NR 283 PATHO FINAL EXAM 3 STUDY GUIDE
(LATEST)
Chapter 9
Bone- Types of bone tissue
Bone tissue consists of two types, which differ in density.
Compact bone is formed when many Haversian systems are tightly packed
together, producing a very strong, rigid structure that forms the outer covering of
bones.
Cancellous or spongy bone is less dense and forms the interior structure of bones.
Spongy bone lacks Haversian systems but is made up of plates of bonebordering
cavities that contain marrow.
A typical long bone consists of the diaphysis, a thin shaft, between two larger ends
or epiphyses (see Fig. 9-1B). The diaphysis is formed of
compact bone surrounding a medullary cavity containing marrow.
The metaphysis is the area where the shaft broadens into the epiphysis. The
epiphysis is made up of spongy bone covered by compact bone. The end of each
epiphysis is covered by hyaline cartilage (articular cartilage), which facilitates
movement at points of articulation between bones.
The epiphyseal cartilage or plate (“growth” plate) is the site of
longitudinal bone growth in children and adolescents, such growth being promoted
by growth hormone and sex hormones. Longitudinal bone growth ceases when the
epiphyseal plate ossifies during adolescence or early adulthood depending on the
specific bone.
The epiphyseal plate is referred to as the epiphyseal line following ossification or
closure. No bone growth in length occurs after the epiphyseal plate becomes the
epiphyseal line.
However, bone may change in density or thickness at any time under the influence
of hormones such as growth hormone, parathyroid hormone, or cortisol. The stress
(weight-bearing or muscle tension) placed on the bone also affects the balance
between osteoblastic and osteoclastic activity. With aging, bone loss is
,accentuated, resulting in decreased bone mass and density. Osteoporosis, loss
of bone density due to loss of calcium salts, is common in older people,
particularly women (see Chapter 24). Except for the surface of the bone covered by
articular cartilage, the bone is covered by periosteum, a fibrous connective tissue.
The periosteum contains osteoblasts, blood vessels, nerves, and lymphatics, some
of which penetrate into the canals in the bone. When the periosteum is stretched or
torn, severe pain results.
The medullary cavity is lined with endosteum, also containing osteoblasts. These
osteoblasts are required for bone repair and remodeling as needed. At birth the
medullary cavity in most bones contains red bone marrow in
which hematopoiesis takes place. Gradually, yellow (fatty) bonemarrow replaces
red bone marrow in the long bones. In adults, red bone marrow is found in the
cranium, bodies of the vertebrae, ribs, sternum, and ilia, the last two being the
usual sites of bonemarrow aspiration used in the diagnosis and monitoring of
leukemias and blood dyscrasias.
Joints
Joints or articulations between bones vary in the degree of movement allowed:
•Synarthroses, represented by the sutures in the skull, are immovable joints.
•Amphiarthroses, slightly movable joints, are joints in which the bones are
connected by fibrocartilage or hyaline cartilage. Examples of this type of joint
include the junction of the ribs and sternum and the symphysis pubis.
•Diarthroses or synovial joints are freely movable joints and are the most common
type of joint in the body.
Different types of diarthroses allow a variety of movements. For example, a hinge
joint, providing flexion and extension, is found at the elbow, whereas a ball-and-
socket joint at the shoulder provides a wide range of motion, including rotation.
Both hinge and gliding movements are found in the temporomandibular joint
(TMJ), controlling the opening of the mouth. Common body movements are
illustrated in Ready Reference 1 (see Fig. RR1-6).
In a synovial joint, the ends of the bone are covered
with articular (hyaline) cartilage, providing a smooth surface and a slight cushion
during movement (see Fig. 9-13A). With aging, the cartilage in joints tends to
degenerate and become thin, leading to difficulty with movement and potential
changes in the alignment of bones.
,The joint cavity or space between the articulating ends of the bones is filled with a
small amount of synovial fluid, which facilitates movement. The synovial fluid
prevents the articular cartilage on the two surfaces from damaging each other and
also provides nutrients to the articular cartilage. The synovial fluid is produced by
the synovial membrane (synovium), which lines the joint capsule to the edge of the
articular cartilages. The synovial membrane is well supplied with blood vessels.
The articular capsule is composed of the synovial membrane and its outer
covering, the fibrous capsule, a tough protective material that extends into the
periosteum of each articulating bone (Sharpey's fibers). The capsule is reinforced
by ligaments, straps across the joint that link the two bones, which support the joint
and prevent excessive movement of the bones.
In a few joints there are some variations in structure. The knee has additional
moon-shaped fibrocartilage pads, termed lateral and medial menisci, which act to
stabilize the joint. Bursae are fluid-filled sacs composed of synovial membrane and
located between structures such as tendons and ligaments; they act as additional
cushions in the joint. The TMJ, the only movable joint in the skull and face, has
two synovial cavities and a central articular cartilage of dense collagen tissue.
Open or compound fractures
•Complete-incomplete. A complete fracture occurs when the bone is broken to
form two or more separate pieces, whereas in an incomplete fracture the bone is
only partially broken. An example of the latter is a greenstick fracture, common in
the softer bones of children, in which the shaft of the bone is bent, tearing the
cortical bone (outer layer of compact bone) on one side but not extending all the
way through the bone.
•Open-closed. An open or compound fracture results when the skin is broken (Fig.
9-4). The bone fragments may be angled and protrude through the skin. In
open fractures there is more damage to soft tissue, including the blood vessels and
nerves, and there is also a much higher risk of infection. In a closed fracture the
skin is not broken at the fracture site.
•Number of fracture lines:
•Simple fracture, a single break in the bone in which the bone ends maintain their
alignment and position
•Comminuted fracture, in which there are multiple fracture lines and bone
fragments
, •Compression fracture, common in the vertebrae, occurring when a bone is crushed
or collapses into small pieces
•Other types:
•Impacted fracture occurs when one end of the bone is forced or telescoped into the
adjacent bone; for example, the neck of the femur is crushed against the pelvis.
•Pathologic fracture results from a weakness in the bone structure due to conditions
such as a tumor or osteoporosis. The break occurs spontaneously or with very little
stress on the bone.
•Stress fractures (fatigue fractures) result from repeated excessive stress,
commonly in the tibia, femur, or second and third metatarsals.
•Depressed fracture occurs in the skull when the broken section is forced inward on
the brain.
•Direction of the fracture line; for example:
•A fracture across the bone is a transverse fracture.
•A break along the axis of the bone is a linear fracture.
•A break at an angle to the diaphysis of the bone is an oblique fracture.
•A break that angles around the bone, usually due to a twisting injury, is
a spiral fracture.
•Unique names for certain types of fractures; for example:
•Colles' fracture is a break in the distal radius at the wrist, commonly occurring
when a person attempts to break a fall by extending the arm and open hand.
Sometimes the ulna is also damaged.
•Pott's fracture refers to a fracture of the lower fibula due to excessive stress on the
ankle; for example, when stepping down with force. The tibia may be damaged as
well.
Pathophysiology
When a bone breaks, bleeding occurs from the blood vessels in the bone and
periosteum. Bleeding and inflammation also develop around the bone because of
(LATEST)
Chapter 9
Bone- Types of bone tissue
Bone tissue consists of two types, which differ in density.
Compact bone is formed when many Haversian systems are tightly packed
together, producing a very strong, rigid structure that forms the outer covering of
bones.
Cancellous or spongy bone is less dense and forms the interior structure of bones.
Spongy bone lacks Haversian systems but is made up of plates of bonebordering
cavities that contain marrow.
A typical long bone consists of the diaphysis, a thin shaft, between two larger ends
or epiphyses (see Fig. 9-1B). The diaphysis is formed of
compact bone surrounding a medullary cavity containing marrow.
The metaphysis is the area where the shaft broadens into the epiphysis. The
epiphysis is made up of spongy bone covered by compact bone. The end of each
epiphysis is covered by hyaline cartilage (articular cartilage), which facilitates
movement at points of articulation between bones.
The epiphyseal cartilage or plate (“growth” plate) is the site of
longitudinal bone growth in children and adolescents, such growth being promoted
by growth hormone and sex hormones. Longitudinal bone growth ceases when the
epiphyseal plate ossifies during adolescence or early adulthood depending on the
specific bone.
The epiphyseal plate is referred to as the epiphyseal line following ossification or
closure. No bone growth in length occurs after the epiphyseal plate becomes the
epiphyseal line.
However, bone may change in density or thickness at any time under the influence
of hormones such as growth hormone, parathyroid hormone, or cortisol. The stress
(weight-bearing or muscle tension) placed on the bone also affects the balance
between osteoblastic and osteoclastic activity. With aging, bone loss is
,accentuated, resulting in decreased bone mass and density. Osteoporosis, loss
of bone density due to loss of calcium salts, is common in older people,
particularly women (see Chapter 24). Except for the surface of the bone covered by
articular cartilage, the bone is covered by periosteum, a fibrous connective tissue.
The periosteum contains osteoblasts, blood vessels, nerves, and lymphatics, some
of which penetrate into the canals in the bone. When the periosteum is stretched or
torn, severe pain results.
The medullary cavity is lined with endosteum, also containing osteoblasts. These
osteoblasts are required for bone repair and remodeling as needed. At birth the
medullary cavity in most bones contains red bone marrow in
which hematopoiesis takes place. Gradually, yellow (fatty) bonemarrow replaces
red bone marrow in the long bones. In adults, red bone marrow is found in the
cranium, bodies of the vertebrae, ribs, sternum, and ilia, the last two being the
usual sites of bonemarrow aspiration used in the diagnosis and monitoring of
leukemias and blood dyscrasias.
Joints
Joints or articulations between bones vary in the degree of movement allowed:
•Synarthroses, represented by the sutures in the skull, are immovable joints.
•Amphiarthroses, slightly movable joints, are joints in which the bones are
connected by fibrocartilage or hyaline cartilage. Examples of this type of joint
include the junction of the ribs and sternum and the symphysis pubis.
•Diarthroses or synovial joints are freely movable joints and are the most common
type of joint in the body.
Different types of diarthroses allow a variety of movements. For example, a hinge
joint, providing flexion and extension, is found at the elbow, whereas a ball-and-
socket joint at the shoulder provides a wide range of motion, including rotation.
Both hinge and gliding movements are found in the temporomandibular joint
(TMJ), controlling the opening of the mouth. Common body movements are
illustrated in Ready Reference 1 (see Fig. RR1-6).
In a synovial joint, the ends of the bone are covered
with articular (hyaline) cartilage, providing a smooth surface and a slight cushion
during movement (see Fig. 9-13A). With aging, the cartilage in joints tends to
degenerate and become thin, leading to difficulty with movement and potential
changes in the alignment of bones.
,The joint cavity or space between the articulating ends of the bones is filled with a
small amount of synovial fluid, which facilitates movement. The synovial fluid
prevents the articular cartilage on the two surfaces from damaging each other and
also provides nutrients to the articular cartilage. The synovial fluid is produced by
the synovial membrane (synovium), which lines the joint capsule to the edge of the
articular cartilages. The synovial membrane is well supplied with blood vessels.
The articular capsule is composed of the synovial membrane and its outer
covering, the fibrous capsule, a tough protective material that extends into the
periosteum of each articulating bone (Sharpey's fibers). The capsule is reinforced
by ligaments, straps across the joint that link the two bones, which support the joint
and prevent excessive movement of the bones.
In a few joints there are some variations in structure. The knee has additional
moon-shaped fibrocartilage pads, termed lateral and medial menisci, which act to
stabilize the joint. Bursae are fluid-filled sacs composed of synovial membrane and
located between structures such as tendons and ligaments; they act as additional
cushions in the joint. The TMJ, the only movable joint in the skull and face, has
two synovial cavities and a central articular cartilage of dense collagen tissue.
Open or compound fractures
•Complete-incomplete. A complete fracture occurs when the bone is broken to
form two or more separate pieces, whereas in an incomplete fracture the bone is
only partially broken. An example of the latter is a greenstick fracture, common in
the softer bones of children, in which the shaft of the bone is bent, tearing the
cortical bone (outer layer of compact bone) on one side but not extending all the
way through the bone.
•Open-closed. An open or compound fracture results when the skin is broken (Fig.
9-4). The bone fragments may be angled and protrude through the skin. In
open fractures there is more damage to soft tissue, including the blood vessels and
nerves, and there is also a much higher risk of infection. In a closed fracture the
skin is not broken at the fracture site.
•Number of fracture lines:
•Simple fracture, a single break in the bone in which the bone ends maintain their
alignment and position
•Comminuted fracture, in which there are multiple fracture lines and bone
fragments
, •Compression fracture, common in the vertebrae, occurring when a bone is crushed
or collapses into small pieces
•Other types:
•Impacted fracture occurs when one end of the bone is forced or telescoped into the
adjacent bone; for example, the neck of the femur is crushed against the pelvis.
•Pathologic fracture results from a weakness in the bone structure due to conditions
such as a tumor or osteoporosis. The break occurs spontaneously or with very little
stress on the bone.
•Stress fractures (fatigue fractures) result from repeated excessive stress,
commonly in the tibia, femur, or second and third metatarsals.
•Depressed fracture occurs in the skull when the broken section is forced inward on
the brain.
•Direction of the fracture line; for example:
•A fracture across the bone is a transverse fracture.
•A break along the axis of the bone is a linear fracture.
•A break at an angle to the diaphysis of the bone is an oblique fracture.
•A break that angles around the bone, usually due to a twisting injury, is
a spiral fracture.
•Unique names for certain types of fractures; for example:
•Colles' fracture is a break in the distal radius at the wrist, commonly occurring
when a person attempts to break a fall by extending the arm and open hand.
Sometimes the ulna is also damaged.
•Pott's fracture refers to a fracture of the lower fibula due to excessive stress on the
ankle; for example, when stepping down with force. The tibia may be damaged as
well.
Pathophysiology
When a bone breaks, bleeding occurs from the blood vessels in the bone and
periosteum. Bleeding and inflammation also develop around the bone because of
