Chapter 5: Integumentary System Flashcards
Functions of the Integumentary System- PROTECTION
-3 types of barriers
Chemical:
*Low pH secretions (acid mantle) and defensins retard bacterial activity
Physical/mechanical barriers:
- Keratin and glycolipids block most water and water- soluble substances
- Limited penetration of skin by lipid-soluble substances, plant resins (e.g., poison ivy), organic solvents, salts of heavy metals, some drugs
Biological barriers
*Dendritic cells, macrophages
Functions of the Integumentary System- BODY TEMPERATURE REGULATION
~500 ml/day of routine perspiration (at normal body temperature)
At elevated temperature, dilation of dermal vessels and increased sweat gland activity cool the body
Functions of the Integumentary System- CUTANEOUS SENSATIONS
-Temp, touch (merkel, meissner cells), and pain (free nerve endings)
Functions of the Integumentary System- METABOLIC FUNCTIONS
-Synthesis of vitamin D precursor and collagenase (increases collagen and reduces wrinkles)
Chemical conversion of carcinogens and some hormones
Functions of the Integumentary System- BLOOD RESERVOIR
Up to 5% of body’s blood volume
Functions of the Integumentary System- EXCRETION
Nitrogenous wastes and salt in sweat
Consists of 3 major regions
- Epidermis: superficial region
- Dermis: middle region
- Hypodermis: deepst region
* Subcutaneous layer deep to skin-mostly adipose tissue
The epidermis consists of stratified squamous epithelium
true
Dermis
*Papillary layer of areolar tissue
then
*Reticular layer of dense irregular connective tissue
Hypodermis
(subcutaneous layer or superficial fascia) seperates the integument from the fascia around deeper organs. This tissue layer is not a part of the integument
The network of arteries and veins connected to smaller vessels servicing the tissues of the integumentary system is the cutaneous plexus
true
Epidermis
- Keratinized stratified squamous epithelium
- Avascular
Cells of epidermis:
*Keratinocytes—produce fibrous protein keratin
*Melanocytes
10–25% of cells in lower
epidermis
Produce pigment melanin
- Epidermal dendritic (Langerhans) cells—macrophages that help activate immune system
- Tactile (Merkel) cells-touch receptors
NOTE: melanin protects nucleus of the cells from UV rays
Layers of the epidermis:
1. Stratum Basale (Basal layer)
- Deepest epidermal layer firmly attached to the dermis
- Single row of stem cells; source of new cells
- Also called stratum germinativum: cells undergo rapid division
- Journey from the basal layer to surface
- Takes 25–45 days
Layers of the epidermis: 2. Stratum Spinosum (Prickly Layer)
Cells are covered with thorn-like spines: provides strength and flexibility
abundant melanin granules and dendritic cells
Layers of the epidermis: Stratum Granulosum (Granular Layer)
- Thin, “grainy layer”
- 3-5 layers of flattened keratinocyte
- intermediate filaments located here
- Lamellated granules: secretion which acts as water repellant sealant
Layers of the epidermis: 3. Stratum Lucidum (clear layer)
- In thick skin – palms & soles of feet
- Thin, transparent
- Almost no organelles
- A few rows of flat, dead keratinocytes
Layers of the epidermis: 4. Stratum Corneum (Horny Layer)
- 20–30 rows of dead, flat, keratinized membranous sacs
- Three-quarters of the epidermal thickness
- Cells are continuously shed
Functions:
- Protects from abrasion and penetration
- Waterproofs
- Barrier against biological, chemical, and physical assaults
Clinical correlation: Psoriasis
- Abnormal Keratin
- Cells divide at a faster rate, faster than you can shed them
Dermis
- Strong, flexible connective tissue
- Cells include fibroblasts, macrophages, and occasionally mast cells and white blood cells
- Two layers:
- Papillary (loose areolar CT)
- Reticular (dense irregular CT)
Layers of the Dermis: Papillary layer
- Areolar connective tissue with collagen and elastic fibers and blood vessels
- Dermal Papillary: form friction ridges
- Dermal papillae contain:
- capillary loops
- Meissner’s corpuscles- tactile receptors (response to light touch)
- Free nerve endings-pain receptors
This layer of the skin is responsible for our fingerprints
Layers of the Dermis: Reticular Layer
~80% of the thickness of dermis
- Collagen fibers provide strength and resiliency
- Elastic fibers provide stretch-recoil properties
- Blood vessels, nerves, hair follicles, sebaceous and sudoriferous (sweat) glands
- Deep sensory receptors
- Pacinian corpuscle – deep pressure
Overview of sensory receptors
Levels starting from outer surface of skin:
- epidermis
- dermis
- hypodermis
- Pacinian corpuscle: senses pressure
- Nociceptor: senses pain
- Meissner’s corpuscle: senses touch
- thermo-receptor: senses heat or cold
Skin markings: friction ridges
Epidermal ridges lie atop deeper dermal papillary ridges to form friction ridges of fingerprints
Skin markings: Cleavage lines
- Collagen fibers arranged in bundles form cleavage (tension) lines
- Incisions made parallel to cleavage lines heal more readily
Skin color: Melanin
- Yellow to reddish-brown to black, repsonsible for dark skin colors
- produced in melanocytes migrates to keratinocytes where it forms “pigment shields” for nuclei
- Freckles and pigmented moles
- local accumulations of melanin
Skin color: Carotene
-Yellow to orange, most obvious in the palms and soles
Hemoglobin
Responsible for the pinkish hue of skin
Excessive exposure to sunlight
- eventually damages skin
- elastic fibers clump=leathery skin
- alters DNA of skin cells and can lead to skin cancer
***Melanoma: worst that skin cancer
Which layer of the skin has no blood vessels (avascular)?
epidermis
Derivatives of the epidermis
- Sweat glands (merocrine and apocrine)
- Oil glands (sebaceous glands)
- Hairs and hair follicles
- Nails
Sweat glands (sudoriferous): Eccrine
2 main types of sweat glands
- Eccrine (merocrine)- —abundant on palms, soles, and forehead
* Sweat: 99% water, NaCl, vitamin C, antibodies, dermcidin, metabolic wastes
* Ducts connect to pores
* Function in thermoregulation
* Emotional sweating “cold sweat”
Sweat glands (sudoriferous): Apocrine
—confined to axillary and anogenital areas
- Sebum: sweat + fatty substances and proteins
- Ducts connect to hair follicles
- Functional from puberty onward, body odor
- Specialized apocrine glands:
- Ceruminous glands—in the external ear canal; secrete cerumen
*Mammary glands
Sebaceous (oil) glands
- Widely distributed
- Most develop from hair follicles
- Become active at puberty (hormones)
- Sebum
- Oily holocrine secretion
- Bactericidal
- Softens hair and skin
If sebum blocks duct – white head
acne
Hair
Functions:
-Alerting the body to presence of insects on the skin
-Guarding the scalp against physical trauma, heat loss, and sunlight
Distribution:
-Entire surface except palms, soles, lips, nipples, and portions of external genitalia
- Eye lashes shield eyes
- Nose hairs filters large particles
Anatomy of hair
- Columns of dead, keratinized epidermal cells
- Shaft: projects above surface of the skin
- Root: penetrates into dermis or subcutaneous layer
- Three concentric layers:
- medulla: inner, lacking in thinner hair
- cortex: middle, major part of shaft
- cuticle: outermost, heavily keratinized
Hair follicle : Epithelial root sheath:
- external root sheath: continuation of epidermis
- internal root sheath: produced by matrix
Hair follicle: Dermal root sheath
-dense dermis surrounding hair follicle
Hair follicle: Bulb
base of hair follicle, houses papilla of hair
- papilla: areolar connective tissue & blood supply
Hair follicle: Arrector pili
-smooth muscle, attaches to dermal root sheath
Types of Hair
- Vellus—pale, fine body hair of children and adult females
* Terminal—coarse, long hair of eyebrows, scalp, axillary, and pubic regions (and face and neck of males - testosterone)
Hair growth
- Growth cycle: growth, regression & rest stages
- Active stage: cells of hair matrix divide, existing cells pushed upward, hair grows. 2-5 years
- Regression stage: cells of matrix stop dividing, follicle atrophies, hair stops growing. 2-3 weeks
- Resting stage: final stage before old hair falls out and new hair begins to grow. 3 months
Structure of nail
-Made from hard keratin
- Nail body: visible portion of nail
- free edge: part extending past end of digit
- Nail root: portion buried in a fold of skin
- lunula: whitish, thickened crescent shaped area
-Hyponychium: nail bed, secures nail to fingertip
- Eponychium: cuticle, narrow band of epidermis adheres to nail wall
- Corresponds to hooves/claws of animals
Skin cancer
-Most skin tumors are benign (do not metastasize)
- Risk factors:
- Overexposure to UV radiation
- frequent irritation of the skin
- 1 in 5 americans develop skin cancer
Skin cancer
Three major types:
*Basal cell carcinoma :
Least malignant, most common. Stratum Basale.
*Squamous cell carcinoma:
Second most common. Stratum Spinosum.
*Melanoma
Most dangerous. Melanocytes.
Greatest risk factor for skin cancer is overexposure to the UV raditaion in sunlight which damages DNA bases
Melanoma
Characteristics (ABCD rule)
A: Asymmetry; the two sides of the pigmented area do not match
B: Border exhibits indentations
C: Color is black, brown, tan, and sometimes red or blue
D: Diameter is larger than 6 mm (size of a pencil eraser
Burns
1st degree: epidermis
- redness, swelling & pain
- sunburn
2nd degree: upper dermis
- blisters
3rd degree: full thickness
- gray/white or blackened
- nerve endings destroyed
- graft may be necessary
Immediate threat:
*Dehydration and electrolyte imbalance, leading to renal shutdown and circulatory shock
*infection
Rule of nines
- Used to estimate the volume of fluid loss from burns
- 11 areas of body each account for 9% of body area
Partial thickness burns
First degree:
*Epidermal damage only
*Localized redness,
edema (swelling),
and pain
Second degree:
- Epidermal and upper dermal damage
- Blisters appear
Full-thickness burns
Third degree:
-Entire thickness of skin
damaged
*Gray-white, cherry red,
or black
*No initial edema or pain
*Skin grafting usually
necessary
Steps in tissue repair 1
- Inflammation:
* Release of inflammatory chemicals
* Dilation of blood vessels
* Increase in vessel permeability
* Clotting occurs
Steps in tissue repair 2
Organization and restored blood supply:
- The blood clot is replaced with granulation tissue, which restores the vascular supply
- Epithelium begins to regenerate
- Fibroblasts produce collagen fibers to bridge the gap
Debris is phagocytized
Steps in tissue repair 3
Regeneration and fibrosis:
*The scab detaches
- Fibrous tissue matures; epithelium thickens and begins to resemble adjacent tissue
- Results in a fully regenerated epithelium with underlying scar tissue
