Bone Tissue

Quick Review for Quiz over Bone Tissue/Structure  Covers only pgs 1-2 of notes  5 major functions  4 classifications & examples of each  7 parts of long bone  2 kinds of marrow  Bone diagram – will be a similar diagram on quiz but not the exact one! So really look at the parts.

Bone Tissue Pages 3&4 of notes will be on a WS

Composition of bone tissue  Bone tissue is composed of 2 types of tissues –Organic –Inorganic

Organic portion: 35% of mass  The organic portion consists of the bone cells and the organic matrix –The Bone cells are the: Osteocytes Osteoblasts Osteoclasts FYI: There are also osteoprogenitor cells that are the precursers to blasts & cytes. They are derived from mesenchyme & found on all bone surfaces.

Blasts, clasts & Cytes

Organic portion  The Organic Matrix aka. Osteoid –is produced by the osteoblasts Analogy: The organic matrix is the portion that is deposited first as the “grillwork” or framework of the bone during the process of OSTEOGENESIS It consists of ground substance and collagen fibers produced by CT cells Its function is to provide the bone with tensile strength and resilience – in other words, to make the bone a little flexible Review: ground substance, collagen fibers & EC matrix functions!!

Inorganic matrix: 65% of mass  The inorganic matrix consists of inorganic salt compounds mainly: –Calcium & phosphorus salt compounds  Its function is to give Strength to the bone  Analogy: It is formed during OSTEOGENESIS by the process of Mineralization –The inorganic matrix minerals are deposited into the organic matrix “grillwork” –The enzyme alkaline phosphatase mediates this process

Two types of bone tissue Know slides, locations, functions

Compact bone tissue (cbt)  Arranged in OSTEONS aka Haversian system  Contains a series of openings that permit exchange of materials between osteocytes (& other bone cells) and the blood.  Location: look at diagrams

Osteon diagram – cross section

osteocytes  Lacunae, osteocytes, & canaliculi

Osteon diagram – sagittal section

Cancellous (spongy) bone tissue  Main structures are the trabeculae which are needlelike structures of minerals that are arranged along stress lines to provide strength  Materials are exchanged by diffusion since there are NO canals for passage  Location: ends of long bones & middle of flat, short, and irregular bones

Bone marrow  Aka myeloid tissue  Yellow bone marrow –Fat storage –Found in medullary canal of long bones  Red bone marrow –Found in spongy bone (ends of long bones, flat bones, irregular bones) –Hematopoiesis (formation of all blood cells)

Types of growth  Longitudinal growth – bone growth in length at epiphyseal plates (till plates ossify)  Appositional growth – bone growth in diameter (throughout life) –Known as remodeling  These 2 types work together to make the bones long enough & strong enough

Regulation of bone growth  Bone is a dynamic and active tissue. They are constantly being remodeled according to the activities that we do.  Main factor = Ca levels in blood  Ca imp for bone strength but also for nervous & muscular system to work correctly!!!

Regulation by hormonal feedback  Purpose: to maintain optimal ionic calcium levels in blood –This is your body’s TOP priority!!!  A main factor that affects what our bone tissue does is our blood calcium level –Optimum blood Ca 2+ level = 9-11 mg/100 ml of blood –Calcium ions are VERY important for muscle & nervous function – our body cares more about this level than it does our bone strength!!

Regulation by hormonal feedback  PTH (parathyroid gland) – activated when Ca levels in blood are too low –(hypocalcemia) - promotes calcium reabsorption –Calcium will go from bone to blood  Calcitonin (thyroid gland) activated when Ca levels in blood are too high –(hypercalcemia) - promotes calcium deposition –Calcium will go from blood to bone

Regulation by mechanical stress  Purpose: keep bones strong –This is the secondary purpose  Wolff’s law states that bones will grow according to the stresses placed upon them –So activities that compress bones and pull on muscles which pull on bones can make bones stronger

How they work together to regulate  PTH & calcitonin (hormones) determine WHEN the remodeling will occur –Primary purpose = Ca 2+ regulation in blood  The Mechanical stresses determine WHERE the remodeling will occur –Secondary purpose = where will the calcium ions be deposited or reabsorbed from

Fractures & Disorders This section of info will be part of a lab practical quiz along with the tissue slides & functions from earlier in the notes

Instructions Construct a chart or other type of graphic organizer for the 9 types of fractures You will also need to be able to identify the X-rays or pictures of each. See Lab practical slide study on webpage for quiz review.

Common types of fractures  1. Comminuted –Bone breaks into many fragments –Common in aged whose bones are more brittle (contain less organic matrix)

Common types of fractures  2. Compression –Bone is crushed –Common on osteoporotic bones (or bones that are porous for other reasons)

Common types of fractures  3. Depressed –Broken bone portion is pressed inward –Typical of skull fracture

Common types of fractures  4. Impacted –Broken bone ends are forced into each other –Commonly occurs when one attempts to break a fall with outstretched arms –Or when one jumps off something too high

Impacted

Common types of fractures  5. Spiral –Ragged break occurs when excessive twisting forces are applied to a bone –Common sports fracture

Spiral fractures

Spiral fracture

Common types of fractures  6. Greenstick –Bone breaks incompletely, much in the way a green twig breaks –Common in children whose bones are more flexible (more organic matrix present)

7. Simple fracture  Bone does not protrude through skin

8. Compound Fractures  Bone protrudes through skin

9. Epiphyseal fracture  Bone shears off at growth plate  Can cause problems with early ossification at location of break

Example:Clavicle fracture

Example: Fracture

Example: dislocation

Disorders

Osteoporosis  Define: –reabsorption outpaces deposition –chemical composition remains the same BUT less total bone mass –SO bones become more porous & lighter –Which leads to fractures & deformities from body weight  Who is affected? –Mainly: Aged, post-menopausal women

osteoporosis  Contributing factors –Decreased estrogen –Decreased calcium & protein –Vitamin D metabolic disorders –Hormone conditions –Insufficient exercise –Immobility  Treatments –Replace what is missing –Medication for metabolic disorders

osteoporosis

Osteomalacia (rickets)  Define: –Chemical composition is abnormal (% are not right) –Increase in organic matrix – decrease in inorganic matrix –Indequate mineralization so bones are too soft –Lack of calcium deposition  Who is affected? –More severe effects in children since they are still growingbut primarily a nutritional disorder

osteomalacia  Contributing factors: –Vitamin D &/or calcium deficiency –Poor nutrition  Treatments: –Supplementation –Sunlight: think about why Vitamin D deficiency would lead to this disorder!

osteomalacia

Other disorders – add to notes  Osteomyolitis: inflammation of bone and muscle  Gigantism: excess of growth hormone before epiphyseal plates have ossified  Acromegaly: excess of growth hormone after epiphyseal plates have ossified  Dwarfism: deficit of growth hormone as well as other factors  Achondroplasia: most common form of dwarfism– autosomal dominant but can be from mutation

gigantism  Robert Wadlow  Lots of internal health problems including joint problems

acromegaly  Epiphyseal plates are sealed so bones can only grow in diameter/thickness

achondroplasia  Disproportionate dwarfism  Normal torso & head  Short arms & legs

Hypopituitary dwarfism  More proportionate dwarfism