Joints pdf - Dr.Rana Al-tae

Anatomy Lecture 3

Introduction to Bone

and Joints

Dr. Rana Al-tae

2015-2016

Anatomy of a Bone

• The structure of a bone is analyzed by

considering the parts of a long bone as
the humerus ( arm bone ) and the femur
( thigh bone). A long bone is the one that
has greater length than width. A typical
long bone consists of the following parts:

The

diaphysis

is the bone's shaft or body-

the long, cylindrical, main portion of the

bone.

The

epiphyses

are the proximal and distal

ends of the bone (the singular is epiphysis).

The

metaphyses

are the regions in a mature

bone where the diaphysis joins the

epiphyses ( the singular is metaphysis). In a

growing bone the metaphyses are regions

that include the

epiphyseal plate

which is a

plate of hyaline cartilage that allow the

growth of the diaphysis in length but not in

width. When the bone growth in length

stops, the cartilage in the epiphyseal plate is

replaced by bone and the resulting bony

structure is known as the

epiphyseal line

The

articular cartilage

is a thin layer of

hyaline cartilage that covers each epiphysis

where the whole bone forms an articulating

joint with another bone. Articular cartilage

reduces friction and absorbs shock at freely

movable joints.

5. The

Periosteum

is a layer of

connective tissue that covers the
bone surface wherever there is
no articular cartilage. It helps the
bone to grow in width, protects
the bone and nourishes it, helps
in repair in fractures and serves
as an attachment point for
ligaments and tendons.

6. The

medullary cavity

or marrow

cavity is the space within the
diaphysis that contain the fatty
yellow bone marrow in adults.

7. The

Endosteum

is a thin

membrane that lines the
medullary cavity.

Joints

• Introduction

• Bones are too rigid to bend without being damaged.

Fortunately, flexible connective tissues forms joints

that hold bones together permitting some degree of

movement. A joint (articulation) is a point of contact

between two bones, between bone and cartilage or

between bone and teeth. When we say one bone

articulate with another bone we mean that the bones

form a joint. Because most movements of the body

occur at joints, You should appreciate their importance

if you imagine how a cast over your knee joint makes

walking difficult or how a splint on your finger limits

you ability to manipulate small objects.

• Some joints permit no movement, others permit slight

movement and others afford fairly free movement.

Joint classification

• The joints in the body are classified according to their

structure and to their function.

1. Structural classification

of joints depends on the type

of connective tissue that combines the bones
together and whether there is a space between the
articulating bones or not ( synovial cavity) and this
classification is as the following:

2. Fibrous joints

: the bones are held together by fibrous

connective tissue and the is no synovial cavity.

3. Cartilaginous joints

: the bones are held together by

cartilage and the is no synovial cavity.

4. Synovial joints

: the bones are held together by

capsule and ligaments and there is a synovial cavity.

• Functional classification

of the joints relates to

the degree of movement they permit as the
following:

1. Synarthrosis

: An immovable joint.

2. Amphiarthrosis

: A slightly movable joint.

3. Diarthrosis

: A freely movable joint.

• NOTE: all Diarthrosis are Synovial joints.

Types of fibrous joints :

1. Sutures

: as the

sagittal suture or the
coronal suture of the
skull which is
immovable so they
are classified
functionally as
synarthrosis

Types of fibrous joints :

2. Syndesmoses

: (band or

ligament) is a fibrous joint in
which there is a greater
distance between the
articulating bones and more
fibrous connective tissue than
in sutures. Ex. The interossous
membrane between the
parallel borders of radius and
ulna bone ( middle radioulnar
joint)

Types of fibrous joints :

• and between the parallel

borders of the tibia and fibula
( middle tibiofibular joint).
Because it allows slight
movement it is classified
functionally as an
amphiarthrosis.

Types of fibrous joints :

3. Gomphosis

: is a type of

fibrous joint in which a
cone-shape peg fits into
a socket. The only
example in the body is
the roots of teeth and
their sockets in the
maxilla and the
mandible bones. A
gomphosis is classified
functionally as a
synarthrosis, an
immovable joint.

Types of cartilaginous joints :

1. Synchondroses

: example

is the epiphyseal plate
that connects the
epiphysis with the
diaphysis of the long
bone. Other ex. Is the
joint between the first
rib and the sternum
bone. Functionally it is
classified as a
synarthrosis.

Types of cartiligenous joints :

2. Symphyses

: in which the ends

of the articulating bones are

covered by hyaline cartilage, but

the bones are connected by a

broad, flat disc of fibrocartilage.

All symphyses are present in the

midline of the body, ex: The joint

between the manibrium and the

body (parts ) of the sternum, the

joint between the two hip bones

called pubic symphyses, the

joints between the bodies of the

vertebrae forming the

intervertebral joints. A

symphysis is an amphiarthrosis,

slightly movable joint.

Synovial Joints

• They have a space called the

synovial (joint) cavity between
the articulating bones. The
structure of these joints allows
the bones to move freely, so
all of them are diarthrosis. The
bones at the synovial joint are
covered by

articular cartilage,

which is hyaline cartilage. This
cartilage provides a smooth,
slippery surface for the
articulating bones, but it does
not bind them together. It
reduces the friction between
the bones of the joint during
movement and helps to
absorb shock.

• There is also the

articular

capsule

surrounds a synovial

joint, encloses the synovial
cavity and unites the
articulating bones. It is
composed of two layers, an
outer fibrous capsule and an
inner synovial membrane.
The outer layer is fibrous,
tougher than the inner layer
and attaches to the
periosteum of the
articulating bones, while the
inner layer is areolar with
elastic fibers.

• The

synovial fluid

is secreted from the synovial

membrane, it is a thin film of fluid present in
the synovial (joint) cavity, viscous, clear or
pale yellow fluid similar in appearance and
consistency to uncooked egg white or
albumin. It consists of hyaluronic acid. Its
several functions are reducing friction,
lubricating the joint, supplying nutrients and
removing waste products and has phagocytic
cells that remove microbes and debris that
result from tear in the joint. When a synovial
joint is immobile the synovial fluid becomes
gel-like but as joint movement increases the
fluid becomes less viscous.

• Many synovial joints also contain

accessory

ligaments

called extra capsular ligaments and

intracapsular ligaments. The extra capsular
ligaments lies outside the articular capsule ,
while the intra capsular ligaments lies within
the articular capsule but are excluded from
the synovial cavity by folds of the synovial
membrane.

Nerve and Blood supply of the joint:

• The nerves that supply a joint are the same as those

that supply the skeletal muscles that move the joint.

Some nerve endings convey information about pain

in the joint, others are responsive to the degree of

movement and stretch at a joint.

• Also nearbying arteries are responsible for nourishing

the joint with oxygen and nutrients and the veins

carry out carbon dioxide and waste products from

the joint. The arteries send out numerous branches

that penetrate the ligaments and articular capsule.

We should know that the articulating portions of the

synovial joint receives its nourishment from the

synovial fluid whereas all other joint tissues are

supplied by blood capillaries.

Types of synovial joints:

• Although all synovial joints are similar in

structure, the shapes of the articulating
surfaces vary. Accordingly, synovial joints
are divided into six subtypes:

Planer,

Hinge, Pivot, Condyloid, Saddle, and ball-
and-socket joints.

Types of synovial joints:

Planer joints

: the articular surfaces

of bones are flat or slightly curved.

These joints permits side-to-side

and back-and-forth gliding

movements. These joints are said

to be nonaxial joints because the

motion they allow does not occur

around an axis or plane (line). Ex:

the intercarpal joints (between the

carpal bones at the wrist ) and the

intertarsal joints ( between the

tarsal bones of the ankle), the

sternoclavicular joint between the

manubrium part of the sternum

with the sternal end of the clavicle

bone, the sternocostal joints

between the body part of the

sternum and the ends of the costal

cartilages at the tips of the 2

- 7

pairs of ribs, and the

vertebrocostal joints between the

heads of all ribs with the vertebrae

of the thoracic region.

Types of synovial joints:

2. Hinge joints:

the convex

surface of one bone fits
into the concave surface of
the another bone. As the
name implied, hinge joints
produce an angular
opening and closing motion
like that of a hinged door.
Hinge joints are said to be a
monoaxial or uniaxial joints
because permits movement
in only one single axis. Ex.
Are the knee, elbow, ankle,
and interphalangeal joints.

Types of synovial joints:

3. Pivot joints

: the rounded

or pointed surface of one
bone articulates with a
ring formed partly by
another bone and partly
by a ligament. A pivot joint
is a uniaxial because it
allows movement around
a longitudinal axis only.
EX: the atlantoaxial joint in
which the atlas bone
rotates around the axis
bone giving the" no"
movement of the head.

Types of synovial joints:

4. Conyloid joints :

(Ellipsoidal joint) a convex
oval surface of one bone
fits into a convex oval
surface of the other bone.
Ex: Metacarpophalangeal
joints of the 2

-5

digits.

Condyloid joints are biaxial
joints because they allow
movements around two
axis. notice that your index
finger can be moved from
side-to-side and up and
down.

Types of synovial joints:

5. Saddle joints

: the articular

surface of one bone is

saddle shaped and the

articular surface of the

other bone fits into the

"saddle" as a sitting rider

would sit. a saddle joint is a

modified condyloid joint in

which the movement is

somewhat freer. They are

biaxial producing side-to-

side and up and down

movement. Ex: the joint in

the thumb between the

trapezium bone (one of the

carpal wrist bones) and the

metacarpal of the thumb.

Types of synovial joints:

6. Ball-and –socket joints

consists of a ball-like
surface of one bone
fitting into a cuplike
depression of another
bone. Such joints are
multiaxial (polyaxial)
because they allow
movements in many
axis. Ex: shoulder joint
and Hip joint.

Types of Movements at synovial joints:

• Anatomists, Physical therapists use specific

terminology to design movements that can occur at
synovial joints. These precise terms may describe
the direction of movement or the relationship of
one part of the body to another. The movements are
grouped into four main categories:

1. Gliding
2. Angular movements.
3. Rotation.
4. Special movements.

• This last category includes movements that only

occur at certain joints.

Gliding

• Is a simple movement in

which the relatively flat
bone surfaces moves
from side to side, back
and forth with respect to
one another. This
movement is limited
according to the articular
capsule and the strength
of the surrounding
ligaments. Gliding occurs
at plane joints.

Angular movements

• There is an increase or decrease in the

angle between the articulating bones.
The principle angular movements are

flexion, extension, lateral flexion ,
hyperextension, abduction, adduction
and circumduction.

These movements

are discussed in respect to the body in
the anatomical position.

Angular movements

• Flexion

and

extension

are

opposite movements. in

flexion there is decrease in

angle between the articulating

bones while in extension there

is an increase in the angle.

(flexion=bend,

extension=strech out).

Extension usually restores the

part of the body to the

anatomical position after it

has been flexed. EX: tilting the

head downward to the chest

(flexion) and returning it back

to its normal position

(extension). Other EX:

(Homework).

Angular movements

• Lateral flexion

means

movement of the
trunk to the right or
left at the waist and
this involves the
intervertebral joints.

• Hyperextension

means continuation of
extension beyond the
anatomical position.
Ex: bending the head
backward at the
cervical intervertebral
joint. Other EX: (Home
work).

Angular movements

• Abduction

is the movement

away from the midline whereas

adduction

is the movement

toward the midline Ex: moving
the arm laterally at the shoulder
joint is abduction while
returning it back to its normal
anatomical position is
adduction. Other Ex: (Home
work).

Angular movements

• Note that abduction and

adduction of the fingers
and toes are movements
away and towards an
imaginary line drawn
through the longest
middle finger in the hand
and the second toe in the
foot. So spreading out the
fingers is abduction while
returning them back to
their normal anatomical
position is adduction.

Angular movements

• Circumduction

is the

movement of the distal
end of the body around a
circle, it’s a result of a
continuous sequence of
flexion, abduction,
extension and adduction.
Ex: moving the arm in a
circle at the shoulder
joint. Other Ex: (Home
work).

• Rotation

means that the bone revolves around

its own longitudinal axis EX: as in pivot joint,
and moving the trunk from side to side at the
intervertebral joints while keeping the hips
and the lower limbs in their anatomical
position. In the limbs , rotation is defined
relative to the midline and specific qualifying
terms are used. If the anterior surface of the
limb is turned toward the midline, the
movement is called

medial (internal) rotation

If the anterior surface of the limb is turned
away from the midline, the movement is
called

lateral (external ) rotation

• Special movements occurs only at

specific joints. They include

elevation,

depression, protraction, retraction,
inversion, eversion, dorsiflexion, planter
flexion, suppination, pronation, and
opposition.

• Elevation

is an upward

movement of a part of the
body, such as closing the
mouth at the
tempromandibular joint
or shrugging the
shoulders at one of the
lateral joint of the clavicle.

• Depression

is a downward

movement of a part of a
body, such as opening the
mouth ton depress the
mandible or returning the
shrugged shoulders to
their anatomical position.

• Protraction

is a

movement of a part of
the body anteriorly (to
draw froth) as in protract
the mandible at the
tempromandibular joint
by thrusting it outward,
or protract your clavicles
by crossing your arms.

• Retraction

is the

movement of the
protracted part of the
body back to the
anatomical position. (to
draw back)

• Inversion

( to turn inward )

is movement of the soles
medially at the intertarsal
joints (between the
tarsals)

• Eversion

(to turn outward )

is the movement of the
soles laterally at the
intertarsal joints.

• Dorsiflexion

refers to

bending of the foot at the
ankle in the direction of the
dorsum (superior surface).
Dorsiflexion occurs when
you stand on your heels.

• Planter flexion

refers to

bending of the foot at the
ankle joint in the direction
of the planter or inferior
surface (sole), as when
standing on your toes.

• NOTE: dorsiflexion is true

flexion, whereas planter
flexion is true extension.

• Supination

is a movement

of forearm at the proximal
and distal radioulnar
joints in which the palm is
turned anteriorly or
superiorly. This position is
one of the defining
features of the anatomical
position.

• Pronation

is the

movement of the forearm
at the proximal and distal
radioulnar joints in which
the palm is turned
posteriorly or inferiorly.

• Opposition

is the

movement of the thumb
at the carpometacarpal
joint in which the thumb
moves across the palm to
touch the tips of the
fingers on the same
hand. This gives the
ability to grasp and
manipulate objects very
precisely.

• The end….