Chapter 6 The Skeletal System

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Chapter 6 The Skeletal System

• Bones and Cartilage

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Summary

• Structure
• Functions
• Growth
• Embryonic
• Factors that affect bone growth and maintenance
• Types of bones
• Divisions of the skeleton
• Joints/articulations

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Structure

• There are a total of 206 bones in the human body.
• The skeletal system contains both bone and
  cartilage 2 types of connective tissue.
• The appearance and texture of bone varies,
  depending on its location.

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Structure

• Compact Bone
• Outer layer of bone, very hard and dense.
• Organized in structural units called Haversian
  systems.
• Matrix is composed of Ca salts (Ca carbonate and
  Ca phosphate)
• Osteocytes living bone cells that live in
  matrix.

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Structure

• Porous (Spongy) bone
• Located in the ends of long bones.
• Many spaces that are filled with red bone marrow
  which produces blood cells.
• Trabeculae needle-like threads of spongy bone
  that surround the spaces. Add strength to this
  portion of the bone.

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Structure

• Cartilage
• Matrix is a firm gel with chondrocytes suspended
  in the matrix.

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Functions

• Provides framework that supports the body.
• Protection
• Provides movement with the help of the skeletal
  muscles.
• Storage of calcium
• Produces blood cells

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Embryonic Bone Growth

• The skeleton is first made of cartilage and
  fibrous connective tissue. These are gradually
  replaced by bone.
• Bone matrix is produced by osteoblasts.
• Calcification begins at 8 weeks gestation.
• Process is not complete at birth.

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Factors that Affect Bone Growth and Maintenance

• Heredity
• Nutrition

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Factors that Affect Bone Growth and Maintenance

• Hormones growth hormone, thyroxine, parathyroid
  hormone and insulin help regulate cell division,
  protein synthesis, Ca metabolism and energy
  production.
• Exercise or stress bearing weight causes
  bones to thicken.

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4 Types of Bones

• Long bones bones of the arms and legs.
  Structure
• Diaphysis
• Medullary cavity

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4 Types of Bones

• Long bones contd
• Epiphysis
• Composed of spongy bone which contains red bone
  marrow in children, replaced with yellow marrow
  in adults.
• Epiphyses are covered with compact bone which in
  turn is covered with articular (hyaline)
  cartilage.
• Periosteum
• Endosteum

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4 Types of Bones

• Short bones carpels and tarsals (wrist and
  ankle).
• Flat bones skull bones.
• Irregular bones vertebrae.

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Divisions of the Skeleton

• Axial Skeleton bones of the skull, spine, chest
  and the hyoid bone.
• Skull 8 bones that form the cranium, 14 that
  form the face and 6 in the middle ears.
• Frontal forehead bone, also forms upper part of
  eye sockets.
• Parietal top/upper sides of the cranium behind
  the frontal bone
• Temporal forms the lower sides of the cranium
  contains middle and inner ear structures,
  external auditory canal, and mastoid process
  (behind the ear).

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Divisions of the Skeleton

• Axial skull
• Cranium
• Occipital bone - forms the back of the skull,
  large hole (foramen magnum) allows entry of
  spinal cord.
• Sphenoid forms central part of the floor of the
  cranium pituitary gland is located in a
  depression called the sella turcica (Turkish
  sadle).
• Ethmoid bone helps form floor of cranium, side
  walls and roof of nose.
• Nasal bones form upper bridge of nose.

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Divisions of the Skeleton

• Axial - skull
• Face
• Maxilla upper jawbones
• Zygomatic bones cheek bones help form eye
  orbit.
• Mandible lower jawbone.
• Lacrimal bones form medial wall of the eye
  socket and side of nasal cavity.
• Palatine forms back part of the roof of the
  mouth, part of the orbit.
• Vomer forms lower, back part of nasal septum.

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Divisions of the Skeleton

• Axial - skull
• Ear bones from the outside in..
• Malleus hammer
• Incus anvil
• Stapes stirrup
• Sinuses spaces or cavities inside the cranium
• Sutures Immovable joints that join skull bones
  together
• Lamboidal between the parietal and occipital
• Squamous between the parietal and temporal
• Coronal between parietal and frontal
• Sagittal between parietal bones
• Fontanels usually ossify by 2 years of age

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Divisions of the Skeleton

• Vertebral column consists of a series of separate
  bones or vertebrae connected such that they form
  a flexible curved rod.
• 7 Cervical vertebrae - Atlas and axis are first
  two vertebrae
• 12 Thoracic
• 5 Lumbar
• Sacrum
• Coccyx

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Divisions of the Skeletal System

• Axial Vertebral column
• Vertebral column has 4 curves that support the
  weight of the body and help with balance.
• Cervical curvature curves anteriorly
• Thoracic curvature curve posteriorly
• Lumbar curvature anteriorly
• Sacral posteriorly

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Divisions of the Skeletal System

• Axial Vertebral column
• Abnormal curves
• Kyphosis (thoracic) exagerated curve
• Lodosis (lumbar) exagerated curve
• Scoliosis lateral curve.

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Divisions of the Skeletal System

• Axial Thorax
• Includes manubrium, sternum, thoracic vertebrae
  and the ribs.
• All 12 ribs are all attached posteriorly to the
  vertebrae
• True ribs - 1st 7 pair are attached to the
  sternum by the costal cartilage beginning at the
  manubrium (upper part of the sternum).
• False ribs ribs 8, 9, and 10 are attached to
  the cartilage of the 7th ribs.
• Floating ribs last 2 pairs are not attached at
  the anterior end.

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Divisions of the Skeletal System

• Appendicular skeleton bones of the upper and
  lower extremities and their girdles.
• Upper extremity
• Scapula shoulder blade
• Clavicle collar bone
• Humerus long bone of the upper arm 2nd longest
  bone in the body. The humerus is attached to the
  scapula proximally and articulates with the
  radius and ulna distally to form the elbow joint.

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Divisions of the Skeletal System

• Appendicular skeleton - Upper Extremity contd
• Radius and ulna bones of the lower arm,
  articulate with each other distally and with the
  carpals.
• Carpals 8 wrist bones
• Metacarpals palm of hand
• Phalanges 14 finger bones, 3 in each finger and
  2 in each thumb.

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Divisions of the Skeletal System

• Appendicular skeleton - Lower extremity
• Pelvic (hip) girdle connects legs to the trunk.
  Consists of 2 large os coxae one on each side of
  the pelvis. Each os coxae consists of 3 separate
  bones in the infant
• Ilium
• Ischium
• Pubis These grow together in the adult.

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Divisions of the Skeletal System

• Appendicular skeleton Lower extremity
• Femur thigh bone, longest bone in the body.
  The femur fits into the cup-shaped socket
  acetabulum in the pelvic girdle. Distally the
  femur articulates with the patella (knee cap) and
  the
• Tibia (lower leg - shinbone).
• Medial malleolus inner anklebone, protuberance
  of the tibia.
• Fibula long slender, non-weight bearing bone
  located along the lateral border of the lower
  leg.

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Divisions of the Skeletal System

• Appendicular skeleton Lower extremity
• Lateral Malleolus rounded projection at the
  lower end of the fibula (outer anklebone)
• Tarsals 7 ankle bones the talus articulates
  with the tibia and the calcaneous, the heel bone.
• Metatarsals 5 long bones of the foot.
• Phalanges - toe bones, two in the big toe and
  3 in each of the other toes.

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Joints Articulations

• Three types of joints synarthroses,
  amphiarthroses and diarthroses
• Synarthroses
• Amphiarthroses

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Joints Articulations

• Diarthroses freely moveable joints.
• All have a joint capsule, a joint cavity and a
  layer of cartilage over the ends of the adjoining
  bones.
• Joint Capsule made of tough fibrous connective
  tissue and lined with the smooth slippery
  synovial membrane fits over the ends of the
  bones like a sleeve.
• Ligaments cords or bands of fibrous connective
  tissue that hold the bones together firmly.

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Joints Articulations

• Diarthroses contd
• Joint structure contd
• Articular cartilage layer of cartilage over the
  end of the bones.
• Synovial membrane secretes a lubricating fluid
  (synovial fluid) that allows easier movement with
  less friction.

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Joints Articulations

• Types of Diarthroses
• Ball and Socket ball like head on one bone fits
  into a socket of another. Ex shoulder and hip.
  Widest range of movement.
• Hinge allow movements in only 2 directions
  flexion and extension. Ex elbow and knee,
  fingers.
• Pivot small projection of one bone pivots in an
  arch of another. Ex atlas and axis.

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Joints Articulations

• Types of Diartroses
• Saddle or saddle-shaped allows for flexion,
  extension, abduction, adduction, opposition.
  Only example metacarpal bone of thumb and a
  carpal bone of the wrist.
• Gliding least moveable, flat articulating
  surfaces. Ex carpals.
• Condyloid distal end of radius into the
  depressions in the carpals.

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