Integumentary System Skin, Hair, Nails, Associated Glands & Structures Skin is sometimes called the cutaneous membrane.

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 3 Skin & Accessory Structures Skin –large waterproof covering –UV light and chemical protection –Covers 3000 square inches of the body –Weighs 6 lbs –Helps regulate body temperature Accessory structures –hair, nails, glands

Skin Functions Protects deeper tissues from: – Mechanical damage – Chemical damage – Bacterial damage – Thermal damage – Ultraviolet radiation – Desiccation

Skin Functions Aids in heat regulation Aids in excretion of urea and uric acid Synthesizes vitamin D

Meissner’s Corpuscle A Mechanoreceptor of Touch

5.5.

Epidermis

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 15 General Characteristics Stratified, squamous, keratinized, epithelium Held together by desmosomes (allows the flexibility of the skin) Thickest on the palm and soles Thinnest over the ventral surface of trunk

Skin Structure Epidermis – outer layer – Stratified squamous epithelium – Often keratinized (hardened by keratin) Dermis Figure 4.3

Layer of Epidermis Stratum corneum – Shingle-like dead cells Stratum lucidum – Occurs only in thick skin

Layer of Epidermis Stratum granulosum Stratum spinosum Stratum basale – Cells undergoing mitosis – Lies next to dermis

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 19 The Stratum Corneum Outermost layer Dead, keratinized cells Barrier to light, heat, chemicals, microorganisms “leathery” layer

Stratum Corneum Consists of about 20% water Constantly losing this layer Thickness depends on use (hands, soles) A thick Callus can form from heavy use Abrasions on the foot produce Corns ©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 20

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 21 The Stratum Lucidum One to two cell layers thick Flat and transparent Difficult to see

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 22 The Stratum Spinosum Several layers of spiny-shaped cells Desmosomes prevalent –Desmosomes: interlocking cellular bridges

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 23 The Stratum Granulosum Two or three layers Flattened cells Active keratinization Lose nuclei Compact and brittle

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 24 The Stratum Germinativum Deepest and most important layer Rests on basement membrane Lowermost layer called stratum basale New cells produced here (mitosis) This layer must remain intact so the epidermis will regenerate

Stratum Germinativum Melanocytes - produce melanin Produces skin color Irregularly shaped All races have the same number of melanocytes, but specific genes that determine the amount of melanin produced ©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 25

Skin Structure Figure 4.4

Non-vascularized The lowermost cells divide by mitosis Keratinization occurs as new cells rise –cells move to surface, lose water and nuclei change –Filled with keratin (protein) Composed of five layers ©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 28

The Dermis True Skin (Corium)

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 30 Divisions of the Dermis Papillary –adjacent to the epidermis Reticular –between papillary and subcutaneous Subcutaneous (hypodermis) –layers of fat below the dermis –Where you get hypodermic injections

Dermis Two layers – Papillary layer Projections called dermal papillae Pain receptors Capillary loops – Reticular layer Blood vessels Glands Nerve receptors

Hypodermis aka Subcutaneous Layer Deep to dermis – Not part of the skin – Anchors skin to underlying organs – Composed mostly of adipose tissue

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 33 Structures Found in Dermis The following are all found here in the dermis –Blood and lymph vessels –Nerves –Muscles –Glands –Hair follicles

Sebaceous Glands – Produce oil (Sebum) Lubricant for skin Kills bacteria – Most with ducts that empty into hair follicles

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 35 Sebaceous Glands –Brushing hair brings more out –secretion controlled by endocrine system –Increases at puberty Causes acne Later on, it decreases and causes dry skin

Suderiferous Glands Sweat glands – Widely distributed in skin – Two types Eccrine – Open via duct to pore on skin surface Apocrine – Ducts empty into hair follicles

Suderiferous Glands Sweat –most numerous in palms and soles 3000 per square inch on palms –Not found on lips or male genitalia –sweating helps cool the body Same materials as blood Odorless (smell is bacteria) ©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 37

Sweat and Its Function Composition – Mostly water – Some metabolic waste – Fatty acids and proteins (apocrine only) Function – Helps dissipate excess heat – Excretes waste products – Acidic nature inhibits bacteria growth Odor is from associated bacteria

Normal Skin Color Determinants Melanin – Yellow, brown or black pigments Carotene – Orange-yellow pigment from some vegetables Hemoglobin – Red coloring from blood cells in dermis capillaries – Oxygen content determines the extent of red coloring

Melanin Pigment (melanin) produced by melanocytes Color is yellow to brown to black Melanocytes are mostly in the stratum basale Amount of melanin produced depends upon genetics and exposure to sunlight

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 44

Dermis Pink tint of light skinned individuals is a result of the blood vessels here When you get embarrassed, blood vessels here dilate and causes blushing ©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 45

Hair

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 48 Hair One main characteristic of mammals Covers most of the surface of the body Three parts - cuticle, cortex, medulla –Cuticle Outermost part –Cortex Principal portion of hair Contain fibers that determine hair color –Medulla – central part of the hair

Shaft - visible portion Root - hair follicle –Has an outer connective tissue sheath Arrector pili - smooth muscle –Causes goose bumps –Involuntary ©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 49

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 50 Hair Characteristics Growth –hair follicle –cycles of growth and rest –Begins in the hair bulb (blood vessels to nourish) –Hair loss occurs because new hair pushes old hair down – baldness occurs because the follicle is lost too –The cycles depend on hair: Scalp hair grows for 3 years and rests for 1 or 2

Hair Texture - straight, curly, or tightly curly –Based on keratin in hair Color - based on complex genetic factors –Gray hair occurs due to a loss of pigment in the cortex ©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 51

Appendages of the Skin Hair – Produced by hair bulb – Consists of hard keratinized epithelial cells – Melanocytes provide pigment for hair color Figure 4.7c

Hair Anatomy Central medulla Cortex surrounds medulla Cuticle on outside of cortex – Most heavily keratinized Figure 4.7b

Nails

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 55 Nails Modified epidermal cells –Composed of very hard keratin Lunula - white crescent –Caused by air mixed in the keratin Body - visible portion Root - covered by skin Growth occurs from the nailbed –Grows about 1mm per week –Cuticle extends over the proximal end of the nail body –Fingernails grow faster than toe nails

Nails – Scale-like modifications of the epidermis Heavily keratinized – Stratum basale extends beneath the nail bed Responsible for growth – Lack of pigment makes them colorless

Free edge Body Root of nail Eponychium – proximal nail fold that projects onto the nail body Figure 4.9

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 60

Miscellaneous and Pathology

Homeostatic Imbalances Burns – Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals – Associated dangers Dehydration Electrolyte imbalance Circulatory shock

Rule of Nines Way to determine the extent of burns Body is divided into 11 areas for quick estimation – Each area represents about 9% Figure 4.11a

Severity of Burns First-degree burns – Only epidermis is damaged – Skin is red and swollen Second degree burns – Epidermis and upper dermis are damaged – Skin is red with blisters Third-degree burns – Destroys entire skin layer – Burn is gray-white or black

Critical Burns Burns are considered critical if: – Over 25% of body has second degree burns – Over 10% of the body has third degree burns – There are third degree burns of the face, hands, or feet

Skin Cancer Cancer – abnormal cell mass Two types – Benign Does not spread (encapsulated) – Malignant Metastasized (moves) to other parts of the body Skin cancer is the most common type of cancer

Skin Cancer Types Basal cell carcinoma – Least malignant – Most common type – Arises from statum basale Squamous cell carcinoma – Arises from stratum spinosum – Metastasizes to lymph nodes – Early removal allows a good chance of cure

Skin Cancer Types Malignant melanoma – Most deadly of skin cancers – Cancer of melanocytes – Metastasizes rapidly to lymph and blood vessels – Detection uses ABCD rule

ABCD Rule A = Asymmetry – Two sides of pigmented mole do not match B = Border irregularity – Borders of mole are not smooth C = Color – Different colors in pigmented area D = Diameter – Spot is larger then 6 mm in diameter