1. The Integumentary System
Human Anatomy & Physiology I

2. Introduction Integumentary (inte: whole; gument: body covering)
Helps protect the body, helps maintain a constant body temperature, and provides sensory information about the environment.
Of all the body’s organs, none is more easily inspected or more exposed to infection, disease, and injury than the skin.

3. Introduction

4. Introduction

5. Functions of the skin Helps regulate body temperature
Serves as water repellent
Protective barrier between the external environment and internal tissues

6. Functions of the skin
Excretes a small amount of salts and several organic compounds
Some capacity to absorb substances
Helps synthesize the active form of vitamin D

7. Thermoregulation Two (2) ways: By liberating sweat
By adjusting the flow of in the dermis

8. Protection Bacterial infection Mechanical injury Chemical injury
Dehydration
UV radiation

9. Cutaneous Sensations Tactile sensations Thermal sensations Pain
Tactile touch
Pressure
Vibration
Tickling
Thermal sensations
Pain

10. Excretion Elimination of substances from the body
Water evaporation (about 400 mL/daily)
Sedentary person loses and additional 200 mL per day as sweat
Sweat (vehicle for excretion of salts, CO2, ammonia & urea)

11. Absorption Certain lipid-soluble materials: Fat soluble vitamins
Certain drugs
Gases (O2 & CO2)
Toxic materials (mercury)
Toxins (poison ivy)

12. Synthesis of vitamin D
Requires activation of a precursor molecule in the skin (UV rays)
Enzymes in liver & kidney modify the activated molecule finally producing calcitriol (most active form of vitamin D)
Calcitriol is a hormone that aids in the absorption of calcium in the GI tract

13. Structures of the skin Epidermis (epi: above) Dermis
Hypodermis (hypo: below)

14. Epidermis The epidermis is keratinized stratified squamous epithelium.
4 types of cells
4 to 5 “strata” or layers (depending on the location)

15. Types of cells Keratinocytes: most of the skin cells
Tactile (Merkel) cells: receptor/sensation
Melanocytes: production of the pigment melanin
Langerhans: immune response

16. Layers of the epidermis
Stratum basale
Stratum spinosum
Stratum granulosum
Stratum lucidum*
Stratum corneum

17. Stratum Germinativum (Basale)
Deepest layer (closest to dermis)
Single row of cuboidal or columnar keratinocytes
Some cells in the layer are stem cells (undergo cell division to continually produce new keratinocytes)

18. Stratum spinosum Superficial to stratum basale
8 to 10 layers of keratinocytes
Projections of both Langerhans and melanocytes also appear in this stratum

19. Stratum granulosum 3 to 5 layers of flat keratinocytes
Marks the transition between the deeper, metabolically active strata and the dead cells of the more superficial strata.

20. Stratum lucidum*
Present only in the thick skin of the fingertips, palms, and soles
3 to 5 layers of flattened clear, dead keratinocytes
Large amount of keratin

21. Stratum corneum 25 to 30 layers of flattened dead keratinocytes.
Cells are continuously shed and replaced by cells from the deepest strata.
Constant exposure of skin to friction stimulates the formation of a callus (abnormal thickening of the stratum corneum).

22. Dermis
Composed mainly of connective tissue containing and elastic collagen fibers.
Blood vessels, nerves, glands, and hair follicle are embedded in the in dermal tissue.

23. Dermis
Two layers:
Papillary layer
Reticular layer
Dermal papillae: extensions of the dermis into the epidermis
forming the ridges of the fingerprints

24. Hypodermis Deep to the dermis, but not part of the skin!
Mostly adipose tissue
Serves as a storage depot for fat and contains large blood vessels that supply the skin.

25. Hair Hair on the head guards the scalp from injury and the sun’s rays.
Decreases heat loss from the scalp.
Eyelashes and eyebrows protect the eyes from foreign particles.
Sensory (touch receptors)

26. Nails
Nails are plates of tightly packed, hard, keratinized epidermal cells.
Nail body: visible part
Free edge: extend past the distal end of the digit
Nail root: portion that is buried in a fold of skin
Lunula: whitish, crescent-shaped

27. Sweat (sudoriferous) gland
There are two main types: eccrine and apocrine sweat glands.
The cells of sweat glands release their secretions by exocitosis and empty them into hair follicles of onto the skin surface through pores.

28. Eccrine sweat glands Distribution: Throughout the skin
Location of secretory portion: mostly deep in dermis
Termination of excretory duct: surface of epidermis
Secretion: less viscous; consist of water, ions, urea, uric acid, ammonia, glucose, and lactic acid
Functions: thermoregulation, and waste removal
Onset of function: soon after birth

29. Apocrine sweat glands
Distribution: skin of axilla, groin, areola, and bearded regions of face
Location of secretory portion: mostly in subcutaneous layer
Termination of excretory duct: hair, follicle
Secretion: more viscous; consist of same components as eccrine sweat glands plus lipids and proteins
Functions: stimulated during emotional stress and sexual excitement
Onset of function: puberty

30. Sebaceous (oil) glands
Usually connected to hair follicles.
They are absent in the palms and soles.
Sebaceous glands produce sebum, which moistens hairs and waterproofs the skin.
Clogged sebaceous glands may produce acne.

31. Hyperthermia Increased blood and internal temperature.
Increased temperature is sensed by the hypothalamus.
Vasodilation occurs in skin blood vessels so more heat is lost from the skin.
Sweat glands become active, increasing evaporative heat loss.
Body temperature decreases!

32. Hypothermia Decreased blood and/or skin temperature.
Decreased temperature is sensed by the hypothalamus.
Vasoconstriction occurs in skin blood vessels so less heat is loss to the environment.
Skeletal muscles are activated, causing shivering, which increases metabolism and generates heat.
Body temperature increases.