Skeletal System Flashcards
Bone Classification
Compact Bone
-dense, looks smooth and homogeneous
Spongy Bone
-small, needle-like pieces of bone, lots of open space
Long Bones
- shaft with heads and both ends, mostly compact
- limbs
Short Bones
-cube-shaped, mostly spongy, wrist, ankle
Flat Bones
- thin, flattened, usually curved
- 2 layers of compact sandwiching spongy
- skull, ribs, sternum
Irregular Bones
- all other bones
- vertebrae, hip bones
Functions of Bones
1) Support
- internal framework
- legs are pillars to support trunk
2) Protect
- soft body organs
- skull, vertebrae, rib cage
3) Move
- skeletal muscles use bones as levers
4) Storage
- fats and minerals (calcium and phosphorus)
5) Blood Cell Formation
- hematopoiesis
- within marrow cavities
Gross Anatomy of Long Bone
Diaphysis
- shaft, makes up bone’s length
- compact bone
Periosteum
-fibrous, connective tissue covering and protecting diaphysis
Epiphyses
- ends of long bone
- compact bone enclosing spongy bone
Articular Cartilage
- glassy, hyaline cartilage which covers external surface
- provides smooth, slippery surface to decrease joint friction
Epiphyseal Line
- thin line of bony tissue in adults spanning epiphysis
- remnant of epiphyseal plate
Medullary Cavity
- cavity of shaft to store adipose tissue
- yellow marrow
- adults
Red Marrow
-cavity of shaft to form RBC in infants
Endosteum
-thin membrane lining medullary cavity
Microscopic Structure-Compact Bone
- outer layer hard and dense, appears solid
- osteons
- structural units of matrix
- aka haversian systems
- concentric lamella
- each osteon composed of calcified matrix arranged in layers
Microscopic Structure-Spongy Bone
- aka cancellous bone
- porous, end of long bone
- many spaces, filled with marrow
- trabeculae
- needle-like threads of spongy bone
Microscopic Structure-Bones in General
- osteocytes (bone cells)
- lacunae
- little spaces between hard layers of lamellae where mature bone cells lie
- canaliculi
- tiny passageways which connect lacunae with each other and central canal in each osteon
- how nutrients move from vessel to osteocytes
Cartilage
- more of intercellular substance than of cells
- fibers embedded in firm gel (not cement of bone)
- chondrocytes
- cartilage cells located in lacunae, suspended in matrix
- nutrients must diffuse through matrix to get to cells
- rebuilds itself very slowly
Bone Formation
-aka ossification
-use hyaline cartilage from fetus as ‘model’
-cartilage covered with bone matrix by bone-forming cells (osteoblasts)
-enclosed cartilage is digested, forming medullary cavity
-most bones converted by birth
except articular cartilage, epiphyseal plates and nose plate
-growth ceases when all epiphyseal cartilage becomes bone
Bone Growth
- new cartilage forms on external face of articular cartilage and epiphyseal plate
- old cartilage broken down and replace with bony matrix
- controlled by growth and sex hormones
- ends during adolescence
Bone Remodeling
- osteoclasts break down bone matrix and release calcium ions into blood
- calcium deposited in bone matrix
- occurs when increased strength required by bulky muscles
- bones must respond to pull of gravity and muscles on skeleton
- bones dynamic and active tissue
- elderly and bed-ridden lose mass and atrophy
Axial Skeleton
- bones of center (skull, spine, chest)
- 80 bones
Axial-Skull-Cranial Bones
- frontal (forehead)
- parietal (bulging topside)
- temporal (lower sides and around ears)
- occipital (back)
- sphenoid (central part of floor)
- ethmoid (floor of cranium)
Axial-Skull-Facial Bones
- nasal (upper bridge of nose)
- maxilla (upper jaws)
- zygomatic (cheeks)
- mandible (lower jaw)
- lacrimal (medial wall of eye socket)
- palatine (roof of mouth)
- inferior nasal concha (inside wall of nose)
- vomer (lower back nasal septum)
Axial-Skull-Ear
- malleus (hammer)
- incus (anvil)
- stapes (stirrup)
Axial-Skull-Other
-sinuses (cavities within cranial bones)
paranasal (openings in nose)
-sutures (immovable joints)
-fontanels (soft spots, areas where ossification incomplete)
