Skeletal System Flashcards
Classification and functions of bones
A highly specialized supportive tissue which is characterized by its rigidity and hardness
Bones
Four main functions of Bones
● To provide mechanical support
● To permit locomotion
● To provide protection
● To act as metabolic reservoir of minerals
● Mesenchymal cells
● Located in the inner layer of the periosteum (fibrous membrane that covers the surface of the bone) they give rise to osteoblasts
Osteogenic cells
● Bone secreting cells
● During bone formation, they first secrete the amorphous and fibrous (Collagen) components of unmineralized bone, and later they deposit their stored calcium to mineralized or harden the bone
● They line the trabecular (bone material) surfaces of the bone
Osteoblasts
● Mamre bone cells that stop secreting the bone substance
● They are actually osteoblasts which have been trapped in spaces called lacunae in the bone substance during mineralization
● Their main function is to maintain the integrity of the bone by supplying nutrient derived from the blood vessels in thr canaculi
Osteocytes
● Believed to rise from the fusing of osteocytes
● Remodeling cells which are multinucleated in the structure and located in a concavity called the Howship’s lacuna at the bone surface
Osteoclasts
A non-mineral matrix of collagen and glycosaminoglycan
Osteoid
Deposited within the matrix
Inorganic mineral salts
It is the spaces between the adjacent trabeculae
Interosseous space
A portion of the bone substance which is called the bone spicule
Trabeculae
Consisting of few trabeculae and many of the interosseous spaces
Cancellous Bone (Spongy bone)
Consist of extensive lamallae and fewer interosseous spaces. This bone develops into existing trabecullae to form layers called lamallae
Compact Bone (Lamellar Bone)
● Basic unit structure of a compact bone
● Circular structure composed of a central canal called the “Harversian canal” surrounded by concentric layers (lamellae) of bone substance
● Embeded in the lamellae are the bone caniculi containing the cytoplasmic process of the osteocytes
● The Harvasian canal connects a transversely positioned Volkmann’s canal
Osteon or Harversian system
The process by which bone is formed through the secretory activity of the osteoblasts
Osteogenesis
Bone develops in pre-exsisting mesenchymal connective tissue (Bones of this type are called membrane bones)
Intramembranous Ossification
Bones that are developed from pre-existing cartillage. This type of bone growth is responsible for the longitudinal growth of bones. (E.G. Long bones like femur and humerus)
Endochondral Ossification
● Site of bone growth as seen in long bones
● Composed of different zones
A. Zone of growth
B. Zone of cartillage transformation
C. Zone of ossificationEpiphyseal Plate (Epiphyseal Line)
“Great Dimension
- e.g., Forelimb = humerus, radius, ulna, metacarpals, phalanges
Hind limb = femur, tibia, fibula, metatarsals, phalanges
Functions: a. Act as levers
b. For support, locomotion
Long Bones
“Cuboids or equal shape”
- e.g., carpals, tarsals
Function: absorbs concussion
Short Bones
“Thin and expanded”
- e.g., skull, ribs, scapula, pelvic bones
Functions: a. Protect vital organs e.g. brain, lungs
b. Provide areas for muscle attachment
Flat Bones
“Sesame-seed shape develops along the course of tendons”
- e.g., patella
Functions: a. Reduce friction
b. Change the course of tendons
Sesamoid Bones
“Unpaired bones in median plane
- e.g., vertebral column, some bones of the skull
Functions: a. For protection and support
b. For muscle attachment
Irregular Bones
“Presense of air spaces or sinuses that communicate with the exterior”
- e.g., flying birds, maxillary and frontal bones
Pneumatic Bones
“Made up of bones of the limbs bones of the front (pectoral) limbs and bones of the hind (pelvic) limbs
Appendicular Skeleton
