Unit 2 Videos 7-9 Flashcards
What is the skeletal system composed of:
Bones and cartilage.
Bones, referred to as connective tissue, consist of:
(osseous)
Cells
Extracellular matrix (ground substance + fibers)
The living / dynamic tissues are capable of repair and growth.
Bone, referred to as an organ, consists of:
(osseous)
osseous tissue
nervous tissue
epithelial and muscle tissue
Ex, femur, humerus, clavical, sternum
Compact bone
Dense outer layer
Spongey bone
A honeycomb of trabeculae filled with yellow bone marrow.
The function of the bone
Support - Form the framework that supports the body
Protection - Provide a protection cavity for the brain (skull), Spinal cord (vertebrae), and Vital organs (rib cage)
Movement - Provide attachment points for skeletal muscles and are used as levers
Mineral storage - reservoir for calcium and phosphors
Blood cell formation ( hemopoiesis) - occurs within the red bone marrow of the bones.
What are long bones?
A bone that is longer than they are wide.
ex humerus, femur, tibia
What are short bones?
Cube-shaped bones of the wrist and ankle
Bones that form within tendons (patella)
What are flat bones?
Thin, Flattened, and a bit curved.
Ex. most bones in the skull and sternum
What are irregular bones?
Bone with complicated shapes
ex: vertebrae and os coxae
What are the regions of the long bone?
Diaphyisis
elongated, usually cylindrical shaft
provides for leverage and major weight support
compact bones with thin spicules of spongey bone extending out the word
medullary cavity ( cavity in Diaphyis)
hollow, cylindrical space within Diaphysis
contains red bone marrow
contains yellow bone marrow in adults
What are the regions of the long bone?
Epiphysis ( red bone marrow)
The knobby region at the ends of the long bone
Proximal epiphysis - end of the bone closest to the trunk
Distal epiphysis - end furthest from the trunk
Composed of:
the outer layer of compact bone
inner layer spongey
The joint surface is covered by a thin layer of hyaline cartilage:
termed articular cartilage
helps reduce friction and absorb shock in moveable joints.
What are the regions of the long bone?
Metaphysis
- the region of mature bone between epiphysis and diaphysis
Epiphyseal plate
- in metaphysis
- thin layer of hyaline cartalige
- provides for continued lengthwise growth
- remnant in adults termed epiphyseal line
What is periosteum?
Doubled layer protective membrane. Outside of the bone.
- The outer fibrous layer is dense regular connective tissue
- The inner osteogenic layer is composed of osteoblast and osteoclast
- richly supplied with nerve fibers, blood, and lymphatic vessels. enter the bone via nutrient foramina
- secured to underlying bone by Shaprleys fibers
What is endosteum?
inside of bone
- Covers all internal surfaces of bone within the medullary cavity
- an incomplete layer of cells
- contains osteoprogenitor cells, osteoblast, and osteoclast
- tough sheath covering the outer surface of the bone.
-
Structure of short, flat, and irregular bone.
- external surface of compact bone
- interior composed of spongey bone called diploe
- lack a medullary cavity
Location of red bone marrow.
in infants
- found in the medullary cavity and all areas of spongey bone
In adults
- found in the diploe of flat bones
-The head of the humerus and femur
What is osteon?
The structural unit of the compact bone.
What is lamella?
Weight-bearing, colom-like matrix tubes are composed mostly of college.
What is the central canal?
Central channel containing blood vessels and nerves.
What are Volkmann’s canals?
Channels lying at the right angles to the central canal connect the blood and nerve supply of the periosteum to the haversine canal.
What are osteoprogenitor cells?
- Stem cells derived from mesenchyme
- Produced cells that mature to become osteoblast
- located in periosteum and endosteum
What are osteoblasts?
Build bone
- Often positioned side by side on bone surface
- synthesize and secrete osteoid
Initial semisolid from bone matrix
later calcifies
- Become entrapped within the matrix they produce
What are osteocytes?
- Mature bone cells derived from osteoblast
- have lost bone-forming ability
- maintain bone matrix
- detect mechanical stress on bone
- may trigger bone matrix of new bone matrix
What are osteoclasts?
- Large, Multinuclear, phagocytic cells
- Derived from fused bone marrow
- Ruffled border to increase the surface area exposed to bone
- Often located within or adjacent to the depression pit on the bone surface. (respobrtion lacunae)
- involved in breaking down bone
What two vitamins are needed in bone formation?
Vitamin D - for calcium absorption
vitamin C - collagen formation
What does resorption mean?
to break down the bone by osteoclast
Calcium is released into the bloodstream
What organic substances compose a bone matrix?
The organic compound is osteoid, composed of collagen, proteoglycans, and glycoproteins.
What inorganic substances compose a bone matrix?
The inorganic component is formed from hydroxyapatite. Which includes calcium phosphate, other salts and ions, calcium carbonate, sodium, magnesium ion
What is ossification or osteogenesis?
- The formation and development of bone connective tissues
- begins in the embryo
- continues through childhood and adolescents
- begins by 8 through 12 weeks of embryonic development
- occurs through intramenbrous ossification or endochondral ossification
What is intramembrnous ossification?
- formation in most of the flat bones in the skull and clavicle
- fibrous connective tissue membranes are formed by mesenchymal cells
Steps of intramembranous ossification.
- ossification centers appear in the fibrous connective tissue membrane ( osteoid secret)
- Osteiod is secreted within the fibrous membrane and calcifies ( become osteocytes trapped in lacunae)
- woven bone (trabeculae) and periosteum form ( blood vessels pass through diploe)
- lamellar bone replaces woven bone, just deep to the periosteum. Red bone marrow appears
What bones are formed from intramembranous ossifaction?
Flat bones of the skull, some facial bones, the manubrium, and the central part of the clavicle.
What is endochonral ossifaction?
- begins with a hyaline cartilage model
- produce most bones of the skeleton, including bones of upper and lower limbs, pelvis, vertebrae, and ends of clavicle.
Process of endochonral ossifaction
- The fetal hyaline cartilage model develops
- Cartalige calcifies, and a periosteal bone collar forms around diaphysis
- primary ossification center forms in the diaphysis
- secondary ossification center form in the epiphysis
- bone replaces cartilage, except for the growth plate. (epiphyseal plate)
- epiphyseal plates ossify and turn into epiphyseal lines. ( stop growing lengthwise)
Interstitial growth
Bone growth in length
- occurs within Zone 2 and Zone 3
- pushes zones of resting cartilage towards the epiphysis
- Flexible hyaline cartilage permitting growth
- new hyaline cartilage replaced by bone
- similar to endochondral ossification during development.
Appositional Groth
Width of bone growth
- Bone grows in diameter
- occurs within the periosteum (outermost side)
- bone matrix deposit within layers parallel to the surface
- Layers termed external circumferential lamella
as they increase in number, they increase in diameter
-osteoclast resorb bone matrix along the medullary cavity
- transforms infant’s bone into adult bone
What is mechanical stress?
- occurs in weight-bearing movement and excise
- required for normal bone remodeling
- detected by osteocytes and communicated to osteoblast
- osteoblast synthesis of osteoid
- cause an increase in bone strength
- results from skeletal contraction and gravitational forces
What do you do to increase bone mass?
Exercise from weight lifting, running, walking, etc.
What do you do to decrease bone mass?
-removal of mechanical stressors
- reduce collagen formation
- demineralization
decreased strength of unstressed bone in immobilized fracture