Integumentary System (A&P)

Integumentary system includes…

• skin / integument

• Appendages of the skin

Appendages of the skin

• oil glands

• Hair

• Sweat glands

• Nails

How much skin do you have?

• 2.2 sq meters

• 15% of your body weight

Layers of skin

• 2 layers

• Epidermis & dermis

Epidermis

• superficial layer of the skin

• Made of epithelial cells

• Outermost protective layer of the body

• Avascular

• Can be thick or thin

• Composed of 5 layers

Dermis

• deeper layer

• Makes up most of the skin

• Made of connective tissue

• Vascular

• Made of 2 layers - papillary layer and reticular layer

Subcutaneous tissue

• not part of the skin

• Deep to the skin

• Also known as hyper dermis

• Made of adipose tissue

Cells of the epidermis

• 5 layers - corneum, lucidum, granulosum, spinosum, basale

• Keratinocytes, langerhans cells / dendritic cells, melanocytes, Merkel cells

  
  

  
  

Keratinocytes

• 90% of epidermal cells

• Produces keratin - a protein that helps the epidermis protect from abrasions/penetration and remains waterproof

• Produced in the basale and pushed upward by new cells beneath them - as they approach the surface they flatten and die

• Shed millions daily

• New epidermis every 25-45 days

• Friction stimulates keratinocyte production (ex. Callus)

Langerhans cells / dendritic cells

• formed in the bone marrow and migrated to the spinosum

• Ingests foreign substances and active our immune system

Melanocytes

• spider shaped

• Produces melanin - a pigment that determines hair, skin, and eye color

• Everyone has similar numbers of melanocytes

• Melanin covers keratinocytes and blocks them from UV radiation from the Sun

• Only found in basale

Merkel cells

• present at the junction between the epidermis and dermis

• Senses light touch

Stratum Corneum

• keratinocytes are dead and shed continuously

• Outer / top layer

• 20-30 layers of squamous, anucleate keratinocytes

• Up to ¾ of the thickness of the epidermis

• Highly keratinized / cells are full of keratin

Stratum Lucidum

• keratinocytes are dead

• Clear layer

• Cells lose nuclei and die

• Only found in thick skin

Stratum granulosum

• keratinocytes are living but begin to die

• Keratinocytes begin producing granules called keratohyalin granules which help form keratin in the upper strata

• Releases lamellad bodies - releases lipids that waterproof our skin

Stratum spinosum

• keratinocytes are living

• Keratinocytes are connected by desmosomes making them appear spiny

Stratum basale

• keratinocytes are living

• Deepest epidermal layer

• Right above and attached to the dermis

• Consists of a single row of stem cells that rapidly undergo mitosis, creating keratinocytes and pushing the layers up

Papillary layer

• superficial layer

• Thin

• Top 1/5 of the dermis

Reticular layer

• deep layer

• Thick

• Bottom 4/5 of the dermis

Dermal papillae

• skin “nipples”

• Bumps that bind the epidermis and dermis

• Creates fingerprints

Meissner’s corpuscles

• sense light touch

Capillary loops

• where oxygen and nutrients are dropped off in the dermis (and shared with the epidermis)

• Where CO2 and waste are removed from the dermis

Free nerve endings

• sense pain, heat, cold, itching, and tickling

Hair follicle

• tunnel where the hair grows from

Arrector pilli muscle

• contracts to raise hair on end

• Causes goosebumps

Sebaceous glands

• oil glands

• Oil is called sebum

Sudoriferous glands

• sweat glands

Pacinian corpuscle

• sense heavy touch (pressure and vibrations)

Hypodermis

• subcutaneous layer

Adipose tissue

• adheres skin to underlying muscle (anchored loosely enough to allow skin to slide)

• Insulates heat

• Absorbs shock

Sensory nerve

• sends messages from the Merkel cells, meissners corpuscles, free nerve endings, and pacinian corpuscles to the brain

Motor nerve

• sends messages from the brain to the arrector pilli, muscles, sebaceous glands, and sudoriferous glands

Blood vessels

• delivers blood to and from the skin

• Artery = drops off blood with oxygen and nutrients

• Vein = takes away blood with CO2 and waste

Hair

• also known as pilli

• Made of dead, keratinized cells

• Located everywhere on surface on body except palms, soles, lips, nipples, and parts of the genitals

• Shaft = part of the hair above the skins surface and determines texture ( straight hair = round shaft, wavy hair = oval shaft, and curly hair = flat shaft)

• Root = part of the hair that’s embedded in the skin

• Follicle = tunnel in the skin that the hair grows from

Body hair

• senses things like insects on the skin

Scalp hair

• protects against heat loss and sunlight

Nose hair

• Filters particles in the air that we inhale

Eyelashes

• Shields the eyes from the dust and dirt

Male pattern baldness

• genetic

• More common in males

• Due to changes in testosterone

Terminal hair

• eyebrows, eyelashes, and scalp

• Darker and thicker

• Appear in the axillary (armpit) and pubic region (and face and body of males) during puberty

Vellus

• peach fuzz found on the face, arms, legs, and stomach

• Means wool

• Becomes terminal hair in males during puberty

Nail plate

• also known as the nail body

• The actual finger nail

• Made of keratin

Nail bed

• pinkish colored soft tissue under the nail plate

Free edge

• the nail tip

• Distal, free part of the nail plate

Nail root

• proximal part of the nail plate embedded in the skin

Nail matrix

• thickened proximal portion of the nail bed

• Responsible for nail growth

Lunula

• visible portion of the nail matrix

• White crescent

Eponychium

• also known as the cuticle

• Layer of clear skin along the bottom of a fingernail or toenail

Nail fold

• skin folds over the proximal and lateral borders of the nail

  
  

Glands

• an exocrine gland = gland that makes a substance and secretes them through an opening to a body surface

• 4 main types = sebaceous, sudoriferous, mammary, and ceruminous

Sebaceous glands

• oil glands

• Secretes sebum

• Found all over the body except the thick skin of the palms and soles

• Small on body and limbs and large on the face, neck, and upper chest

• Usually grow on hair follicles

• Sebum = softens and lubricates hair and skin, prevents water loss, kills bacteria

  
  

  
  

Sudoriferous glands

• sweat glands

• Everywhere on body except nipples and parts of genitals

• Up to 3 million per person

• Contraction of the glands forces sweat out to the skins surface

• 2 types = eccrine and apocrine

  
  

Eccrine glands

• more numerous that apocrine glands

• Abundant on palms, soles of feet, and forehead

• Secrete 99% water, some salt, and some traces of waste

• Prevents body from overheating

Apocrine glands

• you have approximately 2,000

• Only in axillary (armpit) and genital regions

• Larger that eccrine glands

• Water, some salt, traces of waste, and fats

• Due to fat apocrine sweat is milky and viscous

• Odorless but bacteria on skin feed on it and create body oder

• Apocrine sweat glands begin functioning at puberty

• Very little role in maintaining body temperature

• 2 types of modified apocrine glands = ceruminous glands (makes ear wax) and mammary glands (produce milk)