1

Unit 4The Integumentary

System

I. Classification of Body Membranes

A. Epithelial Membranes (3)

1. Cutaneous Membrane> Stratified Squamous> Sits on Dense Connective Tissue> Skin: Epidermis & Dermis> Dry Membrane

2. Mucus Membrane> Epithelial Cell type varies> Sits on Loose Connective Tissue> Lines all body cavities that open to exterior> Wet & Moist Membrane

3. Serous Membrane> Simple Squamous> Sits on Areolar Connective Tissue> Lines body cavities closed to exterior> Found in pairs

– Parietal layer: lines body cavity– Visceral layer: covers outside of organ– Layers are separated by Serous Fluid

> Types:– Peritoneum = Abdominal area– Pericardium = Heart area– Pleura = Lung area

2

3

I. Classification of Body Membranes cont'dB. Connective Tissue Membrane (1)

1. Synovial Membrane> Surrounds joints> Provides smooth surface> Secretes lubricating fluid

– Reduces friction

4

II. Cutaneous Membrane (Skin)A. Structure of the Skin

1. Epidermis• New every 35­45 days• Avascular• Cell Types:

> Keratinocytes ­ produce keratin> Melanocytes ­ produce melanin> Dendritic ­ defense> Tactile ­ sensory reception

• Stratified Squamous epithelium with ability to Keratinize & "Waterproof"> Hardening & drying out of cells through

production of Keratin> "Waterproof" ­ from glycolipid produced that coats

cells

• Epidermal Sections:> Stratum Corneum: outermost section

– 20­30 layers of Keratinized dead cells

> Stratum Lucidum> Stratum Granulosum> Stratum Spinosum

> Stratum Germinativum/Stratum Basale: deepest layer of epidermis– Area of cell division– Nourishment from dermis via diffusion

5

;

• Production of Melanin> by Melanocytes found in S. Germinativum

> What happens when skin is exposed to sunlight?– Melanocytes are stimulated to make more melanin

– Melanin phagocytized by Keratinocytes

– Natural "Sunscreen"« Melanin creates shield/umbrella over underlying

nucleus« prevents DNA mutations from UV rays

1. Epidermis cont'd

6

2. Dermis "hide"

• Composed of mostly Dense Connective Tissue• Split into two regions:

> Papillary: upper dermal region ﴾dermal papillae﴿– Aerolar Connective Tissue– Provide nutrients to epidermis ﴾blood vessels﴿– House pain receptors– Phagocytes– Creates patterns: "finger prints"

> Reticular: deepest dermal layer– Composed of collagen & elastic fibers ﴾Dense Irregular﴿

– Houses blood vessels ﴾vascularized﴿– Houses sweat & oil glands– Phagocytes

7

• Protection From:> Mechanical, Chemical, Thermal Damage

– S. corneum ﴾like "bricks & mortar"﴿« Multiple layers of dead keratinized cells = bricks« Glycolipids = mortar

> Bacterial Damage– Low pH– Chemicals in sweat & oil– Dendritic cells ﴾epidermis﴿ & macrophages ﴾dermis﴿

> Ultraviolet Radiation– Melanin = natural sunscreen

> Dessication ﴾drying out﴿– Glycolipids = waterproof barrier

• Aids in temperature regulation

• Excretion

• Vitamin D synthesis

B. General Functions

C. Skin Color• Determined by...

> Amount & Type of Melanin

> Amount of Carotene deposited in the S. Corneum

> Amount of O2 bound to Hemoglobin in dermal blood vessels

• Homeostatic Imbalances:> Cyanosis

> Jaundice

> Anemia

8

III. Accessory StructuresA. Glands

1. Sebaceous Glands (oil)• Found all over body except palms & soles• Most are open to hair follicle• Secretes sebum (grease)

> Arrector pili muscles contract & force sebum out

> Prevent hair from becoming brittle / moisturizes skin

> Chemicals that kill bacteria• If gland is blocked, sebum backs up = Whitehead

2. Sudoriferous Glands (sweat)• Eccrine Gland

> Found all over body> Secretes H2O, salts, & little urea> Functions: helps regulate body

temperature & excretion

• Apocrine Gland> Found in axillary & pubic regions> Secretes everything eccrine does + fatty

acids & proteins> Unknown function> Odorless

– Bacteria who utilize fatty acids & proteins are not!!!!

9

B. Hair

C. Nails

• Made of protein (hard Keratin)• Protects eyes & respiratory tract• Produced by hair follicle

> Root ­ is in follicle> Shaft (dead tissue) ­ is mainly above skin

• Arrector Pili Muscle> Connects hair follicle to dermis> When cold, this contracts and stands hair upright...

• Scale­like modifications of the skin

• Colorless• Appears pink because dermis (rich in blood vessels) lies just below