Chapter 6

Perichondrium

Dense irregular connective tissue membrane covering cartilage; acts as a reinforcer to resist outward expansion when cartilage is compressed; vontain blood bessles that nourish cartilage cells

hyaline cartilage

provides support with flexibility and resistance; most abundant skeletal cartilage;

articulate cartilage

cover the ends of most bones and movable joints

costal cartilage

connect the ribs to the sternum (breast bone)

Respiratory cartilage

forms the skeleton of the larynx (voice box) and reinforces the other respiratory pathways

nasal cartilage

support the external nose

elastic cartilage

contains stretchy elastic fibers so they can stand up to repeat bending; found in the ear and epiglottis

Fibrocartilage

highly compressible with great tensile strength consisting of rough parallel rows of chondrocytes alternating with thick collagen fibers

cartilage

has a flexible matrix that can accommodate mitosis; ideal tissue to rapidly lay down the embryonic skeleton and to provide for new skeletal growth

appositional growth

growth in width; cartilage forming cells in the surrounding perichondrium secrete new matrix against the external face of existing cartilage tissues

interstitial growth

growth in length; lacunae bound chondrocytes divide and secrete new matrix expanding cartilage within; ends during adolescence when skeleton stops growing

Support (bone function)

provide a framework that supports the body and cradles its soft organs

Protection (bone function)

The fused bones of the skull protect the brain. The vertebrae surround the spinal cord, and the rib cage helps protect the vital organs of the thorax

Anchorage (bone function)

skeletal muscles (attach bones by tendons) use bones as levers to move the body and it's parts

mineral storage (bone functions)

bone is a reservoir for minerals- most importantly calcium and phosphate

blood cell formations (bone functions)

most blood cell formation (hematopoiesis) occurs in the red marrow of certain bones

Triglycerides (fat) storage (bone function)

Fat is a source of energy for the body and is stored as yellow marrow in the cavities of long bones

hormone production (bone function)

Bones produce osteocalcin, a hormone that helps to regulate insulin secretion, glucose homeostasis, and energy expenditure.

axial skeleton

Portion of the skeletal system that consists of the skull, rib cage, and vertebral column; protect support or carry other body parts

appendicular skeleton

consists of the bones of the upper and lower limbs and the girdles (shoulder and hip bones) and the bones that anchor the limbs to the axial skeleton; help us move place to place (locomotion)

long bones

longer than they are wide; consists of a shaft plus two ends which are often expanded; all limbs except patellar and ankle bone and finger

short bones

roughly cube shaped (wrist and ankle)

sesamoid bones

round bones found near joints; a special type of short bone that form in a tendon (patella); some reduce frictions and modify pressure for abrasions and tears; others alter direction of pill tendon

flat bones

thin, flattened, and usually curved, two thin layers of compact sandwiching spongey bone; skull, ribs, sternum

gross anatomy

Study of structures that can be seen with the naked eye; every bone has a dense outer layer that looks smooth and solid to the naked eye

compact bone

Hard and dense, but not solid, bone tissue that is beneath the outer membrane of a bone; external layer

spongy bone (trabecular bone)

Layer of bone tissue that has many small spaces and is found just inside the layer of compact bone

trabeculae

supporting bundles of bony fibers in cancellous (spongy) bone; a honeycomb of small needle like or flat pieces

bone structure

thin plates of spongy bones covered by compact bone; bone marrow

the connective tissue membrane covering the compact bone

periosteum and endosteum

Diaphysis (shaft-long bone)

Compact bone collar surrounds medullary (marrow) cavity; forms the long axis of the bone

Medullary (yellow marrow) cavity

stores adipose tissue in adults; makes red blood cells in infants

Epiphysis

End of a long bone; an outer shell of compact bone

epiphyseal line

remnant of the epiphyseal plate, seen in adult bones

epiphyseal plate

growth plate, disc of hyaline cartilage that grows during childhood to lengthen the bone

metaphysis

where diaphysis and epiphysis meet

Periosteum

Double-layered connective tissue that covers and nourishes the external surface bone (except joint surfaces)

Osteogenitor cells

primitive stem cells that give rise to most bone cells

osteoclasts

bone destroying cells

osteoblasts

bone forming cells look

Endosteum

delicate membrane covering internal surfaces of bone

Nutrient Vein and Artery

main vessels serving diaphysis (shaft); run through a hole in the wall of a diaphysis

hematopoietic tissue

red bone marrow

medullary cavity of the diaphysis and all areas of spongy bone

Where is red bone marrow found in newborns

in the cavities between sponger bones in the skull, sternum, ribs, clavicles, scapulae, hip bones, vertebrae, femur, and humorous

where is red bone marrow found in adults

Osteopeogenitor cells

divide and form osteoblasts; mitotically active stem cells found in the membranous periosteum and endosteum; in growing bones they are flattened or squamous cells

Osteoblasts

bone forming cells that secrete bone matrix; actively mitotic;

Osteoid

unmineralized bone matrix composed of proteoglycans, glycoproteins, and collagen

Osteocytes

mature bone cells that conform to their shape; monitor and maintain the bone matrix; act as a stress or strain sensors and respond to mechanical stimuli; trigger bone remodeling; communicate to blasts and cytes

Bone lining cells

flat cells found on bone surfaces where bone remodeling is not going on; help maintain the matrix

Osteoclasts

bone destroying cells; giant multinucleate cells located at sites of bone restoration; derive from white blood cells;

Osteon

structural unit of compact bone; tiny weight bearing pillars; group of hollow tubes of bone matrix

central canal

runs through core of osteon, contains blood vessels and nerve fibers that serve the osteon cells

perforating canals

lie at right angles to the central canals and connect the blood and nerve supply of the periosteum to that of the central canals and the marrow cavity

Endosteum

membranous lining of the hollow cavity of the bone;lines canals

Canaliculi

Hairlike canals that connect lacunae to each other and the central canal; tie all the osteocytes in a mature osteon together allowing them to communicate and permitting nutrients and waste to be relayed from one osteocyte to the next

Canaculi and gap junctions

allows bone cells to be well nourished because matrix is impermeable to nutrients

interstitial lamellae

fill spaces between osteons; they either fill gaps between forming osteons or are remnants of osteons that have been cut through by bone remodeling

circumferential lamellae

extends around the entire circumference of the diaphysis and effectively resists twisting of long bone; located in between periosteum and endosteum

spongy bone

Layer of bone tissue having many small spaces and found just inside the layer of compact bone.

Trabeculaue

spicules of bony material found in spongy bone; help the bones resist stress; contain irregularly arranged lamellae and osteocytes interconnected by canaliculi; no osteons

capillaries

in the endosteum surrounding trabeculae; nutrients reaches the osteocytes of spongy bones by diffusing the canaliculi

organic and inorganic compounds

what makes bone extremely strong and durable

soft organic components of bone

allow it to resist tension; include bone cells and osteoids

hard organic components of bone

allow it to resist compression; includes mineral salts

half; fully

healthy bone is _ as strong as steel in resisting compression and ___ as strong in resting tension.

bone cells and osteoids- part of the matrix

organic components of bone

ground substance and collagen fibers that are secreted by osteoporosis

what contributes to a bone structure and flexibility and tensile strength that allows it to resist stretch and twisting

sacrificial bones

break under stress to dissipate shock and quickly reform; in osteons

sacraficial bones in or between collagen molecules

where does bone resilience come from

inorganic hydroxyapatites

mineral salts account for almost 2/3 of the weight of bone; largely calcium phosphate present as tiny tightly packed needle like crystals in or around collagen fibers in the extracellular matrix

it's hardness that allows it to resist tensions

most notable characteristic of the bone

mineral salts

why bones last so long after death

ossification and osteogenesis

names for the process of bone tissue formation

formation of boney skeleton

ossification in embryos

ossification

process of bone formation; goes on until early adulthood as the body increases in size

remodeling and repair

ossification in adults

endochondral ossification

bone develops by replacing hyaline cartilage; results in endochondrial bone

intramembranous ossification

bone develops from a fibrous membrane; results in membranous bone

flexible structures

accommodate mitosis in the embryonic skeleton; membrane and cartilage

bones below the base of the skull

what bones are formed by endochondral ossification

intermembranous ossification

forms the cranial bones of the skull and the clavicles; forms mostly flat bones

interstitial growth of the epiphyseal plate and replaced by long bone

how bones lengthen during infancy and youth

appositional growth

increase in bone thickness

resting zone

the cartilage is relatively inactive on the side of the epiphyseal plate facing the epiphysis

continuous remodeling- of the epiphyseal ends to maintain the proportion between the diaphysis and epiphysis

what process accompanies longitudinal growth

epiphyseal plate closure

longitudinal bone growth ends when the bone of the epiphysis and diaphysis fuses

if stressed by excessive muscle activity or body weight

when does appositional growth in adults occur

osteoblasts in the periosteum

secrete bone matrix on the external bone surface

osteoblasts on the external surface of diaphysis

remove the bone

hormones

what controls bone growth in young adulthood

growth hormone

most important hormone in stimulating epiphyseal plate activity in infancy and childhood; released by pituitary gland

thyroid hormones

monitor the activity of growth hormone; ensuring the skeleton has the proper properties as it grows

increased estrogen levels

what induces epiphyseal closure to end long bone growth

bone resorption

the removal of minerals and collagen fibers from bone by osteoclasts; process by which osteoclasts break down the tissue in bones and release the minerals resulting in a transfer of calcium from bone tissue to blood

bone deposition

the addition of minerals and collagen fibers to bone by osteoblasts

parathyroid hormone

A hormone of the parathyroid gland that regulates the metabolism of calcium and phosphorus in the body

Calcitonin

regulates the blood concentration of calcium; produces in parafollicular

bones response to mechanical stress

keeps the bones strong where stressors are acting

Wolff's Law

holds that a bone grows or remodels in response to the demands placed on it