Skeletal System Flashcards
Long bone features:
Made of cortical bone (compact) and pockets of cancellous bone (spongy)
Contain: epiphysis, diaphysis, medullary cavity, metaphysics and epiphyseal plate
Cortical bone is ________, while cancellous bone is _________
Compact
Spongy
Epiphyses
Ends of long bones
Converted by articular cartilage because they form synovial joints with other bones
Spongy bone containing red bone marrow on the inside, important for hematopoesis (production of RBCs)
Diaphysis
Long, hollow shaft between the epiphyses
The outside is covered in a membrane called the periosteum, which wraps around the cortical bone itself
Medullary cavity
The “hollow” inside of the diaphysis
Contains cancellous bone that hold yellow bone marrow
Lined by a membrane called the endosteum
Epiphyseal plate
“Growth plate”
Made of hyaline cartilage
Lies between the epiphysis and metaphysics
Grows in the direction of the metaphyses but lengthens the diaphysis
Grows in response to growth factors
Ossifies when pubertal hormones signal for calcification and apoptosis
Metaphyses
Found between the medullary cavity and the epiphyseal plate
Short bones
Cuboidal- as wide as they are long
Provide support without doing a lot of movement
Primarily made up of cancellous bone covered by a very thin layer of cortical bone
Ex: bones in the wrist
Flat bones
Consist of cancellous bone sandwiched between cortical bone
Mainly provide protection
Ex: bones that make up the skull, and the sternum
Sesamoid bone
Embedded within tendons to increase the muscles leverage on the bone (eg. help the muscles pull)
Ex: kneecap/patella
Irregular bone
Irregularly shaped
Made of abundant cancellous interior surrounded by a thin layer of cortical bone
Ex: bones of the pelvis and spine
Cortical bone
The dense outer layer of bone that allows bones to support our weight
Composed of microstructures: Osteons, Haversian canals, lamellae, lacunae, canaliculi, and Volkmann’s canals
Osteons
The functional unit of cortical bone
Haversian canal lies in the center of each osteon (which is why osteons are sometimes referred to as Haversian systems)
Haversian canals
- Lie at the center of each osteon
- Contain blood vessels that supply nutrients to the bone cells living in lacunae
- tunnels burrowed by osteoclasts
Volkmann’s canals
Connect adjacent Haversian canals to one another and to the periosteum which provides the blood and nutrients that the bone needs to grow
Lacunae
Small spaces between lamellae that hold trapped bone cells (osteocytes) and
Connect to each other, as well as the Haversian canal through canaliculi allowing for exchange of nutrients
Lamellae
Layers of osteon
Canaliculi
Small channels that connect lacunae and the Haversian canals of a single osteon
Cancellous bone
The inner network of spongy bone
Soaks up red bone marrow is network of trabeculae
Part of bone where hematopoiesis occurs (production of RBCs)
Cells involved in bone remodeling:
Osteoprogenitors
Osteoblasts
Osteoclasts
Osteocytes
Osteoprogenitors
- Immature precursor cells that differentiate into osteoblasts
- part of mesenchymal stem cell lineage
Osteoblasts
- Build bone
- Mononucleated cells
- Mature into osteocytes after getting trapped inside the bone matrix they create
- Secrete proteins (organic compounds) and collagen that make osteoid
- They make the enzyme that allows calcium, phosphorus and water to crystalize into hydroxyapatite
- incapable of mitosis