The Skeletal System PDF/PPT


The Skeletal System

       Skeleton comes from a Greek word meaning dried up body.

       Bone appears dead and dried up, but it is not!

       Bone is living tissue

       Newborn human has 350 bones

       Adult human has 206 bones

       Parts of the skeletal system

       Bones (skeleton)



       Ligaments (bone to bone)(tendon=bone to muscle)

Functions of Bones

  • Support of the body (framework)
  • Protection of soft organs
  • Serve as levers (with help from muscles)
  • Storage of minerals and fats (calcium)
  • Blood cell formation

Bones of the Human Body

Two basic types of bone tissue

    • Compact bone
      • Dense/hard
    • Spongy bone
      • (Cancellous)
      • Many open spaces
        • Decrease wt of bone/contain red bone marrow

Classification of Bones on the Basis of Shape

  • Long bones
    • Typically longer than wide
    • Have a shaft with heads at both ends
    • Contain mostly compact bone
    • Found in legs and arms

          Examples: Femur, humerus

  • Short bones
    • Generally cube-shape and small
    • Contain mostly spongy bone
    • Found in wrist, ankles, and toes

          Examples: Carpals, tarsals

  • Flat bones
    • Thin and flattened
    • Usually curved
    • Cover organs/provide surface for lg. muscle
    • Thin layers of compact bone around a layer of spongy bone

          Examples: Skull, ribs, sternum

  • Irregular bones
    • Irregular shape
    • Do not fit into other bone classification categories

          Example: Vertebrae and hip

Gross Anatomy of a Bone

  • Diaphysis

§  Shaft

§  Composed of compact bone

  • Epiphysis

§  Ends of the bone

§  Composed mostly of spongy bone

  • Periosteum

§  Outside covering of the diaphysis

§  Fibrous connective tissue membrane

§  Serves as an attachment for muscle

  • Arteries

§  Supply bone cells with nutrients

·         Articular cartilage

§  Covers the external surface of the epiphyses

§  Made of hyaline cartilage

§  Decreases friction at joint surfaces

·         Medullary cavity

§  Cavity of the shaft

§  Contains yellow marrow (mostly fat) in adults

§  Contains red marrow (for blood cell formation) in infants

Changes in the Human Skeleton

  • In embryos, the skeleton is primarily hyaline cartilage
  • During development, much of this cartilage is replaced by bone
  • Cartilage remains in isolated areas
    • Bridge of the nose
    • Parts of ribs
    • Joints

Bone Growth

  • Epiphyseal plates allow for growth of long bone during childhood
    • New cartilage is continuously formed
    • Older cartilage becomes ossified
      • Cartilage is broken down
      • Bone replaces cartilage
  • Bones are remodeled and lengthened until growth stops
    • Grow longitudinally for height
    • Bones grow in width to support weight

Epiphyseal Disc

       Growth plate

       The cartilage near the epiphyseal disc multiplies and eventually becomes ossified (turns to bone)

       As long as new cartilage continues to form the bone continues to lengthen.

       When the growth plate hardens and becomes ossified, growth stops

       Hormones play a big part in this

       Growth hormone stimulates growth

       Sex hormones stop growth

Bone Width

       Long after longitudinal bone growth has stopped, bones continue to grow in thickness and width.

       Bones are continuously being reshaped

Types of Bone Cells

  • Osteocytes
    • Mature bone cells
  • Osteoblasts
    • Bone-forming cells
  • Osteoclasts
    • Bone-destroying cells
    • Break down bone matrix for remodeling and release of calcium
  • Bone remodeling is a process by both osteoblasts and osteoclasts

Bone Remodeling

       A combined action of osteoblasts (bone forming cells) and osteoclasts (bone destroying cells)

       Osteoblasts deposit bone on the external bone surface

       Osteoclasts break down bone from the inside

Bone Fractures

  • A break in a bone
  • Types of bone fractures
    • Closed (simple) fracture – break that does not penetrate the skin
    • Open (compound) fracture – broken bone penetrates through the skin
  • Bone fractures are treated  by reduction and immobilization
    • Realignment of the bone

Dislocation of joint

       Displacement of bones at the joint

       Often caused by impact trauma to that joint

       Can be more damaging and painful than a fracture

       Damage to the joint capsule and surrounding ligaments and tendons often takes much longer to heal than bone tissue.

Repair of Bone Fractures

  • Hematoma (blood-filled swelling) is formed
  • Break is splinted by fibrocartilage to form a soft callus
    • Blood vessels grow into the hematoma
  • Fibrocartilage callus is replaced by a bony callus
  • Bony callus is remodeled to form a permanent patch

Skeletal System

Divided into two divisions

Axial skeleton ~ bones of the cranium, face, vertebral column, and bony thorax.

Appendicular skeleton ~ includes the bones of the pelvic girdles, the upper extremities and lower extremities.

The Axial Skeleton 

  • Forms the longitudinal part of the body
  • Divided into three parts
    • Skull
    • Vertebral column
    • Bony thorax

The Skull (28 bones) (18 names!)

  • Sits on top of the vertebral column
  • Two sets of bones
    • Cranium (8 bones)
    • Facial bones (14 bones)
  • Bones are joined by sutures
  • Only the mandible is attached by a freely movable joint

The Cranium

       Bony structure that encases and protects the brain.

       8 bones

       Frontal Bone ~ forehead/upper part of the bony structure surrounding the eyes.

       Parietal Bone (2) ~ upper sides of the head and the roof of the cranial cavity (top of the head)

       Temporal Bones (2) ~ sides of the head, close to ears.

       Commonly called the temples

       Includes the external auditory meatus

       Opening for the ear

       Includes the zygomatic process

       Part of the cheekbone

       Occipital Bone ~ back and base of the cranium

       Includes the foramen magnum

       Foramen means hole

       Large hole for the brainstem/spinal cord

       Sphenoid Bone ~ forms sides of cranium and parts of orbits of the eyes

       Butterfly shaped

       Includes Sella Turcica (Turk’s Saddle)

       Where pituitary gland sits

       Ethmoid Bone ~ irregularly shaped bone located between the eye orbits

       Major supporting bone of the nasal cavity

       That’s it!  No more cranium bones!

       206 bones - 8 bones = 198 bones to go…

Facial Bones

       14 bones

       Most of these bones come in pairs

       Only the mandible and vomer are single bones

       Mandible ~ the lower jaw bone

       Carries the lower teeth

       The anterior portion forms the chin

       Only freely movable joint in the skull

       Maxilla (2) ~ Upper jaw

       Two bones fused together

       Roof of the mouth

       Also form parts of the nasal cavity and eye orbits

       Palantine Bones (2) ~ form the posterior part of the hard palate and the floor of the nasal cavity.

       Failure of the palatine and/or maxillary bones to fuse causes a cleft palate.

       Zygomatic Bones (2) ~ the cheekbones

       Also forms a part of the orbits of the eyes

       Other Facial Bones

                      Lacrimal Bones (2) ~ inner wall of eye sockets

                      Nasal Bones (2) ~ bridge of nose

                      Vomer ~ nasal septum

                      Inferior Nasal Conchae (2)

       That’s it!  No more facial bones!

       198 bones - 14 bones = 184 bones to go…

Paranasal Sinuses

  • Functions of paranasal sinuses
  • Air filled cavities
    • Lighten the skull
    • Give resonance and amplification to voice

The Fetal Skull

  • The fetal skull is large compared to the infants total body length
  • Fontanelles – fibrous membranes connecting the cranial bones
    • Allow the brain
      to grow
    • Convert to bone within 24 months after birth

The Hyoid Bone

  • U shaped
  • Found in the upper neck
  • The only bone that does not articulate with another bone
  • Serves as a moveable base for the tongue

Middle Ear

       3 Tiny bones ~ transmit vibrations

       All derived from Latin words

       Malleus (hammer)

       Incus (anvil)

       Stapes (stirrup)

       Smallest bone in the body

Middle Ear and Hyoid Bones

       That’s it!

       184 bones - 4 bones = 180 bones to go…

The Vertebral Column

       The backbone or spine

       Consists of 26 bones called vertebrae

       Vertebrae separated by intervertebral discs (act as shock absorbers)

       The spine has a normal curvature

       Each vertebrae is given a name according to its location

       C1-C7 ~ in the neck region

       7 cervical vertebrae

       T1-T12 ~ located in the chest region

       12 thoracic vertebrae

       L1-L5 ~ located in the lower back

       5 lumbar vertebrae

       Sacrum ~ curved bone of the lower back (posterior wall of the pelvis)

       fused sacral vertebrae

       5 vertebrae at birth

       Coccyx ~ the tailbone

       4 vertebrae at birth

       The vertebrae become larger as the vertebral column descends…..WHY?

       Vertebral foramen ~ opening for spinal cord.

       What is the opening for the spinal cord in the skull called?

       180 bones - 26 vertebral column bones = 154 bones to go!

The Bony Thorax (Thoracic Cage)

  • The chest region
  • Forms a cage to protect major organs
  • Composed of sternum, ribs and thoracic vertebrae.
  • Sternum ~ breastbone.
  • Dagger-shaped bone located along the midline of the anterior chest.
  • Ribs ~ 12 pairs of ribs attach posteriorly to the thoracic vertebrae
  • True ribs ~ first 7 pair
  • False ribs ~ last 5 pairs

That is it for the axial skeleton!

       154 bones - 24 ribs -1 sternum = 129 bones to go!!!


The Appendicular Skeleton

  • Limbs (appendages)
  • Pectoral (shoulder) girdle
  • Pelvic girdle

The Pectoral (Shoulder) Girdle

  • Composed of two bones
    • Clavicle – collarbone
    • Scapula – shoulder blade
  • These bones allow the upper limb to have exceptionally free movement

Bones of the Upper Limb

  • The arm is formed by a single bone
    • Humerus
    • Head of humerus allows for rotation
  • The forearm has two bones
    • Ulna
    • Radius


       Radius ~ locate on the lateral or thumb side when the palm of the hand is facing forward.


       Ulna~ the longer of the two forearm bones.

       Located on the medial or little finger side of the forearm.

Bones of the Upper Limb

  • The hand
    • Carpals – wrist
    • Metacarpals – palm
    • Phalanges – fingers

Bones of the Pelvic Girdle

  • Composed of two coxal bones (hip bones)
    • Composed of three pair of fused bones
      • Ilium
      • Ischium
      • Pubis
  • The total weight of the upper body rests on the pelvis
  • Protects several organs
    • Reproductive organs
    • Urinary bladder
    • Part of the large intestine

Bones of the Lower Limbs

  • The thigh has one bone
    • Femur – thigh bone
  • Patella ~ knee cap
  • Triangular bone located within a tendon that passes over the knee.
  • The leg has two bones
    • Tibia ~ shin bone
      • larger
    • Fibula
      • Long and thin
  • The foot
    • Tarsal (7)– ankle
    • Metatarsals (5)– sole/instep
    • Phalanges (14) – toes


  • Articulations of bones
  • Functions of joints
    • Hold bones together
    • Provide flexibility
  • Ways joints are classified
    • By their function
    • By their structure

Functional Classification of Joints

  • Synarthroses – immovable joints
  • Amphiarthroses – slightly moveable joints
  • Diarthroses – freely moveable joints

Structural Classification of Joints

  • Fibrous joints
    • Generally immovable
  • Cartilaginous joints
    • Immovable or slightly moveable
  • Synovial joints
    • Freely moveable

Fibrous Joints

  • Bones united by fibrous tissue – synarthrosis or largely immovable.

Cartilaginous Joints – mostly amphiarthrosis

  • Bones connected by cartilage
  • Examples
    • Pubic
    • Intervertebral

Synovial Joints

  • Articulating bones are separated by a joint cavity
  • Synovial fluid is found in the joint cavity
  • Reinforced by ligaments
  • 6 Types of Synovial Joints

Hinge joint

·         Movement is like two boards joined together by a hinge

·         Movement in one direction

·         Elbow, knees, fingers

Ball and Socket Joint

·         When ball-shaped end of one bone fits into the cup-shaped socket of another

·         Bones can move in many directions

·         Shoulder, hip

Pivot Joint

·         Allows for rotation around the length of a bone.

·         Allows only for rotation

·         Head (side to side “no” action)

·         Forearm joints (palms) supination/pronation

Saddle Joint

·         When the surfaces of both articulation bones are saddle-shaped              

·         Concave/convex

·         Thumb

·         Wide range of motion

Gliding Joint

·         Interaction of flat surfaces of articulating bones

·         Limited but complex movement

·         Wrist, ankle

Condyloid Joint

·         Oval-shaped articular surface of one bone fits into the oval-shaped depression of another

·         Mandible, knuckles

Inflammatory Conditions Associated with Joints

  • Bursitis – inflammation of a bursa usually caused by a blow or friction
  • Tendonitis – inflammation of tendon sheaths
  • Arthritis – inflammatory or degenerative diseases of joints
    • Over 100 different types
    • The most widespread crippling disease in the United States

Clinical Forms of Arthritis

  • Osteoarthritis
    • Most common chronic arthritis
    • Probably related to normal aging processes
  • Rheumatoid arthritis
    • An autoimmune disease – the immune system attacks the joints
    • Symptoms begin with bilateral inflammation of certain joints
    • Often leads to deformities
  • Gouty Arthritis
    • Inflammation of joints is caused by a deposition of urate crystals from the blood
    • Can usually be controlled with diet
      • Red meat and wine are high in uric acid.

 The Skeletal System PDF

The Skeletal System PPT



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