Transcript Integumentary System

Integumentary
System
Skin as an Organ
• Largest organ in human body
• All adults have 20-25 lbs of skin
• 4 Functions- Skin as radiator
Integumentary Structures
• Components of the Integumentary System
Figure 5-1
Quick Overview
Epidermis
• Tissue= Stratified Squamous
• No blood vessels in this layer
• Dead Skin Cells
Dermis
• Tissue=Dense Irregular Collagenous Connective
• Active area of skin
Hypodermis (not actually skin)
• Tissue=Areolar & Adipose
• Connects skin to body
(Epi=On, On the surface of something)
(Hypo=Below, Less than)
4 Major Structures in Dermis
1. Hair Follicles• All anchored in dermis
• Aid in temp regulation by trapping air to help
insulate.
• Sensitive-Can sense vibrations
2. Glands
• Sweat Glands-Evaporation cools you
• Oil Glands-Keep dead skin cells together. Protects
from things getting in. (sebaceous gland)
4 Major Structures in Dermis
3. Blood Vessels
• Bring nutrients and fluids to cells.
• Bleed when you cut into dermis (not epidermis).
4. Sensory Nerves
• Sense Temperature
• Pain
• Touch (Meisners Corpuscle-Light Touch; Pacinian
Corpuscle-Deep pressure)
Hypodermis
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Link Between Body & Skin
Find adipose mixed in with areolar tissue
Most fat in your body is directly under skin.
Major blood vessels
Dermis
• Boundary between dermis
& epidermis isn’t flat to
prevent slipping apart.
• Dermal Papilla-Bumps in
dermis
• Blisters caused by intense,
prolonged friction.
Epidermis separates from
dermis and fluid enters.
• Any change to dermis will
be seen through epidermis
(scars, surface contours,
etc)
• Scars are in dermis
• Causes Fingerprints
Dermal
Papilla
Blisters
Epidermis
• Super thin
• Stratified Squamous
• 5 Layers
Living Layers!
– Stratum Corneum
– Stratum Lucidum (Only Soles of Feet &
Palms)
– Stratum Granulosum
– Stratum Spinosum
– Stratum Basale
Started from the bottom now we’re
here..Stratum Basale (hehehe)
• All other cells come from
here
• #1 Job is ReproductionCells born here aren’t in
full production mode
yet, they don’t grow up
here.
Stratum Basale (cont)
• 2 Main types of cells in
Stratum Basale
– mostly Keratinocytes:
Make protein- keratin to
give epithelium strength.
Don’t produce keratin yet in
basale layer.
– Melanocytes: Make
pigment melanin (colors
your skin). More
Melanin=darker skin.
• Albinism=Malfunctioning
melanocytes
Stratum Spinosum
• Cells from basale
go here.
• Cells here are
growing up and
producing keratin,
etc. Like teenagers.
Stratum Spinosum (cont)
• Melanocytes don’t
reproduce in numbers.
When they
do=melanoma
(malignant skin cancer)
• Melanin-natural
sunblock
– Absorbs UV Rays, blocks
UV rays from damaging
dermis.
– Tanning occurs by UV
radiation stimulating
excess melanin
production.
Stratum Granulosum
• Old cells
• Been producing
keratin for so long,
we can see keratin
“GRANULES”
• Not much
moisture/nutrient
s
• Cells on the verge
of death.
Stratum Corneum
• Top layer
• Dead skin cells
• Still tough because
of protein keratin.
Stratum Lucidum
• Palms/Soles of
Feet
• Less
melanocytes,
decreased
pigment
• Change from
granulosum
before
corneum to
thicken.
Sebaceous
Glands
(oil
glands)
• Occur over entire body - Except palms and soles
• Simple alveolar glands
– Holocrine secretion – entire cell breaks up to form secretion
– Secretes an oily substance called sebum
– Most are associated with a hair follicle
• Functions of sebum
– Softens and lubricates hair and skin
– Skin waterproofing
– Collects dirt
Sweat (Sudoriferous) Glands
• Two types:
• Eccrine (Merocrine)
– Most abundant sweat gland
– “True sweat”
• 99% water with some salts
• Contains traces of
metabolic wastes ~ 2%
urea
– Role in thermoregulation
– Widely present in skin (up to
500/cm2)
• Apocrine
– Odorous secretion
– Absent before puberty
– Present in axillary, areolar,
anal and genital areas
Eccrine (Merocrine) Gland
Figure 5.10b
Nails
• Scalelike modification of epidermis made of hard keratin
• Parts of the nail
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–
–
–
–
Free edge
Body - dense mass of keratinized cells
Root
Nail folds
Eponychium – cuticle
Skin Injury and Repair
Bleeding occurs at the site of injury
immediately after the injury, and mast cells in
the region trigger an inflammatory response.
Epidermis
After several hours, a scab has formed and cells
of the stratum germinativum are migrating
along the edges of the wound. Phagocytic cells
are removing debris, and more of these cells
are arriving with the enhanced circulation
in the area. Clotting around the edges
of the affected area partially isolates
the region.
Scab
Dermis
Sweat
gland
Migratory
Macrophages epithelial
cells
and
fibroblasts
Granulation
tissue
Skin Injury and Repair
One week after the injury, the scab has been
undermined by epidermal cells migrating over
the meshwork produced by fibroblast activity.
Phagocytic activity around the site has almost
ended, and the fibrin clot is disintegrating.
After several weeks, the scab has been shed,
and the epidermis is complete. A shallow
depression marks the injury site, but fibroblasts
in the dermis continue to create scar tissue that
will gradually elevate the overlying epidermis.
Scar
tissue
Fibroblasts
Skin Injury and Repair
Table 5-1
Aging of the Skin
• Major Age-Related Changes
– Injury and infection increase
– Immune cells decrease
– Sun protection diminishes
– Skin becomes dry, scaly
– Hair thins, grays
– Sagging, wrinkles occur
– Heat loss decreases
– Repair slows
Effects of UV Radiation
• Beneficial effect - activates synthesis of
vitamin D3
• Harmful effects
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–
–
–
Sun burn
Wrinkles, premature aging
Malignant melanoma
Basal cell carcinoma
Types and Growth of Hair
• Vellus hairs
– Body hairs of women and children
• Terminal hairs
– Hair of scalp
– Axillary and pubic area (at puberty)
• Hair thinning and baldness
– Due to aging
– Male pattern baldness
Burns
• Classified by severity
– First-degree burn – only upper epidermis is
damaged
– Second-degree burn – upper part of dermis
is also damaged
• Blisters appear
• Skin heals with little scarring
– Third-degree burn
• Consume thickness of skin
• Burned area appears white, red, or blackened
Burns
First-degree
(epidermis only; redness)
Second-degree
(epidermis and dermis,
with blistering)
Third-degree
(full thickness, destroying
epidermis, dermis, often part
of hypodermis)
Estimating Burns Using the Rule of
Nines
Figure 5.11a
Skin Cancer
• Basal cell carcinoma
– Least malignant and most common
• Squamous cell carcinoma
– Arises from keratinocytes of stratum spinosum
• Melanoma
– A cancer of melanocytes
– The most dangerous type of skin cancer
Skin Cancer
Squamous
Squamouscell
cellcarcinoma
carcinoma
Basal cell carcinoma
Melanoma
Figure 5.12
The Skin Throughout Life
• Epidermis
– Develops from embryonic ectoderm
• Dermis and hypodermis
– Develop from mesoderm
• Melanocytes
– Develop from neural crest cells
The Skin Throughout Life
• Fetal skin
– Well formed after the fourth month
– At 5-6 months
• The fetus is covered with lanugo (downy hairs)
– Fetal sebaceous glands produce vernix
caseosa