The Skeletal System

The Skeletal System 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Skeleton: Overview o

Functions of the Skeleton • • • • •

o o o

Support Protection Blood cell production Storage Movement

Anatomy of a Long Bone Bone Growth and Repair Surface Features of Bones 2

Skeleton: Overview o Classification • Long – longer than they are wide • Short – cube shaped • Flat – plate-like, with broad surfaces • Irregular – varied shapes • Round – circular in shape

Fig 6.1

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Skeleton: Overview o

Anatomy of a Long Bone

• Periosteum – tough, connective tissue covering • Epiphysis – expanded portion at the ends of bones • Diaphysis – portion between the epiphyses • Medullary cavity – hollow portion of diaphysis containing yellow marrow • Articular cartilage – layer of hyaline cartilage where bones join together • Endosteum – lines the medullary cavity and the spaces of spongy bone

Fig 6.2a

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Skeleton: Overview •

Compact Bone  

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•

Lacunae – contain bone cells (osteocytes) Lamellae – concentric layers of matrix containing collagen fibers and mineral salts Blood vessels and nerves enter the central canal

Spongy Bone  

Contains bony bars and plates called trabeculae Trabeculae follow lines of stress, giving bones strength

Fig 6.2b

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Mic. Structure of Compact Bone

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Skeleton: Overview o

Bone Growth and Repair • • • •

Osteoprogenitor cells – unspecialized cells Osteoblasts – bone forming cells Osteocytes – mature bone cells Osteoclasts – break down bone

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Skeleton: Overview Bone Development and Growth

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Ossification – formation of bone

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Epiphyseal plate

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Intramembranous ossification Bone forms between two sheets of fibrous connective tissue Form bones of the skull Endochondral ossification Form most bones of the human body Hyaline cartilage models are replaced by bone Band of cartilage in the epiphyses of long bones Long bone growth continues until plate is ossified

Appositional growth – increase in bone diameter 8

Fig 6.3

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Skeleton: Overview •

Remodeling of Bones Bone is continually being broken down and built up again Osteoclasts remove worn cells and deposit calcium in the blood Osteoblasts remove calcium from the blood and form new bone Three important hormones regulating bone growth

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Parathyroid hormone Calcitonin Growth hormone 10

Skeleton: Overview •

Bone Repair

Required after it fractures (breaks) Steps involved in bone repair

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Hematoma Fibrocartilaginous callus Bony callus Remodelling

Naming of fractures

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Complete – bone is broken through Incomplete – bone is not separated into two parts Simple – does not pierce the skin Compound – pierces the skin Impacted – broken ends are wedged into each other Spiral – ragged break due to twisting of bone Reduction – repair of a fracture Closed reduction – re-aligning bone fragments without surgery Open reduction – surgical repair of the bone using plates, screws, or pins 11

Fig 6.4

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Table 6.1

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Fig 6.5

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Axial Skeleton o o

Lies in the midline of the body Bones of the axial skeleton • • • • •

Skull Hyoid bone The vertebral column The thoracic cage Middle ear bones

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Axial Skeleton •

Skull Formed by the cranium and the facial bones Sinuses

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Air spaces within the bones Lined by mucous membranes Reduce the weight of the skull Give the voice a resonant sound Paranasal sinuses Maxillary Frontal Sphenoidal Ethmoidal Mastoid sinuses 16

Fig 6.6

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Axial Skeleton •

Bones of the Cranium

Protects the brain Sutures – immovable joints Composed of eight bones

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Frontal bone Parietal bones Occipital bone Temporal bones External auditory meatus Mandibular fossa Mastoid process Styloid process Zygomatic process Sphenoid bone Ethmoid bone Crista galli Cribriform plate Perpendicular plate Superior and middle nasal conchae 18

Fig 6.7a

Fig 6.7b

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Fig 6.8a

Fig 6.8b

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Cranium Sphenoid (1) • base of cranium • sides of skull • floors and sides of orbits • sella turcica • sphenoidal sinuses

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Cranium

Ethmoid (1) • roof and walls of nasal cavity • floor of cranium • wall of orbits • cribiform plates • perpendicular plate • superior and middle nasal conchae • ethmoidal sinuses • crista galli

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Axial Skeleton B. Bones of the Face Maxillae x2 (upper jaw)

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Alveolar process ( tooth sockets) Palatine process (form the anterior portion of the hard palate, roof of the mouth)

Palatine bones x2 (nasal cavity) Zygomatic bones x2 (side of the orbits) Lacrimal bones x2 (medial wall of the orbits) Nasal bones x2 Vomer bone Inferior nasal conchae x2 Mandible (lower jaw)

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Mandibular condyle (articular with a temporal bone) Coronoid process 23

Axial Skeleton Bones of the Face

•

Maxillae

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Alveolar process Palatine process

Palatine bones Zygomatic bones Lacrimal bones Nasal bones Vomer bone Inferior nasal conchae Mandible

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Mandibular condyle Coronoid process

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Facial Skeleton Palatine (2) • L shaped bones located behind the maxillae • posterior section of hard palate • floor of nasal cavity • lateral walls of nasal cavity

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Facial Skeleton

Mandible (1) • lower jaw • body • ramus • mandibular condyle • coronoid process • alveolar process • mandibular foramen • mental foramen

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Skeletal Muscles of the Body • Hyoid bone  

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Superior to larynx Only bone in the body that does not articulate with another bone Anchors the tongue Site of attachment for muscles associated with swallowing

Fig 6.5a

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Axial Skeleton Vertebral Column (Spine)

•

Supports rib cage Serves as a point of attachment for the pelvic girdle Protects the spinal cord Consists of a series of separate bones named for their location

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Seven cervical (neck) Twelve thoracic (chest) Five lumbar (lower back) Five sacral Three to five coccygeal

Normal curvatures

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Fig 6.9

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Axial Skeleton Normal curvatures

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Cervical and lumbar – convex anteriorly Thoracic and sacral – concave anteriorly Provide support and balance Abnormalities Lordosis – exaggerated lumbar curvature Kyphosis – increased roundness of the thoracic curvature Scoliosis – abnormal lateral curvature that occurs most often in the thoracic region

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Fig 6.10

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Axial Skeleton Intervertebral Disks

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Prevent vertebrae from grinding against one another Absorb shock Allow motion between vertebrae

Vertebrae

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Body – anterior portion Vertebral foramin – canal for spinal cord Bony projections serve as sites for muscle attachment Atlas (C1) – supports the head; allows head movement up and down Axis (C2) - serves as a pivot for the atlas; allows head movement from side to side Sacrum – fused sacral vertebrae; forms posterior wall of the pelvic cavity Coccyx – formed from a fusion of three to five vertebrae 32

Fig 6.11

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Axial Skeleton •

The Rib Cage Protects the heart and lungs Provides support for the bones of the pectoral girdle The ribs

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Twelve pair that connect to the thoracic vertebrae True ribs – upper seven pairs connect directly to the sternum by costal cartilages False ribs – next five pair that attach indirectly to the sternum or not at all (“floating” ribs)

The sternum

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Flat, blade-shaped bone Composed of three bones that fuse Manubrium Body Xiphoid process 34

Fig 6.12

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Appendicular Skeleton o

Pectoral Girdle •

Clavicles   

•

Articulate medially with the manubrium Only attachment to the axial skeleton Serves as a brace for the scapula and stabilizes the shoulder

Scapulae    

Spine Acromion process Coracoid process Glenoid cavity

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Fig 6.13

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Appendicular Skeleton o

Upper Limb •

Humerus  

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Long bone of the arm Head articulates with the glenoid cavity of the scapula Greater and lesser tubercles serve as attachments for muscles Intertubercular groove holds a tendon from the biceps brachii Deltoid tuberosity attaches the deltoid Capitulum articulates with the head of the radius Trochlea articulates with the ulna Coronoid fossa Olecranon fossa 38

Fig 6.14

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Appendicular Skeleton •

Radius  

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Lateral side of the forearm Head articulates with the capitulum of the humerus and fits into the radial notch of the ulna Radial tuberosity attaches a tendon from the biceps brachii Ulnar notch articulates with the head of the ulna Styloid process attaches ligaments that run to the wrist

Ulna  

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Longer bone of the forearm Coronoid process articulates with the coronoid fossa when elbow is flexed Olecranon process articulates with the olecranon fossa when the elbow is extended Trochlear notch articulates with the trochlea of the humerus Head articulates with the ulnar notch of the radius Styloid process attaches ligaments that run to the wrist 40

Fig 6.15

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Appendicular Skeleton •

Hand Wrist (carpus) contains eight small bones Metacarpal bones form the palm Phalanges

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Bones of the fingers The thumb has only two phalanges (proximal and distal) The other fingers have three phalanges each (proximal, middle, and distal)

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Fig 6.16

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Appendicular Skeleton o

Pelvic Girdle •

Coxal bones Ilium Ischium Pubis

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Pubic symphysis Obturator foramen

Gender differences      

Female Female Female Female Female Female

has broader hips pelvis is wider inlet and outlet of the true pelvis are wider pelvic cavity is more shallow bones are lighter and thinner pubic arch is wider 44

Fig 6.17

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Appendicular Skeleton o

Lower Limb •

Femur   

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Longest and strongest bone in the body Head fits into acetabulum of coxal bone Greater and lesser trochanters attach muscles of the thigh and buttocks Linea aspera attaches several muscles Medial and lateral epicondyles attach muscles and ligaments Lateral and medial condyles articulate with the tibia Patellar surface articulates with the patella

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Fig 6.18

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Appendicular Skeleton • Tibia 

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Medial bone of the lower leg Bears the weight from the femur Medial and lateral condyles articulate with the femur Tibial tuberosity attach patellar ligaments Anterior crest Medial malleolus articulates with the talus in the foot

Fig 6.19

• Fibula  

Lateral to the tibia Stabilizes ankle 48

Appendicular Skeleton • Foot  

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Seven tarsal bones Only the talus can move freely The calcaneus and the talus support the weight of the body Five metatarsal bones form the instep The phalanges form the toes  

Fig 6.20

Big toe has only two Three each in other toes

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Joints (Articulations) o

Classification according to the amount of movement • • •

o

Synarthrosis – immovable Amphiarthrosis – slightly moveable Diarthrosis – freely moveable

Classification according to structure • • •

Fibrous Cartilaginous Synovial

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Joints (Articulations) •

Fibrous – fibrous connective tissue Fibrous connective tissue joins bone to bone Typically immovable Sutures of the cranium

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Coronal – between the parietal bones and the frontal bone Lambdoidal – between the parietal bones and the occipital bone Squamosal – between each parietal bone and each temporal bone Sagittal – between the parietal bones

Joints formed by each tooth in its socket 51

Fig 6.7

Fig 6.8

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Joints (Articulations) •

Cartilaginous 

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•

Bones are joined by fibrocartilage or hyaline cartilage Usually slightly moveable

Synovial   

Bones do not touch each other Bones are separated by a joint cavity Usually freely moveable

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Fig 6.21

Fig 6.22

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Joints (Articulations) Types of synovial joints

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Saddle joint Ball-and-socket joint Pivot joint Hinge joint Gliding joint Condyloid joint

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Fig 6.23

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Joints (Articulations) Movements permitted by synovial joints

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Angular movements Flexion Extension Adduction Abduction Circular movements Circumduction Rotation Supination Pronation Special movements Inversion and eversion Elevation and depression

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Fig 6.24

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Effects of Aging Cartilage and bone tend to deteriorate Articular cartilage may not function properly, resulting in arthritis

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Osteoarthritis – deterioration of the articular cartilage Rheumatoid arthritis – synovial membrane becomes inflamed Gout – excessive buildup of uric acid

Osteoporosis is common 59

Homeostasis o

Functions of the Skeletal System • • • • • •

Protection of internal organs Bones assist in all phases of respiration Bones store and release calcium Bones assist the lymphatic system and immunity Bones assist digestion The skeleton is necessary to locomotion 60

Homeostasis o

Functions of Other Systems • •

•

The integumentary and the muscles assist in protecting internal organs The digestive system absorbs calcium from food and the endocrine system regulates the storage of calcium in the bones Movement of the bones is only possible because of the contraction of skeletal muscle 61