C6 7-11 Flashcards
Gross anatomy of a long bone?
Diaphysis, medullary cavity, epiphyses, epiphyseal line or plate.
Has periosteum, endosteum
Gross anatomy of a flat bone?
Thin layer of diploe covered by compact bone. Periosteum/endosteum. Contain marrow, but do not have a defined cavity.
Diploe
Internal layer of SPONGY bone in flat, short and irregular bones
Diaphysis
tubular shaft consisting of compact bone
Epiphyses
expanded area at each end of the diaphysis in a long bone.
containing mostly spongy bone
Layer of articular cartilage
Epiphyseal line and plate
Hyaline cartilage at the junction of the diaphysis and epiphysis that provides for growth at the end of a long bone. (Plate = young, line = adult)
Periosteum
Double layered CT that covers and nourishes the bone (does not cover joint surfaces) (fibrous layer dense irreg, osteogenic layer of osteogenic stem cells)
Endosteum
Covers internal bone surfaces. Contains osteogenic cells, osteoblasts, osteoclasts
Medullary cavity
Central cavity of a long bone. Contains yellow or red marrow.
Trabeculae
Strut or thin plate in SPONGY bone
(Align precisely along lines of stress and help bones resist stress)
Only a few cells thick, contain irregularly arranged lamellae, osteocytes and are connected by canaliculi
Yellow marrow - location/function
LOC: medullary cavity, spongy bone FCTN: fat storage
Red marrow - location/function
LOC: trabecular cavities in spongy bone in long bones, diploe of flat bones.
FCTN: hematopoiesis
(in adults red marrow is found in ends of pelvis/femur/humerus, vertebrae bodies, ribs, sternum.)
Articular cartilage
Hyaline CT that covers the end of bones rather than periosteum
Cells in bone?
Osteogenic, osteoblasts, Osteoclasts, osteocytes
Osteogenic cell function?
Mesenchymal stem cells that divide to produce osteoblasts. Found in the inner layer of periosteum and the endosteum.
Osteoblast cell function?
Produce new bone matrix (ossification). Release the proteins and other organic components of matrix. (matrix is called osteoid)
Osteoclast cell function?
Break down bone (osteolysis/resorption) via proteases (protein digesting and acids). Important in Ca and phosphate homeostasis. Giant cells with 50 or more nuclei. Not related to osteoprogenitor cells or their descendents - derived from the samestem cells that produce monocytes and macrophages
Osteocyte function?
Maintain present bone. Mature bone cells that make up most of cell population.
Compact bone?
relatively solid, forms a sturdy protective layer that usually surrounds a medullary cavity with osteons. Contains: Osteons, lamellae, central haversian/volkmann’s canals, osteocytes, lacunae, canaliculi
Spongy or cancellous bone?
consists of an open network of struts [trabeculae] and plates that resembles latticework with a thin covering Contains: trabeculae. Can contain either red or yellow marrow
Osteon/Haversian system
basic functional unit of mature compact bone. Compressional strength comes from matrix - resilience comes from collagen fibers.
Lamellae
- layers of matrix/matix tube in compact bone.
- Collagen fibers alternate direction in the lamella.
- withstand torsion
Central (haversian) canals
Run thru core of Osteon, contain blood vessels and nerve fibers
Volkmann’s canals
Lie at right angles to long axis of bone and connect blood and nerve supply to medullary cavity
Canaliculi
Tiny canals that connect osteocytes in the lacunae with one another (communication) and allow for nutrients and wastes to be relayed.
Chemical composition of bones - organic
Cells, osteoid (matrix - proteoglycans/glycoproteins/collagen)
Give bone tensile strength by resisting stretching and twisting and contribute to overall flexibility.
Chemical composition of bones - inorganic
Calcium phosphate (primary) + calcium hydroxide forms crystals of hydroxyapatite. Include other salts and ions also. Crystals harden the matrix and account for the rigidity or relative inflexibility of bone that provide its compressioinal strength.
Two types of bony skeleton formation?
Intramembranous ossification, edochondral ossification
Intramembrous ossification steps
Almost always flat bone.
- ossification centers appear in the fibrous ct membrane.
- Osteoid is secreted by mesenchymal cells within the fibrous membrane and calcifies and trapped osteoblasts become osteocytes.
- Woven bone and periosteum form.
- lamellar bone replaces woven bone, just deep to the periosteum and red marrow appears
Endochondral ossification steps
Almost all bone except flat bone. 1. bone collar forms around diaphysis of the hyaline cartilage model.
- cartilage in the center of the diaphysis calcifies and then develops cavities.
- The periosteal bud invades the internal cavities and spongy bone forms.
- Diaphysis elongates, medullary cavity forms, ossification centers appear in epiphysis
- Epiphysis ossify, hyaline remains only in epiphyseal plates and articular cartilage
Lacunae
Small space/depression/cavity. Lacunae at the junctions of lamellae are occupied by osteocytes
Osteoid
Unmineralized bone matrix
Ossification/osteogenesis
Process of bone formation
What does an osteon consist of?
Lamellae, central/haversian canals, volkmanns canals, osteocytes in lacunae, canaliculi
Endochondral vs intramembranous
ORIGIN TISSUE: I = membranes of embryonic ct, E = preformed in hyaline cartilage
OSTEOBLAST ORIGIN: I = ct cells become osteoblasts, E = cartilage is calcified and osteoblasts derive from perichondrium
GROWTH: I = osteoblasts from the periosteum deposit compact bone over spongy, I = osteoblasts of periosteum form collar of compact bone that grows towards the end of each bone
WHERE: I = skull bones, E = most bones of the body
