chapter 1-musculoskeletal system
TRANSCRIPT
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Musculoskeletal system
The musculoskeletal system (also
known as the locomotor system)
is an organ system that givesanimals the ability to move using
the muscular and skeletalsystems.
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The musculoskeletal system
provides:1. form
2. stability, and
3. movement to the human
body.
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Musculoskeletal system is made up of the bodys
bones:
Skeleton
Muscles
Cartillage
Tendons
Ligaments
Joints
Connective tissues (described as the tissue that
supports and binds tissue and organs together)
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The musculoskeletal systems
primary functions include supportingthe body, allowing motion and
protecting vital organs.
The skeletal portion of the system
serves as the main storage system
for calcium and phosphorus andcontains critical components of
hematopoietic system.
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There are, however, diseases and disorders
that may render the function and overall
effectiveness of the system.
These diseases can be difficult to diagnose
due to the close relation of the
musculoskeletal system refers to the system
having its muscles attached to an internal
skeletal system. However, hydrostatic
musculoskeletal systems contain musclesattached to an external exoskeleton in order
to function and maintain shape.
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STRUCTURE IN HUMANSA. SKELETAL
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Skeletal
The human skeleton is a complex structure with twodistinct divisions.
The axial skeleton consists of the skull, vertebralcolumn, and rib cage.
The vertebral column is made up of 33 separatevertebrae separated by cartilaginous disk that allowmovement.
The ribs contain cartilage that allow the rib cage to
flex breathing.
The appendicular skeleton is the remaining 126 bonesthat are in the arms, legs and pelvis.
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The axial skeleton consists of 80
bones in the head and trunk of the humanbody. It is composed of five parts; the
human skull, the ossicles of the inner ear,
the hyoid bone of the throat, the chest andthe vertebral column the axial skeleton and
the appendicular skeleton together form
the complete skeleton. flat bones housesthe brain, spinal cord, and other vital
organs.
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Normal count of the human skeletal
system
Skull (22)
Cranial Bones (8)
Parietal (2) Temporal (2)
Frontal (1)
Occipital (1)
Ethmoid (1)
Sphenoid (1)
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Normal count of the human skeletal
system
Skull (22)
Facial bones (14)
Maxilla (2)
Zygomatic (2)
Mandible (1)
Nasal (2)
Palatine (2) Inferior nasal concha (2)
Lacrimal (2)
Vomer (1)
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Normal count of the human skeletal
system
Auditory ossicles
Ossicles (6)
Malleus (2)
Incus (2)
Stapes (2)
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Normal count of the human skeletal
system
Hyoid bone
hyoid bone (1)
U-shape bone located in the
neck. It anchors the tongue and is
associated with swallowing.
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Normal count of the human skeletal
system
Vertebral column
Vertebral column (33)
Cervical vertebrae (7)
Thoracic vertebrae (12)
Lumbar vertebrae (5)
Sacrum (5- fused)
Coccyx (4- fused, varies between 3-5)
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Normal count of the human skeletal
system
Ribs
Thoracic cage (25)
Sternum (1)
Ribs (24)
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Components of the skull
Eight bones from the neurocranium (brain
case), a protectivee vault of bone surrounding
the brain and brain stem.
Fourteen bones form the splanchnocranium,
which comprises the bones supporting the
face.
Encased within the temporal bones are the six
auditory ossicles of the middle ear.
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The hyoid bone, supporting the
larynx, is usually not considered as
part of the skull, as it is the onlybone that does not articulate with
other bones of the skull.
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The skull also contains the sinus cavities,
which are air-filled cavities lined with
respiratory epithelium, which also lines the
large airways.
The exact functions of the sinuses are
debatable; they contribute to lessening theweight of the skull with a minimal reduction
in strength, they contribute to ressonance of
the voice, and assist in the warming andmoistening of air drawn in through the nasal
cavities.
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A typical vertebra consists of two
essential parts: an anterior (front)
segment, which is the vertebral body;
and a posterior part- the vertebral
(neural) arch- which encloses thevertebral arch is formed by a pair of
pedicles and a pair of laminae, and
supports seven processes, four articular,two transverse, and one spinous, the
latter also being known as the neural
spine.
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When the vertebrae are articulated with
each other, the bodies form a strongpillar for the support of the head and
trunk, and the vertebral foramina
constitute a canal for the protection ofthe medulla spinalis (spinal cord). In
between every pair of vertebrae are two
apertures, the intervertebral foramina,one on either side, for the transmission
of the spinal nerves and vessels.
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Two transverse process and one
spinous process are posterior(behind) the vertebral body. The
spinous process comes out the back,
one transverse process comes outthe left, and one on the right.
The spinous process of the cervical
and lumbar region can be felt
through the skin.
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Superior and inferior articular
facets on each vertebra act to
restrict the range of movement
possble. These facets are joinedtogether by a thin portion of the
neural arch called the parsinterarticularis.
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Classification
The centra of the vertebra can be
classified based upon the fusion of its
elements. In aspidospondyly, bones suchas the neural spine, the pleurocentrum
and the intercentrum are separate
ossifications. Fused elements however,classify a vertebra as having
holospondyly.
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A vertebra can also be described in termsof the shape of the ends of the centra.
Humans are said to be acoelous, or withflat ends. These flat ends of the centraare especially good at supporting anddistributing comprehensive forces.
Amphicoelus vertebra is represented byboth ends of the centra being concave.This shape is common in fish, wheremost motion is limited.
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Amphicoelus centra often are
integrated with a full notochord. Procoelus vertebra are atriorly
concave, and posteriorly convex.
An opisthocoelus vertebra, however
is quite the opposite, where the
vertebra displays posterior convexity,and anterior concavity.
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Heterocoelus vertebrae are saddle
shaped at each end of the centra.This type of configuration is seen in
turtles that retract their necks, and
birds, because it permits extensivelateral and vertical flexion motion
without stretching the nerve cordtoo extensively or wringing it about
its long axis.
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Regions
Orientation of vertebral column on
surface. T3 is at level of medial part of
spine of scapula. T7 is at inferior angle of
the scapula. L4 is at the highest point of
iliac crest. S2 is at the level of posterior
superior iliac spine. Furthermore, C7 iseasily localized as a prominence at the
lower part of the neck.
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1. Cervical vertebrae
These are generally small and delicate.
Their spinous processes are short (with
the exception of C2 and C7, which have
palpable spinous process). Numbered
from top to bottom from C1-C7, atlas
(C1) and axis (C2), are the vertebrae thatallow the neck and head so much
movement.
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For the most part, the atlanto-
occipital joint allows the skull to
move up and down, while the
atlanto-axial joint allows the upperneck to twist left and right.
The axis also sits upon the first
intervertebral disk of the spinalcolumn.
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All mammals except manatees and sloths
have seven cervical vertebrae, whateverthe length of the neck.
Cervical vertebrae possess transverse
foramina to allow for the vertebralarteries to pass through on their way to
the foramen magnum to end in the Circle
of Willis. These are the smallest, lightestvertebrae and the vertebral foramina are
triangular in shape.
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The spinous process are short
and often bifurcated. (the spinous process of C7,
however, is not bifurcated, and issubstantially longer than that of
the other cervical spinous
processes)
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2. Thoracic vertebrae
Their transverse processes have
surfaces that articulate with the
ribs. Some rotation can occurbetween the thoracic vertebrae,
but their connection with the ribcage prevents much flexion or
other excursion.
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They may also be known as
dorsal vertebrae, in the humancontext. Bodies are roughly
heart-shaped and are about aswide anterio-posteriorly as they
are in the transverse dimension.
Vertebral foramina are roughlycircular in shape.
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3. Lumbar vertebrae
These vertebrae are very robust in
construction, as they must support more
weight than other vertebrae.
They allow significant flexion and extension,
moderate lateral flexion (side-bending), and a
small degree of rotation. The discs between
these vertebrae create a lumbar lordosis(curvature that is concave posteriorly) in the
human spine.
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4. Sacral vertebrae
There are 5 vertebrae (S1-S5).
They are fused in maturity,
with no intervertebral discs.
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5. Coccygeal vertebrae
There are 3-5 vertebrae (Co1-Co5), with
no intervertebral discs. Many animals
have greater number of tail vertebrae
and, in animals, they are more commonly
known as caudalvertebrae.
Pain in the coccyx (tailbone) is known ascoccydynia.
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Human rib cage
The human rib cage, also known as
the thoracic cage, is a bony and
cartilaginous structure whichsurrounds the thoracic (chest) cavity
and supports the pectoral (shoulder)
girdle, forming a core portion of thehuman skeleton.
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A typical human ribcage consists of
24 ribs, the sternum, costalcartilages, and the 12 thoracic
vertebrae. It, along with the skin and
associated fascia and muscles make
up the thoracic wall, and provides
attachments for the muscles of theneck, thorax, upper abdomen and
back.
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The human rib cage is a component of
the human respiratory system. Itencloses the thoracic cavity, which
contains the lungs.
An inhalation is accomplished when themuscular diaphragm, at the floor of the
thoracic cavity, contracts and flattens,
while contraction of intercostal muscleslift the rib cage up and out.
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These actions produce an increase in
volume and a resulting partial vacuum,or negative pressure, in the thoracic
cavity resulting in atmospheric pressure
pushing air into the lungs, inflating them. An exhalation results when the
diaphragm and intercostal muscles relax,
and elastic recoil of the rib cage and
lungs expels the air.
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All ribs are attached in the back to
the thoracic vertebrae.
The upper seven are called true ribs
(costae verae, vertebrosternal ribs, I-
VII ) are attached in the front to thesternum by means of costal
cartillage. Due to their elasticity they
allow movement when inhaling and
exhaling.
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The 8th, 9th, 10th ribs are called false ribs
(costae spuricae, vertebrochondral ribs, VIII-
X), and join with the costal cartillages of the
ribs above.
The 11th and 12th ribs are known as floating
ribs (costae fluitantes, vertebral ribs, XI-XII), as
they do not have any anterior connection to
the sternum.
The spaces between the ribs are known asintercostal spaces; they contain the intercostal
muscles, nerves and arteries.
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The human rib parts:
The head
is the end of a rib closest to the vertebral
column.
The costovertebral joints
are the articulations that connect the heads of
the ribs to the thoracic vertebrae.
The neck
is the flattened portion which extendslateralward from the head.
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The tubercle
Is an eminence on the posteriorsurface.
The angle
bending part.
The costal grove
is a grove between the ridge of theinternal surface of the rib and the
inferior border.
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Atypical ribs
The atypical ribs are the 1st, 2nd and
11thto 12th.
The first rib is a shaft that is wide and
nearly horizontal and has the sharpestcurve of the seven true ribs. Its head has a
single facet to articulate with the first
thoracic vertebra (T1). It has also twogroves for the subclavian vessels, which are
separated by the scalene tubercle.
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The second rib is thinner, less curved,
and longer than the first rib. It has two
facets to articulate with T2 and T1, and a
tubercle for muscles to attach to.
The 11th
to 12th
ribs have only onefacet on their heads; the 11thand 12thribs
are short with no necks or tubercles and
terminate in the abdominal wall beforefusing with the costal cartillages.
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Breathing
Breathing takes oxygen in and
carbon dioxide out of the body.
Aerobic organisms require oxygento create energy via respiration, in
the form of the metabolism ofenergy-rich molecules such as
glucose.
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The medical term for normal
relaxed breathing is eupnea.Breathing is only part of the
processes of delivering oxygento where it is needed in the
body and removing carbon
dioxide waste.
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The process of gas exchange
occurs in the alveoli by passivediffusion of gasses between the
alveolar gas and the blood passing
by in the lung capillaries. Once in
the blood the heart powers the
flow of dissolved gasses around thebody in the circulation.
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As well as carbon dioxide,
breathing also results in loss ofwater from the body. Exhaled
air has a relative humidity of100% because of water diffusing
across the moist surface ofbreathing passages and alveoli
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Appendicular skeleton
the appendicular skeleton consists of
126 bones in the human body which make
motion possible and protects the organs of
digestion, excretion, and reproduction. the
word appendicular refers to an appendage
or anything attached to a major part of the
body, such as the upper and lower
extremities.
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THE MAJOR AREAS OFAPPENDICULAR SKELETON
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1. Pectoral girdle
In humans, the only joints between
shoulder girdle and axial skeleton re
sternoclavicular joints on each side. No
joint exists between each scalpula and
the thoracic cage, instead of muscular
connection between the two permits
relatively great mobility of the shoulder
girdle in relation to the pelvic girdle
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2. Arm
The human arm contains 30 bones,
joints, muscles, nerves, and blood
vessels. Many of these muscles are used
for everyday tasks. The humerus is the
(upper) arm bone. It joins with the
scalpula above at the shoulder joint
(glenohumeral joint) and with the ulna
and radius below a the elbow joint.
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3. Elbow joint
The elbow joint is the hinge joint
between the distal end of the
humerus and the proximal ends ofthe radius and ulna. The humerus
cannot be broken easily. Its strength
allows it to handle loading up to300lbs.
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Osteofacial compartments
The arm is divided by a fascial layer
(known as lateral and medial
intermuscular septa) separating themuscles into two osteofascial
compartments:
Anterior compartment of the arm
Posterior compartment of the arm
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The fascia merges with theperiosteum (outer bone layer) of
the humerus. The compartments
contain muscles which are
innervated by the same nerve
and perform the same action.
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Two other muscles are considered to be partially
in the arm:
the large deltoid muscle is considered tohave part of its body in the anterior
compartment. This muscle is the main abductor
muscle of the upper limb and extends over theshoulder.
The brachioradialis muscle originates in
the arm but inserts into the forearm. Thismuscle is responsible for rotating the hand so its
palm faces forward (supination).
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Cubital fossa The cubital fossa is clinically important for
venipuncture and for blood pressuremeasurement. It is an imaginary triangle withborders being: Laterally
The medial border of brachioradialis muscle.
Medially The lateral border of pronator teres muscle.
Superiorly
The intercondylar line, an imaginary line between the twoepicondyles of the humerus.
The floor is the brachialis muscle.
The roof is the skin and fascia of the arm and forearm.
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Nerve supply
The musculoskeletal nerve, from C5, C6,
C7 is the main supplier of muscles of the
anterior compartment. It originates from
the lateral cord of the brachial plexus of
nerves. It pierces the coracobrachialis
muscle and gives off as the anterior
cutaneous nerve of the forearm.
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The musculoskeletal nerve, from C5,
C6, C7 is the main supplier ofmuscles of the anterior
compartment. It originates from the
lateral cord of the brachial plexus ofnerves. It pierces the
coracobrachialis muscle and gives off
as the anterior cutaneous nerve of
the forearm.
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The radial nerve, which of from the fifth
cervical spinal nerve to the first thoracic
spinal nerve, originates as the
continuation of the posterior cord of the
brachial plexus. This nerve enters the
lover triangular space (an imaginary
space bounded by, amongst others, the
shaft of the humerus and the triceps
brachii) of the arm and lies deep to the
triceps brachii.
H i l i h h d
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Here it travels with the deep
artery of the arm (the profunda
brachii), which sits in the radial
groove of the humerus. This fact
is very important clinically as afracture of the bone at the shaft
of the bone here can causeleasions or even transections in
the nerve.
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Other nerves passing through give no
supply to the arm. These include:
The median nerve, nerve origin C5-T1,
which is a branch of the lateral and medial
cords of the brachial plexus. This nerve
continues in the arm, travelling in a plane
between the biceps and triceps muscle. At
the cubital fossa, this nerve is deep to the
pronator teres muscle and is the mostmedial structure in the fossa. The nerve
passes into the forearm.
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Other nerves passing through give no
supply to the arm. These include:
The ulnar nerve, origin C7-T1, is a
continuation of the medial cord of the
brachial plexus. This nerve passes in the
same plane as the median nerve, between
the biceps and triceps muscles. At the
elbow, this nerve travels posterior to the
medial epicondyle of the humerus. Thismeans that condylar fractures can cause
lesion to this nerve.
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Blood supply and venous drainage
Arteries
The main artery in the arm is the brachial artery.
This artery is a continuation of the axillary artery.
The point at which the axillary becomes thebrachial is distal to the lower border of teres
major. The brachial artery gives off an important
branch, the profunda brachii (deep artery of the
arm). This branching occurs just below the lowerborder of the teres major.
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The brachial artery continues to the cubital
fossa in the anterior compartment of the
arm. It travels in a plane between thebiceps and triceps muscles, the same as
median nerve and bacillic vein. It is
accompanied by venae comitantes(accompanying veins). It gives branches to
the muscles of the anterior compartment.
The artery is in between the median nerve
and the tendon of the biceps muscle in the
cubital fossa. It then continues into the
forearm.
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The profunda brachii travels through
the lower triangular space with the
radial nerve. Frome here onwards ithas an intimate relationship with the
radial nerve. They are both found deep
to the triceps muscle and are located
on the spinal groove of the humerus.
Therefore fracture of the bone may not
only lead to lesion of the radial nerve,
but also hematoma of the internal
structures of the arm.
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The artery then continues on
to anastamose with thereeccurent radial branch of
the brachial artery, providinga diffuse blood supply for the
elbow joint.
V i
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Veins
The veins of the arm carry blood from the
extremities of the limb, as well as drain thearm itself. The two main veins are the
basilic and the cephalic veins. There is a
connecting vein between two, the mediancubital vein, which passes through the
cubital fossa and is clinically important for
venipuncture (withdrawing blood). The
basilic vein travels on the medial side of the
arm and terminates at the level of the
seventh rib.
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The cephalic vein travels on the
lateral side of the arm andterminates as the axillary vein.
It passes through the
deltopectoral triangle, a space
between the deltoid and the
pectoralis major muscles.
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Hand
The multi-fingered body parts normally located
at the end of each arm of a human or otherprimate. They are chief organs for physically
manipulating the environment, using
anywhere from the roughest motor skill(wielding a club) to the finest (threading a
needle), and since the fingertips contain some
of the densest areas of nerve endings on the
human body, they are also the richest sourceof tactile feedback so that sense of touch is
intimately associated with human hands.
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Digits
The four fingers on the hand are used for the
outermost performance; there four digits can befolded over palm which allows the grasping of
objects. Each finger, starting with one closest to
the thumb, has a colloquial name to distinguish it
from the others:
Index finger= pointer finger or forefinger
Middle finger
Ring finger
Little finger pinky
The thumb (connected to the trapezium) is located on
one of the sides, parallel to the arm.
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The articulations are:
Intercephangeal articulations of hand
Metacarpophalengeal joints
Intercarpal articulations
Wrist (may also be viewed as belongingto the forearm.)
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Leg
A limb or part of the body thatsupports the rest of the human
parts above the ground
between the ankle and hip and
is used for locomotion.
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Hip
Is the bony projection of the femur which
is known as the greater trochanter, and
the overlying muscle and fat. The hip
joint scientifically refered to as the
acetabulofemoral joint, is the jointbetween the femur and acetabulum of
the pelvis and its primary function is to
support the weight of the body in bothstatic (e.g standing) and dynamic (e.g
walking or running) postures.
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Ankle joint
Is formed where the foot and legmeet. The ankle, or talcrural joint, is
a synovial hinge joint that connects
the distal ends of the tibia and fibulain the lower limb with the proximal
end of the talus bone in the foot.
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Foot
It is the terminal portion of thelimb which bears weight and
allows locomotion. The foot is a
separate organ at the terminal
part of the leg made up of
bones, generally including thenails.
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Pelvic girdle
The appendicular skeleton and theaxial skeleton together form the
complete skeleton.
The pelvis or pelvic girdle is the
irregular bony structure located at
the base of the spine (properlyknown as the caudal end).
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Pelvic girdle
In the adult human, it is formed by the
sacrum and the coccyx, the caudal part of
the axial skeleton, and a pair of hip bones,
part of the appendicular skeleton or lower
extremity. Until puberty, however, each hip bone
consists of three separate bones yet to be
fused-the ilium, ischium, and the pubis- andthe pelvis is thus composed of up to five or
seven bones.
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Pelvic girdle
The ilium is the largest and uppermost part, the ischium is the
posterior-inferior (back lower)
part, and the pubis is the anterior(front) part of the hip bone. The
two hip bones are joined anteriorly
at the symphysis pubis and
posteriorly to the sacrum.
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Pelvic girdle
The pelvis incorporates the socketportion of the hip joint (the
acetabulum) for each leg (in
bipeds) or hind leg (in quadripeds).it forms the lower limb (or hind
limb) girdle of the skeleton.
During childbirth, child has to pass
through pelvic opening in women.
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Pelvic cavity
The pelvic cavity is a bodycavity that is bound by the
bones of the pelvis and which
primarily contains reproductive
organs and the rectum.
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Pelvic cavity
The lesser pelvis (or true pelvis)only includes structures inferior
to the pelvic brim. The greater
pelvis (false pelvis) is the
expanded portion of the cavity
situated above and in front ofthe pelvic brim.
diff i h l i
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Sex differences in human pelvis
Infrapubic angle is greater than 90 in
males.
Pelvic inlet in males is more heart-shaped,
while in females it is more round or oval.
Greater sciatic notch narrower in males.
Acetabulum in males faces more laterally,
while it faces more anteriorly in females.
Sacrum more triangular and shorter in
females.
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Four main types of pelvis
Gynaecoid: normal female pelvis,round with enlarged transverse
diameter.
Android: normal male pelvis, heart-shaped.
Anthropoid: long anterior to posterior
diameter.
Platypelloid: long transverse diameter.
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STRUCTURE IN HUMANSB. MUSCULAR
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Muscle
Muscle is a contractile tissue of the
body and is derived from the
mesodermal layer of embryonicgerm cells. Muscle cells contain
contractile filaments that move past
each other and change the size ofthe cell.
Their function is to produce force
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Their function is to produce force
and cause motion. Muscle can
cause either locomotion of the
organism itself or movement of
internal organs.
Cardiac and smooth muscle
contraction occurs withoutconscious thought and is
necessary for survivial.
Examples are the contraction of the
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Examples are the contraction of the
heart and peristalisis which pushes
food through the digestive system.
Voluntary contraction of the skeletal
muscles is used to move the bodyand can be finely controlled.
Examples are movements of the eye,
or gross movements like quadriceps
muscle of the thigh.
There are two broad types of
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There are two broad types of
voluntary muscle fibers: slow twitch
and fast twitch. Slow twitch fibers
contract for long periods of time but
with little force while fast twitchfibers contract quickly and
powerfully but fatigue very rapidly.
These are three types of muscles:
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These are three types of muscles:
Cardiac
This is a type of highly oxidative (using
molecular oxygen to generate energy)
involuntary striated muscle found in the
walls of the heart, specifically themyocardium.
Cardiac muscle cells are known as cardiac
myocytes. Cardiac muscles is one of threemajor types of muscle.
Th ll th t i di l
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The cells that comprise cardiac muscle are
sometimes seen as immediate between these
two other types in terms of appearance,structure, metabolism, excitation-coupling and
mechanism of contraction. Cardiac muscle
shares similarities with skeletal muscle with
regard to its striated appearance andcontraction, with both differing significantly
from smooth muscle cells.
Coordinated contraction of cardiac muscle cells
in the heart propel blood from the atria and
ventricles to the blood vessels of the circulatory
system.
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Cardiac muscle cells, like all
tissues in the body, rely on anample blood supply to deliver
oxygen and nutrients and to
remove waste products such ascarbon dioxide. The coronary
arteries fulfill this function.
Skeletal
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Skeletal muscle or voluntary muscle is
anchored by tendons to bone and is used to
effect skeletal movement such as locomotion
and in maintaining posture. Through this
postural control is generally maintained as
subconscious reflex, the muscles responsiblereact to conscious control like non-postural
muscles.
An average adult male is made up of 40-50% of
skeletal muscle and an average adult female ismade up of 30-40% (as a percentage of body
mass).
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Skeletal muscle is further divided
into several subtypes:Type I, slow oxidative, slow twitch, or
red muscle is dense with capillaries
and is rich in mitochondria andmyoglobin, giving the muscle tissue its
characterisitic red color. It can carry
more oxygen and sustain aerobicactivity.
Type II, fast twitch muscle, has three major kinds
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yp j
that are, in order of increasing contractile speed.
Type IIa, which like slow muscle, is aerobic, rich
in mitochondria and capillaries and appears
red.
Type IIx, (also known as type IId) which is less
dense in mitochondria and myoglobin. This isthe fastest muscle type in humans. It can
contract more quickly and with a greater
amount of force than oxidative muscle, but can
only sustain short, anaerobic bursts of activitybefore muscle contraction becomes painful
(often incorrectly attributed to a build-up of
lactic acid).
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Type IIb, which is anaerobic,
glycolytic, whitemuscle that iseven less dense in mitochondria
and myoglobin. In small animalslike rodents this is the major fast
muscle type , explaining the pale
color of their flesh.
S th
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Smooth
Smooth muscles are used to control the flow of
substances within the lumens of hollow organs,and are not consciously controlled. Skeletal and
cardiac muscles have striations that are visible
under a microscope due to the components
within their cells. Only skeletal and smooth
muscles are part of the musculoskeletal system
and only the skeletal muscles can move the
body. (cardiac muscle are found in the heartand are used exclusively to circulate blood; like
the smooth muscles, these muscles are not
under conscious control)
Contraction initiation
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Contraction initiation
When a muscle contracts, a series of reactionsoccur. Muscle contraction is stimulated by themotor neuron sending a message to themuscles from the somatic nervous system.
Depolarization of the motor neuron results inneurotransmitters being released from thenerve terminal. The space between the nerve
terminal and the muscle cell is calledneuromusclular junction.
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These neurotransmitters diffuse
across the synapse and bind tospecific receptor sites on the cell
membrane of the muscle fiber. When
enough receptors are stimulated, anaction potential is generated and the
permeability of the sarcolema isaltered. This process is known as
initiation.
Joints
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Joints
Joints are structures that connect individualbones and may allow bones to move against
each other to cause movement. These are two
divisions of joints, diarthroses which allowsextensive mobility between two or more
articular heads, and false joints or
synarthroses that allow little or no movementand are predominantly fibrous.
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Synovial joints are lubricated by a
solution called synovia that is produced
by the synovial membranes. This fluid
lowers the froction between the articular
surfaces and is kept within an articular
capsule, binding the joint with its taut
tissue.
Diarthroses
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Diarthroses
Synovial joint are the most common
and most movable type of joints in the
human body. As with most other
joints, synovial joints achievemovement at the point of contact of
the articulating bones.
Synarthroses
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Synarthroses
A type of joint which permits very little
or no movement under normal
condition. Most synarthrosis joints are
fibrous. Suture joints and
synchroondroses are synarthroses.
S i l b
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Synovial membranes
Synovial membrane id the soft tissuethat lines the non-cartilagenous
surface within joints with cavities
(synovial joints).
Tendons
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Tendons
A tendon is tough, flexible band of fibrousconnective tissue that connects muscles to
bones. Muscles gradually become tendon as
the cells become closer to the origins andinsertions on bones, eventually becoming
solid bands of tendons transmitt the forces to
the rigid bones, pulling on them and causing
movement.
Fibrous connective tissue
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Fibrous connective tissue
A type of connective tissue which has
relatively high tensile strength, due to a
relatively high concentration of
collagenous or elastic fibers. Scuh tissues
from ligaments and tendons; the majorityof the tissue does not contain living cells,
and is primarily composed of
polysaccharides, proteins, and water.Fibrous connective tissue is found ajacent
to the Mllersmuscle
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Periosteum
Periosteum is a membrane that lines theouter surface of all bones, except at the
joints of long bones. Endosteum lines the
inner surface of all bones. Periosteumconsists of the irregular type of dense
conncetive tissue. Periosteum is divided
into an outer fibrous layer and inner
cambiumlayer(also osteogenic layer)
h fib l i fib bl
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The fibrous layer contains fibroblasts
while the cambium layer contains
progenitor cells which develops into
osteoblasts. These osteoblasts are
responsible for increasing the width of a
long bone and the overall size of theother bone types. After a bone fracture,
the progenitor cells develop into
osteoblasts and chondroblasts which areessential to healing process.
Ligaments
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A ligaments is a small band of dense ,
white, fibrous elastic tissue. Ligamentsconnect the ends of bones together in
order to form a joint.
Most ligaments limit dislocation, orprevent certain movements that may
cause breaks. Since they are only elastic
they increasingly lengthen when under
pressure. When this occurs the ligament
may be susceptible to break resulting in
an unstable joint.
Three different types of structures:
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Three different types of structures:
Fibrous tissue that connects bones toother bones. They are sometimes
called articular ligaments, fibrous
ligamentsor trueligamentsA fold of peritoneum or other
membrane
The remnants of a tubular structurefrom the fetal period of life.
Bursa
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Bursa
A bursa is a small fluid-filled sac
made of white fibrous tissue and
lined with synovial membrane. It
provides a cushion between bonesand tendons and/ or muscle around
a joint; bursae are filled with synovial
fluid and are found around almostevery major of the body.