Integumentary (Slides 1-19 Exam 1) Flashcards
What two things is the integument system composed of?
- Skin (Cutaneous membrane or integument)
- The derivatives of skin
- Hair, sweat glands, sebaceous glands, ceruminous glands, nails
What is the hypodermis?
- Not a part of the skin, but is studied with the skin
- Composed of adipose connective tissue and areolar connective tissue
What two layers make up the skin?
- Epidermis (epithelial cells)
- Dermis (Connective tissue)
The skin is considered the largets organ in the body, it makes up _____% of body weight.
7-8%
The epidermis contains 4-5 layers depending on location, name them from deepest to most superficial.
- Stratum basale
- Stratum spinosum
- Stratum granulosum
- Stratum lucidum (only found in thick skin)
- Stratum corneum
The dermis has two layers, what are they and what differentiates them?
- Papillary layer
- Interdigitation between epidermis and dermis
- Epidermal ridges and dermal papilla
- Interdigitation between epidermis and dermis
- Reticular layer
- Capillaries
- Sweat glands
- Nerve endings
- Hairs
What cells is the epidermis primarily composed of?
- Keratinocytes
- More superficial layers are composed of keratinized stratified squamous epithelium
Which layers of the epidermis contain living keratinocytes?
The deepest 3 layers
- Stratum basale
- Stratum spinosum
- Stratum granulosum
Which layers of the epidermis contain dead keratinocytes?
The most superficial two layers
- Stratum lucidum (only in thick skin and deep to the stratum corneum)
- Stratum corneum
Describe the Stratum basale layer of the epidermis
- Deepest epidermal layer
- Single layer of cuboidal cells (may also have low columnar cells)
- Attached to a basement membrane
- Separates the epidermis form the dermis
- Contains sensory nerve endings for pain and temp
- Contains three cell types
What are the three cell types found within the Stratum basale layer of the epidermis?
- Keratinocytes
- Melanocytes
- Tactile cells (Merkel cells)
Describe keratinocytes in the Stratum basale
Many keratinocyte stem cells that divide to regenerate new cells, replace old cells shed from the surface of the skin.
As the keratinocytes divide they push the newly formed cells upward towards the surface.
What do melanocytes do?
- Produce and store pigment (melanin) in response to UV light.
- Transfer pigment granules into keratinocytes which accumulate around the nucleus of the keratinocyte sheilding its DNA from UV radiation.
- Responsible for darker skin tones
What do tactile cells (Merkel cells) do?
- Are modified nerve endings
- Sensitive to touch, when compressed, release chemicals to stimulate sensory nerve endings.
What does the stratum spinosum layer of the Epidermis contain?
- Also called the spiny layer
- Contains several layers of polygonal keratinocytes
- Daughter cell from the keratinocyte stem cells in the stratum basale
- Pushed into the stratum spinosum
- Become specialized, non-dividing, keratinocytes
- Some still divide in the deepest layers of the stratum spinosum
- Daughter cell from the keratinocyte stem cells in the stratum basale
- Contains sensory nerve endings for sensing pain and temperature
- Contain epidermal dendritic cells (Langerhans cells)
What are epidermal dendritic cells (Langerhans cells) responsible for? What layer of the epidermis are they found in?
- Immune cells that help initiate immune responses
- Responsive to pathogens and epidermal cancer cells
- Found in the stratum spinosum layer of the epidermis.
Describe the stratum granulosum layer of the epidermis
- 3-5 layers of keratinocytes
- First layer of keratinization
What is keratinization? Which layer of the epidermis does this process start?
- Process where keratinocytes fill with keratin
- Causes nucleus and organells to disintegrate
- Fully keratinized cells are dead but maintain their structure
- Proccess starts in the stratum granulosum layer but is not completed until keratinocyte reaches more superficial layers.
Describe the Stratum lucidum layer of the epidermis
- 2-3 layers of keratinocytes
- Found only within thick skin
- Appears transulcent because keratinocytes are filled with a transulcent protein, eleidin.
What is eleidin?
- A translucent protein that is an intermediate product in keratin maturation.
- Found in keratinocytes undergoing keratinization in the stratum lucidum
The stratum lucidum layer of the epidermis is only found within “thick” skin, where is thick skin located
- Palms of hands
- Surface of fingers (Part of what makes up our fingerprints)
- Soles of feet
- Toes
Describe the stratum corneum layer of the epidermis
- Also known as the hornlike layer
- Several layers of dead, interlocking keratinized keratinocytes
- The keratinocytes are anucleate
- Most superficial layer of the epidermis
- Surface is dry and unsuitable for growth of many microorganisms
- Secretions from exocrine glands (sweat glands) helps prevent microbial growth
From when a keratinocyte is first made in the stratum basale, to when it has reached the stratum corneum as a keratinized keratinocyte, takes how long? How long does the keratinocyte remain in the stratum corneum before it is shed from the body?
2 weeks
Describe thick skin
- Located on the palms of hands, soles of feet, surfaces of fingers, and toes
- Has all 5 layers of epidermal strata
- Has sweat glands
- Lacks hair follicles and sebaceous glands
- 0.4-0.6 mm thick
Name the five layers of thick skin
- Stratum basale
- Stratum spinosum
- Stratum granulosum
- Stratum lucidum
- Stratum corneum
How thick is thick skin?
0.4-0.6 mm
Describe thin skin
- Covers most of the body
- Lacks stratum lucidum
- Has sweat glands, hair follicles, and sebaceous glands
- 0.075-0.150 mm thick
What are the four layers of thin skin?
- Stratum basale
- Stratum spinosum
- Stratum granulosum
- Stratum corneum
How thin is thin skin?
0.075-0.150 mm
What are the two main causes of variation in skin color?
- Coloring from Hemoglobin
- Coloring from Melanin
How does hemoglobin affect skin color?
- Reddish tint due to the presence of hemoglobin in blood vessels of the dermis
- More visible if blood vessels dilate
How does melanin affect skin color?
- Is a pigment with black, brown, tan, yellow-brown shades
- Amount in skin varies according to heredity and light exposure (UV light stimulates production of melanin)
- Everyone has the same number of melanocytes (cells that produce melanin)
- Activity of melanocytes and color of melanin vary among individuals
- Darker skinned people produce more melanin with a darker shade.
- Activity of melanocytes and color of melanin vary among individuals
Describe the mechanism of a suntan? This is a long one, I just copied it from her slide.
- Exposure of skin to UV light
- Keratinocytes experience DNA damage and increase p53 activity (tumor suppressor gene: regulates cell cycle, prevents gene mutations)
- P53 stimulates a cascade that releases Corticotropin Releasing hormone (CRH) which stimulates POMC (pro-opiomelanocortin)
- POMC is broken down to form a-MSH (Melanin Stimulating Hormone) in the pituitary
- a-MSH in the blood stream binds to receptors on melanocytes (MC1R) stimulating 2nd messenger cAMP
- cAMP stimulates Melanocytes to increase production of melanin
- Melanin is packaged in vesicles & exocytosed into interstitial fluid
- Melanin enters keratinocyte
- Melanin migrates to nucleus of keratinocyte (protecting DNA from further damage)
- As keratinocytes move toward the surface they die & leave a layer of melanin in the dead cells
- Melanin in the Stratum Corneum cells provides both the color of a suntan and further UV protection to underlying layers
Describe melanocytes function
UV light damages keratinocyte nuclei, which causes them to release signals which travel to the melanocytes. The signals cause the melanocytes to increase production of melanin, package up the melanin and send it to the keratinocyte. At the keratinocyte the melanin enters the cytosol of the keratinocyte and surrounds the nuclei. The melanin acts like a shield that prevents UV light from further damaging the keratinocyte nucleus.
