Skeletal System 1

SKELETAL SYSTEM rev 9-11

• Bone or Osseous Tissue– consists primarily of nonliving extracellular

crystals of calcium minerals which make the bone hard

– contains several types of living bone cells, nerves, and blood vessels

– Is classified as a connective tissue

Skeletal System 2

Bones perform 5 important functions:• support• movement • protection• formation of blood cells• mineral storage

Skeletal System 3

Bones can be classified into 4 categories • Long--bones of the limbs and fingers

– are longer than they are wide– consist of a hollow, cylindrical shaft called the

diaphysis and– an enlarged knob at each end called the

epiphysis– An internal marrow space or cavity

Skeletal System 4

• Short--bones of the wrists • Flat--including the cranial bones, sternum and ribs• Irregular--hip bones and vertebrae

• All bones contain 2 types of osseous tissue– a solid, compact tissue – a spongy tissue with trabeculae

Skeletal System 5

Periosteum covers the outer surface of all bones• is a tough connective tissue• the outermost layer is dense irregular connective

tissue– is supplied with nerve fibers, lymphatic vessels

and blood vessels which enter the bone through openings called nutrient foramen

Skeletal System 6

– provides insertion or anchoring points for the tendons and ligaments

– contains bone forming cells– if the end of a long bone forms a movable joint,

the joint surface is covered by articular or hyaline cartilage

Skeletal System 7

The internal part of the bone surface is covered by endosteum

• this covers the trabeculae in the marrow cavities of the spongy bone– lines the canals that pass through compact bone– contains osteoblasts (bone forming cells),

osteoclasts (bone resorption cells), and osteocytes (bone cells)

Skeletal System 8

Long bones• Compact bone forms the external layer • central cavity of the shaft of long bones is called

the medullary cavity– this cavity is filled with red marrow in children

and with yellow bone marrow in adults• Compact bone consists of calcium phosphate laid

in a pattern around the central cavity

Structural Unit of Compact bone is the– Osteon (or Haversian system) this forms a

pattern of hollow tubes like the growth rings of a tree trunk

Skeletal System 9

• Parts of the Haversian system:– each ring of bone tissue in the hollow tube is

called a lamellae – Haversian or Central canal: middle cavity in

a Haversian system. Contains the blood vessels and nerve fibers

– lacunae: found at the junctions of the lamellae and is filled with bone cells called osteocytes

Skeletal System 10

• canaliculi: thin canals in bone tissue which connect the lacunae to each other and to the central canal

• Volkmann’s canals lie at right angles to the long axis of the bone and connect the blood and nerve supply of the periosteum to those in the central canals and the medullary cavity– this allows all osteocytes to get nutrients

Skeletal System 11

Spongy bone

• Is found inside the epiphysis• spongy bone is less dense than compact bone• spongy bone is a honeycomb of hard, strong

pieces called trabeculae • blood cell formation (hemopoiesis) takes

place in the spongy bone– Contains the epiphyseal plate

• When bone length growth is completed, the epiphyseal plate becomes ossified (hardened) and leaves an epiphyseal line

Skeletal System 12

SKELETAL SYSTEM

• Skeleton – provides support– protects internal organs– produces blood cells– stores minerals– stores energy– Permits movement via muscle attachments

Skeletal System 13

Skeletal system contains 3 types of connective tissue:

• bone--hard elements of the skeleton• ligaments--dense fibrous connective tissue that

binds the bones to each other• cartilage--specialized connective tissue consisting

primarily of fibers of collagen and elastic in a gel-like fluid called ground substance

Skeletal System 14

The Skeleton is organized into the• Axial skeleton and the Appendicular skeleton• Axial skeleton

– forms the long axis of the body which supports the head, neck and trunk

– consists of the – skull, **bones of the ear– vertebral column, **hyoid bone (in the throat)– ribs and – sternum

Appendicular skeleton• bones which help get us from place to place

(locomotion) and enable us to manipulate our environment

**these bones are also parts of the axial skeleton

Skeletal System 15

The Skull includes the bones of the face, the cranial bones and the jaws

– Frontal bone (forehead)– Parietal bones (behind the frontal bone)– Occipital bone (forms the back of the skull)

• near the base of this bone is an opening called the foramen magnum.

Skeletal System 16

– Occipital condyles--2 rounded bumps at the base of the skull which pivot on the 1st vertebrae (as in nodding the head to say “yes”)

– Temporal bones – Sphenoid bone – Ethmoid bone

Skeletal System 17

• Facial bones and jaws-comprise the front of the skull

• zygomatic bones• nasal bones • lacrimal bones• maxillary bones form part of the eye sockets,

anchors the upper row of teeth, and forms part of the upper palate

• Mandible or lower jaw anchors the lower teeth• Hyoid bone: not really part of the skull

Skeletal System 18

– Ear bones• present in the middle ear and move when air

vibrations bend the eardrum inward– called the malleus (hammer), incus (anvil) and

stapes (stirrup)

• Several of the cranial and facial bones contain air spaces which form the sinuses

• Vertebral column or spine– supports the head, protects the spinal cord and serves as

the attachment for each of our arms and legs and the body’s muscles

Skeletal System 19

– Is a column of 33 vertebrae which extends from the skull to the pelvis

– is classified into 5 anatomical regions• cervical (neck)• thoracic (chest or thorax)• lumbar (lower back)• sacral (sacrum/upper pelvic region)• coccygeal (coccyx or tailbone)

Skeletal System 20

– The first cervical vertebrae is called the Atlas• it articulates with the occipital condyles

– The second cervical vertebrae is called the Axis– vertebrae share 2 points of contact called

articulations– vertebral bodies are separated from each other

by intervertebral disks

Skeletal System 21

• Ribs and sternum (breastbone)– Sternum is actually 3 fused bones– protect the chest cavity– we have 12 pairs of ribs

• the upper 7 pairs, called “true” ribs, • “False ribs:

– pairs 8-10 are joined to the 7th rib by cartilage and are thus indirectly attached to the sternum

• Floating ribs: pairs 11 and 12: don’t attach to the sternum at all.

Skeletal System 22

Appendicular skeleton• bones which help get us from place to place

(locomotion) and enable us to manipulate our environment– includes the:– Pectoral Girdle is a supportive frame for the

upper limbs– Arms (the humerus, ulna, radius, wrist bones,

the palm, and the fingers)

Skeletal System 23

– The Pelvic Girdle consists of the 2 pelvic bones and the sacrum and coccyx

– they meet in front at the pubic symphysis where cartilage joins the 2 bones

• primary purpose is to support the weight of the upper body against the force of gravity

• in adult women, the pelvic girdle is

– broader and shallower than in men and

– the pelvic opening is wider/rounder--to allow for childbirth

– the sacrum is flatter

Skeletal System 24

– The leg bones:• Femur• Patella• Tibia• Fibula• Tarsals• Metatarsals• Phalanges (toes)

Skeletal System 25

Mature Bone Remodeling and Repair

• Changes in shape, size, strength:– Dependent on diet, exercise, age

• Bone cells regulated by hormones:– Parathyroid hormone (PTH): removes calcium

from bone– Calcitonin: adds calcium to bone

• Repair: hematoma and callus formation

Skeletal System 26

• Joints or Articulations– are sites where 2 or more bones meet– give our skeleton mobility– hold the skeleton together– are the weakest parts of the skeleton

• ligaments and tendons are connective tissues that stabilize each joint

Skeletal System 27

• Joint types– freely movable or synovial --bones are separated by a

thin fluid filled synovial cavity which secretes synovial fluid

• Synovial membrane lines the interior surfaces of the joint.

• Hyaline cartilage lines the articulating surfaces of the bones

Types of synovial joints:

• Ball and socket--the ball end of one bone fits into the socket of another bone: shoulder and hip joints

• Hinge joint —allows movement in one plane– Knee and elbow joints

Skeletal System 28

• Slightly Movable or Cartilaginous --has no synovial cavity and permit only slight movement – has a pad of fibrocartilage between 2 bones

• Pubic Symphysis • intervertebral discs• sacroiliac• joint connecting the lower ribs to the

sternum

Skeletal System 29

• Immovable or Fibrous Joints – flat bones in a baby’s skull

• at birth these bones are separated by space filled with fibrous connective tissue. These “soft spots” are called fontanels

Skeletal System 30

Diseases and Disorders of the Skeletal System

• Sprains: stretched or torn ligaments– Partially torn ligaments will repair themselves but take

a long time due to poor vascularization

– Completely torn ligaments require surgery to repair

• Cartilage injuries usually due to overuse– Require surgery to remove damaged cartilage

• Bone dislocation: occurs when bones are forced out of alignment– Subluxation is a partial dislocation

• Bursitis: inflammation of the part of the joint which contains the synovial fluid– Falling on your knees, repeated leaning on your elbows

• Inject with anti-inflammatory drugs

• Remove some excess fluid by needle aspiration to relieve pressure in the joint

• Tendinitis: inflammation of the tendon sheath– Typically caused by overuse

• Arthritis: inflammation of joints– Rheumatoid Arthritis

– Osteoarthritis= Degenerative Joint Disease (DJD)

Skeletal System 31

Rheumatoid Arthritis• Thought to be an autoimmune disease that causes chronic

joint inflammation as well as inflammation of tissue around the joints

– Inflammation in other body organs

• ? Genetic cause, environmental, viral, bacterial

• Exacerbations and remissions

• Chronic inflammation leads to destruction of cartilage, bone and ligamentsjoint deformity

• Symptoms: fatigue, energy loss, decreased appetite, low-grade fever, muscle and joint aches and stiffness (worse in mornings)

Skeletal System 32

Treatment: ---REST

– reduce joint inflammation and pain

– Patient education to maximize joint function

– Prevent joint destruction and deformity

• Medications:– Aspirin and corticosteroids, NSAIDs (non-steroidal

anti-inflammatory drugs), to decrease pain and inflammation

• No known cure

Skeletal System 33

Skeletal System 34

Homeostatic Imbalances

• Osteomalacia (in adults)– Bones are inadequately mineralized causing

softened, weakened bones– Main symptom is pain when weight is put on

the affected bone– Caused by insufficient calcium in the diet, or by

vitamin D deficiency

Skeletal System 35

Homeostatic Imbalances

• Rickets– Bones of children are inadequately mineralized

causing softened, weakened bones– Bowed legs and deformities of the pelvis, skull,

and rib cage are common– Caused by insufficient calcium in the diet, or by

vitamin D deficiency

Skeletal System 36

Homeostatic Imbalances

• Osteoporosis– Group of diseases in which bone reabsorption

outpaces bone deposit– Spongy bone of the spine is most vulnerable– Occurs most often in postmenopausal women– Bones become so fragile that sneezing or

stepping off a curb can cause fractures

Skeletal System 37

Osteoporosis: Treatment

• Calcium and vitamin D supplements

• Increased weight-bearing exercise

• Hormone (estrogen) replacement therapy (HRT) slows bone loss

• Natural progesterone cream prompts new bone growth

• Statins increase bone mineral density

Skeletal System 38

Paget’s Disease• Characterized by excessive bone formation and

breakdown; – Initially have excessive bone resorption (osteoclastic

phase) followed by a reactive phase of excessive, abnormal bone formation (osteoblastic phase)

• Pagetic bone is chaotic, fragile and weak and tends to have reduced mineralization

• Usually localized in the skull, spine, pelvis, femur, • Unknown cause (possibly viral)• Treatment includes the drugs Didronate and

Fosamax

Skeletal System 39

Bone Fractures (Breaks)

• Bone fractures are classified by:– The position of the bone ends after fracture– The completeness of the break– The orientation of the bone to the long axis– Whether or not the bones ends penetrate the

skin

Skeletal System 40

Types of Bone Fractures

• Nondisplaced – bone ends retain their normal position

• Displaced – bone ends are out of normal alignment

• Complete – bone is broken all the way through• Incomplete – bone is not broken all the way

through

Skeletal System 41

Types of Bone Fractures

• Compound (open) – bone ends penetrate the skin• Simple (closed) – bone ends do not penetrate the skin

• Comminuted – bone breaks into three or more pieces; common in the elderly

• Oblique - a fracture which goes at an angle to the axis

• Epiphyseal – epiphysis separates from diaphysis along epiphyseal plate; occurs where cartilage cells are dying

• Greenstick – incomplete fracture where one side of the bone breaks and the other side bends; common in children