A&P Quiz 4 (Chapters 5 and 6)

what are the three types of bone cells?

osteoblasts, osteocytes, osteoclasts

bone matrix

-35% organic material and 65% inorganic material -organic material: collagen, proteoglycans -inorganic material: calcium phosphate crystal called hydroxyapatite -the collagen and mineral components are responsible for the major functional characteristics of bone -collagen fibers lend flexible strength to the matrix and the mineral components give the matrix weight bearing strength (if mineral is removed from bone, the bone will be overly flexible, and if the collagen is removed from the bone, it would become very brittle)

erythema

-a condition in which the skin turns a reddish hue when the amount of blood flowing through the skin increases -an inflammatory response stimulated by infection, sunburn, allergic reactions, insect bites, or other causes can produce erythema, as can exposure to the cold, and blushing or flushing when angry or hot

periosteum

-a connective tissue membrane covering the outer surface of a bone -the outer fibrous layer is dense irregular collagenous connective tissue that contains blood vessels and nerves -the inner layer is a single layer of bone cells, including osteoblasts, osteoclasts, and osteochondral progenitor cells -where tendons and ligaments attach to bone, the collagen fibers of the tendon or ligament become continuous with those of the periosteum -some of the collagen fibers of the tendons or ligaments penetrate the periosteum into the outer part of the bone-these bundles of collagen fibers are called perforating fibers, or sharpey fibers, and they strengthen the attachment of the tendons or ligaments to the bone

cyanosis

-a decrease in blood flow, as occurs in shock, can make the skin appear pale -occurs as a decrease in blood oxygen content -is a blueish skin color

melanin

-a group of pigments primarily responsible for skin, hair, and eye color -provides protection against ultraviolet light from the sun -large amounts of melanin are found in certain regions of the skin, such as freckles, moles, the nipples, the areolae of the breasts, the axillae, and the genitalia -lips, palms of the hands, and soles of the feet, contain less melanin -melanin is produced by melanocytes

nails

-a nail is a thin plate consisting of layers of dead stratum corneum cells that contain a very hard type of keratin -located in the distal ends of the digits (fingers and toes) -consists of the proximal nail root and the distal nail body -the nail root is covered by the skin and the nail body is the visible portion of the nail -the lateral and proximal edges of the nail are covered by skin called the nail fold, and the edges are held in place by the nail groove -the stratum corneum of the nail fold grows onto the nail body as the cuticle/epychonium -beneath the free edge of the nail body is the hypochonium: a thickened region of the stratum corneum

albinism

-a recessive genetic trait that results from an inability to produce tyrosinase -result is a deficiency or an absence of pigment in the skin, the hair, and the irises of the eyes

endosteum

-a single cell layer of connective tissue that lines the internal surfaces of all cavities within bones, such as the medullary cavity of the diaphyses and the smaller cavities in spongy and compact bone -includes osteoblasts, osteoclasts, and osteochondral progenitor cells

cuticle

-a single layer of cells also containing hard keratin -the edges of the cuticle cells overlap like shingles on a roof

ruffled border

-a specialized reabsorption specific area of the membrane -acidic vesicles fuse with the membrane of the ruffled border, while ATP powered H+ pumps and protein digesting enzymes are inserted into the membrane of the ruffled border -secretion of H+ creates an acidic environment within the sealed compartment, which causes decalcification of the bone matrix -the protein digestion enzymes are secreted into the sealed compartment and digest the organic, protein component of the bone matrix -after breakdown of the matrix, the degradation products are removed by a trancytosis mechanism, whereby products enter the osteoclast and move across the cytoplasm to the other side of the osteoclast -there, the degradation products are secreted into the extracellular space, enter the blood, and are used elsewhere in the body

what is a major burn?

-a third degree burn over 10% or more of the BSA -a second degree burn over 25% or more of the BSA -a second or third degree burn of the hands, feet, face, genitals, or anal region (facial burns are often associated with damage to the respiratory tract, and burns of joints often heal with scar tissue formation that limits movement)

moderate burn

-a third degree burn over 2-10% of the BSA -a second degree burn over 15-25% of the BSA

minor burn

-a third degree burn over less than 2% of the BSA -second degree burn over less than 15% of the BSA

carotene

-a yellow pigment found in plants such as carrots and corn -humans usually ingest carotene and use it as a source of vitamin A -is lipid soluble and when large amounts of carotene are consumed, the excess accumulates in the stratum corneum and in adipocytes of the dermis and subcutaneous tissue, causing the skin to deveop a yellowish tint (slowly dissapears as carotene intake is reduced)

spongy bone

-appears porous -has less bone matrix and more space than compact bone -consists of interconnecting rods or plates of bone called trabeculae -between the trabeculae are spaces, which are filled with bone marrow and blood vessels -most trabeculae are thin and consist of several lamellae with osteocytes located in lacunae between the lamellae -each osteocyte is associated with other osteocytes through canaliculi-no blood vessels penetrate the trabeculae, so osteocytes must obtain nutrients through their canaliculi -the surfaces of trabeculae are covered with a single layer of cells consisting mostly of osteoblasts with a few osteoclasts -trabeculae are oriented along the lines of mechanical stress within a bone

what are the two types of cartilage growth?

-appositional growth: chondroblasts in the perichondrium add new cartilage to the outside edge of the existing cartilage. The chondroblasts lay down new matrix and add new chondrocytes to the outside of the tissue -interstitial growth: chondrocytes in the center of the tissue divide and add more matrix in between the existing cells

muscles/arrector pilli

-arrector pilli are smooth muscle cells that are associated with each hair follicle -arrector pilli extend from the dermal root sheath of the hair follicle to the papillary layer of the dermis -normally, the hair follicle and the hair inside it are at an oblique angle to the surface of the skin-but when an arrector pilli muscle contracts-they pull the follicle into a more perpendicular position, causing the hair to stand on end -this movement of hair follicles produce raised areas called goose bumps

aging

-as the body ages, the skin is more easily damaged because the epidermis thins and the amount of collagen in the dermis decreases -skin infections are more likely and skin repair occurs more slowly -decrease in number of elastic fibers in the dermis and a loss of adipose tissue from the subcutaneous tissue cause the skin to sag and wrinkle ( retin A treats wrinkles but makes the skin more sensitive to the sun) -skin becomes drier with age as sebaceous gland activity decreases -decreases in the activity of sweat glands and the blood supply to the dermis result in a reduced ability to regulate body temp (can experience heat exhaustion which can lead to death) -functioning melanocytes decrease-but increase in some areas causing age spots -lack of melanin also results in white and grey hairs

hair growth and rate

-average rate of hair growth is 0.3 mm per day -cutting, shaving, or plucking hair does not alter the growth rate of the character of the hair, although the hair can feel coarse and bristly because the short hairs are less flexible -maximum hair length is determined by the rate of hair growth and the length of the growing phase: example: scalp hair can become very long but eyelashes are short

Thin skin

-covers all of the body except for palms of hand, soles of feet, and fingertips -more flexible than thick skin -each of its strata contains fewer layers of cells than are found in thick skin -stratum granulosum consists of one or two layers of cells -stratum lucidum is generally absent -hair is found only in thin skin -thin and thick skin refer to the epidermis only

interstitial lamellae

-between the osteons -remnants of concentric or circumfrential lamellae that were partially removed during bone remodeling

temperature regulation

-body temp is affected by blood flow through the skin -when blood vessels in the dermis dilate, more warm blood flows from deeper structures to the skin, and heat loss increases -body temp tends to increase as a result of exercise, fever, or a rise in environmental temperature -in order to maintain homeostasis, this excess heat must be lost-the body accomplishes this by producing sweat, the sweat spreads over the surface of the skin, as it evaporates, the body loses heat -when blood vessels in the dermis constrict, less warm blood flows from deeper structures to the skin, and heat loss decreases. if body temperature begins to drop below normal, heat can be conserved by a decrease in the diameter of dermal blood vessels -the hair on the head is an effective insulator

osteoclasts

-bone destroying cells -perform reabsorption, or breakdown, or bone that mobilizes crucial Ca2+ and phosphate ions for use in many metabolic processes -as bone is broken down, the Ca2+ goes back into the blood, these cells are massive, multinucleated cells whose differentiation follows a complex pathway -they are derived from red bone marrow cells that also differentiate into monocytes. these precursors attach to the bone matrix, where direct contact with osteoblasts is required to allow eventual maturation into functional osteoclasts -mature osteoclasts carry out bone reabsorption through a multi-step process (first, the osteoclasts must access the bone matrix, the osteoblasts lining the connective tissue around bone regulate the movement of mature osteoclasts into a bone remodeling area. once the osteoclasts have come in contact with the bone surface, they form attachment structures via interactions with cell surface proteins called integrins . structures called podosomes develop and form a sealed compartment under the osteoclast. the osteoclast cell membrane then further differentiates into a highly folded form called the ruffled border)

osteoblasts

-bone forming cells -have an extensive endoplasmic reticulum and numerous ribosomes -produce collagen and proteoglycans, which are packaged into vesicles by the golgi apparatus and released from the cell by exocytosis -release matrix vesicles: which contain high concentrations of Ca++ and PO43-, stimulates further hydroxyapetie formation and mineralization of the matrix when released from vesicles -form new bone through the process of ossification

lanugo

-by the fifth or six month of fetal development, delicate, unpigmented hair called lanugo has developed and covered the fetus

full thickness burns

-called third degree burns -the epidermis and the dermis are completely destroyed, and deeper tissue may be involved -often surrounded by first and second degree burns -usually painless because the sensory receptors have been destroyed -appear white, tan, brown, black, or deep cherry red -skin can regenerate only from the edges and skin grafts are often necessary

bone shapes

-can be long, flat, short, or irregular -long bones are longer than they are wide (most of the bones of the upper and lower limbs are long bones) -flat bones have relatively thin, flattened shape and are usually curved (certain skull bones, the ribs, breastbone, shoulder blades) -short bones are round or nearly cube shaped (bones of the wrist, and ankle) -irregular bones: have shapes that do not readily fit into the other three categories and includes the vertebrae and facial bones

Melanin production during pregnancy

-certain hormones such as estrogen and melanocyte-stimulating hormone, cause the mothers body to increase melanin production, which causes the darkening of the nipples, areolae, and genitalia -the cheekbones, forehead, and chest also may darken, resulting in the "mask of pregnancy" -a dark line of pigmentation may appear on the midline of the abdomen -diseases such as addison disease also cause increased pigmentation due to increased secretion of adrenocorticotropic hormone and melanocyte-stimulating hormone

concentric lamellae

-circular layers of bone matrix that surround the central canal

reticular layer of the dermis

-composed of dense, irregular connective tissue -the main layer of the dermis -continuous with the subcutaneous tissue and forms a mat of irregularly arranged fibers that are resistant to stretching in many directions

perichondrium

-covers most cartilage -is a protective connective tissue sheath -double layered outer layer of dense, irregular connective tissue containing fibroblasts -the inner, more delicate layer has fewer fibers and contains chondroblasts -blood vessels and nerves penetrate the outer layer of the perichondrium, but do not enter the cartilage matrix, so nutrients must diffuse through the cartilage matrix to reach the chondrocytes

skin grafts

-deep partial thickness and full thickness burns take a long time to heal and often form scar tissue with disfiguring and debilatating wound contracture -in a split skin graft, the epidermis and part of the dermis are removed from another part of the body and placed over the burn -interstitial fluid from the burned area nourishes the graft until its dermis becomes vascularized -at the graft donation site, part of the dermis is still present where epithelial cells form new epidermis

corn

-develops in areas of skin that are over bony prominences -cone-shaped structure -the base of the cone is at the surface, but the apex extends deep into the epidermis, and pressure on the corn may be very painful -can develop in both thin and thick skin

partial thickness burns

-divided into first and second degree burns -first degree burns: involve only the epidermis and may result in redness, pain, and slight edema (swelling): can be caused by sunburn or brief exposure to hot or cold objects, they heal in about a week without scarring -second degree burns: damage the epidermis and the dermis. minimal dermal damage causes redness, pain, edema, and blisters. healing takes two weeks and no scarring results. however, if the burn goes deep into the dermis, the wound appears red, tan, or white, may take several months to heal, and might scar -in all second degree burns, the epidermis regenerates from epithelial tissue in hair follicles and sweat glands, as well as from the edges of the wound

epithelial root sheath

-divided into internal and external parts -at the opening of the follicle, the external epithelial root sheath has all the strata found in thin skin -deeper in the hair follicle, the number of cells decreases until, at the hair bulb, only the stratum basale is present (important consequences for skin repair) -the internal epithelial root sheath has raised edges that mesh closely with the raised edges of the hair cuticle and hold the hair in place -when a hair is pulled out, the internal epithelial root sheath usually comes out as well, and is plainly visible as a whitish tissue around the hair

hair structure

-divided into the shaft, and the root Shaft: protrudes above the surface of the skin Root: located below the surface, the base of the root is expanded to form the hair bulb -most of the root and the shaft are composed of columns of dead, keratinized epithelial cells arranged in three concentric layers: the medulla, the cortex, and the cuticle

structure of flat, short, and irregular bones

-flat bones contain an interior framework of spongy bone sandwhiched between two layers of compact bone -short and irregular bones have a composition similar to the epiphysis of long bones-compact bone surfaces surrounding a spongy bone center with small spaces that are usually filled with marrow -short and irregular bones are not elongated and have no diaphysis, but certain regions of these bones such as the processes and projections have epiphyseal growth plates and therefore small epihyses -some of the flat and irregular bones of the skull have air filled spaces called sinuses, which are lined by mucous membranes

callus

-forms in areas where skin is subjected to friction or pressure -occurs when the stratum corneum of the epidermis increases in thickness -provides added protection -can develop in both thin and thick skin

epiphyseal plate

-growth plate -located between the epiphysis and the diaphysis -growth in bone length occurs at the epiphyseal plate -when bone stops growing in length, the epiphyseal plate becomes ossified and is called the epiphyseal line

hair growth

-hair is produced in cycles that involve a growth stage and a rest stage -during the growth stage, the hair increases in length as new matrix cells are produced, differentiate, become keratinized, and die -the hair grows longer as cells are added at the base of the hair root -eventually, hair growth stops, the hair follicle shortens, and holds the hair in place -a resting period follows, after which a new cycle begins and a new hair replaces the old hair, which falls out of the hair follicle (losing a hair normally means that the hair is being replaced) -the length of each stage depends on the hair: eyelashes grow for 30 days and rest for 105, scalp hairs grow for 3 years and rest for 1-2 years (loss of approx 100 scalp hairs per day is normal)

Thick skin

-has all five epithelial strata -stratum corneum has many layers of cells -found in areas subject to pressure or friction (palms of the hand, soles of the feet, fingertips) -thin and thick skin refer only to the epidermis

compact bone

-has more matrix and is denser with fewer pores than spongy bone -blood vessels enter the substance of the bone itself, and the lamalllae of compact bone are primarily oriented around those blood vessels

chondroblasts

-hyaline cartilage chondroblasts produce a matrix surrounding themselves -by the time the matrix has surrounded a chondroblast, the cell has differentiated into a chondrocyte (a rounded cell that occupies a space called a lacuna, within the matrix) -the matrix contains collagen, which provides strength, and proteoglycans, which make cartilage resilient by trapping water

articular cartilage

-hyaline cartilage that covers the ends of bones, where they come together to form joints -has no perichondrium, blood vessels, or nerves

Burns

-injury to a tissue caused by heat, cold, friction, chemicals, electricity, or radiation -classified according to the extent of surface area involved and the depth of the burn -can be classified as either partial thickness or full thickness burns

subcutaneous tissue

-lies deep to the skin -attaches the skin to the underlying bone and muscle and supplies the skin with blood vessels and nerves -consists of loose connective tissue with collagen and elastic fibers -the main types of cells within the subcutaneous tissue are fibroblasts, adipocytes, and macrophages -is not part of the skin and is sometimes called the hypodermis -half of the bodies stored lipids are in the subcutaneous tissue, where they function as insulation, padding, and a source of energy -can be used to estimate the total body fat by pinching the skin at selected locations and measuring the thickness of the skin fold and underlying subcutaneous tissue (the thicker the fold, the greater amount of total body fat)

sebaceous glands

-located in the dermis -simple or compound aleveolar glands that produce sebum (an oily, white substance rich in lipids) -sebaceous glands are classified as holocrine glands because sebum is released by the lysis and death of secretory cells -most sebaceous glands are connected by a duct to the upper right part of the hair follicles, from which the sebum oils the hair and the skin surface -this secretion prevents drying and protects against some bacteria (a few sebaceous glands located in the lips, the eyelids/meibomian glands, and the genitalia are not associated with hairs but open directly onto the skin surface)

effect of location of pigments

-location of pigments and other substances in the skin affects the color produced -the deeper within the dermis or subcutaneous tissue any dark pigment is located, the bluer the pigment appears because of the light scattering effect of the overlying tissue -effect causes the blue color of tattoos, bruises, and some superficial blood vessels

papillary layer of the dermis

-loose connective tissue with thin fibers that are somewhat loosely arranged -contains blood vessels that supply the overlying epidermis with oxygen and nutrients, removes waste products, and aid in regulating body temperature -the dermal papillae under the thick skin of the palms of the hands and soles of the feet lie in paralell, curving ridges that shape the overlying epidermis into fingerprints and footprints (ridges increase friction and improve the grip of the hands and feet-everyone has unique fingerprints and footprints-even identical twins)

dermis

-made up of connective tissue (cells distributed widely in an extensive extracelluar matrix that includes protein fibers) -cells in the dermis are: fibroblasts, adipocytes, and macrophages -collagen is the main type of protein fiber in the extracellular matrix, but elastic and reticular fibers are present too -dermis contains blood vessels that allow for nutrient and waste exchange to the cells of the dermis and the living cells of the epidermis -dermis also contains nerve endings, hair follicles, smooth muscles, glands, and lymphatic vessels

lamellar bone

-mature bone that is organized into thin, concentric sheets or layers approximately 3-7 micrometers thick called lamallae -the collagen fibers of one lamallae lie parallel to one another, but at an angle to the collagen fibers in the adjacent lamallae -osteocytes, within their lacunae, are arranged in layers sandwiched between lamallae

hair color

-melanocytes within the hair bulb matrix produce melanin and pass it to keratinocytes in the hair cortex and medulla -varying amounts and types of melanin cause different shades of hair color ex) blonde hair has little brown-black melanin, whereas jet black hair has the most intermediate amounts of melanin account for brown hair -red hair is caused by varying amounts of red type melanin- hair can also contain black-brown and red melanin -with age, the amount of melanin in hair can decrease, causing hair color to fade or become white -gray hair is usually a mixture of unfaded, faded, and white hairs -hair color is controlled by several genes, and dark hair color is not necessarily dominant over light

mammary glands

-modified apocrine sweat glands located in the breasts -produce milk

ceruminous glands

-modified eccrine sweat glands located in the ear canal (external auditory canal) -cerumen/ear wax is composed of the combined secretions of ceruminous glands and sebaceous glands -cerumen and hairs in the ear canal protect the tympanic membrane by preventing dirt and small insects from moving too deeply into the ear canal but an accumulation of cerumen can block the ear canal and make hearing more difficult

terminal hairs

-near the time of birth -long, coarse, pigmented hairs -replace the lanugo of the scalp, eyelids, and eyebrows

stretch marks

-occur when the skin is overstretched, and the dermis ruptures and leaves lines that are visible through the epidermis -can develop on the abdomen and breasts of a women during pregnancy or on the skin of athletes who have quickly increased muscle size by intense weight training

osteocytes

-once an osteoblast has secreted enough bone matrix to become surrounded by it, the cell is an osteocyte -retain their connections to neighboring osteocytes through their cell extensions -become relatively inactive, compared with most osteoblasts, but it is possible for them to produce the components needed to maintain the bone matrix -the spaces without matrix, but occupied by the osteocyte cell bodies are called lacunae -the spaces occupied by the osteocyte cell extensions are called canaliculi (the extensions of bone cells are in contact with one another through the canaliculi. instead of diffusing through the mineralized matrix, nutrients and gases can pass through the small amount of fluid surrounding the cells in the canaliculi and lacunae or pass from cell to cell through the gap junctions connecting the cell extensions)

perforating canals

-osteocytes receive nutrients and eliminate waste products through the canal system within compact bone -blood vessels from the periosteum or medullary cavity enter the bone through perforating canals -run perpendicular to the length of the bone and are not surrounded by concentric lamallae, but instead, pass through the concentric lamalle of osteons -central canals receive blood vessels from perforating canals -nutrients in the blood vessels enter the central canals, pass into the caniculi, and move through the cytoplasm of the osteocytes that occupy the canniculi and lacunae to the most peripheral cells at the edge of the osteon -waste products are removed in the reverse direction

what are the two tissue layers of the dermis

-papillary layer: superficial layer, derives its name from projections called dermal papillae, that extend toward the epidermis -reticular layer: deeper layer

what are the factors that determine skin color?

-pigments in the skin -blood circulating through the skin -thickness of the stratum corneum

hair

-presence of hair is one of the characteristics of all mammals -if the hair is dense and covers most of the body surface, it is called fur -in humans, hair is found everywhere on the skin except for the palms, the soles, the lips, the nipples, parts of the external genitalia, and the distal segmens of the fingers and toes

melanocytes

-produces melanin -irregularly shaped cells with many long processes that extend between the keratinocytes of the stratum basale and the stratum spinosum -produce and package melanin into vesicles called melanosomes

sensation

-receptors in the skin can detect pain, heat, cold, and pressure -the epidermis and dermal papillae are well supplied with touch receptors -the dermis and deeper tissues contain pain, heat, cold, touch, and pressure receptors -hair follicles (but not the hair) are well innervated, and sensory receptors surrounding the base of hair follicles can detect hair movement

what are the major glands of the skin?

-sebaceous glands -sweat glands

vellus hairs

-short, fine, and usually unpigmented -replace the lanugo on the rest of the body (everywhere except the scalp, eyelids, and eyebrows) -at puberty, terminal hair, especially in the pubic and axillary regions, replaces much of the vellus hair -in males, terminal hairs replace the vellus hairs of the face to form the beard -pubic and axillary hairs may serve as wicks for dispersing odors produced by secretions from specialized glands in the pubic and axillary regions -pubic hair protects against abrasion during intercourse and axillary hair reduced friction when the arms move

apocrine sweat glands

-simple, coiled, tubular glands that usually open into hair follicles superficial to the opening of the sebaceous glands -found in the axillae and genitalia and around the anus -do not help regulate temperature in humans -become active at puberty as a result of sex hormones -secretions contain organic substances such as 3-methyl-2-hexenoic acic: essentially odorless when first released but are quickly metabolized by bacteria to cause what is commonly known as body odor (many mammals use scent as a means of communication, and physiologists have suggested that the activity of apocrine sweat glands may signal sexual maturity)

eccrine sweat glands

-sometimes called merocrine sweat glands -most common type of sweat gland -simple, coiled, tubular glands that open directly onto the surface of the skin through sweat pores -can be divided into two parts: the deep, coiled portion, which is located mostly in the dermis, and the duct: which passes to the skin surface -the coiled part of the gland produces isotonic fluid that is mostly water but contains some salts (mainly NaCl and small amounts of ammonia, urea, uric acid, and lactic acid) -as this fluid moves through the duct, NaCl moves by active transport from the duct back into the body, thereby conserving salts -the resulting hyposmotic fluid that leaves the duct is called sweat (when the body temp starts to rise above normal, the sweat glands produce sweat, which evaporates and cools the body. sweat can also be released in the palms, soles, and axillae as a result of emotional stress) -eccrine sweat glands are distributed over a majority of the areas of the body but are most numerous in the palms of the hands and soles of the feet: are not found on the margin of the lips, the labia minora, and the tips of the penis and clitoris)

osteochondral progenitor cells

-stem cells that can become osteoblasts or chondroblasts -located in the inner layer of the perichondrium and in layers of connective tissue that cover bone (periosteum and endosteum) -osteoblasts are derived from osteochondral progenitor cells and osteocytes are derived from osteoblasts

cortex

-surrounds the medulla -forms the bulk of the hair -the cells of the cortex contain hard keratin -covered by the cuticle

racial variations in skin color are determined by...

-the amount and types of melanin produced by the melanocytes -the size, number, and distribution of the melanosomes -many genes are responsible for skin color, but a single mutation can prevent the manufacture of melanin (albinism) -exposure to ultraviolet light darkens the melanin already present in the skin and stimulates melanin production, resulting in tanning

medulla

-the central axis of the hair -consists of two or three layers of cells containing soft keratin -surrounded by the cortex

hair papilla

-the dermis of the skin projects into the hair bulb as hair papilla -within the hair papilla are blood vessels that provide nourishment to the cells of the hair matrix

cleavage lines

-the elastic and collagen fibers are oriented more in some directions than in others and produce cleavage lines/tension lines in the skin -an incision made parallel to the cleavage lines is less likely to gap than an incision made across them -the development of infections and the formation of scar tissue are reduced in wounds where the edges are closer together

Melanin production

-the enzyme tyrosinase converts the amino acid tyrosine to dopaquinone -dopaquinone an be converted to a variety of related molecules, most of which are brown to black pigments, but some of which are reddish or yellowish -determined by genetic factors, exposure to light, and hormones -genetic factors are primarily responisble for the variations in skin color among different races and among people of the same race -number of melanocytes in the skin is relatively the same for all humans, regardless of race

woven bone

-the first type of bone that osteoblasts form during ossification -fairly weak bone -the collagen fibers are randomly oriented in many directions -after woven bone formation, osteoclasts break down the woven bone and osteoblasts build new matrix -woven bone is remodeled into a stronger, more permanent type called lamellar bone (the process of removing old bone and adding new bone is called bone remodeling)

ossification

-the formation of new bone by osteoblasts -occurs by appositional growth on the surface of previously exisiting material, either bone or cartilage -bone matrix produced by osteoblasts covers the older bone surface and surrounds the osteoblast cell bodies and extensions: the result is a new layer of bone

osteon

-the functional unit of a long bone is an osteon -an osteon is composed of concentric rings of matrix, which surround a central tunnel and contain osteocytes -a cross section resembles a circular target, the bulls eye of the target is the central canal and concentric lamallae form the rings

matrix

-the hair bulb is an expanded knob at the base of the hair root -inside the hair bulb is a mass of undifferentiated epithelial cells called matrix -the matrix produces the hair and the internal epithelial root sheath

medullary cavity

-the hollow center in the diaphysis of long bones -filled with marrow (red marrow is the site of blood cell formation and yellow marrow is mostly adipose tissue). yellow marrow completely replaces the red marrow in the long bones of the limbs, except for some red marrow in the proximal part of the arm bones and thigh bones

pattern baldness

-the most common kind of permanent hair loss -hair follicles shrink and revert to producing vellus hair, which is very strong, transparent, and for practical purposes, invisible -eventually, hair production in these smaller follicles may completely cease -genetic factors and the hormone testosterone are involved in causing pattern baldness

nails continued

-the nail root extends distally from the nail matrix -the nail also attaches to the underlying nail bed, which is located between the nail matrix and the hypochonium -the nail matrix and bed are composed of epithelial tissue, with a stratum basale that gives rise to the cells that form the nail -the nail matrix is thicker than the nail bed and produces nearly all of the nail -the nail bed is visible through the clear nail and appears pink because of blood vessels in the dermis -a small part of the nail matrix, the lunula, is seen through the nail body as a whitish, crescent shaped area at the base of the nail: it is seen best on the thumb and appears white because the blood vessels do not show through the thicker nail matrix -as the nail forms in the nail matrix and bed, it slides over the nail bed toward the distal end of the digit -fingernails grow more rapidly than toe nails -grow continuously throughout life and do not have a resting phase

circumfrential lamellae

-the outer surfaces of compact bone are formed by circumferential lamellae -thin plates that extend around the bone

epiphysis

-the part of a long bone that develops from a center of ossification distinct from that of the diaphysis -each long bone of the arm, forearm, thigh, and leg has one or more epiphysis on each end of the bone -each long bone of the hand and foot has one epyphysis, which is located on the proximal or distal end of the bone

dermal root sheath

-the portion of the dermis that surrounds the epithelial root sheath

Excretion

-the removal of waste products from the body -in addition to water and salts, sweat contains a small amount of waste products, including urea, uric acid, and ammonia -even when large amounts of sweat are lost, the quantity of waste products eliminated in the sweat is insignificant because the urinary system excretes most of the body's waste products

sweat glands

-there are two types of sweat/sudoriferous glands: eccrine glands and apocrine glands -appocrine sweat glands also release some of their secretions in a merocrine fashion, and possibly some in a holocrine fashion -eccrine sweat glands release their secretions in a merocrine fashion

structure of a long bone

-traditional model for overall bone structure -diaphysis: shaft, composed primarily of compact bone, but can also contain some spongy bone. the end of a long bone is mostly spongy bone, with an outer layer of compact bone (the primary ossification center is within the diaphysis) -within joints, the end of a long bone is covered with hyaline cartilage called articular cartilage

hair follicle

-tube-like invagination of the epidermis that extends into the dermis -a hair develops and grows within each hair follicle -consists of a dermal root sheath and an epithelial root sheath

nerve endings in the dermis

-varied in structure and function -free-nerve endings for pain, itch, tickle, and temperature sensation -hair follicle receptors for light touch -pacinian corpuscles for deep pressure -meissners corpuscles for detecting simultaneous stimulation at two points on the skin -ruffini end organs for sensing continuous touch or pressure

amount of adipose tissue...

-varies with age, sex, and diet -babies have more adipose tissue than adults -women have more adipose tissue than men (especially over the thighs, butt, and breasts) -amount of adipose tissue is also responsible for some of the differences in body shape between individuals of the same sex

melanosomes

-vesicles that contain melanin -move into the cell processes of the melanocytes -keratinocytes phagocytize the tips of the melanocyte cell processes, thereby aquiring melanosomes (although all keratinocytes can contain melanin, the only cells that produce it are melanocytes)

central canal

-vessels that run paralell to the long axis of the bone are contained within the central canals -lined with endosteum and contain blood vessels, nerves, and loose connective tissue -osteocytes are located in lacunae between the lamellar rings, and canaliculi radiate between lacunae across the lamellae

vitamin D production

-vitamin D functions as a hormone involved in the regulation of calcium homeostasis -its primary role is to stimulate the uptake of calcium and phosphate from the intestines-adequate levels of these minerals are necessary for normal bone metabolism, and calcium is required for normal nerve and muscle function -vitamin D synthesis begins in skin exposed to ultraviolet light, and people can produce all the vitamin D they require by this process if enough ultraviolet light is available - but because people live indoors and wear clothing, their exposure to ultraviolet light may not be adequate for the manufacture of sufficient vitamin D -vitamin D can also be ingested and absorbed in the small intestine: liver, egg yolks, dairy products, fortified milk, vitamin pills

cholecalciferol and calcitriol

-vitamin D synthesis involves a precursor molecule, 7-dehydrocholesterol, which is stored in the skin -when exposed to ultraviolet light, the precursor molecule is converted to cholecalciferol, which is released into the blood and modified first by the liver and later by the kidneys to form active vitamin D3, calcitriol

functions of the skeletal system

1) body support: rigid, strong bone is well suited for bearing weight and is the major supporting tissue of the body. Cartilage provides a firm, yet flexible support within certain structures, such as the nose, external ear, thoracic cage, and trachea. Ligaments are strong bands of fibrous connective tissue that holds bones together 2) organ protection: bone is hard and protects the organs it surrounds ex) skull encloses and protects the brain 3) body movement: skeletal muscles attach to bones by tendons, which are strong bands of connective tissue. contraction of the skeletal muscles moves the bones, producing body movements. Joints, which are formed where two or more bones come together, allow movement between bones. smooth cartilage covers the ends of bones within some joints, allowing the bones to move more freely. ligaments allow some movement between bones but prevent excessive movements 4) mineral storage: some minerals in the blood are stored in bone. if blood levels of these minerals decrease, the minerals are released from the bone into blood. the principle minerals stored are calcium and phosphorus, two minerals essential for many physiological processes. adipose tissue is also stored within bone cavities. if needed, the lipids are released into the blood and used by other tissues as a source of energy 5) blood cell production: many bones contain cavities filled with red bone marrow, which gives rise to blood cells and platelets

four components of the skeletal system

1) bones 2) cartilage 3) tendons 4) ligaments

integumentary system: protection

1) the skin protects the underlying structures from mechanical damage. the dermis provides structural strength, preventing tearing of the skin. the stratified epithelium of the epidermis protects against abrasion. as the outer cells of the stratum corneum slough off, they are replaced by cells from the stratum basale. calluses develop in areas subject to heavy friction or pressure 2) the skin prevents microorganisms and other foreign substances from entering the body. secretions from skin glands produce an environment unsuitable for some microorganisms. the skin also contains components of the immune system that act against microorganisms 3) melanin absorbs ultraviolet light and protects underlying structures from its damaging effects 4) hair provides protection in several ways. the hair on the head acts as a heat insulator and protects against ultraviolet light and abrasion. the eyebrows keep sweat out of the eyes, the eyelashes protect the eyes from foreign objects, and hair in the nose and ears prevents dust and other materials from entering. axillary and pubic hair are a sign of sexual maturity and protect against abrasion 5) nails protect the ends of the fingers and toes from damage and can be used in defense 6) the intact skin plays an important role in reducing water loss because its lipids act as a barrier to the diffusion of water (lipid soluble substances readily pass through the epidermis. lipid soluble medications can be administered by applying them to the skin, after which the medication slowly diffuses through the skin and into the blood)

what are the three types of cartilage?

hyaline, fibrocartilage, elastic -hyaline cartilage is most intimately associated with bone -most bones in the body start out as hyaline cartilage -growth in bone length and bone repair often involve making hyaline cartilage first, then replacing it with bone