Anatomy Chapter 8

lunula

actively growing part of the nail that is visible. a pale crescent-shaped disc that extends beyond the proximal nail fold. it is the distal portion of the ventral nail matrix.

hemidesmosomes

after a basal cell keratinocyte divides (undergoes mitosis and cytokinesis), the deeper of the two daughter cells remains attached to the basement membrane by this

sebacous glands

also called oil glands. secrete sebum. attached to "leaning" side of hair follicles. not located on palms or soles. lack the water-resistant oily covering present on other parts of your body. stimulated by hormones. temperature can also affect these. HOLOCRINE GLANDS

cholecalciferol

also known as vitamin D3. its added to milk to promote good health. this is an inactive (unusable) form of vitamin D. this diffuses into the blood and travels to the liver

pigment

an organic molecule that gives color to a cell, tissue, or organ

superficial fascia

another name for the hypodermis. called this because the hypoderis is superficial to underlying muscles

ruffini's endings

are located mainly in the lower dermis of both thick and thin skin, and in the hypodermis, where they respond mostly to skin stretch and vibration. looks like cylinder with a connective tissue shell surrounding one or two nerve endings.

Meissner corpuscles or tactile corpuscles

are mechanoreceptors sensitive to light touch, and are found mainly in the dermal papillae of thick skin. most abundant in fingertips. these are a fluid-filled, encapsulated receptor, consisting of several layers of flat epithelial cells intertwined with a single nerve ending. this corpuscle has an outer covering made of fine elastic fibers and fibroblasts.

eccrine sweat glands

are simple, coiled tubular (one duct and one coiled tube-like gland). they are also sudoriferous (produce sweat), exocrine (have a duct and release secretions to the outside of the body), and merocrine (release secretions by exocytosis) glands.

encapsulated nerve endings

are surrounded by a well-defined "shell" of connective tissue. type of cutaneous receptor that is classified structurally

papillary plexus

arterioles at the junction between the reticular and papillary regions of the dermis form this fin network. small loops of capillaries extend superficially from this into the dermal papillae, where nutrients diffuse across the basement membrane into the epidermis.

erythema

as more blood flows through the skin's vessels, the skin turns red (this), and feels warm to the touch - inflammation stage

epidermal nerve endings

attach to a specific type of cell in the epidermis, or a structure that is derived from epidermal cells. type of cutaneous receptor that is classified structurally

is epidermis vascular or avascular

avascular (lacks vessles)

what secretes the basal lamina

basal keratinocytes in the stratum basale secrete this superficial portion

langerhans cells

belong to a class of white blood cells called macrophages. they are located in the stratum spinosum. they are motile and can perform phagocytosis to remove foreign particles from the epidermis

squame cells

cells in the stratum corneum that are dead, flattened keratinocytes. have a rough leathery texture because the cells are keratinized (or cornified)

merkel cells

cells that are also scattered throughout the stratum basale. they are thought to be modified keratinocytes. they are in close contact with a nerve ending located in the upper region of the dermis.

hair matrix

cells that form the different layers in a hair arise from the portion of the hair bulb called this. where the hair is "born". also gives rise to parts of the hair follicle. consists of several layers of modified epidermal cells (mainly keratinocytes).

inflammation stage

chemical reactions in the blood convert a soluble blood protein into an insoluble form called fibrin. strands of fibrin interlock, forming a "net" that traps blood cells in the broken vessel and helps reduce blood loss. the fibrin strands and trapped blood cells form a clot. the part of the clot at the wound's surface soon hardens, forming a scab, which protects the wound against bacteria and prevents the underlying tissue from dehydrating.

hyponychium

clumps of stratum corneum that form this. this helps to seal the inferior margin of the free end.

tension lines or lines of cleavage

collagen fibers in the reticular region are organized into bundles that align in parallel rows. these bundles usually align in the same direction that the skin stretches, which is why they are known as this

Skin or Cutaneous membrane

composed of different tissues, is physically distinct from surrounding organs, and performs functions specific to its structure.

free nerve endings

consists of a nerve endings not surrounded by a capsule of connective tissue. type of cutaneous receptor that is classified structurally

hair papilla

consists of areolar connective tissue and blood vessels. provides nutrients to the hair bulb

dermal (fibrous) root sheath

consists of collagen fibers and fibroblasts, and serves to anchor the hair follicle to the surrounding dermal tissue

hair growth cycle

consists of three phases - anagen, catagen, and telogen - during which a hair follicle grows a hair, sheds it, and then begins forming a new hair

stratum spinosum

contains eight to ten rows or keratinocytes, and is superficial to the stratum basale.

inner root sheath

contains mostly keratinocytes and is continuous with the stratum spinosum. makes contact with the hair from the hair bulb to about the level of the sebaceous gland, but at the sebaceous gland, this disintegrates.

literal moving of integumentary

covering

thin skin

covers the entire body except the palms, the anterior surfaces of the fingers, the soles of the feet, and the plantar (inferior) surfaces of the toes. has a FOUR layer epidermis

two regions of hair shaft

cuticle and the cortex

proliferation stage

damaged integumentary system structures begin to regrow. cells from the stratum germinativum migrate across the wound along the inferior margin of the scab and begin replacing the epidermis. fibroblasts in the dermis secrete collagen that ts into thick fibers and ties the edges of the wound together. severed blood vessels are reconnected, and damaged nerves are regenerated.

eumelanin

darkest and most common form, is brown-to-black in color - darker skinned people usually produce more of this

dermis or stratum corium

deep to the epidermis and forms the bulk of the skin (by weight and by volume). consits of dense irregular connective tissue, with collagen fibers accounting for about 70% of the total weight.

hair root

deeper part of the hair that is firmly attached to the inner root sheath of the hair follicle. extends from the hair shaft into the hair bulb

epidermal surface features are classified into three groups

surface pattern lines, flexure lines, and friction ridges

cerumen

waxy secretion, also called earwax, that waterproofs the ear canal and may help repel tiny insects

goose bumps or cutis anserina (physiological name)

when the skin around the hair is pushed into a little peak

edema

when tissues swell

myoepithelial cells

whenever the nervous system stimulates eccrine sweat glands, the nervous system stimulates specialized contractile cell which surround the secretory cells at the base of the gland. These cells contract and squeeze the sweat into the duct leading to the hair follicle.

autophagia

where lysosomes in the cytoplasm are digesting other organelles. this occurs in the stratum granulosum where keratinocytes are flatter than the spiny cells in the stratum spinosum, and most are dying and undergoing this.

lateral nail groove

where the nail plate curves inferiorly

three basic patterns of fingerprints

whorl, loop, and arch

dehydrocholesterol

UVB radiation converts this compound, found inside keratinocytes of the stratum germinativum, into cholecalciferol. Keratinocytes synthesize this from cholesterol

three types of cutaneous receptors - structurally

1. encapsulated nerve endings 2. free nerve endings 3. epidermal nerve endings

three types of cutaneous receptors - how they respond to certain stimulus

1. mechanoreceptor 2. nociceptor 3. thermoreceptor

is the epidermis or dermis thicker?

DERMIS

two kinds of apocrine glands

ceruminous glands and mammary glands

reticular plexus

"braided" network. its the largest vessels in the skin that are sandwiched between the reticular dermis and the hypodermis.

literal meaning of strata

"layers"

strata

"layers" of finer tissue. located in both the epidermis and dermis. this is what makes skin a stratified organ

functions of fatty acids in sebum

1. decrease the sebum's pH, which can inhibit the growth of certain types of bacteria and fungi on the skin's surface 2. after entering a hair follicle, sebum coats the hair inside making it more flexible and able to repel water 3. when sebum reaches the skin's surface, it coats the epidermal cells and helps keep them flexible and water resistant

dermis is divided into two regions

1. papillary region (thin) reticular region (thick)

two parts of the basement membrane

1. reticular lamina 2. basal lamina

functions of hair

1. scalp hairs shield the scalp, the skin that covers the skull, from the damaging effects of UV radiation. scalp hairs also help to insulate the scalp from heat and cold 2. eyebrows reduce glare around the eyes, and eyelashes prevent foreign particles from reaching the surface of the eye 3. hairs help keep dust and other foreign objects from entering the eyes, nasal cavities and ear canals 4. hairs in the axillary regions reduce friction while the arms are swinging and hair in the pubic region reduces skin friction during sexual intercourse

functions of papillary region

1. secures the epidermis to the dermis, 2. provides nutrients to the cells of the epidermis

keratinization or cornifcation five step process

1. synthesis of keratin and formation of intermediate filaments in the stratum basale 2. formation of keratin tonofilaments in the stratum spinosum 3. binding of tonofilaments with kertohyalin to form keratin fibrils in the stratum granulosum 4. conversion of keratohyalin to eleidin (in the upper stratum granulosum or stratum lucidum) 5. aggregation of keratin fibrils into bundles in the stratum corneum

melanin

a chemical that darkens the skin and helps protect underlying tissues from the ultraviolet rays of the sun

heme

a constituent of hemoglobin, the oxygen-carrying molecule in red blood cells. dramatic evidence of this is during blushing.

nociceptor

a free nerve ending that generates an impulse interpreted as pain. stimulated most often by tissue damage, resulting from a wound, extreme hot or cold temperature, or stretching. certain chemicals whether foreign or those released from surrounding tissues, can stimulate these.

cuticle

a hair's outer covering and consists of five to ten layers of dead, flattened keratinocytes (squamous cells).

deep pressure receptor

a mechanoreceptor that generates an impulse when something presses hard enough against the skin to compress the hypodermis

the duct of an eccrine gland has two parts

a spiraled part in the epidermis and a straight part in the dermis

keratin

a structural, filamentous proteins, and is abundant in the horns of certain animals (mainly cows)

stratum granulosum

a thin region, containing only three to five rows of cells, and located immediately superficial to the stratum spinosum.

stratum lucidum

a thin, clear region seen only in the thick skin of the palm and sole. contains 3 to 5 rows of keratinocytes, all of which are dead.

carotene

a yellow-orange, lipid-soluble precursor to vitamin A. It can diffuse from the blood into keratinocytes of the epidermis and adipocytes of the hypodermis. this pigment is only noticeable in light-skinned people

flexure lines

deeper than surface pattern lines and exist in regions where skin is flexed (bent) repeatedly. examples are "life lines" on palms and wrinkles and grooves on the face. pattern of these usually corresponds to orientation of parallel bundles of collagen fibers in underlying dermis

nail bed

dense collagenous fibers firmly anchor this to the underlying bony structure of the digit.

four layers of the hair follicle

dermal root sheath, glassy membrane, the outer root sheath and the inner root sheath.

epidermal wounds

do not penetrate deeper than the basement membrane of the epidermis. these do not bleed. to repair these, there is repeated cell division of nearby, undamaged epidermal. either the superficial strata simply re-grow from the stratum germinativum, or undamaged epidermal cells from the stratum germinativum surrounding the wound, divide and the daughter cells spread to fill in the wound.

epidermal pegs

downward projections of the epidermis

suoriferous gland

eccrine sweat glands are a type of this because it produces sweat

3 different skin glands

eccrine, apocrine and sebaceous glands

terminal hairs

eight times thicker than vellus hairs. usually contain pigment. these develp from vellus hairs at puberty, in the axillary and pubic regions.

eleidin

enzymes transform the keratohyalin granules into this chemical, causing the cell's cytoplasm to appear clear, not grainy.

literal meaning of epidermis

epi = on dermis = skin

merkel discs or tactile discs

epidermal nerve endings that attach to merkel cells int he stratum basale of both thin and thick skin. the Merkel cell causes this to initiate an impulse, which you feel as a light touch. these branch from a single nerve fiber in the dermis and extend to the base of epidermal peg.

thin skin and thick skin only apply to...

epidermis

melanocytes make two kinds of melanin

eumelanin and pheomelanin

fingerprints

example of friction ridges. these are telltale impressions of the ridges themselves.

surface pattern lines

extremely small, triangular or polygonal-shaped line patterns seen only on thin skin. increase surface area, allowing it to stretch more evenly during movement

remodeling stage

fibroblasts in the dermal zone of the wound continue to produce collagen fibers that arrange themselves in large irregular bundles. fibrous, source of scar tissue, occurs. scar tissue helps strengthen the site of the wound, but it me problematic because it is usually much less flexible than an undamaged dermis. over time, collagen fiber in the scar tissue arrange themselves in a more regular pattern, similar to the pattern in dermal tension lines.

what secretes the reticular lamina

fibroblasts within the dermal papillae secrete compounds that form this bottom half

anagen

first and longest phase of hair growth. hair is growing from dividing cells in the hair matrix, and the hair is pushing through a fully developed hair follicle. hair grows fastest at the start of this phase

medulla

forms a narrow central core that is seen only in the root of thick terminal hairs. consists of loosely packed keratinocytes filled with soft keratin and interspersed with air spaces

cortex ("bark")

forms the bulk of the hair. responsible for hair's strength and color. consists of cylindrical keratinocytes that contain hard keratin.

Hair receptors or hair root plexuses

found only in think skin containing hair follicles, the tubes from which individual hairs grow. the hair follicle is derived from epidermal cells so these are epidermal nerve endings. these consists of numerous nerve endings. this doesn't reach the hair, but when something touches the hair hard enough to bend its follicle, this initiates an impulse allowing you to feel your hair move

thermoreceptor

generates an impulse in response to changes in temperature. most of these are free nerve endings

keratohyalin

granules of this attach to the keratin fibrils. these are part protein. they absorb dye and cause the keratinocytes to appear dark and "grainy"

Hair or pili

grow from tube-like structures called hair follicles and consist of densely packed keratinized cells.

telogen

hair follicle's resting phase. base of the follicle has shrunk to the point that it is very near the surface of the epidermis. at this time, the club hair may be shed from the follicle

thick skin

has a relatively deep, FIVE layer epidermis. Covers the anterior surface of the hands and fingers and the plantar surface of the feet and toes

two pigments not produced in the skin

heme and carotene

dandruff

if the epidermis becomes too dry, large clumps of squame cells may detach together, causing the skin surface to look flaky.

sweat pore

in eccrine glands. the sweat-forming portion of the gland is a tightly coiled tube housed in the reticular region of the dermis. the gland's secretions are released into a single tubular duct that opens directly onto the skin's surface through this...

skin derivatives

include hair, nails, and variety of microscopically small glnads

advantages of epidermal pegs and dermal papillae structure

increase amount of surface area contact between epidermis and dermis, firmly anchors the epidermis to the dermis and it increases the surface area over which nutrients can diffuse from dermal blood vessels to epidermal cells

trichosiderin

iron-rich form of pheomelanin that makes hair red.n

hair follicle

is a tube-like organ that produces a hair. its a pouch-like extension of the epidermis that plunges deep into the superficial region of the hypodermis in some cases. deepest part of this is in the reticular region of the dermis.

stratum corneum

is the most superficial stratum of the epidermis. may consist of a bunch of layer of keratinocytes (thick skin) or only a few layers of keratinocytes (thin skin)

epidermis

is the thinner, superficial layer of the skin consisting of stratified squamous epithelium

basal cells

keratinocytes comprising the stratum basale are called this and is attached to neighboring ______ cells by desmosomes

spiny (prickle) cells

keratinocytes in the stratum spinosum are sometimes called this because when the cells in the stratum spinosum lose water and crenate (shrivel) and the desmosomes continue to hold the cells together, the stretched plasma membranes appear to have spines.

pacinian corpuscles or lamellated corpuscles

largest cutaneous receptors and respond to deep pressure and vibration. some are found deep in the dermis of both thick and thin skin, but most are found in hypodermis, where they are examples of subcutaneous receptors. these are encapsulated mechanoreceptors

outer root sheath

lies between the glassy membrane and the inner root sheath. contains mostly keratinocytes, and is continuous with the stratum basale

lamellar granules

lipid-rich vesicles which stack like small saucers. they fuse with the plasma membrane and release their lipids into the extracellular spaces between the keratinocytes. keratinocytes consist of these in the stratum granulosum

papillary region

located deep to the basement membrane of the epidermis and is named for its tiny projections (the dermal papillae). contains areolar connective tissue.

hard keratin

located in the cuticle. has more sulfide bonds and twists more tightly than "soft" keratin found in the epidermis. strengthens the desmosomes so that the cuticle cells do not peel off (desquamate)

mammary glands

located within the breasts. produce milk, but this occurs only during lactation period following childbirth.

ceruminous glands

located within the skin of the external ear canals. waxy secretion called cerumen

merkel disc

made of a single merkel cell and the nerve ending beneath it. it functions as a receptor of light touch

histamine

mast cells in the region of the wound release this. a substance that dilates blood vessels - part of inflammation stage. also causes the vessels to leak blood plasma into surrounding tissues causing them to swell

keratinocytes

most cells in the epidermis are these. they are named this because they secrete keratin

eccrine sweat glands

most important skin derivatives. they regulate body temperature and excretion. more prevalent in palms and soles. stimulated by the nervous system

arrector pili

muscle attached to the dermal root sheath of most hair follicles. extends just below sebaceous gland to the papillary region of the dermis. located on "leaning" side of hair follicle. contracts in response to cold temperature, making goose bumps

cutaneous receptors

nerve endings in the epidermis, dermis, and hypodermis. also us to experience different cutaneous sensations (awareness of stimuli in the skin). this receptor initiates an impulse that passes along a nerve to the brain, where the impulse is interpreted.

hypodermis or subcutaneous tissue

not part of the skin. helps attach the skin to the body. consists of areolar and adipose connective tissue. cushions the skin against hard, deep structures such as bones

hypodermis or subcutaneous tissue

not part of the skin. it is what underlys the skin. composed of areolar and adipose connective tissue

vellus hairs

often called "peach fuzz" - covers most of the body and are extremely thin. most of these lack pigment

sebum

oily fluid secreted by sebacous glands. lubricates hair within hair follicles and helps make the hair and epidermis water resistant. viscous secretion consisting mostly of tiglycerides and free fatty acids.

hair shaft

part of the hair you see above the skin, but it also extends into the skin to about the level of the sebaceous gland

proximal nail fold

pocket of the epidermis where nails form. located at the end of a digit. the epidermis tucks beneath itself, becoming the DORSAL MATRIX, which then wraps distally forming the VENTRAL MATRIX.

excretion

process of expelling waste

sensible perspiration

process of water loss that we are aware of or can feel. like sweating

insensible perspiration

process of water loss that we are unaware of. occurs because the epidermis is not waterproof, so in a dry environment, water constantly diffuses out of the skin - water lost by diffusion through the epidermis

piloerection

process when the arrector pili contracts in response to cold temperatures and yanks the follicle and its hair into a vertical position. this pushes the skin into goose bumps

desquamation or exfoliation

process when the desmosomes holding adjacent squame cells together break, allowing the outermost cells to peel off.

epidermal migration

process where undamaged epidermal cells from the stratum germinativum surrounding the wound, divide and the daughter cells spread to fill in the wound.

apoptosis

programmed cell death. some say that the reason keratinocytes die in the stratum granulosum is due to lack of nutrients or this..

functions of integumentary system

protection, temperature regulation, emergency blood reserve, excretion, sensation, vitamin D synthesis, identification, communication of emotions, sexual differentiation, and diagnosing and treating health problems

pheomelanin

red-to-amber in color - light skinned people typically produce more of this

mechanoreceptor

responds to mechanical forces, such as compression and stretch. most of these are encapsulated nerve endings. there are two different types

vasoconstriction

ring-like muscles surrounding the dermal arterioles contract, causing the vessels to narrow. dermal blood flow decreases, and less heat radiates from the blood to the external environment.

vasodilation

rings of smooth muscle that surround the dermal arterioles relax, causing the vessels to widen. dermal blood flow increases, so more heat radiates to external environment

free sebaceous glands

sebaceous glands that do not attach to hair follicles, but secrete sebum directly onto skin's surface. found in skin of eyelids, certain regions on the external genitalia, and in the areola of the nipples

free nerve endings

sensory receptors which are root-like branches of neurons, that extend between the basal cells and into the stratum spinosum. important for temperature detection and generation of pain signals when the epidermis is damaged

epidermal grooves

shallow grooves between epidermal ridges or friction ridges which correspond to indentations of the epidermis, called epidermal pegs, into the dermis.

stratum basale

single row of cells (most of these are keratinocytes) that form the base (basal layer) of the epidermis.

wrinkles

skin creases that become more prevalent as we get older, when the epidermis and the dermis become thinner

integumentary system

skin is most prominent organ but is also comprised of orther organs called skin derivatives (or accessory organs)

epidermal ridges or friction ridges

slightly elevated, parallel lines separated by shallow grooves on the surface of thick skin. they provide a rough surface that allows the fingers and palms to grip objects more effectively, and they help prevent feet from slipping. these correspond to rows of tiny projections, called dermal papillae, located at the superficial margin of the dermis

melanocytes

spider-shaped cells that synthesize melanin. between 5% and 25% of the stratum basale are these cells

order of skin layers in thin skin

stratum corneum, stratum granulosum stratum spinosum, and stratum basale

order of skin layers in thick skin

stratum corneum, stratum lucidum, stratum granulosum stratum spinosum, and stratum basale

functions of keratinocytes in stratum basale

synthesize part of the basement membrane (basal lamina) by secreting proteoglycans, they synthesize keratin polypeptides, and they are the principal source of epidermal growth

two different mechanoreceptors

tactile receptor and deep pressure receptor

dendrites

the arm-like projections of a melanocyte that extend between adjacent basal cells and outward between keratinocytes in the stratum spinosum.

hair bulb

the base of the hair follicle that fits like a cup over the hair papilla. contains mostly keratinocytes but also has some melanocytes and Langerhans cells

glassy membrane

the basement membrane separating the epidermis from the dermis extends into the hair follicle called this. has a clear appearance. separates epidermal tissue (outer root sheath) from dermal tissue (dermal root sheath)

lamellae

the capsule of the pacinian corpuscles surrounding the nerve ending consists of flat fibroblasts arranged in concentric layer called this

eponychium

the cuticle of the nail. as the nail plate creeps along the nail bed, bands of the stratum corneum from the surrounding epidermis stick to the nail's superior margins, forming this.. this helps to seal the nail matrix and nail bed from the external environment.

strata

the different layers in the epidermis. there are four in thin skin and five in thick skin. the strat consists of one or more rows of similar-looking cells.

calcitriol

the kidneys convert the calcidiol into the active (usuable) form of vitamin D called this. shows importance of this vitamin to calcium homeostasis

calcidiol

the liver converts the vitamin D3 into this, which travels through the blood to reach the kidneys

epidermis

the most superficial region of the skin, and lies superficial tot he dermis.

nail root

the nail starts forming here, and the dorsal matrix and the ventral matrix add more keratinocytes to complete the nail plate

free nerve endings (FNEs)

the only cutaneous receptor found in both the epidermis and the dermis, and they are found in both thin and thick skin. these extend throughout the dermis and extend through the basement membrane into the stratum basale and stratum spinosum. most of these are nociceptor, but sometimes are mechanoreceptors or thermoreceptors.

melanin

the only endogenous skin pigment; the only pigment made by the skin itself. melanocytes in the stratum basale secrete this. this is a complex polymer derived from the amino acid tyrosine.

free edge

the part of the nail at the tip. used to grasp or pinch objects

granulation tissue

the pink, sensitive tissue around and beneath the scab during the proliferation stage. because it does not have a well-defined structure.

fibrosis

the proliferation of collagen fibers during the remodeling stage. source of scar tissue. the more fibrosis, the more scar tissue.

evaporative cooling

the release of heat that takes place when water evaporates off the skin surface. the watery protion of eccrine sweat is an important source of this.

keratin tonofilaments

the resulting protein strands that arise int he stratum spinosum where more keratin polypeptides form within the keratinocytes and combing with existing intermediate filaments of the cytoskeleton. these are thicker and denser than the intermediate filaments found within the stratum basale

reticular region

the scaffolding of the skin. fibrous region of the dermis that is located between the papillary region and the hypodermis, and it is the thickest part of the dermis. consists of dense irregular connective tissue

catagen

the second and shortest phase of hair growth. base of the hair follicle shrinks toward the epidermis, eventually diminishing to about one-sixth its original length. matrix cells die, and the hair bulb detaches from hair papilla resulting in club hair. as hair follicle shrinks, it slowly pushes the club hair toward the surface of the epidermis.

two regions of a hair

the shaft and the root

nail plate

the shovel-shaped body of a nail.

stratum germinativum

the stratum basale and stratum spinosum together are sometimes called this because some of the cells in the stratum spinosum are still capable of dividing, which means they can contribute to the outward growth of the epidermis

basal lamina

the superficial portion of the basement membrane that separates the epidermis from the dermis. made of proteoglycans from which keratinocytes secrete.

dermis

the thicker layer, lies deep to the epidermis and consists mostly of dense irregular and areolar connective tissues

keratinization

the transformation of living keratinocytes, in the deeper strata, to dead flat cells full of keratin protein, at the apical surface. this process requires about four weeks

dermal papillae

the upward projections of the dermis

pilosebaceous unit

the whole unit of the sebaceous gland and the hair follicle which secretes through the hair follicle

glabrous skin

thick skin lacks hair so it is sometimes called this (since it lacks hair, it lacks sebaceous (oil) glands)

keratin fibrils

thick strands formed when keratinocytes are pushed outward into the stratum granulosum, and their keratin tonofilaments intertwine to form these thick strands

hirsute skin

thin skin is sometimes called this because occasionally it contains hair

deep wounds

those that penetrate into the reticular region of the dermis, but they may extend well into the hypodermis. repair of deep wounds involves three main stages - inflammation, proliferation, and remodeling

main functions of the inflammation stage

to restrict the movement of harmful agents, such as bacteria, from the wound site and to seal off damaged tissues so they can be cleaned up

tactile receptor

touch receptor. its a mechanoreceptor that generates an impulse when something makes light contact with the skin

Apocrine sweat glands

unique sweat glands, like eccrine glands, have a sweat-forming portion that is a highly coiled tube. mainly attached to hair follicles. located in thin skin of the axillary, anal, areola (nipple), and pubic regions. these secrete sweat into the hair follicle to which they are attached. contain lipids and proteins, which make it more viscous (thicker). considered a merocrine gland. stimulated by hormones. they have myoepithial cells surrounding their secretory cells that squeeze sweat into the secretory ducts.

dermal papillae

upward projections that interlock with the epidermal pegs. consist of areolar connective tissue that contains fibroblasts, mast cells, very thin collagenous and elastin fiber, tiny loops of capillaries, and one or more sensory receptors.

two types of hairs

vellus and terminal

melanosomes

vesicles where melanin molecules (granules) are packaged. this is in a melanocyte. keratinocytes use phagocytosis to engulf the dendritic tips containing these, causing these to release their granules into the cytoplasm.