Chapter 11
Skeletal System
Points to Ponder
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What are the 5 functions of the skeletal system?
What are the parts of a long bone?
How do bones grow, remodel and repair?
How are hormones involved in bone growth?
What is osteoporosis?
How are age, gender and ethnicity determined
through skeletal remains?
• What are the components of the axial and
appendicular skeletons?
• What are synovial joints and what kind of
angular movements to they allow?
11.1 Overview of the skeletal system
What are the functions of the skeletal
system?
1.
2.
3.
4.
Supports the body
Protects the soft body parts
Produces blood cells
Stores minerals (calcium and phosphate)
and fat
5. Allows for movement by attaching
muscles
11.1 Overview of the skeletal system
What is the anatomy of a long bone?
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Diaphysis – shaft of the bone made of
compact bone and filled with yellow
marrow
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Epiphysis – ends of the bone made
mostly of spongy bone
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Articular cartilage – hyaline cartilage
found on the ends of long bones
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Yellow bone marrow – stores fat
Red bone marrow – makes blood cells
found in spongy bone and flat bones
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Periosteum – living, outer covering of
fibrous connective tissue
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Ligaments – fibrous connective tissue
that connects bones
11.1 Overview of the skeletal system
More detail on bone…
• Compact bone
– Composed of osteons with
a central canal containing
blood vessels
– Contains living bone cells
called osteocytes
chambers called lacunae
• Spongy bone
– Made of plates with spaces
filled with red bone marrow
11.1 Overview of the skeletal system
Where are the 3 types of cartilage found?
• Cartilage – flexible connective tissue
categorized based on the type and arrangement
of matrix fibers
• Types:
– Hyaline cartilage – ends of long bones, nose, ends of
ribs, larynx and trachea
– Fibrocartilage – disks between vertebrae and in the
knee; stronger than hyaline cartilage
– Elastic cartilage – ear flaps and epiglottis; more
flexible than hyaline cartilage
11.2 Bone growth, remodeling and repair
What are the important cells in bone growth,
remodeling and repair?
• Osteoblasts – bone-forming cells
• Osteocytes – mature bone cells that maintain
bone structure derived from osteoblasts
• Osteoclasts – bone-absorbing cells
• Chondroytes – cartilage-forming cells
11.2 Bone growth, remodeling and repair
How does bone develop?
Ossification - the formation of bone in two
distinct ways:
1. Intramembranous ossification - bone
development between sheets of fibrous
connective tissue; used in flat bones
2. Endochondrial ossification – cartilage is
replaced by bone; used by most bones
11.2 Bone growth, remodeling and repair
How does endochondral ossification occur?
1st Cartilage model – chondrocytes lay down hyaline cartilage in the
shape of the future bones
2nd Bone collar formation – osteoblasts secrete bone matrix and results
in a collar made of compact bone
3rd Primary ossification center – osteoblasts are brought interiorly by
blood and lay down spongy bone
4th Secondary ossification sites – bone centers in the epiphyses formed
after birth
5th Epiphyseal plate – a cartilage band that acts as a growth plate that
allows bones to lengthen
11.2 Bone growth, remodeling and repair
Visualizing endochondral ossification
11.2 Bone growth, remodeling and repair
How do bones lengthen?
11.2 Bone growth, remodeling and repair
How do hormones affect bone growth?
• Growth hormone (GH) – stimulates
general bone growth and the epiphyseal
plates
• Sex hormones – increases growth during
adolescence
• Vitamin D – converted to a hormone to
allow calcium absorption in the intestine
11.2 Bone growth, remodeling and repair
What is bone remodeling and what is its
role in homeostasis?
• Bone remodeling – bone renewal at a rate of up
to 18% per year
• Remodeling allows bones to respond to stress
• Regulates the calcium in the blood through
hormones:
– Parathyroid hormone (PTH) – increases blood
calcium by accelerating bone recycling
– Calcitonin – decreases blood calcium
11.2 Bone growth, remodeling and repair
Health focus: Osteoporosis
• Osteoporosis – bones are weakened due to a decreased
bone mass
• Bone reabsorption exceeds absorption usually by age 40
• Risk factors: women, white or Asian, thin, family history,
early menopause, smoking, diet low in calcium,
excessive caffeine or alcohol consumption and a
sedentary lifestyle
• Can lead to fractures and other complications
• Can be treated with drugs, hormones and lifestyle
change
11.2 Bone growth, remodeling and repair
Steps in bone repair
• Hematoma (6-8 hrs.) – blood clot formed between
broken bones
• Fibrocartilaginous callus (~ 3 weeks) – cartilaginous
callus forms between broken bones
• Bony callus (3-4 months) – cartilaginous callus is turned
to bone
• Remodeling – old bone tissue is replaced by new bone
tissue
11.2 Bone growth, remodeling and repair
Bone repair
11.3 Bones of the axial skeleton
The 206 bones of the skeleton
11.3 Bones of the axial skeleton
Science focus: Skeletal remains
Characteristics to be determined:
1. Age: approximated through dentition,
studying areas of bone ossification and joint
condition
2. Gender: pelvic bone is best used, thickness
of long bones, skull characteristics
3. Ethnicity: difficult to tell but skull
characteristics are most useful
11.3 Bones of the axial skeleton
The axial skeleton
• Skull – made of cranium and facial bones
• Hyoid bone
• Vertebral column – vertebrae and
intervertebral disks
• Rib cage – ribs and sternum
11.3 Bones of the axial skeleton
The skull – the cranium
• Cranium
– Protects the brain
– Composed of 8 bones
– Some contain sinuses
11.3 Bones of the axial skeleton
Bones of the face and the hyoid bone
• Facial bones
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Mandible
Maxillae
Zygomatic bones
Nasal bones
• Hyoid
– Only bone that does
not articulate with
another bone
11.3 Bones of the axial skeleton
The vertebral column
• Types of vertebrae
– 33 vertebrae
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Cervical (7)
Thoracic (12)
Lumbar (5)
Sacrum (5 fused)
Coccyx (4 fused into
tailbone)
• Intervertebral disks
– Fibrocartilage between
vertebrae
11.3 Bones of the axial skeleton
The rib cage
• Ribs – protects heart and
lungs
– Flattened bone originating
from the thoracic vertebrae
– 12 pairs:
• 7 pr. true ribs
• 3 pr. false ribs
• 2 pr. floating ribs
• Sternum
– Known as the breastbone
11.4 Bones of the appendicular skeleton
The appendicular skeleton
• Pectoral girdle and upper limb
• Pelvic girdle and lower limb
11.4 Bones of the appendicular skeleton
The appendicular skeleton
• Pectoral girdle
– Scapula and clavicle
• Upper limb
– Arm and hand bones
11.4 Bones of the appendicular skeleton
The appendicular skeleton
• Pelvic girdle
– coxal bone
• Lower limb
– Leg and foot bones
11.5 Articulations
Types of joints
(where bones meet bones)
• Fibrous – usually immovable such as the
sutures between cranial bones
• Cartilaginous – tend to be slightly movable
such as the intervertebral disks
• Synovial – freely movable joints such as
the ball-and-socket hip and shoulder joints
and the knee joint
11.5 Articulations
Anatomy of a synovial joint
11.5 Articulations
Summary of synovial joints movements
• Flexion – decrease in joint angle
• Extension - increase in joint angle
• Adduction – body part moves toward midline
• Abduction – body part moves away from midline
• Inversion – sole of foot turns inward
• Eversion – sole of foot turns outward
11.5 Articulations
Visualizing synovial joints movements