Skin and Body MembranesChapter 4

2 Types of Body Membranes

A. Epithelial and B. Connective

A. Epithelial Membrane=Skin, Mucous Membrane, Serous Membrane

B. Connective Membranes=Synovial (areolar connective tissue) that has no Epithelial cells

Epithelial Membranes

A . C u ta ne o us M e m bra ne"S k in "-O n ly D ry M e m b ra ne

E p id e rm isD e rm is

B . M uco u s M e m b ra n e"W e t"L in ing E xte rio r O pe n ing

R e sp ito ry, D ig e s tiveU rin a ry, R e p rod u c tive

C . S e ro u s M e m b ran e (se ro sa)L in ing In te rio r

O ccu r in p a irs liketh e "B a llo on " exa m p le

E p ithe lia l M e m bra n es

Skin (Integument)

Wet Exterior Openings

Interior Linings

A. Cutaneous/Integument/Skin

• Waterproof-Stretchable-Washable

• Self-Repairs: Cuts, Rips, and Burns

• Electrical Insulation

• Includes: Sweat and Oil Glands, Hairs, and Nails

                        

Functions of the SkinMechanical Damage Physical Barrier

Chemical Damage Acids and Bases

Bacterial Damage Unbroken Surface, “Acid Mantle”

Ultraviolet Radiation Melanin protects from Sun

Thermal Damage Heat/Cold/Pain Receptors

Desiccation Waterproofing Surfaces

Heat Loss/Retention Skin Capillary AccessUrea and Uric Acid Excretion Perspiration

Vitamin D Sunlight

Skin StructureEpidermis

A. Stratified Squamous

B. Keratinizing (hardening)

DermisA. Dense Connective

B. Contains Blood, Sweat, and Oil Glands

HypodermisA. A.K.A Subcuaneous tissue

B. Adipose Tissue

C. Anchor Skin (E&D) to underlying organs

                                                               

3 Layers-Actual Picture

Epidermis-5 Strata (Layers)

• Corneum• Lucidum• Granulosum• Spinosum• Basale

*****OUTSIDE THE BODY*****

*****DERMIS*****

EPIDERMI S

Why can we shave (face/legs) and not bleed?

• The epidermis is AVASCULAR, meaning it has no blood supply of its own.

• Most cells produce keratin (tough, fibrous protein)

• Basale (alive with spino- and granulo-) absorbs nutrients, the top 2 (lucid- and corne-) are non-living

Then why do you bleed when you shave?

Because you cut too deeply and get into the DERMIS

The 5 Strata Layers

• Corneum:20-30 cells thick• Lucidum: dead, clear cells found only on hands/feet

• Granulosum: still living cells

• Spinosum:living cells

• Basale: absorb nutrients from the dermis to keep them alive, and “float” up to form the above 4 layers

New EPIdermis every 25-45 days

• Suntans/burns occur in the Basale

• Melanin (colored pigment)

• Basale cells phagocytize (eat) the melanin

• Melanin shields DNA from UV rays

The Dermis• Divided into 2 Layers-

Papillary and Reticular

Papillary Layer• Upper projections called papillae containing pain

and touch receptors (known as Meissner’s corpuscles)

Reticular Layer

• Contains blood vessels, sweat and oil glands and deep pressure receptors (Pacinian corpusles)

• Many phagocytes to attack bacteria that has passed through Epi-

• Collagen fibers and blood vessels