Ch. 5

Parts of the skeletal system
◦
◦
◦
◦
Bones
Joints
Cartilages
Ligaments





Support
Protection
Movement
Storage
Blood cell formation


The adult skeleton has 206 bones
Two basic types of bone tissue:
◦ Compact bone
 Homogeneous
◦ Spongy bone
 Small needle-like
pieces of bone
 Many open spaces
Figure 5.2b
Figure 5.1

Long bones
◦
◦
◦
◦
Typically longer than they are wide
Have a shaft with heads at both ends
Contain mostly compact bone
Example:
 Femur
 Humerus
Figure 5.1a

Short bones
◦ Generally cube-shape
◦ Contain mostly spongy bone
◦ Example:
 Carpals
 Tarsals
Figure 5.1b

Flat bones
◦ Thin, flattened, and usually curved
◦ Two thin layers of compact bone surround a layer
of spongy bone
◦ Example:
 Skull
 Ribs
 Sternum
Figure 5.1c

Irregular bones
◦ Irregular shape
◦ Do not fit into other bone classification categories
◦ Example:
 Vertebrae
 Hip bones
Figure 5.1d

Diaphysis
◦ Shaft composed of compact
bone
◦ Medullary cavity stores fat

Epiphyses
◦ Ends composed mostly of
spongy bone
◦ Red marrow produces blood
cells
◦ Hyaline cartilage covering
reduces friction

Epiphyseal (growth)
plate
◦ Flat plate of hyaline cartilage
in young, growing bone

Epiphyseal line
◦ Remnant of the epiphyseal
plate seen in adult bones

Periosteum
◦ Outside covering of the
diaphysis
◦ Fibrous connective tissue
membrane

Sharpey’s fibers
◦ Connective tissue securing
periosteum to underlying
bone

Arteries
◦ Supply bone cells with
nutrients

Osteon (Haversian system)
◦ A unit of bone containing central canal and matrix rings

Central (Haversian) canal
◦ Opening in the center of an osteon
◦ Carries blood vessels and nerves

Lacunae
◦ Cavities containing bone cells (osteocytes)
◦ Arranged in concentric rings

Canaliculi
◦ Tiny canals that radiate from the central canal to lacunae
◦ Form a transport system connecting all bone cells to a nutrient
supply
Figure 5.3b–c




In embryos, the skeleton is primarily hyaline
cartilage
During development much of this cartilage is
replaced by bone (ossification)
Red marrow in the medullary cavity of long
bones is replaced with yellow marrow (fat).
Cartilage remains in isolated areas
◦ Bridge of the nose
◦ Parts of ribs
◦ Joints


Epiphyseal (growth) plates allow for
lengthwise growth of long bones during
childhood
Bone remodeling and sculpting continues
throughout life
Articular
cartilage
Hyaline
cartilage
Spongy
bone
New center of
bone growth
New bone
forming
Epiphyseal
plate
cartilage
Growth
in bone
width
Medullary
cavity
Bone starting
to replace
cartilage
Growth
in bone
length
Blood
vessels
New bone
forming
Bone collar
Epiphyseal
plate cartilage
Hyaline
cartilage
model
In an embryo
(a)
In a fetus
In a child
Figure 5.4a



Osteocytes—mature bone cells
Osteoblasts—bone-forming cells
Osteoclasts—bone-destroying cells


Fracture—break in a bone
Types of bone fractures
◦ Closed (simple) fracture—break that does not
penetrate the skin
◦ Open (compound) fracture—broken bone
penetrates through the skin

Bone fractures are treated by reduction
(realignment)and immobilization
Table 5.2
1.
2.
3.
4.
Hematoma (blood-filled swelling) is formed
Break is splinted by fibrocartilage callus
Fibrocartilage callus is replaced by a bony
callus
Bony callus is remodeled to form a
permanent patch
Hematoma
Internal
callus
(fibrous
tissue and
cartilage)
External
callus
Bony
callus of
spongy
bone
New
blood
vessels
Healed
fracture
Spongy
bone
trabecula
Hematoma
formation
Fibrocartilage
callus formation
Bony callus
formation
Bone remodeling
Figure 5.5

Two subdivisions:
◦ Axial skeleton – skull, thoracic cage & vertebral
column
◦ Appendicular skeleton – limbs, pectoral & pelvic
girdle
Figure 5.6a
Figure 5.6b


Forms the longitudinal axis of the body
Divided into three parts
◦ Skull
◦ Vertebral column
◦ Bony thorax

Two sets of bones
◦ Cranium
◦ Facial bones


Bones are joined by sutures (immovable
joints)
Only the mandible (jaw) is attached by a
freely movable joint
Figure 5.7
Figure 5.11



The only bone that does not articulate with
another bone
Serves as a moveable base for the tongue
Aids in swallowing and speech
Figure 5.12


The fetal skull is large compared to the
infant’s total body length
Fontanels—fibrous membranes connecting
the cranial bones
◦ Allow the brain to grow
◦ Convert to bone within 24 months after birth
Figure 5.13a
Figure 5.13b

Each vertebrae is given a name according to
its location
◦ There are 24 single vertebral bones separated by
intervertebral discs
 Seven cervical vertebrae are in the neck
 Twelve thoracic vertebrae are in the chest region
 Five lumbar vertebrae are associated with the lower
back

Nine vertebrae fuse to form two composite
bones
◦ Sacrum
◦ Coccyx
Figure 5.14

The spine is curved
◦ Primary curvatures are in the thoracic and sacral
regions
 Present from birth (“C” shape)
◦ Secondary curvatures are in the cervical and lumbar
regions
 Develop after birth (“S” shape)

Spinal curvature allows for the absorption of
shock when moving
Figure 5.15
Figure 5.16

Sacrum
◦ Formed by the fusion of five vertebrae

Coccyx
◦ Formed from the fusion of three to five vertebrae
◦ “Tailbone,” or remnant of a tail that other
vertebrates have
Figure 5.19


Forms a cage to protect heart and lungs
Consists of three parts
◦ Sternum (breast bone)
◦ Ribs
 True ribs (pairs 1–7) – attached to sternum
 False ribs (pairs 8–12) – attached to other ribs
 Floating ribs (pairs 11–12) – only attached at vertebrae
◦ Thoracic vertebrae
Figure 5.20a

Composed of 126 bones
◦ Limbs (appendages)
◦ Pectoral girdle
◦ Pelvic girdle

Composed of two bones
◦ Clavicle —collarbone
◦ Scapula —shoulder blade

These bones allow the upper limb to have
exceptionally free movement
Figure 5.21a
Figure 5.21b
Figure 5.21c–d

The upper arm has one bone
◦ Humerus (a.k.a.funny bone)
Figure 5.22a–b

The forearm has two bones
◦ Ulna
 Medial bone in anatomical position
◦ Radius
 Lateral bone in anatomical position
Figure 5.22c

The hand
◦ Carpals —wrist
◦ Metacarpals —palm
◦ Phalanges —fingers
Figure 5.23

Formed by two coxal (hip) bones
◦ Each is composed of three pairs of fused bones:
 Ilium
 Ischium
 Pubis
Figure 5.24a


The total weight of the upper body rests on
the pelvis
It protects several organs
◦ Reproductive organs
◦ Urinary bladder
◦ Part of the large intestine
Figure 5.24c

The thigh has one bone
◦ Femur
 The heaviest, strongest bone in the body
 Makes a good cave-man club
Figure 5.25a–b

The lower leg has two bones
◦ Tibia
 Shinbone
 Larger and medially oriented
◦ Fibula
 Thin and sticklike
 Bears no weight – for muscle attachment only
Figure 5.25c

The foot
◦ Tarsals - ankle
◦ Metatarsals—sole
◦ Phalanges—toes
Figure 5.26

Bones of the foot are arranged to form three
strong arches
◦ Two longitudinal
◦ One transverse

Arches provide shock absorption
Figure 5.27

Ligaments hold bones together at joints
◦ Allow for mobility

Joints are classified functionally or
structurally

Synarthroses
◦ Immovable joints

Amphiarthroses
◦ Slightly moveable joints

Diarthroses
◦ Freely moveable joints

Fibrous joints
◦ Generally immovable

Cartilaginous joints
◦ Immovable or slightly moveable

Synovial joints
◦ Freely moveable
[Insert Table 5.3 here]
Table 5.3


Bones united by fibrous tissue
Example:
◦ Sutures (cranium)
◦ Syndesmoses
 Allows more movement than sutures
 Example: Distal end of tibia and fibula
Figure 5.28a–b


Bones connected by cartilage
Example:
◦ Pubic symphysis
◦ Intervertebral joints
Figure 5.28c–e





Articulating bones separated by a joint cavity
(formed by a synovial membrane)
Articular cartilage (hyaline cartilage) covers
the ends of bones
A fibrous articular capsule encloses joint
surfaces
A joint cavity is filled with synovial fluid
Ligaments reinforce the joint
Figure 5.28f–h

Bursae
◦
◦
◦
◦

Flattened fibrous sacs
Lined with synovial membranes
Filled with synovial fluid
Not actually part of the joint
Tendon sheath
◦ Elongated bursa that wraps around a tendon
Figure 5.29
Figure 5.30a–c
Figure 5.30d–f

Bursitis
◦ inflammation of a bursa usually caused by a blow or
friction

Tendonitis
◦ inflammation of tendon sheaths

Arthritis
◦ inflammatory or degenerative diseases of joints
◦ Over 100 different types
◦ The most widespread crippling disease in the
United States
bursitis
tendonitis

Osteoarthritis
◦ Most common chronic arthritis
◦ Probably related to normal aging processes

Rheumatoid arthritis
◦ An autoimmune disease—the immune system
attacks the joints
◦ Symptoms begin with bilateral inflammation of
certain joints
◦ Often leads to deformities

Gouty arthritis
◦ Inflammation of joints is caused by a deposition of
uric acid crystals from the blood
◦ Can usually be controlled with diet
Rheumatoid
arthritis
Gouty arthritis

Osteoporosis
◦ Bone-thinning disease afflicting
 50% of women over age 65
 20% of men over age 70
◦ Disease makes bones fragile and bones can easily
fracture
◦ Vertebral collapse results in kyphosis (also known
as dowager’s hump)
◦ Estrogen aids in health and normal density of a
female skeleton
normal
osteoporotic
Figure 5.34