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Chapter 7Skeletal System

Bone Classification

• Long Bones• Short Bones• Flat Bones• Irregular Bones• Sesamoid (Round) Bones

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• Functions– Support– Protection

• internal organs

– Movement facilitation• Bones act as the levers

• Articulations as the fulcrums

• Muscles provide the force

Skeletal System

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• Functions– Mineral Storage

• calcium and phosphorous

– Storage of Blood Cell Producing Cells• red bone marrow

– Storage of Energy• lipids stored in yellow bone marrow are

important source of chemical energy

Skeletal System

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Bone Function

• Support, Movement & Protection• gives shape to head, etc.• supports body’s weight• protects lungs, etc.• bones and muscles interact when limbs or body parts move

• Blood Cell Formation• hematopoiesis• red marrow

• Inorganic Salt Storage• calcium • phosphate• magnesium• sodium• potassium

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• Cartilage, Osseous and Dense CT

• Osseous Tissue (4 cell types)– Osteoprogenitor

• Found throughout the bone

• Have mitotic potential

• May differentiate into osteoblast

Cells and Histology of Bone

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• Osseous Tissue (4 cell types)– Osteoblast

• No mitotic potential

• Found on the surface of the bone

• Secrete mineral salts and organic components for bone formation

Cells and Histology of Bone

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• Osseous Tissue (4 cell types)– Osteocytes

• No mitotic potential• Found within the bone• Maintain daily cellular activities of bone tissue

– Osteoclast• Found on the surface of bone• Function in the re-absorption of bone

Cells and Histology of Bone

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• Epiphysis• distal end• proximal end

• Articular Cartilage• Covers each

epiphysis• Hyaline cartilage

• Diaphysis• Shaft

• Metaphysis• Area between

diaphysis and epiphysis in mature bone

Parts of a Long Bone

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• Periosteum• Contains nerves,

blood vessels, osteo cells

• Attachment point for ligaments and tendons

• Medullary cavity• contains yellow

marrow• Endosteum

• lines the medullary cavity

Parts of a Long Bone

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• Spongy Bone

• Irregular lattice work of bone-trabeculae

• Spaces filled with red marrow

• produces RBCs

Parts of a Long Bone

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• Compact Bone• Tightly packed tissue• Parts

• Concentric Lamellae• Concentric circles of

tightly packed tissue• Volkmann’s Canals

• Penetrate compact bone

• Allow blood vessels and nerves into medullary cavity and other Haversian Canals

Parts of a Long Bone

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• Compact Bone• Haversian Canals

• Run longitudinally through the compact bone

• Concentric lamellae surround the canals

• Lacunae• Open spaces between the

concentric lamellae that contain osteocytes

• Look like “little lakes”

Parts of a Long Bone

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• Compact Bone– Canaliculi

• Tiny canals that radiate away from the lacunae

– Osteon (Haversian System)• Central canal,

surrounding lamellae, lacunae, osteocytes and canaliculi

Parts of a Long Bone

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Bone Development

Intramembranous Ossification• bones originate within sheetlike layers of connective tissues• broad, flat bones

• skull bones (except mandible)• intramembranous bones

Endochondral Ossification• bones begin as hyaline cartilage

• form models for future bones• most bones of the skeleton• endochondral bones

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Endochondral Ossification

• hyaline cartilage model• primary ossification center• secondary ossification centers

• epiphyseal plate• osteoblasts vs. osteoclasts

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• Hyaline cartilage model• “bone” created by

chondroblast

• Actual ossification of this “bone” starts 6-7 weeks after conception

Endochondral Ossification

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• Interstitial and Oppositional Growth• Chondrocytes burst

and trigger calcification

• Capillaries and bone cells invade dying cartilage

• Bone starts to calcify

Endochondral Ossification

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• Primary Ossification Center• Blood vessels in mid-

region produce ossification center

• Osteoblast form spongy bone in the area of calcified cartilage, this causes the center to enlarge

• Spongy bone is destroyed by osteoclast-forms medullary cavity

Endochondral Ossification

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• Secondary Ossification Centers• When blood vessels enter

the epiphysis

• Spongy bone created here will stay

• Epiphyseal plate• Layer of hyaline

cartilage between the 2 areas of growth

• Stays until you reach maturity

Endochondral Ossification

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• Remnants of hyaline cartilage on the epiphysis becomes articulating cartilage

Endochondral Ossification

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Growth at the Epiphyseal Plate

First layer of cells• closest to the end of epiphysis• resting cells• anchors epiphyseal plate to epiphysis

Second layer of cells• many rows of young cells• undergoing mitosis

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Growth at the Epiphyseal Plate

Third layer of cells• older cells• left behind when new cells appear• cells enlarging and becoming calcified

Fourth layer of cells• thin• dead cells• calcified extracellular matrix

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Homeostasis of Bone Tissue

•Bone Re-absorption – action of osteoclasts and parathyroid hormone•Bone Deposition – action of osteoblasts and calcitonin

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Factors Affecting Bone Development, Growth, and

Repair

• Deficiency of Vitamin A – retards bone development• Deficiency of Vitamin C – results in fragile bones • Deficiency of Vitamin D – rickets, osteomalacia• Insufficient Growth Hormone – dwarfism• Excessive Growth Hormone – gigantism, acromegaly • Insufficient Thyroid Hormone – delays bone growth• Sex Hormones – promote bone formation; stimulate ossification of epiphyseal plates• Physical Stress – stimulates bone growth

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• Process• bony prominence “bump”• Condyle

• rounded or knuckle like process

• Tubercle• small process

• Tuberosity• large process (tibial tuberosity)

• Trochanter• huge process (located on the proximal end of the femur)

Superficial Bone Anatomy

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• Crest• narrow ridge of bone

• Spine • sharp slender process (holes and/or depressions)

• Fissure• narrow slit through which blood vessels or nerves

pass

• Foramen • opening through which blood vessels and nerves

pass

Superficial Bone Anatomy

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• Meatus • tubelike passageway running within a bone

• Sulcus or groove• furrow that accommodates a soft structure such as

blood vessels, nerves or tendons

• Fossa• depression in or on the surface of a bone

Superficial Bone Anatomy

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Life-Span Changes

• decrease in height at about age 30• calcium levels fall• bones become brittle• osteoclasts outnumber osteoblasts• spongy bone weakens before compact bone• bone loss rapid in menopausal women• hip fractures common• vertebral compression fractures common

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• Impacted • one fragment is firmly driven into the other

• Displaced• anatomical alignment is NOT preserved

• Non-displaced• anatomical alignment is preserved

• Stress• partial fracture resulting in bones inability to

withstand forces• About 25% involve distal end of the fibula

Clinical Application: Fractures

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Clinical Application

Types of Fractures

• green stick• fissured• comminuted• transverse• oblique• spiral

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• Pathologic• caused by weakening of the bone due to a disease

• Pott’s• fracture of the distal end of the fibula with serious

injury to the distal tibial articulation • Severe eversion sprain may lead to this

• Colle’s• fracture at the distal end of the radius in which the

distal end is displaced posteriorly• Occurs frequently when you try to stop yourself from

falling

Clinical Application: Fractures

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• Fracture breaks blood vessels found in the Haversian system

• Blood clot forms at the site of the break within 6 to 8 hours (fracture hematoma)

• Fracture hematoma• serves as the focus for

cellular invasion

Clinical Application: Fracture Repair

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• Callus forms• New bone tissue

developed around the fracture

• Site of osteoblast activity

Clinical Application: Fracture Repair

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• Remodeling• Dead bone is

absorbed by osteoclast

• Compact bone replaces spongy bone in the fractured area

Clinical Application: Fracture Repair

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• Osteoporosis• Age related disease

characterized by decreased bone mass an increased chance of fractures

• Decreased levels of estrogen (sex hormones that stimulate osteoblast)

Clinical Application: Disorders

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• Osteoporosis• White women more than men and people of color• Other factors linked to osteoporosis

• Body build• short people have less bone mass

• Weight• thin people have less adipose, which stores estrogen

• Smokers- • low estrogen levels

• Calcium deficiency and mal-absorption• Vitamin D deficiency• Certain drugs-

• alcohol, cortisone, etc.

• Premature menopause

Clinical Application: Disorders

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• Osteoporosis Prevention– Exercise

• muscle action stimulates blood flow to bone tissue

– Estrogen pills- • for post menopause women

– Calcium supplements/ vitamins– Prescription anabolic steroids-

• increase hormone levels– Sodium Fluoride stimulates oteoblast

Clinical Application: Disorders

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• Osteogenic Sarcoma• Malignant bone tumor that affects osteoblast• People between ages of 10-25• Left untreated it will metasticize and lead to

death• Treatment includes chemotherapy following

amputation of affected area

Clinical Application: Disorders

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• Rickets– Vitamin D deficiency in children– Body can’t transport Ca+2 and P-3 from GI tract to

blood– Osteoblasts in diaphysis don’t calcify causing bones

to stay soft– Weight of body causes the legs to bow– Cure and prevention

• Dietary- add vitamin D, calcium and phosphorus in large amounts

• Exposing the skin to ultraviolet rays of light

Clinical Application: Disorders

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Skeletal Organization

Axial Skeleton• head • neck • trunk

Appendicular Skeleton• upper limbs• lower limbs• pectoral girdle• pelvic girdle

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Skeletal Organization

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• Hyoid Bone– Supports tongue– Attachment point

for muscles that move tongue

Skeletal Organization

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Cranium

Frontal (1)• Forehead• Roof of nasal cavity• Roofs of optical orbits• Frontal sinuses• Supraorbital foramen

•Blood vessels and nerve

• Coronal suture• Develops in two parts

•Completely fused by age 5 or 6

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Cranium

Parietal (2)• Side walls of cranium• Roof of cranium• sagittal suture

•Fuses two parietal bones together

•Coronal suture•Fuses parietal bones to frontal bone

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Cranium

Occipital (1)• back of skull• base of cranium• foramen magnum

•Inferior part of brain stem connects with spinal cord

• occipital condyles•Either side of foramen magnum

• lambdoid suture•Fuses parietal bones with occipital bone

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CraniumTemporal (2)

• side walls of cranium• floor of cranium• floors and sides of orbits• squamous suture

•Fuses parietal with temporal

• external acoustic meatus•Leads to inner ear

• mandibular fossa•Where mandible meets temporal bone

• mastoid process•Neck muscle attachment

• styloid process•Tongue and pharynx attachment

• zygomatic process

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Cranium

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

•Indentation along midline within cranial cavity•Contains pituitary gland

• sphenoidal sinuses

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Cranium

Ethmoid (1)• roof and walls of nasal cavity• floor of cranium• wall of orbits• cribriform plates

•Join two parts of ethmoid on either side of nasal cavity

• perpendicular plate•Forms most of nasal septum

• superior and middle nasal conchae

•Support mucous membranes of nasal cavity

• ethmoidal sinuses• crista galli

•Projects upward into cranial cavity •Attaches brain membranes

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Facial Skeleton

Maxillary (2)• upper jaw• anterior roof of mouth• floors of orbits• sides of nasal cavity• floors of nasal cavity• alveolar processes• maxillary sinuses• palatine process

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Facial Skeleton

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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

Zygomatic (2) • prominences of cheeks• lateral walls of orbits• floors of orbits• temporal process

•Extends posteriorly to join zygomatic process of temporal bone

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Facial Skeleton

Lacrimal (2)• medial walls of orbits• groove from orbit to nasal cavity

Nasal (2)• bridge of nose

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Facial Skeleton

Vomer (1)• inferior portion of nasal septum

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Facial Skeleton

Inferior Nasal Conchae (2)• extend from lateral walls of nasal cavity

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Facial Skeleton

Mandible (1)• Lower jaw• Body

•Horseshoe shaped portion

• Ramus•Flat, upward projections

• Mandibular condyle•Fits into mandibular fossa

• Coronoid process•Chewing muscle attachment

• alveolar process• mandibular foramen• mental foramen

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Infantile Skull

Fontanels – fibrous membranes

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Vertebral Column

• cervical vertebrae (7)• thoracic vertebrae (12)• lumbar vertebrae (5)• sacrum • coccyx

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Vertebral Column• cervical curvature

•Smallest vertebrae•Most dense bone tissue

• thoracic curvature• lumbar curvature• sacral curvature• rib facets• vertebra prominens

•Long spinous process on 7th vertebra

• intervertebral discs• intervertebral foramina

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Cervical Vertebrae

• Atlas – 1st; supports head• Axis – 2nd; dens pivots to turn head• transverse foramina

•Blood vessels leading to the brain pass through

• bifid spinous processes•Muscle attachment

• vertebral prominens • useful landmark

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Thoracic Vertebrae

• long spinous processes• rib facets

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Lumbar Vertebrae

• large bodies•Support weight

• thick, short spinous processes

•Nearly horizontal

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Sacrum

• five fused vertebrae•Fuse between age 15 and 30

• median sacral crest•Fused spinous processes

• posterior sacral foramina• posterior wall of pelvic cavity• sacral promontory

•Body of the 1st sacral vertebra

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Coccyx

• tailbone• four fused vertebrae

•Fuse by age 25

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Thoracic Cage

• Ribs• Sternum• Thoracic vertebrae• Costal cartilages• Supports shoulder (pectoral) girdle and upper limbs• Protects viscera• Role in breathing

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Ribs

• True ribs (7)•Attach to sternum by costal cartilage

• False ribs (5)•Costal cartilage does not reach sternum•Top 3 join cartilage of 7th True rib•Bottom 2 don’t attach at all

• floating (2)

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Rib Structure

• Shaft• Head

•posterior end•articulates with vertebrae

• Tubercle •articulates with vertebrae

• Costal cartilage •hyaline cartilage

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Sternum

• Manubrium• Body• Xiphoid process

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• Comprised of 2 parts– Pectoral girdle and upper extremity

• Shoulders and arms

– Pelvic girdle and lower extremity• Hips and legs

Appendicular Skeleton

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Pectoral Girdle

• attach bones of the upper extremities to the axial skeleton

•Shoulder Girdle •clavicles - anterior• scapulae - posterior

• supports upper limbs

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Clavicles

•Long slender bone with double curvature •Sternal end

•Rounded end•articulates with manubrium

•Acromial end•Broad flat end• articulates with scapula (acromion process)

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Scapulae

• spine•Runs diagonally across body• supraspinous fossa• infraspinous fossa

•Triangular flat bone •Posterior part of the thorax •Between the 2nd and the 7th rib •Medial border

•5 centimeters from the vertebral column

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• acromion process

• part of the spine that expands past the body

• coracoid process• located at the lateral

end of the superior ridge

• glenoid cavity• fossa inferior to the

acromian process• Articulates with the

head of the humerus to make a ball and socket joint

Scapulae

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Scapulae

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• Consists of 60 bones• Each side contains 30 bones

– 1 humerus– 1 radius– 1 ulna– 8 carpals– 5 metacarpals – 14 phalanges

Upper Limb

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Upper Limb

• Humerus• Articulates proximally with the scapula and distally with both the radius and the ulna• Largest bone in the upper extremity

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Humerus• Head

•rounded proximal end, articulates with glenoid cavity

•Anatomical neck•Slight groove below head•Epiphyseal plate

• Greater tubercle•large lateral process below the anatomical neck

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• lesser tubercle• anterior side

• Intertubercular groove• Surgical neck

• Constricted portion inferior to tubercles

• Fractures likely here• Deltoid tuberosity

• Slight bump on the anterior surface

• Insertion point for deltoid muscle

Humerus

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• Capitulum• rounded knob• articulates with head of

radius• Trochlea

• Pulley-like surface that articulates with ulna

• Coronoid fossa• Receives part of the ulna

when elbow is flexed• On anterior, distal

surface

Humerus

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• Olecranon fossa• posterior side • receives olecranon

process of ulna when elbow is extended

• Medial and Lateral Epicondyles• Found on either side

of distal end of humerus

• Serve as attachments of most forearm muscles

Humerus

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• Ulnar nerve

• Lies over the posterior surface of the medial epicondyle

• Can be rolled between the finger and the medial epicondyle

Humerus

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Ulna• medial forearm bone• trochlear notch

•Curved area between olecranon and coronoid process•Articulates with trochlea of humerus•Allows for flexion and extension of elbow

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• Olecranon process• posterior projection • proximal end

• Coronoid process• anterior projection-

lateral• Styloid process

• posterior side of the head of the ulna

• Head• distal end of the ulna

Ulna

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Radius• lateral forearm bone• Head

•Disc like structure that articulates with capitulum of humerus and radial notch of ulna

• Radial tuberosity•Proximal end inferior to head•Anterior surface

• Styloid process•Distal end•Articulates with scaphoid bone

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Wrist and Hand

• Carpals (16)• trapezium• trapezoid• capitate• scaphoid• pisiform• triquetrum• hamate• lunate

• Metacarpals (10)

• Phalanges (28)• proximal phalanx• middle phalanx• distal phalanx

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Pelvic Girdle

•Provide a strong support for the lower extremities• Coxae (2)

•Each is 3 bones fused together•Os coxa (1)

•Sacrum• supports trunk of body• protects viscera

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Coxae

• hip bones•Acetabulum

•lateral fossa of the os coxa where 3 pelvic bones merge

• Ilium•Superior to other 2 portions •iliac crest

•superior border•serves as insertion point for abdominal wall

muscles

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• Ilium• Iliac fossa

• internal surface seen from the medial side

• gives the pelvis a bowl shape appearance

• Greater sciatic notch• Inferior to iliac crest• Posterior to

acetabulum• Allows for major

nerves and blood vessels to travel from sacrum to legs

Coxae

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• Ischium• inferior, posterior

portion of the coxal bone

• ischial spines• Posterior, superior

to ischial tuberosity• lesser sciatic notch

• Inferior to ischial spine

• ischial tuberosity• tuberosity that we

sit on

Coxae

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• Pubis• orbturator foramen

• between ischium, pubic bone and acetabulum

• symphysis pubis• Joins with other

pubic bone at symphysis pubis

• Hormone, relaxin, is released during child birth that allows greater flexibility of the fibrocartilage

Coxae

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Greater and Lesser Pelvis

Greater Pelvis• lumbar vertebrae posteriorly• iliac bones laterally• abdominal wall anteriorly

Lesser Pelvis• sacrum and coccyx posteriorly• lower ilium, ischium, and pubis bones laterally and anteriorly

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Male and Female Pelvis

Female• iliac bones more flared• broader hips• pubic arch angle greater• more distance between ischial spines and ischial tuberosities• sacral curvature shorter and flatter• lighter bones

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Lower Limb

• Femur (2)• Patella (2)• Tibia (2)• Fibula (2)• Tarsals (14)• Metatarsals (10)• Phalanges (14)

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Femur

• Longest & heaviest bone of body•Body of femur angles toward the midline

•makes knees closer than hips•Degree is greater in females

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• Head• rounded end• articulates with acetabulum

• Neck• Distal to the head• Elderly people break this

area often• Greater trochanter &

Lesser trochanter• large processes below the

neck • serve attachment points for

some thigh and buttock muscles

Femur

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• Shaft• diaphysis

• Linea aspera• Posterior side of shaft

• Serves as insertion point for adductor muscles of the leg

• Medial & Lateral epicondyles• Distal end of femur• Articulates with proximal

end of tibia

Femur

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• Intercondylar fossa• important area for the

ligaments in the knee

• Patellar surface• distal anterior surface

between the condyles that forms a gliding joint with the patella

Femur

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Patella

• kneecap•Inferior end is called the Apex

• anterior surface of knee• flat sesamoid bone located in a tendon

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Tibia

• shin bone•Large, medial, weight bearing bone of the lower extremity•Lateral & Medial Condyles

•Articulate with epicondyles of femur•Inferior surface of the lateral condyle articulates with the fibula

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• Tibial tuberosity• Anterior surface of

the tibia• Surface serves as

attachment point for the patellar ligaments and tendons

• anterior crest• Extends downward

from tibial tuberosity

Tibia

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• Intercondylar Eminence• Upward projection

between the condyles of the tibia

• Cruciate ligaments attach here

• Medial malleolus• Medial projection on the

distal end of the tibia• Provides medial

supports to the hinge joint of your ankle

Tibia

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Fibula

• Lateral to tibia• Non weight-bearing• Long, slender• Head

•proximal end•more rounded

• Lateral malleolus•Distal end•articulates with the tibia and talus•Lateral support to the ankle•Longer pointier end

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Ankle and Foot• Tarsals (14)

• Calcaneus•Largest and strongest tarsal•Supports body weight•Serves as lever attachment for gastrocnemius

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• Talus• Uppermost tarsal• Only bone that

articulates with the tibia and fibula

• Initially bares all body weight, then transfers half to the calcaneus and half to the other tarsals

Ankle and Foot

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• Navicular• just anterior to the talus

• cuboid• Lateral side of the foot• Articulates with calcaneus,

the 4th and 5th metatarsal• lateral cuneiform• intermediate cuneiform• medial cuneiform

• Each cuneiform that articulates with the corresponding metatarsal

Ankle and Foot

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• Metatarsals (10)

• numbered from the medial to the lateral side

• Phalanges (28)• proximal• middle• distal

Ankle and Foot