Chapter 6 Flashcards
Skeletal Cartilages
- Hyaline Cartilages
- Elastic Cartilages
- Fibrocartilages
Skeletal Cartilages: Hyaline cartilages
- Provide support, flexibility, and resilience
- Most abundant type
Skeletal Cartilages: Elastic cartilages
-Similar to hyaline cartilages, but contain elastic fibers
Skeletal Cartilages: Fibrocartilages
-Collagen fibers- have great tensile strength
costal cartilage
in ribs
pubic symphysis meniscus
padlike cartilage in knee joint
Growth of cartilage
- Appositional ( grows from outside-width)
- Cells secrete matrix against the external face of existing cartilage
- Interstitial (grows from inside-length)
- Chondrocytes divide and secrete new matrix, expanding cartilage from within
- Calcification of cartilage occurs during:
- normal bone growth
- old age
- CALCIFIED CARTILAGE IS NOT BONE
Classification of bones by shape
Long bones:
Longer than they are wide
Short bones:
- Cube-shaped bones (in wrist and ankle)
- Sesamoid bones (within tendons, e.g., patella)
Flat bones
*Thin, flat, slightly curved (skull, scapula, sternum)
Irregular bones
*Complicated shapes (vertebrae, pelvis)
Slide 6 in bones PPW
Functions of bones
Support-
for the body and soft organs
Protection-
for brain, spinal cord, and vital organs
Movement-
Levers for muscle action
Storage-
Minerals (calcium & phosphorus) and growth factors
Blood cell formation (hematopoiesis)-
in marrow cavities
Triglyceride (energy) storage- in bone cavities
Bone markings
Bulges, depressions, and holes serve as:
- sites of attachment for muscles, ligaments, and tendons
- Joint surfaces
- Conduits for blood vessels and nerves
- helps you understand many bones
- Surface features of the skull
- surface features of the humerus
- surface features of the femur
- surface features of the pelvis
PPW Chapter 6 slide 9
slide 10
Bone markings: projections
- Sites of muscle and ligament attachment
- Tuberosity—rounded projection
- Crest—narrow, prominent ridge
- Trochanter—large, blunt, irregular surface
- Line—narrow ridge of bone
- Tubercle—small rounded projection
- Epicondyle—raised area above a condyle
- Spine—sharp, slender projection
- Process—any bony prominence
Bone markings: projections
-Projections that help to form joints
Head:
Bony expansion carried on a narrow neck
Facet:
Smooth, nearly flat articular surface
Condyle:
Rounded articular projection
Ramus:
Armlike bar
Bone markings: Depressions & openings
Meatus:
*Canal-like passageway
Sinus:
*Cavity within a bone
Fossa:
*Shallow, basinlike depression
Groove (bicipital):
*Furrow
Fissure:
*Narrow, slitlike opening
Foramen:
*Round or oval opening through a bone
Bone Textures
Compact bone (10 years) *Dense outer layer
Spongy (cancellous) bone (3-4 years)
- Honeycomb of trabeculae
- More porous like a sponge
The structure of a long bone
Long bones transmit forces easily and have a rich blood supply. Nutrient artery and vein through nutrient foramen. Periosteum: extensive network of blood vessels, lymphatic vessels & sensory nerves.
slide 15
Membranes of bone
Periosteum :
-outer fibrous layer
-inner osteogenic layer
*Osteoblasts (bone-
forming cells)
*Osteoclasts (bone- destroying cells) *Osteogenic cells (stem cells)
Membranes of bone
Endosteum:
-delicate membrane on internal surfaces of bone
-also contains osteoblasts and osteoclasts
Structure of short, irregular, and flat bones
- Periosteum-covered compact bone on the outside
- Endosteum-covered spongy bone within
- Spongy bone called diploë in flat bones
- Bone marrow between the trabeculae
Location of Hematopoietic Tissue (red marrow)
- Red marrow cavities of adults
- Trabecular cavities of the heads of the femur and humerus
- Trabecular cavities of the diploë of flat bones
Microscopic Anatomy of Bone
Cells of bones:
Osteogenic (osteoprogenitor) cells-
*Stem cells in periosteum and endosteum that give rise to osteoblasts
Osteoblasts-
*Bone-forming cells, secrete bone matrix
Osteocytes-
*Mature bone cells, monitor/maintain matrix
Osteoclasts-
*Cells that break down (resorb) bone matrix
Microscopic Anatomy of Bone: Compact Bone
Haversian system, or osteon—structural unit:
Lamellae –
*concentric rings
* Weight-bearing
*Column-like matrix
tubes
Central (Haversian) canal-
*Contains blood
vessels and nerves
-Perforating (Volkmann’s) canals:
*At right angles to the
central canal
*Connects blood
vessels and nerves of
the periosteum and
central canal
-Lacunae:
*small cavities that contain
osteocytes
-Canaliculi:
*hairlike canals that
connect lacunae to each
other and the central
canal
Compact bone anatomy
-Canaliculi:
*hairlike canals that
connect lacunae to each
other and the central
canal
Compact bone anatomy
Lacunae:
*small cavities that contain
osteocytes
Compact bone anatomy
-Perforating (Volkmann’s) canals:
*At right angles to the
central canal
*Connects blood
vessels and nerves of
the periosteum and
central canal
Spongy bone
Trabeculae:
-align along lines of stress
- no osteons
- contain irregularly arranged lamellae, osteocytes, and canaliculi
- capillaries in endosteum supply nutrients
In bone, collagen is found in the
lamellae
Adjacent osteocytes communicate via gap junctions found within
canaliculi
Chemical composition of bone: organic
-Osteogenic cells, osteoblasts, osteocytes, osteoclasts
Osteoid—organic bone matrix secreted by osteoblasts
Ground substance (proteoglycans, glycoproteins)
Collagen fibers:
Provide tensile strength and flexibility
Chemical composition of bone: inorganic
Hydroxyapatites (mineral salts):
*65% of bone by mass
*Mainly calcium phosphate crystals *Responsible for hardness and resistance to compression
Bone development: osteogenesis
-Osteogenesis (ossification): bone tissue formation
Stages:
1. Initial formation in embryo and fetus
- Growth from infancy through adolescence
- Remodeling of bone throughout life
- Repair of fractures
2 types of ossification
- Intramembranous ossification:
* membrane bone develops from fibrous membrane
*forms flat bones, e.g. clavicles and cranial bones
- Endochondral ossification
* Cartilage (endochondral) bone forms by replacing hyaline cartilage*forms most of the rest of the skeleton
Intramembranous Ossification
- development of the ossification center.
* Ossification centers appear in the fibrous connective tissue membrane. Selected centrally located mesenchymal cells cluster and differentiate into osteoblasts, forming an ossification center that produces the first trabeculae of spongy bone. - bone matrix (osteoid) secreted & calcified
* Osteoid is secreted within the fibrous membrane and calcified. Osteoblasts begin to secrete osteoid, which calcified in a few days. trapped osteoblasts become osteocytes - Trabeculae of woven bone and periosteum form
- Bone collar of compact bone forms and red marrow appears
Endochondral ossification
- Uses hyaline cartilage models
- Requires breakdown of hyaline cartilage prior to ossification
- Forms all bones below skull except for clavicles
At week 9 (babies)
- bone collar forms around hyaline cartilage model
- cartilage in the center of the diaphysis calcifies and then develops cavities
- the periosteal bud invades the internal cavities and spongy bone begins to form
- the diaphysis elongates and a medullary cavity forms as ossification continues. secondary ossification centers appear in the epiphyses in preparation for stage 5
- the epiphyses ossify. when completed, hyaline cartilage remains only in the epiphyseal plates and articular cartilages.
Post natal bone growth
- Interstitial growth:
* increased length of long bones - Appositional growth:
* increased thickness and remodeling of all bones by osteoblasts and osteoclasts on bone surfaces
*Bone matrix secreted under periosteum
Organization of cartilage within epiphyseal plate of growing long bones
-resting zone- small, inactive cartilage cells
- Proliferation zone:
Chondroblasts quickly divide and push the epiphysis away from the diaphysis, lengthening the bone - Hypertrophic zone:
older chondrocytes enlarge and signal the surrounding matrix to calcify - Calcification zone:
matrix becomes calcified; chondrocytes die. leaving behind trabeculae-shaped calcified cartilage. THIS IS NOT YET BONE - Ossification zone:
osteoclasts digest the calcified cartilage, and osteoblasts replace it with actual bone tissue in the shape of the calcified cartilage-resulting in bone trabeculae
Spongy bone is made up of small, flat pieces of bone called
trabeculae
Which structure plays an important role in widening long bones?
periosteum
depressions on bone include
fossae
A group of concentric rings of bone matrix, comprising the functional unit of long bones, is called a(n)
osteon (the chief structural unit of compact (cortical) bone, consisting of concentric bone layers called lamellae, which surround a long hollow passageway, the Haversian canal)
Hormonal regulation of bone growth
- Growth hormone stimulates epiphyseal plate activity (from pituitary gland)
- Thyroid hormone modulates activity of growth hormone
-Testosterone and estrogens (at puberty)
*Promote adolescent
growth spurts
*End growth by inducing
epiphyseal plate closure
(18 y/o females; 21 y/o for
males)
Hormonal control of blood Ca 2+
Primarily controlled by parathyroid hormone (PTH):
decrease in Blood Ca2+ levels -> Parathyroid glands release PTH-> PTH stimulates osteoclasts to degrade bone matrix and release Ca2+ -> increase in Blood Ca2+ levels
slide 47
Control of remodeling
What controls continual remodeling of bone?
- Hormonal mechanisms that maintain calcium homeostasis in the blood
- Mechanical and gravitational forces
* Wolff’s Law
response to mechanical stress
- Wolff’s law: A bone grows or remodels in response to forces or demands placed upon it
- Observations supporting Wolff’s law:
- 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
- Trabeculae form along lines of stress
- Large, bony projections occur where heavy, active muscles attach
- Increased stress or decreased stress ie astronauts
Fracture Classification
- Displaced or nondisplaced
- Open or closed
- Comminuted – bone fragments
- Spiral - excessive twisting force
- Compression – common in osteoporosis
- Depressed
- Greenstick
Stages in the healing of a bone fracture
- Hematoma (mass of clotted blood) forms
*Site becomes swollen,
painful, and inflamed - Fibrocartilaginous callus
- Fibroblasts secrete collagen to connect bone ends
- Bony callus formation
- Firm union in 8 weeks
- Bone remodeling
- In response to mechanical stresses
Homeostatic imbalances
- Osteoporosis (osteopenia):
- Loss of bone mass—bone resorption outpaces deposit
- Spongy bone of spine and neck of femur become most susceptible to fracture
Risk factors:
*Lack of estrogen, calcium or vitamin D; petite body form; immobility; low levels of TSH; diabetes mellitus
*At risk: petite white post menopausal female who is a nonexercising smoker
Osteoporosis: treatment and prevention
Calcium, vitamin D, and fluoride supplements
New research:
* Increase Weight-bearing exercise throughout life
- Hormone (estrogen) replacement therapy (HRT) slows bone loss
- Some drugs (Fosamax, SERMs, statins) increase bone mineral density
