Lecture 3 Bone Flashcards
What is another name for bone tissue?
osseous tissue
What type of connective tissue has cells, vessels, nerves, and a matrix hardened by minerals (mostly calcium phosphate)?
bone tissue
What are the units of the skeletal system?
bones
What makes up individual bones?
bone tissue, marrow, periosteum, endosteum, and cartilage
What are the functions of the skeletal system? Hint: (S.P.M.B.H. - Sarah Pulls Mary Behind Her)
support, protection of other tissues, movement, blood formation, homeostasis of calcium, phosphate, and pH
What type of bones provide leverage for movement?
long bones
What type of bones can move in several directions?
short bone
What type of bones protect soft organs and/or provide a broad surface for attachment of powerful muscles?
flat bones
What type of bones can serve multiple, complex functions?
irregular bones
What is the name of the tightly adhered, vascular membrane that cover bones (except at articular surfaces)?
periosteum
What is the name of the enlarged end of a long bone and is covered with articular hyaline cartilage?
epiphysis
What is the outer layer of bone called?
compact bone
What are long bones filled with?
spongy bone and marrow
What is the membrane lining the marrow cavity and all internal passages called?
endosteum
What is also known as the shaft of the bone?
diaphysis
What is the cylinder of compact bone containing the marrow cavity (medullary cavity) called?
diaphysis
What is the diaphysis covered with?
periosteum
What is another name for the meduallary cavity?
marrow cavity
What cavity contains hematopoeitic bone marrow tissue in young individuals that is progressively replaced by adipose with age?
medullary (marrow) cavity
What is the medullary (marrow) cavity lined with?
endosteum
What are the spongy bone covered with a layer of compact bone and hyaline cartilage called? They are also the enlarged ends of the bone
epiphyses
What is the purpose of enlarged ends of long bones?
to strengthen joints and provide attachments for tendons and ligaments
What is covered with articular cartilage of smooth, low friction hyaline cartilage that is lubricated with synovial fluid?
joint surface
What is the layer of vascular, innervated, dense irregular connective tissue attached to the outer non-articular surfaces of bone called?
periosteum
What is the name of the layer that is continuous with periosteum that is the internal membranes of bone?
endosteum
What surrounds nutrient arteries and lines the medullary cavity?
endosteum
What are the type I collagen fibers that connect the periosteum to the bone matrix?
Sharpey’s fibers
T/F
Spongy bone has no fiber direction.
False.
Pattern is present and fiber direction adds structural integrity to the bone.
What is the basic structural unit of bone?
Osteon (aka Haversian system)
What lines the Haversian Canal?
Endosteum
What structures connect osteocytes?
Pseudopods (within canaliculi)
What’s another name for Perforating Canals?
Volkman’s canals
Are circumferential lamellae part of an osteon?
No.
They ring the outside of a bone (diaphysis)
What structure branches of compact bone to form spongy bone?
Trabeculae
What connects periosteum to compact bone?
Sharpey’s fibers
Inner circumferential lamellae are found between _____ and ______ .
Spongy bone
Osteons
What is the functional unit of the bone?
Osteon (Haversian System)
Would you ever see an osteocyte in a ground bone preparation?
No.
Lacunae only.
What is the name of the blood vessels that penetrate into bones called?
nutrient arteries
What is the name of the blood vessels that carry blood and fluid out of the bone?
periosteal veins and lymphatics
What are the remnants of old osteons that fill the spaces between new osteons?
Interstitial lamellae
What are the external and internal surfaces of flat bone composed of?
compact bone
What is the middle layer of spongy bone called?
diploe
Which layer of spongy bone can absorb some of the force of a skull fracture providing some additional protection to the underlying brain?
diploe
What layer covers the outer surface under the scalp?
periosteum
What are two other names for spongy bone?
Trabecular
Cancellous
What type of cells are in the endosteum and periosteum membranes?
osteogenic cells
What type of cells arise form embryonic mesenchymal cells and become the only source of new osteoblasts?
osteogenic cells
What type of cells multiply continuously and differentiate into osteoblasts in response to growth, stress, or healing of fractures?
osteogenic cells
What type of cells produce an extracellular matrix of collagen (mostly type I) and minerals (mostly calcium phosphate)?
osteoblasts
What type of cells are fully differentiate osteoblasts that are completely surrounded by the matrix they produced?
osteocytes
What are small, thin, isolated, pieces of bone, as in the development of bone or as in a fragment of bone?
spicules
What completely surrounds the osteocytes?
bone matrix
What are the pits in the matrix occupied by the cells?
lacunae
What is the function of osteoclasts?
Resorb and remodel bone.
What are the different types of pseudopods?
filopodia, cytoplasmic extensions, dendritic processes
What are the tiny canals in the bone matrix that contain the filopods?
canaliculi
What type of cells are arranged in rings in the bone matrix around a central canal that contains blood vessels and nerves?
osteocytes
What type of junction interconnects the tips of pseudopods of adjacent osteocytes?
gap junctions
What type of cells use the gap junctions to communicate and to nourish each other?
osteocytes
Endochondral ossification replaces what connective tissue?
Hyaline cartilage
What does organic matter of bone matrix consist of?
type I collagen, proteoglycans, noncollagenous proteins
What are proteoglycans rich in?
chondroitin sulfate, keratin sulfate, and hyaluronic acid
What are the different types of noncollagenous proteins?
osteocalcin, osteopontin, and bone sialoprotein
T/F
Only matrix can be seen in a ground section.
True
What is the difference between an osteocyte and a lacunae?
Osteocytes are cells
Lacunae is the matrix surrounding osteocytes.
What are the remnants of old osteons that fill the spaces between new osteons?
Interstitial lamellae
Which noncollagenous protein has a high bonding affinity for hydroxyapatite and is required for bone mineralization?
osteocalcin
What regulates the expression of osteocalcin?
Vitamin D3
Which noncollagenous protein regulates the formation and remodeling of mineralized tissues and mediates the formation of the osteoclast sealing zone?
osteopontin
Which noncollagenous protein mediates binding of osteoblasts to the extracellular matrix through integrins?
bone sialoprotein
What does inorganic matter of bone matrix consist of?
85% hydroxyapatite, 10% calcium carbonate, 5% other minerals
What are the crystals that are distributed along collagen fibers and organized by osteocalcin?
hydroxyapatite
What two materials make bones both strong and resilient?
minerals and collagen
Which material of bone resist compression?
minerals
Which material of bone adds resilience?
collagen
Which type of bone does not have any hollow spaces in the bone matrix?
compact bone
What type of bone forms the thick-walled tube of the shaft (or diaphysis) of long bones, which surrounds the marrow cavity (medullary cavity)?
compact bone
What are the other names for spongy bone?
cancellous bone and trabecular bone
What type of bone consists of a delicate network of trabeculae which branch and intersect to form a sponge-like tissue?
spongy bone
What type of bone are the ends of long bones filled with?
spongy bone
What can be seen in a decalcified slide of compact bone?
Osteocytes, connective tissue, and vasculature.
In compact bone, what canals house neurovascular bundles?
Volkman’s Canals and
Haversian Canals
What encases osteocyte filopods?
Canaliculi
T/F
The newest matrix in bone is found furthest from the Haversian Canal.
False.
New growth is found in the middle.
What are two other names for spongy bone?
Trabecular
Cancellous
Name the zones of cartilage endochondral ossification from diaphysis to epiphysis.
bone deposition, calcification, hypertrophy, proliferation, reserve cartilage
In metaphysis, what is the zone where macrophages remove dead chondrocytes and calcified cartilage matrix creating voids that are filled with growing blood vessels surrounded by connective tissue that contains fibroblast-like cells that differentiate into osteoblasts.
zone of bone deposition
In metaphysis, what is the zone of resting hyaline cartilage called?
zone of reserve cartilage
In metaphysis, what is the zone of that has a layer of chondrocytes that multiply forming columns of flattened lacunae?
zone of cell proliferation
In metaphysis, what is the zone that has a region of swollen chondrocytes?
zone of hypertrophy
In metaphysis, what is the zone where the cartilage matrix calcifies and the chondrocytes die?
zone of calcification
In metaphysis, what is the zone where macrophages remove dead chondrocytes and calcified cartilage matrix creating voids that are filled with growing blood vessels surrounded by connective tissue that contains fibroblast-like cells that differentiate into osteoblasts.
zone of bone deposition
What fills spaces between trabecular in spongy bone?
Marrow and adipose tissue
Name 3 types of bone marrow.
Red, Yellow, gelatinous
Which bone marrow is hematopoietic?
Red
Why are many elderly people anemic?
The replacement of hematopoietic tissues (red marrow) with yellow and gelatinous marrows.
What do megakaryocytes produce?
Where are they found?
platelets
Red Marrow
What are the two types of ossification processes?
Intramembranous
Endochondral
What respective tissues are replaced in Intramembranous and Endochondral ossification?
Intramembranous replaces Embryonic CT
Endochondral replaces Hyaline Cartilage
What bones go through Intramembranous ossification?
Mostly flat bones
skull, clavicle, mandible body
What is the function of osteoclasts?
Resorb and remodel bone.
What is the first step in intramembranous ossification?
Condensation of mesenchyme
What does matrix replace?
Osteoid
When does an osteoblast become an osteocyte?
When it is surrounded by matrix.
Osteoclasts are syncicia of ________.
macrophages
(and multinucleated)
The soft regions of irregular CT present in the skull at birth are called…
Fontanels
Endochondral ossification replaces what connective tissue?
Hyaline cartilage
What initiates endochondral ossification?
vasculature invades and stimulates chondrocytes in hyaline cartilage
How is the primary marrow space formed in endochondral ossification?
chondrocytes lay down matrix (suffocating themselves) and it is removed by macrophage.
(space then filled with osteoblasts)
What seeds osteoblasts in endochondral ossification?
fibroblasts connected to invading membranes
In a longbone, where are the primary and secondary ossification centers?
Primary - diaphysis
Secondary - epiphysis
When does secondary ossification centers begin to form in the epiphyses of long bones?
near the time of birth
T/F Bone development proceeds all the way to the end of the bone.
False; Hyaline cartilage remains over the epiphysis as the articular cartilage of the joint surface
What is the transitional zone that is at the junction of the diaphysis and epiphysis and forms an epiphyseal plate?
metaphysis
What is the cartilaginous tissue between the primary and secondary ossification centers?
metaphysis
What is the cartilaginous tissue that remains between the medullary cavity (marrow cavity) and the spongy bone in the epiphyses until bone growth ends?
epiphyseal plate
T/F Bones grow and remodel throughout life.
True
What type of growth increases the length of bones at the epiphyseal plate?
interstitial growth
What type of growth increases the width of bones produced by new osteons?
appositional growth
Why do girls grow faster?
Estrogen
Growth hormone causes…
Bone elongation
thyroid hormone increases metabolic rate of…
Osteoblasts
Name two functions of Calcitonin
Deposits Calcium into bone
Inhibits Osteoclasts
What stimulates osteoclast growth and increases blood Ca+ levels?
PTH
Glucocorticoids are increased by…
Stress
cause bone loss / impair growth
What gland secretes GH (growth hormone)
Anterior Pituitary
Why are multiple samples necessary to determine GH levels?
Pulsatile Secretion
Thickening of hand, foot, jaw, and brow bones throughout life is called…
Acromegaly (hormone disorder)
How many types of dwarfism are there?
Over 200
What type of dwarfism is characterized by normal sized head and short longbones?
Achondroplastic dwarfism
What is pituitary dwarfism characterized by?
Normal proportions
What is primordial dwarfism?
growth proportional but severely delayed
What are the four types of bone cells?
osteoprogenitor, osteoblasts, osteocytes, and osteoclasts
What cell secretes osteocalcin and what does it do?
Osteoblasts
Directs hydroxyapatite and forms mineralized matrix
What binds osteoblast to the matrix through itegrins?
Sialoprotein
What are the two main components of bone and how do osteoclasts break them down?
Matrix - HCl
Collagan fibrils - Acid Phosphatase (released by lysosomes)
________ are stimulated by increased pressure and ________ are stimulated by decreased pressure.
OsteoClasts
OsteoBlasts
What seals the Osteoclast plasma membrane to the mineralized surface of the bone?
The “ruffled border”
What is the eroded cavity created by osteoclasts called?
Howship’s lacuna
also called “resorption bays”
Why is the osteoclast considered a “polarized” cell?
The ruffled end is much different than the smooth end.
What is an important component of the sealing zone in an osteoclast?
Osteopontin - binds to an integrin
What is the pH of the acidic environment eroding matrix at the ruffled end of an Osteoclast?
4.5
What follows the cutting zone of osteoclasts in compact bone remodeling?
Blood vessel medially and osteoprogenitor cells cortically
Osteoblasts fill in the space behind the osteoclast cutting zone with what material?
Osteoid (organic bone matrix)
What happens to the organic components of matrix after degradation by osteoclaststs?
Packaged into endocytotic vesicles and either used by the osteoclast or exocytosed.
What induction surface molecule on osteoblasts bind to preosteoclast to initiate differentiation into osteoclast.
RANKL
What receptor binds RANKL on preosteoclasts?
RANK
What is a ligand?
a binding protein
Does PTH stimulate OsteoBlasts?
this is a stupid trick question.
Yes, it stimulates osteoblasts to release M-CSF ligand, which binds macrophage, which ends up producing osteoclast, which resorbs bone.
How does the drug denosumab work?
Interrupts communication between RANK and RANKL
What is paradoxical about giving some patients low and intermittent doses of PTH?
It can INCREASE osteoblast activity in some patients
mechanism unknown - 2nd messenger system apparently complex
What can low calcium levels (hypocalcemia) lead to?
muscle excitability, spasms, tremors, tetany
this increases membrane excitability
What can high calcium levels (hypercalcemia) lead to?
Depresses nervous system activity
this decreases membrane excitability
What is Calcitriol?
Activated Vitamin D
What is the pathway that leads to activated Vitamin D?
UV acts on 7-dehydrocholesterol > cholecalciferol > calcidiol (liver) > calcitriol (kidney)
What are 3 actions of calcitriol?
Stimulates intestines to absorb calcium and phosphate
Promotes urinary resorption of Ca+
Promotes osteoclast activity
Where is Calcitonin produced?
By C cells in the thyroid
remember ultimobranchial body
What does calcitonin do?
Reduce osteoclast activity
Increase osteoblast activity
(TONES down CALcium)
T/F
Calcitonin has equal effects in children and adults.
False
Powerful effect in children not seen in adults
How does PTH mobilize Calcium from bone?
Stimulates osteoblasts to release osteoclast stimulating factor that promotes osteoclast multiplication and activity
Why does PTH inhibit collagen synthesis?
It takes a lot of calcium to make collagen, and the point of PTH is to free up calcium and increase its levels in the bloodstream.
What class of drug is given as treatment for osteoporosis?
Bisphosphonates
How do bisphosphonates work, and what bone does it protect?
Binds hydroxyapatite sites necessary for osteoclast attachment. This protects old bone.
What is the progression of bone fracture healing?
Hematoma > Soft Callus > Hard Callus > Remodeling
How long does it take to heal a bone fracture?
8-12 weeks
What is the disease that causes excessive bone production that entombs the body in bone?
Fibrodysplasia Ossificans Progressiva
