
cleavage lines may
gape and delay healing.
An incision parallel
to cleavage lines is more
likely to heal quickly and
not gape open.
Figure 5.7

29. Innervation Nerve fibers are present in dermis Functions:
tactile (touch) receptors
control blood flow
control glandular secretion

30. Blood Supply Epidermis: avascular Dermis: contains blood vessels
important in controlling body temperature
vasoconstriction: narrowing blood vessels preserves core body heat
vasodilation: widening blood vessels releases body heat, lowering body temperature

31. The Hypodermis A.K.A. subcutaneous layer Functions:
deep to, not really part of, the integument
areolar and adipose connective tissues
Functions:
protects underlying structures
stores energy
thermal insulation

32. Hypodermis (Subcutaneous Layer)
Figure 5.6

34. Epidermal Derivatives
Structures that grow from the epidermis:
Nails
Hairs
Glands

35. Nails Derived from the stratum corneum
Cells densely packed together filled with parallel fibers of hard keratin
The nail plate has a whitish free edge, a pinkish nail body, and a nail root
The nail body covers a layer of epidermis called the nail bed
The nail bed appears pink because of the underlying capillaries

36. Nails Protective structures on digits Parts
nail body: flat keratinized cells protecting digit
nail bed: live epidermal cells under nail body
nail root: region hidden by cuticle
nail matrix: thickened growing part of the nail bed
lunula: white semilunar proximal area of nail body caused by thickened underlying stratum basale obscuring capillaries in dermis

37. Fingernail
Figure 5.8

38. Hair
Columns of keratinocytes growing from follicles deep in dermis or hypodermis
Regions of a hair from deep to surface:
Hair bulb
Hair root
Hair shaft

39. Structure of a Hair Figure 5.9 Shaft (beyond epidermis) Root Sebaceous
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Shaft
(beyond epidermis)
Root
Sebaceous
(oil) gland
Hair follicle
Arrector
pili muscle
Matrix
Hair bulb
Melanocyte
Figure 5.9
Hair papilla
(a)

40. Hair Structure From deep to superficial
hair papilla: connective tissue, nerves, and blood vessels below follicle that support the keratinocytes
hair bulb: a swelling at bottom of follicle filled with dividing keratinocytes; increase in hair matrix causes hair growth
arrector pili: involuntary smooth muscle attached to hair shaft; responds to emotional states (fear or rage) and cold temperatures by contracting, standing hair up, and producing “goose bumps”

41. © Biophoto Associates/Photo Researchers, Inc.
Structure of a Hair
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Connective
tissue root
sheath
Cortex
Cuticle
External root
sheath
Internal root
sheath
Hair
bulb
Matrix
Hair papilla
LM 100x
Figure 5.9
(b)
© Biophoto Associates/Photo Researchers, Inc.

42. Functions of Hair Protection Heat retention Facial expression
Sensory reception
Visual identification
Chemical signal dispersal

43. Skin Exocrine Glands Two most common types: Two rarer types:
sweat glands: produce watery solution
merocrine and apocrine
sebaceous glands: produce oily secretions
Two rarer types:
ceruminous glands: produce ear wax
mammary glands: produce milk

44. Sweat Glands
Figure 5.10

45. Merocrine Sweat Glands
Simple coiled tubular glands that secrete into a duct with a pore on skin’s surface
secretion is 99% H2O, clear, and controlled by nervous system
numerous on forehead, palms, and soles
Functions:
Thermoregulation
Secretion
Protection

46. Apocrine Sweat Glands
Simple coiled tubular glands that secrete into hair follicles around nipples (areolae), armpits (axillae), groin (pubic), and anus (anal)
secretion is thick, cloudy, proteins and lipids
leads to bacterial growth, causing body odor in the above regions

47. Sebaceous Glands Secrete oily sebum into hair follicles
lubricates hair and skin
relatively inactive during childhood; sex hormones at puberty cause secretions to increase significantly