CRS101: Integumentary*

Epidermis

Most superficial layer of skin
Stratified squamous epithelium
not vascular

types of cells present in Epidermis

Keratinocytes
Melanocytes
Langerhans cells
Merkel cells

Layers of epidermis from superficial to deep

Stratum Corneum
Stratum Lucidum
Stratum Granulosum
Stratum Spinosum
Stratum Germinativum

Hypodermis(subcutaneous tissue)

made up of fat, connective tissues and larger blood vessels

Stratum Lucidum

Only present in thick skin
clear layer composed of 3-5 layers of flattened diamond shaped cells
disperses keratohyalin around keratin fibers because they both came from Stratum Granulosum

Thin skin

Found in most areas of the body
NO stratum lucidum
has hair

Thick skin

Found in areas subject to friction(palms or soles)
has all 5 epidermal layers
Dermal Papillae arranged in parallel, curving ridges known as fingerprints

Keratinocytes

Produces keratin
for structural strength
Soft keratin- skin
Hard keratin- hairs and nails

Stratum Granulosum

grainy layer
keratohyalin and keratin fibers are produced here
2-5 layers of somewhat flattened, diamond shaped cells
cells start to die here

Stratum Spinosum

Spiny layer
8-10 layers of prickle cells
prickle cells are the main foundation of Stratum Spinosum

Stratum Germinativum

where epithelial cells originate
deepest layer
Other name is "Stratum Basale"

Cell types present in Stratum Germinativum

Stem cells(basal cells)
Melanocytes
Merkel cells (touch receptors in hairless skin only)

Melanocytes

Produces melanin for skin pigmentation
For skin, eye and hair color
Protection from UV rays
Number of melanocytes same in all people
production levels differ
Melanin-brown
Carotene- Yellow

Skin color depends on 3 pigments

Hemoglobin
- reddish in tone
- pale
- bluish
Melanin
- produced by melanocytes of stratum basale
Carotene
- obtained from plant foods

Albinism

caused by genetic mutation
have little or no pigmentation in the skin, hair and/or eyes
usually present at birth
Melanocytes are present at birth but do not function properly

Vitiligo

melanocytes die
born with normal pigmentation in skin and hair but over time melanocytes die giving patchy appearance of unpigmented skin

Dermis

intermediate level of skin
in between epidermis and hypodermis
Mostly connective tissue(collagen, elastin, and reticular fibers) with
- Fibroblasts
- Adipose cells
- Macrophages

2 layers of Dermis

1. Papillary layer
2. Reticular layer

Papillary layer

project between epidermal ridges
Consists of:
- Loose connective tissue
- capillaries
- tactile receptors

Reticular layer

has dense irregular connective tissues
Irregularly arranged fibers that are resistant to stretching in every direction
Has tension lines on the skin
Has Accessory structures:
- Hair
- Glands
- Nerves
- Blood supply

Structures present in Dermis

Nerve endings
Hair follicles
Smooth muscles
Glands
Lymphatic vessels

Nerve endings in the Integumentary system(skin) and their function

Merkel's disc(for light touch)
Meissner's Corpuscles(Light touch and 2 point discrimination)
Pacinian corpuscle(Deep pressure, vibration)
Free nerve endings(Pain, Itch, light touch, temperature)
Ruffini Corpuscles(Continous touch)
Krause End Bulbs(cold)

Sensation recieved by Ruffini Corpuscles

Continous touch

Sensation recieved by Merkel's disc

light touch

Sensation recieved by Meissner's Corpuscles

Light touch and 2 point discrimination

Sensation recieved by Pacinian Corpuscles

Deep pressure and Vibration

Sensation recieved by Free nerve endings

Pain, Itch, Light touch and temperature

Sensation recieved by Krause End Bulbs

Cold

Hypodermis

Other names: Subcutaneous layer, Superficial fascia
Indistinct boundary(connective tissue fibers interwoven):

stabilization of skin while allowing independent movement

cells of hypodermis

Fibroblasts
Adipose
Macrophages

Function of Adipose

Padding, insulation gender differences in adipose tissue distribution

Accessory structures in Integumentary system

Hair follicles and hair
Glands
Nails

Glands in Integumentary system

1. Sebaceous glands
2. Apocrine glands
3. Eccrine glands

Function of Exocrine glands

Assist in thermoregulation
Excrete wastes
Lubricate epidermis

Sebaceous glands function

secretes oil that coats hair shaft and epidermis
provides lubrication and antibacterial action

Sweat

99% water
has electrolytes and organic substances
has a pH level of 4-6.8
Mainly for temp. regulation and water homeostasis

Mammary glands

Modified apocrine sweat glands
for milk production

Ceruminous glands

modified sweat glands in ears
produces waxy substance known as cerumen

What happens to skin as you age?

Dry epidermis(reduction in sebaceous and sweat gland activity)
Thin Epidermis(less vitamin D production,
reduced number of Langerhans cells)
Tendency to overheat due to less sweat gland activity
Thin dermis(loss of fibers leads to wrinkling and sagging)
Reduced blood supply(slow healing, slower ability to lose heat)
Thinner sparse hairs
Fewer Melanocytes

Arrector pili muscle

responsible for temp. regulation by causing goosebumps to close pores in the skin

Concentric layers of keratinized epithelium in hair

Medulla(soft keratin)
Cortex(hard keratin)
Cuticle

Types of hair

Velus hair(delicate hair found all over the body)
Terminal hair(coarser and deeply pigmented)
Lanugo(evident during fetal development)

White spot on base of nail

Lunula