The Integumentary System – Skin!
Steve Bradley
Machin L. Norris
Poudre High School
Anatomy and Physiology
INTEGUMENTARY SYSTEM


Structure - Epidermal layer, Dermal layer, Subcutaneous layer
Functions
A. Regulation of body temperature – sweat, vessels dilate for heat
loss/heat retention through vessel constriction
B. Protection – keeps water and other molecules in, keeps water and
undesirable substances out
C. Sensation – detect pain, pressure, temperature, touch
D. Excretion – elimination of some nitrogenous waste, excess salt,
water (sweat/perspiration
E. Immunity - macrophages
F. Synthesis of Vitamin D – sunlight hits skin cells, cholesterol is
converted to precursor molecule that aids in absorption of Ca and P
EPIDERMIS – Stratified squamous
epithelium, first layer of skin
Cell Types:
a. KERATINOCYTES – in all five layers, more on
the outside, make keratin, sealing cells
b. MELANOCYTES – Produce melanin
c. LANGERHANS CELLS – macrophages
d. MERKEL CELLS – sensory cells
First Layer of the Integumentary System


Epidermis
Five layers of Strata
from deepest to most
superficial
a. Stratum Basale –
(Germinativum) – deepest,
single layer of cells,
only layer to undergo mitosis
(millions of new cells daily)
receives adequate
nourishment,
contains few keratinocytes,
melanocytes, Merkel cells,
as are pushed out become
more keratinized,
new turnover every 35-45
days
b. Stratum Spinosum contains keratinocytes,
Langerhans cells
arise in the bone marrow
and migrate
receives nourishment
several layers thick
does not divide
c. Stratum Granulosum –
3-5 layers of flattened
keratinocytes = water
repellent
last living layer, receives
nourishment
everything beyond this layer
is dead
d. Stratum Lucidum
Few layers of dead
keratinocytes
Found only in thickskinned areas (pads of
feet, palms of hands,
calluses – no hair
e. Stratum Corneum
20-30 layers thick of dead
keratin-filled cells,
protects against abrasion
and penetration, water
proof
Second Layer of the
Integumentary System

Dermis
1. Cells of dermis – fibroblasts,
macrophages, adipocytes.
2. Thick – palms, soles/Thin –
scrotum, eyelids
3. Dermal Papillae – produce
fingerprints, contain tactile
receptors called “Meissner’s
Corpusles.” These are nerve
endings sensitive to touch.
Dermis cont.
4. Lower Region of the Dermis
a. Consists of dense, irregular connective tissue containing
collagen and elastic fibers, adipose tissue, hair follicles,
nerves, oil glands, and the ducts of sweat glands.
b. These fibers give skin it’s strength!
Extensibility – ability to stretch (ex. Neck, Elbow “chickenskin!”)
Elasticity – the ability to return to it’s original shape after
extension or contraction (ex. Pregnancy, Tissue swelling)
c. Lamellated Corpuscles – a subcutaneous layer that is sensitive
to pressure
Skin Color and Pigmentation
A. Pigments
1. Melanin – pigment in the epidermis
2. Carotene – pigment in the dermis
3. Hemoglobin – pigment in the RBC’s ( passes thru
capillaries in the dermis)
Albinisim – the inability to produce melanocytes
1. Inherited through parents via an altered copy of genes
that does not allow the body to make the usual amount
of a pigment called melanin.
2. Melanin is a dark compound that is called a
photoprotective pigment.
3. Major role of melanin is to absorb the UV light that
comes from the sun so that the skin is not damaged.
* (see diagram 6 and 7 for inheritance)
Albinism (cont.)
4. Common eye problems resulting from albinism
a. Nystagmus – an involuntary movement of the eyes back
and forth (stand up and spin, then watch eyes. diagram 1)
b. Photophobia - sensitivity to light but, it does not
limit albinos from going out into the sunlight!
c. Strabismus – the eyes do not fixate and
track together, but they do have some depth perception
d. Iris color – usually blue/gray or light brown. The reddish
reflection comes from the retinaon the inside of the eye.
(diagram 1).
e. Unusual patterns of sending nerve signals
from the eye to the brain (diagram 3)
Malignant Melanoma
1. Melano = dark colored;
oma = tumor
2. Cancer of the Melanocytes
3. Due to the repeated exposure
of ultraviolet radiation –
amount of darkness of
melanin increases. Tanning
Beds (=) Stupid Idea!!!
Accessory Organs of the Skin –
develop from the embryo of the developing
fetus.
 Hair – Protect the
body
 Glands – help
regulate the body
 Nails – protect the
body
Hair
1. Primary function is protection, guards the scalp
from injury and the suns rays.
a. Eyebrows and Eyelashes – protect the eyes
from foreign particles.
b. Nostril hair – protects against inhaling insects
and foreign particles.
Hair - Composition
Hair is Keratinized cells, that consist of a shaft and a
root.
a. SHAFT – projects above the surface of the skin.
b. ROOT – below the surface that penetrates into the
dermis and into the subcutaneous layer.
c. HAIR FOLLICLE – composed of two layers of epidermal
cells :
External and Internal root sheaths surrounded by a
connective tissue sheath.

Anatomy of the Hair Follicle:
More Hair Composition!!!
d. BULB – onion shaped structure, contains papilla
of the hair, which have many blood vessels and
provide nourishment for the hair.
e. MATRIX – included in the bulb, produces new
hairs by cell division when older hairs are shed.
Growth cycles of the hair.
a. GROWTH STAGE –
Cells of matrix differentiate
Keratinization
Death
*New cells are added at base of root making the hair grow longer.
b. RESTING STAGE –
Growth of the hair stops, innactive matrix and shortening of hair
follicle.
c. NEW GROWTH CYCLE –
*New hair replaces old hair and old hair is pushed out of the growth
cycle.
Thought you were done…..Nope!
 Melanin –hair color is due to melanin (brown,
black, blonde). **FYI – decreased melanin
production and increased air in the hair shaft
produces grey and white hairs.
 “Canadian” Goosebumps! – due to the
contraction of the arrector pili, under stresses of
froght and cold which pull hairs into a verticle
position.
Glands
1. Sebaceous Oil Glands – secreting portion lies in the
dermis and open into the necks of hair follicles or
directly onto a skin surface.
*no sebaceous glands on the palms or soles
a. Sebum – oily secretion that ….
- Keeps hair from drying out
- Prevents excessive evaporation of water from skin
- Keeps skin soft
- Inhibits the growth of certain bacteria
Glands Again!
BLACKHEADS – accumulated sebum and
enlargement of sebaceous glands in face.
PIMPLES – sebum acts as a nutrient to bacteria
– that’s why you get the yucky puss out of them!
Glands – almost…….
2. Sudoriferous (Sweat) Glands – Two types
a. APOCRINE SWEAT GLANDS
a. armpit, pubic region, and areolae of
breasts.
b. produce sticky viscous secretion
b. ECCRINE SWEAT GLANDS – more watery secretion
during emotional stress or “cold sweat.”
a. not found in lips, nail beds, labia minora, glans
penis, and eardrums.
b. Palms and soles!!
Bad Odor (BO)
 Perspiration or Sweat (comes from the eccrine)
– functions to….
- Help regulate body temperature
- Elimination of wastes
*Antiperspirants v.s. Deodorants
“The Last of the Sweat Glands”
3. Ceruminous Glands – located in the outer ear
canal.
a. EAR WAX = cerumen (cera = wax)
*a combination of ceruminous secretions and
sebaceous glands
b. HAIRS + EAR WAX = provide a sticky barrier
against foreign bodies.
Nails
1. Structure - Plates of tightly packed, keratinized cells of
the epidermis.
a. NAIL BODY – visible portion of nail (PINK PART)
b. FREE EDGE – part that extends past the end of the
finger or toe.
c. NAIL ROOT – non-visible portion
d. LUNULA – thickened, whitish semilunar area
Near the nail root and cuticle
2. Growth of the nails
a. Occurs by transformation of superficial cells of the nail
matrix into nail cells.
b. Growth slower in toenail.
c. The longer the digit the faster the nail grows
d. The more the had used, the faster the hand nail growth.
e. Nails help us grasp and manipulate objects and provide
a protection against damage to the fingertips.