Week 4- Skeletal System Flashcards
Types of Bones
Compact and Spongy
Compact Bone
-Rigid
-appears white, smooth, and solid
-80% total bone mass
Spongy Bone
-internal to compact
-porous
-20% total bone mass
Function of Bone
1) Support and Protection
2) Levers for Movement
3) Storage of Minerals and Energy Reserves
Support and Protection
-Provide structural support and serves as framework for entire body
-Protects tissues/organs from injury/trauma
Levers for Movement
-Serve as attachment sites for skeletal muscles, soft tissues, and some organs
-Muscles attached to bone contract and exert pull on skeleton, which functions as a system of levers
-Can alter direction and magnitude of forces generated by skeletal muscles (powerful vs precise)
Storage of Minerals and Energy Reserves
-Most of body’s calcium and phosphate are stored within and released from bone
-When calcium or phosphate is needed, some bone gets broken down and minerals are released into blood
-Potential energy in lipid form stored in yellow bone marrow sometimes
Calcium
Essential for muscle contraction, blood clotting, and release of neurotransmitters from nerve cells
Phosphate
-Structural component of ATP, other nucleotides, and phospholipids
-Important component of plasma membrane
Hematopoiesis
-Process of blood cell production
-Occurs in red bone marrow(contains stem cells that form blood cells and platelets)
Classes of Bones
1) Long Bones
2) Short Bones
3) Flat Bones
4) Irregular bones
Long Bones
-greater in length than width
-bones have elongated, cylindrical shaft (diaphysis)
-most common bone shape
-found in upper and lower limbs
-examples: metatarsals, femur, tibia, fibula
Short Bones
-length nearly equal to width
-Ex: carpals and tarsals
-Sesamoid bones: small sesame shaped bones along tendons of some muscles (ex: patella)
Flat Bones
-Flat, thin surfaces that may be slightly curved
-Provide extensive surface areas for muscle attachment and protect underlying soft tissues
-Form roof of skull, scapulae, sternum, and ribs
Irregular Bones
-Elaborate, sometimes complex shapes
-Vertebrae, ossa coxae, and several skull bones (ethmoid, sphenoid, and maxilla)
Regions of Long Bones
-Diaphysis
-Epiphysis
-Metaphysis
Diaphysis
-elongated, cylindrical shaft
-provides leverage and support
-composed of compact bone and spongy bones extends internally from compact in form of spicules(thin needlelike structures)
Medullary Cavity
-Hollow, cylindrical space within diaphysis
-contains bone marrow
Epiphysis
-expanded, knobby region at ends of each bone
-composed of outer, thin layer of compact bone and inner, more extensive region of spongy bone
-spongy bone resists stress that is applied from many directions
Proximal epiphysis
End closest to trunk
Distal epiphysis
End furthest from trunk
Articular cartilage
-Thin layer of hyaline cartilage covers joint surfaces of epiphysis
-Helps reduce friction and absorb shock in moveable joints
Metaphysis
-Region where bone widens and transfers forces between diaphysis and epiphysis
-Thin layer of hyaline cartilage provides for continued lengthwise growth
-contains epiphyseal plate in growing bones
Coverings and Linings of Long Bones
-Periosteum
-Endosteum
Periosteum
-Tough sheath that covers outer surface of bone except for areas cover by articular cartilage
-Responsible for width growth
-anchored to bone by numerous collagen fibers(perforating fibers) which run perpendicular to diaphysis
Layers of Periosteum
-Outer, fibrous layer
-Inner, cellular layer
Fibrous Layer
-made of dense irregular connective tissue
-protects bone from surrounding structures, anchors blood vessels/nerves to surface of bones, and serves as attachment site for tendons and ligaments
Cellular layer
-includes osteoprogenitor cells, osteoblasts, and osteoclasts
-osteoprogenitor cells and osteoblasts produce circumferential layers of bone matrix
Endosteum
-Very thin layer of connective tissue containing osteoprogenitor cells, osteoblasts, and osteoclasts
-covers all internal surfaces of bone within medullary cavity
-active during bone growth, repair, and remodeling
Anatomy of other bone classes
-external surface= compact bone covered by periosteum
-interior= spongy bone
-no medullary cavity
-in flat bones of skull
Blood Supply and Innervation
-bone is highly vascularized, especially regions with spongy bone
-blood vessels enter from periosteum
-nerves accompany blood vessels through nutrient foramen and innervate bone, periosteum, endosteum, and marrow cavity
-mainly sensory nerves
Nutrient Foramen
Small opening/hole through which 1 nutrient artery enters and 1 nutrient vein exits
Bone Marrow
-Soft connective tissue of bone
-2 types: Red and yellow
Red Bone Marrow
-contains reticular connective tissue, developing blood cells, and adipocytes
-primary function is hematopoiesis
-in children, it’s widely distributed and located in spongy bone of most bones and medullary cavity of long bones
-in adults, in select bones of axial skeletons (flat bones of skull, vertebrae, ribs, sternum, and ossa coxae) and in proximal epiphyses of each humerus and femur
Yellow Bone Marrow
-Within medullary cavity of long bones and inner core of epiphyses there is a decrease in developing blood cells and increase in adipocytes
-fatty appearing substance
-severe anemia may cause yellow to turn to red to produce RBCs
Cells in Bone
-Osteoprogenitor cells
-Osteoblasts
-Osteocytes
-Osteoclasts
Osteoprogenitor cells
-stem cells derived from mesenchyme
-when they divide, produce stem cell and committed cell (matures to osteoblast)
-in periosteum and endosteum
Osteoblasts
-form new bone
-synthesize and secrete initial semisolid bone matrix called osteoid (later calcifies)
-as a result of mineral deposition, osteoblasts become trapped and mature into osteocytes
Osteocytes
-mature cells that lost ability to form bone
-maintain matrix and detect mechanical stress
Osteoclasts
-large multinuclear phagocytic cells
-involved in breaking down bone in process called bone resorption
Composition of Bone Matrix
Organic and Inorganic component
Organic Component
-Osteoid
-collagen and semisolid ground substance of proteoglycans and glycoproteins
-gives bone tensile strength by resisting stretch/twisting
Inorganic Component
-Calcium and phosphate
-provide bone with rigidity/inflexibility
Bone Formation
-begins with osteoblasts secreting osteoid
-calcification occurs subsequently with osteoid deposition
-requires many substances (vitamin D, vitamin C, calcium, and phosphate)
Bone Resorption
-bone matrix is destroyed by osteoclasts
-occurs when blood calcium levels are low