Integumentary System
BIOL241
Lab #7
Overview of the Integumentary
System
Organization of the Epidermis:
Figure 5–2
Layers of the epidermis are known
as “strata”
Layers of the Epidermis
Top: Free surface of skin
- stratum corneum
- stratum lucidum
- stratum granulosum
- stratum spinosum
- stratum germinativum
Bottom: Basal lamina
A note on thick vs. thin skin
• Thick skin has an
extra layer (lucidum)
but that is NOT the
reason that it is thicker
than thin skin.
• Real reason is the
other layers are
thicker in thick skin
than in thin skin.
The Dermis
• Deeper part of cutaneous layer
• Located between epidermis and
subcutaneous layer
• Anchors epidermal accessory structures
(hair follicles, sweat glands)
• Has 2 components:
– outer papillary layer
– deep reticular layer
The Papillary Layer
• Consists of areolar tissue
• Contains smaller capillaries, lymphatic
vessels, and sensory neurons
• Has dermal papillae projecting between
epidermal ridges
The Reticular Layer
• Consists of dense irregular connective
tissue
• Contains larger blood vessels, lymph
vessels, and nerve fibers
• Contains collagen and elastic fibers
Integumentary
Accessory Structures
• Hair, hair follicles, sebaceous (oil) glands,
sweat glands, and nails:
– are derived from embryonic epidermis
– are located in dermis
– project through the skin surface
The Hair Follicle
• Is located deep in dermis
• Is made of epidermal tissue (with
connective tissue around the outside)
• Produces nonliving hairs
• Is wrapped in a dense connective-tissue
sheath
• Base is surrounded by sensory nerves
Hair
Structures of Hair and Follicles
Figure 5–9a
Accessory Structures of Hair
• Arrector pili:
– involuntary smooth muscle
– causes hairs to stand up
– produces “goose bumps”
• Sebaceous glands:
– lubricate the hair
– control bacteria
Inside the
Follicle
Figure 5–9b
Exocrine Glands in the skin
• Sebaceous glands and follicles (oil
glands):
– holocrine glands
– secrete sebum
• Sweat glands:
– merocrine glands
– watery secretions
Types of Sebaceous Glands
• Sebaceous glands:
– associated with most hair follicles (on head
and body)
• Sebaceous follicles:
– discharge directly onto skin surface
– found on face and trunk
– when clogged  acne
Sebaceous glands
Types of Sweat Glands
• Apocrine:
– found in armpits, around nipples, and groin
• Merocrine:
– more numerous, widely distributed on body
surface
– especially on palms and soles (thick skin)
 Both are actually merocrine
“Apocrine” Sweat Glands
• Merocrine secretions, not apocrine
• Associated with hair follicles in groin,
nipples, and axillae (armpits)
• Become active at puberty
• Produce sticky, cloudy secretions (thick
sweat) that breaks down and causes odor
Merocrine Sweat Glands
• Also called eccrine glands:
– coiled, tubular glands
– discharge directly onto skin surface
– sensible perspiration for cooling (thin sweat)
– water, salts, and organic compounds
Sweat Glands of the Skin
Merocrine
Apocrine
Epidermis
What to look for:
• Usually darkest between stratum
germinativum and stratum granulosm
(granulosm often a dark meandering line)
• Keratinized cells (s. corneum) often lift off
the underlying layers
• S. germinativum along basal lamina, along
with melanocytes
Dermis: Papillary vs. Reticular layer
What to look for
• Papillary layer
– has ridges
– is areolar
– Just under basal lamina
• Reticular layer
– much thicker
– Dense irregular CT
• Hypodermis
– Loose CTP
More skin
Merocrine sweat gland
• What to look for
– Found in most skin
– Coiled, tubular
– Small lumens in cross
section
– Have duct that goes all
the way to the
epidermal surface and
ends in sweat pore
– Smaller than apocrine,
don’t extend as deep
into dermis
Apocrine sweat gland
What to look for:
• Associated with
hair follicle
• Only in nipples,
groin, armpit
• Large lumens
• Deeper in dermis
than merocrine
Apocrine sweat gland
Hair with
sebaceous
glands and
arrector pilli
Hair
What to look for:
• Follicles are rarely complete
• Can often see root, papilla at base of hair
• Arrector pilli muscle at an angle
• Associated glands (which are?)
Sebaceous
glands
Sebaceous glands
What to look for:
• Associated with hair follicle
• Found most everywhere hair follicles are
found in skin
• Look like cauliflower (maybe?)
Sebaceous follicle
Sebaceous follicle
What to look for:
• Also look like cauliflower
• Found on face and trunk only
• NOT associated with hair follicle
• Have duct that opens onto skin surface
Lab Activity #7
• Look at slides:
– Axillary skin (armpit)
– Pigmented and Nonpigmented thin skin slide
– Scalp
What will you find there?
Armpit
– Hair?
– Hair follicle?
– Sebaceous gland?
– Sebaceous follicle?
– Apocrine sweat gland?
– Merocrine sweat gland?
Scalp
Y
Y
Y
Y
Y
?
Y
N
Y
N
Y
Y
Pigmented Thin Skin
• Find:
– Epidermis
• Identify layers, starting with germinativum
• Find melanocytes
– Dermis
• Papilary and reticular CT layers
– Hypodermis
Axillary skin
• Locate:
– an apocrine sweat gland.
– a merocrine sweat gland
– also look for a sebaceous follicle (not
associated with a hair)
Turn in one drawing page with…
• Three types of glands (one sebaceous, a
merocrine sweat gland and an apocrine
sweat gland)
• Epidermis (label the four layers)
• Dermis (label papillary and reticular)
• Hair follicles and shaft (label follicle,
sebaceous gland, arrector pilli muscle if
seen)
Assignment
• For Next Monday turn in:
– Your drawing
– Review Sheet #7 (you do not have to do the
parts about plotting sweat glands and
fingerprinting on page 104)