1

The Skeletal

System

Chapter 7

The Skeletal System

• Parts of the skeletal system

• Bones

• Joints

• Cartilages

• Ligaments

• Divided into 2 divisions

• Axial skeleton

• Appendicular skeleton

Functions of Bones

• Supports the body

• Protects soft organs

• Movement

• Storage of minerals and fats

• Blood cell formation -

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Bones of the Human Body

• The skeleton has bones

• 2 basic types of bone tissue

• Compact bone

• Solid - strength

• Spongy bone

• Made of trabeculae – small needle-like pieces of bone

• Many open spaces

Compact & Spongy Bone

7-4

Classification of Bones• 4 types of bones – long, short, flat & irregular,

• Long bones

• Typically longer than wide

• Have a shaft with heads at both ends

• Examples:

• Short bones

• Generally cube-shape

• Contain mostly spongy bone

• Examples:

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Classification of Bones• Flat bones

• Thin and flattened

• Usually curved

• Thin layers of compact bone around spongy bone

• Examples: Skull, ribs, sternum, scapula

• Irregular bones

• Irregular shape

• Example:

Slide 5.4cCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Figure 5.1

Gross Anatomy of a Long Bone

• Diaphysis

• Shaft

• Composed of mostly compact bone

• Epiphysis

• Ends of bone

• Composed mostly of spongy bone

• Proximal & distal ends Figure 5.2a

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Structures of a Long Bone• Periosteum

• Outside covering of the diaphysis

• Fibrous connective tissue

• Sharpey’s fibers

• Secures periosteum to underlying bone

• Arteries

• Supply bone cells with nutrients

• Endosteum

• Inner layer

Structures of a Long Bone

• Articular cartilage

• Covers external

surface of the epiphyses

• Decreases friction at joint surfaces

• Epiphyseal plate –

growth plate

Figure 5.2a

Structures of a Long Bone

• Medullary cavity

• Cavity of the shaft

• Contains yellow marrow (fat)

Figure 5.2a

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Terms

� Openings or depressions � Foramen –

� Meatus – canal or passageway

� Sinus – cavity in bones

� Fissure – slit like opening

� Fossa –

� Projections � Tubercule – small, rounded knob

� Tuberosisty – larger than tubercule; rounded knob

� Trochanter – very large, irregular knob

TERMS

� Projections

� Crest – narrow ridge

� Spine – sharp, pointed projection

� Condyle – rounded articular projection

� Epicondyle – raised area on or above condyle

� Facet – flat, smooth articular surface

� Head – bony expansion above neck

Microscopic Anatomy of Bone

• Osteon (Haversian System)

• A unit of bone tissue

• Central (Haversian) canal

• Opening in the center of an osteon

• Carries blood vessels & nerves

• Perforating (Volkman’s) canal

• Canal perpendicular to the central canal

• Carries blood vessels & nerves

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Microscopic Anatomy of Bone• Osteocytes –

• Lacunae

• Cavities containing bone cells; arranged in concentric rings

• Lamellae

• -

• Canaliculi

• Tiny canals that radiate from the central canal to lacunae

• Form a transport system

Bone Growth

• Epiphyseal plates allow for growth of long bone during childhood

•New cartilage is continuously formed

•Older cartilage becomes ossified

•Bone replaces cartilage

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Arrows

indicate

growth plates

are still

present.

Epiphyseal

plates usually

calcify

between the

ages of 17-25.

Types of Bone Cells

• Osteocytes

• Mature bone cells

• Osteoblasts

• Bone-forming cells

• Osteoclasts

• Bone-destroying cells

• Break down bone for remodeling & release of Ca

Skeleton

• Divided into 2 divisions

• Axial skeleton

• Appendicular skeleton

8

The Axial Skeleton

• Forms the longitudinal part of the body

• Divided into 3 parts

• Skull

• Vertebral column

• Thorax

The Axial Skeleton

The Skull

• 2 sets of bones

• Cranium

• Facial bones

• Bones are joined by sutures

• Only the mandible is attached by a freely

movable joint

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The Skull

Skull

Frontal (1)

• forehead

• frontal sinuses

• supraorbital foramen

• coronal suture

SkullParietal (2)

• side & roof of cranium

• sagittal suture

• coronal suture

• lambdoidal suture

• squamosal suture

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SkullTemporal (2)

• side of skull

• below parietal

• floor of cranium

• squamosal suture

• external acoustic meatus

• mastoid process

• styloid process

• zygomatic process

Mastoid

Styloid

Zygomatic

Process

SkullOccipital (1)

• back of skull

• foramen magnum

• occipital condyles

• external occipital

protuberence

• lambdoidal suture

SkullSphenoid (1)

• base of cranium

• sides of skull

• butterfly bone

• sella turcica Sella turcica

Sphenoid

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Skull

Ethmoid (1)

• roof and walls of nasal cavity

• cribiform plates

• perpendicular plate

• ethmoidal sinuses

Facial SkeletonMaxillary (2)

• upper jaw

• anterior roof of mouth

• house upper teeth

• palatine suture

Facial SkeletonPalatine (2)

• L-shaped bones behind maxillae

• posterior section of hard palate; forms

soft palate

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Facial SkeletonZygomatic (2)

• prominences of cheeks

• lateral walls & base of orbits

Facial SkeletonLacrimal (2)

• medial walls of orbits

• groove from orbit to

nasal cavity carries tears to

nasal cavity

Nasal (2)

• bridge of nose

Facial SkeletonVomer (1)

• inferior portion of nasal cavity

• joins w/ethmoid to form nasal septum

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Facial SkeletonNasal Conchae (2)

• extend from lateral walls of nasal cavity

•Superior

•Middle

•Inferior

Facial SkeletonMandible (1)

• lower jaw

• ramus

• mandibular condyle

• coronoid process

• mandibular foramen

• mental foramen

Bones of the Skull

Figure 5.11

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Human Skull, Superior View

Figure 5.8

Human Skull, Inferior View

Figure 5.9

Sinuses• Cavities w/in cranium

• Functions

• Lighten the skull

• Give resonance & amplification to voice

Figure 5.10

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The Hyoid Bone

• only bone that does

not articulate

w/another bone

• Base for the tongue

The Vertebral Column

• Vertebrae

separated by intervertebral discs

• Each vertebrae is

given a name & #

according to its location

Figure 5.14

Structure of a Vertebrae

Figure 5.16

• Body - large flat area;

supports wt. of body

• Vertebral foramen – opening

for spinal cord

• Spinous process – posterior

projection

• Transverse process – lateral

projections on either side

• Pedicle – upper extension of

body

• Lamina – arch of vertebrae

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3 Types of Vertebrae• Cervical - first 7 vertebrae of neck

• Only vertebrae w/ transverse foramen

• Only vertebrae w/ bifed spinous process

• Atlas –

• Axis – 2nd vertebrae with dens; pivot joint that allows head to

rotate

• Thoracic – vertebrae

•Long angled spinous processes

• Lumbar – in lower back

• Thickest body

• Spinous process are shorter & thicker

Cervical Vertebrae

Thoracic Vertebrae

Lumbar Vertebrae

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Sacrum and Coccyx

� Sacrum – 5 fused vertebrae; join with/hip bones

� Coccyx – 4 fused vertebrae; forms tailbone

The Thorax

• Protects

major organs

Figure 5.19a

• Made up of

3 parts

• Sternum

• Ribs

• Thoracic vertebrae

Thorax

� Ribs – 12 pair

� True ribs – attached to sternum (1-7)

� False ribs – attached to cartilage of 7th

� Floating ribs – not attached to any structure

� Sternum – connected to ribs by cartilage

� Manubrium – superior region of sternum

� Body – main part

� Xiphoid – inferior end; used in landmarking for CPR

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The Appendicular Skeleton

• Limbs (appendages)

• Pectoral girdle (shoulder)

• Pelvic girdle

Pectoral Girdle

• Composed of 2 bones

• Clavicle – collarbone; connects to sternum

& scapula

• Scapula – shoulder blade; connects to

humerus & clavicle

Shoulder

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Bones of the Shoulder Girdle

Bones of the Shoulder Girdle

Bones of the Upper Limb

• Humerus -long bone

forming

upper arm

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Bones of the Upper Limb

• The forearm has

2 bones

•Ulna –inner

bone

•Radius – bone

inline w/thumb

Bones of the Upper Limb• The hand

•Carpals – wrist

•Metacarpals – palm

•Phalanges – fingers

• Distal

• Middle

• Proximal

So Long Top Part Here Comes The Thumb

� S – scaphoid

� L – lunate

� T – triquetrum

� P – pisiform

� H – hamate

� C – capitate

� T – trapezoid

� T – trapezium

Carpal Bones

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Bones of the Pelvic Girdle

• Coxal - hip bones

• Composed of three pair of fused bones

• Ilium

• Ischium

• Pubic bone

• The wt. of the upper body rests on the pelvis

• Protects several organs

• Reproductive organs

• Bladder

• Part of the large intestine

Illum� Form most of hip

� iliac crest – upper edge

� iliac fossa – depression under crest

� greater sciatic notch – large indentation for nerves

� sacroiliac joint – joins w/sacrum

� anterior superior spine – front of iliac crest

� posterior superior spine – back of iliac crest

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Ishium

� Sit down bone

� ischial tuberosity – bony area that supports wt when sitting

� lesser sciatic notch – indentation for nerves

� ischial spine – points toward pelvic cavity

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Pubis

� Most anterior bone

� Obturator foramen – largest opening in body; blood & nerves pass to thigh

� Acetabulum – articulation of femur

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Bones of the Lower Limbs

• Femur- upper

thigh bone

• Articulates with

acetabulum

• Largest bone

Bones of the Lower Limbs

Slide

5.40b

• 2 bones of

lower leg

• Tibia - medial

• Fibula – lateral

Bones of the Lower Limbs

• The foot

•Talus –

•Metatarsals

– sole

•Phalanges –

•Calcaneus - Figure 5.25

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Foot

� Tarsals (14)

� calcaneus

� talus

� navicular

� cuboid

� lateral cuneiform

� intermediate cuneiform

� medial cuneiform