the skeletal system 5-1. copyright 2008 john wiley & sons, inc. the skeletal system is a dynamic...

The Skeletal SystemThe Skeletal System

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Copyright 2008 John Wiley & Sons, Inc.

The Skeletal System is The Skeletal System is a Dynamic Living Systema Dynamic Living System

The skeletal system provides many The skeletal system provides many essential functions including:essential functions including: Providing supportProviding support Anchoring skeletal musclesAnchoring skeletal muscles Protecting soft tissues and organsProtecting soft tissues and organs Producing blood cells (hematopoiesis)Producing blood cells (hematopoiesis) Storing and releasing minerals Storing and releasing minerals (calcium and phosphorus)(calcium and phosphorus)

Moving with the help of jointsMoving with the help of joints

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The Skeletal System is The Skeletal System is a Dynamic Living Systema Dynamic Living System

Bones look stable and static, but they Bones look stable and static, but they change throughout life.change throughout life. The entire calcium content of your femur is The entire calcium content of your femur is replaced approximately every five to seven replaced approximately every five to seven years.years.

There are 206 named bones in the adult There are 206 named bones in the adult human skeletal system.human skeletal system.

The skeleton is divided into the axial The skeleton is divided into the axial skeleton (the central axis of the body) and skeleton (the central axis of the body) and the appendicular skeleton (the appendages the appendicular skeleton (the appendages and girdles holding them to the central and girdles holding them to the central axis).axis).

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The SkeletonThe Skeleton

Figure 5.2 The skeleton

5-4Copyright 2008 John Wiley & Sons, Inc.


Classification of boneClassification of bone

We classify the bones according to We classify the bones according to shape:shape: Long bones – longer than wideLong bones – longer than wide Short bones – comparable to small Short bones – comparable to small cubescubes

Flat bones – thin in one dimensionFlat bones – thin in one dimension Irregular bones – odd shapedIrregular bones – odd shaped Sesamoid bones – form inside tendonsSesamoid bones – form inside tendons Wormian bones – embedded in the Wormian bones – embedded in the sutures between the main skull bonessutures between the main skull bones

5-5Copyright 2008 John Wiley & Sons, Inc.


Classification of BoneClassification of Bone

Figure 5.3 Classification of bone

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Form follows functionForm follows function

Every bone is designed to perform a Every bone is designed to perform a specific task.specific task. Example: The femur must be strong and Example: The femur must be strong and have a slight curve to bear the weight have a slight curve to bear the weight of the upper torso.of the upper torso.

Bones are composed of compact or Bones are composed of compact or spongy mineralized tissue that is spongy mineralized tissue that is structured for maximum strength and structured for maximum strength and minimum weight.minimum weight.

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Ossification forms bone Ossification forms bone and remodeling continues and remodeling continues

to shape itto shape it Bones are connective tissue produced Bones are connective tissue produced by immature bones cells called by immature bones cells called osteoblasts.osteoblasts.

Where is bone formed in the body?Where is bone formed in the body? Endochondral – within cartilageEndochondral – within cartilage

oror Intramembranous – between membranesIntramembranous – between membranes

Which occurs more often?Which occurs more often? EndochondralEndochondral

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Enochondral OssificationEnochondral Ossification

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Figure 5.4 Endochondralossification


Bone growthBone growth Appositional growth occurs at the Appositional growth occurs at the outer surface of the bone.outer surface of the bone.

The periosteum is the membrane that The periosteum is the membrane that covers the bone.covers the bone. The innermost cellular layer of the The innermost cellular layer of the periosteum differentiates into osteoblasts periosteum differentiates into osteoblasts and begins to add matrix to the exterior.and begins to add matrix to the exterior.

The osteoblasts become trapped in the The osteoblasts become trapped in the matrix and mature into osteocytes, matrix and mature into osteocytes, which creates new bone tissue around which creates new bone tissue around the exterior of the bone.the exterior of the bone.

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Intramembranous Intramembranous ossificationossification

Bone is made within embryonic Bone is made within embryonic connective tissue, surrounded connective tissue, surrounded by developing periosteum.by developing periosteum.

These bones form deep in the These bones form deep in the dermis of the skin and are dermis of the skin and are often called dermal bones.often called dermal bones.

This process forms the flat This process forms the flat bones of the skull, clavicle, bones of the skull, clavicle, and mandible.and mandible.

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Intramembranous Intramembranous ossificationossification

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Figure 5.5 Intramembranous ossification


Bony tissue comes in Bony tissue comes in two forms:two forms:

Compact (dense) or spongy.Compact (dense) or spongy. Compact bone occurs on the Compact bone occurs on the outside of the bone and is outside of the bone and is composed of many individual composed of many individual Haversian systems.Haversian systems.

Spongy bone comprises the inner Spongy bone comprises the inner support and is less organized.support and is less organized. Both forms are held inside the Both forms are held inside the periosteum.periosteum.

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Compact bone Haversian Compact bone Haversian systemssystems

Concentric rings of matrix laid by Concentric rings of matrix laid by osteocytes and formed surrounding a osteocytes and formed surrounding a central canal.central canal.

An osteon is one complete Haversian An osteon is one complete Haversian system.system.

The osteocytes must receive a constant The osteocytes must receive a constant supply of nutrients and dispose of wastes.supply of nutrients and dispose of wastes.

The central cavity of the osteon houses The central cavity of the osteon houses the blood and nerve supply for the bone the blood and nerve supply for the bone tissue.tissue.

Individual cells lie within small holes in Individual cells lie within small holes in the matrix called lacunae.the matrix called lacunae.

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Compact bone Haversian Compact bone Haversian systemssystems

Bone cells communicate with each Bone cells communicate with each other via small canals cut in the other via small canals cut in the matrix called canaliculi.matrix called canaliculi.

These canals allow fluid carrying These canals allow fluid carrying vital nutrients and signaling vital nutrients and signaling chemicals to pass between cells.chemicals to pass between cells.

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Havarsian systemHavarsian system

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Figure 5.6a Haversian system


Spongy boneSpongy bone Spongy bone has trabeculae, or Spongy bone has trabeculae, or struts, that form in response to struts, that form in response to stress.stress.

The struts are composed of The struts are composed of osteocytes surrounded by matrix.osteocytes surrounded by matrix.

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Figure 5.6b Spongy bone


The shaft of the long The shaft of the long bone, or diaphysis, bone, or diaphysis, is composed of dense is composed of dense bone surrounding a bone surrounding a central canal.central canal.

The central canal The central canal houses the marrow.houses the marrow. Red marrow is where Red marrow is where blood cells are blood cells are formed.formed.

Yellow marrow is where Yellow marrow is where energy is stored.energy is stored.

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Figure 5.7 Long bone with parts identified


The ends of the bones, or The ends of the bones, or epiphyses, include the epiphyses, include the epiphyseal plate.epiphyseal plate. This is an area of cartilage This is an area of cartilage where long bones continue to where long bones continue to grow during childhood and grow during childhood and adolescence.adolescence.

When bones cease growing, When bones cease growing, the cartilage is replaced by the cartilage is replaced by bone, leaving the epiphyseal bone, leaving the epiphyseal line.line.

Articulating cartilage is a Articulating cartilage is a layer of hyaline cartilage layer of hyaline cartilage found between two bones to found between two bones to prevent bones from grinding prevent bones from grinding at the joints.at the joints.

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Figure 5.7 Long bone with parts identified


The Axial Skeleton is the The Axial Skeleton is the Center of ThingsCenter of Things

The axial skeleton includes the 8 The axial skeleton includes the 8 cranial and 14 facial bones, the hyoid, cranial and 14 facial bones, the hyoid, ribs and vertebra.ribs and vertebra.

The 8 cranial bones surround and The 8 cranial bones surround and protect the brain.protect the brain.

How are the 8 cranial bones held How are the 8 cranial bones held together?together? by fixed joints called suturesby fixed joints called sutures

To articulate means to join. What is To articulate means to join. What is an articulation?an articulation? a joint holding two bones togethera joint holding two bones together

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8 cranial bones8 cranial bones 1 Frontal bone1 Frontal bone 2 Parietal bones2 Parietal bones 2 Temporal bones2 Temporal bones 1 Occipital bone1 Occipital bone 1 Ethmoid bone1 Ethmoid bone 1 Sphenoid bone1 Sphenoid bone

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Figure 5.8 Skull


14 facial bones support 14 facial bones support the distinctive facial the distinctive facial features of humans.features of humans.

2 Maxillae bones2 Maxillae bones 2 Palatine bones2 Palatine bones 2 Nasal bones2 Nasal bones 2 Lacrimal bones2 Lacrimal bones 2 Zygomatic bones2 Zygomatic bones 2 Inferior nasal conchae2 Inferior nasal conchae 1 Mandible1 Mandible 1 Vomer1 Vomer

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Copyright 2008 John Wiley & Sons, Inc. 5-28

Figure 5.9 Facial bones


The bony orbital complex of the The bony orbital complex of the eye is composed of seven bones eye is composed of seven bones (three cranial and four facial). (three cranial and four facial). This provides the support for the This provides the support for the eye.eye.

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Figure 5.11 Orbital complex


The nasal complex includes The nasal complex includes bones that encase the nasal bones that encase the nasal cavities and the paranasal cavities and the paranasal sinuses. sinuses.

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Figure 5.12 Nasal complex


Hyoid, ribs and Hyoid, ribs and vertebraevertebrae

The hyoid bone, The hyoid bone, which lies below which lies below the tongue, is the the tongue, is the only bone in the only bone in the skeleton that is skeleton that is not attached to not attached to another bony another bony structure.structure.

The vertebrae, ribs The vertebrae, ribs and sternum allow and sternum allow upright posture and upright posture and protect vital protect vital organs of the organs of the thoracic cavity.thoracic cavity.

Figure 5.14 Thoracic cage

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Vertebral columnVertebral column

24 vertebrae24 vertebrae 1 sacrum1 sacrum 3-5 coccyx bones3-5 coccyx bones

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Figure 5.13 Vertebrae


Vertebral columnVertebral column A typical vertebra consists of A typical vertebra consists of 3 parts:3 parts: Vertebral bodyVertebral body Vertebral archVertebral arch Vertebral articularVertebral articular processesprocesses

5-33Figure 5.13 Vertebrae


Your limbs comprise your Your limbs comprise your Appendicular SkeletonAppendicular Skeleton

The appendicular The appendicular skeleton includes all skeleton includes all bones that are attached bones that are attached to the axial skeleton.to the axial skeleton. Pectoral girdlePectoral girdle

shoulder bonesshoulder bones Upper appendagesUpper appendages

arms and handsarms and hands Pelvic girdlePelvic girdle Lower appendagesLower appendages

legs and feetlegs and feet

5-34Figure 5.15 Appendicular skeleton


Pectoral girdlePectoral girdle

ClavicleClavicle

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Figure 5.16 The clavicle


Pectoral girdlePectoral girdle

ScapulaeScapulae

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Figure 5.17 The scapulae


Upper AppendagesUpper Appendages

HumerusHumerus

CarpalsCarpals 2 rows of 4 short bones2 rows of 4 short bones

Scaphoid boneScaphoid bone Lunate boneLunate bone TriquetrumTriquetrum Pisiform bonePisiform bone

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Figure 5.18 The humerus and carpals

Trapezium Trapezoid bone Capitate bone Hamate bone


Upper AppendagesUpper Appendages

MetacarpalsMetacarpals

PhalangesPhalanges

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Figure 5.19 The metacarpels and phalanges


Pelvic girdlePelvic girdle Os coxa (hip bone)Os coxa (hip bone)

The sacrum and coccyxThe sacrum and coccyx Emerges from 3 bones that fuse in Emerges from 3 bones that fuse in early puberty:early puberty: Ilium, ischium, and pubic boneIlium, ischium, and pubic bone

Male and female hip bones are Male and female hip bones are visibly different:visibly different: Female - shallower, broader, enlarged Female - shallower, broader, enlarged pelvic outlet, wider pelvic inlet and pelvic outlet, wider pelvic inlet and broader pubic angle.broader pubic angle.

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Pelvic girdlePelvic girdle

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Figure 5.20 Pelvis


Lower AppendagesLower Appendages

FemurFemur

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Figure 5.22 Femur


Lower AppendagesLower Appendages Patella (knee cap)Patella (knee cap)

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Figure 5.24 Patella


Lower AppendagesLower Appendages TibiaTibia FibulaFibula

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Figure 5.25 The fibulaFigure 5.26 The tibia



AnkleAnkle 7 tarsal bones7 tarsal bones

Calcaneous (heel Calcaneous (heel bone)bone)

TalusTalus Navicular Navicular CuboidCuboid Lateral Lateral cuneiformcuneiform

Intermediate Intermediate cuneiformcuneiform

Medial cuneiformMedial cuneiform

5-44Figure 5.27 The ankle—superior



AnkleAnkle 7 tarsal bones7 tarsal bones

Calcaneous (heel Calcaneous (heel bone)bone)

TalusTalus Navicular Navicular CuboidCuboid Lateral cuneiformLateral cuneiform Intermediate Intermediate cuneiformcuneiform

Medial cuneiformMedial cuneiform

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Figure 5.28 The ankle—inferior


Lower AppendagesLower Appendages FootFoot

Metatarsal bonesMetatarsal bones PhalangesPhalanges

5-46Figure 5.29 Arches of the foot

The arches of The arches of the foot are the foot are maintained by maintained by ligaments and ligaments and tendons.tendons.


Joints Link the Skeletal Joints Link the Skeletal System TogetherSystem Together

Joints occur wherever two bones Joints occur wherever two bones meet.meet.

Joints can be classified by Joints can be classified by function or structure.function or structure.

Functionally:Functionally: Synarthrotic – immovableSynarthrotic – immovable Amphiarthrotic – semimovable Amphiarthrotic – semimovable Diarthrotic – freely movableDiarthrotic – freely movable

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Synarthrotic JointsSynarthrotic Joints Bones are fused together, so Bones are fused together, so movement is impossible.movement is impossible.

Examples:Examples: Fibrous connections Fibrous connections

holding teeth in jawsholding teeth in jaws Coronal sutureCoronal suture Sagittal sutureSagittal suture Lamboidal sutureLamboidal suture Squamous sutureSquamous suture

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Figure 5.30 Synarthrotic joint


Bones are fused together, so Bones are fused together, so movement is impossible.movement is impossible.

Examples:Examples: Fibrous connections Fibrous connections

holding teeth in jawsholding teeth in jaws Coronal sutureCoronal suture Sagittal sutureSagittal suture Lamboidal sutureLamboidal suture Squamous sutureSquamous suture

Synarthrotic JointsSynarthrotic Joints

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Figure 5.30 Synarthrotic joint


Amphiarthrotic JointsAmphiarthrotic Joints Some movement is Some movement is possible.possible.

Examples:Examples: Between adjacent Between adjacent vertebraevertebrae

Between the Between the tibia and fibula tibia and fibula (connected by (connected by tight ligaments)tight ligaments)

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Figure 5.31 Amphiarthrotic joint


Diarthrotic or Synovial Diarthrotic or Synovial JointsJoints Allow free movement Allow free movement

between two bones. between two bones. These are the most These are the most common joints in common joints in the body.the body.

Supporting Supporting structures:structures: TendonsTendons LigamentsLigaments Bursae Bursae MenisciMenisci

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Figure 5.32 Typical Synovial joint


SummarySummary

The skeletal system is composed of the The skeletal system is composed of the axial and appendicular skeleton.axial and appendicular skeleton.

The adult skeleton contains 206 bones.The adult skeleton contains 206 bones. The skeletal system provides support, The skeletal system provides support, protection, allows movement and stores protection, allows movement and stores calcium.calcium.

The skeleton, together with all of its The skeleton, together with all of its sophisticated joints, provides a sophisticated joints, provides a framework for movement, but it does not framework for movement, but it does not guarantee movement on its own.guarantee movement on its own.

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the skeletal system 5-1. copyright 2008 john wiley & sons, inc. the skeletal system is a dynamic...

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