A&P 1 - Chapter 6
osteoclast activation involves
PTH (parathyroid hormone) and immune T cell proteins
compression fracture
bone is crushed
classification of bones
long, short, sesamoid, flat, irregular
thyroid hormone
modulates activity of growth hormone, ensuring proper proportions
osteocyte
monitors and maintains the bone matrix
bone remodeling
ongoing replacement of old bone tissue by new bone tissue
Five main steps in the process of ossification
1. Bone collar forms around diaphysis of cartilage model 2. Central cartilage in diaphysis calcifies, then develops cavities 3. Periosteal bud invades cavities, leading to formation of spongy bone • Bud is made up of blood vessels, nerves, red marrow, osteogenic cells, and osteoclasts 4. Diaphysis elongates, and medullary cavity forms • Secondary ossification centers appear in epiphyses 5. Epiphyses ossify • Hyaline cartilage remains only in epiphyseal plates and articular cartilages
5 zones of the growth plate
1. resting zone 2. proliferation zone 3. hypertonic zone 4. calcification zone 5. ossification zone
How many bones are in the human skeleton
206
at what age are all bones completely ossified
25
what percent of bone mass is recycled each week
5-7%
leptin
A hormone released by white adipose tissue to reduce hunger
Serotonin
Affects mood, hunger, sleep, and arousal
Treating Osteoporosis
Calcium Vitamin D supplements Weight-bearing exercise Hormone replacement therapy
Perforating (Volkmann's) canals
Connect blood vessels and nerves of periosteum, medullary cavity, and central canal
Epiphysis
End of a long bone that consists of compact bone externally and spongy bone internally
Estrogen
Female sex hormone
Canaliculi
Hairlike canals that connect lacunae to each other and the central canal
Repair involves four major stages
Hematoma formation, fibrocartilaginous callus formation, bony callus formation, bone remodeling
inorganic components of bone
Hydroxyapatites (mineral salts)
axial skeleton
Long axis of body: Skull, vertebral column, rib cage
long bones
Longer than they are wide Limb bones
Calcitonin
Lowers blood calcium levels
Testosterone
Male sex hormone
nutrient foramen
Narrow tunnel through the diaphysis that allows blood vessels into the medullary cavity
Control of Remodeling
Occurs continuously but regulated by genetic factors and two control loops
bone deposit
Occurs where bone is injured or added strength is needed
functions of bones: hormone production
Osteocalcin secreted by bones helps to regulate insulin secretion, glucose levels, and metabolism
resorption is function of
Osteoclasts
compact bone consists of
Osteon (Haversian system) Canals and canaliculi Interstitial and circumferential lamellae
functions of bones: protection
Protect brain, spinal cord, and vital organs
hyaline cartilage
Provides support, flexibility, and resilience
Hydroxyapatites (mineral salts)
Responsible for hardness and resistance to compression
functions of bones
Support Protection Movement Mineral and growth factor storage Blood cell formation Triglyceride (fat) storage Hormone production
wolf's law of bone
The shape of a bone reflects the stress it endures
flat bones
These bones are thin, flat, and curved. They form the ribs, breastbone, and skull.
hematoma formation
Torn blood vessels hemorrhage, forming mass of clotted blood called a hematoma
growing bones widen as they lengthen through apposition growth (can occur throughout life) T or F
True
what is the cause of rickets
Vitamin D deficiency
Response to Mechanical Stress
Wolff's law: A bone grows or remodels in response to forces or demands placed upon it
Osteoporosis
a condition in which the bones become fragile and break easily
fibrocartilaginous callus formation
a mass of repair tissue
primary ossification center
a region where bone tissue will replace most of the cartilage
excesses or deficits of any hormones cause
abnormal skeletal growth
osteomalacia
abnormal softening of bones in adults
calcification front
abrupt transition zone between osteoid seam and older mineralized bone
testosterone and estrogen promote
adolescent growth spurts
two ways in which cartilage grows
appositional and interstitial
fractures
are breaks
trabeculae of spongy bone
are like cables on a suspension bridge, they confer strength to bone
when does bone lengthening in females cease?
around 18 years of age
when does bone lengthening in males cease?
around 21 years of age
osteoid seam
band of unmineralized bone matrix that marks area of new matrix
skeletal cartilage contains no
blood vessels or nerves
epiphyseal plate thins, then is replaced by
bone
greenstick fracture
bone breaks incompletely. common in children
comminuted fracture
bone breaks into many fragments
intramembranous ossification
bone develops from a fibrous membrane
displaced fracture
bone ends are out of normal alignment
non-displaced fracture
bone ends retain their normal position
Osteoblasts
bone forming cells
endochondral ossification
bone forms by replacing hyaline cartilage
periosteal cells
bone lining cells on the external bone surface
endosteal cells
bone lining cells on the internal bone surface
what is scattered throughout spongy bone
bone marrow
osteoprogenitor cells
bone stem cells
irregular bones
bones of the vertebrae and face
short bones
bones of the wrist and ankles
appendicular skeleton
bones of upper and lower limbs: girdles attaching limbs to axial skeleton
Depression (bone marking)
bowl or groove like cut out that can serve as passageways for vessels and nerves, or plays a role in joints
closed (simple) fracture
break that does not penetrate the skin
sacrificial bonds
break under stress to dissipate shock and quickly reform
bone resorption
breakdown of bone
complete fracture
broken all the way through
open (compound) fracture
broken bone penetrates through the skin
depressed fracture
broken bone portion is pressed inward
functions of bones: mineral and growth factor storage
calcium and phosphorus, and growth factors reservoir
cartilage is made up of
chondrocytes
Lamellae
contain collagen fibers that run in different directions in adjacent rings
Endosteum
covers inside portion of compact bone
Periosteum
covers outside of compact bone
Bisphosphonates
decrease osteoclast activity and number
gross anatomy of compact bone
dense outer layer on every bone that appears smooth and solid
sustained high blood calcium levels can lead to
deposits of calcium salts in blood vessels or kidneys and formation of kidney stones
Where is yellow marrow found?
diaphysis
some risk factors for osteoporosis
diet poor in calcium and protein, smoking, genetics
what does resorption do?
dig depressions or grooves as they break down matrix
closed reduction
doctor manipulates to correct position
osteoclasts remove bone on
endosteal surface
How often is compact bone replaced?
every 10 years
how often is spongy bone replaced
every 3-4 years
functions of bones: triglyceride (fat) storage
fat used for an energy source is stored in bone cavities
interstitial lamellae
fill spaces between osteons
bone lining cells
flat cells on bone surfaces believed to also help maintain matrix
functions of bones: support
for body and soft organs
levels of bone structure
gross, microscopic, chemical
interstitial growth
growth from within
postnatal bone growth
growth in length of long bones
appositional growth
growth in width
epiphyseal plate
growth plate
epiphyseal fracture
growth plate (epiphyseal plate) separates from shaft of bone (diaphyses)
In adults, red marrow is located
heads of femur and humerus
circumferential lamellae
help long bone to resist twisting
functions of bones: blood cell formation
hematopoiesis occurs within the marrow cavities of bones
hypercalcemia
high levels of calcium cause nonresponsiveness
fibrocartialge
highly compressible, forms cushion-like discs between vertebrae
Opening (bone marking)
hole or canal in bone that serves as passageways for blood vessels and nerves
two control loops of remodeling
hormonal controls and response to mechanical stress
What covers area of bone that is part of a movable joint
hyaline cartilage
what makes up 65% or bone by mass?
hydroxyapatite
when can yellow marrow convert to red marrow?
if the person becomes anemic
Denosumab
improves bone density in elderly
parathyroid hormone
increases blood calcium levels
osteogenic layer
inner layer abutting bone and contains primitive osteogenic stem cells that gives rise to most all bone cells
immobilization
is needed for healing by a cast
compact bone is also called
lamellar bone
functions of bones: movement
levers for muscle action
Hypocalcemia
low levels of calcium cause hyper excitability
skeletal cartilage
made of high resilient, molded cartilage tissue that consists primarily of water
gross anatomy of spongy bone
made up of a honeycomb of small, needle-like or flat pieces of bone called trabeculae
Osteocytes
mature bone cells
growth hormone
most important hormone in stimulating epiphyseal plate activity in infancy and childhood
bones thicken in response to increased stress from
muscle activity or added weight
incomplete fracture
not broken all the way through
capillaries in endosteum supply
nutrients
New bone matrix is deposited by
osteoblasts
bony callus formation
osteoblasts begin to produce spongy bone trabeculae joining portions of the original bone fragments
Types of bone cells
osteocytes, osteoblasts, osteoclasts
Cells of bone tissue
osteogenic cells, osteoblasts, osteocytes, bone lining cells, osteoclasts
organic components of bone
osteogenic cells, osteoblasts, osteocytes, bone-lining cells, osteoclasts, and osteoid
bone disorders
osteomalacia, rickets, osteoporosis
Projection (bone marking)
outward bulge of bone
remodeling units
packets of adjacent osteoblasts and osteoclasts coordinate remodeling process
Fracture Classification
position of bone ends after fracture, completeness of break, whether skin is penetrated
Ossification (osteogenesis)
process of bone tissue formation
Three types of bone markings
projection, depression, opening
spiral fracture
ragged break occurs when excessive twisting forces are applied to a bone
open spaces between trabecular are filled with
red or yellow bone marrow
fracture treatment involves
reduction
osteoblasts
responsible for bone growth
sesamoid bones
round bones found near joints
Central (Haversian) Canal
runs through the core of the osteon that contains blood vessels and nerve fibers
sharpey's fiber
secures periosteum to bone
elastic cartilage
similar to hyaline cartilage but contains elastic fibers
bone markings
sites of muscle, ligament, and tendon attachment on external surfaces
Lacunae
small cavities that contain osteocytes
rickets
softening of bones in children
Where is red marrow found?
spongy bone
where is red marrow found in newborns?
spongy bone and medullary cavities
mesenchymal cells
stem cells that respond to injury or infection
osteon
structural unit of compact bone
trabeculae
supporting bundles of bony fibers in spongy bone
open reduction
surgical pins or wires secure ends
resorption bays (osteoclasts)
the depressions that the cells are located when active
paget's disease
the excessive breakdown of bone tissue, followed by abnormal bone formation
reduction
the realignment of broken bone ends
diaphysis
the shaft of the bone
Hematoma
tumor of blood
Osteoid
unmineralized bone matrix
How do Canaliculi form?
when matrix hardens and cells are trapped
