Chapter 3 - Human Skeleton
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Transcript of Chapter 3 - Human Skeleton
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CHAPTER 3
HUMAN SKELETON
I. INTRODUCTION
A. Bone is made up of several different tissues working together: bone, cartilage, dense
connective tissue, epithelium, various blood forming tissues, adipose tissue, and
nervous tissue.
B. Each individual bone is an organ; the bones, along with their cartilages, make up the
skeletal system.
II. FUNCTIONS OF THE SKELETAL SYSTEM
A. Bones support the soft tissues and provide attachment sites for muscles, thereby
serving as the structural framework for the body.
B. Many of the body’s internal organs are protected by bony coverings.
C. Bones assist skeletal muscles to produce movement.
D. Bones store and release several minerals, especially calcium and phosphorus, to
help maintain mineral homeostasis.
E. Hemopoiesis, blood cell formation, occurs in the red marrow of bones.
F. Yellow marrow of adult bones serves as a site of triglyceride storage.
III. STURCTURE OF BONE
A. The structure of bone can be analyzed by studying a long bone .
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B. A typical long bone consists of numerous parts.
1. The diaphysis is the shaft of the long bone.
2. The epiphyses are the ends of the bone
3. The metaphyses are the areas between the epiphysis and diaphysis and
include the epiphyseal plate in growing bones.
4. Hyaline cartilage (articular cartilage) at the ends of the bones reduces friction
and absorbs shock at freely moveable joints.
5. The periosteum is a connective tissue covering of the surface of the bone
which contains osteogenic cells, protects bone, assists in fracture repair,
helps nourish bone tissue, and serves as an attachment point for ligaments
and tendons.
6. The space within the diaphysis is the marrow cavity.
7. The endosteum is the lining of the medullary cavity.
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IV. HISTOLOGY OF BONE TISSUE
A. The matrix of bone contains inorganic salts, primarily hydroxyapatite and some
calcium carbonate, and collagen fibers.
1. These and a few other salts are deposited in a framework of collagen fibers,
a process called calcification or mineralization.
2. Mineral salts confer hardness on bone while collagen fibers give bone its
great tensile strength.
3. The process of calcification occurs only in the presence of collagen fibers.
B. Bone (osseous) tissue consists of widely separated cells surrounded by large
amounts of matrix.
C. There are four principal types of bone cells.(Figure 6.2)
1. Osteogenic cells undergo cell division and develop into osteoblasts.
2. Osteoblasts are bone-building cells.
3. Osteocytes are mature bone cells and the principal cells of bone tissue.
4. Osteoclasts are derived from monocytes and serve to break down bone
tissue.
D. Depending on the size and distribution of the spaces between the hard components
of bone, the regions of a bone may be categorized as compact or spongy (Figure
6.1).
1. Compact Bone
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a. Compact bone is arranged in units called osteons or Haversian
systems (Figure 6.3a).
b. Osteons contain blood vessels, lymphatic vessels, nerves, and
osteocytes along with the calcified matrix.
c. Osteons are aligned in the same direction along lines of stress. These
lines can change as the stresses on the bone changes.
2. Spongy Bone
a. Spongy (cancellous) bone does not contain osteons. It consists of
trabeculae surrounding many red marrow filled spaces (Figure 6.3b).
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b. It forms most of the structure of short, flat, and irregular bones, and
the epiphyses of long bones.
c. Spongy bone tissue is light and supports and protects the red bone
marrow.
3. A bone scan is a diagnostic procedure that can detect certain bone
abnormalities or disorders.
V. BLOOD AND NERVE SUPPLY OF BONE
A. Bone is richly supplied with blood (Figure 6.4).
B. The arterial supply to bone involves several vessels.
1. The periosteal arteries pass through Volkmans’ canals to a multitude of
vessels that supply the outer compact bone region (Figure 6.3a).
2. The nutrient artery passes through the nutrient canal and sends branches
into the central Haversian canals to provide for osteocytes .
3. The metaphyseal artery enters the metaphysis while the epiphyseal arteries
enter the epiphyses.
C. Veins that carry blood away from long bones are evident in three places. (Figure 6.5)
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1. One or two nutrient veins follow the nutrient artery in the diaphysis.
2. Epiphyseal and metaphyseal veins accompany epiphyseal and metaphyseal
arteries in the epiphysis.
3. Periosteal veins exit with their periosteal arteries in the periosteum.
D. Nerves follow vessels into bone tissue and the periosteum where they sense
damage and transmit pain messages.
VI. BONE FORMATION
A. Bone formation is termed osteogenesis or ossification and begins when
mesenchymal cells provide the template for subsequent ossification. Two types of
ossification occur.
1. Intramembranous ossification is the formation of bone directly from or within
fibrous connective tissue membranes.
2. Endochondrial ossification is the formation of bone from hyaline cartilage
models.
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B. Intramembranous ossification forms the flat bones of the skull and the mandible
(Figure 6.5).
1. An ossification center forms from mesenchymal cells as they convert to
osteoblasts and lay down osteoid matrix.
2. The matrix surrounds the cell and then calcifies as the osteoblast becomes
an osteocyte.
3. The calcifying matrix centers join to form bridges of trabeculae that constitute
spongy bone with red marrow between.
4. On the periphery the mesenchyme condenses and develops into the
periosteum.
C. Endochondrial ossification involves replacement of cartilage by bone and forms most
of the bones of the body (Figure 6.6).
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1. The first step in endochondrial ossification is the development of the cartilage
model.
2. Step two is the growth of the cartilage model.
3. In step three, the primary ossification center develops in the diaphysis.
4. The medullary (marrow) cavity develops and fills with red marrow.
5. Step four involves the development of secondary ossification centers in the
epiphysis.
6. The final process is the formation of articular cartilage and the epiphyseal
plate.
VII. BONE GROWTH
A. Growth in Length
1. To understand how a bone grows in length, one needs to know details of the
epiphyseal or growth plate (Figure 6.7).
2. The epiphyseal plate consists of four zones: the zone of resting cartilage,
zone of proliferation cartilage, zone of hypertrophic cartilage, and zone of
calcified cartilage (Figure 6.7b).
3. The activity of the epiphyseal plate is the only means by which the diaphysis
can increase in length.
4. When the epiphyseal plate closes, is replaced by bone, the epiphyseal line
appears and indicates the bone has completed its growth in length.
B. Growth in Thickness
1. Bone can grow in thickness or diameter only by appositional growth (Figure
6.8).
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2. The steps in thes process are:
a. Periosteal cells differentiate into osteoblasts which secrete collagen
fibers and organic molecules to form the matrix.
b. Ridges fuse and the periosteum becomes the endosteum.
c. New concentric lamellae are formed.
d. Osetoblasts under the peritsteum form new circumferential lamellae.
C. Factors Affecting Bone Growth
1. Adequate dietary intake of minerals and vitamins is necessary for growth and
maintenance of bone.
e. Calcium and phosphorus are needed for bone growth in large
concentrations, with other minerals needed in smaller amounts.
f. Vitamins C, K, B12, and A are needed for bone growth.
2. The most important hormones for stimulation of bone growth during childhood
are the insulinlike growth factors (IGFs), which are stimulated by human
growth hormone (hGH).
3. Thyroid hormones and insulin are also necessary hormones for bone growth.
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4. At puberty the sex hormones, estrogen and testosterone, stimulate sudden
growth and modifications of the skeleton to create the male and female
forms.
5. Hormonal abnormalities can affect growth in height.
VII. BONES AND HOMEOSTASIS
A. Bone Remodeling
1. Remodeling is the ongoing replacement of old bone tissue by new bone
tissue.
2. Old bone is constantly destroyed by osteoclasts, whereas new bone is
constructed by osteoblasts.
3. In orthodontics teeth are moved by vraces. This places stress on bone in the
sockets causing osteoclasts and osteablasts to remodel the sockets so that
the teeth can be properly alligned (Figure 6.2)
4. Several hormones and calcitrol control bone growth and bone remodeling
(Figure 6.11)
B. Fracture and Repair of Bone
1. A fracture is any break in a bone.
2. Common fractures include open (compound) fracture (Figure 6.9a), closed
(simple) fracture, comminuted fracture (Figure 6.9b), greenstick fracture
(Figure 6.9c), impacted fracture (Figure 6.9d), Pott’s fracture (Figure 6.9e),
and Colles’s fracture (Figure 6.9f).
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3. A stress fracture is a series of microscopic fissures in bone that forms without
any evidence of injury to other tissues.
4. Fracture repair (Figure 6.10)involves formation of a clot called a fracture
hematoma, organization of the fracture hematoma into granulation tissue
called a procallus (subsequently transformed into a fibrocartilaginous [soft]
callus), conversion of the fibrocartilaginous callus into the spongy bone of a
bony (hard) callus, and, finally, remodeling of the callus to nearly original
form.
5. Treatments for fractures include the anatomic realignment of the bone
fragments, immobilization to maintain realignment, and restoration of function
(Clinical Application).
C. Bone’s Role in Calcium Homeostasis
1. Bone is the major reservoir for calcium ions (Ca2+) in the body; the blood level
calcium ions (Ca2+) are very closely regulated due to calcium’s importance in
cardiac, nerve, enzyme, and blood physiology.
2. An important hormone regulating Ca2+ exchange between bone and blood is
parathyroid hormone (PTH), secreted by the parathyroid gland. It increases
blood calcium ion levels.
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3. Another hormone that contributes to the homeostasis of blood Ca2+ is
calcitonin (CT). It is secreted by the thyroid gland and decreases blood Ca2+
levels.
4. Vitamin D is also involved in calcium homeostasis
IX. EXERCISE AND BONE TISSUE
A. Within limits, bone has the ability to alter its strength in response to mechanical
stress by increasing deposition of mineral salts and production of collagen fibers.
B. Removal of mechanical stress weakens bone through demineralization (loss of
bone minerals) and collagen reduction.
C. Weight-bearing activities, such as walking or moderate weightlifting, help build and
retain bone mass.
X. AGING AND BONE TISSUE
A. Of two principal effects of aging on bone, the first is the loss of calcium and other
minerals from bone matrix (demineralization), which may result in osteoporosis.
B. The second principal effect of aging on the skeletal system is a decreased rate of
protein synthesis, resulting in decreased production of matrix components (mostly
collagen) and making bones more susceptible to fracture.
XI. DISORDERS: HOMEOSTATIC IMBALANCES
A. Osteoporosis is a decrease in the amount and strength of bone tissue owing to
decreases in hormone output. In osteoporosis, bone resorption outpaces bone
formation.
B. Rickets and osteomalacia are disorders in which bones fail to calcify.
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AXIAL SKELETON
I. INTRODUCTION
A. Familiarity with the names, shapes, and positions of individual bones helps to locate
other organs and to understand how muscles produce different movements due to
attachment on individual bones and the use of leverage with joints.
B. The bones, muscles, and joints together form the musculoskeletal system.
II. DIVISIONS OF THE SKELETAL SYSTEM
A. The axial skeleton consists of bones arranged along the longitudinal axis of the body.
The parts of the axial skeleton, composed of 80 bones, are the skull, hyoid bone,
vertebral column, sternum, and ribs (Figure 7.1).
B. The appendicular skeleton comprises one of the two major divisions of the skeletal
system.It consists of 126 bones in the upper and lower extremities (limbs or
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appendages) and the pectoral (shoulder) and pelvic (hip) girdles, which attach them
to the rest of the skeleton.
III. TYPES OF BONES
A. Almost all of the bones of the body can be classified on the basis of shape: long,
short, flat, irregular, and sesamoid (Figure 7.2).
B. Sutural bones are classified on the basis of location (Figure 7.6). The number of
sutural bones varies greatly from person to person.
IV. BONE SURFACE MARKINGS
A. Bones show characteristic surface markings which are structural features adapted
for specific functions.
B. There are two major types of surface markings.
1. Depressions and openings participate in joints or allow the passage of soft
tissue.
2. Processes are projections or outgrowths that either help form joints or serve
as attachment points for connective tissue.
C. Table 7.2 describe the various surface markings along with examples of each.
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D. Skeletal remains persist for many years after a person’s death. These remains may
reveal patterns of disease, nutrition, as well as the individual’s sex, age, height, and
race.
V. SKULL
A. The skull, composed of 22 bones, consists of the cranial bones (cranium) and the
facial bones (face) (Figures. 7.3 through 7.8).
B. General Features
1. The skull forms the large cranial cavity and smaller cavities, including the
nasal cavity and orbits (eye sockets).
2. Certain skull bones contain mucous membrane lined cavities called
paranasal sinuses.
3. The only moveable bone of the skull, other than the ear ossicles within the
temporal bones, is the mandible.
4. Immovable joints called sutures hold the skull bones together.
5. The cranial bones have many functions.
a. They protect the brain.
b. Their inner surfaces attach to membranes that stabilize the positions
of the brain, blood vessels, and nerves.
c. The outer surfaces of cranial bones provide large areas of attachment
for muscles that move the various parts of the head.
d. Facial bones form the framework of the face and protect and provide
support for the nerves and blood vessels in that area.
e. Cranial and facial bones together protect and support the special
sense organs.
C. Cranial Bones
1. Frontal Bones
a. The frontal bones form the forehead, the roofs of the orbits, and most
of the anterior part of the cranial floor (Figure 7.3).
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b. A “black eye” results from accumulation of fluid and blood in the upper
eyelid following a blow to the relatively sharp supraorbital margin
(brow line).
2. Parietal bones form the greater portion of the sides and roof of the cranial
cavity (Figure 7.4).
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3. Temporal bones form the inferior lateral aspects of the cranium and part of
the cranial floor
4. The occipital bone forms the posterior part and most of the base of the
cranium
5. The sphenoid bone is called the keystone of the cranial floor because it
articulates with all the other cranial bones, holding them together .The
ethmoid bone forms part of the anterior portion of the cranial floor, the medial
wall of the orbits, the superior portion of the nasal septum, and most of the
superior side walls of the nasal cavity. It is a major superior supporting
structure of the nasal cavity
D. Facial Bones
1. Nasal bones form part of the bridge of the nose
2. The maxillae unite to form the upper jawbone and articulate directly with
every bone of the face except for the mandible
a. They form part of the floors of the orbits, part of the lateral walls and
floor of the nasal cavity, and most of the hard palate.
b. Cleft palate and cleft lip result from a lack of fusion of portions of the
palatine and maxillary bones during fetal development.
3. The zygomatic bones (cheekbones) form the prominences of the cheeks and
part of the lateral wall and floor of each orbit .
4. The lacrimal bones form a part of the medial wall of each orbit and are the
smallest bones of the face.
5. Palatine bones form the posterior portion of the hard palate, part of the floor
and lateral wall of the nasal cavity, and a small portion of the floors of the
orbits
6. The inferior nasal conchae (turbinates) form a part of the inferior lateral wall
of the nasal cavity
7. The vomer, found on the floor of the nasal cavity, is one of the components of
the nasal septum .
8. The mandible (jawbone) is the largest, strongest facial bone and the only
moveable skull bone (other than the ear ossicles)
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a. The mandible articulates with the temporal bone to form the
temporomandibular joint
b. Temporomandibular joint (TMJ) syndrome is dysfunction to varying
degrees of the temporomandibular joint. Causes appear to be
numerous and the treatment is similarly variable.
E. Nasal Septum
1. The nasal septum is a vertical partition that divides the nasal cavity into right
and left sides
2. A deviated nasal septum is a lateral deflection of the septum from the midline,
usually resulting from improper fusion of septal bones and cartilage.
F. The orbits (eye sockets)
1. The orbits contain the eyeballs and associated structures and are formed by
seven bones of the skull.
2. Five important foramina are associated with each orbit
G. Unique Features of the Skull
1. Sutures
a. Sutures are immovable joints found only between skull bones and
hold skull bones together.
b. Sutures include the coronal, sagittal, lamboidal,and squamous
sutures, among others
2. Paranasal Sinuses
a. Paranasal sinuses are cavities in bones of the skull that communicate
with the nasal cavity.
b. They are lined by mucous membranes and also serve to lighten the
skull and serve as resonating chambers for speech.
c. Cranial bones containing the sinuses are the frontal, sphenoid,
ethmoid, and maxillae.
d. Sinusitis occurs when membranes of the paranasal sinuses become
inflamed due to infection or allergy.
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3. Fontanels
a. Fontanels are dense connective tissue membrane-filled spaces
between the cranial bones of fetuses and infants. They remain
unossified at birth but close early in a child’s lift.
b. The major fontanels are the anterior, posterior, anterolaterals, and
posterolaterals .
c. Fontanels have two major functions.
1) They enable the fetal skull to modify its size and shape as it
passes through the birth canal.
2) They permit rapid growth of the brain during infancy.
HYOID BONE
A. The hyoid bone is a unique component of the axial skeleton because it does not
articulate with any other bones.
B. The hyoid bone consists of a horizontal body and paired projections, the lesser and
greater horns.
VERTEBRAL COLUMN
A. The vertebral column, along with the sternum and ribs, makes up the trunk of the
skeleton.
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B. The 26 bones of the vertebral column are arranged into five regions: cervical,
thoracic, lumbar, sacral, and coccygeal .
C. Normal Curves of the Vertebral Column
2. The four normal vertebral curves are the cervical and lumbar (anteriorly
convex curves) and thoracic and sacral (anteriorly concave curves).
3. In the fetus, there is only a single anteriorly concave curve.
a. The cervical curve develops as the child begins to hold his head erect.
b. The lumbar curve develops as the child begins to walk.
c. All curves are fully developed by age 10.
D. Between adjacent vertebrae, from the first cervical (atlas) to the sacrum, are
intervertebral discs that form strong joints, permit various movements of the vertebral
column, and absorb vertical shock.
E. Parts of a typical vertebra include a body, a vertebral arch, and several processes.
F. Regions of the Vertebral Column
1. Cervical Region
a. There are 7 cervical vertebrae .
b. The first cervical vertebra is the atlas and supports the skull
c. The second cervical vertebra is the axis, which permits side-to-side
rotation of the head
d. The third to sixth correspond to the structural patterns of the typical
cervical vertebrae.
e. The seventh called the vertebra prominens is somewhat different
2. Thoracic Region
a. There are 12 thoracic vertebrae .
b. These vertebrae articulate with the ribs.
3. Lumbar Region
a. There are 5 lumbar vertebrae .
b. They are the largest and strongest vertebrae in the column.
4. Table 7.4 summarizes the major structural differences among the cervical,
thoracic, and lumbar vertebrae.
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5. Sacrum
a. The sacrum is formed by the union of 5 sacral vertebrae and serves
as a strong foundation for the pelvic girdle.
b. Table 8.1 shows the differences between the male and female
sacrum.
6. Coccyx
a. The coccyx is formed by the fusion of 4 coccygeal vertebrae
b. Caudal anesthesia (epidural block), frequently used during labor (in
childbirth), causes numbness in the regions innervated by the sacral
and coccygeal nerves (approximately from the waist to the knees).
VIII. THORAX
A. The term thorax refers to the entire chest.
1. The skeletal part of the thorax (a bony cage) consists of the sternum, costal
cartilages, ribs, and the bodies of the thoracic vertebrae .
2. The thoracic cage encloses and protects the organs in the thoracic and
superior abdominal cavities. It also provides support for the bones of the
shoulder girdle and upper limbs.
B. Sternum
1. The sternum is located on the anterior midline of the thoracic wall.
2. It consists of three parts: manubrium, body, and xiphoid process .
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C. Ribs
1. The 12 pairs of ribs give structural support to the sides of the thoracic cavity.
2. The first 7 pairs of ribs are called true ribs; the remaining five pairs, false ribs
(with the last two false ribs called floating ribs).
3. Rib fractures are the most common types of chest injuries.
IX. DISORDERS: HOMEOSTATIC IMBALANCES
A. Protrusion of the nucleus pulposus into an adjacent vertebral body is called a
herniated (slipped) disc .This movement exerts pressure on spinal nerves, causing
considerable pain.
B. Abnormal curvatures of the vertebral column include scoliosis, an lateral bending of
the vertebral column; kyphosis, an exaggerated cuve of the thoracic curve; and
lordosis, an exaggeration of the lumbar curve .
C. Spina bifida is a congenital defect caused by failure of the vertebral laminae to unite
at the midline. This may involve only one or several vertebrae; nervous tissue may or
may not protrude through the skin.
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APPENDICULAR SKELETON
I. INTRODUCTION
A. The appendicular skeleton includes the bones of the upper and lower extremities and
the shoulder and hip girdles.
B. The appendicular skeleton functions primarily to facilitate movement.
II. PECTORAL (SHOULDER) GIRDLE
A. The pectoral or shoulder girdle attaches the bones of the upper limbs to the axial
skeleton (Figure 8.1).
B. Clavicle
1. The clavicle or collar bone lies horizontally in the superior and anterior part of
thorax superior to the first rib and articulates with the sternum and the clavicle
(Figure 8.2).
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2. The clavicle, one of the most frequently broken bones in the body, transmits
mechanical force from the upper limb to the trunk.
C. Scapula
1. The scapula or shoulder blade articulates with the clavicle and the humerus
(Figure 8.3).
2. The scapulae articulate with other bones anteriorly, but are held in place
posteriorly only by complex shoulder and back musculature.
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III. UPPER LIMB (EXTREMITY)
A. Each upper limb consists of 30 bones including the humerus, ulna, radius, carpals,
metacarpals, and phalanges (Figure 8.4).
B. Humerus
1. The humerus is the longest and largest bone of the upper limb (Figure 8.5).
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2. It articulates proximally with the scapula and distally at the elbow with both
the radius and ulna.
C. Ulna and Radius
1. The ulna is located on the medial aspect of the forearm (Figure 8.6).
2. The radius is located on the lateral aspect (thumb side) of the forearm (Figure
8.6)
3. The radius and ulna articulate with the humerus at the elbow joint (Figure
8.7a), with each other (Figure 8.7b, c), and with three carpal bones. (Figure
8.8)
D. Carpals, Metacarpal, and Phalanges
1. The eight carpal bones, bound together by ligaments, comprise the wrist
(Figure. 8.8).
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2. Five metacarpal bones are contained in the palm of each hand (Figure 8.8).
3. Each hand contains 14 phalanges, three in each finger and two in each
thumb (Figure 8.8).
IV. PELVIC (HIP) GIRDLE
A. The pelvic (hip) girdle consists of two hipbones (coxal bones) and provides a strong
and stable support for the lower extremities, on which the weight of the body is
carried (Figure 8.9).
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1. Each hipbone (coxal bone) is composed of three separate bones at birth: the
ilium, pubis, and ischium.
2. These bones eventually fuse at a depression called the acetabulum, which
forms the socket for the hip joint (Figure 8.10a).
B. The ilium
1. The larger of the three components of the hip bone and articulates (fuses)
with the ischium and pubic.
2. Bone marrow aspiration or bone marrow biopsy are frequently performed on
the iliac crest in adults.
C. The ischium is the inferior, posterior portion of the hip bone .
D. The pubis is the anterior and inferior part of the hip bone .
E. True and False Pelves
1. Together with the sacrum and coccyx, the two hipbones (coxal bones) form
the pelvis.
2. The greater (false) and lesser (true) pelvis are anatomical subdivisions of
this basin-like structure.
3. Pelvimetry, the measurement of the size of the inlet and the outlet of the birth
canan, is important during pregnancy
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V. COMPARISON OF FEMALE AND MALE PELVES
A. Male bones are generally larger and heavier than those of the female; the male’s
joint surfaces also tend to be larger.
B. Muscle attachment points are more well-defined in the bones of a male than of a
female due to the larger size of the muscles in males.
C. A number of anatomical differences exist between the pelvic girdles of females and
those of males, primarily related to the need for a larger pelvic outlet in females to
facilitate childbirth
VI. COMPARISON OF PECTORAL AND PELVIC GIRDLES
A. The pectoral girdle does not directly articulate with the vertebral column; the pelvic
girdle does.
B. The pectoral girdle sockets are shallow and maximize movement; those of the pelvic
girdle are deeper and allow less movement.
C. The structure of the pectoral girdle offers more movement than strength; the pelvic
girdle, more strength than movement.
VII. LOWER LIMB (EXTREMITY)
A. Each lower extremity is composed of 30 bones, including the femur, tibia, fibula,
tarsals, metatarsals, and phalanges (Figure 8.12).
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B. Femur
1. The femur or thighbone is the largest, heaviest, and strongest bone of the
body.
2. It articulates with the hip bone and the tibia.
C. Patella
1. The patella or kneecap is a sesamoid bone located anterior to the knee joint .
2. It functions to increase the leverage of the tendon of the quadriceps femoris
muscle, to maintain the position of the tendon when the knee is bent, and to
protect the knee joint.
3. Patellofemoral stress syndrome is a common knee problem in runners.
D. Tibia and Fibula
1. The tibia or shinbone is the larger, medial, weight-bearing bone of the leg .
2. The fibula is parallel and lateral to the tibia .
E. Tarsals, Metatarsals, and Phalanges
1. Seven tarsal bones constitute the ankle and share the weight associated with
walking.
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2. Five metatarsal bones are contained in the foot .
3. Fractures of the metatarsals are common among dancers, especially ballet
dancers.
4. The arrangement of phalanges in the toes is the same as that described for
the fingers and thumb above - fourteen bones in each foot .
F. Arches of the Foot
1. The bones of the foot are arranged in two non-rigid arches that enable the
foot to support the weight of the body; provide an ideal distribution of body
weight over the hard and soft tissues, and provide leverage while walking.
2. Flatfoot, clawfoot, and clubfoot are caused by decline, elevation, or rotation of
the medial longitudinal arches.
VIII. DEVELOPMENTAL ANATOMY OF THE SKELETAL SYSTEM
A. Bone forms from mesoderm by intramembranous or endochondrial ossification. The
skull begins development during the fourth week after fertilization
B. Vertebrae are derived from portions of cube-shaped masses of mesoderm called
somites
C. Around the fifth week of embryonic life, extremities develop from limb buds, which
consist of mesoderm and ectoderm.
D. By the sixth week, a constriction around the middle portion of the limb buds produces
hand plates and foot plates, which will become hands and feet.
E. By the seventh week, the arm, forearm and hand are evident in the upper limb bud
and the thigh, leg, and foot appear in the lower limb bud.
F. By the eighth week the limb buds have developed into limbs.
IX. FOCUS ON HOMEOSTASIS: THE SKELETAL SYSTEM Examines the skeletal system’s
contribution to homeostasis
X. DISORDERS: HOMEOSTATIC IMBALANCE
A. The term hip fracture most commonly applies to a break in the bones associated with
the hip joint.
B. Hip fractures often require surgical treatment.
………………………………………………..
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JOINT
I. INTRODUCTION
A. A joint (articulation or arthrosis) is a point of contact between two or more bones,
between cartilage and bones, or between teeth and bones.
B. The scientific study of joints is called arthrology.
II. JOINT CLASSIFICATION
A. Structural classification is based on the presence or absence of a synovial (joint)
cavity and type of connecting tissue. Structurally, joints are classified as fibrous,
cartilaginous, or synovial.
B. Functional classification of joints is based on the degree of movement permitted.
Joints may be synarthroses (immovable), amphiarthroses (partially movable), or
diarthroses (freely movable).
III. FIBROUS JOINTS
A. Fibrous joints lack a synovial cavity, have the articulating bones held together by
fibrous connective tissue, and permit little or no movement.
B. Types of fibrous joints include sutures, syndesmoses, and gomphoses.
1. A suture is a fibrous joint composed of a thin layer of dense fibrous
connective tissue that unites skull bones (Figure 9.1a).
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a. A synostosis is a suture joint that has ossified. An example of a
synostosis is the frontal suture between the left and right sides of the
frontal bone.
b. A synostosis is functionally classified as a synarthrosis.
2. A syndesmosis is a fibrous joint in which there is more fibrous connective
tissue than in a suture (Figure 9.1b).
3. A gomphosis (dentoalveolar) is a fibrous joint in which a cone-shaped peg fits
into a socket. An example is the root of a tooth in its socket (Figure 9.1c).
IV. CARTILAGINOUS JOINTS
A. A cartilaginous joint lacks a synovial cavity, has the articulating bones connected by
either fibrocartilage or hyaline cartilage, and allows little or no movement.
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B. The two types of cartilaginous joints are synchondroses and symphyses.
1. A synchrondosis is a cartilaginous joint in which the connecting material is
hyaline cartilage (Figure 9.2a).
2. A symphysis is a cartilaginous joint in which the connecting material is a disc
of fibrocartilage. Examples are the interverterbral discs (Figure 7.17) and the
pubic symphysis (Figure 9.2b).
V. SYNOVIAL JOINTS
A. Synovial joints have a synovial (joint) cavity between the articulating bone (Figure
9.3) and are freely movable (diarthrotic).
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B. Structure of Synovial Joints
1. Articular cartilage
a. The articular cartilage covers the bones at synovial joints.
b. The articular cartilage reduces friction at the joint with movement and
helps absorb shock
c. Techniques for cartilage replacement
1) In cartilage transplantation chondrocytes are removed from the
patient, grown in culture, and then placed in the damaged
joint.
2) Eroded cartilage may be replaced with synthetic materials
3) Researchers are also examining the use of stem cells to
replace cartilage.
2. Articular Capsule
a. The articular capsule surrounds a diarthrosis, encloses the synovial
cavity, and unites the articulating bones.
b. The articular capsule is composed of two layers - the outer fibrous
capsule (which may contain ligaments) and the inner synovial
membrane (which secretes a lubricating and joint-nourishing synovial
fluid) (Figure 9.3).
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c. The flexibility of the fibrous capsule permits considerable movement
at a joint, whereas its great tensile strength helps prevent bones from
dislocating.
d. Other capsule features include ligaments and articular fat pads
(Figure 9.3).
3. Synovial fluid,
a. secreted by the synovial membrane, lubricates and reduces friction in
the joint and supplies nutrients to and removes metabolic wastes from
the joint.
b. When disease or injury leads to a buildup of synovial fluid, the fluid
may be aspirated and medications may be injected into the cavity.
4. Accessory Ligaments and Articular Discs
c. Many diarthroses also contain accessory ligaments and articular discs
(menisci) .
d. Ligaments help hold bone to bone.
e. Articular discs modify the shape of the joint surfaces of the articulating
bones, help maintain the stability of the joint, and direct the flow of
synovial fluid to areas of greatest friction .
5. Torn cartilage, occurring frequently in the knees of athletes, is damage to the
articular discs that lie between the ends of some bones. Removal, to prevent
erosion and arthritis, is usually accomplished by arthroscopy.
C. Nerve and Blood Supply
1. Nerves that supply a joint are the same as those that supply the skeletal
muscles that move the joint.
2. Numerous arteries and veins supply the joints and surrounding structures.
D. Sprain and Strain
1. A sprain is the forcible wrenching or twisting of a joint that stretches or tears
its ligaments but does not dislocate the bone.
2. A strain is a stretched or partially torn muscle.
E. Bursae and Tendon Sheaths
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1. Bursae are synovial fluid filled saclike structures that cushion the movement
of one body part over another . They are found where one part of the body
moves over another.
3. Tendon sheaths are tubelike bursae that wrap around tendons where there is
considerable friction, such as the tendon of the biceps brachii at the shoulder
joint
4. Bursitis is a chronic inflammation of a burse.
VI. TYPES OF MOVEMENT AT SYNOVIAL JOINTS
A. Gliding movements occur when relatively flat bone surfaces move back and forth and
from side to side with respect to one another .
1. In gliding joints there is no significant alteration of the angle between the
bones.
2. Gliding movements occur at plantar joints.
B. Angular Movements
1. In angular movements there is an increase or a decrease in the angle
between articulating bones.
2. The principal angular movements are flexion, extension and hyperextension.
a. Flexion results in a decrease in the angle between articulating bones .
b. Extension results in an increase in the angle between articulating
bones .
c. Lateral flexion involves the movement of the trunk sideways to the
right or left at the waist. The movement occurs in the frontal plane and
involves the intervertebral joints .
3. Hyperextension is a continuation of extension beyond the anatomical position
and is usually prevented by the arrangement of ligaments and the anatomical
alignment of bones Abduction, Adduction, and Circumduction
a. Abduction refers to the movement of a bone away from the midline .
b. Adduction refers to the movement of a bone toward the midline
Circumduction refers to movement of the distal end of a part of the
body in a circle.
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4) Circumduction occurs as a result of a continuous sequence of
flexion, abduction, extension, and adduction.
5) Condyloid, saddle, and ball-and-socket joints allow
circumduction.
C. In rotation, a bone revolves around its own longitudinal axis.
1. Pivot and ball-and-socket joints permit rotation.
2. If the anterior surface of a bone of the limb is turned toward the midline,
medial rotation occurs. If the anterior surface of a bone of the limb is turned
away from the midline, lateral rotation occurs .
D. Special Movements
1. Elevation is an upward movement of a part of the body
2. Depression is a downward movement of a part of the body (Protraction is a
movement of a part of the body anteriorly in the transverse plane
3. Retraction is a movement of a protracted part back to the anatomical position.
4. Inversion is movement of the soles medially at the intertarsal joints so that
they face away from each other .
5. Eversion is a movement of the soles laterally at the intertarsal joints so that
they face away from each other .
6. Dorsiflexion refers to bending of the foot at the ankle in the direction of the
superior surface
7. Plantar flexion involves bending of the foot at the ankle joint in the direction of
the plantar surface .
8. Supination is a movement of the forearm at the proximal and distal radioulnar
joints in which the palm is turned anteriorly or superiorly
9. Pronation is a movement of the forearm at the proximal and distal radioulnar
joints in which the distal end of the radius crosses over the distal end of the
ulna and the palm is turned posteriorly or inferiorly
10. Opposition is the movement of the thumb at the carpometacarpal joint in
which the thumb moves across the palm to touch the tips of the finger on the
same hand.
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E. A summary of the movements that occur at synovial joints is presented in Table 9.1.
F. A dislocation or luxation is a displacement of a bone from a joint.
VII. TYPES OF SYNOVIAL JOINTS
A. Plantar joints permit mainly side-to-side and back-and-forth gliding movements
(Figure 9.10a). These joints are nonaxial and include the intercarpal, intertarsal,
sternoclavicular, acromioclavicular, sternocostal, and vertebrocostal joints.
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B. A hinge joint contains the convex surface of one bone fitting into a concave surface
of another bone (Figure 9.10b). Movement is primarily flexion or extension in a single
plane. Examples include the elbow, knee, ankle, and interphalangeal joints.
C. In a pivot joint, a round or pointed surface of one bone fits into a ring formed by
another bone and a ligament (Figure 9.10c). Movement is rotational and monaxial.
Examples are the atlas rotating about the axis (see Figure 9.8a) and turning the
palms anterior and posterior
D. In an condyloid joint, an oval-shaped condyle of one bone fits into an elliptical cavity
of another bone (Figure 9.10d). Movements are flexion-extension, abduction-
adduction, and circumduction; an example is the joint between the carpals and the
radius.
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E. A saddle joint contains one bone whose articular surface is saddle-shaped and
another bone whose articular surface is shaped like a rider sitting in the saddle.
Movements are flexion-extension, abduction-adduction, and circumduction (Figure
9.10e).
F. In a ball-and-socket joint, the ball-shaped surface of one bone fits into the cuplike
depression of another (Figure 9.10f). Movements are flexion-extension, abduction-
adduction, rotation, and circumduction; the only examples are the shoulder joint and
hip joint.
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G. Table 9.2 summarizes the structural and functional categories of joints.
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VIII.
SELECTED JOINTS OF THE BODY
A. Tempromandibular Joint (TMJ)
1. The TMJ is a combined hinge and planar joint formed by the condylar
process of the mandible, the mandibular fossa, and the articular tubercle of
the temporal bone.
2. Movements include opening and closing and protraction and retraction of the
jaw.
3. When dislocation occurs, the mouth remains open.
B. Shoulder Joint.
1. This is a ball-and-socket joint formed by the head of the humerus and the
glenoid cavity of the scapula.
2. Movements at the joint include flexion, extension, abduction, adduction,
medial and lateral rotation, and circumduction of the arm .
3. This joint shows extreme freedom of movement at the expense of stability.
4. Rotator cuff injury and dislocation or separated shoulder are common injuries
to this joint.
B. Elbow Joint
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1. This is a hinge joint formed by the trochlea of the humerus, the trochlear
notch of the ulna, and the head of the radius.
2. Movements at this joint are flexion and extension of the forearm.
3. Tennis elbow, little elbos, and dislacation of the radial head are common
injuries to this joint.
C. Hip Joint
1. This ball-and-socket joint is formed by the head of the femur and the
acetabulum of the hipbone.
2. Movements at this joint include flexion, extension, abduction, adduction,
circumduction, and medial and lateral rotation of the thigh.
3. This is an extremely stable joint due to the bones making up the joint and the
accessory ligaments and muscles.
D. Knee Joints
1. This is the largest and most complex joint of the body and consists of three
joints within a single synovial cavity.
2. Movements at this joint include flexion, extension, slight medial rotation, and
lateral rotation of the leg in a flexed position.
3. Some common injuries are rupture of the tibial colateral ligament and a
dislocation of the knee.
E. Refer to Tables 9.3 and 9.4 to integrate bones, joint classifications, and movements.
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IX. FACTORS AFFECTING CONTACT AND RANGE OF MOTION AT SYNOVIAL JOINTS
A. Structure and shape of the articulating bone
B. Strength and tautness of the joint ligaments
C. Arrangement and tension of the muscles
D. Contact of soft parts
E. Hormones
F. Disuse
X. AGING AND JOINTS
A. Various aging effects on joints include decreased production of synovial fluid, a
thinning of the articular cartilage, and loss of ligament length and flexibility.
B. The effects of aging on joints are due to genetic factors as well as wear and tear on
joints.
XI. ARTHROPLASTY
A. Arthroplasty is the surgical replacement of a joint with an artificial joint
B. The most commonly replaced joints are hips, knees, and shoulders.
XII. DISORDERS: HOMEOSTATIC IMBALANCES
A. Rheumatism and Arthritis
1. Rheumatism refers to any painful state of the supporting structures of the
body - bones, ligaments, joints, tendons, or muscles.
2. Arthritis is a form of rheumatism in which the joints become inflamed.
B. Rheumatoid arthritis is an autoimmune disease in which the body’s immune system
attacks its own cartilage and joint linings resulting in loss of joint function (Figure
9.15).
C. Osteoarthritis is a degenerative joint disease commonly known as “wear-and-tear”
arthritis. It is characterized by deterioration of articular cartilage and bone spur
formation. It is noninflammatory and primarily affects weight-bearing joints.
D. Gouty arthritis is a condition in which sodium urate crystals are deposited in soft
tissues of joints, causing inflammation, swelling, and pain. If not treated, bones at
affected joints will eventually fuse, rendering the joints immobile.
E. Lyme disease is a bacterial disease which is transmitted by deer ticks. Symptoms
include joint stiffness, fevers, chills, headache, and stiff neck.
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F. Ankylosing spondylitis affects joints between the vertebrae and between the sacrum
and hip bone. Its cause is unknown.
G. Ankle Sprains and Fractures: The ankle is the most frequently injured major joint.
Sprains are the most common injury to the ankle; they are treated with RICE. A
fracture of the distal leg that involves both the medial and lateral malleoli is called a
Pott’s fracture.