Chapter 1-Musculoskeletal System

8/11/2019 Chapter 1-Musculoskeletal System

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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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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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system

Auditory ossicles

Ossicles (6)

Malleus (2)

Incus (2)

Stapes (2)


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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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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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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.

f l


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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

M l


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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.

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Chapter 1-Musculoskeletal System