Download The Skeletal System

The Skeletal System
Anatomy and Physiology
Bone
• A connective tissue
• Contains bone tissue,
cartilage, fibrous
connective tissue,
blood, and nervous
tissue
• It is alive!
Functions
• Provides points of
attachment for
muscles
• Protection
• Support
• House blood
producing cells
• Store inorganic salts
and minerals
A typical bone
• Epiphysis: large knob on
the ends
• Diaphysis: long shaft
• Periosteum: covering over
all
• Compact bone: hard and
rigid outside
• Spongy bone: spongy and
contains marrow
• Articular cartilage: smooth
surface on bone ends
Spongy bone and marrow
• Spongy bone is near
the ends in the
epiphyses
• Contains red marrow,
which produces blood
cells (fills an infant’s)
• Yellow marrow is in
the medullary cavity,
and stores fat, more in
an older adult
Compact Bone
osteocyte
• Tightly packed
• Cells are called osteocytes
• Surrounded by fibers and
cemented by hard
background
• The structure forms
around an osteonic canal,
with blood vessels and
nerves in the center
Osteonic canal
Osteonic Canals: bone grows in
concentric circles
Only in the compact bone!
Bone Cells
• Osteoblasts: are bone
forming cells
• When they mature and
become surrounded
with the hard matrix,
they are osteocytes
• Osteoclasts: break
down bone
Osteoblasts and Osteoclasts
• When would osteoblasts be working?
• When forming new bone for growth, repair,
replacement of aging or dying bone
• When would osteoclasts be working?
• When dissolving older bone containing
dead cells, or to release calcium into the
bloodstream if needed
Calcium Levels
• If too low, parathyroid
gland senses this and
secretes parathyroid
hormone (PTH)
• PTH stimulates
osteoclasts to break down
bone and release calcium
into blood
• Calcium levels in the
blood return to normal
Calcium Levels
• If too high, thryoid
gland senses this and
secretes calcitonin
• Calcitonin stimulates
osteoblasts to form new
bone, depositing
calcium in the new bone
• Calcium levels in blood
return to normal
Why do we need calcium in the
blood?
•
•
•
•
For muscle contraction
Nerve impulse conduction
Blood clotting
Other processes
Orange: is
axial
Yellow: is
appendicular
Types of Skeletal Joints
• Fibrous: immovable,
ex: sutures of skull
• Cartilaginous: bones
connected by
cartilage; limited
movement; ex:
vertebrae
• Synovial: bones
surrounded by capsule
and synovial
membranes; ends of
bones are covered in
cartilage and
surrounded by
synovial fluid; lots of
movement
Fibrous
• Connected by thin
layer of fibrous
connective tissue
Cartilaginous
• Connected by cartilage
• Limited movement, as
when back is twisted
or bent
Synovial
Synovial
• Ball and Socket
• Hip and shoulder
• Ball shaped head
joints with the cup of
the other bone
• Circumduction
Synovial
• Condyloid: oval
shape of one bone
joints with elliptical
cavity of the other
Synovial
• Gliding: surfaces are
nearly flat
• Wrist, ankle
Synovial
• Hinge: convex
surface joins with a
concave surface
• Flexion and extension
• Elbow and knee
Synovial
• Pivot: can rotate
around a central axis
• Proximal ends of
radius and ulna
Synovial
• Saddle: surface of
bones are both convex
and concave; fits in
• Only occurs in the
joint between the
carpal and the
metacarpal of the
thumb