Download THE SKELETAL SYSTEM

PART 1: BONES
 made up of CT, epithelial tissue, & nerve
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tissue
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
SUPPORT
 skeleton serves as
structural
framework by
supporting soft
tissues & providing
attachments for
tendons of muscle
1.
2. PROTECTION
 Protects most
important soft tissue
organs from injury
3. MOVEMENT
 Skeletal muscles
attach to bones,
when the muscle
contract the bones
move
4. MINERAL
HOMEOSTASIS
 Bone stores calcium,
phosphorus which
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)
DIAPHYSIS:
 bone’s shaft or
body: the long
cylindrical, main
portion of the bone
1.
2. EPIPHYSIS:
 distal & proximal
ends of the bone
3. METAPHYSIS:
4. ARTICULAR
CARTILAGE
 Region in mature
bone where diaphysis  hyaline cartilage
meets epiphysis
covering part of
epiphysis involved in
 in growing bone
joint
include metaphyseal
plate (hyaline
 reduces friction &
cartilage that allows
absorbs shock @
bone to grow in
freely movable joints
length)
5. PERIOSTEUM
 tough , dense,
irregular CT
surrounds bone
wherever it is not
covered by hyaline
cartilage
 helps in repair of
fractures
 attachment pt for
ligaments
6. MEDULLARY
CAVITY
 aka Marrow Cavity
 space w/in diaphysis
that contains yellow
bone marrow in
adults
7. ENDOSTEUM
 thin membrane that
lines marrow cavity
 contains 1 layer of
bone-forming cells
and CT
 bones are hard due to calcification:
calcium carbonate & other minerals
(Mg, F, K, S) form crystals around
collagen fibers
 bone hardness depends on crystallized
inorganic mineral salts
 bone flexibility depends on collagen
fibers
OSTEOGENIC CELLS
 stem cells from mesenchyme (origin of all
CT)
 only bone cells to divide
1.
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
 has few spaces
 strongest form of bone
 beneath periosteum of all bone
 provides protection & support and 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, 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
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columns called trabeculae
appears spongy but hard
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
 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 of minerals & collagen fibers to bone
by osteoblasts
Minerals
 Ca, P, F, Mg, Fe, Mn
2. Vitamins
 C needed to make collagen fibers & for
differentiation osteoblast  osteocyte
 E & B12 needed for protein synthesis
3. Hormones
 IGF’s in childhood (insulin-like growth
factors)
 estrogens & androgens important in
puberty
1.
 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 hormones control Ca in/out bone:
Calcitonin
 decreases blood Ca levels by putting more
Ca into bone
2. Parathyroid Hormone (PTH)
 increases blood Ca levels by taking Ca out
of bone (increasing osteoclast resorption)
1.
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