Epidermis Structure and Functions

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Questions and Answers

What is the primary composition of the dermis?

Collagen fibers (correct)

Adipose tissue

Epithelial cells

Striated muscle fibers

What feature allows for the mobility of leukocytes in the dermis?

Stratified layers of epithelium

Areolar tissue in the papillary layer (correct)

Dense irregular connective tissue in the reticular layer

Sebaceous glands presence

Which layer of the dermis is responsible for the formation of stretch marks?

Hypodermis

Reticular layer (correct)

Papillary layer

Epidermal layer

What type of fibers are known for providing strength and resistance to stretching in the dermis?

Collagen fibers Signup and view all the answers

What physiological feature contributes to the wavy boundary between the dermis and epidermis?

Downward waves of epidermis and upward extensions of dermis Signup and view all the answers

What property of elastic fibers allows them to return to their original length after being stretched?

They allow stretching when pulled and recoil back when released. Signup and view all the answers

What is indicated by dehydrated skin in relation to skin turgor?

It shows loss of turgor and stays pinched when tested. Signup and view all the answers

What is the primary cause of dermatitis?

Infection, radiation, and irritants affecting the papillary layer. Signup and view all the answers

What leads to the development of decubitus ulcers?

Compression of superficial blood vessels due to sustained pressure. Signup and view all the answers

Which of the following statements about skin turgor is correct?

Skin with good turgor is able to return to shape quickly after being pinched. Signup and view all the answers

What is the primary function of melanocytes in the epidermis?

To synthesize the pigment melanin Signup and view all the answers

In which layer of the epidermis are tactile cells primarily located?

Stratum basale Signup and view all the answers

Which statement about dendritic cells is TRUE?

They are immune cells that phagocytize invaders. Signup and view all the answers

What characterizes the stratum lucidum?

Is only found in thick skin Signup and view all the answers

What triggers keratinocyte multiplication to become slower?

Aging Signup and view all the answers

What happens to keratinocytes as they migrate toward the skin surface?

They flatten and produce keratin Signup and view all the answers

What primarily forms the epidermal water barrier?

Lipids from keratinocytes Signup and view all the answers

What is the main composition of the stratum corneum?

Dead, scaly, keratinized cells Signup and view all the answers

Which layers of the epidermis contain dendritic cells?

Stratum spinosum and stratum granulosum Signup and view all the answers

How long does it take for a keratinocyte to make its way to the skin surface?

30 to 40 days Signup and view all the answers

What are friction ridges primarily formed from?

Dermal papillae Signup and view all the answers

Which skin marking is characterized by an elevated, melanized patch often with hair?

Mole Signup and view all the answers

What is the primary function of the hypodermis?

Pad the body and bind skin to underlying tissues Signup and view all the answers

What condition should moles be monitored for changes in, that may suggest cancer?

Color, diameter, or contour Signup and view all the answers

Which type of skin marking is flat and melanized?

Freckle Signup and view all the answers

Which hemangioma type is often referred to as a 'strawberry birthmark'?

Capillary hemangioma Signup and view all the answers

What term describes the layer of connective tissue beneath the skin?

Hypodermis Signup and view all the answers

How does the thickness of subcutaneous fat compare among different demographics?

Thicker in females, thinner in infants and elderly Signup and view all the answers

Which type of skin cancer is the most common but least dangerous?

Basal cell carcinoma Signup and view all the answers

What is a common characteristic of squamous cell carcinoma?

Typically has a scaly appearance and can form a concave ulcer Signup and view all the answers

Where do the majority of skin cancers commonly occur on the body?

Head, neck, and hands Signup and view all the answers

Which skin cancer has the highest risk of metastasis?

Malignant melanoma Signup and view all the answers

What contributes significantly to the survival rates of skin cancer?

Early detection and treatment Signup and view all the answers

Study Notes

Melanocytes

Synthesize melanin, which protects skin from ultraviolet radiation
Located in stratum basale, but have branched processes that distribute melanin via melanosomes to keratinocytes

Tactile Cells

Touch receptor cells found in the basal layer of the epidermis
Associated with dermal nerve fibers
Merkel cell and associated nerve fiber are collectively called a Tactile/Merkel disc

Dendritic Cells

Phagocytic immune cells
Guard against toxins and microbes
Found in stratum spinosum and stratum granulosum

Layers of the Epidermis

Stratum Basale:
- Single layer of stem cells and keratinocytes
- Rests on basement membrane
- Contains melanocytes and tactile cells
Stratum Spinosum:
- Several layers of living keratinocytes
- Joined by desmosomes and tight junctions
- Contains keratinocytes that have a spiny appearance after histological preparation
- Contains dendritic cells that protect against invaders
Stratum Granulosum:
- Three to five layers of flat, living keratinocytes
- Cells start to dehydrate and die
- Contain keratohyalin granules
Stratum Lucidum:
- Thin, pale layer found only in thick skin
- Keratinocytes packed with clear protein eleidin
- Cells lack nucleus and organelles
Stratum Corneum:
- Up to 30 layers of dead, scaly, keratinized cells
- Resist abrasion, penetration, and water loss

Life History of a Keratinocyte

Keratinocytes are produced by mitosis in the stratum basale or stratum spinosum
Mitosis requires abundant oxygen and nutrients
Once cells migrate away from the dermis, mitosis stops
New keratinocytes push older ones towards the surface
Keratinocytes flatten over time, produce more keratin, and lipid-filled lamellar granules
Keratinocytes take approximately 30-40 days to reach the surface and exfoliate
Keratinocyte multiplication slows with age, but speeds up due to injury or stress
Calluses and corns are thick accumulations of dead cells on the hands and feet
Epidermal water barrier:
- Located in the stratum granulosum
- Formed from lipids from keratinocytes and tight junctions
- Helps prevent dehydration
- Doesn't prevent water absorption by stratum corneum

The Dermis

Connective tissue layer that is 0.2 mm to 4 mm thick
Composed mainly of collagen; also contains elastic and reticular fibers
Houses hair follicles, nail roots, sweat and sebaceous glands, and nerve endings
Muscles of facial expression attach to the dermis
Wavy boundary between dermis and epidermis
Dermal Papillae: Upward, finger-like extensions of the dermis
Epidermal Ridges: Downward waves of the epidermis
Papillary Layer:
- Thin layer of areolar tissue in and near the dermal papillae
- Allows for mobility of leukocytes and other defense cells
- Rich in small blood vessels
Reticular Layer:
- Deeper, thicker layer of the dermis
- Composed of dense irregular connective tissue
- Stretch Marks (Striae): Tears in collagen fibers caused by stretching
- Blisters: Form when dermal blood vessels are damaged, resulting in serous fluid leaking between the dermis and epidermis

Dermal Strength and Elasticity

Collagen fibers:
- Strong, resistant to stretching, but bends easily
- Provides flexibility
Elastic fibers:
- Permit stretching, recoils to original length when released
- Provides flexibility and stretching
Skin Turgor:
- Caused by water content in skin
- Dehydrated skin shows loss of turgor, pinched skin stays pinched after release

The Dermis 4

Dermatitis:
- Inflammation of the papillary layer
- Characterized by pain and itchiness
- Can spread rapidly across the integument
- Caused by infection, radiation, mechanical, or chemical irritation
Decubitus Ulcers:
- Bedsores caused by problems with dermal circulation
- Caused by compression of superficial blood vessels
- Common on skin covering joints or bony prominences
- Kill epithelial cells and erode dermal tissue

Skin Markings

Friction Ridges:
- Formed from dermal papillae
- Markings on fingertips that leave oily fingerprints
- Unique pattern formed during fetal development
- Enhance fingertip sensitivity and improve grip
Flexion Lines:
- Lines on the flexor surfaces of digits, palms, wrists, elbows
- Mark where skin folds during flexion of joints
Freckle:
- Flat, melanized patch
Mole (Nevus):
- Elevated, melanized patch, often with hair
- Should be monitored for changes in color, diameter, or contour, which may suggest cancer
Hemangiomas (Birthmarks):
- Patches of discolored skin caused by benign tumors of dermal capillaries
- Some disappear in childhood, some last for life
- Capillary Hemangioma (Strawberry Birthmark), Cavernous Hemangioma, Port-Wine Stain

The Hypodermis

Layer of connective tissue beneath the skin
Contains more areolar and adipose tissue than the dermis
Pads the body and binds skin to underlying tissues
Common site of drug injection (hypodermic needles)
Subcutaneous Fat:
- Refers to subcutaneous tissue primarily composed of adipose tissue
- Energy reservoir
- Thermal insulation
- Thicker in females, thinner in infants and the elderly

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Description

This quiz explores the structure and function of various cells in the epidermis, including melanocytes, tactile cells, and dendritic cells. It delves into the specific layers of the epidermis such as the stratum basale and stratum spinosum, highlighting their unique characteristics and roles in skin health.