1. Anatomy and Physiology I
BIOL 2401
Chapter 5 Integumentary System

2. Integumentary system:
Skin
Accessory structures
glands, hair, nails, sensory receptors

3. Functions of the Skin Protection
Stratified epidermis…protects from abrasions
Sweat and sebum…protects from bacterial infections
Keratin…water proofing
Melanin…protects from UV
WBC in dermis…immunity
Temperature regulation
Sweat…evaporates to cause cooling
Blood vessels…vasoconstriction/vasodilation to regulate heat loss from warm blood in the skin
Arrector pili…goose bumps
Sensation
Nerves to sense touch, temperature and injury (pain)
Excretion
Sweat…salts, lactic acid, urea
Synthesis of vitamin D
For absorption of calcium 3

4. Skin Two parts/layers: Epidermis Dermis
*Subcutaneous layer attaches the skin to underlying muscles

5. Skin - Epidermis Stratified squamous epithelium
Composed of 4-5 layers:
Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale

6. Four Principle Cells of the Epidermis
keratinocytes produce the protein keratin, which helps protect the skin and underlying tissue from heat, microbes, and chemicals, and releases a waterproof sealant
Melanocytes produce the pigment melanin which contributes to skin color and absorbs damaging ultraviolet (UV) light
Langerhans cells- derived from bone marrow
participate in immune response
Merkel cells contact a sensory structure called a tactile (Merkel) disc and function in the sensation of touch

7. Skin Epidermis Stratum corneum: Top layer with flat, dead cells
Packed with keratin
Continuously shed as dander
Stratum lucidum:
Dead keratinocytes
Present only in thick skin (palm, sole)
Stratum granulosum:
Keratinocytes making keratin
Degenerating nucleus…dying cells
Stratum spinosum:
Live, non-dividing keratinocytes
Phagocytize melanin from melanocytes present in S basale
Stratum basale:
Deepest layer
Actively dividing cuboidal cells
Produce new cells that are pushed upwards to become keratinocytes of S spinosum
Have melanocytes (make melanin) and Merkel cells (touch sensation)

8. Skin - Dermis Connective tissue layer collagen & elastic fibers
fibroblasts, macrophages & fat cells
Contains
hair follicles
glands
nerves
blood vessels
Two major regions
papillary region
reticular region

9. Skin - Dermis Papillary region: Areolar (loose) connective tissue
Upper region of dermis
Has finger like projections - dermal papillae
Contains capillaries that feed epidermis
Contains Meissner’s corpuscles (touch) & free nerve endings for sensations of heat, cold, pain, tickle, and itch
Dermal papillae reflect on the surface as epidermal ridges and fingerprints – increase friction for grasping objects 9

10. Skin - Dermis Reticular region: Dense connective tissue
Lower region of dermis
Has glands, hair follicles and fat tissue
Specific arrangement of collagen fibers reflect on the surface as cleavage lines and wrinkle lines
Provides strength and ealsticity to the skin 10

11. Skin - Hypodermis Also referred to as: Subcutaneous layer
Superficial fascia
Made of adipose tissue (loose connective tissue)
Attaches skin to the underlying muscle layers 11

12. Skin Color Three main factors affecting skin color: 1. Melanin:
Brown pigment
Gives brown color to the skin
Made by melanocytes in S basale layer
Pigment phagocytized by keratinocytes of upper layers of epidermis
Amount of pigment is controlled by:
Genetics
UV exposure
Hormone
2. Carotene:
Yellow pigment (also found in yellow fruits and vegetables)
Used to make vitamin A
Gives yellow hue to the skin
3. (Hemoglobin) Blood capillaries:
Network of capillaries varies in dermis
Gives reddish color to the skin

13. Skin color clues:
Jaundice - yellowish color to skin and whites of eyes due to the buildup of yellow bilirubin in blood from liver/blood disease
Cyanosis - bluish color in the nails and skin due to oxygen circulation deficiencies
Erythema: redness of skin due to dilation of blood capillaries in the dermis, caused by inflammation, infection, allergy or burns
Albinism: melanocytes are present but melanin gene is mutated  little or no melanin made  no color in the skin, hair and eyes
Vitiligo: partial or complete loss of melanocytes  patchy skin

14. Accessory Structures of the Skin
Formed by the epidermis
Hair - Hair follicle
Glands
Sudoriferous gland
Sebaceous gland
Nails

15. Accessory Structures of the Skin - Hair
Hair parts:
Shaft
Root
Made of:
medulla, cortex & cuticle
Hair follicle:
Jacket that surrounds hair root
Made by pushing in of the S basale and S spinosum of the epidermis
Base of the follicle
Bulb
Surrounded by touch sensitive nerves – hair root plexus
blood vessels
germinal cells in papilla for hair growth
Arrector pili:
Smooth muscle band - attaches follicle to epidermis
Contracts  goose bumps

16. Accessory Structures of the Skin - Hair16

17. Hair Color, Growth and Function
Hair color depends upon amount and type of melanin:
Dark hair – a lot of melanin
Red and blonde hair – different type of melanin
Gray hair – decrease in melanin production (decreasing tyrosinase)
White hair – absence of melanin and presence of air bubbles in hair medulla
Hair growth cycle:
Growth stage
lasts for 2 to 6 years
matrix cells at papilla of hair root producing cells
Resting stage
lasts for 3 months
cells accumulate keratin & follicle atrophies
Old hair falls out and growth stage begins again
Normal hair loss is 70 to 100 hairs per day
Growth and replacement cycle affected by illness, diet, high fever, surgery, blood loss, severe emotional stress, and gender (hormones).
Chemotherapeutic agents affect the rapidly dividing matrix hair cells resulting in hair loss.
Function: protects from sun, prevents heat loss, and provides touch sensitivity

18. Glands of the Skin Exocrine glands: Sebaceous (oil) glands
Sudiferous (sweat) glands
Ceruminous (wax) glands
Mammary (milk) glands

19. Glands of the Skin - Sebaceous Gland
Usually connected to hair follicles
Absent in the palms and soles
Located in the dermis
Exocrine gland
produce sebum
contains cholesterol, proteins, fats & salts
secretions are stimulated by hormones at puberty
Function:
moistens hairs
waterproofs and softens the skin
inhibits growth of bacteria & fungi (ringworm)
Acne
bacterial inflammation of glands
Glands of the Skin - Sebaceous Gland 19

20. Glands of the Skin - Sudoriferous Gland
Located in the dermis
Duct opens on to the surface of the skin
Function:
regulates body temperature through evaporation (perspiration)
help eliminate wastes such as urea
Sweat: water, salts, urea, lactic acid, ammonia…. 20

21. Eccrine sweat glands
Apocrine sweat glands
Located all over the body, more in the palm and soles
limited in distribution to the skin of the axilla, pubis, and areolae
Secretory portion is in dermis with duct to surface
secretory portion in dermis
duct that opens onto hair follicle
Active right after birth
Active after puberty
Secretion is commonly referred to as “sweat”
secretions are more viscous, and have a distinct odor.
regulate body temperature through evaporation (perspiration)
help eliminate wastes such as urea.

22. Glands of the Skin – Other Glands
Ceruminous (wax) glands:
Present in the skin lining the external canal of the ear
Modified sudoriferous gland
Secretes a waxy liquid (cerumen)
Function: Protection against moisture and insect entry into the ear canal
Mammary (milk) glands:
Located between the pectoralis major muscle and the skin
Secretes milk
Function: Nutrition for the newborn 22

23. Nails Made of thick, keratinized epidermis Divided into:
Nail body - visible part
Nail root – embedded into the skin
Lunula: white region of the nail body…thickened stratum basale
Eponychium (cuticle): stratum corneum layer that projects over the nail body
Nail growth: in the nail matrix surrounding the nail root 23

24. Mostly refers to differences in epidermis of the skin
Thick vs. Thin Skin
Mostly refers to differences in epidermis of the skin
Thin Skin
Skin is thin and smooth
Most regions of the body
Epidermis has four layers:
S corneum
S granulosum
S spinosum
S basale
S corneum is thinner
Sebaceous glands are present
Fewer sudoriferous glands
Fewer sensory receptors
Thick Skin
Skin is thicker and rougher
Specific regions – palm and sole
Epidermis has five layers:
S corneum
S lucidum
S granulosum
S spinosum
S basale
S corneum is thicker
Seceous glands are absent
More sudoriferous glands
More sensory receptors

25. Skin Wound Healing Two types of injuries: Superficial wounds
Such as abrasions and superficial burns
Healing may take 24 – 72 hours
Deep wounds
Such as deep lacerations or surgical incisions
May take days to months 25

26. Skin Wound Healing – Superficial Wound Healing
Stratum basale cells from the periphery of the wound  migrate towards the center  divide to make new epidermal cells  replace the lost tissue  cells become keratinized and pick up melanin  skin becomes normal 26

27. Skin Wound Healing – Deep Wound Healing
Inflammatory phase – Bleeding is stopped by a clot; WBC migrate to clean up
Migratory phase – Clot dries to form scab; S basale cells of epidermis migrate under the scab; Fibroblasts of the dermis migrate to form new fibers
Proliferative phase – Extensive activity of epidermal cells to make new epidermis; Continued addition of fibers to form new dermis; New blood vessels grow in
Maturation phase – The scab comes off; New skin appears from underneath; Scar tissue is lighter and may lack accessory structures 27

28. Clinical Applications
Skin Burns:
Caused by: Fire, electricity, radiations, and chemicals
Effects on the body: Dehydration, lowered body temperature, decreased blood pressure, decreased or no urine production (kidneys shut down), infections
First degree burn – epidermis is damaged  erythema, pain, flaking and peeling
Second degree burn – epidermis and part of the dermis is damaged  erythema, blister formation, pain, partial loss of skin functions and some scarring
Third degree burn – epidermis, dermis and accessories lost  marble white area surrounded by redness, major scarring
Skin Graft:
Autograft – skin from one area to another area of the same individual
Isograft – skin from an identical twin…matching MHC antigens
Homograft – temporary graft skin from another person (donor, cadaver, foreskin)
Heterograft – temporary grafts from another animal
Synthetic skin – artificial skin, temporary use only. 28

29. Skin Cancer 1 million cases diagnosed per year
3 common forms of skin cancer
basal cell carcinoma (rarely metastasize) more than 70% cases
squamous cell carcinoma (may metastasize) approx 25% cases
malignant melanomas (metastasize rapidly) approx 5% cases
most common cancer in young women
arise from melanocytes ----life threatening
key to treatment is early detection watch for changes in symmetry, border, color and size
risks factors include-- skin color, sun exposure, family history, age and immunological status

30. Clinical Applications
Psoriasis: more rapid division of the stratum basale  thicker S corneum  dry scales and flakes on the surface
Callus and Corns: frequent friction on skin over a bone  thicker S corneum  painful thickening
Stretch marks: due to sudden stretching of the reticular region of the dermis
Tattoos: special pigments used to permanently color the dermis 30

31. Aging and Integumentary System
Number of fibroblasts and fibers decrease
Skin looses it’s elasticity and attachment to underlying layers
WBC (macrophages) does not protect
Infections
Loss of subcutaneous fat
Skin becomes thinner
Decrease in activity of sebaceous and sudoriferous glands
Skin dries, cracks and gets infected
Decrease in melanocyte number and activity
Skin color becomes patchy 31