Unit 4: Integumentary System SKIN!

Skin Info. Functions (5 major) Protection Physical barrier Accounts for 15% of total body weight Includes smaller accessory organs Hair, glands, receptors, blood vessels Functions (5 major) Protection Physical barrier Regulation of body temperature Insulation, sweat glands, blood supply Communication Sensory receptors→ react to stimuli Excretion of wastes Sweat glands Vitamin D production

Three Layers Epidermis Origin of accessory organs Dermis Where most accessory organs are located Dense irregular connective tissue and blood vessels Hypodermis (subcutaneous tissue)

Epidermis Tough protective layer Contains MELANIN Protects from the sun, gives skin its color It is composed of five layers of cells...

Epidermis SURFACE Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale DEEP

Epidermis Stratum corneum The most superficial layer 20-50 rows or flattened, dead cells Normal wear and tear sheds these cells often Each “cell” contains KERATIN Important in water retention Keratin is mostly insoluble in water

Epidermis Stratum lucidum Only in thick skin Palms or hands Soles of feet 3-4 rows of flattened, dead cells, mostly transparent

Epidermis Stratum granulosum 3-5 rows of partially flattened cells Cytoplasm contains small granules Proteins turning into keratin

Epidermis Stratum spinosum Multiple layers of cuboidal cells Molecular bridges Spiny or prickly appearance Early signs of cell death No nutrients/oxygen from diffusion

***No blood supply in the epithelial tissue/epidermis!*** Stratum basale Deepest layer Single layer of columnar cells Actively dividing (alive cells) New cells pushed to surface Die as they get farther away from blood supply in the dermis ***No blood supply in the epithelial tissue/epidermis!*** (avascular)

Building diagram of the skin… starting with epidermis Draw the outline for a model of the skin to show the 3 layers: Epidermis Dermis Hypodermis *draw it big, leaving plenty of space in each layer

Fill in the details for the Epidermis Diagram the details of the epidermis: Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale For each layer: Draw the layer on your diagram Short sentence about the structure of the layer Indicate amount of blood flow Short sentence about any special molecules or functions

Dermis Made of connective tissue Vascular Blood vessels supply dermis with nourishment and remove waste Blood vessels supply the stratum basale (to support constant mitosis) *NOTICE: blood vessels don’t extend into the layers of epidermis*

Dermis Divided into two layers: Papillary Region - superficial Reticular Region - deep

Dermis - Papillary Region Loose, areolar connective tissue “Friction ridges” between dermis and epidermis strengthen the connection between the dermis and epidermis Created by projections originating in the papillary region called papillae DNA determines friction ridge patterns -- basis for unique fingerprints!

Dermis - Reticular Regions Deep to the papillary region Dense irregular connective tissue Many protein fibers! Strength, elasticity, extensibility Fibers change in response to aging, too much sun = wrinkles!!!

Fill in the details for the Dermis Diagram the details of the dermis: Papillary Region Show the friction ridges Label the type of connective tissue Reticular Region Sketch out the dense irregular connective tissue

Hypodermis Deep to the dermis Connects dermis to deeper body structure Adipose tissue and loose connective tissue Insulation (amount varies by area) shock - absorbing

Fill in the details for the hypodermis Draw in the adipose tissue Write a short few sentences about the function of the hypodermis