Download Skeletal Notes - Part 5

Skeletal Notes - Part 5
Bony Thorax
 The bony thorax is made up of the:
1.
Sternum
2.
Ribs
3.
Thoracic vertebrae

Often called the
“thoracic cage.”

It forms a protective,
cone-shaped cage of
slender bones around
the organs of the
thoracic cavity (heart,
lungs, and major blood vessels).
Sternum
 The sternum
(breastbone) is a typical
flat bone and the result
of the fusion of three
bones:
1.
2.
3.
Manubrium
Body
Xiphoid Process
 The sternum is attached
to the first 7 pairs of ribs.
Ribs
 Twelve pairs of ribs form
the walls of the thoracic
cage.

Contrary to popular
misconception, males do not
have one less rib than females!
 All the ribs articulate with
the vertebral column
posteriorly and then curve
downward toward the
anterior body surface.
Ribs
 True Ribs – Attach directly
to the sternum by costal
cartilages; The first seven
pairs.
 False Ribs – Either attach
indirectly to the sternum or
are not attached to the
sternum at all; The next five
pairs of ribs.

Floating Ribs – Lack a sternal
attachment; Last two pairs of
the false ribs.
Intercostal Spaces
 Intercostal Spaces -
Spaces between the ribs.

Are filled with the intercostal
muscles that aid in breathing.
Appendicular Skeleton
 It is composed of 126 bones of the
limbs and the pectoral and pelvic
girdles, which attach the limbs to
the axial skeletal.
Bones of the Shoulder Girdle
 Each shoulder girdle
(pectoral girdle) consists of
two bones:
1.
2.
Clavicle
Scapula
Clavicle
 Clavicle – Collarbone;
slender doubly curved bone.

Attaches:
To the sternum medially
 To the scapula laterally, where it
helps to form the shoulder joint.


Acts as a brace to hold the arm
away from the top of the thorax
and helps prevent shoulder
dislocation.

When the clavicle is broken, the
whole shoulder region caves in
medially, which shows how
important its bracing function is.
Scapulae
 Scapulae – Shoulder blades.


Not directly attached to the axial skeleton;
is loosely held in place by trunk muscles.
Each scapula has a flattened body and two
important processes:
1.
Acromion – The enlarged end of
the spine of the scapula.
• The acromion connects with the
clavicle laterally at the acromioclavicular joint.
2.
Coracoid Process – Beaklike process.
• The coracoid process points over
the top of the shoulder and anchors some
of the muscles of the arm.
The Shoulder Girdle
 Is very light and allows the
upper limb to have exceptional
free movement because:
1.
2.
3.
Attaches to the axial skeleton at
only one point – the
sternoclavicular joint.
The loose attachment of the
scapula allows it to slide back
and forth against the thorax as
muscles act.
The glenoid cavity is shallow,
and the shoulder joint is poorly
reinforced by ligaments.
 However, this exceptional
flexibility also has a drawback,
the shoulder girdle is easily
dislocated.
Bones of the Upper Limbs
 30 separate bones form the skeletal
framework of each upper limb.
 They form the foundations of the arm,
forearm, and hand.
Arm
 The arm is formed by a
single bone, the humerus,
which is a typical long
bone.

At its proximal end is a
rounded head that fits into the
shallow glenoid cavity of the
scapula.
Forearm
 Two bones form the
skeleton of the forearm:
1.
2.
Radius – The lateral bone,
when the body is in
anatomical position; on the
thumb side of the forearm.
Ulna – The medial bone,
when the body is in
anatomical position; on the
little finger side of the
forearm.
Radius and Ulna
 Both proximally and distally, the
radius and ulna articulate at small
radioulnar joints.
 The two bones are connected
along their entire length by the
flexible interosseous membrane.
Hand
 The skeleton of the hand
consists of:
1.
2.
3.
The carpals
The metacarpals
The phalanges
Hand: Carpals
 The eight carpal bones
form the part of the hand
called the carpus or the
wrist.


The carpal bones are
arranged in two irregular
rows of four bones each.
The carpals are bound
together by ligaments that
restrict movements between
them.
Hand: Metacarpals
 The palm of the hand
consists of the
metacarpals.


The metacarpals are
numbered 1-5 from the
thumb side of the hand
toward the little finger.
When the fist is clenched,
the heads of the
metacarpals become
obvious as the “knuckles.”
Hand: Phalanges
 The phalanges are the
bones of the fingers.


Each hand contains 14
phalanges.
There are three phalanges
in each finger (proximal,
middle, and distal) except
for the thumb, which has
only two (proximal and
distal).