36.1 ¢â‚¬â€œ The Skeletal System form the skeletal system....
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36.1 – The Skeletal System
The Skeleton All organisms need structural support.
cytoskeleton (unicellular) exoskeleton (arthropods) or an endoskeleton
The Skeleton Functions of the skeleton:
support protects internal organs movement stores mineral reserves provides site for blood cell
Bones and other connective tissues (cartilage and ligaments) form the skeletal system.
Appendicular Skeleton • The bones of the arms
and legs, along with the bones of the pelvis and shoulder area form the appendicular skeleton (grey).
Structure of Bones
Haversian canal Compact bone
Structure of Bones a network of living
cells and protein fibers surrounded by deposits of calcium salts
surrounded by a tough layer of connective tissue called the periosteum
Blood vessels in the periosteum carry oxygen and nutrients to the bone.
Osteocytes (mature bone cells) are embedded in the bone matrix.
Other bone cells (osteoclasts and osteoblasts) line the Haversian canals and the surfaces of compact and spongy bone. Osteoclasts break down bone. Osteoblasts produce bone.
Bone Marrow a soft tissue inside
the cavities within bones
two types: Yellow marrow –
made up of fat cells.
Red marrow produces red blood cells, some kinds of white blood cells, and platelets.
Development of Bones
Development of Bones The skeleton of an embryo is composed of cartilage
(strong connective tissue, softer and more flexible than bone).
Cartilage is replaced by bone ossification. Bone tissue forms as osteoblasts secrete mineral
deposits. When the osteoblasts become surrounded by bone
tissue, they mature into osteocytes.
Many long bones have growth plates at either end.
Growth of cartilage at these plates causes bones to lengthen. Gradually, this cartilage is replaced by bone tissue.
By early adulthood, cartilage in the growth plates is replaced by bone, the bones become ossified, and growth stops.
Joints where one bone attaches to
another bone is called a joint
Joints permit bones to move without damaging each other.
3 types: immovable, slightly movable, or freely movable
Immovable Joints “fixed joints”
allow no movement
bones are interlocked and held together by connective tissue, or they are fused together
Ex: skull bones
Slightly Movable Joints
permit a small amount of restricted movement
Ex: joints between adjacent vertebrae
Freely Movable Joints permit movement in one
or more directions
4 common types
ball-and-socket joints (many directions)
hinge joints (back- and-forth)
pivot joints (one bone rotates around the other)
Structure of Joints Ligaments hold bones
together in joints and are attached to membranes that surround bones.
Synovial fluid lubricates surface of joint, enabling the bones to slide past each other more smoothly.
Bursae act as shock absorbers.