Download PowerPoint Sunusu - Yeditepe University Faculty of Medicine 1st

GENERAL CONSIDERATIONS ON
BONES & JOINTS
Kaan Yücel M.D., Ph.D.
21. September 2011 Wednesday
GENERAL CONSIDERATIONS ON BONES
Osteology (Gk, osteon, bone, logos, science) is the branch of
medicine concerned with the development and diseases of bone
tissue.
The human skeleton
270 bones in the newborn
222 bones in children
206 bones in adults
Why Humans Have 270 Bones at Birth, but Only 206 Bones Once
We are Adults
Including the hyoid bone (os hyoideum) and the three auditory
ossicles (malleus, incus and stapes) on each side, the head
(caput) has 29 bones. The vertebral column (columna vertebralis)
has 26 bones. Thorax (chest) is composed of 25 bones. The
number of the upper limb/extremity bones (ossa membri
superirois) is 64, whereas that of the lower limb/extremity is 62.
The skeletal system may be divided into
2 functional parts:
The axial skeleton
• head (cranium or skull)
• neck (hyoid bone and cervical vertebrae)
• trunk (ribs, sternum, vertebrae, and sacrum)
The appendicular skeleton
• Limbs
including those forming the shoulde & pelvic girdles
126 bones in the appendicular skeleton
80 bones in the axial skeleton
 Bone is a living tissue capable of changing its structure as the
result of the stresses to which it is subjected.
 Like other connective tissues, bone consists of cells, fibers, and
matrix.
 It is one of the hardest structures of the animal body, because of
the calcification of its extracellular matrix.
 Living bones have some elasticity (results from the organic
matter) and great rigidity (results from their lamellous structures
and tubes of inorganic calcium phosphate).
 Its color, in a fresh state, is pinkish-white externally, and deep
red within.
Cartilage and Bones
 The skeleton is composed of cartilages and bones.
 Cartilage is a resilient, semirigid form of connective tissue that
forms parts of the skeleton where more flexibility is required—
for example, where the costal cartilages attach the ribs to the
sternum.
Cartilage and Bones
Also, the articulating surfaces (bearing surfaces) of bones
participating in a synovial joint are capped with articular cartilage
that provides smooth, low-friction, gliding surfaces for free
movement.
Cartilage and Bones
 Blood vessels do not enter cartilage (i.e., it is avascular);
consequently, its cells obtain oxygen and nutrients by diffusion.
 The proportion of bone and cartilage in the skeleton changes as the
body grows; the younger a person is, the more cartilage he or she
has.
 The bones of a newborn are soft and flexible because they are
mostly composed of cartilage.
 Bone has a protective function; the skull and vertebral column, for
example, protect the brain and spinal cord from injury.
A fibrous connective tissue covering surrounds each skeletal
element like a sleeve, except where articular cartilage occurs; that
surrounding bones is periosteum, whereas that around cartilage is
perichondrium.
 The periosteum and perichondrium nourish the external aspects of
the skeletal tissue.
 They are capable of laying down more cartilage or bone (particularly
during fracture healing) and provide the interface for attachment of
tendons and ligaments.
Classification of Bones
Bones are classified according to their shape.
1) Long bones
2) Short bones
3) Flat bones
4) Irregular bones
5) Sesamoid bones
Classification of Bones
Long bones are tubular (e.g., the humerus in the arm).
Classification of Bones
Short bones are cuboidal and are found only in the tarsus (ankle) and
carpus (wrist).
Classification of Bones
Flat bones usually serve protective functions (e.g., the flat bones of the
cranium protect the brain).
Classification of Bones
Irregular bones have various shapes other than long, short, or flat (e.g.,
bones of the face).
Classification of Bones
Sesamoid bones (e.g., the patella or knee cap) develop in certain
tendons and are found where tendons cross the ends of long bones in
the limbs; they protect the tendons from excessive wear and often
change the angle of the tendons as they pass to their attachments.
 There are two types of bones according to histological features:
compact bone and spongy (trabecular) bone.
 They are distinguished by the relative amount of solid matter and by
the number and size of the spaces they contain.
 All bones have a superficial thin layer of compact bone around a
central mass of spongy bone, except where the latter is replaced by
a medullary (marrow) cavity.
 Spongy bone is found at the expanded heads of long bones and fills
most irregular bones.
 Compact bone forms the outer shell of all bones and also the shafts
in long bones.
 Spongy or cancellous bone consists of a lattice of thin threads of bone
called trabeculae and is less dense than compact bone.
 The orientation of the trabeculae is modelled by the mechanical stress
to which the bone is exposed (Wolff's law).
 The architecture and proportion of compact and spongy bone vary
according to function.
 Compact bone provides strength for weight bearing.
 In long bones designed for rigidity and attachment of muscles and
ligaments, the amount of compact bone is greatest near the middle
of the shaft where the bones are liable to buckle.
Bone Markings and Formations
 Bone markings appear wherever tendons, ligaments, and fascias are
attached or where arteries lie adjacent to or enter bones.
 Other formations occur in relation to the passage of a tendon (often
to direct the tendon or improve its leverage) or to control the type of
movement occurring at a joint.
Bone Markings and Formations
 Surfaces of the bones are not smooth.
 Bones display elevations, depressions and holes.
 The surface features on the bones are given names to distinguish and
define them.
Some of the various markings and features of bones
 Linear elevation
 line, crest
Some of the various markings and features of bones
 Round elevation
 tubercule (small eminence), protuberance (swelling)
External occipital
protuberance @ CT scan
Some of the various markings and features of bones
 Sharp elevation
 spine, process
Some of the various markings and features of bones
 Rounded articular area
head, condyle
Vasculature and Innervation of Bones
 Bones are richly supplied with blood vessels.
 Most apparent are the nutrient arteries (one or more per bone) that
arise as independent branches of adjacent arteries outside the
periosteum.
Vasculature of Bones
 Veins accompany arteries through the nutrient foramina.
 Many large veins also leave through foramina near the articular ends
of the bones.
 Bones containing red bone marrow have numerous large veins.
 Lymphatic vessels are also abundant in the periosteum.
Innervation of Bones
 Nerves accompany blood vessels supplying bones.
 The periosteum is richly supplied with sensory nerves—periosteal
nerves—that carry pain fibers.
 The periosteum is especially sensitive to tearing or tension, which
explains the acute pain from bone fractures.
Innervation of Bones
 Bone itself is relatively sparsely supplied with sensory endings.
 Within bones, vasomotor nerves cause constriction or dilation of
blood vessels, regulating blood flow through the bone marrow.
Accessory Bones
 Accessory (supernumerary) bones develop when additional
ossification centers appear and form extra bones.
 Many bones develop from several centers of ossification, and the
separate parts normally fuse.
 Sometimes one of these centers fails to fuse with the main bone,
giving the appearance of an extra bone.
 Careful study shows that the apparent extra bone is a missing part
of the main bone.
Heterotopic Bones
 Bones sometimes form in soft tissues where they are not normally
present (e.g., in scars).
 Horse riders often develop heterotopic bones in their thighs
(rider's bones), probably because of chronic muscle strain resulting
in small hemorrhagic (bloody) areas that undergo calcification and
eventual ossification.
Changes in Bones
 Atrophy (decrease in size) might develop in unused bones, such as in
a paralyzed limb.
 Bone may be absorbed, which occurs in the mandible when teeth
are extracted.
 Bones hypertrophy (enlarge) when they support increased weight
for a long period.
Bone Fractures
 Trauma to a bone may break it.
 For the fracture to heal properly, the broken ends must be brought
together, approximating their normal position.
 This is called reduction of a fracture
 Fractures are more common in children than in adults because of
the combination of their slender, growing bones and carefree
activities.
Osteoporosis
 During the aging process, the organic and inorganic components of
bone both decrease, often resulting in osteoporosis, a reduction in
the quantity of bone, or atrophy of skeletal tissue.
 Hence, the bones become brittle, lose their elasticity, and fracture
easily.
 Bone scanning is an imaging method used to assess normal and
diminished bone mass.
GENERAL CONSIDERATIONS ON JOINTS
 Joints (articulations) are unions or junctions between two or
more bones or rigid parts of the skeleton.
 Joints exhibit a variety of forms and functions. It is the fact that,
whether or not movement occurs between them, it is still
called a joint.
 Some joints have no movement, others allow only slight
movement, and some are freely movable.
Classification of Joints
Joints are classified according to the tissues that lie between the
bones:
1) Fibrous joints
2) Cartilaginous joints
3) Synovial joints
Fibrous joints
 The bones are united by fibrous tissue.
 The amount of movement occurring at a fibrous joint
depends in most cases on the length of the fibers uniting the
articulating bones.
 The sutures of the cranium are examples of fibrous joints.
 These bones are close together, either interlocking along a
wavy line or overlapping.
 A syndesmosis type of fibrous joint unites the bones with a
sheet of fibrous tissue, either a ligament or a fibrous
membrane.
 Consequently, this type of joint is partially movable.
 The interosseous membrane in the forearm is a sheet of
fibrous tissue that joins the radius and ulna in a
syndesmosis.
 A dentoalveolar syndesmosis (gomphosis or socket) is a
fibrous joint in which a peglike process fits into a socket
articulation between the root of the tooth and the alveolar
process of the jaw.
 Mobility of this joint (a loose tooth) indicates a pathological
state affecting the supporting tissues of the tooth.
Cartilaginous joints
The bones are united by hyaline cartilage or fibrocartilage.
In primary cartilaginous joints, or synchondroses, the bones are united
by hyaline cartilage, which permits slight bending during early life.
Secondary cartilaginous joints, or symphyses, are strong, slightly
movable joints united by fibrocartilage.
The fibrocartilaginous intervertebral discs between the vertebrae
consist of binding connective tissue that joins the vertebrae together.
Synovial joints
 The bones are united by a joint (articular) capsule (composed of an
outer fibrous layer lined by a serous synovial membrane) spanning
and enclosing an articular cavity.
 Synovial joints are the most common type of joints and provide free
movement between the bones they join.
 They are joints of locomotion, typical of nearly all limb joints.
This type of joints has three common features:
Joint cavity: The joint cavity of a synovial joint, like the
knee, is a potential space that contains a small amount
of lubricating synovial fluid, secreted by the synovial
membrane.
Articular cartilage: The articular surfaces are covered
by hyaline cartilage
Articular capsule: This structure surrounds the joint and formed of
two layers. Inside the capsule, articular cartilage covers the articulating
surfaces of the bones; all other internal surfaces are covered by synovial
membrane.
1. Fibrous capsule
2. Synovial membrane
Some synovial joints have other distinguishing features,
such as a fibrocartilaginous articular disc or meniscus,
which are present when the articulating surfaces of the
bones are incongruous.
Ligaments
 A ligament is a cord or band of connective tissue uniting two
structures.
 Articular capsules are usually strengthened by articular ligaments.
 These are from dense connective tissue and they connect the
articulating bones to each other.
Ligaments
 Articular ligaments limit the undesired and/or excessive movements
of the joints.
 Articular ligaments are classified as intrinsic and extrinsic ligaments.
Articular disc: Help to hold the bones together.
Labrum: A fibrocartilaginous ring which deepens the articular surface
for one of the bones.
Fatt Pads: A pad of fat lying within a joint, covered with synovial
membrane and thought to assist in the spreading of synovial lubricant,
e.g. infrapatellar fat pad of stifle joint.
Bursa
 Bursae are flattened sacs that contain synovial fluid to
reduce friction.
 Its walls are separated by a film of viscous fluid.
 Bursae are found wherever tendons rub against bones,
ligaments, or other tendons.
 They are commonly found close to joints where the skin
rubs against underlying bony structures, for example, the
prepatellar bursa.
Tendon Sheath
 A layer of the synovial membrane around a tendon.
 Permits the tendon to move.
Types of synovial joints
The six major types of synovial joints are classified according
to the shape of the articulating surfaces and/or the type of
movement they permit:
1. Plane joints
2. Hinge joints (ginglymus, trochlear joints)
3. Saddle joints
4. Condyloid (ellipsoid type)
5. Ball and socket joints
6. Pivot joints
Plane joints (gliding joints) permit gliding or sliding
movements in the plane of the articular surfaces.
The articular surfaces of the plane joints are almost flat.
Most plane joints move in only one axis, hence they are called
uniaxial joints.
Examples for Plane joints
Acromioclavicular joint
between the acromion of the scapula and the clavicle
Hinge joints (ginglymus, trochlear joints)
Also uniaxial
flexion and extension only, around the transverse axis.
Bones are joined with strong collateral ligaments. e.g. elbow and knee
joints.
Cylindrical projections (condyles) fit into concave shapes.
Saddle joints
abduction – adduction & flexion and extension
biaxial joints that allow movement in two planes
sagittal and frontal.
The articular surfaces resemble a saddle shape and are concave and
convex respectively.
Examples for Saddle joints
Carpometacarpal joint at the base of the 1st digit (thumb)
Condyloid (ellipsoid type) joints
Flexion and extension as well as abduction and adduction
Biaxial
Examples for Condyloid (ellipsoid type) joints
Metacarpophalangeal joints (knuckle joints)
Radiocarpal joint (wrist)
Ball and socket joints (enarthrosis, spheroidal joint)
 Movement in multiple axes and planes:
flexion and extension, abduction and adduction, medial and lateral
rotation, and circumduction
multi-axial joints
 The spheroidal surface of a bone articulates with the socket shaped
articular surface of another bone.
Examples for Ball and socket joints
Hip joint
Shoulder joint
Pivot joints
 Rotation around a central axis
 The rounded part of a bone rotates in
a sleeve or ring like osteofibrous structure.
 The rounded end of one bone fits
into the sleeve of bone or ligaments.
uniaxial
Examples for Pivot joints
Median atlantoaxial joint
Atlas (C1 vertebra) rotates around a finger-like process, the dens of the
axis (C2 vertebra), during rotation of the head.
Proximal and distal radioulnar joints
Stability of Joints
depends on four main factors:
1) Negative pressure within the joint cavity
2) Shape, size, and arrangement of the articular surfaces
3) Ligaments
4) Tone of the muscles around the joint
Articular Surfaces
 The ball-and-socket arrangement of the hip joint and the mortise
arrangement of the ankle joint are good examples of how bone shape
plays an important role in joint stability.
 Other examples of joints, however, in which the shape of the bones
contributes little or nothing to the stability, include the
acromioclavicular joint, the calcaneocuboid joint, and the knee joint.
Ligaments
 Fibrous ligaments prevent excessive movement in a joint, but if the
stress is continued for an excessively long period, then fibrous
ligaments stretch.
 Should the tone of the muscles that normally support the arches
become impaired by fatigue, then the ligaments will stretch and the
arches will collapse, producing flat feet.
 Elastic ligaments, conversely, return to their original length after
stretching.
Muscle Tone
 In most joints, muscle tone is the major factor controlling stability.
 For example, the muscle tone of the short muscles around the
shoulder joint keeps the hemispherical head of the humerus in the
shallow glenoid cavity of the scapula.
 The knee joint is very unstable without the tonic activity of the
quadriceps femoris muscle.
 Without the action of these muscles, very little force would be
required to dislocate this joint.
Joint vasculature and innvervation
 Joints receive blood from articular arteries that arise from the
vessels around the joint.
 The arteries often anastomose (communicate) to form networks
(periarticular arterial anastomoses) to ensure a blood supply to
and across the joint in the various positions assumed by the joint.
 Articular veins are communicating veins that accompany arteries
(L. venae comitantes) and, like the arteries, are located in the
joint capsule, mostly in the synovial membrane.
Joint innvervation
 Joints have a rich nerve supply provided by articular nerves with
sensory nerve endings in the joint capsule.
 The capsule and ligaments receive an abundant sensory nerve supply.
 Hilton's law: A sensory nerve supplying a joint also supplies the
muscles moving the joint and the skin overlying the insertions of
these muscles.
Examination of Joints
 When examining a patient, the clinician should assess the normal
range of movement of all joints.
 When the bones of a joint are no longer in their normal anatomic
relationship with one another, then the joint is said to be
dislocated.
Examination of the shoulder joint
Knee examination
Dislocation of Joints
 Some joints are particularly susceptible to dislocation because of:
a) lack of support by ligaments
b) the poor shape of the articular surfaces,
c) the absence of adequate muscular support.
 The shoulder joint, temporomandibular joint, & acromioclavicular
joints are good examples.
Dislocation of the acromioclavicular joint
Anterior knee dislocation
Dislocation of the hip is usually congenital, being caused by inadequate
development of the socket that normally holds the head of the femur
firmly in position.
Damage to Ligaments
 Joint ligaments are very prone to excessive stretching and even
tearing and rupture.
 If possible, the apposing damaged surfaces of the ligament are
brought together by positioning and immobilizing the joint.
 In severe injuries, surgical approximation of the cut ends may be
required.
Trauma and Infection of Bursae and Tendon Sheaths
Bursae and synovial sheaths are commonly the site of traumatic or
infectious disease.
For example, the extensor tendon sheaths of the hand may become
inflamed after excessive or unaccustomed use.
An inflammation of the prepatellar bursa may occur as the result of
trauma from repeated kneeling on a hard surface.
Osteoarthritis
 Synovial joints are well designed to withstand wear, but heavy use
over several years can cause degenerative changes.
 Some destruction is inevitable during such activities as jogging, which
wears away the articular cartilages and sometimes erodes the
underlying articulating surfaces of the bones.
Osteoarthritis
The normal aging of articular cartilage begins early in adult life and
progresses slowly thereafter, occurring on the ends of the articulating
bones, particularly those of the hip, knee, vertebral column, and hands.
 Degenerative joint disease or osteoarthritis is often accompanied by
stiffness, discomfort, and pain.
 Osteoarthritis is common in older people and usually affects joints
that support the weight of their bodies (e.g., the hips and knees).
Arthroscopy
 The cavity of a synovial joint can be examined by inserting
a cannula and an arthroscope (a small telescope) into it.
 This surgical procedure enables orthopedic surgeons to
examine joints for abnormalities, such as torn menisci
(partial articular discs of the knee joint).
 Some surgical procedures can also be performed during
arthroscopy (e.g., by inserting instruments through small
puncture incisions).