lec6 anatomy

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Anatomy Dr.Israa H. Mohsen
Lecture 6
Joints
Joints—also called articulations—are points where bones meet. Some joints are
completely immovable; others allow only limited movement. Most joints, however,
permit considerable movement. Through the interaction of multiple interconnecting
parts, these incredible structures allow the body to walk, run, dance, throw a ball, and
even type on a computer.
Joints may be classified according to how movable they are: fixed, semi-movable, or
freely movable. They may also be classified according to the material that binds them
together. For example, fixed joints are bound by fibers and are called fibrous joints;
semi-movable joints are joined by cartilage and are called cartilaginous joints; freely
movable joints contain a fluid-filled joint capsule and are called synovial joints.
Fibrous Joints
Fibrous joints—also called synarthroses—result when collagen fibers from one
bone penetrate the adjacent bone, anchoring the bones in place.
Cartilaginous Joints
In cartilaginous joints, two bones are joined by cartilage. These joints—called
amphiarthroses—are slightly movable.
The adult skull’s suture joints
are fibrous joints:
once growth is complete, the
bones of the skull knit together
securely, offering protection to
the brain.
Fibrocartilaginous pads (called
intervertebral discs) reside
between each vertebrae, making
the vertebrae of the spine
cartilaginous joints. These pads
of cartilage absorb shock and
allow for limited movement.
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Synovial Joints
Synovial joints—also called diarthroses—are freely movable. They’re also the most
numerous and versatile of all the body’s joints. Every synovial joint contains the
following structures:
Bursae in Synovial Joints
Some joints—such as the knee, shoulder, and elbow—contain small sacs filled with
synovial fluid called bursa (plural: bursae). Residing in areas where muscles and
tendons pass over bony prominences, the bursae facilitate movement and ease
friction.
Joint capsule: is a sheet of
connective tissue that encloses
the joint cavity.
Synovial membrane: This
moist, slippery membrane lines
the inside of the joint capsule,
where it secretes synovial fluid.
Joint cavity: This small space between
the bones allows for freedom of
movement. It also contains synovial
fluid, a slippery, viscous fluid that has
the consistency of an egg white.
Synovial fluid lubricates the joint,
nourishes the cartilage, and contains
phagocytes to remove debris
Articular cartilage: A thin layer of
hyaline cartilage covers the bone
surfaces. In combination with synovial
fluid, the articular cartilage permits
friction-free movement.
Ligaments: Tough cords of connective
tissue help bind the bones more firmly
together.
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Movements of Synovial Joints
The movements a joint can make depend upon the shape of the joint (as previously
discussed) as well as the involvement of nearby muscles, tendons, and ligaments.
Flexion and Extension
Flexion
Extension
Hyperextension
Dorsiflexion
Plantar flexion
Abduction and Adduction
Abduction
Adduction
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Circumduction
Internal rotation
External rotation
Supination
Inversion
Protraction
Pronation
Eversion
Retraction
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MUSCULAR SYSTEM
Muscles are a unique form of tissue that transform energy into motion. Everything
your mind conceives is transmitted to your muscles to perform. The words you speak,
the expression on your face, the motion of your fingers as you write or play an
instrument are possible only because of muscular movement. Even more, muscles
operate behind the scenes to propel blood through blood vessels, drive the flow of air
into and out of the lungs, digest food, and produce body heat. Indeed, this
sophisticated tissue helps sustain life.
The body contains three types of muscle: cardiac muscle, smooth muscle, and skeletal
muscle.
Cardiac Muscle
• Found only in the heart
• Consists of short, branching fibers that fit together at
intercalated discs
• Appears striped, or striated, when viewed under a microscope
• Is a type of involuntary muscle because it contracts
automatically
Smooth Muscle
• Found in the digestive tract, blood vessels, bladder, airways, and
uterus
• Does not appear striped when viewed under a microscope, so is
called nonstriated
• Known as involuntary muscle, because it contracts automatically
(such as when the digestive
tract processes food)
Skeletal Muscle
• Attached to bone and causes movement of the body
• Known as voluntary muscle because it can be contracted at will
• Appears markedly striated when examined with a microscope
Muscles of the Head and Neck
Muscles in this region are typically grouped according to their function: muscles of
facial expression, muscles of chewing (called mastication) and swallowing, and
muscles that move the head.
Of all the muscles of the face, the area around the mouth is the most complex. This
makes sense considering that the mouth is the most expressive part of the face; the
movement of the lips is also pivotal in the formation of words. Besides contributing to
facial expression, the muscles of the face allow us to speak, chew, and perform other
oral functions.
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Muscles Involved in Breathing
Muscles are the driving force behind our ability to breathe
Muscles of Facial
Expression
1. Frontalis
2. Orbicularis oculi
3. Zygomaticus
4. Orbicularis oris
Buccinator (shown
on the other side of
the face):
Assists in smiling and
blowing
Muscles That Move The
Head
1.Sternocleidomastod
2.Trapezius
Muscles of Chewing
Temporalis
Masseter
Internal intercostals
Diaphragm
External intercostals
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Muscles Forming the Abdominal Wall
abdominal wall derives its strength from alternating layers of muscle. The muscle
fibers in each of the three layers forming the abdominal wall run in different
directions
Muscles of the Shoulder and Upper Arm
The shoulder and upper arm perform a wide variety of movements. Some
movements—such as throwing a ball or swimming—require power and a full range of
motion. Others, such as writing, depend upon more subtle movements. To make these
motions possible, the shoulder draws on a complex variety of muscles. A few of those
muscles are illustrated in the figure below.
Rectus abdominis
Transversus abdominis
Linea alba Internal oblique
(white line).
External oblique
Deltoid: Abducts, flexes, and
rotates the arm
Pectoralis major: Flexes and
adducts the upper arm
Serratus anterior: Drives all
forward-reaching and pushing
movements; pulls the shoulder
down and forward
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Muscles That Move the Forearm
The muscles that flex and extend the forearm are located on the humerus.
Pronator muscles allow
the arm to pronate
Brachioradialis: Helps the
brachialis and the biceps
brachii flex the forearm
Triceps brachii: The prime
mover when extending the
forearm
Brachialis: The prime
mover when flexing the
forearm
Biceps brachii: Assists
the brachialis when
flexing the forearm; also
flexes the elbow and
supinates the forearm
Trapezius: Raises
and lowers the
shoulders; stabilizes
the scapula during
arm movements
Latissimus dorsi:
Adducts the
humerus; extends
the upper arm
backward
Rotator cuff: The
tendons of four
muscles (attached to
the scapula) form the
rotator cuff. They are
the:
• supraspinatus
• infraspinatus
• teres minor and
• subscapularis (on
the anterior scapula)
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Muscles Acting on the Hip and Thigh
the legs are built for stability and power. The muscles of the hip and thigh enable the
body to stand, walk, and maintain balance.
The iliopsoas flexes the thigh
The term iliopsoas refers to a
combination of the following
muscles:
• Iliacus
• Psoas major
The sartorius is the longest
muscle in the body. It aids in
flexion of the hip and knee
(such as when sitting) and
abducts and laterally rotates
the thigh
The adductor muscles rotate
and draw the thigh in toward
the body (adduction).
This group consists of the
following muscles:
• Adductor magnus
• Adductor brevis
• Adductor longus
• Gracilis
The quadriceps femoris—the
most powerful muscle in the
body—is the prime mover for
knee extension. It consists of four
muscles, although only
three are visible here. The fourth,
the vastus intermedius, lies
underneath the rectus femoris.
• Rectus femoris
• Vastus lateralis
• Vastus medialis
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Muscles Acting on the Foot
Muscles in the lower leg are primarily responsible for moving the foot and ankle.
The gluteal muscles
consist of the following
three muscles:
Gluteus medius: Abducts
and rotates the thigh
outward
Gluteus maximus: The
bulkiest muscle in the
body; it produces the
backswing of the leg when
walking and provides most
of the power for climbing
stairs
Gluteus minimus: This
muscle lies beneath the
The hamstrings are a group of other two gluteal muscles
muscles consisting of the following
three muscles, all of which work to
extend the thigh at the hip, flex the
knee, and rotate the leg.
Biceps femoris
Semitendinosus
Semimembranosus
Gastrocnemius
Soleus
Contraction of these
muscles causes
plantar flexion of the foot
calcaneal (Achilles) tendon.
It inserts on the calcaneus (heel
bone).
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Muscles on the anterior of the lower leg also participate in moving the foot and ankle.
The extensor digitorum longus
and the tibialis anterior
dorsiflex the foot, keeping the
toes from dragging the ground
when walking. The extensor
digitorum longus also extends
the toes and turns the foot
outward (eversion).
Tibialis anterior
Extensor digitorum longus
The muscles of the lower leg
pull on tendons that attach to
the bones of the foot. The
foot also contains numerous
smaller muscles that act to
flex and extend the toes.