Honors Anatomy & Physiology
a
combination of CT, epithelial &
nervous tissues
 18% of weight of human body
 Skeletal System includes bones &
cartilage
 Part 1: Bone
 Part 2: Axial Skeleton
 Part 3: Appendicular Skeleton
 Part 4: Joints
1.

SUPPORT
skeleton serves
as structural
framework by
supporting soft
tissues &
providing
attachments for
tendons of
muscle
2. PROTECTION
 Protects most
important soft
tissue organs
from injury
3. MOVEMENT
4. MINERAL
 Skeletal muscles
HOMEOSTASIS
attach to bones,
 Bone stores
when the muscle
calcium,
contract the bones
phosphorus which
move
both help make
bone strong
 If body needs
these minerals
bone releases
them
5. BLOOD CELL
PRODUCTION
 red bone marrow
produces RBCs,
WBCs, & platelets
6. TRIGLYCERIDE
STORAGE
 yellow bone
marrow stores
triglycerides
(chemical energy
reserve)
1.
Diaphysis:
shaft or body; the
long cylindrical
portion of the
bone
2. Epiphysis:
distal & proximal
ends of bone
3. Metaphysis:
 region between
diaphysis &
epiphysis
 in growing bone
includes
metaphyseal plate
(hyaline cart. that
allows bone to
lengthen
4. Articular
Cartilage:
 layer of hyaline
cartilage covering
part of epiphysis
where bone forms
a joint with
articulating bone
5. PERIOSTEUM
6. MEDULLARY
 tough , dense,
CAVITY
irregular CT
 aka Marrow
surrounds bone
Cavity
wherever it is not  space w/in
covered by hyaline diaphysis that
cartilage
contains yellow
 helps in repair of
bone marrow in
fractures
adults
 Attachment pt for
ligaments
7. ENDOSTEUM
 thin membrane
that lines marrow
cavity
 contains 1 layer
of bone-forming
cells and CT
 bone
consists of widely separated cells
surrounded by large amts extracellular
matrix
 *bone is hard due to crystallized inorganic
mineral salts
 *bone is flexible due to collagen
1.


OSTEOGENIC CELLS
Stem cells from mesenchyme (origin
of all CT)
only bone cells to divide
2. OSTEOBLASTS
 bone-building cells
 synthesize & secrete collagen fibers
 initiate calcification
3. OSTEOCYTES
 mature bone cells
 main cells in bone
 maintain exchange of nutrients & wastes
with blood
4. OSTEOCLASTS
 huge cells that form by merging of
many (50)monocytes
 in endosteum
 ruffled border faces bone surface:
releases lysosomal enzymes & acids
that digest underlying bone (bone
resorption): part of normal maintenance,
growth, development, & repair of bone
Compact bone
1.


few open spaces
outer bone layer of all bones
Spongy bone
2.

inside bones
 strongest
form of bone
 beneath periosteum of all bone
 functions:
protection & support
 resists stresses produced by weight &
movement


OSTEON:
 aka Haversian Systems
 repeating units thru out compact bone
 each one has central canal with
concentrically arranged lamellae (rings),
lacunae (filled with 1 osteocyte)
 aligned in same direction along lines of
stress
 space between osteon filled with
interstial lamellae
 absence
of osteons
 made of lamellae arranged in irregular
columns called trabeculae
 makes up most of inside of short, flat,
or irregular bones & epiphysis of long
bones
 lighter than compact bone
 Function:

support & protect red bone marrow
1.

1.



longer:
@ epiphyseal plate
wider:
called appositional growth
periosteal osteoblasts on outer surface
of bone
osteoclast remove compact bone inner
border
 Most
bones are formed b/4 birth but
each one continually renews itself for
rest of life
 ~5% of bone being remodeled @ any
given time
 bone remodeling is the ongoing
replacement of old bone tissue by new
bone tissue
1. Bone Resorption
2. Bone Deposition
 removal
of minerals & collagen fibers
from bone by osteoclasts
 results in destruction of bone
extracellular matrix
 addition
minerals & collagen fibers to bone by
osteoblasts
1.
2.
3.
Minerals
 Ca, P, F, Mg, Fe, Mn
Vitamins
 C needed to make collagen fibers & for
osteoblast  osteocyte
 E & B12 needed for protein synthesis
Hormones
 IGF’s in childhood (insulin-like growth
factors)
 estrogens & androgens important in
puberty
 Fracture:
any break in a bone
 Fractures named by:
 severity
 shape or position of fracture line
 person who 1st described it
 Bone
is body’s main reservoir for
calcium (stores 99% of total body Ca)
 Normal blood level Ca 9 -11 mg/100mL
 Calcium important for:
 Muscle contraction
 Nerve impulses
 Blood clotting
 Many enzymes require Ca as cofactor)
2
1.
2.
hormones control Ca in/out bone:
Calcitonin
 Decreases blood Ca levels by
putting more Ca into bone
Parathyroid Hormone (PTH)

Increases blood Ca levels by taking
Ca out of bone (increasing
osteoclast resorption)
1.
Osteoporosis
 condition of porous bones
(resorption > deposition)
 causes: deficient Ca in diet
 USA: > 1 million fractures (hip,
wrist, vertebrae) & afflicts 30
million Americans
 decreased stature, hunched back,
bone pain