Chapter6 Flashcards
- contain no blood vessels/nerves
- dense connective tissue girdle of perichondrium contains blood vessels for nutrient delivery to cartilage
skeletal cartilages
- most abundant type of cartilage
- provides support, flexibility, and resilience
- can be found in costal cartilages, nose, thyroid cartilage
hyaline cartilages
- simlar to hyaline cartilages but contain elastic fibers
- found in external ear or epiglottis
elastic cartilages
- includes collagen fibers
- has great tensile strength
- sites subjected to both pressure and stretch such as menisci of the knee and discs btw vertebrae
fibrocartilage
- cells secrete matrix against the external face of existing cartilage
appositional growth (growth from outside)
- lacunae bound chondrocytes divide and secrete new matrix, expanding cartilage from within
interstatial growth - length (growth from inside)
classification of bones by shape
- long bones- longer than they are wide
- short bones- cubeshaped (wrist or ankle)
- sesamoid- bones within tendons (patella)
- flat bones- thin, flat , slightly curved
- irregular bones- complicated shapes
functions of bones
- support
- protection
- movement
- storage
- blood cell formation
- compact bone collar surrounds medullary(marrow) cavity
- medullary cavity in adults contain fat(yellow marrow)
Diaphysis(shaft)
[structure of a long bone]
- expanded ends
- spongy bone interior
- epiphysea line (remnant of growth plate)
- articular(hyaline) cartilage on joint surfaces
epiphyses
[structure of long bone]
dense outer layer bone texture
compact bone
honeycomb of trabeculae filled with red or yellow bone marrow
spongy bone
- periosteum: Outer fibrous layer
- endosteum: deliocate connective tissue membrane
membranes of bone
inner osteogenic layer includes:
- osteogenic - stem cells
- osteoblasts- bone forming cells
- osteoclasts- bone destroying cells
nerve fibers, nutrient blood vessels, and lymphatic vessels enter the bone via……
nutrient foramina
- periosteuum
- endosteum
- spongy bone called diploe in flat bones
- bone marrow btw the tracbeculae
structure of short, irregular, and flat bones
- bone forming cells, laying dow the matrix
osteoblasts
- mature bone cells that occupy (lacunae) spaces that conform to their shape
- monitor and maintain bone matrix
osteocytes
- Cells that break down (resorb) bone matrix
- HCL(hydrochloric acid) for mineral salts
- lysosomal_ enzymes digest proteins
- lie at right angels tot he long axis of the bone and connect the blood and nerve supply of the periosteum to those in the central canals and the medullary cavity
perforating canals or Volkmann’s canal
- Trabeculae- Align along lines of stress
- No osteons
- Contain irregularly arranged lamellae , osteocytes , and canaliculi
- Capillaries in endosteum supply nutrients_
microscopic anatomy of spongy bone
- Osteogenic cells, osteoblasts , osteocytes, osteoclasts
- Osteoid—organic bone matrix secreted by osteoblasts
- ground substance (proteoglycans , glycoproteins)
- collagen fibers
- Provide tensile strength and flexibility
organic chemical composition of bone
- hydroxyapatites_(mineral salts)
- 65% of bone by mass
- Mainly calcium phosphate crystals
- Responsible for hardness and resistance to compression
chemical composition of bone: inorganic
______: ossification centers appear in the fibrous connective tissue membrane. Selected centrally located mesenchymal cells cluster and differentiate into _____, forming an ossification center
Step one (1) of intramembranous ossification, osteoblasts
_____: bone matrix (osteoid) is secreted within the fibrous membrane and calcifies. Osteoblasts begin to secrete osteoid, which is calcified within a few days. Trapped osteoblasts become _____.
Step two (2) of intramembranous ossification, osteocytes
_____: woven bone and periosteum form. Accumulating osteoid is laid down between ____ blood vessels in a random manner. The result is a network (instead of lamellae) of trabeculae called ____ bone. Vascularized mesenchyme condenses on the external face of the woven bone and becomes the ____.
Step three (3) of intramembranous ossification, embryonic, woven, periosteum
______: lamellar bone replaces woven bone, just deep to the periosteum. Red marrow appears. Trabeculae just deep to the periosteum thicken, and are later replaced with mature lamellar bone, forming ____ bone plates. Spongy bone (dipole), consisting of distinct _____, persists internally and its vascular tissue becomes ____ marrow.
Step four (4) of intramembranous ossification, compact, trabeculae, red
_____: a bone collar is laid down around the diaphysis of the hyaline cartilage model. In week __ everything except a clavicle is made. Osteoblasts of the newly converted periosteum secrete ___ against the hyaline cartilage diaphysis, encasing it in ___. This freshly formed layer of bone is called the ____ bone collar. Primary ossification center is in the center of the diaphysis.
Step one (1) of Endochondral ossification in a long bone, 9, osteoid, bone, periosteal
____: cartilage in the center of the diaphysis calcifies and then develops cavities. Still during development. As the bone collar forms, chondrocytes within the shaft hypertrophy (enlarge) and signal the surrounding cartilage matrix to calcify. Then, the ____ die and the matrix begins to deteriorate. This deterioration opens up ____, but they hyaline cartilage model is stabilized by the bone collar. Elsewhere, the cartilage remains healthy and continues to grow briskly, causing the cartilage model to ____.
Step two (2) of Endochondral ossification in a long bone, chondrocytes, cavities, elongate
the periosteal bud invades the internal cavities and spongy bone forms.
Step three (3) of Endochondral ossification in a long bone
the diaphysis elongates and a medullary cavity forms. As the primary ossification center enlarges, osteoclasts break down the newly formed spongy bone and open up a medullary cavity in the center of the diaphysis
Step four (4) of Endochondral ossification in a long bone
the epiphyses ossify. Durring childhood and adolescence. When secondary ossification is completed, hyaline cartilage remains in the epiphyseal plates and articular cartliages
Step five (5) of Endochondral ossification in a long bone
long bones lengthen entriedly by ________ growth of the epipyseal plate cartilage and its replacement by bone, and all bones grow in thickness by _______ growth
interstitial/ appositional
- uses hyaline cartilage models
- requires breakdown of hyaline cartilage prior to ossification
endochondral ossification
epiphseal plate cartilage organizes into4 important functional zones
- proliferation (growth):cartilage undergoes mitosis
- Hypertrophic: older cartilage cells enlarge
- Calcification: matrix becomes calcified,carilage cells die; matrix begins deteriorating
- ossification(osteogenic)- new bone formation is occuring
- occurs when bone is injured or added strength is needed
- requires a dieet rich inp protein; vitamins c,d, and A; calcium; phosphorus; magnesium; and manganese
bone deposit
- osteoclasts secrete
- lsosomal enzymes (digest organic matrix)
- acids (convert calcium salts into soluble forms)
- dissolved matrix is transcytosed across osteoclast, enters interstital fluid and then blood
one resorption
- hormonal mechanisms that maintain calcium homeostasis in the blood
- mechanical and gravitational forces
what controls the remodeling of bone
calcium is necessary for:
- Transmission of nerve impulses
- muscle contraction
- Blood cogaulation
- Secretion by glands and nerve cells
- enzyme activity
- Cell division
9-11 mg/100 ml
calcium homeostasis of blood
- falling blood Ca2+ levels
- parathyroid glands release PTH
- so PTH goes up
- osteoclasts degrade bone matrix and release Ca2+ into blood
balance to calcium homeostasis of blood
- high blood Ca2+ levels
- parafollicular cells of thyroid release calcitonin
- osteoblasts deposit calcium salts
- blood Ca2+ levels go down
hormonal control of blood Ca2+ when there are high blood Ca2+ levels
_____Law :A bone grows or remodels in response to forces or demands placed upon it
Wolff’s Law
observations supporting:
- Trabeculae form along lines of stress
- handedness(right or left handed) results in bone of one upper limb being thicker and stronger
- Curved bones are thickest where they are most likely to buckle
- Large, bony projections occur where heavy , active muscles attach
1.Position of bone ends after fracture:
- nondisplaced —ends retain normal position
- Displaced —ends out of normal alignment
2.Completeness of the break
- Complete —broken all the way through
- Incomplete —not broken all the way through
3.Orientation of the break to the long axis of the bone:
- Linear —parallel to long axis of the bone
- Transverse—perpendicular to long axis of the bone
4.Whether or not the bone ends penetrate the skin:
- Compound (open) —bone ends penetrate the skin
- Simple(closed) —bone ends do not penetrate the skin
classification of bone fractures
all fractures can be described in terms of :
- location
- external appearance
- nature of the break
common types of fractures
- comminuted-bone frag into3ormore pieces
- compression- bone crushed
- spiral- ragget break when twisting forces applied in sports
- epiphyseal- separates diaphysis along teh epiphyseal plate
- depressed- broken bone portion is pressed inward (skull fracture)
- greenstick- bone breaks incompletely where one side of shaft breaks and other side bends common in children
stages in the healing of a bone fracture
- a hemotoma forms
- fibrocartilaginous callus forms
- bony callus forms
- bone remodeling occurs
- calcium salts not deposited
- rickets(childhood disease) causes bowed legs and other bone deformities
- Cause: vitamin D deficiiency or insufficient dietary calcium
homeostatic imbalances :osteomalacia and rickets
- loss of bone mass- bone resportion outpaces deposit
- risk factors: lack of estrogen, calcium or vitamin d; petite body form; immobility; low levels of TSH; diabetes mellitus
osteoporosis
- excessive and haphazard bone formation and breakdown , usually in spine, pelvis, femur , or skull
- pagetic bone has very high ratio of spongy to compact bone and reduced mineralization
- Unknown cause (possibly viral)
- treatment includes calcitonin and biphosphonates
paget’s disease
- Embryonic skeleton ossifies predictably so fetal age easily determined from X rays or sonograms
- At birth, most long bones are well ossified (except epiphyses )
developmental aspects of bones
- Nearly all bones completely ossified by age 25
- Bone mass decreases with age beginning in 4th decade
- Rate of loss determined_ by genetics and environmental factors
- In old age, bone resorption predominates
developmental aspects of bones
