Specialized tissue forming the bones
osseous tissue
The end of a long bone that is originally separated from the main bone by a layer of cartilage but that later becomes united to the main bone through ossification
epiphysis
the cavity that contains bone marrow in the diaphysis of a long bone; called also medullary canal.
marrow cavity
the entrance for the nutrient artery of a bone
nutrient foramen
The disc of cartilage between the metaphysis and the epiphysis of an immature long bone permitting growth in length
epiphyseal plate
The line of junction of the epiphysis and diaphysis of a long bone where growth in length occurs
epiphyseal line
The thick fibrous membrane covering the entire surface of a bone except its articular cartilage and serving as an attachment for muscles and tendons
periosteum
a thin layer of connective tissue that lines the walls of the bone marrow cavities and haversian canals of compact bone and covers the trabeculae of cancellous bone. It has both osteogenic and hematopoietic potencies and, like the periosteum, takes an act
endosteum
The cartilage covering the articular surfaces of the bones forming a synovial joint
articular cartilage
A central canal and the concentric osseous lamellae encircling it, occurring in compact bone. Also called haversian system
osteon
the nearly parallel layers of bone tissue found in compact bone
lamellae
the cavity, space, or depression in bone tissue.
lacunae
a very small tube or channel, such as the microscopic haversian canaliculi throughout bone tissue
canaliculi
canals in bone through which blood vessels pass
perforating canals
...
trabeculae
The word osteoporosis literally means "porous bones." It occurs when bones lose an excessive amount of their protein and mineral content, particularly calcium. Over time, bone mass, and therefore bone strength, is decreased. As a result, bones become frag
osteoporosis
1.Provide support by acting as a structural framework and a point of attachment for tendons and ligaments
2. Protect the internal organs (brain, chest, etc.)
3. Assist body movements (in conjunction with muscles)
4.Store and release salts of calcium and p
What are the six functions of the skeletal system?
1. Long bones
2. Flat bones
3. Sutural bones
4. Irregular bones
5. Short bones
6. Sesamoid bones
what are the six types of bones by shape?
long and thin
Describe a long bone
long bone
thin with parallel surfaces
describe a flat bone
arms, legs, hands, feet, fingers, and toes
where are long bones found?
Are found in the skull, sternum, ribs, and scapula
(Resembles a sandwich of spongy bone)
Between 2 layers of compact bone
where are flat bones found?
small, irregular bones
describe a sutural bone?
flat bone
found between the flat bones of the skull
where are sutural bones found?
wormian bones
sutural bones are also called ?
sutural bone
complex shaped bones
describe irregular bones?
spinal vertebrae, pelvic bones
What are two examples of irregular bones?
irregular bone
small and thick
describe short bones??
ankle and wrist bones
2 examples of short bones
short bones
small and flat
describe sesamoid bones?
Develop inside tendons near joints of knees, hands, and feet
where are sesamoid bones found?
sesamoid bone
Stem cells which turn into fibroblasts then differentiate into most other types of bone cells
Are located in inner, cellular layer of periosteum, central canal and the endosteum
Assist in fracture repair
osteogenic cells
are mature osteoblasts (maintenance).
osteocytes
are bone building cells: They synthesize and secrete collagen fibers and other organic components.
osteoblasts
are large bone breakdown cells.
osteoclasts
is good at providing protection and support.
It forms the diaphysis of long bones,
and the external layer of all bones
compact bone
is lightweight and provides tissue support .
It forms much of the epiphysis and the internal cavity of long bones
spongy bone
compact bone
spongy bone
is a highly vascularized C.T. with a hard, mineralized extracellular matrix. It is found in the body in two different arrangements:
bone
is a tough sheath of dense, irregular connective tissue on the outside of the bone.
periosteum
fat storage
yellow marrow
hematopoiesis
red marrow
Bone is 25% water, 25% organic proteins, 50% mineral salts (hydroxyapatite crystals).
bone is made up of
Collagen fibers provide flexibility and tensile strength.
what are the organic constituents of bones and their function?
Calcium Phosphate (Ca3PO4)2
Calcium Carbonate (CaCO3 - marble)
Other trace elements: magnesium, fluoride, sulfate
what are the Inorganic hydroxyapatite crystals (mineral salts) that composes bone?
the shaft or body of a long bone.
diaphysis
form the distal and proximal ends of a long bone.
epiphyses
are the areas where the epiphyses and diaphysis join.
metaphysis
The growth plate is always actively dividing and causing the bone to elongate from each end.
how does mature bone continues to grow and remodel itself?
...
osteogenesis is the process of forming new bone.
ossification
1. Formation of bone in an embryo
2. Growth of bones until adulthood
3. Remodeling of bone
4. Repair of fractures
bone formation occurs in 4 ways
Bone remodeling is the action of reshaping and resizing bone tissue to adapt to changing physical requirements. Bone growth occurs from infancy until the mid-20's. However, bone remodeling never ceases and persists throughout an individual's lifespan.
What is bone remodeling, and why does it occur?
Postpartum, bones develop in thickness through appositional buildup at the periosteum. In contrast, interstitial growth allows for the lengthwise
development of long bones at the epiphyseal plates located at the end of the bones (epiphysis.)
Contrast the effects of appositional and interstitial growth. Which occurs at the periosteum?
It is through the action of osteoclasts, as well as appositional growth that the bone dimensions are proportionally maintained while it is remodeled.
How does bone shaft thickness and width remain proportional during bone remodeling?
Osteoclast activity
This is the other factor that controls the bone's symmetry (ie. thickness and articulations) while it is reshaped.
How does bone shaft thickness and width remain proportional during bone remodeling?
Appositional growth (periosteum and endosteum)
Only the bones located in the appendages experience interstitial lengthening
All bones undergo widening, but only some undergo interstitial lengthening. Which bones undergo interstitial lengthening?
This specifically transpires at the epiphyseal plates.
Where does bone lengthening occur?
1. Zone of Resting Cartilage
2. Zone of Proliferating Cartilage
3. Zone of Hypertrophic Cartilage
4. Zone of Calcified Cartilage
What are the four zones of epiphyseal plate?
Zone of Hypertrophic Cartilage
this is site where chondrocytes build up and enlarge, which in turn expands the lacunae. Its overall effect adds to the lengthening of the shaft.
what is the function of the
zone of hypertonic cartilage
?
Zone of Calcified Cartilage
this is a thin area (a few cells thick) containing expiring and deceased chondrocytes. This layer grounds the epiphyseal plate to the diaphysis
what is the function of the
zone of calcified cartilage
?
Zone of Resting Cartilage
this is a region of hyaline cartilage made of dormant chondrocytes. This region secures the plate to the epiphysis.
what is the function of the
zone of resting cartilage
?
Zone of Proliferating Cartilage
this is the mitotic layer of chondrocytes that drives the resting layer outward. This action results in elongation the diaphysis.
what is the function of the
zone of proliferating cartilage
?
Osteoclasts act to decompose the calcified cartilage. Osteoblasts, in turn, replace the calcified cartilage with bone extracellular matrix
what is the role of
osteoclasts
and
osteoblasts
?
This happens when an individual reaches their adult stature. Once bone growth ceases, the epiphyseal plate's cartilage is replace by bone and the epiphyseal line is left as a reminant of the epiphyseal plate.
what forms the epiphyseal line?
This membrane found to cover the surface of bone. It is composed of connective tissue, osteogenic cells, and osteoblasts. It is critical for bone growth, repair, & nourishment. It is also offers an attachment site for tendons and ligaments.
what is the role of the periosteum?
These progenitor cells give rise to osteoblasts that participates in bone formation.
Describe the role of the following with regard to bone widening.
Osteogenic cells
These cells produce bony matrix that is composed of organic compounds & inorganic salts.
Describe the role of the following with regard to bone widening.
Osteoblasts
This is the bony area produced by osteoblasts that is found around a periosteal blood vessel.
Describe the role of the following with regard to bone widening.
groove formation
The ridges of the groove formation merge forming this central canal structure. This encompasses the periosteal blood vessel.
Describe the role of the following with regard to bone widening.
central canal
This is the lining that develops around the blood vessel within the central canal. It also contains osteogenic cells.
Describe the role of the following with regard to bone widening.
endosteum
Osteoblasts continue to add bony matrix that form these circular structures called lamellae.
Describe the role of the following with regard to bone widening.
lamallae formation
This is accomplished as osteoblasts continue creating lamellae inwardly to the periosteal blood vessel which lead to the creation of a new structural unit of bone.
Describe the role of the following with regard to bone widening.
new osteon formation
While the bone boundary expands outward on the periphery at the periosteum, osteoclasts found on the endosteum break down the inner surface of bone. This leads to a bone with a larger breadth & bigger medullary cavity
Describe the role of osteoclasts along the inner surface of bone at the endosteum?
It is dynamic because it cycles through, being reduced to its primary components to be reabsorbed into the body and then built up again from these components. This homeostatic process is regulated by the body's requirements at any given moment.
why is bone tissue called dynamic?
Bone remodeling starts by having its bone cells (osteoclasts) resorb its own tissue thereby releasing calcium & other minerals for use throughout the body. When restoring bone tissue, bone cells form new bone, taking minerals from the bloodstream and stor
Describe the process and timing of bone remodeling
Remodeling of bone tissue is dependent upon the demands placed upon it. If an individual leads a sedentary and relaxed lifestyle, bone tissue is reduced and excessive bone matrix is resorbed into the body. In contrast, if an individual leads a physically
How does remodeling change bone structure in response to slight and heavy stress?
Bone matrix is connective tissue that is both dense and resilient. Embedded collagen fibers provide for its resilience while calcium phosphate is responsible for the density and firmness in bone.
Describe the composition of bone matrix. Include the importance of collagen fibers and inorganic mineral salts such a calcium phosphate (also known as hydroxyapatite).
The combination of both these fibers with the minerals salts furnishes bone its capacity to withstand pressure along its long axis.
Bone composition gives it great tensile strength. What does this mean?
Osteoclasts break down the bony matrix, and release phosphate and calcium into the blood when they are their blood concentrations are low. Conversely, osteocytes are stimulated to remove calcium and phosphate from the blood when their concentrations are h
Explain how bone tissue matrix serves as a storage site for calcium and phosphate ions.
all of them
What bones contain spongy and compact bone tissue?
external portions of all bones and the majority (diaphysis) of the shafts of all long bones. (external to spongy bone).
where is compact bone located ?
The structural unit of spongy bone. Its appearance gives spongy bone its name because its arrangement is that of an irregular lattice of thin columns.
Define trabeculae?
spongy bone lamellae consists of trabeculae. These units are aligned in a delicate, lacy framework providing space for red bone marrow.
Lamellar arrangement
red marrow
What fills the spaces between the trabeculae
Spongy bone tissue is found in short, flat, and irregularly shape bones. It also forms most of the ends of long bones (epiphysis.) It is also found in a narrow border around the medullary cavity of the diaphysis of long bones.
Where is spongy bone located and what is its function?
In order to adjust to changing demands, bone is continuously remodeled. This involves deposition of new bone and removal of old bone.
Why must bone continuously be broken down?
In response to calcium needs in the body and regulating hormones, bone tissue is either deposited or reabsorbed. Bone deposition lowers blood calcium levels whereas bone reasorbtion raises blood calcium levels.
Describe the two needs that regulate bone remodeling
blood calcium levels
Bone is remodeled to accommodate physical stress. Increased stress results in bone deposition. Conversely, reduced stress results in bone resorption. This conforms to Wolff's law.
Describe the two needs that regulate bone remodeling
physical stresses
1. normal functions of muscles and neurons
2. it increases the overall density of bone tissue
why is calcium needed?
The normal level for calcium is between 9 and 11 mg/1 dL
what is the normal blood calcium level?
Hypercalcemia is an elevated blood calcium level that reduces nervous excitability and can lead to weakness and depression of the nervous system.
what is hypercalcemia? W
Hypocalcemia is a depressed level of calcium that can increase nervous irritability, produces muscle cramps, tetany and even convulsions.
what is hypocalcemia?
The demand placed on calcium usage by the cells of the body
What causes blood calcium levels to naturally decline?
Parathyroid hormone is released when blood calcium level drops. This hormone increases the number and activity of osteoclasts. These cells is involved in bone resorption and raises blood calcium levels.
Describe the effect of parathyroid hormone (PTH) on osteoclasts, bone resorption, and ultimately on blood calcium levels.
PTH promotes calcium reabsorption in the kidney tubules and raises blood calcium levels.
Describe the effect of PTH in the kidneys and ultimately how this affects blood calcium levels.
High blood levels of calcium cause the release of CT from the thyroid gland. CT stimulates osteoblast and osteocytic activity which promotes bone deposition and decreases blood calcium levels
When blood calcium levels are high, the thyroid gland secretes the hormone Calcitonin (CT). Describe the effect of CT on osteoblasts and ultimately on bone matrix structure.
These are involved in the synthesis of collagen.
Describe the bone growth regulatory role of these vitamins
C,K and B12
Stimulates osteoblast formation.
Describe the bone growth regulatory role of these vitamins
vitamin A
Forms calcitrol a hormone that increases calcium concentration in the blood.
Describe the bone growth regulatory role of these vitamins
vitamin D
Promote cell division and enhance protein synthesis.
Describe the bone growth regulatory role of these hormones.
Insulin-like Growth Factors (IGFs)
stimulates IGF production
Describe the bone growth regulatory role of these hormones.
Human growth hormone (gh)
promote normal bone growth
Describe the bone growth regulatory role of these hormones.
Estrogen, Testosterone, Thyroid Hormones, and Insulin
anterior pituitary - stimulates the production of IGF from the liver.
Describe the regulatory role of these hormones, and what gland secretes each.
Human Growth Hormone (GH)
Liver - initiate formation of cartilage matrix and protein synthesis during bone growth.
Describe the regulatory role of these hormones, and what gland secretes each.
Insulin-like Growth Factors (IGFs)
An increase in GH increases blood glucose levels which in turn stimulate the release of somatostatin.
How does GH affect blood glucose levels?
Inhibits secretion of growth hormone and slows IGF release.
Describe the regulatory role of these hormones, and what gland secretes each.
somatostatin(GHIH)
Increases in GH >> increases IGF >> increases blood glucose levels >> increases somatostatin >> decreases GH (repeat)
give an example of how homeostasis is maintained in response to increases in GH.
Sex hormones stimulate osteoblastic activity during puberty which leads to increased ossification and the eventual sealing of the epiphyseal plate. Once the plate seals, longitudinal bone growth ends and the epiphyseal line is left as a remnant of the epi
Describe the affect of sex hormones, initiated during puberty, on osteoblasts and the epiphyseal plate.
Hyaline cartilage is found as the articular cartilage within a synovial joint. It allows flexibility and support. It lessens friction by providing a smooth surface and soaks up vibrations. It is also found in the epiphyseal plate between the end of the bo
Describe hyaline cartilage location and function.
Spongy (cancellous) bone makes up short, flat, and irregularly shaped bones. It also forms the ends (epiphysis) of long bones. Its structural units are called trabeculae "little beams" and within the spaces of these irregular frameworks of columns are fou
Describe spongy (cancellous) bone tissue location and function.
Dense regular CT referred to as white fibrous tissue provides resistance against forces in one direction. This makes up critically important tendons (connects muscle to bone) and ligaments (connects bones to bones).
Describe the function of dense regular CT relative to bones.
Is the process by which bone forms within an individual. An embryo has the beginnings of its skeleton in regions made up of loose mesenchymal cells that provide the guide for future bone formation. Ossification is the process that replaces these progenito
Define ossification
Intramembranous ossification occurs at the flat bones of the skull and mandible.
Where does intramembranous ossification occur?
at the centers of ossification, mesenchymal cells receive specific chemical commands to group together and differentiate into the next type of cells.
Explain how ossification centers form during intramembranous ossification. Include each of the following:
Mesenchymal cells
mesenchymal cells transform into osteogenic cells which are destined to give rise to bone cells..
Explain how ossification centers form during intramembranous ossification. Include each of the following:
osteogenic cells
osteogenic cells further differentiate into these bone-building cells that synthesize and secrete collagen fibers and other organic compounds to form extracellular matrix.
Explain how ossification centers form during intramembranous ossification. Include each of the following:
osteoblasts
this is the uncalcified material secreted by the osteoblasts.
Explain how ossification centers form during intramembranous ossification. Include each of the following:
osteoid (bone matrix)
Spongy bone grows as the bone matrix develops into thin columns of bone (trabeculae) that interconnect to form a lacy network of bone with intervening spaces.
How do trabeculae form which leads to spongy bone formation?
Blood & lymphatic vessels growing into the surfaces of the newly formed trabeculae of the spongy layer provide the basis for red bone marrow. Red bone marrow is a highly vascularized connective tissue
How does red bone marrow develop?
This is a layer of connective tissue that forms on the outer surface of the bone.
Where does the periosteum form?
Compact bone usually replaces the outer layer of spongy bone. The center remains spongy bone.
Where does compact bone frequently replace spongy bone and where does spongy bone remain?
Sutures are immovable joints in the skull made of fibrous tissue found in adults.
Define sutures ?
Fontanels are spaces in the infant skull filled with dense connective tissue commonly called soft spots.
Define fontanels.
These allow the infant's head to pass through the birth canal and allow for brain growth as the infant matures.
What is the function of fontanels and sutures?
Embryonic connective tissue cells aggregate into clusters and differentiate into chondroblasts.
Describe the formation of the cartilage model. Include each of the following:
mesenchymal cells
cells that secrete cartilage matrix to form the cartilage model.
Describe the formation of the cartilage model. Include each of the following:
chondroblasts
Interstitial growth of cartilage is growth from within the tissue and results in increases in length. Appositional growth adds bone tissue from the surfaces and results in increases in width and thickness.
Contrast interstitial and appositional growth of the cartilage model.
this occurs during the development of the ossification center of endochondral ossification when an arterial vessel penetrates the bone from the perichondrium, thereby increasing the availability of nutrients to the surrounding cells.
Describe events during cartilage model formation. Include each of the following:
nutrient artery penetration
Nutrient artery penetration stimulates nearby osteogenic cells to
differentiate into osteoblasts.
Describe events during cartilage model formation. Include each of the following:
osteogenic cells and osteoblasts
Perichondrium is the connective tissue on the surface of cartilage while periosteum is the connective tissue on the surface of bone
Describe events during cartilage model formation. Include each of the following:
contrast the perichondrium and the periosteum
1. Chondroblasts within the perichondrium secrete cartilage matrix causing growth of the cartilage model within the fetus.
2. Two types of cartilage growth happen. Interstitial growth reinforces the cartilage model to develop lengthwise while appositional
Describe (step 2) growth of the cartilage model.
1. A nutrient arterial vessels inserts into the perichondrium and provide an increase of nutrients to the surrounding cells.
2. This increase of nourishment stimulates the osteogenic cells to mature into osteoblasts.
3. Osteoblasts secrete bone matrix und
Describe (step 3) bone collar and periosteum formation.
1. Nutrient deprival
This happens when the bone collar prevents diffusion of nutrients to the interior cartilage area.
2. Osteoblast carrying capillaries
As the cartilage in the interior area disintegrate due to a lack of nutrients, capillaries penetrate
Describe (step 4) primary ossification center formation.
Medullary cavity formation :
As cartilage breaks down in the interior, spaces form and merge into a single central cavity. .
Capillaries and red bone marrow:
the medullary cavity becomes filled with nutrient-carrying capillaries and red bone marrow connec
Describe events of (step 5) remodeling. Include each of the following:
Medullary cavity formation
capillaries and red bone marrow
diaphysis formation