1. The Integumentary System5
The Integumentary System

2. Integumentary System 1 8 2 9 3 7
Get the skinny here….. 4 5 6

3. The Skin = The Cutaneous Membrane
Skin (Integument)
The Skin = The Cutaneous Membrane
Consists of three major regions
Epidermis – outermost superficial region (stratified squamous epithelial tissue) - lacks blood supply.
Dermis – middle region (dense irregular connective tissue with muscle & nervous tissue) - collagen & elastic fibers - binds the epidermis to underlying tissues
Hypodermis or subcutaneous layer (superficial fascia) – deepest region (adipose tissue with nervous tissue & blood vessels) - Binds dermis to organs and blood vessels

4. Integumentary Functions
Overall Function: Maintaining Homeostasis (what else?)
Temperature regulation
Protection of underlying tissues.
Retardation of water loss
Sensory Reception
Synthesizing certain chemicals
Excreting wastes.

5. Integumentary Functions Memory Tool
WeT PETS – Visualize a dog with these features:
Water bowl: Reduce water loss
Petting the dog: Touch
Guard dog: Protection
Dog doo: Excretion
Panting: Temperature regulation
Food bowl: Synthesis of needed molecules
Good dog, Dermo!!

6. Covers 7600 sq. cm in average adult. 7% of body weight.
The Largest Organ
Covers 7600 sq. cm in average adult.
7% of body weight.
Varies in thickness- .5 mm to 2 mm.
Composed of many tissues:
Hair Epithelial
Nerves Adipose
Smooth Muscle Blood
Glands

7. Epidermis Hair shaft Pore Dermal papillae (papillary layer of dermis)
Meissner's corpuscle
Free nerve ending
Reticular layer of dermis
Sebaceous (oil) gland
Dermis
Arrector pili muscle
Sensory nerve fiber
Eccrine sweat gland
Pacinian corpuscle
Hypodermis
(superficial
fascia)
Artery
Vein
Hair root
Adipose tissue
Hair follicle
Eccrine sweat
gland
Hair follicle receptor
(root hair plexus)
Figure 5.1

8. Epidermis
Composed of keratinized stratified squamous epithelium, consisting of four distinct cell types and four or five layers
Cell types include keratinocytes (squamous cells), melanocytes, Merkel cells, and Langerhans’ cells
Outer portion of the skin is exposed to the external environment and functions in protection

9. Cells of the Epidermis (Listed in order of importance!)
Keratinocytes – produce the fibrous protein keratin, which makes the skin waterproof (most common cell of epidermis - squamous)
Melanocytes – produce the brown pigment melanin (causes skin color for UV protection – amoeboid shape)
Merkel cells – function as touch receptors in association with sensory nerve endings
Langerhans’ cells – epidermal macrophages that help activate the immune system (amoeboid shape and activity)

10. Cells of the Epidermis
Figure 5.2b

11. Layers of the Epidermis
Stratum Basale
Stratum Spinosum
Stratum Granulosum
Stratum Lucidum
Stratum Corneum
Deep
Superficial

12. Layers of the Epidermis

13. A Mnemonic for the Layers of the Epidermis:
Corneum
Lucidum
Granulosum
Spinosum
basale BS
Grows
Lots of
Corn!!

14. Layers of the Epidermis
Two major processes occur in the epidermis: mitosis and keratinization
Mitosis occurs in the deepest layer (stratum basale), where new cells are continually formed to replace old, dead cells that have sloughed off of the most superficial layer (stratum corneum)
Keratinization occurs in the intermediate layers, as the cells age and accumulate large quantities of the protein keratin, becoming a waterproof protective layer in the stratum corneum when the cells die
Figure 5.2b

15. Layers of the Epidermis: Stratum Basale (Basal Layer)
Deepest epidermal layer firmly attached to the dermis
C onsists of a single row of the youngest keratinocytes
C ells undergo rapid division (mitosis), hence its alternate name, stratum germinativum

16. Layers of the Epidermis: Stratum Spinosum (Spiny Layer)
As the young cuboidal keratinocytes begin to form keratin fibers, the lengthening fibers stretch the cell membranes, forming spiny projections
Cells joined together by desmosomes

17. Layers of the Epidermis: Stratum Spinosum (Prickly Layer)
C ells contain a weblike system of intermediate filaments attached to desmosomes
Desmosomes: anchoring junctions between cells – they connect cells securely in areas subjected to stress, like skin and cardiac muscle
Intermediate filaments stretch across the interior of the cell from one desmosome to another, forming part of the cytoskelton
Melanin granules and Langerhans’ cells are abundant in this layer
C ell membranes

18. Layers of the Epidermis: Stratum Granulosum (Granular / Grainy Layer)
Thin; three to five cell layers in which drastic changes in keratinocyte appearance occurs
Keratohyaline and lamellated granules accumulate in the cells of this layer – gives the cells a granulated, or spotty, appearance

19. Layers of the Epidermis: Stratum Lucidum ( Clear Layer)
Thin, transparent band superficial to the stratum granulosum
Consists of a few rows of flat, dead keratinocytes
Clear because nuclei, organelles, & membrane no longer visible
Present only in thick skin (palms and soles)

20. Layers of the Epidermis: Stratum C orneum (Horny Layer)
Outermost layer of completely keratinized cells
Accounts for three quarters of the epidermal thickness
Functions include:
Waterproofing
Protection from abrasion and penetration
Rendering the body relatively insensitive to biological, chemical, and physical assaults

21. Layers of the Epidermis
Figure 5.2b