The Integument: Cutaneous Membrane

Reticular Layer

-Deep layer -Dense irregular CT -Relatively high elastic fiber content -Provides strength and elasticity -Numerous accessory structures are found within the reticular layer.

Dermis

-Deep to the epidermis -Primarily connective tissue proper -Two layers(Papillary and Reticular)

Mammary Glands

-Modified apocrine sweat glands -Found in the breasts of both men and women -Produce milk -Generally only active in certain females as a result of hormonal control.

Ceruminous Glands

-Modified apocrine sweat glands -Found in the ear canal -Secretion mixes with sebum and shed keratinocytes to form cerumen (ear wax)

Nail Structure

A.Nail root B.Eponychium(cuticle) C.Lunula D.Nail body E.Free edge F.Hyponychium G.Epidermis H.Dermis I.Phalanx(finger bone)

Merkel (tactile) cells

Definition-Large, specialized epithelial cells that stimulate specific sensory nerve endings when they are distorted by fine touch or pressure.

Accessories

Many of the accessory structures located in the dermis are of epidermal origin. -These include Nails, hair,sweat glands,sebaceous glands -There are also non-epidermal accessories Muscles, sensory receptors

Hair Types

1.Lanugo- in newborns, fine unpigmented, downy hair that first appears on the fetus in the second trimester of development. 2.Vellus-primary human hair and is found on most of the body. Adult hair,short,fine,light pigmented 3.Terminal hair-coarser, pigmented, and longer than vellum. Facial and pubic regions

Epidermis

Definition-Epithelium of the integument 1. The epidermis is a keratinized, stratified squamous epithelium.

Nails

Definition-Scalelike modifications of the stratum corner layer of the epidermis that form on the dorsal tips of the fingers and toes. -Composed of dead, keratinized cells -Protect the exposed digital tips against damage and distortion under stress.

Arrector pili muscle

Definition-Thin ribbons of smooth muscle -Smooth muscles -Involuntary -Originate in the papillary dermis, insert on the lateral sides of hair follicles. -Contraction lifts hair to...improve insulation value of hair, make the body appear larger -Stimulated in response to an emotional state

Stratum Lucidum(or clear layer)

Definition-a thin translucent region about two to three cell layers thick that is superficial to the stratum granulosum. -Variably present -Only found in the thick skin of the palm side of the hand and the plantar side of the foot. -Superficial to the stratum granulosum -Cells do not stain well, so it appears colorless

Stratum granulosum(or granular layer)

Definition-consists of three to five layers of keratinocytes superficial to the stratum spinosum. 1.Superficial to the stratum spinosum 2.Keratinocytes begin to produce keratin 3.As keratin progresses.... -Cells become more squamous -Plasma membranes become thicker and lest permeable -Cells eventually die, breakdown of cellular membranes produces this layer granular appearance

Melanocytes

Definition-have long, branching cytoplasmic processes and are scattered among the keratinocytes of the stratum basal. They produce and store melanin in response to ultraviolet(UV) light exposure.

Sebaceous Glands

Definition-holocrine glands that discharge an oily, waxy secretion. -Most are associated with hair follicles. -Produce oily sebum by holocrine secretion -Mildly bactericdal -Coats surface of hair -Activity is influenced by hormones(especially sex hormones) -Prone to blockage, especially during adolescence. Acne,boils

Stratum corneum(or hornlike layer)

Definition-is the most superficial layer of the epidermis. 1.Superficial layer -20 to 30 layers of dead,scaly,interlocking keratinized cells called carneocytes. -Old keratinocytes are regularly shed from the apical surface (exfoliation) -Unsuitable to sustain most microorganisms

Integument

Definition-is the skin that covers your body. Skin is also known as Cutaneous membrane or Cutaneous layer. 1.Largest organ of the body 2.Covers the entire external surface of the body. 3. Contains all four of the primary tissue types.

Keratinization

Definition-keratinocytes fill up with the protein keratin.

Apocrine Sweat Glands

Definition-release their secretion into hair follicles at armpits(axillae), nipples(areola),groin(pubic region), anus(anal region) -Found in the axilla, the pubic and anal regions as we as around the areolae of the breasts. -Coiled, tubular shape with a duct that opens into hair follicles. -Secretion is viscous and cloudy -Produced by merocrine secretion -Produces distinctive odors -May also carry pheromones

Stratum spinosum

Definition-several layers of polygonal keratinocytes. 1.Overlies the stratum basal 2.Varies in thickness 3.Consists primarily of keratinocytes -Form desmosomes with neighboring cells -Also contains Langerhans(epidermal dendritic)cells

Stratum Basale(or Germinativum)

Definition-the deepest epidermal layer. 1.Single layer of cuboid cells along the basal surface. Contains....basal cells,melanocytes,merkel (tactile) cells

Keratinocytes

Definition-the most abundant cell type in the epidermis and occur throughout all epidermal strata. The stratum basal is dominated by large keratinocyte stem cells, which divide to provide both replacement stem cells and the new keratinocytes that replace the dead keratinocytes shed from the surface. 1.Most common,skin cell,99%

Papillary Layer

Definition-the super facial region of the dermis directly adjacent to the epidermis. -Superficial portion of the dermis -Areolar connective tissue -Contains...blood capillaries supplying the overlying epidermis -Sensory receptors, meisner's corpuscles sensitive to light pressure and vibration -Dermal papillae, projections of tissue, most pronounced in the thick skin, lie alongside epidermal ridges(complimentary projections of the epidermis)

Subcutaneous Layer(hypodermis, Superficial Fascia)

Definitions-deep to the integument -Deep to the dermis, not actually part of the integument. -Consists of...Areolar CT,Adipose CT Functions-Loosely binds skin to underlying muscles Provides padding and thermal insulation

Merocrine (Eccrine) Sweat Glands

Defintion-realease secretion onto the surface of the skin. -Most numerous and widely distributed -Smaller than apocrine glands and ducts open one the skin surface(sweat pores) -Secretion is thin and clear (perspiration) Functions-Thermoregulation, Excretion, Protection by dilution

Hair

Non-living projections of keratinized epidermal tissue. -Found in most skin except...palms of hands,soles of feet,lips,parts of the genitalia ~5 million hairs form in follicle -Hair Functions 1.Physical protection 2.Heat retention 3.Sensory reception 4.Communication 5.Expression 6.Identification 7.Signal dispersal

Cutaneous membrane

Skin

Skin Color

Skin color is the product of several factors: -Dermal blood supply -Increased supply ->darker,redder color (blush) -Reduced supply ->paler,bluer color (cyanosis) -Pigments- Melanin-dark(usually brown-black) pigment, protects cell nuclei from UV radiation, Variation is a result of varying levels of melanocyte activity -Influenced by genetics an environment Increased exposure to light increases melanocyte activity -Carotene- -Yellow red pigments -Dietary (mostly from fruits and vegetables) -Carotene is used by to body for a variety of important functions(e.g. production of Vitamin A) -Excess carotene accumulates in the keratinocytes

Sweat Glands

Two main types of sweat glands Apocrine sweat glands and Merocrine sweet glands. -Both types have myoepithelial cells and are under autonomic control.

Hair Structure

Two parts 1.Shaft-portion of the hair that extends beyond the skin surface. 2.Root-portion of the hair deep to the skin surface. Hair bulb- consists of epithelial cells and is a swelling at the base where the hair originates in the dermis. Matrix- specialized type of keratinization that occurs. Hair papilla-composed of a small amount of connective tissue containing tiny blood vessels and nerves.

Sensory Receptors

Variety of structures that response to stimuli such as pressure, vibration, temperature, pain, and itch. Examples-Merkel cells(see epidermis), Meisner's corpuscles(see papillary dermis) Layer=Lamellated (Pacinian) corpuscles-sensitive to stronger pressure and vibration.