Integumentary system 2 Flashcards
Where does not hair grow?
palms, palmer surfaces of digits, soles, and plantar surfaces of the digits
hair is
dead, keratinized epidermal cells bonded together by extracellular proteins
Genetics and hormones determine thickness and pattern of distribution
Hair function (3)
- Protection (injury, sun’s rays, eyelashes and eyebrows protect eyes from foreign particles)
- Senses light touch: touch receptors in hair root plexus are activated when hair moves
- Prevents heat loss (scalp)
Structure of hair
Shaft - visible projects above the skin
Root - below the surface into the dermis and sometimes subcutaneous layer
Shaft and Root - consist of 3 concentric layers of cells (medulla, cortex, cuticle)
What surrounds the root of the hair?
hair follicle, consists of
1. external root sheath - downward continuation of the epidermis
2. internal root sheath
1+2=epithelial root sheath or hair follicle
what is at the base of each hair follicle
the bulb, nourishes the growing hair follicle
contains a germinal layer of cells called the hair matrix
Where the hair matrix cells arise from
The stratum Basale, the site of cell division
what does smooth muscle in dermis contracts with cold or fear
Arrector pili
forms goosebumps as hair is pulled vertically
What detects hair movement and senses touch
Hair root plexus
what secretes oil
Sebaceous (oil) glands
what is the three stages of hair growth cycle
Growth stage (2-6 years) matrix cells at base of hair root are active producing length
Regression stage (2-3 weeks) Cells of matrix stop dividing, hair follicle atrophies and hair stops dividing
Resting stage (3 months)
following the resting stage, a new growth cycle begins
old hair falls out as growth stage begins again
What is the normal hair loss/day
70-100 hairs/day
Types of hair in Utero
Lanugo hair: fine non-pigmented downy hair that covers the fetus
Prior to birth, Lanugo hair is replaced by
Terminal hair: coarse, heavily pigmented hair that replaces hair on eyebrows, eyelashes and scalp
Vellus hair: short fine pale hair barely visible to the human eye replaces lanugo on the rest of the body
The type of hair at puberty
Terminal hair replace vellus hair in the axillae and pubic regions of girls and boys and face, limbs, chests of boys.
Hair color is due to….
the amount and type of melanin (passed into cortex and medullary cavity)
Graying of hair occurs because of….
Progressive decline in tyrosinase and decline in melanin production
Dark hair contains
true melanin
Blond and red hair contain
melanin with iron and sulfur added
white hair is due to
lack of melanin and air bubbles in the medullary shaft
partial or complete loss of hair
Alopecia, by genes, aging, endocrine disorders, chemotherapy, skin disease
Chemotherapy kills
rapidly dividing cells such as hair matrix cells (the 15% of hairs in resting stage are not affected0
Excessive body hair or body hair in areas that are not usually experienced by females or prepubertal males
Hirsutism - caused by tumor in the adrenal glands, ovaries or testes that produce an excessive amount of androgens
Genetic predisposition where androgens inhibit hair growth
Androgenic Alopecia or male pattern baldness
nails are
tightly packed hard dead keratinized epidermal cells that form a clear solid covering over the DORSAL surfaces of the distal portion of digits
Structure of nails
- nail body: visible portion (like stratum corneum of skin)
- Free edge may extend past distal end of the digit
white, because absence of capillaries - Nail root: portion of nail buried in a fold of skin
Whiter crescent shaped area of the nail
Lunula(capillaries don’t show thickened epithelium)
Function of nails (4)
1 Protect the distal end of digits
2 provide support and counter pressure to the PALMAR surface of fingers to enhance touch perception and manipulation
3 Allow us to grasp and manipulate small objects
4 can be used to scratch and groom the body
Thickened St. Corneum beneath the free edge that secures nail to fingertips
Hyponychium or nail bed
Narrow band of epidermis that extends from and adheres to lateral side of nail wall
Epohychium or cuticle
Nail growth
Nail matrix proximal portion of the epithelium deep to the nail root who’s cells divide mitotically
grow on average 1 mm per week
4 specialized exocrine glands of the skin
Sebaceous (oil) glands
sudiferous (sweat) glands (Eccrine - most body, especially palms, soles, forehead. Apocrine - into hair follicle, groin/axillae, emotional stress and sexual excitement)
Ceruminous (wax) glands
Mammary (milk)glands
Where are sebasecous (oil) glands found
found in lips, glans penis, labia minora and tarsal glands (prevents eyelids from sticking)
small in trunk and limbs, in the dermis and opens into neck of hair follicle, produce sebum
Absent in the palms and soles
what does sebum do
contains cholesterol, proteins, fats and salts
moistens hair
water proofs and softens skin
inhibits growth of bacteria and fungi (ringworm)
sudoriferous gland function: Eccrine sweat gland
- Secretory portion in dermis with duct to surface that terminates at epidermal pores
- regulates body temperature through evaporation (perspiration), the homeostatic regulation of body temperature called “thermoregulation”
- Release sweat in response to emotional stress called “emotional sweating or cold sweat
- Help eliminate wastes
- start functioning at birth
Apocrine sweat gland function
- secretory portion in dermis with duct that opens into hair follicle
- secretions are more viscous appearing milky or yellowish
- release in response to emotional stress and during sexual activity
- apocrine sweat has musky odor aka body odor
- start functioning at puberty
Ceruminous glands function
modified sudoriferous glands found in external auditory meatus
1 produce a waxy lubricating secretion
2. the compination of ceruminous and sebaceous secretions is called cerumen
3. secretory portion is in subcutaneous layer deep to sebaceous glands
4. excretory ducts open to EAM surface or into ducts of sebaceous glands
5. Function: barrier for entrance of foreign bodies and water proof canal
bacterial inflammation of sebaceous glands
Acne
Secretions are stimulated by hormones at puberty
An abnormal amount of cerumen in the external auditory meatus or canal
impacted cerumen: can result in impaction and prevent sound waves from reaching the ear drum
Thin skin
covers all parts of the body except thick skin
lacks epidermal ridges
has a sparser distribution of sensory receptors than thick skin
hair follicles and erector pili present
Thick skin (0.6 to 4.5mm)
covers the palms, palmar surfaces of the digits and soles
features a stratum lucidum and thick epidermal ridges
lacks hair follicles, arrector pili muscles and sebaceous glands and has more sweat glands than thin skin
how many % of blood skin reserves?
8-10% in resting adults
How does skin protect the body
- Keratin - physical, chemical and biological barriers
- Tight cell junctions prevent bacterial invasion
- lipids released by lamellar granules retard evaporation
- Sebum moistens skin and hair, kill bacteria
- Acidic perspiration retards some microbe growth
- Pigment protects somewhat against UV light
- Langerhans cells alert immune system and macrophages in dermis phagocytize bacteria
Synthesis of Vitamin D
Activation of a precursor molecule in the skin by UV light
Enzymes in the liver and kidneys modify the activated molecule to produce calcitriol, most active form of vitamin D
Necessary vitamin for absorption of calcium from food in the gastrointestinal tract
Excretion and absorption
Excretes: 400 ml of water/day, small amounts salt, CO2, ammonia and Urea
Absorption: Certain lipid soluble materials - Vitamin A, D, E, K, Certain drugs, O2 & CO2, cortisone, nail polish remover, salts of lead/mercury, arsenic
method of drug passage across the epidermis and into the blood vessels of the dermis
Transdermal drug administration
Epidermal wound healing
ABRASION or MINOR BURN
- Basal cells MIGRATE across the wound
- CONTACT INHIBITION with other cells stops migration
- Epidermal growth factor stimulates basal cells to divide and replace the ones that have moved into the wound
- full thickness of epidermis
Deep Wound healing 4 phages
- Inflammatory phase: clot unite wound edges and WBCs arrive from dilated and more permeable blood vessels
- Migratory phase: begins the regrowth of epithelial cells and the formation of scar tissue by the fibroblasts (fibrin threads)
- Proliferative phase is a completion of tissue formation
- Maturation phase sees the scab fall off
skin thermoregulates by
perspiration (and its evaporation)
Shivering and constriction of surface vessels
Free nerve ending sensasions
vibration, tickle, heat, cold and pain
Touch sensation
Merkel cell
Pressure
Pacinian corpuscle
Inflammatory phase
Clots unites the wound edge
Epithelial cells migrates across the wound
Vasodilation and increased permeability of blood vessels deliver phagocytic WBC (neutrophils, macrophages) and fibroblasts
Migratory phase
epithelial cells beneath the scab bridge the wound
* Fibroblasts begin forming scar tissue along fibrin threads - GRANULATION TISSUE: collagen fibres and glycoproteins
Proliferative phase
Extensive growth of epithelial cells under scab
Fibroblasts continue to lay down collagen RANDOMLY
continued growth of blood vessels
Maturation Phase
The scab sloughs off once epidermis is restored to normal thickness
Collagen fibers become more organized
fibroblasts begin to disappear
blood vessels are restored to normal
Scar tissue formation is called
Fibrosis Collagen fibres more densely arranged Decreased elasticity Fewer blood vessels May have fewer hairs, glands or sensory structures
Excess scar tissue two types
- Hypertrophic scar stays within the boundaries of the original wound
- Keloid scar extends beyond boundaries
Epidermis develops from
Ectodermal germ layer
Hair, nail, and skin glands are
epidermal derivatives
Dermis develops from
mesenchmal mesodermal germ layer cells
what develops from mesoderm
the connective tissue and blood vessels associated with the gland
Slippery coating of oil and sloughed off skin for new born is call
vernix caseosa ( to protects fetus from amniotic fluid)
Age related structural changes
- collagen fibres decrease in number and stiffen
- Elastic fibers less elastic
- Fibroblasts decrease in number
- Decrease in number of melanocytes (gray hair, blotching)
- Decrease in Langerhans cells (decreased immune responsiveness)
- Reduced number and less efficient phagocytes
Aging and integumentary system
Most of the changes occur in the dermis
wrinkling, slower growth of hair and nails
dryness and cracking due to sebaceous gland atrophy
***subcutaneous fat is lost
Photodamage
Ultraviolet light (UVA and UVB) both damage the skin
acute overexposure causes sunburn
DNA damage in epidermal cells can lead to skin cancer
*UVA produces oxygen free radicals that damage collagen and elastic fibres and lead to wrinkling of he skin
Most common forms of skin cancer
Basal cell carcinoma
Squamous cell carcinoma
Malignant melanoma
78% of all skin cancers
basal cell carcinoma (rarely metastasize)
20 % of skin cancer
Squamous cell carcinoma (tumors in at st. spinosum) may metastasize
Most common cancer in young women
Malignant melanomas (metastasize rapidly) arise from melanocytes, life threatening, die within months of diagnosis
How to detect Malignant melanomas
A-asymmetry
B-Border
C-colour (different colors in the same place)
D-diameter (over 6 mm, pencil eraser) E- Evolving, changing size, shape and color
When AB and C present usually size is over 6 mm
Risks factors include skin color, sun exposure, family history, age and immunological status
Systematic Effects of a burn
- large loss of water, plasma, plasma protein which causes shock
- Bacterial infection
- Reduced circulation of blood
- Decreased production of urine
- Diminished immune responses
Types of burns
First degree - only epidermis
Second degree - entire epidermis and part of dermis, blisters between epidermis and dermis, but epidermal derivatives are not damaged. Heals without grafting in 3-4 weeks and may scar
Third-degree or full thickness -
- destroy epidermis, dermis and epidermal derivatives and subcutaneous layer,
- most skin functions are lost, marble, white to mahogany colored,
- marked edema and damaged area is numb due to loss of sensory nerves
What % of the body burnt, more than 50% chance to die?
exceeds 70%
Major burn (3)
a. 3rd degree burn over 10 % of body
b. 2nd degree burn over 25% of body
c. any 3rd degree burn on face, hand, feet or perineum
caused by a constant deficiency of blood to tissues overlying a bony projection that has been subjected to prolonged pressure
Pressure sore, or pressure ulcers AKA decubitus ulcers
