Chapter 6 Bones and Skeletal Tissues
Facet
Projection that helps form joints Smooth, nearly flat articular surface
Meatus
Canal like passageway
greenstick fracture
bone breaks incompletely where only one side breaks and the other bends, and this is common in children where bones are more flexible having more organic matrix than adults
Trabeculae
Carefully positioned along stress lines to reduce bone stress
How long does it take for a bone to heal?
- 6-8 weeks for a simple fracture -6-8 weeks for small to medium sized bones in young adults -Weight bearing bones and fracturs in elderly take longer
Treatment of osteoporosis
-Calcium and Vitamin D supplements -Weight bearing exercise -Medication such as HRT, Biphosphonates (alendronate), SERMS (raloxifene)
step 4 of Endochondral ossification
-Diaphysis enlongates and a medullary cavity is formed -secondary ossification occurs in the epiphysis
Step 5 of Endochondral ossification
-Epiphysis ossifies -Hyaline cartilage remains in the epiphyseal plate and in articular cartilage
Consequences of abnormal blood calcium
-Increase, hyperexcitability -Decrease, nonresponsiveness; inability to function - Sustained hypercalcemia leads to inhibiting organ functioning
What causes osteomalacia and rickets?
-Insufficient dietary calcium -insufficient dietary vitamin D
Step 2 of Intramembranous ossification
-Osteoblasts begin to secrete osteoid, which calcifies in a few days -Trapped osteoblasts become osteocytes
Risk factors for osteoporosis
-Petite stature -insufficient exercise -poor dietary calcium -abnormal vitamin d receptors -smoking -endocrine disorders such as diabetes mellitus -immobility -steroid use
What are the negative effects of HRT?
-Slows bone deteriation but does not reverse it -Increase risk of heart attack, stroke, and breast cancer
Step 4 of Intramembranous ossification
-Trabeculae thickens below the periosteum -Mature lamellar bone replaces wovem bone forming compact bone plates -Spongy bone consisting of distinct trabeculae exists internally where its vascular tissue becomes red marrow
Step 3 of Intramembranous ossification
-Woven bone forms: Network of trabeculae due to accumulating osteoid between embryonic blood vessels -Periosteum forms: vascularized mesenchyme condenses on the external face of woven bone
How much bone mass is recycled each week?
5-7%
Inorganic components
65% of bone mass consisting of hydroxyapatites or mineral salts/calcium phosphates Crystalize around collagen which accounts for hardness of bone resisting compression
Blood calcium level must be maintained within ________-.
9-11 mg/dL blood
The bone stores ______ of body calcium.
99%
fracture
A break in a bone
Rickets
A disorder similar to osteomalacia that occurs in growing bones of children -more severe than osteomalacia due to growth -bowed legs, deformity of pelvis, skull, and ribs
Osteoporosis
A medical condition in which the bones become brittle and fragile from loss of tissue due to more bone resorption than bone deposit
Step 2 of Endochondral ossification
Cartilage in the center of diaphysis calcifies and develops cavities
Perforating canals
Also known as Volkmann's canals; run perpindicular to the central canal and connects the blood and nerve supply of the periosteum to those in the central canal and the medullary cavity.
Osteon
Also known as the Haversian system; structural unit of compact bone which consists of a group of hollow tubes one inside the other
Spongy Bone
Appears poorly organized compared to compact bone; No Osteons, Contains irregularly arranged lamellae; Canaliculi connect osteocytes; nutrients reach osteocytes from capillaries in endosteum covering trabeculae
Why is bone considered an organ?
Because it contains multiple tissue types
Hematopoiesis
Blood cell formation
Sacrificial bonds
Bonds located in or between collagen molecules which break on impact dissipating energy to resist fracture
Step 1 of Endochondral ossification
Bone collar forms around the diaphysis of the hyaline cartilage model
Osteogenesis
Bone formation
Comminuted fracture
Bone fragments into three or more pieces and is common in the aged where bones are more brittle
Endochondral ossification
Bone from hyaline cartilage
Ossification
Bone remodeling or replacing tissue with bone
Osteoclast
Bone resorbing cell or bone destroying cells
What is the endosteum made of?
CT, osteoblast, osteoclasts
Sinus
Cavity within a bone, filled with air and lined with mucous membrane
medullary cavity
Cavity within the shaft of the long bones filled with bone marrow
Endosteum
Connective tissue membrane covering internal bone surfaces specifically trabeculae and canals through compact bone
What two processes constitute bone remodeling?
Deposit and resorption
Periostium
Double-layered connective tissue that covers and nourishes the bone except on joints; provides anchor for ligaments and tendons
Why is bone durable and strong but not brittle?
Due to its precise combination of organic and inorganic matrix elements
Bone lining cells
Flat cells found on bone surfaces where bone remodeling is not going on which are believed to help maintain the bone matrix
Groove
For passage of blood vessels and nerves Furrow
Notch
For passage of blood vessels and nerves Indentation at the edge of a structure
Fissure
For passage of blood vessels and nerves Narrow, slitlike opening
Foramen
For passage of blood vessels and nerves Round or oval opening through a bone
Compact bone
Hard, dense bone tissue that is beneath the outer membrane of a bone
Haversian (central) canal
Hollow tube through the middle of an osteon containing blood vessels and nerves
Remodeling and repair of bone is part of ________.
Homeostasis
What regulates bone growth?
Hormones
Red bone marrow
Includes stem cells that can produce red blood cells, white blood cells, or platelets
Interstitial lamellae
Incomplete lamellae between osteons; either fill the gaps between forming osteons or are remnants of osteons that have been cut through by bone remodeling.
Lamella
Individual tubes that make up the osteon
What does the skeleton in the human embyro consist of before week 8?
It consists of fibrous membrane and hyaline cartilage. After week 8, bone tissue develops
Why is the role of calcium in blood important for homeostasis?
It is needed: - to transmit nerve impulses - in muscle contraction - in blood coagulation - in cell division
What makes up the organic components of bone?
Its cells and osteoid (35% bone mass) Reservoir for caclium and phosphate which is deposited and withdrawn as need; Growth factors
What is the periosteum made of?
Its outer fibrous layer consists of dense irregular CT and its inner layer consists of osteoblasts and osteoclasts
Circumferential lamellae
Lamellae adjacent to periosteum and endosteum
Osteoblast
Matrix-synthesizing cell responsible for bone growth or bone forming cells
Osteocytes
Mature bone cell that monitors and maintains the mineralized bone matrix
How does bones respond to stress?
Mechanical stress and gravity maintains bone strength -Thickens bones -Bones develop heavier prominences -Rearranges trabeculae
Osteogenic cell
Mitotic stem cells in the periostium and endosteum which can develop into osteoblasts or bone lining cells, or persist as osteogenic cells.
Osteoid
Organic part of the bone matrix which makes up 1/3 of matrix; includes ground substance and collagen fibers which both are made and secreted by osteoblasts. Contributes to bone strength, structure, and its flexibility to resist stretch and twisting
What are the 5 major cell types that make up bone tissue?
Osteogenic cells, osteoblasts, osteocytes, bone lining cells, osteoclasts
Describe homeostatic imbalance in blood calcium
Parathyroid gland releases PTH (parathyroid hormone) which stimulates osteoclasts to resorb bone releasing calcium into the blood stream. When calcium levels in the blood rises, the stimulus for PTH release ends.
Step 3 of Endochondral ossification
Periosteal bud invades the internal cavities and spongy bone forms
What are the three membranes in a bone structure?
Periosteum, Endosteum, collagen fibers
Condyle
Projection that helps form joints Rounded articular projection
Osteoporosis is most common in which group of people?
Postmenopausel women because estrogen restrains osteoclasts and promotes bone deposition
Ramus
Projection that helps form joints Armlike bar of bone
Head
Projection that helps form joints Bony expansion carried on a narrow neck
Ground subtance
Proteoglycans and glycoproteins
Epiphyseal line
Remnant of epiphyseal plate between the diaphysis and epiphysis Contains hyaline cartilage disc that grows in children to increase bone length and overal height
Step 1 of Intramembranous ossification
Selected centrally located mesenchymal cells cluster and differentiate into osteoblasts, forming an ossification center that produces the first trabeculae of spongy bone
Fossa
Shallow, basinlike depression in a bone, often serving as an articular surface
Process
Site of muscle/ligament attachement Any bony prominence
Tuberosity
Site of muscle/ligament attachement Large rounded projection; may be roughened
Crest
Site of muscle/ligament attachement Narrow ridge of bone; usually prominent
Epicondyle
Site of muscle/ligament attachement Raised area on or above a condyle
Spine
Site of muscle/ligament attachement Sharp, slender, often pointed projection
Tubercle
Site of muscle/ligament attachement Small rounded projection or process
Trochanter
Site of muscle/ligament attachement Very large, irregularly shaped process found on the femur
Lacunae
Small cavities in bone that contain osteocytes
What hormones contribute to bone growth in puberty?
Testerone and estrogen
bone resorption
The process whereby osteoclasts breakdown bone matrix
How do long bones increase in length?
Through interstitial growth of the epiphyseal plate cartilage and its replacement by bone
What hormone regulates bone growth in infants and children?
Thyroid hormone
Canaliculi
Tiny canals that connect lacunae and the central canal by linking all osteocytes in the osteon.
Paget's disease
Treatments include calcotonin and biphosphonates such as alendronate
Paget's disease
abnormally high ratio of spongy tissue to compact bone
How does long bone increase in width?
appositional growth and remodeling
why is bone dynamic?
because it continually being formed and resorbed influence by hormonal changes, physical activity, diet, etc.
The addition of minerals and collagen fibers to bone by osteoblast is called ________.
bone deposit
Paget's disease
bone deposit and bone resorption are not occuring at the same rate and reduced mineralization of bone
epiphysis
bone ends -outer compact bone/inner spony bone -joint surface covered with articular cartilage
Compression fracture
bone is crushed and is common in porous bones subjected to extreme trauma such as a fall
The process whereby osteoclasts breakdown bone matrix is called ____________.
bone resorption
Closed reduction
bones manipulated into position with surgery usually using hand
Depressed fracture
broken bone portion is pressed inward and is a typical skull fracture
Periosteal bud
contains a nutrient artery and vein, lymphatic vessels, nerve fibers, red marrow elements, osteogenic cells, and osteoclasts
Collagen fibers
contribute to flexibility and tensile strength
dwarfism
deficit of growth or thyroid hormone leading the short stature
Paget's disease
deformity and pain increase with time
Epiphyseal fracture
epiphysis separates from the diaphysis along the epiphyseal plate and tends to occur where cartilage cells are dying and calcification of the matrix is occuring
In young healthy adults bone mass is constant but not static because the rate of deposit and resorption are essentially __________.
equal
gigantism
excessive growth hormone in children leading to excessive height
Intramembranous ossification
formation of flat bones such as the cranial bones and the clavicles from fibrous membrane
Epiphyseal plate closure
fushion of epiphysis and diaphysis ending growth in bone length induced by testerone/estrogen
Interstitial growth
growth from inside
appositional growth
growth from outside
Bone remodeling is controlled by ______ and ________.
mechanical force, hormones
Paget's disease
often found first on x-rays done for unrelated reasons
Paget's disease
often localized to spine, pelvis, femur, or skull
Paget's disease
patchy weakness of bone
immobilization
preventing movement of fracture to allow healing by cast or traction
Spiral fracture
ragged break occurs when excessive twisting forces are applied to the bone and is a common sports fracture
Reduction
realignment of broken bones
Bone Remodeling
simultaneous bone depostion and resorption which maintains appropriate proportions between diaphysis and epiphysis
Osteomalacia
softening of the bone due to: -bones are inadequately mineralized -calcium salts not deposited -symptom includes pain with weight bearing
open reduction
surgical realignment of bones with pins or wires
Paget's disease
the cause is unknown
Diaphysis
tubular shaft of long bone containing a thick outer layer (compact bone) and medullary cavity where yellow marrow exists in adults
Metaphysis
where the diaphysis and epiphysis meet