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Chapter 7

Skeletal System

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Outline• Tissues of the Skeletal System• Bone Growth and Repair• Bone Development• Bone Repair• Bones of the Skeleton

– Bone Classification– Axial and Appendicular Skeleton

• Articulation• Movements Permitted by Joints

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Tissues of the Skeletal System

• Bone.– Compact bone is highly organized and

composed of tubular osteons.Osteocytes lie in lacunae, tiny chambers

arranged in concentric circles around a central canal.

– Spongy bone contains numerous plates (trabeculae) separated by unequal spaces.

Spaces are often filled with red bone marrow.

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Tissues of the Skeletal System

• Cartilage– Cartilage is flexible because the gel-like

matrix contains collagenous and elastic fibers.

– Three types differ according to type and arrangement of fibers.

Hyaline - Firm and flexible.Fibrocartilage - Strong.Elastic - Flexible.

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Tissues of the Skeletal System

• Fibrous Connective Tissue– Made of rows of fibroblasts separated by

bundles of collagenous fibers.Makes up ligaments (connect bone to

bone) and tendons (connect muscles to bones at joints).

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Bone Growth and Repair

• Several different types of cells are involved in bone growth and repair.– Osteoprogenitor cells.– Osteoblasts.– Osteocytes.– Osteoclasts.

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Bone Development and Growth

• Ossification refers to bone formation.– Intramembranous ossification - Bones

develop between sheets of fibrous tissue.– Endochondral ossification - Cartilage

breaks down in the center of the diaphysis.• After birth, the ends of developing bones

continue to grow, but secondary ossification centers soon appear.– Growth plate remains between primary and

secondary ossification centers.

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Endochondral Ossification

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Remodeling of Bones

• Osteoclasts derived from monocytes in red bone marrow break down bone, remove worn cells, and assist in depositing calcium in the blood.– Osteoblasts take calcium from blood and

form new bone.

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Bone Repair

• Fracture repair takes place over a span of several months in a series of four steps.– Hematoma.– Fibrocartilaginous callus.– Bony callus.– Remodeling.

• Naming of a fracture indicates what kind of break occurred. (types)

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Bone Fracture and Repair

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Bones of the Skeleton

• Skeletal Functions.– Support body.– Protect soft body parts.– Produce blood cells.– Store minerals and fat.– Permit flexible body movement.

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Bone Classification

• Bones are classified according to their shape, and whether they occur in the axial skeleton or the appendicular skeleton.– Axial - Midline.– Appendicular - Limbs and their girdles.

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The Axial Skeleton

• The axial skeleton lies in the midline of the body and consists of:– Skull.– Hyoid bone.– Vertebral column.– Rib cage.

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The Skull

• The skull is formed by the cranium and the facial bones.– The cranium contain eight bones.

Frontal boneTwo parietal bones.Occipital bone.Two temporal bones.Sphenoid bone.Ethmoid bone.

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Bones of the Skull

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The Facial Bones

• The most prominent facial bones are the mandible, maxillae, zygomatic bones, and nasal bones.– Mandible is the movable, lower jaw.– Maxillae form upper jaw.– Zygomatic bones form cheek prominence.– Nasal bones form the bridge of the nose.

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Bones of the Face

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Hyoid Bone

• The hyoid bone is not part of the skull, but is part of the axial skeleton.– Only bone that does not articulate with

another bone.

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The Vertebral Column

• Column made of thirty-three vertebrae.• Spinal cord passes through the vertebral

canal and gives off spinal nerves.• Vertebrae named according to location.

– Cervical. – Thoracic.– Lumbar.– Sacrum.– Coccyx.

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The Vertebral Column

• Intervertebral disks composed of fibrocartilage are found between the vertebrae and provide padding to absorb shock caused by movements and also provide flexibility of the column.

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The Rib Cage

• The rib cage is composed of the thoracic vertebrae, ribs and associated cartilage, and the sternum.– Twelve pairs of ribs.

All connect to thoracic vertebrae in back.Upper seven pairs (true ribs) connect to

sternum by costal cartilage.Next three pairs (false ribs) attach to

sternum by common cartilage.Last two pairs (floating ribs)do not attach

to sternum.

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Thoracic Vertebrae and Rib Cage

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The Appendicular Skeleton

• The appendicular skeleton consists of bones within the pectoral and pelvic girdles and their attached limbs.– The pectoral girdle and upper limb (arm)

are specialized for flexibility.

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Bones of Pectoral Girdle and Arm

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The Appendicular Skeleton

• The Pelvic Girdle and Lower Limb.– The pelvis is a basin composed of the

pelvic girdle, sacrum, and coccyx.Pelvis bears the weight of the body,

protects organs within the pelvic cavity, and serves as attachment point for the legs.

Femur is the longest and strongest bone in the body.

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Bones of the Lower Limb

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Articulations

• Bones are joined at joints.– Cartilaginous joints are connected by

hyaline cartilage.– Synovial joints separate the bones by a

cavity.Hinge.

2 direction movementBall-and-socket.

Full rotation movement

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Knee Joint

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Movements Permitted by Synovial Joints

• Angular Movements.– Flexion - Decreases joint angle.– Extension - Increases joint angle.– Adduction - Movement towards midline.– Abduction - Movement away from midline.

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Movements Permitted by Synovial Joints

• Circular Movements.– Rotation - Movement around axis.– Supination - Rotation with palm upward.– Circumduction - Movement in wide circle.

• Special Movements.– Inversion (sole inward) and eversion (sole

outward).– Elevation (lifting up) and depression

(moving down).

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Joint Movements

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Homeostasis

• Rib cage enables oxygen to enter bloodstream.

• Red bone marrow produces red and white blood cells.

• Jaw and teeth chew food, aiding digestion.• Bones protect internal organs.• Calcium storage.• Efficient locomotion.

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Review• Tissues of the Skeletal System• Bone Growth and Repair• Bone Development• Bone Repair• Bones of the Skeleton

– Bone Classification– Axial and Appendicular Skeleton

• Articulation• Movements Permitted by Joints