Integumentary System Flashcards
All parts of the integumentary system
Skin
Hair
Skin glands (sebaceous, sudoriferous)
Nails
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
Epidermis –
superficial layer, thin, epithelial tissue
dense and highly packed skin cells
Dermis –
deep layer, thicker, connective tissue
The dermis is attached to the underlying fascia by a subcutaneous layer of areolar and adipose tissues
Top layer of skin
Epidermis
middle layer of skin
Dermis
Deep layer of skin
subcutaneous layer
Epidermis – Cell Types
Keratinocytes
Langerhans cells
Merkel cells
Melanocytes
Keratinocytes
~90% of epidermal cells
Produce keratin (tough, fibrous protein) and lamellar granules (release water-resistant lipids)
Langerhans cells
Migrate to the epidermis from red bone marrow
Contribute to the body’s immune responses
Merkel cells
Located in the deepest layer of the epidermis
Contact specific sensory receptors (Merkel discs) that detect touch sensations
Melanocytes
Produce melanin (pigment that absorbs UV light)
Slender projections transfer melanin to keratinocytes
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
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
Stratum Spinosum
8-10 layers of many-sided keratinocytes
middle area of the skin
Stratum Granulosum
3-5 layers of flattened keratinocytes that undergo apoptosis
Production of keratin and lamellar granules
right above the middle of skin
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
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
