bones chapter 6

What is osteoporosis and how many forms does it present in?

a rare hereditary bone disorder that causes bones to become overly dense and can be presented in three different forms: osteoporosis tarda, congenital, and marble bone.

What is osteopenia?

is the loss of ossification (bone density) where bones get thin and weaker as a part of getting old.

What causes gigantism?

caused by the overproduction of growth hormones before puberty.

What is acromegaly?

characterized by cartilage growth and changes in the soft tissue that lead to enlargement, which mainly occurs in adulthood.

What is osteosarcoma and what is its survival rate?

a type of bone cancer that is the most common malignancy in adolescents, with a survival rate of 60-75%.

What is the mortality rate for Ewings Sarcoma?

has a mortality rate of 50% with treatments such as chemotherapy, radiation, and surgery.

What is an osteoma?

is a noncancerous (benign) bone tumor in children and adolescents that can be removed with laser photocoagulation.

How many bones are there in the human body?

206

What are the two divisions of the skeletal system?

divided into two parts: the axial and appendicular systems.

What is the axial skeleton?

the support system for the body, consisting of the head, neck, back, and chest.

What is the appendicular skeleton?

includes all bones that attach to the axial skeleton.

Define proximal and distal in relation to bone structure.

promixal means closer, while distal means further away.

What are the functions of the skeletal system?

providing support for the attachment of soft tissues, storing minerals, regulating blood serum calcium levels, producing red marrow, and protecting underlying organs.

What are sutural bones?

located between the flat bones of the skull and are shaped like jigsaw puzzle pieces.

Describe irregular bones and give an example.

short and flat with ridged surfaces; examples include the pelvis and several bones in the skull.

What characterizes short bones? Give examples.

box-like in appearance; examples include carpal and tarsal bones.

What are flat bones and provide examples.

characterized by thin parallel surfaces; examples include the skull, parietal bone, sternum, and ribs.

What are long bones?

long and slender; examples include femurs, tibia, and humerus.

What are sesamoid bones?

small, round, and flat bones located in the kneecap, hand, and feet.

depression openings

sites where blood vessels or nerves lie alongside or penetrate the bone,

projection openings in bone structure?

openings form where muscles, tendons, and ligaments attach or where bones form joints.

What is the diaphysis?

the tubular or long shaft of a bone.

What is the epiphysis?

the end of the bone on both sides where bones join with other bones.

What is the metaphysis?

the region where the epiphysis and diaphysis meet.

What is the role of osteocytes?

mature bone cells held in a lacuna; they maintain protein and mineral content of the surrounding matrix and help repair damaged bones.

What is the dense matrix?

compact and tightly packed extracellular matrix contains calcium salts.

What is the function of osteoblasts?

form new bones and grow by healing existing bones through a process called osteogenesis.

What do osteoblasts become when surrounded by bone?

osteocytes.

Define osteoid.

the matrix produced by osteoblasts that has not yet been calcified to form bone.

What is the function of osteoclasts?

break down old or damaged bones to make space for new ones.

What is osteolysis?

the breakdown and loss of bone tissue.

How does PTH affect osteoclast activity?

increases osteoclast activity.

What are osteoprogenitor cells?

stem cells that can differentiate into osteoblasts and originate from mesenchymal stem cells.

What is bone homeostasis?

the balance between osteoblasts (builders) and osteoclasts (breakers) that ensures constant renewal and strength of bone tissue.

What is the basic structural unit of compact bone?

an osteon.

What form does concentric lamellae take in compact bone?

form one at a time during the creation of an osteon.

What are perforating canals?

canals that run opposite directions, and they are perpendicular to the central canal.

What is spongy bone and what is it filled with?

has a mesh-like open matrix called trabeculae, which is avascular; the spaces between trabeculae are filled with red bone marrow that produce red blood cells.

What is the role of weight-bearing bones?

are centrally located in the body and support and distribute the body's weight, such as the femur, tibia, and ulna.

What is the periosteum?

made of an outer fibrous layer and an inner layer; it covers all bones except parts enclosed in joints, supplying blood and aiding in the growth and healing of bones.

What is the function of the endosteum?

a thin, vascular membrane that lines the inner surface of bones, including the medullary cavity and surfaces of spongy bone.

What is endochondral ossification?

the process of bone formation that involves the replacement of hyaline cartilage with bone tissue.

What steps are involved in endochondral ossification?

1) Hyaline chondrocytes enlarge; 2) Distinct features of epiphysis, diaphysis, and metaphysis appear; 3) Blood enters the medullary cavity, forming the primary ossification center; 4) Bone becomes longer and thicker; 5) Blood vessels form in the epiphysis with osteoblasts building up bone, creating the secondary ossification center; 6) Trabeculae appear in the epiphysis surrounded by cartilage.

What is appositional growth?

allows bones to increase in both length and thickness by adding new bone tissue to the outer surface.

What marks the area where bone growth once occurred?

The epiphyseal line marks the area where bone growth once occurred.

What happens to the epiphyseal plate after puberty?

the epiphyseal plate cartilage is gradually replaced by bone, forming the epiphyseal line.

How does osteoblast and osteoclast activity affect bone thickness?

If osteoblast activity is higher, bones become thicker and stronger; if osteoclast activity dominates, bones become thinner or weaker.

osteoblast

activity is higher, bones become thicker and stronger

osteoclast

osteoclast activity dominates, bones become thinner or weaker.

What is calcitriol and its function?

a hormone produced in the kidneys that helps the body absorb calcium and phosphorus from the digestive tract.

Vitamin D

aids in calcium absorption.

Vitamin A

stimulates osteoblast activity,

Vitamin K

helps synthesize bone proteins,

What is the composition of bones?

Bones consist of approximately 67% inorganic components (calcium, phosphate, carbonate, sodium, magnesium, and potassium) and 33% organic components (mostly collagen fibers providing flexibility and resilience).

What happens to muscle cells and neurons if blood calcium levels drop significantly?

If blood calcium levels drop by more than 30%, muscle cells and neurons in the brain become unresponsive; if levels drop by more than 50%, it can lead to death.

What hormones maintain calcium homeostasis?

maintained by calcitonin and parathyroid hormone (PTH).

What is the role of parathyroid hormone (PTH)?

PTH, produced by parathyroid glands, raises blood calcium by stimulating bone breakdown, increasing intestinal absorption, and reducing kidney excretion.

How does calcitonin affect blood calcium levels?

Calcitonin, produced by thyroid gland parafollicular cells, lowers blood calcium by inhibiting bone breakdown and increasing kidney excretion.

What happens during the initial response to a fracture?

Bleeding occurs, producing a clot called a fracture hematoma.

What forms to stabilize a fracture?

Calluses form to stabilize the break, including an external callus (cartilage and bone around the fracture) and an internal callus (develops inside the medullary cavity).

During bone healing, osteoblasts replace the cartilage of the external callus with __________,which is later remodeled into compact bone.

spongy bone

• The internal callus forms between the broken bone ends to __________ the fracture.

stabilize (or bridge)

Over time, spongy bone is remodeled into __________ bone.

Compact

What is osteopenia?

early bone demineralization that starts around ages 30-40, causing a bone loss of about 8% per decade in women and 3% in men, affecting areas such as epiphyses, vertebrae, and jaws.

What are the consequences of osteopenia?

Consequences include fragile limbs, reduced height, and tooth loss.

What is osteoporosis characterized by?

characterized by severe loss of spongy bone, usually later in life due to a reduction in estrogen, impairing normal function.

What is the prevalence of osteoporosis in individuals over age 50?

In individuals over age 50, prevalence is 29% in women and 18% in men.

What is a compression fracture?

fracture occurs when jumping from a height compresses vertebrae.

What is an epiphyseal fracture?

fracture occurs in a child before puberty, and if not fixed, it may prevent proper bone growth.

What are greenstick fractures?

partial fractures where the bone bends and cracks but does not break completely, affecting both older and younger audiences.

What is a Colles fracture?

a fracture of the distal radius near the wrist, commonly occurring in the elderly when they fall on an outstretched arm.

What is a Pott's fracture?

is a fracture of the distal fibula and/or tibia involving the ankle, often associated with soccer injuries.

What percentage of the inorganic component of bone is made up of calcium?

39% of the inorganic component of bone.

What percentage of the inorganic component of bone is made up of phosphate?

17% of the inorganic component of bone.

What percentage of the inorganic component of bone is made up of carbonate?

9.8% of the inorganic component of bone.

What percentage of the inorganic component of bone is made up of sodium?

0.7% of the inorganic component of bone.

What percentage of the inorganic component of bone is made up of magnesium?

0.4% of the inorganic component of bone.

What percentage of the inorganic component of bone is made up of potassium?

0.2% of the inorganic component of bone.