AXIAL & APPENDICULAR

SKELETONS

First part

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THE SKELETAL SYSTEM

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The skeleton consists of• Bones (206)• Cartilages• Joints• Ligaments

Divided into axial and appendicular.

Functions of Skeletal System

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1) Support – provides solid axis for muscles to act against, creating motion.

2) Protection- bones such as skull provide barrier of protection from external forces.

3) Hematopoiesis-production of blood cells.

4 )Mineral storage (calcium especially).

22 bones in skull

6 in middle ears

1 hyoid bone

26 in vertebral column

25 in thoracic cage

4 in pectoral girdle

60 in upper limbs

60 in lower limbs

2 in pelvic girdle

206 bones in all

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Bone

Types of Bones Bones are classified

into 4 types :-

A. LongB. FlatC. IrregularD. short

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Long BonesFound in the limbsEach bone is made

of a body (diaphysis) and two

extremities (epiphyses)

Wall consists of dense tissue

Central canal called medullary canal is filled with marrow

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Short Bones

Found in skeleton where strength, compactness, and limited movement are desired

2 main examples Tarsus Carpus

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Flat Bones

Used in spots where protection or muscular attachment is desired

Main locations are skull and scapula

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Irregular Bones

Bones which don’t fit into other categories due to irregular shapes

Examples: vertebrae, sphenoid, hyoid

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Skull.Vertebral column.Thoracic cage.

Axial skeleton is shown in green

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Axial skeleton

The Skull

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Cranial bones (or cranium) Enclose the cranial cavity, which supports and

protects the brain Attachment sites for some head and neck

muscles

Facial bones (anterior aspect of skull) Form framework of face. Form cavities for sense organs of light, taste and

smell. Provides openings for passage of air and food. Hold the teeth. Anchor the muscles of the face.

Cranial bones

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parietal

parietal

frontal

temporalparietal

occipital

_______sphenoid_____ethmoid

occipital

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Facial Bones

Mandible- lower jaw bone

Maxillary bones (maxillae) fuse together to form upper jaw

Palatine processes – directly posterior to maxillae; forms rear of hard palate

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Facial Bones Contd. Zygomatic bones – cheekbones

Lacrimal bones – inferior section of orbital bones; provides passageway for tears

Ethmoid bone- forms roof of nasal cavity

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More Facial Bones Nasal bones- form

bridge of nose

Vomer – divides nasal cavity in half

Inferior conchae- thin curved bones which project from interior of nasal cavity

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Mandible

Paranasal sinuses

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Air-filled sacs in the bones “Paranasal” because they cluster around

and connect to the nasal cavity

Sutures

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Immovable, interlocking joints of flat bones of skull

Irregular, saw-toothed appearance Largest 4 skull sutures: where bones

articulate with parietal bones Coronal Sagittal Squamous Lambdoid

Fontanels

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Unossified remnants of membranes

Present at birth Anterior fontanel

largest Called “soft spots” Ossify by 1 ½ - 2

years

Hyoid bone

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Only bone which does not articulate with any other bone.

Moveable base for the tongue.

Points of attachment for neck muscles that raise and lower the larynx during swallowing.

The Thoracic Cage

Made of bones which connect and protect heart and lungs

Ribs, Costal Cartilage, and Sternum

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Ribs

12 pairs of ribs, each connects to a thoracic vertebrae

First 7 pairs = true ribs; attach directly to sternum

Last 5 pairs = false ribs; indirect or no attachment; last two are floating (no sternal attachment)

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Typical rib

Sternum

Fusion of three bones

1 )Manubrium (top)2 )Body (middle)3 )Xiphoid Process

(bottom)Location for rib

attachmentSurrounded by

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The Vertebral Column

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Adult: 24 vertebrae Inferior 9 have fused

forming

The sacrum (5)

The coccyx (4)

Structure of a typical vertebra

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Cervical Vertebrae

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Smallest

Transverse processes have foramina (transverse foramen)

Spinous process bifid (forked) except for C7

Thoracic Vertebrae T1-T12

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Heart shaped body

The spinous process are long, sharp and directed downwards

Lumbar Vertebrae L1-L5

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Massive blocklike bodies

The spinous processes short, thick, broad and directed backward

Sacrum and Coccyx

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