The Skeletal System
206 Bones in t he Human Skeleton
2
Bones are Organs Each bone is a complex living organ made up of
many cells, protein fibers, and minerals.
They come in many sizes and shapes.
The largest bone is the femur and the smallest is
the stapes.
The humerus is pictured here.
3
The Skeletal System Also Includes
Joints
Cartilages
Ligaments
4
Anatomy of the
Skeletal System
5
Two Divisions of the Skeleton
Axial Skeleton &
Appendicular Skeleton6
Axial Skeleton
Bones that form the longitudinal axis of the body make up the axial skeleton
Vertebral Column Vertebrae Sacrum Coccyx
Bony Thorax Ribs Sternum
Skull Cranium Facial Bones
7
Axial Skeleton
Vertebral
Column
Bony Thorax or
Rib Cage
Skull
8
Vertebral Column
Composed of 33 bones
before birth; some later fuse
to form 26 separate bones
7 cervical vertebrae (red)
12 thoracic vertebrae (blue)
5 lumbar vertebrae (yellow)
Sacrum – 5 fused (green)
Coccyx – 4 fused (purple)
9
Structure of a Vertebrae
10
Cervical Vertebrae
7 vertebrae
located in the
neck
Smallest and
lightest
vertebrae
11
Atlas & AxisThe first vertebra is
called the atlas, C1.
The second vertebra
is called the axis, C2.
12
Thoracic Vertebrae
12 thoracic
vertebrae
Articulate with ribs
Larger than
cervical vertebrae
Long spinous
process that hooks
sharply downward
13
Lumbar Vertebrae
5 lumbar
vertebrae
Much larger
than other
vertebrae to
support the
weight of the
upper body 14
Bony Thorax or Rib Cage 12 pairs of ribs articulate with
the 12 thoracic vertebrae
posteriorly
True ribs, pairs 1-7 (red),
articulate anteriorly directly to
the sternum by cartilage
False ribs, pairs 8-12 (green &
blue), articulate indirectly or not
at all
The last 2 pair do not connect at
all and are called floating ribs
(blue). 15
Sternum
Manubrium
Body
Xiphoid
Process16
The Skull� The skull is
for med by t wo
set s of bones:
� Cranium
� Facial bones
� All are j oined by
immovable j oint s
except for t he
mandible
(j awbone)
17
Lateral View of Skull
18
Hyoid Bone No direct articulation
to another bone
Provides attachment
for these muscles:
Floor of mouth
Tongue
Larynx
Epiglottis
Pharynx
19
Auditory Ossicles
The smallest
bones in the
body are
located in the
middle ear:
Malleus
Incus
Stapes
20
Appendicular Skeleton
Includes the
limbs and the
girdles which
attach the
limbs to the
axial skeleton
Pectoral (Shoulder) Girdle
Collar bones
Shoulder blades
Upper Limbs
Arms
Hands
Pelvic (Hip) Girdle
Coxal Bones
Lower Limbs
Legs
Feet
21
Appendicular Skeleton
Pectoral Girdle: clavicle, scapula
Upper Limbs: humerus, ulna, radius, carpals, metacarpals, phalanges
Pelvic Girdle: ilium ischium, and pubis
Lower Limbs: femur, patella, tibia, fibula, tarsals, metatarsals, phalanges
22
Pectoral Girdle
The clavicle is
commonly
called the collar
bone.
The scapula is
commonly
called the
shoulder blade.
23
Arm Bones
• Humerus: Upper Arm
Bone
• Radius: elbow to thumb
side of the wrist
• Ulna: elbow to pinkie side
of the wrist
24
Bones of the Hand
Carpals
Metacarpals
Phalanges
25
Pelvic Girdle The pelvic girdle
consists of two
coxal or hip bones.
Each hip bone is
formed from the
fusion of 3 bones:
Ilium
Ischium
Pubis
26
The Coxal Bones
27
Leg Bones Femur – thigh bone
Patella – knee cap
Tibia – large bone in
lower leg;
sometimes called
the shin bone
Fibula – smaller
bone in lower leg;
forms the lateral
ankle
28
Bones of the Foot
Tarsals
Metatarsals
Phalanges
29
Shape
s of
Bones• Long
• Short
• Flat
• Irregular
• Sesamoid
Flat Irregular
Long
Short
Sesamoid
30
Two Basic Types of Bone Compact Bone is dense
and looks smooth and
homogeneous.
Spongy Bone is composed
of small pieces of bone
and lots of open space.
31
Compact
Bone• In long bones,
surrounds
spongy bone at
ends
• Along shaft
surrounding
medullary cavity Spongy Bone
• At ends of long
bones32
Microscopic Anatomy of Spongy Bone
The open spaces keep
bones light
Found in the ends of long
bones
Also fills short bones, flat
bones and some parts of
irregular bones
Contains red marrow
33
Microscopic Anatomy of Compact Bone
Composed of a matrix
of hard mineral salts
reinforced with tough
collagen fibers
Bone cells are called
osteocytes
Osteocytes are found in
tiny cavities within the
matrix called lacunae
34
bone cell35
Gross Anatomy of a Long Bone
Diaphysis
Shaft
Composed of
compact bone
Epiphysis
Ends of the bone
Composed
mostly of spongy
bone
36
Other Features of
Long Bones
• Articular Cartilages:
cover epiphyses for
smooth movement
• Epiphyseal Line:
marking left from
growth at epiphyseal
plate
• Periosteum: fibrous,
connective tissue
that covers the
diaphysis 37
Bone Marrow
Red Marrow – in
cavities of spongy
bone in flat bones
and epiphyses of long
bones, site of
hematopoiesis
Yellow Marrow – fat
storage in medullary
cavity
Red Marrow
Medullary Cavity
Yellow Marrow
Compact Bone
Periosteum
38
Bone Markings Bumps, holes, and ridges
where muscles, tendons,
and ligaments are
attached and where blood
vessels and nerves pass
through
Two categories:
projections or
processes
depressions or cavities
Projections:
Tuberosity
Trochanter
Tubercle
Process
Condyle
Depressions or
Openings:
Meatus
Fossa
Foramen 39
Examples of Bone Markings
Styloid
Process
Olecranon Process
Olecranon Fossa
40
Bone Markings on the Femur
Proximal Posterior
Distal Anterior
41
Joints
Also called articulations
Where two bones meet
Hold bones together, but also give mobility
Three Types:
1. Fibrous – no
movement, ex: skull
2. Cartilaginous – slightly
moveable, ex: pubic
symphysis, vertebrae
3. Synovial – bones
separated by cavity
filled with synovial
fluid, allow the most
movement42
Synovial Joints
Articular
cartilage
Fibrous
articular
capsule
Joint cavity –
contains fluid
Reinforced by
ligaments
43
Types of
Synovial
Joints
44
Ball and Socket Joints
The most
moveable
type of joint
Found in the
shoulder and
hip
45
Physiology of the
Skeletal System
46
Function Overview
Support
Protection
Movement
Hematopoiesis
Storage47
Support
Internal
framework that
supports and
anchors all
soft organs.
48
Protection
Protects soft
body organs
49
Movement
Skeletal muscles
attach to bones by
tendons
Tendons use the
bones as levers to
move body parts
50
Storage
Fat storage in
yellow marrow
The minerals
calcium and
phosphorous are
stored in bone
tissue
51
HematopoiesisBlood cell
formation occurs
in red marrow.
52
Developmental
Aspects
53
Fontanels Spaces between
bones of the skull
in an infant
Commonly called
soft spots
Fully ossified by 2
years
Allows for growth
of the brain and
skull54
Ossification Ossification is the
formation of bone
from cartilage
At birth, bones are
part cartilage and
part bone
The skeleton is fully
ossified by age 2
except for epiphyseal
(growth) plates
55
Longitudinal Growth X-ray of 12 year
old showing
epiphyseal
(growth) plates at
the distal ends of
the tibia & fibula
Epiphyseal plates
are fully ossified by
the end of
adolescence 56
Bone Formation & Growth
Key Terms:
Ossification – bone formation
Epiphyseal plates – provide for
longitudinal growth; increase in length
Appositional growth – increase in
diameter
Osteoblasts – bone-building cells
Osteoclasts – bone-destroying cells
57
Bone Remodeling Breaking down & reforming of bone that occurs
throughout life to maintain proportion & strength as well as healthy calcium levels
58
Osteoporosis• Weakening of the
bone that occurs
with aging
• One in two
women and one
in four men over
age 50 will have
an osteoporosis-
related fracture.
59
Hip Fracture
A hip fracture is
actually a femoral
fracture that occurs
in the proximal end of
the femur near the
hip
The 1-year mortality
rate after a hip
fracture is 20% X-ray following
hip replacement60
Diseases and
Conditions
61
Types of Fractures
62
Arthritis
Osteoarthritis usually
part of aging
Rheumatoid Arthritis
autoimmune disease
Arthritis is an inflammation of the joints.63
Rickets
Lack of vitamin D,
calcium, or
phosphorous
Bones fail to
calcify; stay soft
Usually in children
ages 3-36 months
Rare in developed
countries
64
Herniated Disc Protruding discs of
cartilage between
the vertebrae
Can irritate nearby
nerves and result
in pain, numbness
or weakness in an
arm or leg
65
Scoliosis
Abnormal
curvature of the
spine
May be congenital
or result from
disease or trauma
66
The Skeletal System
67