1. 5
The Integumentary System

2. An Introduction to the Integumentary System
Learning Outcomes
5-1 Describe the main structural features of the epidermis, and explain the functional significance of each.
5-2 Explain what accounts for individual differences in skin color, and discuss the response of melanocytes to sunlight exposure.
5-3 Describe the interaction between sunlight and vitamin D3 production.
5-4 Describe the roles of epidermal growth factor.

3. An Introduction to the Integumentary System
Learning Outcomes
5-5 Describe the structure and functions of the dermis.
5-6 Describe the structure and functions of the hypodermis.
5-7 Describe the mechanisms that produce hair, and explain the structural basis for hair texture and color.

4. An Introduction to the Integumentary System
Learning Outcomes
5-8 Discuss the various kinds of glands in the skin, and list the secretions of those glands.
5-9 Describe the anatomical structure of nails, and explain how they are formed.
5-10 Explain how the skin responds to injury and repairs itself.
5-11 Summarize the effects of aging on the skin.

5. Integumentary Structure/Function
Integumentary System Components
(1) Cutaneous membrane
Epidermis
Dermis
(2)Accessory structures
(3) Subcutaneous layer (hypodermis)
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6. Integumentary Structure/Function
Main Functions of the Integument
Protection- from impact, infection, fluid loss
Temperature maintenance – heat exchange
Synthesis and storage of nutrients – vitamin D3
Sensory reception – touch, pressure, pain, temp.
Excretion and secretion – salt, water, milk
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7. Integumentary Structure/Function
Components of the Integumentary System
Figure 5-1

8. Integumentary Structure/Function
The Epidermis
Stratified squamous epithelium
Several distinct cell layers
Thick skin (.5 mm) - five layers
On palms and soles
Thin skin (.08) - four layers
On rest of body
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9. Integumentary Structure/Function
Cell Layers (strata) of The Epidermis
Stratum germinativum – attaches to b.m.
Stratum spinosum
Stratum granulosum
Stratum lucidum (in thick skin)
Stratum corneum – top layer
Dying superficial layer
Keratin accumulation – keratinized cells
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10. Integumentary Structure/Function
The Structure of the Epidermis
Figure 5-2

11. Integumentary Structure/Function
Cell Layers of The Epidermis
Stratum germinativum – deepest layer attaches with hemidesmosomes
Basal layer – “finger prints”
Stem cells – (germinative cells)
Cell division layer
Source of replacement cells
Melanocytes
Synthesize melanin
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

12. Integumentary Structure/Function
Cell Layers of the Epidermis
Intermediate strata
Stratum spinosum (spiny layer)
Cells divide and add to layers of thickness
Superficial to stratum germinativum
Stratum granulosum (grainy layer)
Keratin granules in cytoplasm
No cell division
Stratum lucidum (clear layer) – only in thick skin.
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13. Integumentary Structure/Function
Cell Layers of the Epidermis
Stratum corneum (dead, dry)
Most superficial layer
Flattened (squamous) cells - 25 – 30 layers
Dead cells
Abundant keratin
Keratinized (also, cornified)
Tough, water-resistant protein
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14. Integumentary Structure/Function
Sources of Skin Color
Melanocytes
Make melanin
Melanin provides UV protection
Gives reddish-brown to brown-black color
Carotene
Contributes orange-yellow color
Provided from diet
Hemoglobin
Blood pigment
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15. Integumentary Structure/Function
Melanocytes
Figure 5-3

16. Integumentary Structure/Function
Effects of UV Radiation
Beneficial effect
Activates synthesis of vitamin D3
Harmful effects
Sun burn
Wrinkles, premature aging
Malignant melanoma
Basal cell carcinoma
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17. Integumentary Structure/Function
Two Important Types of Skin Cancer
Figure 5-4
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18. Integumentary Structure/Function
Key Note
The epidermis is a multi-layered, flexible, self-repairing barrier that prevents fluid loss, provides protection from UV radiation, produces vitamin D3, and resists damage from abrasion, chemicals, and pathogens
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

19. Integumentary Structure/Function
Layers of the Dermis
Composed of two layers:
-Papillary layer
- Reticular layer
Papillary layer
Underlies epidermis
Named for dermal papillae
Loose connective tissue
Supports, nourishes epidermis
Provides sensory nerves, lymphatics, and capillaries
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

20. Integumentary Structure/Function
Layers of the Dermis
Reticular layer
Tough, dense, fibrous layer
Collagen fibers
Limit stretch
Elastic fibers
Provide flexibility
Blends into papillary layer (above)
Blends into subcutaneous layer (below)
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

21. Integumentary Structure/Function
Other Dermal Components
Epidermal accessory organs (hair, nails, etc.)
Cells of connective tissues proper (mast, etc.)
Communication with other organ systems
Cardiovascular
Lymphatic
Nervous
Sensation
Control of blood flow and secretion
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

22. Integumentary Structure/Function
The Subcutaneous Layer (not actual integument)
Composed of loose connective tissue
Stabilizes skin position
Loosely attached to dermis
Loosely attached to muscle
Contains many fat cells
Provides thermal insulation
Cushions underlying organs
Safely receives hypodermic needles
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

23. Integumentary Structure/Function
Key Note
The dermis provides mechanical strength, flexibility, and protection for underlying tissues. It is highly vascular and contains a variety of sensory receptors that provide information about the external environment.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

24. Integumentary Structure/Function
Accessory Structures
- Include hair, glands, and nails
Hair follicle – project into the dermis and often subcutaneous layer.
Hair root – portion that anchors the hair
Hair shaft – the part we see
Cells die and become keratinized halfway to the surface of the skin marking the boundary of hair root and shaft.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

25. Integumentary Structure/Function
Hair components include medulla, cortex, cuticle
Arrector pili muscle attaches follicle to dermis
“goose bumps”.
Hair color reflects melanocyte activity and different forms of melanin (decreased production and air bubbles contribute to gray hair)

26. Integumentary Structure/Function
Hair Follicles
Figure 5-5(a)

27. Integumentary Structure/Function
Hair Follicles
Figure 5-5(b)

28. Integumentary Structure/Function
Hair Follicles
Figure 5-5(c)

29. Integumentary Structure/Function
Accessory Structures
Hair growth cycle
0.3 mm/day growth rate
2–5 years growth
2–5 years follicle rest
Follicle reactivation
Old hair shedding
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

30. Integumentary Structure/Function
Accessory Structures
Sebaceous glands (oil glands)
Holocrine gland
Oily secretion
Sebum
Hair shaft lubricant
Sebaceous follicle
Skin lubricant
Skin waterproofing
Becomes acne when clogged
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

31. Integumentary Structure/Function
The Structure of Sebaceous Glands and Their Relationship to Hair Follicles
Figure 5-6

32. Integumentary Structure/Function
Sweat Glands
Apocrine – (communication)
Odorous secretion (“funky”)
Absent before puberty
Present in axilla, areola, groin
Merocrine – primarily to cool the surface of the skin through evaporation.
Watery sweat (~1% NaCl)
For heat loss
Widely present in skin (up to 500/cm2)
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

33. Integumentary Structure/Function
Sweat Glands
Figure 5-7

34. Integumentary Structure/Function
Key Note
The skin plays a major role in controlling body temperature. It acts as a radiator, with the heat being delivered by the dermal circulation and removed primarily by the evaporation of sweat or perspiration.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

35. Integumentary Structure/Function
Accessory Structures: Nails
Nail body
Dense mass of keratinized cells
Nail bed
area of epidermis covered by nail body
Nail root
site of nail production
Cuticle - (eponychium)
Portion of stratum corneum that extends over the exposed nail.
Lunula
Obscured blood vessels that leave a pale crescent.
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36. Integumentary Structure/Function
The Structure of a Nail
Figure 5-8

37. Skin Injury and Repair Four Stages in Skin Healing Inflammation
Blood flow increases
Phagocytes attracted
Scab formation
Formed from insoluble network of fibrin
Cell division and migration
Stratum germinativum cells replace missing epidermal cells
Scar formation
Abnormally large amount of collagen fibers
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

38. Bleeding occurs at the site of injury immediately after the injury, and mast cells in the region trigger an inflammatory response.
After several hours, a scab has formed and cells of the stratum germinativum are migrating along the edges of the wound. Phagocytic cells are removing debris, and
more of these cells are arriving with the enhanced circulation in the area. Clotting around the edges of the affected area partially isolates the region.
Epidermis
Scab
Migratory
epithelial
cells
Macrophages
and
fibroblasts
Dermis
Sweat
gland
Granulation
tissue
One week after the injury, the scab has been undermined by epidermal cells migrating over the meshwork produced by fibroblast
activity. Phagocytic activity around the site has almost ended, and the fibrin clot is disintegrating.
After several weeks, the scab has been shed, and the epidermis is complete. A shallow depression marks the injury site, but fibroblasts in the dermis continue to create scar tissue that will gradually elevate the overlying epidermis.
Scar
tissue
Fibroblasts
Figure 5-9
1 of 5
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

39. Bleeding occurs at the site of injury immediately after the injury, and mast cells in the region trigger an inflammatory response.
Epidermis
Dermis
Figure 5-9
2 of 5
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

40. Macrophages and fibroblasts
Bleeding occurs at the site of injury immediately after the injury, and mast cells in the region trigger an inflammatory response.
After several hours, a scab has formed and cells of the stratum germinativum are migrating along the edges of the wound. Phagocytic cells are removing debris, and more of these cells are arriving with the enhanced circulation
in the area. Clotting around the edges
of the affected area partially isolates
the region.
Epidermis
Scab
Migratory
epithelial
cells
Macrophages
and
fibroblasts
Dermis
Sweat
gland
Granulation
tissue
Figure 5-9
3 of 5
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

41. One week after the injury, the scab has been undermined by epidermal cells migrating over the meshwork produced by fibroblast activity. Phagocytic activity around the site has almost ended, and the fibrin clot is disintegrating.
Fibroblasts
Figure 5-9
4 of 5
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

42. One week after the injury, the scab has been undermined by epidermal cells migrating over the meshwork produced by fibroblast activity. Phagocytic activity around the site has almost ended, and the fibrin clot is disintegrating.
After several weeks, the scab has been shed, and the epidermis is complete. A shallow depression marks the injury site, but fibroblasts in the dermis continue to create scar tissue that will gradually elevate the overlying epidermis.
Scar
tissue
Fibroblasts
Figure 5-9
5 of 5
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

43. Skin Injury and Repair
Table 5-1

44. Aging of the Skin Major Age-Related Changes
Injury and infection increase
Immune cells decrease
Sun protection diminishes
Skin becomes dry, scaly
Hair thins, grays
Sagging, wrinkles occur
Heat loss decreases
Repair slows
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

45. Figure 5-17 System Integrator: The Integumentary System
The integumentary system provides mechanical protection against environmental hazards. It forms the external surface of the body and provides protection from dehydration, environmental chemicals, and external forces. The integument (skin) is separated and insulated from the rest of the body by the subcutaneous layer, but it is interconnected with the rest of the body by an extensive circulatory network of blood and lymphatic vessels. As a result, although the protective mechanical functions of the skin can be discussed independently, its physiological activities are always closely integrated with those of other systems.
Skeletal
Page 275
Muscular
Page 369
Nervous
Page 543
Endocrine
Page 632
ABOUT THE SYSTEM INTEGRATORS
Since each body system interacts with every other body system, no one system can be completely understood in isolation. The integration of the various systems allows the human body to function seamlessly, and when disease or injury strikes, multiple systems must respond to heal the body.
These charts will introduce the body systems one by one and show how each influences the others to make them function more effectively, and in turn how other body systems influence the system you are studying. As we progress through the organ system, the complementary nature of these interactions will become clear. Homeostasis depends on the thorough integration of all the body systems working as one.
Cardiovascular
Page 759
Lymphatic
Page 807
Respiratory
Page 857
Digestive
Page 910
Urinary
Page 992
Reproductive
Page 1072 45