Stefanie MoreiraMs. Tahseen Ashley AcostaPeriod 4 Frances
Lindo11.18.13 The Skeletal System
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Overview The skeletal system is made up of all the bones in the
body, along with the tendons, ligaments, and joints that connect
them. The main functions of the skeleton are support, protection of
the internal organs, and movement. Bones store minerals such as
calcium. Produce red blood cells. At birth, we start with over 300
bones! But as we grow, bones fuse together and and become one,
totaling 206 bones.
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What are bones made of? A bone is enclosed in a tough, fibrous
tissue called the periosteum. It contains blood vessels. Beneath
the periosteum is an outer layer of compact bone, which is dense,
smooth and sturdy. Inside of it is a layer of cancellous bone,
which is spongy and more flexible. In the middle of bones is bone
marrow, which produces red blood cells.
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Classification Bones are classified according to their shape.
There are 5 types: Long bone (femur) Short bone (wrist, ankle) Flat
bone (scapula) Irregular bone (vertebrae) Round bone
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Anatomy of a Long Bone A long bone has a main shaft, called the
diaphysis, made of compact bone. Its covered with a sheet of living
cells, called the periosteum. Inside it is the medullary cavity
(lined with a thin, fibrous membrane called endosteum), which
consists of bone marrow. The bone marrow holds fat and produces
blood cells. At the ends of the diaphysis are epiphyses, made of
spongy bone. Beyond that is the articular cartilage (named because
it occurs where the joints articulate, or join).
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Bone Growth and Repair Bones have living tissues. Its shown in
their ability to grow and be repaired. The formation of bone, or
ossification, begins during embryonic development. Many different
types of cells involved in bone growth and repair: Osteoprogenitor
Cells: found in inner and outer surfaces of the bone Osteoblasts:
bone forming cells, derived from osteoprogenitor cells. Osteocytes:
mature cells derived from osteoblasts that maintain bone tissue.
Osteoclasts: perform bone resorption, meaning they break down bones
and assist in depositing calcium and phosphate in the blood.
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When a bone fractures, it undergoes a series of 4 steps:
Hematoma (blood escapes from ruptured blood vessels and clots)
Fibrocartilaginous Callus (tissue repair starts, fibrocartilage
fills space b/w broken bones) Bony Callus (osteoblasts, bone
forming cells, turn the fibro.cart. into bony callus and joins the
broken bones together) Remodeling Bone Growth and Repair Cont.
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Table 6.1 p100
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Axial Skeleton Skeleton is divided into the axial and
appendicular skeleton. The axial skeleton (80 bones) lies in the
middle of the body and contains the skull, hyoid, vertebral column,
and the thoracic cage. Skull: Formed by the cranium & facial
bones. -These bones contain sinuses, air spaces lined by mucous
membranes, that reduce the weight of the skull and give the voice a
resonant sound. (pg. 100) Sinusitis: inflammation of the paranasal
sinuses Mastoiditis: inflammation of the mastoid sinuses
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Cranial Bones Sutures: immovable joints that separate the
cranial bones. Frontal bone: forehead 2 Parietal bones: posterior
to frontal Occipital bone : back of the skull 2 Temporal bones:
inferior to parietal bones on the sides of the cranium. Sphenoid
bone: helps form the sides and floor of the cranium. Ethmoid bone:
anterior to sphenoid bone and helps form the floor of the
cranium.
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Bones of the Face Maxillae: the 2 maxillae form the upper jaw.
Zygomatic bones: form sides of the orbits and contribute to cheek
bones. Lacrimal bones: located on the medial walls of the orbits.
Nasal bones: form bridge of the nose. Vomer bone: forms the nasal
septum. Inferior Nasal Conchae: form part of the inferior lateral
wall of the nasal cavity. Mandible: the lower jaw, only movable
part of the skull.
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Hyoid: superior to the larynx; only bone in the body that does
not articulate to another. Vertebral column: Series of separate
bones; extends from the skull to the pelvis. Vertebrae are named
according to location Has 4 normal curvatures cervical & lumbar
(convex, or curved outward, anteriorly) thoracic & sacral
(concave anteriorly) Curvatures are subject to abnormalities. An
exaggerated lumbar curvature is called lordosis, or swayback.
Increased roundness of thoracic curvature is called kyphosis, or
hunchback. Abnormal lateral (side-to-side) curvature is called
scoliosis.
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Atlas and Axis Atlas: supports and balances the head; allows
movement. Axis: has an odontoid process, or dens, that projects
into the ring of the atlas. When the head moves from side to side,
the axis turns around the odontoid process.
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Sacrum and Coccyx The sacrum articulates with the pelvic girdle
and forms the posterior wall of the pelvic cavity. The coccyx, or
tailbone, is the last part of the vertebral column.
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Thoracic (rib) cage: Protects heart and lungs 12 pairs All
connect to vertebral column blue-axial orange-appendicular
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Appendicular System Contains the bones of the pectoral girdle,
upper limbs, pelvic girdle and lower limbs. Pectoral Girdle:
Consists of 4 bones : 2 clavicles and 2 scapulae. Supports the arms
and serves as a place of attachment for the arm muscles. Is held in
place by ligaments and muscles. It is possible to dislocate the
shoulder. Clavicle: (Collar bones) slender and S shaped, medial to
the manubrium of the sternum. Only place that is attached to the
axial skeleton. It is structurally weak and will fracture under
pressure.
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Scapulae: (sing. scapula) a.k.a shoulder blades, they resemble
triangles. The scapulae are not joined together and each one has a
spine. Acromion process: articulates with a clavicle, attach arm
and chest muscles. Coracoid process: attachment for arm and chest
muscles. Gleniad cavity: articulates with the head of the arm bone
(humerus).
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Upper Limbs Bones of the arm (humerus), forearm (radius and
ulna), and hand (carpals, metacarpals and phalanges.) Humerus: Bone
of the arm, long bone. Radius and Ulna: Bones of the forearm.
Radius is on the lateral side- thumb side. Ulna is the longer bone
of the forearm. Hand: Wrist, palm and five fingers. Wrist carpals,
wrist watch", or distal forearm. Fingers- metacarpal bones; contain
phalanges.
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Upper limbs: Humerus, Radius and Ulna
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Pelvic Girdle Two coxal bones (hipbones), as well as the sacrum
and coccyx. Coxal bones have 3 parts : Ilium- largest part flares
outward, hands rest on iliac crest. Ischium: inferior (most)
ischial tuberosity allows a person to sit. Pubis: anterior part of
the coxal, two bones joined at the pubic symphasis, posterior to
that is the obturator foramen. All 3 points meet at the acetabulum-
connects the femur. False pelvis bound to the trunk. True pelvis
upper and lower inlet and outlet in females moves apart to let the
baby be born.
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Gender Differences Female iliac crest more flared Broader hips
Wider between ischial spines and ischial tuberosities Inlet and
outlet are wider Pelvic cavity more shallow Lighter and thinner
bones Pubic arch U shaped Male pelvic cavity funnel shaped Pubic
arch V shaped
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Lower Limb Bones of the thigh (femur), kneecap (patella), leg
(tibia and fibula) and foot (tarsals, metatarsals and phalanges).
Femur: a.k.a thighbone, longest and strongest bone in the body.
Tibia: a.k.a shinbone, medial to the fibula. Thicker than the
fibula and bears weight from the femur. Fibula: lateral to the
tibia, more slender. Lateral malleolus articulate talus forms over
ankle. Foot: Consists of the ankle, instep and 5 toes. Ankle 7
bones talus move freely. Largest ankle bone is the calcaneus or
heel bone. Metatarsal bone - instep, ball of the foot. Toes
phalanges, the big toe only has two phalanges, while the other toes
have three.
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Lower limbs: Femur, Tibia and Fibula
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Articulation Two systems for classifying joints: (1) according
to the amount of movement they allow, (2) according to their
structure [1] Synarthorosis - an immovable joint [2]
Amphiarthorosis allows slight movement [3] Diarthorosis freely
movable Fibrous joints: occur where fibrous connective tissue joins
bone to bone typically immovable though there are exceptions. (for
all three types) [1] Cartilaginous joints: occur where
fibrocartilage or hyaline cartilage joins bones. [2] Synovial
joints: are formed where bone ends do not contact each other, but
are enclosed in a capsule. [3]
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Fibrous joints: adult cranium, coronal suture between the
parietal bones and the frontal bone, lambodial suture between the
parietal and occipital bone, squamosal suture between each parietal
bone and each temporal bone, and the sagittal suture between the
parietal bones. The joints formed by each tooth in its tooth jacket
are also fibrous joints. Cartilaginous joints: The ribs are joined
to the sternum by costal cartilages, which are hyaline cartilage.
The bodies of adjacent vertebrae are separated by fibrocartilage
invertebral disks, which increase vertebrae flexibility. The pubic
symphysis, the joint between the 2 pubic bones, consists largely of
fibrocartilage. Due to hormonal changes this joint becomes more
flexible during late pregnancy, allowing the pelvis to expand
during child birth.
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Synovial joints: The two bones are separated by a joint cavity.
The joint cavity is lined by synovial membrane, which produces
synovial fluid a lubricant for the joint. Absence of tissue between
the articulating joints enables movement but it also means that the
joint must be stabilized in some way. The joint is stabilized by
the joint capsule, a sleeve-like extension of the periosteum of
each articulating bone. Ligaments bind the bones (two) to one
another and add even more stability. Tendons also help stabilize
the synovial joint. The surface of the articulating joint are
protected in several ways: Bones are covered by an additional layer
of hyaline cartilage. The joint contains menisci (sing. meniscus)
crescent shaped pieces of cartilage. Fluid filled sacs called
bursae, which ease friction between all parts of the joint. The
inflammation of the bursae is called bursitis, tennis elbow is a
form of bursitis.
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Types of Synovial Joints Saddle joint: each bone is saddle
shaped and fits into the complementary regions of the other. Ex.
Joint between the carpal and metacarpal bones of the thumb.
Rotation is possible. Ball-and-socket joint: the ball-shaped head
of one bone fits into the cup-shaped socket of another. Ex.
Shoulder and hip joints. Pivot joint: a small, cylindrical
projection of one bone pivots within the ring formed of bone and
ligament of another bone. Only rotation is possible. Ex. The joints
between the proximal ends of the radius and ulna, and the joint
between the atlas and axis.
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Hinge joint: the convex surface of one bone articulates with
the concave surface of another bone. Up and down motion in one
plane is possible. Ex. Elbow and knee joints. Gliding joint: flat
or slightly curved surfaces of bones articulate. Sliding or
twisting in various planes is possible. Ex. Joints between the
bones of the writs and between the bones of the ankle. Condyloid
joint: oval-shaped condyle of one bone fits into the elliptical
cavity of another. Rotation is possible. Ex. Joints between the
metacarpals and phalanges.
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Movements permitted by Synovial Joints Angular movements
Flexion: joint angle, elbow forearm towards the arm, knee- legs
toward the thigh. Dorsiflexion is flexion of the foot upward
standing on your heels, and plantar flexion is flexion of the foot
downward standing on your toes. Extension: increases the joint
angle. Extension of the flexed elbow straightens the upper limb.
Hyperextension occurs when a portion of the body part extended
beyond 180. It is possible to hyperextend the head and the trunk of
the body and also the shoulder/wrist (arm/hand). Adduction: is the
movement a body part toward the midline. Ex. arms to sides.
Abduction: is the movement of a body part laterally away from
midline.
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Circular movements Circumduction: the movement of a body part
in a wide circle, as when a person makes arm circles. Rotation: the
movement of a body part around its own axis. Supination: the
rotation of the forearm so that the palm is upward. Pronation:
opposite move of the forearm so that the palm faces downward.
Special movements Inversion and eversion: applies only to the feet.
Inversion is turning the foot so that the sole faces inward.
Eversion is the sole facing outward. Elevation and depression:
refers to the lifting up and down respectively, of a body part, as
when you shrug your shoulders or move your jaw.
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Effects of Aging Both cartilage and bone deteriorate as a
person ages. Cartilage: The bluish color typical of young cartilage
changes to an opaque, yellowish color. The chondrocytes die,
reabsorption occurs as the cartilage undergoes calcification
becoming hard and brittle. Calcification interferes with the ready
diffusion of nutrients and waste products through the matrix.
Osteoarthritis is accompanied by deterioration of the articular
cartilage. Rheumatoid arthritis is the synovial membrane; becomes
inflamed and grows thick cartilage. Autoimmune reaction, the immune
system mistakenly attacks the synovial membrane, affects children
and young adults.
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Gout is caused by an excessive buildup of uric acid ( metabolic
waste) in the blood. Rather than being excreted in the urine, the
acid is deposited as crystals in the joints where it causes
inflammation and pain. Osteoporosis - present when weak and thin
bone cause aches and pains. Tend to fracture easily.
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Homeostasis The bones: protect the internal organs. The bones
assist all phase of respiration The bones store and release
calcium. The bone assist the lymphatic system and immunity.
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Other Functions Integumentary: support for skin helps provide
vitamin D for Ca 2+ absorption Muscular: stores Ca 2+ for muscle
move joints, muscles, help muscles Nervous: protects, store Ca 2+
for nerve function sensory input from bones to joints Endocrine:
protects, stores Ca 2+ use as second messenger regulates bone
development, parathyroid hormone and calcitonin regulate Ca 2+
content
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Cardiovascular: protects red bone marrow produces blood cell;
blood store Ca 2+ for blood clotting Blood vessels deliver
nutrients and O2 to the bones, carry away wastes. Lymphatic: Red
bone marrow produces white blood cells involved in immunity pick up
excess tissue fluid; protects against infections Respiratory:
protects, assists breathing, bones provide attachment sites for
muscles involved in breathing Picks up excess tissue fluid;
protects against infections Digestive -chew food, hyoid bone
assists swallowing Digestive tract provides Ca 2+ and other
nutrients for bone growth and repair Urinary- support, protection
vitamin D for Ca 2+ absorption and help maintain blood level of Ca
2+ need for bone growth and repair