Integumentary System Flashcards by Ordile Silver

All parts of the integumentary system

Skin
Hair
Skin glands (sebaceous, sudoriferous)
Nails

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Skin

Largest organ in the body (surface area and weight)
Ranges from 0.5mm (eyelids) to 4.0mm (heels) thick
Has 2 layers
Epidermis – superficial layer, thin, epithelial tissue
Dermis – deep layer, thicker, connective tissue

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Epidermis –

superficial layer, thin, epithelial tissue
dense and highly packed skin cells

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Dermis –

deep layer, thicker, connective tissue
The dermis is attached to the underlying fascia by a subcutaneous layer of areolar and adipose tissues

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Top layer of skin

Epidermis

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middle layer of skin

Dermis

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Deep layer of skin

subcutaneous layer

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Epidermis – Cell Types

Keratinocytes
Langerhans cells
Merkel cells
Melanocytes

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Keratinocytes

~90% of epidermal cells
Produce keratin (tough, fibrous protein) and lamellar granules (release water-resistant lipids)

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Langerhans cells

Migrate to the epidermis from red bone marrow
Contribute to the body’s immune responses

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Merkel cells

Located in the deepest layer of the epidermis
Contact specific sensory receptors (Merkel discs) that detect touch sensations

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Melanocytes

Produce melanin (pigment that absorbs UV light)
Slender projections transfer melanin to keratinocytes

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Epidermis – Structure

The epidermis has 4-5 layers of keratinocytes in various stages of development
“Thin skin” (4 layers) – covers most of the body
“Thick skin” (5 layers) – covers areas exposed to friction
(e.g., palms of the hand, soles of the feet)
Keratinocytes are formed in the deepest layer and slowly get pushed to the surface
They accumulate more keratin as they proceed and eventually undergo apoptosis (programmed cell death) before being sloughed off

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Stratum Basale

Single row of columnar keratinocytes that act as stem cells (continually undergo cell division to produce new cells)
in the deepest layer of the skin

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Stratum Spinosum

8-10 layers of many-sided keratinocytes
middle area of the skin

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Stratum Granulosum

3-5 layers of flattened keratinocytes that undergo apoptosis
Production of keratin and lamellar granules
right above the middle of skin

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Stratum Lucidum

4-6 layers of clear, flat, dead keratinocytes that have large amounts of keratin
Only present in thick skin
below the superficial layer of skin

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Stratum Corneum

25-30 layers of flat dead keratinocytes that contain mostly keratin
Superficial layers are continually sloughed off and replaced
It takes ~1 month to shed and regrow your epidermis
Therefore, you grow ~1000 skins in a lifetime
the most superficial layer of skin

Dermis

Composed primarily of a strong, flexible connective tissue network of collagen and elastic fibers
Contains few cells (e.g., fibroblasts, macrophages)
Embedded with the dermis are:
Hair follicles
Glands
Blood vessels
Tactile sensory receptors & nerve endings
(The epidermis does NOT contain any of these structures)

Papillary region

Superficial portion (thin)
Areolar connective tissue and thin collagen/elastic fibers
Projections into the epidermis called dermal papillae increase the dermal contact surface

Reticular Region

Deep portion (thick)
Dense irregular connective tissue and thick collagen/elastic fibers
Gives the skin its elasticity and extensibility

2 regions of the dermis

Papillary
Reticular

hair

Composed of circular columns of dead keratinized epidermal cells that are bonded together by proteins
Includes a:
Shaft – superficial portion that projects above the skin
Root – deep portion that penetrates into the dermis

what is the shaft and root of the hair consist of?

three concentric layers of cells
(medulla, cortex, cuticle)

what is surrounding the root of the hair?

the hair follicle Internal root sheath – cellular tubular sheath External root sheath – downward extension of the epidermis

what is surrounding the hair follicle?

a layer of dense dermis called a dermal root sheath

What is the base of a hair follicle called?

bulb, which has an indentation called a papilla

what does The papilla contain?

Hair matrix (germinal layer of cells that arise from the epidermis) Blood vessels (nourish the growing hair follicle)

Also associated with hair follicles are:

Sebaceous (oil) glands Arrector pili (smooth muscle) Hair root plexuses (nerve endings – touch sensations)

2 types of Skin Glands

Sebaceous (Oil) Glands Sudoriferous (Sweat) Glands

Sebaceous (Oil) Glands

Most open into hair follicles (some open directly onto the skin surface – e.g., lips, genitals) Absent in the palms of the hands and soles of the feet Release an oily substance called sebum, which functions to: Keep hair from drying out Prevent water evaporation from the skin Keep the skin soft and pliable Inhibit growth of some bacteria

Sudoriferous (Sweat) Glands

Release sweat into hair follicles or onto the skin surface “Eccrine sweat glands” Present in most regions of the body Sweat consists of water, ions, urea, and ammonia Main function is to help regulate body temperature “Apocrine sweat glands” Present in the axilla, groin, breasts, and face Sweat also contains lipids/proteins that are metabolized by bacteria (odour) Start to function around puberty and are stimulated by emotional stress

what are Nails

Plates of tightly packed dead keratinized epidermal cells

Nail Body

Visible portion Free edge is white due to no underlying capillaries Lunula is white due to thick epithelium in the area

Nail Root

Buried in a fold of skin Deep to the root is the nail matrix (germinal layer of cells that arise from the epidermis)

Functions of the Integumentary System

Protection Regulates body temperature Eliminates wastes Helps make vitamin D Cutaneous sensation

Functions of the Integumentary System - Protection

Keratin protects the skin and underlying tissues from the external environment (e.g., heat, microbes, chemicals) Lipids released from lamellar granules prevent water from entering or leaving the body Melanin absorbs harmful UV light Langerhans cells (epidermis) and macrophages (dermis) assist in immunity

Functions of the Integumentary System - Regulates body temperature

Evaporation of sweat

Functions of the Integumentary System - Eliminates wastes

Evaporation of sweat

Functions of the Integumentary System - Helps make vitamin D

UV light activates a precursor molecule produced in the skin

Functions of the Integumentary System - Cutaneous sensation

Touch, pain, and temperature sensations are detected by the various tactile receptors and nerve endings