1. Chapter 5
The Integumentary
System
Part A

2. Objectives List functions of the skin
List & describe cell structure of the different layers of the skin
Write the process of keratinization in your own words
Describe the principle of skin color
Identify and label skin structures on diagram and model
Match and select from a given list with 100% accuracy
List:
The three types of burns
Their degrees of severity
Be able to estimate the extent of damage

3. Functions of the Integumentary System
Protection:
Chemical, physical, and mechanical barrier
Body temperature regulation is accomplished by:
Dilation of dermal vessels (cooling)
Constriction of dermal vessels (warming)
Increasing sweat gland secretions to cool the body
Cutaneous sensation:
Exoreceptors sense touch and pain

4. Functions of the Integumentary System
Metabolic functions
Synthesis of vitamin D in dermal blood vessels
Blood reservoir:
Skin blood vessels store up to 5% of the body’s blood volume
Excretion
Elimination of water and salts
Elimination of limited amounts of nitrogenous wastes

5. Skin (Integument) The skin consists of two distinct regions
Epidermis:
Outermost superficial region
Dermis
Middle region below the epidermis
The hypodermis (superficial fascia)
Subcutaneous layer deep to skin
Shares some protective functions with skin
Not part of the skin

6. Reticular layer of dermis
Hair shaft
Pore
Dermal papillae
(papillary layer
of dermis)
Epidermis
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

7. Epidermis Composed of keratinized stratified squamous epithelium,
Consists of:
Four distinct cell types
Four or five layers (in palm & Sole)
Cell types include:
Keratinocytes, Melanocytes, Merkel cells, Langerhans’ cells
Avascular:
Nutrients move by diffusion thru tissue fluid from the dermis
Outer portion of the skin is exposed to the external environment ; it functions in protection

8. Cells of the Epidermis: Keratinocytes
Most abundant cell type
Arise from the continuously dividing deep layer “the stratum basale”
Produce the protective fibrous protein keratin
Pushed upward by newly formed cells underneath
Become dead keratin-containing bags at the skin free surface

9. Cells of the Epidermis: Melanocytes
Spider-shape epithelial cells
Found in the deepest layer of the epidermis
Produce membrane-bound melanin granules (melanosomes)
Melanosomes are moved along melanocyte processes to nearby keratinocytes
Melanin granules accumulate into pigment shields on the superficial side of keratinocyte nuclei
These pigment shields protect the melanocytes nuclei (DNA) from the damaging effect of UV

10. Cells of the Epidermis: Langerhans’ Cells
Star shaped cells
Also called epidermal dendritic cells
Arise in the bone marrow and migrate to the epidermis
Have a phagocytic function
Also help activate the immune system
Extend processes among keratinocytes forming a network

11. Cells of the Epidermis: Merkel Cells
Occasional cells present at the epidermal-dermal junction
Spiky hemisphere in shape
Each cell is intimately associated with a disc-like sensory nerve ending
The cell-nerve combination is called Merkel disc
Merkel disc functions as a sensory receptor for touch

12. Layers of the Epidermis
Figure 5.2b

13. Stratum Basale (Basal Layer)
Epidermis Layers:
Stratum Basale (Basal Layer)
Deepest epidermal layer
Firmly attached to the dermis
Consists of a single row of the youngest keratinocytes
Cells are in rapid division, hence the layer is named, (stratum germinativum)
10-25% of this layer are melanocytes
Occasional Merkel cells are also found

14. Layers of the Epidermis
Figure 5.2b

15. Stratum Spinosum (Prickly Layer)
Epidermis Layers:
Stratum Spinosum (Prickly Layer)
This layer is several cell layers thick
Cells contains bundles of intermediate filaments made of pre-keratin
Melanin granules are scattered among keratinocytes
Langerhans’ cells are most abundant
Keratinocytes look spiny “prickled” due to:
The shrinking of the cells during tissue preparation while dismosomes are holding tight

16. Layers of the Epidermis
Figure 5.2b

17. Stratum Granulosum (Granular Layer)
Epidermis layers:
Stratum Granulosum (Granular Layer)
Thin - three to five cell layers
keratinocyte appearance drastically changes here:
Cells flatten
Nuclei and organelles begin to disintegrate
Cells accumulate two types of granules:
Keratohyaline granules:
Help form keratin in upper layer
Lamellated granules:
Release waterproof glycolipid extracellularly
Cells “toughen” due to thickening of cytoplasm

18. Layers of the Epidermis
Figure 5.2b

19. Stratum Lucidum (Clear Layer)
Epidermis Layers:
Stratum Lucidum (Clear Layer)
Present only in thick skin (palm & sole)
Thin, transparent band
Above the stratum granulosum
Consists of a few rows of flat, dead keratinocytes

20. Stratum Corneum (Horny Layer)
Epidermis Layers:
Stratum Corneum (Horny Layer)
Outermost layer of keratinized cells
Accounts for 75% of the epidermal thickness
Functions include:
Waterproofing (exracellular glycolipid)
Protection from abrasion and penetration (keratin & thick membrane)
Relative insensitivity to biological, chemical, and physical assaults

21. Layers of the Epidermis
Figure 5.2b

22. Dermis (hide) Second major skin region Made of: Richly supplied with:
Strong, flexible connective tissue (no epithelium)
Sweat & oil glands and major portions of hair follicles reside here (although all are epidermal in origin)
Richly supplied with:
nerve fibers
blood vessels
lymph vessels

23. Dermis (cont’d) Cell types found in the dermis include:
Fibroblasts
Macrophages
Mast cells (occasionally)
White blood cells
The dermis is composed of two layers:
Papillary: thin superficial (loose areolar)
Reticular: thick deeper (dense irregular)

24. Layers of the Dermis: Papillary layer
Areolar connective tissue with collagen and elastic fibers
Superiorly is thrown into projections called dermal papillae
Various dermal papillae contain:
Capillary loops
Meissner’s corpuscles (touch receptos)
Free nerve endings (pain receptors)

25. Layers of the Dermis:
Papillary layer cont’d.
On the palms and soles, dermal papillae lie atop larger mounds called dermal ridges
Dermal ridges cause formation of epidermal ridges
Epidermal ridge patterns are unique and determined genetically
Sweat pores open along epidermal ridge crests
An individual’s fingertips leave identifying film of sweat called (fingerprints)

26. Reticular layer of dermis
Hair shaft
Pore
Dermal papillae
(papillary layer
of dermis)
Epidermis
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

27. Layers of the Dermis: Reticular Layer
Accounts for approximately 80% of dermis thickness
Made of dense irregular connective tissue
Collagen fibers add strength and resiliency to the skin
Elastin fibers provide stretch-recoil properties
Contains less dense regions called cleavage or tension lines (important for surgeons) that run in:
Longitudinal patterns in the skin of the head and limbs
Circular patterns around the skin of the trunk and neck

28. Hypodermis (Superficial Facia)
Subcutaneous layer deep to the skin
Stores fat (shock absorber)
Functions as an insulator
Anchors skin to underlying structures (usually muscles)
Composed of:
Adipose tissue
Areolar connective tissue

29. Biol
Break Slide
09/ 24/’12