Exam 3 anatomy

skeletal system functions

skeletal system functions

support

protection

movement

mineral homeostasis

blood cell production

triglyceride storage

bone tissue structure

contains large amount of extracellular matrix, composed of crystalized mineral salts, collagen fibers and water. mineral salts are deposited in the collagen fiber framework (process called calcification)

classification of bones

long bones, short bones, flat bones, sesamoid bones, irregular bones

long bones

usually weight bearing long

short bones

cube shape, generate range of motion

flat bones

thin flat and protective

sesamoid bones

found in tendons and protect from wear and tear

irregular bones

bones that do not belong to any of the above categories

diaphysis

main shaft of long bone

diploe

space full of spongy bone in a long bone without any cavities

ossification/osteogenesis

bone formation

4 situations for ossification

initial bone formation

growth of bones during childhoodd and adolescence until adulthood

replacement of old worn out bone tissue

repair of fractures or bone breakage throughout the lifespan of the individual

intramenmbraneous ossification

formation of bone tissue from mesenchymal cells

endochondral ossification

formation of bone tissue from hyaline cartilage developed from mesenchymal cells

epiphyses

proximal and distal ends of the bone

articular cartilage

thin layer of hyaline cartilage covering epiphysis where bone makes articulation (joint) with another bone. lacks perichondrium.

nutrient foramina

where blood vessels enter bone

periostenum

connective tissue surrounding the bone surface not covered by articular cartilage (attatched by perforating fibers)

medullary cavity

lies in diaphysis and contains bone marrow and blood vessels

endostenum

lining medullary cavity and contains single layer of bone forming ceells and small amount of connective tissue

osteoblasts

bone building cells formed by division of osteogenic cells

osteocytes

over time osteoblasts become ___. they are mature bone cells that maintain the metabolism of the tissue

osteoclast

break down bone extracellular matrix as part of bone maintainance and repair (resorption)

compact bone tissue

composed of repeating structural units called haversian systems or osteons

osteon

contains a haversian (centeral) canal, containing a network of blood vessels, lymphatics and nerves.

concentric lamellae

circular plates of mineralized extracellular matrix surrounding central canal

lacunae

small spaces between lamellae containing osteocytes

canaliculi

connects lacune and central canal

gap junctions

what osteocytes communicate with

interstital lamellae

fragments of older osteons that have been destroyed through reobsorption during a previous bone development and growth

Volkmann’s (perforating) canals

connect periosteum with compact bone tissue and medullary cavity

inner circumferential lamellae

form the boundary between compact bone tissue and spongy bone tissue

spongy bone

doesn’t contain osteons, found in the interior of a bone protected by compact bone

spicules and trabeculae

tissue takes the form of small columns of lamellae

periosteal arteries

small arteries accompanied by nerves that enter bone through perforating canals (supply periostenum and outside compact bone)

steps of Intramembranous Ossification

Mesenchymal cells cluster together and differentiate into osteogenic cells, which produce osteoblasts.

The osteoblasts form the ossification center, and start to secrete bone extracellular matrix.

Once the osteoblasts are surrounded, they turn into osteocytes, and start the calcification process.

Trabeculae are formed to protect the blood vessels and bone marrow.

The periosteum forms around the bone.

steps of endochondral ossification

Mesenchymal cells cluster together and differentiate into chondroblasts.

The chondroblasts secrete cartilage extracellular matrix to make a cartilage model of the bone, and a perichondrium forms around the model.

The model grows in size, and the cartilage extracellular matrix starts to calcify.

Chondrocytes within the calcified area die off, leaving behind spaces that merge to become lacunae.

The development of the primary ossification center starts the process of converting cartilage into bone.

A nutrient artery penetrates the perichondrium, and stimulates the formation of osteogenic cells.

The osteogenic cells form osteoblasts.

Once osteoblasts are produced, the perichondrium becomes a periosteum for the forming bone.

The osteblasts deposit bone extracellular matrix over calcified cartilage, forming spongy bone tissue.

Osteoclasts start to break down spongy bone tissue in the middle of the bone, forming the medullary cavity.

Secondary ossification centers develop within the bone epiphyses.

Unlike primary ossification centers, no cavity develops.

Formation of articular cartilage and the epiphyseal (or growth) plate completes endochondral ossification.

The growth plate is the site of future bone growth.

bone growth lengthwise

depends on interstitial growth of cartilage in one area of bone and the conversion of cartilage into bone in another area

epiphyseal line

what froms when the epephyseal plate diseappears at the end of adolescence

bone growth in thickness

only through appositional growth occuring from outside of the bone. as osteoblasts increase the thickness of the bone, osteoclasts break down the interior of the bone (allowing the bone to grow in size while minimizing in weight)

bone remodeling

the ongoing replacement of old bone tissue with new bone tissue.

bone resorption

the removal of minerals and collagen fibers from bone tissue by osteoclasts

bone deposition

addition of minerals and collagen fibers to bone tissue by osteoblasts

steps of bone resorption

During bone resorption, osteoclasts attach to a bone tissue section, and form a leak-proof seal.

The osteoclasts then release digestive enzymes and acids into the pocket.

The digestive enzymes dissolve fibers and other organic materials.

The acids dissolve the minerals.

The digested materials are transported through the osteoclasts via transcytosis into the bloodstream.

Osteoblasts then move in to rebuild the bone in the cleared area.

bone metabolism factors

Large quantities of calcium and phosphorous are required for bone growth and remodeling. Magnesium, fluoride, and manganese are required in lesser amounts.

Insulin, insulin like growth factors (IGFs), thyroid hormones, and sex hormones also contribute to bone growth and maintenance.

Various vitamins contribute to bone formation and maintenance

vitamin A

stimulates osteoblast activity

Vitamin C

required for effective collagen synthesis

vitamin D

increases body’s ability to absorb cancium from food in the bloodstream

vitamins B12 and K

required for synthesis of bone proteins

fracture

any break in a bone

open fraccture

fracture where the broken bone end protrudes through the skin

closed fracture

broken bone ends do not break the skin

comminuted fracture

fracture where the bone is crushed into fragments at the site of the break

greenstick fracture

partial fracture where one side of the bone breaks but the other side just bends (only in children and adolescents

impacted fracture

one end of the broken bone is driven forcefully into the interior of the other end

pott fracture

fracture of the distal end of the fibula with serious damage to distal tibial atriculation

colles’ fracture

fracture of distal end of radius where the distal fragment is displased posteriorly

stress fracture

microscopic fractures that form without sign of injury to surrounding tissues

reduction

process of bringing fractured bone ends into alignment

closed reduction

involves manual manipulation

open reduction

involves surgery

fracture hematoma

disruption of blood flow by the fracture causes the formation of a mass of clotted blood

steps to bone repair

—Disruption of blood flow by the fracture causes the formation of a mass of clotted blood called a fracture hematoma.

—Nearby bone cells die due to a lack of blood flow.

—Swelling and inflammation occur from the dead bone cells.

—Phagocytes and osteoclasts start to remove the dead and damaged tissue.

—The process may last for six to eight weeks.

—Fibroblasts from the periosteum migrate to the fracture site and produce collagen fibers.

—Chondroblasts from the periosteum produce fibrocartilage within the fracture site.

—The two cell types cooperate to form a mass of repair tissue called a fibrocartilaginous (soft) callus that bridges the fracture.

The process takes about three weeks.

—Osteoblasts begin to produce spongy bone trabeculae within the fracture.

—The trabeculae join the living and dead portions of the original bone fragments.

—The fibrocartilage is gradually converted into spongy bone tissue, converting the soft callus into a bony (hard) callus.

—This process takes about three to four months.

—Dead portions of the original bone are gradually resorbed by osteoclasts.

—Compact bone tissue replaces spongy bone tissue around the surroundings of the fracture.

—The repair process of bone remodeling may be so thorough at to be virtually undetectable under an x-ray.

—However, a thickened area on the bone surface remains as evidence of a previous fracture.

calcium

stored in bone, plays key roles in nerve and muscle function as well as blood clotting and enzyme function.

Parathyroid hormone

increasing osteoclast resorption rates resulting in omre calcium entering the bloodstream

calcitonin

implicated in inhibiting osteoclast activity and accelerating calcium deposition

demineralization

result of the loss of calcium and other minerals from the bone extracellular matrix

brittleness

results from decreased protein synthesis

osteoporosis

a growing porosity of bones resulting in greatly increased incidences for fractures

rickets and osteomalacia

bone disorders resulting from insufficinet calcification of bone and extracellular matrix

osteoarthritis

The degeneration of articular cartilage so that bones are in direct contact with each other.

osteomyelitis

is an infection of bone tissue, and is usually caused by bacteria such as S. aureus

Osteopenia

disorder of low bone mass, usually caused by bone loss rates higher than bone gain rates

osteosarcoma

cancer within bone tissue primarily affected by osteoblasts

hypercalcemia

too much calcium in blood

hypocalcemia

too little calcium in blood

what leads to loss of bone mass?

decrease of hormone prodduction in old age

rickets and osteomalacia

disorder resulting from insufficient calcification of bone extracellular matrix. rickets are children osteomalacia is adults and both are usually caused by lack of vitamin D

axial skeleton

skull and vertebral column, sternum, and rib bones (responsible for protecting and supporting internal organs

appendicular skeleton

includes pectoral and pelvic girdles and bones of limb (responsible for movement)

articulations

regions that form joints with other bones

extensions and projections

protrude out of the bone

depressions

indents in the bone that don’t penetrate to the other side

passages and cavities

indentations that penetrate to the other side

frontal bone, two parietal bones, occipital bone, two temporal bones, sphenoid bone, and ethmoid bone.

bones of the cranium

condyle

knob that articulates with another bone

facet

smooth flat slightly concave or convex articular surface

head

prominent expanded end of a bone sometimes rounded

crest

narrow ridge

epicondyle

expanded region superior to a condyle

line

slightly raised elongated ridge

process

any bony prominence

protuberance

bony outgrowth or protruding part

spine

sharp slender narrow process

trochanter

2 massive processes unique to the femur

tubercle

small rounded process

tuberosity

rough elevated surface

alveolus

pit of socket (tooth socket)

fossa

shallow, broad, or elongated basin

fovea

small pit