Structure of a long bone diaphysis (shaft/middle of the long bone)



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STRUCTURE OF A LONG BONE
Diaphysis (shaft/middle of the long bone)


  • Nerve fibers & blood vessels

  • Periosteum

  • fibrous connective tissue membrane that covers & protects the diaphysis

  • Sharpey's fibers

  • made of collagen - secures periosteum to underlying compact bone

  • COMPACT BONE:

  • appears very dense & surrounds yellow bone marrow

  • the most superficial bone tissue - provides protective layer

  • STRONG - withstands tremendous impact from the ends - although, a blow from the side will easily break it


Microscopic Arrangement:

  • osteons (Haversian system) - hollow tubes of bone matrix - lacunae surrounding osteocytes are arranged in concentric circles called lamellae around a central canal:

  1. lamellae - layers that contain the lacunae surrounding the osteocytes - cylindrical, which means they surround the central canal - look like growth rings of a tree - contain collagen fibers running in opposite directions which help bone withstand torsion/twisting stresses - lamellae contains/is matrix that is hard and impermeable

  2. within the lamellae are small cavities (lacunae) surrounding single bone cells (osteocytes)

  3. canaliculi are small canals/passageways extending from the lacunae (through the lamellae) that connect the lacunae to each other and to the central canal to exchange nutrients, waste products, and gases

  4. central (Haversian) canal - contains blood vessels & nerve fibers

  • perforating (Volkmann's canal) - connects blood and nerve supplies of periosteum & central & medullary cavity - connects two osteons

  • Yellow Bone Marrow Cavity (Medullary Cavity)

  • Yellow Bone Marrow - a storage area for adipose tissue (fat cells) - energy reserve


Epiphyses (ends of the long bone)


  • Epiphyseal Line - a remnant of the epiphyseal plate/disc (a flat plate of hyaline cartilage)

(Plates are found in young, growing bones and cause the lengthwise growth of a long bone. When hormones stop long bone growth, plates are replaced by bone and only the lines mark their previous locations.)

  • Articular (hyaline) Cartilage - cushions opposing bone ends during joint movement & absorbs stress - decreases friction

  • Compact Bone - in epiphyses, it is a very thin layer

  • SPONGY BONE:

  • more interior bone tissue - has a spikey, open appearance

  • much lighter than compact bone - reduces the weight of the skeleton - makes it easier for muscles to move bones

  • surrounds red bone marrow - protects cells of bone marrow

  • open spaces/cavities are filled with red bone marrow

  • Red Bone Marrow - hematopoietic tissue - site of blood cell formation (mature & immature red blood cells, white blood cells, stem cells)


(Adults have yellow & red bone marrow. Children have all red bone marrow . . . even inside compact bone.)

(Specific bones are used for bone marrow transplants. In adults, the head (epiphysis) of the femur and humerus are used. In addition, the diploe of flat bones (sternum) and irregular bones (hip) are used.)
STRUTURE OF A FLAT BONE


  • Looks like a bone sandwich!!

  • Periosteum covered compact bone makes up the outer slices of bread

  • Spongy bone (called the diploe) makes up the internal filling

  • Marrow located in spongy bone - No official marrow cavity



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