Bone Flashcards
______________________ is the main component of the adult skeleton
Bone
What are some functions of bone?
Support
Movement
Protection
Homeostasis
Bone is a type of what tissue?
Connective
There are two main components to bone. What are they?
ECM
Cells
The extracellular matrix of bone is _________________
Calcified
There are three types of bone cells. What are they?
Osteocytes
Osteoblasts
Osteoclasts
Calcified bone matrix prevents the diffusion of metabolits, so specialized exchange spaces _____________________ allow for nutrient exchange between osteocytes and blood capillaries
Canaliculi
All bones are lined on internal and external surface by layers of CT containing ________________ cells
Osteogenic
The _____________________ is internal and surrounds the marrow cavity
Endosteum
The ___________________ is external
Periosteum
The ________________ and ______________ are types of connective tissues that layer the surface of bones
Endosteum
Periosteum
__________________ are found in lacunae between bone
matrix layers (lamella) and have cytoplasmic processes in small canaliculi that extend into the matrix
Osteocytes
______________________ are growing cells that synthesize and secrete organic components of bone matrix
Osteoblasts
____________________ are giant multi-nucleated cells involved in removing calcified bone matrix and bone remodeling
Osteoclasts
_______________________ originate from mesenchymal stem cells and when active are located at the surface of bone matrix
Osteoblasts
Active osteoblasts are found at the surface of the bone matrix, bound by _____________________, where they form a single layer of __________________ cells joined by adherent and gap junctions
Integrins
Cuboidal
Some inactive osteoblasts differentiate into ____________________ as they are entrapped in the matrix-bound lacunae while others flatten and cover the matrix as ________________________; the majority, however, undergo apoptosis
Osteocytes
Bone-lining cells
______________________ produce the organic components of the bone matrix and therefore contribute to appositional growth
Osteoblasts
Osteoblasts secrete type __ collagen, proteoglycans, and matricellular glycoproteins, like _____________________
Type I collagen
Osteonectin
___________________________ is a layer of unique collagen-rich material between the osteoblast layer and pre-existing bone surface
Osteoid
Some osteoblasts become surrounded by the material they secrete and differentiate as __________________ enclosed singly in _______________
Osteocytes
Lacunae
What’s the function of osteocytes?
Maintenance of the bony matrix
Upon death they are resorbed into the matrix
In the transition from osteoblasts to osteocytes, the cells extend many long _____________________________ surrounded by calcifying matrix
Cytoplasmic processes
An osteocyte and its processes occupy each _______________ and the ____________________ radiating from it
Lacuna
Canaliculi
________________________ are very large motile cells with multiple nuceli that are necessary for bone matrix resorption during bone growth and remodeling
Osteoclasts
What are osteoclasts large and multinucleated?
Because they derive from the fusion of bone marrow derived monocytes
Where are osteoclasts located?
In areas of bone undergoing resorption; they lie in depression or crypts in the matrix called resorption bays
_________________________ is the process by which osteoclasts break down bone and release its minerals, resulting in the transfer of calcium from bone fluid to blood
Bone resorption
What are resorption bays?
Also called Howship lacunae, these are areas of bone undergoing resorption
Active osteoclasts have a ______________________, a domain of the membrane that contacts the bone and binds cells tightly to the bone matrix
Sealing membrane
The sealizing zone surrounds an area with many surface projections called the ______________________ of osteoclasts
Ruffle border
The sealing zone forms a specialized microenvironment between osteoclast and matrix where ____________________ are pumped to acidify the region and promote the breakdown of matrix proteins
Protons
Bone is __________ water and 50% of its dry weight is inorganic matter
25%
25% of bone is organic matter of which 99& is ____________________
Type I collagen
The remaining 1% of organic matter in bone is composed of small proteoglycans and multiadhesive glycoproteins known as ______________________ and calcium-binding proteins called ___________________
Osteonectin
Osteocalcin
What are osteonectins?
Small proteoglycans and multiadhesive glycoproteins of the bone matrix
What is osteocalcin?
A calcium-binding protein released from cells in bone matrix to promote calcification
Why don’t other tissues rich in type I collagen calcify?
No osteocalcin
The external and internal surfaces of bone are covered by layers of bone-forming cells and vascularized connective tissue. The ______________________ consists of dense fibrous outer layer of collagen bundles and fibroblasts while the marrow cavities are lined by ___________________, a single very thin layer of connective tissue that contains flattened osteoprogenitor cells and osteoblasts
Periosteum
Endosteum
What are the functions of periosteum and endosteum?
Nutrition of osseous tissue
Provision of continous supply of new osteoblasts for repair and growth of bone
There are four bone classifications by shape. What are they?
Long bone
Short bone
Irregular bone
Flat bone
Long bones can be divided into the ____________________ or ends and the _____________________ or middle
Epiphyses
Diaphysis
The _____________________ are cancellous bone covered by thin layers of compart cortical
Epiphyses
______________ bone is also known as cancellous bone
Spongy
The _________________________ is composed of dense compact bone with a thin region of cancellous bone on the inner surface around the marrow cavity
Diaphysis
_______________________ bones have cores of cancellous bone surrounded by compact bone
Short bones
Short bones include the ____________________ of the wrists
Metacarpals
____________________ bones are composed of two layers of compact bone called _________________ that are separated by a thicker layer of cancellous bone called the ________________
Flat bones
Plates
Diploe
There are two primary types of bone: ____________________ or cortical bone and ___________________ or trabecular bone
Compact
Cancellous
80% of total bone mass belongs to __________________ bone
Compact
20% of total bone mass belongs to ____________ bone
Cancellous
Compact bone is a dense area near the ______________ of bones while cancellous bone can be found __________________ with interconnecting cavities
Surface
Deeper
Both compact and cancellous bone show two types of organization. What are they?
Woven bone
Lamellar bone
________________ bone is developing with newly formed and random arrangement of components
Woven
__________________ bone presents as a matrix with discrete sheets
Lamellar bone
Primary or _______________ bone tissue is the first to appear in embryonic development and fracture repair; it is marked by a random disposition of fine collagen fibers and is temporary, later replaced by secondary bone tissue in adults
Woven
Which has a lower mineral content? Woven or lamellar bone?
Woven
Which has a higher proportion of osteocytes? Woven (primary) or lamellar (secondary)
Woven (primary)
Lamellar or __________________ bone tissue is found in adults and contains multiple layers of calcified matrix that is highly organized, either parallel to each other or concentrically around a vascular canal
Secondary
The __________________ is a concentric bony lamellae surrounding a small canal formerly known as a Haversian system
Osteon
In secondary bone, lacunae with osteocytes are found between the lamellae and interconnected by ______________________, which allows all cells to be in contact with the source of nutrients and oxygen in the osteonic cancal
Canaliculi
The outer boundary of each osteon is a more collagen-rich layer called the _____________________
Cement line
The osten was formerly known as a _______________________
Haversian system
_____________________ is a long, often bifurcated cylinder generally parallel to the long axis of the diaphysis of bone and is surrounded by four to ten concentric lamellae
Osteon
Between the two circumferential osteon systems are numerous irregularly shaped groups of parallel lamellae called ________________________
Interstitial lamellae
_________________ lamellae are lamella remaining from osteons partially destroyed by osteoclasts during growth and remodeling of bone
Interstitital lamellae
Each osteon is lined with _______________ over its cancal, which contains blood vessels, nerves, and loose connective tissue
Endosteum
How do central canals communicate with one another and the periosteum?
Perforating (Volkmann) cancal
Bone ______________________ is continuous throughout the life and involves a combination of bone synthesis and removal
Remodeling
In _______________ bone, remodeling resorbs parts of old osteons and produces new ones
Compact
In healthy adults, how much (percentage wise) of bone turns over annually?
5 to 10 percent
________________ is the process of bone development
Osteogenesis
There are two osteogenesis processes. What are they?
Intramembranous ossification
Endochondral ossification
In ___________________________ ossification, osteoblasts differentiate directly from mesenchyme and begin secreting osteoid
Intramembranous
The bones of the skull, jaw, scapula, and clavicle develop via ______________________
Intramembranous ossification
In ___________________ ossification, the preexisting matrix of hyaline cartilage is eroded and invaded by osteoblasts, which then begin producing osteoid
Endochondral ossification
What type of ossification forms most bones of the body and is especially well studied in lone bone?
Endochondral ossification
Where would you find older bone in long bone?
In the diaphysis, toward the center
There are four steps to intramembranous ossification. What are they?
- Mesenchymal cells group into clusters and ossification centers form
- Secreted osteoids trap osteoblasts, which then become osteocytes
- Trabecular matrix and periosteum form
- Compact bone develops superficially to the trabecular bone and crowed blood vessels condense into red marrow
In intramembranous ossification, ___________________ group into clusters and ossification centers form. Then secreted ______________ trap osteoblasts, which then become osteocytes, and the _______________ and periosteum form. Finally, ___________ bone develops superficially to the trabecular bone and crowed blood vessels condense into red marrow
Mesenchymal stem cells
Osteoids
Trabecular matrix
Compact
In _____________________ ossification, ossification centers produce cavities that are gradually filled with bone marrow
Endochondral
The ______________________ is the first site of bone formation in endochondral ossification, where cartilage has begun to degenerate
Primary ossification center
Where does the primary ossification center form?
Diaphysis
The ______________________ forms later in endochondral ossification in the epiphysis
Secondary ossification center
Endochondral ossification:
- A cartilage model surrounded by ________________ is produced by _______________ that become _________________ enclosed by cartilage matrix
- The ________________ of the diaphysis becomes the _______________, and a bone collar is produced. Internally, the chondrocytes hypertrophy and calcified cartilage is formed
Perichondrium
Chondroblasts
Chondrocytes
Perichondrium
Periosteum
Endochondral ossification
- A ___________________ center forms as blood vessels and osteoblasts invade the calcified cartilage; the osteoblasts lay down bone matrix, forming _________________ bone
- The process of bone collar formation, cartilage calcification, and cancellous bone production continues. Calcified cartilage beings to form in the ______________. A medullary cavity begins to form in the center of the diaphysis
Primary ossification center
Cancellous
Epiphyses
