Anatomy & Physiology 150 Chapters 6 & 7

what are the functions of the skeletal system?

• support

• protection

• movement

• storage

• blood cell production

what organ systems help support and move the body?

skeletal, muscular, and nervous

what does the skeletal system store in the bones?

calcium and phosphate

what organ system produces blood cells?

skeletal system

what is ultimately responsible for blood cell production?

red bone marrow

what type of cartilage was the fetal skeleton made up of fully?

hyaline cartilage

chondroblast

form cartilage matrix, immature

chondrocytes

surrounded by matrix, within lacunae, mature

matrix

collagen fibers for strength, proteoglycans for resiliency

perichondrium

double-layered C.T. sheath, covers cartilage except at articulations

arthritis

inflammation of the joints

articular cartilage

covers bones at joints; has no perichondrium growth

appositional

new chondrocytes and new matrix at the periphery and cause growth in width and diameter

interstitial

chondrocytes within the tissue divide and add more matrix between the cells

osteoblast

immature bone cells forming bone through ossification or osteogenesis

ossification

formation of bone tissue

collagen

produced by endoplasmic reticulum and golgi apparatus and released by exocytosis

osteocytes

mature bone cells surrounded by matrix, but can make small amounts of matrix to maintain it

what is each osteocyte surrounded by?

a cavity or pit called a lacuna (plural is lacunae)

osteoclasts

destructive bone cells cause bone resorption, release enzymes that digest the bone matrix to release minerals from bone and are derived from monocytes

stem cells

mesenchyme become chondroblasts or osteoblasts

woven bone

crude type of bone tissue with collagen fibers randomly oriented, first type of bone formed by osteoblasts during ossification

lamellar bone

mature type of bone tissue in sheets called lamellae, fibers are oriented in one direction in each layer, but in different directions in different layers of strength

bone remodeling

osteoclasts remove old bone and osteoblasts add new, woven bone is remodeled into lamellar bone

histological classification (based on tissue type)

• trabecular (spongy or cancellous) bone

• compact bone

structural classification (physical appearance)

• long bone L > W

• short bone L about equal to W

• flat bone W > L

• irregular bone

• sesamoid bone

long bone example

arm, thigh, forearm, femur, leg

short bone example

wrist bones

flat bone example

bones that from cranium: parietal/frontal bones

irregular bone example

sphenoid bone

what is the bone of the second digit? E.C. #1

long bone

sesamoid bone

a small bone that is embedded in a tendon or muscle near a joint (kneecap)

trabeculae

interconnecting rods or plates of bone, like scaffolding. spaces filled with marrow, covered with endosteum. oriented along stress lines

do trabecular bones have osteons?

no because they do not have a central canal

compact bone

• solid, outer layer surrounding each bone; has more matrix and is denser than spongy bone

• blood vessels enter the bone and the lamellae are oriented around the blood vessels

what is the functional unit of a compact bone called?

osteon or haversian system

central (haversian) canal

contains blood vessels and nerve

osteocytes

in a lacuna with canaliculi radiating from the lacuna

canaliculi

“tiny” canals radiating from the lacuna

perforating or volkmann’s canal

perpendicular to long axis and contain blood vessels that run from one central canal to the next

lamellae

calcium and phosphate

concentric lamellae

located within an osteon

circumferential lamellae

located on the peripheral (outer edge)

interstitial lamellae

located in between osteons

where are osteons only found in?

compact bone also known as haversian system

epiphysis of a long bone

• end of the bone; primarily spongy bone covered with compact bone

• within joints, covered with hyaline cartilage called articular cartilage

epiphyseal plate

growth plate. hyaline cartilage; present until growth stops

epiphyseal line

epiphyseal plate is ossified as bone stops growing in length

diaphysis of a long bone

shaft; primarily compact bone surrounding the medullary cavity

medullary cavity

• contains bone marrow, which is made up of fatty tissues

what color is bone marrow in children?

red bone marrow and used for blood cell formation

what color is bone marrow in adults?

the red bone marrow is replaced by yellow in limb bones (except for proximal epiphyses of arm and thigh bones) elsewhere, varying proportions of yellow/red marrow are found

endosteum

lining in the medullary cavity

periosteum

connective tissue membrane covering the outer surface of a bone

perforating fibers (Sharpey’s fibers)

some periosteal fibers penetrate through the periosteum and into the bone. strengthen attachment of tendon to bone

intramembranous ossification

• takes place in embryonic connective tissue membrane

• for example, “soft spots” of the newborn skull closing

endochondral ossification

• takes place in cartilage

• for example, growth of long bone

soft spot of a newborn

fontanelle

primary ossification center of long bone

diaphysis

secondary ossification center of long bone

epiphysis

what happens in both methods of ossification?

• produce woven bone that is then remodeled

• after remodeling, formation cannot be distinguished as one or other

growth in length

occurs at the epiphyseal plate, organized into five zones

what does growth of a long bone involve the formation of new cartilage by?

• interstitial cartilage growth

• appositional growth: on the surface of the cartilage

closure of the epiphyseal plate

epiphyseal plate is ossified becoming the epiphyseal line, between 12 and 25 years of age

articular cartilage

• does not ossify, and persists through life

• epiphysis of long bone

• classified as hyaline cartilage

how does bone grow in width?

• osteoblasts from the periosteum lay down bone under the periosteum which gradually increases the amount the bone surrounding the medullary cavity

• osteoclasts resorb bone surrounding the medullary cavity, which enlarges over time

what can lack of calcium do?

cause bones to be small

where do we get vitamin D from?

vitamin D2 (plant source) and vitamin D3 (animal source)

why is vitamin D important?

necessary for absorption of calcium from intestines and can be ingested or manufactured in the body

rickets

result from lack of vitamin D during childhood

osteomalacia

results from lack of vitamin D during adulthood leading to softening og bones

why is vitamin C important?

necessary for collagen synthesis by osteoblasts

scurvy

results in the deficiency of vitamin C

what does lack of vitamin C cause?

wounds to not heal, teeth to fall out

growth hormone (GH)

from anterior pituitary gland, stimulates interstitial cartilage growth and appositional bone growth

thyroid hormones (T3 and T4)

required for growth of all tissues

estrogen and testosterone

sex reproductive hormones, cause growth at puberty but can also cause closure of the epiphyseal plates and the cessation of growth

gigantism

excessive growth hormone secretion during years (childhood)

acromegaly

excessive growth hormone-liked secretion in adulthood

dwarfism

insufficient growth hormone during growing years (childhood)

what can increased stress do to bones?

increase strength because of bone remodeling, formation of additional bone, and alter trabeculae to align with stress

what does reduced stress result in?

more osteoclast activity as compared to osteoblast activity

mechanism of fracture

traumatic, disease (pathological), at location of an implant

soft-tissue damage

closed versus open (break through skin)

fracture pattern

linear, spiral, avulsion, stress, compression

number of fragments in the fractured bone

incomplete, complete, and communited

age-specific

greenstick and epiphyseal fractures

bone repair

1. hematoma (collection of blood) formation; red blood cells bring respiratory gases (oxygen), white blood cells (fight off infection/immunity), platelets (put wall around infection)

2. callus formation occurs with fibroblasts and chondroblasts

3. callus ossification (physiological) occurs with osteoblasts

4. bone remodeling occurs with osteoclasts

callus formation (woven bone) > ossification > bone remodeling = lamellar bone

hypercalcemia

when blood calcium levels exceed upper limit

hypocalcemia

when blood calcium levels go below lower limit

what inhibits osteoclastic activities?

calcitonin inhibits osteoclastic activities with high blood calcium levels (hypercalcemia)

what stimulates osteoclastic activities?

PTH stimulates osteoclastic activities with low blood calcium levels (hypocalcemia)

osteoporosis

porous bones, a loss of bone matrix and 2.5 times more common in women

when bone mass decreases, how is the bone lost?

spongy bone is lost first, then compact bone

body

main part of bone

head

enlarged end

neck

constriction between head and body

margin or border

edge

angle

natural bend

ramus

branch off body