Bio 241 Chapter 7 Skeletal

compare and contrast between compact and spongy bone

Compact bone tissue forms the outer layer of all bones and contain osteons. makes up about 80% of total bone mass Spongy bone forms the inner layer of all bones. Spongy bone contains trabeculae, which are arranged as rods or plates. Red bone marrow is found between the trabuculae. Makes up about 20% of total bone mass.

how does red marrow differ in adults and infants?

Red bone marrow is found in the spongy bone of most of the bones in children (as well as the medullary cavity of long bones). In adults red marrow is found only in selected portions of the axial skeleton such as flat bones of the skull, vertebrae, ribs sternum and ossa coxae (hip bone). Adults also have red bone marrow in the proximal epiphyses of each humerus and femur.

Define 'tuberosity'

Large rough projection- Projections for tendon and ligament attachment

Define 'trochanter'

Massive, rough projection found only on the femur- Projections for tendon and ligament attachment

define 'foramen'

Rounded passageway through a bone

stress fracture

Thin fractures due to repeated, stressful impact such as running.

rickets

disease of children caused by vitamin D deficiency, characterized by imperfect calcification, softening, and distortion of the bones typically resulting in bow legs.

osteoporosis

disease resulting in loss of bone mass- starts off as osteopenia

what are the three different cartilages in the body and where are they found

elastic cartilage- external ear fibrocartilage- weight bearing cartilage found in intervertebral discs, pubic symphysis knees etc. hyaline cartilage- attaches ribs to sternum (costal cartilage) covers ends of some bones(articular cartilage), epiphyseal plate and provides a model for the formation of most of the bones in the body.

hairline fracture

fine crack in which sections of bone remain aligned (common in skull)

define 'fossa'

flattened or shallow depression

osteogenesis

formation and development of bone connective tissue.

describe the growth of a long bone

growth of a long bone takes place in the epiphyseal plate (interstitial growth) growth in bone length depends on 1) chondrocytes undergo mitotic cell division and chondrocytes are hypertrophy (the cells increase in their size).

what are the factors affecting bone remodeling

hormones and mechanical stresses

what is the effect of mechanical stress on bone?

i.e. weight bearing movement and exercises are mechanical stress. this is required for normal bone remodeling. osteocytes detect the stress and communicates to the osteoblasts they then increase synthesis of osteoid which is then followed by deposition of mineral salts. athletes bones typically become noticeably thicker as a result of repetitive and stressful exercise. these exercises/activities help build and retain bone mass.

what is the epiphyseal line?

in the metaphysis of bones is where the epiphyseal plate occurs, this is where the hyaline cartilage provides continued growth in length. this area is larger in kids, however, in adults this is a thin line called the epiphyseal line, as adults stop growing and the plate (where interstitial growth occurs) is no longer existent.

how does glucocorticoids effect the bones

increase bone loss and in children impair bone growth when there are chronically high levels of glucocorticoids.

how does serotonin effect the bones

inhibits osteoprogenitor cells from differentiating into osteoblasts when there are chronically high levels of serotonin

what are the organic and inorganic components of the bone matrix and what specific roles do they play?

inorganic components include: made up of salt crystals which is calcium phosphate. calcium phosphate and calcium hydroxide interact to form crystals of hydroxyapatite. the crystals also incorporate other salts i.e. calcium carbonate and ions such as sodium, magnesium, sulfate and fluoride during calcification. the crystals harden the matrix and account for the rigidity or relative inflexibility of bone that provide it's strength. Organic components include: Osteoid: is composed of both collagen protein and proteoglycans (including chonroitin sulfate) and glycoproteins which suspends and supports the collagen fibers. these organic components give the bone tensile strength by resisting stretching and twisting and contribute to it's overall flexibility.

which organs are involved in the production of vitamin d

integumentary (gets absorbed by the skin -sunlight) goes to the liver where it vitamin d gets converted to calcidiol by the liver enzymes then passes to the kidney where it's converted to calcitriol- which is the active form of Vitamin D.

what is an osteon

is the basic functional and structural unit of mature compact bone. osteons are oriented parallel to the diaphysis of the long bone.

what are the effect of thyroid and parathyroid hormones on blood calcium levels?

parathyroid hormone is secreted and released by the parathyroid glands in response to reduced blood calcium levels. Calcitonin is released from the thyroid gland in response to high blood calcium levels.

define 'facet'

small flat shallow surface- articulating surface

Define 'tubercle'

small, round projection- projection for tending and ligament attachment

osteomalacia

softening of the bones caused by impaired bone metabolism primarily due to inadequate levels of available phosphate, calcium, and vitamin D,

how does the thyroid hormone effect the bones

stimulates bone growth by stimulating metabolic rate of osteoblasts.

how does the growth hormon effect the bones

stimulates the liver to produce the hormone IGF which causes cartilage proliferation at the epiphyseal plate and resulting bone elongation

What are the functions of the skeletal system

support- provides structural support and serve as a framework for the entire body. Protection- protects internal organs Movement- Bones serve as attachment sites for skeletal muscles. homeopoiesis-is the process of blood cell production. it occurs in red bone marrow CT that contains stem cells that form blood cells and platelets. Storage- stores minerals (calcium and phosphate and is then released by the CT when it's needed) and energy reserves (phosphate is a structural component of ATP.

osteolysis

the pathological destruction or disappearance of bone tissue.

osteoid

unmineralized, organic portion of the bone matrix that forms prior to the maturation of bone tissue.

dwarfism

unusually or abnormally low stature or small size.

describe the role of vitamins a and c in the formation of bones

vitamin c- required for collagen formation Vitamin A-Retinoic acid (which the body makes from vitamin A) stimulates osteoclasts, but suppresses osteoblasts which increases the risk of fractures. Remember these are the bone cells that absorbs bone tissue during growth and healing which are necessary for remodeling, however too much could be detrimental, however too little vitamin A can is also linked to an increased likelihood of a fracture. So we need just the right amount.

define 'fissure'

narrow, slit like opening through a bone.

Define 'ramus'

angular extension of a bone relative to the rest of the structure- Projections for tendon and ligament attachment

Define 'process'

any marked bony prominence- Projections for tendon and ligament attachment

osteoblast

are formed from osteoprogenitor stem cells. Secrete the matrix for bone formation.

complete fracture

bone is broken into two or more pieces

osteoclasts

breaks down bone during growth and healing in an important process called bone resorption.

how do bones respond to mechanical stress?

by increasing bone mass - osteocytes detect the stress and communicates to the osteoblasts they then increase synthesis of osteoid which is then followed by deposition of mineral salts. athletes bones typically become noticeably thicker as a result of repetitive and stressful exercise.

what are the components of bone matrix

cells (osteoprogenitor, osteoblasts, osteocytes, and osteoclasts), ground substance and collagen fibers.

what are the components of an osteon

central canal (haversian) concentric lamellae osteocytes lacunae canaliculi

how do osteocytes communicate?

communicates with its surroundings through tiny channels called canaliculi.

avulsion

complete severing of a body part (typically a toe or finger).

what occurs in the 5 layers of growth area of long bones?

1) zone of resting cartilage: this area is furtherest from the medullary cavity. this region secures the epiphysis to the epiphyseal plate. 2) zone of proliferating cartilage: chondrocytes in this zone undergo rapid mitotic cell division, enlarge slightly. 3) zone of hypertrophic cartilage: here the chondrocytes stop dividing and start to hypertrophy (enlarge in size) the walls of the lacunae become thin because the chondrocytes reasorb matrix as they hypertrophy. 4) zone of calcified cartilage: minerals are deposited in the matrix between the columns of lacunae this calcification destroys the chondrocytes and makes the matrix appear opaque (not transparent) 5) zone of ossification: the walls break down between lacunae in the columns forming longitudinal channels. spaces are invaded by capillaries and osteoprogenitor cells from the medullary cavity. new matrix of the bone is deposited on the remaining calcified cartilage matrix.

which is likely to heal faster, a bone injury or a cartilage injury? why?

A bone injury because bone has more blood vessels and with cartilage you have to rely on diffusion.

what are the structural components of a long bone? Why are the right proportions of these components important?

Diaphysis (aka shaft)- The elongated, usually cylindrical diaphysis provides for the leverage and major weight support of a long bone. The hallow cylindrical space within the diaphysis is the medullary cavity. In children, this cavity contains red bone marrow which is later replaced by yellow bone marrow in adults, and red bone marrow is found in flat bones (aka parts of skull) Epiphysis- is an expanded knobby region at the end of each long bone. An epiphysis is composed of an outer thin layer of compact bone and an inner, more extensive region of spongy bone. Spongy bone within the epiphysis resists stress that is applied from many directions. Metaphysis- is the region in a mature bone between the diaphysis and the epiphysis. This region contains the epiphyseal growth plate. The right proportions of these components are important as each of them have a certain duty/task. The diaphysis I feel is the largest as it's there to bare weight, also in contains the bone marrow where homeopoiesis takes place. The epiphysis is not as large of an area compared to the diaphysis because this basically contains more spongy bone to allow in cushion and articulation. The metaphysis is the smallest of the 3 as it contains the growth plate, as the child grows this area is constantly adding once growing stops it turns into a epiphyseal line.

achondroplasia

a hereditary condition in which the growth of long bones by ossification of cartilage is retarded, resulting in very short limbs and sometimes a face that is small in relation to the (normal-sized) skull.

summarize the process of endochondral ossification

is the development of a bone starting from the hyaline cartilage (which is found in embryo) this process begins in the first month of embryo. the steps are as followed: 1) fetal hyaline cartilage model develops: As cartilage enlarges, chondrocytes near the diaphysis increase in size and surrounding matrix begins to calcify. Deprived of nutrients chondrocytes begin to die. 2) Cartilage calcifies and a periosteal bone collar forms: perichondrium surrounding the cartilage differentiate into osteoblasts. Perichondrium converts to periosteum and the osteogenic layer produces a bony collar around shaft of cartilage. 3)The primary ossification center forms in the diaphysis: capillaries and osteoblasts migrate into the heart of the cartilage, into spaces left by chondrocytes. the calcified matrix breaks down and osteoblasts replace with spongy bone. This becomes Primary Ossification Center in the diaphysis 4)Secondary ossification centers form in the epiphyses: The entire diaphysis is filled with spongy bone but as it enlarges, osteoclasts come to the the central portion to create Medullary Cavity. Growth involves increase in length and diameter (appositional and interstitial growth) 5) Bone replaces almost all cartilage, except the articular cartilage and epiphyseal cartilage: Centers of the epiphyses now begin to calcify. Capillaries and osteoblasts migrate to these area, creating Secondary Ossification Centers. 6) Lengthwise growth continues until the epiphyseal plates ossify and form epiphyseal lines: The epiphyses eventually become filled with spongy bone. A thin cap of cartilage remains exposed to join cavity as Articular Cartilage. At the metaphysis, the epiphyseal plate separates the epiphysis from the diaphysis.

what is the function of red marrow in bones?

it is hemopoietic meaning it makes blood cells.

How are bones classified based on their shape?

long bones- are greater in length than width they have and elongated, cylindrical shaft (diaphysis) short bones- have a length nearly equal to their width. i.e. capals, tarsals, sesamoid bones flat bones- have a flat thin surface that may be slightly curved i.e. roof of skull, scapulae, sternum and ribs. irregular bones- have elaborate sometimes complex shapes which do not fit into any of the preceding categories. vertebrae, many bones in the skull ie ethmoid sphenoid and sutural bones.