Anatomy and Physiology of the
Skeletal System
Introduction
• The skeletal system provides a rigid framework to support and protect the body.
Bones function closely with the muscular system to permit movement.
• In this lecture, we will discuss the functions and structure of bones and how they are
formed.
• We will also learn the names of the major bones and where they are located.
• In order to be effective in working with orthopedic patients, the medical assistant
must have an understanding of the diseases and conditions that affect the skeletal
system.
• Since bones play a major role in body movement and support, injuries may seriously
alter the activities of daily living.
• Therefore, we will discuss diseases and injuries of the bones and joints along with
procedures used in diagnosis and treatment.
Skeletal System
• Function
– Support
• Provides the framework to support the body’s fat, muscle, and skin.
– Protection
• Protects the body’s vital organs.
– Leverage
• Serves as a point of attachment for skeletal muscles responsible for movement.
– Storage
• Stores most of the body’s calcium supply.
– Blood cell production
• Forms red and white blood cell and platelets.
– Form
• Gives shape to the body.
Skeletal System (cont'd)
• Bone Structure
– Composition
• 20% water
• 2/3 inorganic materials
• 1/3 organic materials
Skeletal System (cont'd)
• Bone the Organ
– Parts:
– Compact—hard; dense; found near the surface where strength is required. (Tissue)
– Spongy (cancellous)—mesh-like; found in ends of long bones and center of flat
bones. (Tissue)
– Marrow—loose connective tissue that fills cavities of bone.
• Red—produces formed elements of blood.
• Yellow—made up of fatty tissue—has no blood production function.
– Periosteum—connective tissue around a bone.
– Endosteum—inner lining of bones.
– Haversian canal—duct in bone that contains blood vessels.
– Osteocytes— mature bone cells that maintain the bone
– Osteoblasts- immature bone cells that lay the bone matrix
– Osteoclasts- bone cells that reabsorb damaged or old bone tissue.
Long Bone Features
Skeletal System (cont'd)
• Four General Shapes
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Long
Short
Flat
Irregular
Skeletal System (cont'd)
• Growth and Development
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Bone formation (ossification) begins six weeks after fertilization.
Continues through adolescence (some parts do not stop growing until ages 18 to 25).
Bone growth increases at puberty with the increase of the sex hormone.
While the bone lengthens, it also grows in diameter due to the formation of cell layers
on the outer surface of bone, and the erosion of the cell layers beneath.
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2 types of ossification = endochondral and intramembranous
– Bones become thinner and weaker as a normal process of aging.
– Reduction in bone mass begins to occur between ages 30 and 40.
– Once bone mass reduction begins:
• Females lose approximately 8% of bone mass every decade.
• Males lose approximately 3% of bone mass every decade.
• Osteoporosis results from bones becoming so thin they can no longer withstand normal stress.
Skeletal System (cont'd)
• Number of Bones
– 270 at birth
– 206 at adulthood
– Difference between number at birth and adulthood due to fusion of
bones
Skeletal System (cont'd)
• Divisions of the Skeletal System
– Axial skeleton
• Spinal column
• Skull
• Rib cage
– Appendicular
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Arms
Hands
Legs
Feet
Shoulders
Pelvis
Cranial and Facial Bones
Identification of Bones (cont'd)
• Skull
– Cranium
• Protects the brain from injury.
• Fontanels
– Unossified space or “soft spot” located between cranial bones.
– Allows for molding of skull during childbirth and for enlargement of skull
as growth occurs.
• Found in newborn and infancy; closed by age two.
– Composed of the fusion of eight cranial bones:
» Frontal—1
» Parietal—2
» Temporal—2
» Occipital—1
» Sphenoid—1
» Ethmoid—1
Identification of Bones (cont'd)
• Skull (con’t)
– Facial
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Nasal—2
Zygoma—2
Maxilla
Mandible
Palate—2
Concha—2
Vomer—1
Hyoid—1
Identification of Bones (cont'd)
• Skull (con’t)
– Ear bones (ossicles) smallest bones in the body:
• Malleus (hammer)—2
• Incus (anvil)—2
• Stapes (stirrup)—2
Identification of Bones (cont'd)
• Rib Cage
– Twelve pairs of long slender bones attached to vertebrae.
• True ribs—first seven pairs—attached directly to sternum and spine.
• False ribs—last 5 pairs—attached to cartilage of rib above or have
only anterior attachment.
• Last 2 pairs of false ribs; referred to as floating ribs; only attach to
vertebrae.
• Sternum (breast bone)—1
Identification of Bones
• Spinal Column
– Supports the head, keeps trunk erect, protects spinal cord.
– Sections:
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Cervical—first 7 neck vertebrae (C1–C7)
Thoracic—12 chest vertebrae (T1–T12)
Lumbar—5 back vertebrae (L1–L5)
Sacral—1 large vertebra fused from five original bones
Coccyx (tailbone)—1 vertebra fused from four original bones
Cartilage disks separate the vertebrae to absorb shock and allow flexibility.
Bones of the Rib Cage
Identification of Bones (cont'd)
• Upper Extremities
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Clavicle (collar bone)—1
Scapula (shoulder blade)—2
Humerus (arm) 2
Ulna—2
Radius—2
Carpals (wrist) eight in each wrist
Metacarpals (palm) 5 in each palm
Phalanges (fingers) each finger has 3 bones, each thumb has 2, 14 in each hand
Identification of Bones (cont'd)
• Pelvic Girdle—
– Differences between male and female: female must accommodate
pregnancy and childbirth
• Ilium—upper wedge called iliac crest; wider in females—2
• Ischium—2
• Pubis—2
The Male Pelvis
The Female Pelvis
Identification of Bones (cont'd)
• Lower Extremities
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Femur (thigh) strongest bone in body—2
Patella (kneecap)—2
Tibia (shinbone)—2
Fibula—2
Tarsal (ankle) 7 in each ankle
Metatarsals (instep) 5 in each instep
Phalanges (toes) 14 in each foot
Joints
• A place where any two or more bony parts
join together; also called an articulation.
• Held together by bands of connective tissue
called ligaments.
Joints
Joints (cont'd)
• Joint Classifications
– Diarthrosis
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Moveable
Knee, elbow, which has action of a hinge
Shoulder or hip, which has action like that of ball and socket
Most joints are diarthrotic and contain:
– Articular cartilage
– Bursa, sack-like capsules for cushioning
– Synovial cavity, filled with synovial fluid for lubrication
– Synovial membrane around and between tendons to lubricate and
reduce friction
Joints (cont'd)
• Joint Classifications (cont'd)
– Amphiarthrosis/cartilaginous
• Partly moveable
• Vertebrae
– Synarthrosis/fibrous
• Immovable
• Cranial sutures
Joints (cont'd)
• Types of Joints
– Gliding joints
• Found at the end of clavicles, between carpals and tarsals—slight
movement.
– Hinge joint
• Angular movement in a single plane—knee, elbow.
– Pivot joint
• Permit rotation only—joint between C1 and C2 allows the head to
rotate to either side.
– Ball and socket
• Round head of one bone rests within the cup-like depression in
another—shoulder, hip.
Joints (cont'd)
• Types of Movement
– Flexion
• Movement that reduces the angle between articulating joints.
– Extension
• Movement that increases the angle between articulating joints.
– Abduction
• Movement away from the longitudinal axis of the body.
– Adduction
• Movement towards the longitudinal axis of the body.
– Rotation
• Turning around the longitudinal axis of the body or limb.
Diagnostic Examinations
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Athroscopy
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Computer Tomography (CT scan)
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Visual inspection of a joint with an endoscope.
An x-ray which allows three dimensional views.
Magnetic Resonance Imaging (MRI)
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Process uses strong magnets and radio waves to construct a three dimensional image.
• Advantages over CT scan:
– No radiation used.
– Soft tissues seen in more detail.
• Disadvantages:
– More expensive.
– Patients put in tube; obesity or claustrophobia could be a problem for some
patients.
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X-ray
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Image produced by ionizing radiation.
Fractures
• Types of Fractures:
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Greenstick—bone cracks but does not break, common in children.
Simple or closed—complete break, does not break skin.
Compound or open—complete break, bone protrudes through skin.
Impacted—broken ends are jammed into each other.
Comminuted—more than one fracture, bone fragments.
Depressed—broken pieces of skull driven inward.
Spiral—break winds around bone, common in sports accidents.
Colles—fracture of distal end of radius and/or ulna.
Examples of Fracture Types
Fractures (cont'd)
• Treatment
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Immobilization of the affected part.
Prevention of shock.
Elevate.
Cold pack or ice.
Reducing the fracture:
• Alignment of the bones.
• Splint or cast keeps bone immobilized.
– Open reduction is a surgical procedure to achieve alignment of the bone
and repair tissues and skin.
Fractures (cont'd)
• Healing Process
– When a fracture occurs, a collection of blood forms at site.
– This begins the inflammatory reaction which begins the healing
process.
– A fibrous bridge formed between the fracture fragments is called a callus.
– As time passes this callus turns first to cartilage and then to bone.
• Amputation
– Loss of an extremity due to injury or disease.
– Phantom limb is the sensation that the missing limb is present.
– Prosthesis is an artificial limb.
Common Diseases and Disorders
• Arthritis
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Description: joint inflammation.
More than 100 different types.
Currently affects 40 million Americans, mostly women.
Most common forms:
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Osteoarthritis
Rheumatoid arthritis
Gout
Fibromyalgia
Lupus
Arthritis
Common Diseases and Disorders
(cont'd)
• Bursitis
– Description: inflammation of sac located around a joint; most often
occurs at hip, shoulder, or knee.
– SX: pain upon movement, limited motion of joint.
– Causes: usually occurs in middle age and is result of recurring trauma or
inflammatory joint disease.
– TX: joint rest, pain medication, steroid injection combined with
anesthetic, removal of fluid by aspiration, physical therapy.
Common Diseases and Disorders
(cont'd)
• Dislocation
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Description: displacement of the bones of a joint.
SX: pain.
Causes: congenital, trauma, disease of surrounding joint.
TX: reduction, splint, cast, traction.
Common Diseases and Disorders
(cont'd)
• Herniated Disk (ruptured disk)
– Description: the soft gel-like material within an intervertebral disk has been
forced through its outer surface causing pressure on a spinal nerve.
– SX: severe lower back pain, frequently radiating deep into the buttocks and down
the back of the leg; sensory loss from compression of nerve; motor difficulties.
– Causes: severe trauma or strain, degeneration of the intervertebral joints; occurs
in adults, mainly men under 45; often occurs from trauma in elderly.
Common Diseases and Disorders
(cont'd)
• Lumbar Myositis
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Description: inflammation of the lumbar region muscles of the back.
SX: low back pain.
Causes: straining of back muscles.
TX: rest, mild analgesics, and muscle relaxers.
• Osteoporosis
– Description: metabolic bone disorder where the bone becomes porous, brittle and prone
to fracture.
• Two types: Primary, which is postmenopausal and Secondary, following various
abuses to the body such as steroid therapy.
– SX: snapping sound followed by instant pain, spinal curvatures, fractures, loss of height.
– Causes: aging, inadequate calcium, faulty metabolism, tobacco, family history.
– TX: increasing exercise, estrogen supplement, calcium, vitamin D.
Common Diseases and Disorders
(cont'd)
• Spinal Curvatures
– Kyphosis
• Description: bowing of the back, usually at the thoracic level.
• SX: visible curving, pain, stiffness, tightening of hamstring muscles.
• Causes: growth retardation, degeneration of intervertebral disks,
osteoporosis.
• TX: exercise, firm mattress, surgery.
Common Diseases and Disorders
(cont'd)
• Spinal Curvatures (cont'd)
– Lordosis
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Description: anterior convex curvature of the lumbar spine.
SX: visual curvature.
Causes: poor posture, wearing high heels.
TX: exercise, improving posture, proper footwear.
– Scoliosis
• Description: lateral curvature of the spine usually in the thoracic region.
• SX: uneven hemlines or unequal pants legs, one hip appearing higher than the other,
one shoulder appearing higher.
• Causes: congenital defects, muscular dystrophy, paralysis, transmitted trait that
develops during the growing process, poor posture, uneven leg lengths.
• TX: exercise, brace, surgery.
SPINAL CURVATURES
Common Diseases and Disorders
(cont'd)
• Sprain
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Description: complete or incomplete tear in the supporting ligament of a joint.
SX: pain, swelling, black and blue discoloration; ankle most common site.
Causes: twisting action.
TX: follow R.I.C.E.—Rest, Ice, Compression, and Elevation; may require surgery.
• Carpal Tunnel Syndrome
– Cause: compression of median nerve at the wrist.
– SX: numbness, pain in hand.
– TX: surgery to relieve pressure.
Questions
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Name the bones and locate them on a skeleton.
What is the difference between compact and spongy bone?
How many phalanges are there?
What is the difference between true and false ribs?
Name three types of spinal curvatures and describe their physical
characteristics.
What is a greenstick fracture?
What does the abbreviation R.I.C.E. stand for?
What does open reduction mean?
What is the cause of lumbar myositis?
How many bones are in the human body?
How many bones are there in the human body at birth?