Anatomy Unit 4 Skeletal System (Part 2)

what kind of tissue is osseous tissue?

connective tissue

describe the 4 traits of osseous tissue

• matrix

  • allows for strength and flexibility

    • calcium salts → strength

    • collagen fibers → flexibility

• osteocytes

  • located in lacunae (organized around blood vessels)

• canaliculi

  • narrow passages through the matrix

    • allow for exchange of materials between bone and blood

• periosteum

  • covers bone surfaces (EXCEPT joints)

    • outer fibrous layer

    • inner cellular layer

what is an osteocyte? describe its location and functions

mature bone cell

• located in a lacunae

• functions:

  • cannot divide

  • makes up most of bone cells

  • maintains bone matrix

  • helps repair damaged bone

what is an osteoblast? describe its functions

immature bone cell

• functions:

  • makes new bone matrix (osteogenesis)

  • becomes an osteocyte after fully surrounded by the matrix

describe the appearance and functions of an osteoclast. why is it vital?

• appearance:

  • giant, multinucleated cells

• functions:

  • removes and recycles bone matrix

  • secretes acids and proteolytic enzymes to perform osteolysis (erosion of bone matrix)

* the balance between osteoblasts and osteoclasts helps maintain homeostasis (why exercise is essential)

what is an osteoprogenitor? describe its function and locations

stem cells that divide to make osteoblasts

• function: repair bone fractures

• locations:

  • inner cellular layer of the periosteum

  • inner layer of endosteum

    • lines bone marrow cavities

describe the composition of compact bone

• 20% of bones, represents 80% of total weight

• rigid support shell

describe the composition of spongy bone

• makes up 80% of bone

  • much less dense

• has many open spaces called trabeculae

what is a unit of compact bone called? what canals does it contain? describe their features

• osteon = functional unit of a mature compact bone

  • osteocytes are in the concentric circles around the central canal (Haversian Canal)

• central canal (Haversian Canal)

  • contains 1+ blood vessels

  • acts as a passageway for nerves and blood vessels

  • runs parallel to the surface of the bone

• perforating canals (canals of Volkmann)

  • runs perpendicular to the surface of the bone

    • brings blood deeper into the bone and to the marrow cavity

what are lamellae? what are the 3 types of lamellae? describe them

a thin layer or membrane

• concentric

  • nested cylinders

  • provides strength

• interstitial

  • in-between spaces

• circumferential

  • found at the outer and inner surfaces of bone

describe the functions and locations of spongy bone

• functions:

  • forms struts and plates called trabeculae

    • no blood vessels within trabeculae

  • houses red and yellow bone marrow

• locations:

  • bones that are not heavily stressed

  • bones with stress from many directions

what are the two types of bone marrow?

• red

• yellow

describe the composition and location of red bone marrow

• made up of stem cells that form blood cells

• found only in epiphyses of long and spongy bones

describe the composition, location, and function of yellow bone marrow

• made up of mostly fat cells

• found in most bones

• functions:

  • acts as a food reserve for bone cells

  • can be converted to red marrow when there is significant blood loss

what are the two types of bone coverings?

• periosteum (outer)

• endosteum (inner)

describe the functions of the periosteum

• covers all bones except those within joint cavities

• isolates bones from other surrounding tissues

• provides blood and nervous access

• facilitates bone growth and repair

what is the endosteum? describe its functions

an incomplete cellular layer

• functions:

  • lines medullary (marrow) cavity

  • lines trabeculae and central canals

  • facilitates bone growth and repair