What is the largest organ of the body?
Describe the weight and size of skin on the average adult male
Weighs 10-11 pounds and covers 22 square feet
What body parts have the thickest epidermis?
On palms and soles
What body parts contains the thickest dermis?
List the 4 functions of the skin
- Temperature Regulation
Describe the 4 function of skin
Protection from abrasions, fluid loss, UV radiation, harmful substances and invading microorganisms
Containment, holds in body structures and substances and prevents dehydration
Sensation: this is done by superficial nerves and sensory endings
Temperature Regulation: via sweat and dilation/construction of superficial blood vessels
What is the hypodermis contained with?
Contains with fat, sometimes large adipose cells
Name the layers of the epidermis in order of most superficial first
- Stratum corneum
- Stratum lucidum
- Stratum granulosum
- Stratum spinosum
- Stratum basale
Describe the stratum corneum
- “Horny layer”
- most superficial 20-30 cell layers
- makes up most of the thickness of the epidermis
- cells are dead and flattened and are constantly being rubbed off and replaced
Describe the stratum lucidum
- Clear layer, has mostly keratinocytes
- only present in thick skin
Describe the stratum granulosum
- 3-5 cell layers of cells
- cells are beginning to die
- I. Laminated granules contributes to waterproofing
- II. Keratonhyaline granules form keratin fibrils and contribute to toughness
What are the granules of the stratum granulosum and what are their functions?
Lamellated granules- contributes to waterproofing
Kerato-hyaline granules form keratin fibrils which contribute to toughness
Describe the stratum spinosum
Gets nourishment from vascular tissue in the dermis more division occurs here
Describe the stratum basale
Deepest layer of the epidermis
Nourishment from vascular tissue in the dermis contains stem cells that divide
Daughter cells are pushed towards the surface(remember they are first pushed from stratum basale to stratum spinosum
What is the effect of the epidermis containing melanocytes?
- Melanocytes produce melanin
- Gives the skin color and protects it from UV rays
What causes the differences in skin color?
Differences in skin color result from differences in the amount of melanin produced and how melanosomes( packets of melanin) are arranged in the keratinocytes
What occurs as the keratinocytes are pushed up through the layers of the epidermis?
As they are pushed up through the layers of the epidermis, they age and produce keratin
Before they can reach the top layer they are dead and completely with the tough protein keratin
What is the purpose of keratin?
A protein that toughens the skin
How much of the cells of the epidermis of the skin contain keratin?
About 90% of cells in epidermis are keratinocytes
How does healthy epidermis replace itself?
Healthy epidermis replaces itself in a neatly orchestrated way every month
Give a general description of the epidermis
- Contains melanocytes
What are the main structural components of the dermis ?
-Collagen: responsible for the skin’s strength
- Elastin: the main component of elastic fibers
- these give skin its elasticity- the ability to return to its original shape after stretching
What is the purpose of elastin in dermis?
Elastin is the main component of elastic fibers
-Gives skin its elasticity
How is the dermis responsible for sensation?
Contains nerve endings for pain, pressure, touch, temperature and vibration
How and why are elastin and collagen laid down?
Collagen and elastin are laid down multi-directionally. This allows them to respond to stretching, pulling, compression without damage
What is the function of the hypodermis?
Anchors dermis to underlying bone and muscle
Describe the hypodermis(subcutaneous player)
Loose connective tissue, contains adipocytes(fat cells)
Has cutaneous nerves, arteries and veins supplying skin
List the 4 glands of the integumentary system
- Merocrine(Eccrine) sweat glands
- Apocrine Sweat glands
- Sebaceous glands
- Ceruminous glands
Describe Merocrine sweat glands
- Connect to the surface of the skin by a coiled duct
- Deep in the dermis
- Found almost all over the surface of the body and are most numerous on the palms and soles
Describe Apocrine sweat glands
- Anchored deep in the dermis
- Open into the hair follicles rather than onto the surface of the skin
- Located mainly in the armpit , dental area and around the nipples of the breasts
Describe the sebaceous glands
- Most of them open into hair follicles
- Also occur in some hairless areas, such as the lips and inside the mouth
- Found all over the body except the palms, soles and top of the feet
- Most numerous on feet and scalp
Describe the ceruminous glands
- Modified sweat glands
- Located in the ear glands
Where are ceruminous glands located?
In the ear canal
Where are sebaceous glands located?
Found all over the body except on the palms, the soles and top of the feet
Where are apocrine sweat glands located?
Located mainly in the armpit, Genital area and around the nipples of the breasts
Anchored deep in the dermis
Where are Merocrine sweat glands located?
Deep in the dermis, found almost all over the surface of the body and are most numerous on the palms and soles
What glands open into hair follicles
Apocrine sweat glands and sebaceous glands
Describe the specialization of the epidermis
Arrector pili muscle- can pull hair shaft into an upright position
Sebaceous glands- produce sebum which lubricates scalp and protects hair
What causes hair color?
Due to melanin from melanocytes in the bulb of the hair follicle and then incorporated into the keratinocytes that form the hair
What about melanin leads to dark hair?
Dark hair contains the true melanin
What about melanin leads to blonde/red hair?
Results from types of melanin that contain sulfur and iron
What about melanin leads to gray hair?
When melanocytes age and lose the enzyme necessary to produce melanin
What about melanin causes white hair?
Occurs when air bubbles become incorporated into the growing hair
What causes specific hair textures?
Results from the shape of the hair shaft
What leads to straight hair?
Shape of hair shaft appears round in cross section
What leads to wavy hair?
Shape of hair shaft has an oval shape in cross section
What leads to curly hair?
Shape of the hair shaft has an elliptical or kidney-shaped cross section
From which layer of the epidermis do the nails come from?
Nails come from the stratum corneum(heavily cornified)
What is the lunula of nails?
The white appearance on nails that is due to an underlying thick layer of epidermis that does not contain blood vessels
Describe how nails grow
Nails grow as epidermal cells below the nail root and transform into hard nails that accumulate at the base of the nail , pushing the rest of the nail forward
How quickly do finger nails and toenails grow?
Fingernails Typically grow 1 mm(0.04 inches per week. Tonaails grow more slowly
What is the nail root?
The part of the nail buried under the skin
Describe the pathology of Acne
- Hair follicle becomes blocked, usually by Keratin-containing dead cells
- Sebum is prevented from reaching the surface of the skin
- Bacteria that normally live in the hair follicle breakdown the sebum behind the blockage
- This produces chemicals that cause inflammation in the surrounding skin
This results in inflammation is a pimple
What causes stretch marks?
Occur with rapid size increases like pregnancy, weight gain and growth spurts
This leads to damage in collagen fibers in the dermis
Will stretch marks go away?
Stretch marks will fade but never go away
What interesting structures are associated with skin?
Breasts (hypodermal appendage)
Some teeth in some animals