What are the six main functions of the skeletal system
Support, Protection, Assistance in movement, Mineral homeostasis (storage and release, Blood cell production, Triglyceride storage.
What is the
bone’s shaft or body—the long, cylindrical, main portion of
What are the proximal and distal ends of the bone
What are the regions between the diaphysis and the epiphyses
What is a layer of hyaline cartilage
that allows the diaphysis of the bone to grow in length
When a bone ceases to grow in
length at about ages 18–21, the cartilage in the epiphyseal plate
is replaced by bone; the resulting bony structure is known as the
What is a thin layer of hyaline cartilage
covering the part of the epiphysis where the bone forms an articulation
(joint) with another bone
Function of Articular cartilage?
friction and absorbs shock at freely movable joints.
the external bone surface wherever it is not covered by
What is the periosteum composed of?
outer fibrous layer, inner osteogenic layer
What is a hollow, cylindrical space within the
diaphysis that contains fatty yellow bone marrow in adults.
medullary cavity or marrow cavity
What is a thin
membrane that lines the internal bone surface facing the
medullary cavity. It contains a single layer of cells and a small
amount of connective tissue
calcification is initiated by bone-building cells called
a bone’s hardness depends on the?
inorganic mineral salts
a bone’s flexibility depends on its?
Like reinforcing metal rods in concrete, collagen
fibers and other organic molecules provide?
unspecialized stem cells derived from mesenchyme, the tissue
from which almost all connective tissues are formed
Osteogenic cells are
the only bone cells to
undergo cell division
Osteogenic cells are found along the
inner portion of the?
periosteum, endosteum, and the
canals within bone that contain blood vessels
Osteoblasts synthesize and secrete collagen fibers
and other organic components needed to
build the extracellular
matrix of bone tissue, and they initiate calcification
What are mature bone
cells, are the main cells in bone tissue and maintain its daily
metabolism, such as the exchange of nutrients and wastes with
What are huge cells
derived from the fusion of as many as 50 monocytes (a type of
white blood cell) and are concentrated in the endosteum
plasma membrane is deeply folded into a
Osteoclasts are concentrated where?
powerful lysosomal enzymes and acids that
digest the protein and mineral components of the underlying bone matrix
breakdown of bone extracellular matrix is called?
resorption is part of the
maintenance, and repair of bone
in response to certain
hormones ______________ help regulate blood calcium level
What type of bone tissue contains few spaces and is
the strongest form of bone tissue
Compact bone tissue
Compact bone tissue is found where?
beneath the periosteum
of all bones and makes up the bulk of the diaphyses of long
Compact bone tissue provides
protection and support and
resists the stresses produced by weight and movement.
Blood vessels, lymphatic vessels, and nerves from the
periosteum penetrate compact bone through transverse
Volkmann’s (FOLK-mans) canals.
and nerves of the perforating canals connect with those of the
medullary cavity, periosteum, and central
The components of compact bone tissue are arranged into
repeating structural units called
osteons or haversian systems
what kind of bone tissue does not
spongy bone tissue
Spongy bone consists of lamellae
arranged in an irregular lattice of thin columns called
The macroscopic spaces between the trabeculae help make
bones lighter and sometimes be filled with red bone marrow
Spongy bone tissue makes up most of the
interior bone tissue
of short, flat, and irregularly shaped bones, and most of the
epiphyses of long bones
What is accompanied by nerves
enter the diaphysis through many perforating (Volkmann’s)
canals and supply the periosteum and outer part of the compact
What artery enters the metaphyses of a long bone and, together with the nutrient
artery, supply the red bone marrow and bone tissue of the
What artery enters the
epiphyses of a long bone and supply the red bone marrow and
bone tissue of the epiphyses
The process by which bone forms is called
secrete cartilage extracellular matrix, producing a
The replacement of cartilage by bone is called
around the cartilage model
growth from within is called
The cartilage model also
grows by the addition of more extracellular matrix material
to the periphery of the model by new chondroblasts that develop
from the perichondrium. This growth pattern is called
The epiphyseal (growth) plate (ep-i-FIZ-e--al) is a
hyaline cartilage in the metaphysis of a growing bone
that consists of four zones
growing bones consists of what four zones?
Zone of resting cartilage, Zone of proliferating cartilage, Zone of hypertrophic cartilage, Zone of calcified cartilage
layer is nearest the epiphysis
and consists of small, scattered chondrocytes
Zone of resting cartilage
Slightly larger chondrocytes
in this zone are arranged like stacks of coins
Zone of proliferating cartilage
Zone of proliferating cartilage undergoes what?
interstitial growth as they divide and secrete
consists of large, maturing chondrocytes arranged in columns.
Zone of hypertrophic cartilage
The final zone of the epiphyseal
plate is only a few cells thick and consists mostly of chondrocytes
that are dead because the extracellular matrix around them
Zone of calcified cartilage.
the blood plasma level of Ca2 is very
closely regulated between
9 and 11 mg/100 mL.
Ca2+ exchange is regulated by hormones, the most important
of which is
parathyroid hormone (PTH)
parathyroid hormone (PTH)increases blood ______ level
PTH also acts on the kidneys (effectors) to decrease loss of
Ca2+ in the urine
blood Ca2 rises above normal, parafollicular cells in the thyroid
calcitonin inhibits activity of what?
osteoclasts, speeds blood Ca2 uptake by bone, and accelerates
Ca2 deposition into bones
hormones are responsible for increased
osteoblast activity and
synthesis of bone extracellular matrix and the sudden “growth
spurt” that occurs during the teenage years
what hormone promote changes in the skeleton that are typical of females, such
as widening of the pelvis
Ultimately sex hormones, especially
estrogens in both sexes do what to growth plates?
shut down growth at epiphyseal
(growth) plates, causing elongation of the bones to cease.
During adulthood, sex hormones contribute to what?
by slowing resorption of old bone and promoting deposition
of new bone.
the hormones most important
to bone growth are the insulinlike growth factors (IGFs), which
are produced by the
liver and bone tissue
insulinlike growth factors (IGFs) promote what?
osteoblasts, promote cell division at the epiphyseal
plate and in the periosteum, and enhance synthesis of the proteins
needed to build new bone
IGFs are produced in response
to the secretion of what hormone?
human growth hormone (hGH)
human growth hormone (hGH) is secreted from what?
What hormone that aids in the absorption of calcium
in foods from the gastrointestinal tract into the blood?
stimulates formation of what hormone?
calcitriol (the active form of vitamin D)
What hormone that promotes absorption of calcium from foods in
the gastrointestinal tract into the blood