Skeletal tissues contain 3 cartilages
1. hyaline cartilages- provide support, flexibility, and resilience, most abundant type
2. elastic cartilages- similar to hyaline cartilages but contain elastic fibers
3. fibrocartilages- collagen fibers- have great tensile strength
cells secrete matrix against the external face of existing cartilage
- increases thickness and remodeling of all bones by osteoblasts and osteoclasts on bone surfaces
chondrocytes divide and secret new matrix, expanding cartilage from within.
- increases length of bones
skull, vertebral column and rib cage
bones of upper and lower limbs
Classifications of bones by shape
- Long bones- longer than they are wide (limbs bones)
- short bones- cube shaped (in wrist and ankle). Sesamoid bones (w/in tendons, i.e- patella)
- flat bones- thin, flat, slightly curved
- irregular bones- complicated shapes
Functions of Bones
- Storage- minerals (Ca2+ and phosphorus) and growth factors
- Blood cell formation (hematopoiesis) in marrow cavities
- Triglyceride (energy storage) in bone cavities
Features of bone markings
projections, depressions, and holes or openings that serve as:
- sites of attachment for muscles, ligaments, and tendons
- joint surfaces
- conduits for blood vessels and nerves
narrow, prominent ridge
large, blunt, irregular surface
narrow ridge of bone
small rounded projection
raised area above a condyle
sharp, slender projection
any bony prominence
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
cavity w/in a bone
shallow, basin-like depression
narrow, slitlike opening
round or oval opening through a bone
- outer fibrous layer
- inner osteogenic layer
cover spongy bone w/in
short irregular and flat bone
contains osteoblasts and osteoclasts
Red marrow cavities of adults
- trabecular cavities of the heads of the femur and humerus
- trabecular cavities of the diploe of flat bones
Red marrow cavities of newborn infants
medullary cavities and all spaces in spongy bone
small cavities that contain osteocytes
hairlike canals that connect lacunae to each other and the central canal
at right angles to the central canal
connects blood vessels and nerves of the periosteum and central canal
Central (Haversian) canal
contains blood vessels and nerves
weight-bearing; column-like matrix tubes
located in spongy bone.
align along lines of stress
no osteons; contain irregularly arranged lamellae, osteocytes and canaliculi
organic bone matrix secreted by osteoblasts
ground substance (proteoglycans, glycoproteins)
- membrane bone develops from fibrous membrane (no cartilage)
- forms flat bones
- type of ossification
- requires breakdown of hyaline cartilage prior to ossification
Describe intramembranous ossification process
1. ossification centers appear in the fibrous connective tissue membrane
2. bone matrix (osteoid) is secreted w/in firbrous membrane and calcifies
3. woven bone and periosteum form
4. lamellar bone replaces woven bone, just deep to the periosteum. Red marrow appears.
Describe Endochondral Ossification process
- bone collar forms around the hyaline cartilage model
- cartilage in the center of the diaphysis calcifies and then develops cavities
- the periosteal bud invades the internal cavities and spongy bones 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.
Epiphyseal plate cartilage organizes into 4 important functional zones.
- proliferation (growth)- cartilage undergoes mitosis
- hypertonic- increasing thickness, older cartilage cells in large
- calcification- matrix calcifies, cartilage cells die; matrix begins deteriorating, blood vessels invade the cavity
- ossification (osteogenic) new bone forms
Growth hormone stimulates...
epyphyseal plate activity
Thyroid hormone modulates...
activity of growth hormone
When does bone deposit (bone building) occur?
1. occurs where bone is injured or added strength is needed
Requires a diet rich in protein, vitamin C, D, and A; calcium; phosphorus magnesium; and manganese
Describe process of bone deposit (bone building)
Sites of new matrix deposit are revealed by the
- Osteoid seam- unmineralized band of matrix
- calcification front- the abrupt transition zone between the osteoid seam and older mineralized bone
Describe bone resorption (breaking down) process
- Osteoclasts secrete lysosomal enzymes (digestic organic matrix). Acids convert calcium salts into soluble forms
- Dissolved matrix is transcytosed across osteoclast, enters interstitual fluid and then blood
What controls continual remodeling of the bone?
calcium, phosphorus, mechanical and gravitational forces (body weight)
What is the importance of Calcium?
- transmission of nerve impulses
- muscle contraction
- blood coagulation
- secretion of glands and nerve cells
- cell division
controlled by parathyroid hormone (PTH)
- when blood calcium levels decreases
- PTH stimulates osteoclasts to degrade bone matrix and release Calcium.
- Blood calcium levels increases to normalization
Secondarily controlled by calcitonin
- when blood calcium levels increases
- parafollicular cells of thyroid release calcitonin
- osteoblasts deposit calcium salts
- blood calcium levels decreases to normalization
a bone grows and remodels in response to forces or demands placed upon it.
What are the 4 stages of healing of a bone fracture?
- hematoma forms
- fibrocartilages callus forms
- bony callus formation
- bone remodeling
excessive and haphazard (disorganized) bone formation and breakdown, usually in spine, pelvis femur or skull (not controlled)