2. The integument as an
organ, a
nd is an alternative name for
skin.
The integumentary system
includes the skin and the skin
derivatives hair, nails, and
glands.
The integument as an organ:
3. The Integument
Is the largest system of the body
16% of body weight,
1.5 to 2m2
in area,
The integument is made up of two parts:
1. Cutaneous membrane
a. Epidermis– Superficial epithelium
b. Dermis – underlying CT with blood supply
2. Accessory structures
a. Hair
b. Nails
c. Exocrine Glands
4. Protection
First line of defense against
Bacteria
Viruses
Protects underlying structures from
Ultraviolet (UV) radiation
Dehydration
Vitamin D production
Needed for calcium absorption
Sensation
Sensory receptors
5. Body temperature regulation
If too hot
Dermal blood vessels dilate
Vessels carry more blood to surface so heat can escape
If too cold
Dermal blood vessels constrict
Prevents heat from escaping
Excretion
Small amounts of waste products are lost through
perspiration
6. Understanding how the skin can function in these many
ways starts with understanding the structure of the 3
layers of skin
The Epidermis
Epithelial tissue
Dermis
Dense connective tissue proper – irregular
Hypodermis
Subcutaneous tissue- loose connective tissue proper
and adipose tissue
8. The Epidermis
Is a vascular stratified squamous epithelium
Nutrients and oxygen diffuse from capillaries in the dermis
Cells of the Epidermis
Keratinocytes
Contain large amounts of keratin
Are the most abundant cells in the epidermis
9. The structural relationship and
interface between the epidermis
and underlying dermis. The
proportions of the various layers
differ with the location sampled.
Dermis
Epidermis
Epidermal
ridge
Dermal
papilla
10. Thin Skin
Covers most of the body
Has four layers of keratinocytes
Thick Skin
Covers the palms of the hands and soles of the feet
Has five layers of keratinocytes
11. Structures of the Epidermis
The five strata of keratinocytes in thick skin
From basal lamina to free surface
1. Stratum basale
2. Stratum spinosum
3. Stratum granulosum
4. Stratum lucidum
5. Stratum corneum
12. Thick skin LM 210
Surface
Stratum
corneum
Stratum
lucidum
Stratum
granulosum
Stratum
spinosum
Stratum basale
Basement
membrane
DermisPapillary layer of dermis
E
P
I
D
E
R
M
I
S
13. Stratum Basale
Is attached to basement membrane by
hemidesmosomes
Forms a strong bond between epidermis and dermis
Forms epidermal ridges (e.g., fingerprints)
Dermal papillae (tiny mounds)
Increase the area of basement membrane
Strengthen attachment between epidermis and dermis
Has many basal cells or germinative cells
14. Thick skin SEM 25
Epidermal
ridge
Pores of sweat
gland ducts
Epidermal ridges
15. Stratum Spinosum — the ―spiny layer‖
Produced by division of stratum basale
Eight to ten layers of keratinocytes bound by
desmosomes
Cells shrink until cytoskeletons stick out (spiny)
Continue to divide, increasing thickness of epithelium
Contain dendritic (Langerhans) cells, active in
immune response
16. Stratum Granulosum — the ―grainy layer‖
Stops dividing, starts producing
Keratin
A tough, fibrous protein
Makes up hair and nails
Keratohyalin
Dense granules
Cross-link keratin fibers
17. Stratum Lucidum — the ―clear layer‖
Found only in thick skin
Covers stratum granulosum
Stratum Corneum — the ―horn layer‖
Exposed surface of skin
15 to 30 layers of keratinized cells
Water resistant
Shed and replaced every 2 weeks
18. The Dermis
Located between epidermis
and subcutaneous layer
Anchors epidermal accessory
structures (hair
follicles, sweat glands)
Two components
1. Outer papillary layer
2. Deep reticular layer Dermis
19. The Papillary Layer
Consists of areolar tissue
Contains smaller capillaries, lymphatics, and sensory
neurons
Has dermal papillae projecting between epidermal ridges
The Reticular Layer
Consists of dense irregular connective tissue
Contains larger blood vessels, lymphatic vessels, and nerve
fibers
Contains collagen and elastic fibers
Contains connective tissue proper
20. An inflammation of the papillary layer
Caused by
infection, radiation, mechanical irritation, or chemicals
(e.g., poison ivy)
Characterized by
itch or pain
Characteristics
Strong, due to collagen fibers
Elastic, due to elastic fibers
Flexible
22. The Hypodermis (Subcutaneous Layer)
Lies below the integument
Stabilizes the skin
Allows separate movement
Made of elastic areolar and adipose tissues
Connected to the reticular layer of integument by
connective tissue fibers
Deposits of Subcutaneous Fat
Distribution patterns determined by hormones
Reduced by cosmetic liposuction (lipoplasty)
23.
24. The Hair Follicle
Hair follicles are the organs that form the hairs.
Hair follicles are the organs that form the hairs.
Located deep in dermis.
Produces nonliving hairs.
Wrapped in a dense connective tissue sheath.
Base is surrounded by sensory nerves (root hair plexus).
Control bacteria
26. Regions of the Hair
Hair root
Lower part of the hair
Attached to the integument
Hair shaft
Upper part of the hair
Not attached to the
integument
Boundary
between
hair shaft
and
hair root
Hair shaft
Sebaceous
gland
Arrector
pili muscle
Hair root
Connective
tissue sheath
Hair bulb
Hair matrix
Hair papilla
27. Hair Shaft Structure
Medulla
Core, dead cells contain soft keratin and air to provide
flexible
Cortex
Middle layer, dead cells contain hard keratin to provide
stiffness
Cuticle
Outermost, overlapping dead keratinized cells form
shiny surface
28. Head:
UV protection
Cushion from trauma
Insulation
Nostrils, Ear canals, Eyelashes:
Prevent entry of foreign material
Body Hair:
sensory detection
Root hair plexus:
Sensory nerves at base of hair follicle that detect slight
movement of hair
Arrector pili muscle:
Attached to every hair follicle
Contract to stand hair perpendicular to skin surface
29. Nails
Protect fingers and toes
Made of dead cells packed with
keratin
Metabolic disorders can change
nail structure
Nail Production
Occurs in a deep epidermal fold
near the bone called the nail root
Free edge
of Nail
Body of
Nail
Laternal
Nail fold
Lunula
Eponychium
(cuticle)
30. Structure of a Nail
Nail body
The visible portion of the nail
Covers the nail bed
Lunula
The pale crescent at the base of the nail
Sides of nails
Lie in lateral nail grooves
Surrounded by lateral nail folds