Lecture 7Osseous Tissue
Bio-11
JPHubbard
• Dynamic and ever-changing throughout life• Skeleton composed of different tissues
– cartilage, bone tissue, epithelium, nerve, blood forming tissue, adipose, and dense connective tissue
Functions:
• Support • Movement and leverage
• Protection
• Storage of minerals (Ca especially) and fat
• Blood cell production
Types of Bones – ShapeKnow some examples:
• Long Bone• Flat Bone• Irregular Bone• Short Bone• Two additional types – vary with individuals:
– Sutural Bones– Sesamoid Bone
Gross Anatomy of Long Bone• _______________ tough connective tissue layer
covering boneattachment of tendons and ligaments
blood vessels in periosteum• ______________- ends
spongy bonecompact bone, articular cartilage
• ______________- middlecompact bonemedullary cavity- contains yellow marrow (fat)lined with endosteum (squamous epithelium)
Bone = Osseous tissue • a type of connective tissue – What characterizes connective tissue?
– Cells? – Vascular– matrix
What differentiates bone from other connective tissues?
Bone Cells
• _____________ – build bone, lay down matrix• _____________ – mature bone cells• Osteoprogenetor – mesenchyme cells which
differentiate into osteoblasts, largely inner layer of periosteum
• _________________ – large cells, destroy bone• Activity of osteoblasts, osteoclasts impacted by
hormones from thyroid/parathyroid
Matrix
• Collagen fibers –– Protein– like reinforcing rods – What would be the effect of lack of collagen?
• Minerals: provide rigidity – Calcium salts
Bone Micro-Anatomy – Osseous Tissue• Two types:
– 1. Compact bone• Osteon – Basic organizational unit• Diaphysis long bone, outer layers at
epiphysis and of flat bone– 2. Spongy Bone – no osteons
• Trabeculae provide bracing effect• Red Marrow produces blood cells• Ends of long bones + inside flat bones
Compact Bone – Osteon basic unit
• Central canal: blood vessels at center of osteon
• Lamella: Concentric layers of matrix
• Lacunae: contain osteocytes between layers of lamella
• Canaliculi: canals which connect lacunae
Trabeculae of Spongy Bone• oriented along lines of stress - Latticework• Harbor and protect red marrow ( blood cells
develop)
No true Osteons.
Bone Development Prenatal : (embryonic and fetal) skeleton is mostly cartilaginous
Ossification – the process of mineralization of tissue (hyaline cartilage, fibrocartilage) resulting in formation of bone
Cartilage cells and then osteoblasts start to deposit minerals
Bone Formation – 2 ways:1) Intramembrannous ossification – Flat Bones - bone
formed between sheets of connective tissue
2) Endochondral ossification –Long Bones - formed from hayaline cartilage model– increase in length until puberty at epiphyseal
plate– increase in diameter due to activity of cells
under periosteum– Control from growth hormone (GH) + other
endocrine hormones
Rickets and Osteomalacia• Disorders resulting in abnormal/poor ossification• Rickets:
– Vitamin D deficiency– Bowed limbs– Pain– Limbs easily broken
• Osteomalacia– Failure of adult bone to ossify– hip fractures are common
Growth hormone regulates skeletal growthstimulates cell division in epiphyseal disksin long bones
Growth stops when epiphyseal disks are converted to bone
When excess growth hormone is produced inchildhoodgigantism
In adulthood- acromegaly. Bones can’t growbut soft tissue can
Fracture & Repair of Bone• Healing is faster in bone than in cartilage due
to lack of blood vessels in cartilage• Healing of bone is still slow process due to
vessel damage• Clinical treatment
– closed reduction = restore pieces to normal position by manipulation
– open reduction = surgery
Bone Repair – Similar to Development
6-8 hours Hematoma forms
~ 3 weeks Fibrocartilaginous callus develops
~3-4 months Bony callus and spongy bone formed
Future Osteoblasts form compact bone
Bone Remodeling• Continuous Process
– distal femur is fully remodeled every 4 months• Osteoblast build - stimulated by
– Weight bearing activity– Blood Ca levels via endocrine hormones
(calcitonin stimulates)– Numbers increased by estrogen/testosterone
• Osteoclasts– Stimulated by dropping blood Ca level via
parathyroid hormone– Calcitonin inhibits
Small changes in blood levels of Ca+2 can be deadly:(plasma level maintained 9-11mg/100mL)
cardiac arrest if too high
respiratory arrest if too low
This is an example of a _____________ feedback loop.
Aging & Bone Tissue• Bone is being built through adolescence, holds its own in
young adults, but is gradually lost in aged.• Demineralization = loss of minerals
– very rapid in women 40-45 as estrogens levels decrease
– in males, begins after age 60• Decrease in protein synthesis
– decrease in growth hormone– decrease in collagen production which gives bone its
tensile strength– bone becomes brittle & susceptible to fracture
Osteoporosis• Loss in bone density• Affected by age, sex, race, nutrition, exercise• Particular problem for women after menopause
due to decreased estrogen• Diet factors with negative impact: alcohol,
caffeine, certain antibiotics and other drugs• Positive: Exercise increases bone mass, Fosamax,
vitamin D, hormone replacement therapy, calcium fluoride
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