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
Appositional Growth
(from outside)
cells secrete matrix against the external face of existing cartilage
- increases thickness and remodeling of all bones by osteoblasts
and osteoclasts on bone surfaces
Interstitial Growth
chondrocytes divide and secret new matrix, expanding cartilage from within.
- increases length of bones
Axial skeleton
skull, vertebral column and rib cage
Appendicular skeleton
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
Support Protection Movement 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
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
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
Meatus
canal-like passageway
Sinus
cavity w/in a bone
Fossa
shallow, basin-like depression
Groove
furrow
Fissure
narrow, slitlike opening
Foramen
round or oval opening through a bone
Periosteum
outer fibrous layer inner osteogenic layer
Osteoblasts
bone-forming cells
Osteoclasts
bone-destroying cells
Osteogenic cells
stem cells
Endosteum
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
lacunae
small cavities that contain osteocytes
Canaliculi
hairlike canals that connect lacunae to each other and the central canal
Volkmann's canals
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
Lamellae
weight-bearing; column-like matrix tubes
Trabeculae
located in spongy bone.
align along lines of stress
no osteons; contain irregularly arranged lamellae, osteocytes
and canaliculi
Osteoid
organic bone matrix secreted by osteoblasts
ground substance (proteoglycans, glycoproteins)
Intramembranous Ossification
membrane bone develops from fibrous membrane (no
cartilage) forms flat bones
Endochondral Ossification
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
Calcium
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
Wolff's law
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
Paget's Disease
excessive and haphazard (disorganized) bone formation and breakdown,
usually in spine, pelvis femur or skull (not controlled)