A&P
FUNCTION
Provide support to body
Protection of internal organs; brain, heart, lungs
Attachment for muscles
Acts as levers to produce movement
Storage of mineral, calcium and phosphorus
Produce blood cells (hemopoietic tissue)
-Classification of bones-
Long bones found in the appendages, femur, humerus, etc
Short bones found in the hands, feet metacarpals, metatarsals
Flat bones found in the cranium, ribs, sternum, scapula
Irregular bones vertebrae, pelvic bones, skull, carpals, tarsals
Sesamoid bones- bones which have no direct ligamentous attachment to another bone.
Womerian bones- small bones which form on the lambdoidal suture between the parietal and occipital bones of the cranium
-Parts of a long bone-
piphysis- Rounded end of a long bone, composed internally of spongy bone
Diaphysis- the shaft of a long bone
Articular cartilage- hyaline cartilage acts as a lubricant and a smooth surface for an articulations with another bone at a joint.
Periosteum- fine, tough, vascular membrane covering the outer surface of the entire bone. Functions in the repair and growth of the bone
Medullary canal- hollow shaft lined with endosteum (similar to the periosteum) Houses bone marrow either red or yellow depending on age.
Red marrow produces active blood cells
Yellow marrow is fat storage
Bone composition
Epiphysis is composed of spongy bone covered with a thin layer of compact bone.
Spongy bone is composed of interlocking, branching bony plates called trabeculae
Compact bone is composed of osteons which are cylindrical layers of bone which form around a Haversian Canal.
Microscopic structure of bone
The Haversian canal system is found in compact bone only.
The Haversian canal contains a blood vessel which supplies the nutrients and oxygen to osteoblasts which produce the bone.
The osteon is a series of cylindrical columns of bone which are produced around the Haversian canal.
A lamella is a layer of bone surrounding the Haversian canal
A lacuna is a space in the bone which houses an osteoblast or later an osteocyte
Volkman’s canals are transverse canals through the bone which contain capillaries which interconnect the lacunae where the osteoblasts.
Osteoblasts are bone manufacturing cells.
Osteocytes are bone maintaining cells.
Osteoclasts are bone dissolving cells.
Haversian canal system
Bone is essentially collagen with inorganic minerals added.
Calcium carbonate and calcium phosphate
Ossification- is the hardening of bone due to the addition of minerals. Done by bone making cells called osteoblasts.
Minerals add hardness to bone so it resists crushing
Bone Growth and Development
2 types of ossification:
Membranous ossification- layers of membranous connective tissue form in sites which will become bone. Occurs only in the flat bones of the cranium, sternum, ribs, scapula, etc. etc.
Cartilagenous or Endochondral ossification- A cartilage model of a bone is formed, then bone replaces the cartilage. Occurs in long bones, short bones, and irregular bones.
Bones as levers
1st class levers examples, scissors, teeter-totters
2nd class levers examples, wheelbarrel
3rd class levers
Most joints of the body are 2nd and 3rd class levers
3 parts to a lever F-force or muscle contracting, Fulcrum is an axis point, represented by a triangle, Resistance or Load the weight or mass that is being moved by the lever.
Blood cell formation (Hematopoiesis)
Occurs in the yolk sac as an embryo, liver and spleen as a fetus, long bones of young children, and the irregular spaces of spongy bone in the adult.
Red Marrow soft, netlike mass of connective tissue found in the medullary canals of long bones and the spaces of spongy bone.
Erythrocytes, most leukocytes, and thrombocytes are all manufactured in the red bone marrow
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In the adult, spongy parts of the skull, ribs, sternum, clavicle, vertebrae, and pelvis are where active red bone marrow is located.
Storage of inorganic salts or minerals
Calcium is needed for: blood clot formation, nerve impulse conduction, muscle cell contraction
The storage and release of calcium is controlled by two endocrine glands.
Parathyroid hormone (PTH) secreted by the parathyroid gland stimulates osteoclast activity, elevating blood Ca++ levels. Releases calcium to the blood to be used in different functions.
Calcitonin secreted by the thyroid gland stimulates osteoblast activity, decreasing blood Ca++ levels. Stores calcium by making bone.
Disorders of the skeletal system
Osteoarthritis- degenerative disease of the joints due to trauma and wear and tear to the articular cartilage. Closely associated with aging.
Rhuematoid arthritis-autoimmune disease genetically carried. Causes deformity and disfigurement starting in children, teens, and young adults.
Osteoporosis-Decreased osteoblast activity due to the body’s inability to absorb calcium from the diet. Much more prevelant in females. After menopause, women cannot absorb calcium as well due to the lack of estrogen.
Gout-type of arthritic disease in which uric acid crystals form in the joints causing pain and swelling. Periodic flare ups occur.
Rickets-Deficiency disease of vitamin D. Calcium cannot be absorbed without vitamin D. If it occurs during active growth periods of children severe bone stunting and deformities may occur.
Disorders of the skeletal system cont.
fracture-break or disruption of bony tissue. Due to trauma or stress
Sprain-stretching , tearing or total disruption of a ligament
Scoliosis-a lateral or spiral curvature of the spine. Most prevalent in women.
Kyphosis-abnormal posterior curve of the thoracic vertebrae.
(hunch back)
Lordosis-abnormal anterior curve of the lumbar vertebrae.
(sway back) More prevalent in men.
Osteomyelitis-bacterial infection of a bone.
THE JOINTS (ARTICULATIONS)
Articulations are junctions between bones. They vary a great deal in structure. They are classified according to the amount of movement.
3 types:
Synarthroses (immovable joints)
Amphiarthroses (slightly movable joints)
Diarthroses (freely movable joints)
Immovable joints
Occur between bones that come into close contact with one another
The bones of these joints are separated by a thin layer of fibrous connective tissue or cartilage.
Examples are the sutures of the flat bones of the cranium and the skull. (sagittal, coronal, lambdoidal, and squamousal sutures ) Also the bones of the pelvis.
No active movement takes place in these joints.
Slightly Movable joints
Amphiarthroses are connected by disk of fibrocartilage or by ligaments.
Articular surfaces are covered with hyaline cartilage
These joints allow a limited amount of movement.
Examples are: intervertebral discs and joints, symphysis pubis, sacroiliac joint, acromioclavicular jt., sternoclavicular jt, costovertebral jt., and the distil end of the fibula and tibia. (ankle)
Freely movable joints (Diarthroses)
These are the most complex of all the joints.
These joints are freely movable and the articular surfaces are covered with articular cartilage.
They are held together by a surrounding, tube like capsule called a joint capsule. (synovial capsule) and ligaments.
The inner lining of the capsule is called the synovial membrane which secretes a serous fluid (synovial fluid) which acts to lubricate the joint.
Some synovial joints contain fibrocartilage pads and fluid filled sacs called bursae. They pad and reduce friction between tendons and bones in synovial joints.
Types of Freely Movable Joints (Diarthroses)
Ball and Socket Joint-a ball shaped head that articulates with a cup shaped socket. The most freely movable joint. Movement in all 3 planes.
Condyloid Joint
An oval shaped condyle of one bone fits into an elliptical cavity of another bone.
Examples are: metcarpal-phalangeal jts
2 planes of movement, no rotation.
Gliding Joints
Nearly flat or slightly curved articular surfaces.
Examples: carpal joints of the wrist, tarsal joints of foot and ankle.
2 planes of movement, no rotation.
Hinge Joints
Convex surface of bone fits into a concave surface of the other bone.
Examples: humeral-ulnar jt. of the elbow, knee, interphalangeal joints of the digits.
Only 1 plane of movement.
Pivot Joint
A cylindrical surface of one bone rotates within a ring formed of bone and fibrous tissue.
Movement is limited to rotation.
Example: proximal end of the radius at the elbow.
Saddle Joint
Bones with both concave and convex shaped articular surfaces.
This arrangement allows for a wide variety of movements.
Example: 1st metcarpal and carpal joint (thumb)
2nd greatest range of motion of all the joints, behind the ball and socket joint