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Chapter 7
Skeletal System
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Introduction
A. Bones are very active tissues.
B. Each bone is made up of several types of tissues and so is an organ.
C. Bone functions include: - muscle attachment
- protection and support
- blood cell production
- storage of minerals
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Bone Structure
A.Bones differ in size and shape, yet are similar in several ways.
B.Parts of a Long Bone – 1. Epiphyses– 2. Articular cartilages – 3. Diaphysis– 4. Periosteum– 5. Compact Bone– 6. Spongy Bone– 7. Endosteum (Marrow)
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Epiphyses - Expanded ends of bones that form joints with adjacent bones
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Epiphyses - Expanded ends of bones that form joints with adjacent bones
Articular cartilage - (hyaline cartilage) cover the epiphyses.
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Epiphyses - Expanded ends of bones that form joints with adjacent bones
Articular cartilage - (hyaline cartilage) cover the epiphyses.
Diaphysis - shaft of the bone
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Epiphyses - Expanded ends of bones that form joints with adjacent bones
Articular cartilage - (hyaline cartilage) cover the epiphyses.
Diaphysis - shaft of the bone
Periosteum - tough layer of vascular connective tissue that covers the bone
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Epiphyses - Expanded ends of bones that form joints with adjacent bones
Articular cartilage - (hyaline cartilage) cover the epiphyses.
Diaphysis - shaft of the bone
Periosteum - tough layer of vascular connective tissue that covers the bone
Spongy Bone – fills the epiphyses, porous to reduce the weight of the skeleton.
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Epiphyses - Expanded ends of bones that form joints with adjacent bones
Articular cartilage - (hyaline cartilage) cover the epiphyses.
Diaphysis - shaft of the bone
Periosteum - tough layer of vascular connective tissue that covers the bone
Spongy Bone – fills the epiphyses, porous to reduce the weight of the skeleton.
Compact bone - makes up the wall of the diaphysis
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C. Classification of Bones– Bones are classified according to following
shapes:• Long• Short• Flat• Irregular• Sesamoid
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Bone Structure
Microscopic Cross-Section of Bone
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Bone StructureD. Microscopic Structure
1. Bone cells (osteocytes) are located within lacunae that lie in concentric circles around osteonic (central) canals.
The bone cells can function
because of the
canaliculi! They supply
what the cell needs!
Bone Structure
2. Osteocytes pass nutrients and gasses in the matrix
through canaliculi.
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The arrangement of bone cells effect the type of bone.
Cemented bone cells create compact bone
- the organization of these cells create a
“central canal” where nerve and blood vessels pass through
Spongy bone lacks this organization
central canal
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Bone Development and Growth
Bone Growth
• Ossification – the formation of bone
• This process uses specialized cells. – Osteocytes – living bone cells– Osteoblasts – bone builders – create osteocyte– Osteoclasts – bone breakers – destroy osteocyte
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Babies are born with over 300 bones. At adulthood, the number of bones in the body
in 206 (teeth depending).
In the fetal skeleton – bones fuse together as growth
occurs.
Bone Development & Growth
A. Bones form by replacing connective tissues in the fetus.
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Bone Development & Growth
B. Some bones form within sheetlike layers of connective tissue (intramembranous bones), while others replace masses of cartilage (endochondral bones).
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All of this happens under a
membrane –
Hence “intra” “membranous”
Bone Development & Growth
C. Intramembranous Bones 1. The flat bones of the skull form as intramembranous bones that develop from layers of connective tissue.
2. Osteoblasts deposit bony tissue around themselves.
24Osteoblast (before) Osteocyte (after)
Bone Development & Growth
3. Once osteoblasts deposit bone are located in lacunae, they are called osteocytes.
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Bone Development & Growth
D. Endochondral Bones 1. Most of the bones of the skeleton fall into this category.
2. They first develop as hyaline cartilage models and are
then replaced with bone.
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NOTE: Cartilage does not contain
blood vessels
Bone Development & Growth
3. Cartilage is broken down in the diaphysis and progressively replaced with bone while the periosteum develops on the outside.
4. Cartilage tissue is invaded by blood vessels and osteoblasts.
but where does the cartilage go?
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Bone Development & Growth
5. Osteoclasts break down the cartilage and are replaced with bone building osteoblasts that deposit bone in it’s place.
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Bone Development & Growth
6. Epiphyseal plates are responsible for lengthening bones while increases in thickness are due to ossification underneath the periosteum.
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• Bones can also be manipulated in their growth – they can be enlongated, thinned, or thickened.
The Taboo of Bones
The Taboo of Bones
• Because of the bone cells, when a bone breaks, it heals back stronger.
Bone Function and Organization
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A. Support and Protection
1. Bones give shape to the head, thorax, and limbs.
2. Bones such as the pelvis and lower limbs provide support for the body.
3. Bones of the skull protect the brain, ears, and eyes.
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B. Bone Movement
1. Bones can act as levers.
a. A lever has four components:
- a rigid bar,
- a pivot or fulcrum,
- an object that is moved against resistance
- a force that supplies energy.
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C. Blood Cell Formation
1. Blood cells are manufactured in bone marrow.
2. Two kinds of marrow occupy the medullary cavities of bone.
C. Blood Cell Formation
a. Red marrow functions in the formation of red blood cells, white blood cells, and platelets, and is found in the spongy bone of the skull, ribs, sternum, clavicles, vertebrae, and pelvis.
C. Blood Cell Formation
b. Yellow marrow, occupying the cavities of most bones, stores fat.
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D. Storage of Inorganic Salts
1. The inorganic matrix of bone stores inorganic mineral salts in the form of calcium phosphate that is important in many metabolic processes.
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D. Storage of Inorganic Salts2. Calcium in bone is a reservoir for body calcium; when blood levels are low, osteoclasts release calcium from bone.
3. Calcium is stored in bone under the influence of calcitonin when blood levels of calcium are high.
Mr. T says “DRINK YOUR MILK”
fool.
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D. Storage of Inorganic Salts
4. Bone also stores magnesium, sodium, potassium, and carbonate ions.
5. Bones can also accumulate harmful elements, such as lead, radium, and strontium.
Skeletal Organization
A. The axial skeleton consists of the:- skull
- hyoid bone
- vertebral column (vertebrae and intervertebral disks)
- thorax (ribs and sternum)
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Skull
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Hyoid Bone
Vertrebral Column
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Sternum and Ribs (Thorax)
Skeletal Organization
B. The appendicular skeleton consists of the: - pectoral girdle (scapulae and clavicles)
- upper limbs (humerus, radius, ulna, carpals, metacarpals, and phalanges)
- pelvic girdle (coxal bones articulating with the sacrum)
- lower limbs (femur, tibia, fibula, patella, tarsals, metatarsals, phalanges)
Pectoral Gircle
Upper Limb
Pelvic Girdle
Lower Limb
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The Skull
The body’s natural helmet.
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A Closer Look At….
• The Maxilla
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A Closer Look At….
• The Nasal Bone
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A Closer Look At….
• The Zygomatic Bone
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A Closer Look At….
• The Sphenoid Bone
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A Closer Look At….
• The Frontal Bone
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A Closer Look At….
• The Temporal Bone
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A Closer Look At….
• The Parietal Bone
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A Closer Look At….
• The Occipital Bone
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The Joints of the Skeletal System
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Joints
1. Joints (articulations) are the functional junctions between bones.
2. Joints enable a wide variety of body movements.
3. Joints can be classified according to the degree of movement possible and can be immovable, slightly movable, or freely movable.
Fibrous and Cartilaginous Joints
4. Joints can also classified according to the type of tissue that binds them together.
A. Fibrous Joints - held close together by dense connective tissue and are
immovable
B. Cartilaginous Joints - help absorb shock and are slightly movable.
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Synovial Joints
C. Synovial Joints
1. Most joints of the skeleton are synovial joints.
2. The ends of bone in a synovial joint are covered with hyaline cartilage.
Synovial Joints
3. A joint capsule consists of an outer layer of dense connective tissue that joins the periosteum, and an inner layer made up of synovial membrane.
a. Synovial fluid has the consistency of egg whites and lubricates articulating
surfaces within the joint.
Synovial Joints
4. Some synovial joints contain shock-absorbing pads of fibrocartilage called menisci.
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Types of Synovial Joints
Type Of Joint
What It Looks Like
How It Moves
Where It Is
Ball and Socket
Circular motion, wide rage
Hip and Shoulder
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Types of Synovial Joints
Type Of Joint
What It Looks Like
How It Moves
Where It Is
Condyloid Single plane, wide rage
Metacarpal and Phalenge
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Types of Synovial Joints
Type Of Joint
What It Looks Like
How It Moves
Where It Is
Gliding Joint
Rotate and twist – wide range
Wrist, ankle, vertebrae
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Types of Synovial Joints
Type Of Joint
What It Looks Like
How It Moves
Where It Is
Saddle Wide range metacarpal
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Types of Synovial Joints
Type Of Joint
What It Looks Like
How It Moves
Where It Is
Hinge Back and forth, one plane, like a door hinge
Knee and elbow joints
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Types of Synovial Joints
Type Of Joint
What It Looks Like
How It Moves
Where It Is
Pivot Rotation Head and Neck
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Types of Joint Movements
1. When a muscle contracts, its fibers pull its movable end (insertion) toward its stationary end (origin), causing movement at a joint.
Types of Joint Movement
• These terms describe movements that occur at joints: – flexion, extension, hyperextension
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Types of Joint Movement
• These terms describe movements that occur at joints: – dorsiflexion, plantar flexion
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Types of Joint Movement
• These terms describe movements that occur at joints: – abduction, adduction
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Types of Joint Movement
• These terms describe movements that occur at joints: – rotation, circumduction
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Types of Joint Movement
• These terms describe movements that occur at joints: – pronation, supination
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Types of Joint Movement
• These terms describe movements that occur at joints: – eversion, inversion
Types of Joint Movement
• These terms describe movements that occur at joints: – retraction, protraction
Types of Joint Movement
• These terms describe movements that occur at joints: – elevation, depression
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