SKELETAL SYSTEM

The skeletal system is formed of bones and cartilagesThe bones are connected by joints to form the skeleton.

Functions of bones• They form the skeleton which gives the body shape and form

• They provide attachment for muscles & ligaments• They allow movements of the body• They provide protection for vital organs• They provide storage places for calcium salts• Production of blood cells in the red bone marrow

Types of Bone (according to structure)

• The bone is a type of connective tissue• It is hard because of its high content of calcium salts

• There are 2 types of bone tissue:Compact bone: which is dense & hard. It forms the shaft of long bones, and outer shell of other bones.

It consists of cylindrical units of closely packed lamellae (Haversian system)

Cancellous (spongy) bone: a delicate bony meshwork that fills the inside of bones.

Compact

Types of Bones (according to shape)• Long bones: these are longer than wide, and are found in limbs, e.g. humerus.

• Short bones: they are cuboidal in shape, and found in the hand and foot (carpal & tarsal bones)

• Flat bones: thin and flattened, e.g. scapula & skull bones• Irregular bones: they are irregular in shape, e.g. vertebrae• Pneumatic bones: they contain air-filled cavities, e.g. ethmoid bone

• Sesamoid bones: embedded within certain tendons, e.g. patella• Sutural bones: found between the skull sutures

Remember!! Metatarsal & metacarpal bones and phalanges are considered long bones

Flat bone

Long boneShort bones

Long bones

Sutural bones

Pneumatic bone Irregular bonePatella

Sesamoid bone

Features of Long Bones: Long bones consist of a “shaft” and 2 “ends”Shaft (Diaphysis):

• This is the tubular part of the long bone. It is formed of compact bone and contains a central cavity called “medullary” or “bone marrow cavity”.

• The shaft is lined by a membrane called “endosteum” and covered by a vascular membrane called “periosteum”

• The periosteum contains osteoblasts and causes the increase in width of the bones, it is also needed for repair of bone fractures.

Ends (Epiphysis):• These are the expanded ends of the long bone.• They are formed of cancellous bone covered by a thin layer of compact bone.

Note!! the diaphysis is separated from the epiphysis by the “epiphyseal cartilage”The Metaphysis: is the part of the diaphysis adjacent to the epiphyseal line

Shouldergirdle

SKELETON

Axial skeleton:• Skull• Sternum• Ribs• Vertebrae

Appendicular skeleton:• Bones of upper limb & Shoulder girdle• Bones of lower limb & Pelvic girdle

APPENDICULAR SKELETON

Skeleton of the Upper Limb

Shoulder girdle: 2 bones• Clavicle, anteriorly• Scapula, posteriorly

Upper arm, one bone• Humerus

Forearm, 2 bones• Radius, laterally• Ulna, medially

Hand, formed of:• Carpus (8 bones)• Metacarpus (5 bones)• Phalanges (3 in each finger, except the thumb which contains 2 phalanges)

Scapula & HumerusPosterior view

spine acromion

head

Scapula & HumerusAnterior view

Coracoid process

acromion

Greater & lessertuberosities

capitulum trochlea

Rad

ius

Uln

a

head

neck

Styloidprocess

head

Styloidprocess

Radius & Ulna

Wrist & Hand

Carpal bonesMetacarpalbones

P h

a l

a n

g e

s

APPENDICULAR SKELETON

Skeleton of the Lower Limb

Pelvic girdle 1 bone• Hip bone

Thigh 1 bone• Femur

Leg 2 bones• Fibula, laterally• Tibia, medially

Foot formed of:• Tarsus (7 bones)• Metatarsus (5 bones)• Phalanges (3 in each toe, except the big toe which contains 2 phalanges)

Hip bone

I l i u

m

Ischium

Pubis

Acetabulum

Hip bone (lateral view)

Femur (posterior view)

Head

Neck

Greater & lessertrochanters

Femoralcondyles

Tibia & fibulaAnterior view

Foot

Tarsal bones

Metatarsalbones

ph

alang

es

Tibialcondyles

Tib

ia

Fib

ula

Tibialtuberosity

SKULL

The skull is formed of two parts:•Brain box: the upper & posterior part of the skull•Facial skeleton: the anterior part of the skull

The skull is made up of 22 bones• 1 movable bone, the mandible• 21 immovable bones articulating by fibrous joints (sutures)

Single bones of the skull•Frontal bone•Occipital bone•Ethmoid bone•Sphenoid bone•Vomer•Mandible

Paired bones of the skull•Parietal bone•Temporal bone•Maxilla•Zygomatic bone•Nasal bone•Lacrimal bone•Palatine bone•Inferior nasal concha

Norma Frontalis, shows:• Frontal bone• Nasal bones• Maxillae• Zygomatic bones• Mandible

• Orbital openings• Anterior nasal aperture

• Mental foramen

Features of the Skull

Orbit opening

Anterior nasalaperture

Mental foramen

Norma verticalis, shows:• Frontal bone• Parietal bones• Occipital bone• Coronal, sagittal and lambdoid sutures

• Parietal foramen

Frontal bone

Coronal suture

Sagittal suture

Lambdoid suture

Occipital bone

Pariet

al b

one

Parietal foramen

Norma lateralis, shows:• Frontal, Parietal, Temporal, Occipital and Zygomatic bones• Zygomatic arch• Temporal lines & temporal fossa• External auditory meatus

Fron

tal

bone

Parietalbone

Occ

ipital

bone

Temporal bone

Zygomaticbone

Temporal lines

External auditorymeatus

Zygomaticarch

Norma occipitalis, shows:• Occipital bone• Parietal bones• External occipital protuberence & crest• Nuchal lines

Parietal bones

Occipital bone

External occipitalprotuberence

Superior & inferiorNuchal lines

Norma basalis externa, shows:• Alveolar arch• Hard palate• Posterior nasal apertures• Foramina and canals which give passage to structures which enter or leave the skull

• foramen ovale• foramen magnum• carotid canal• jugular foramen

Posterior nasalaperture

Foramenovale

Carotidcanal

Foramenmagnum

Jugularforamen

Hard palate

Alveolar arch

Norma basalis interna, shows• Anterior, middle & posterior cranial fossae• Frontal, ethmoid, sphenoid, temporal & occipital bones• Foramina:

• Foramen rotundum• Foramen ovale• Foramen lacerum• Jugular foramen• Foramen magnum

Frontal bone

Foramen rotundum

Foramen ovale

Foramen lacerum

Temporal bone

Occipital bone

Jugular foramen

Foramenmagnum

Sphenoid bone

Ethmoid bone

Vertebral Column (Spine)

•The vertebral column (spine) consists of:•7 cervical vertebrae•12 thoracic vertebrae•5 lumbar vertebrae•5 sacral vertebrae (fused together to form the sacrum)•4 coccygeal vertebrae (fused together to form the coccyx)

•The vertebral column provides support for the head and trunk•It provides protection for the spinal cord

Basic Structure of a Vertebra• Body: disc shaped and anterior in position• Vertebral arch: a bony ring behind the body. It is formed of 2 pedicles and 2 laminae• Vertebral foramen: the ring bound by the vertebral arch. The vertebral canal is formed by the succession of vertebral foramina

• 7 Processes: They project from the vertebral arch• A Spinous process, projects posteriorly• 2 Transverse processes, one projecting on each side• 2 Superior articular processes projecting up to articulate with the inferior articular processes of the vertebra above.

• 2 Inferior articular processes projecting down to articulate with the superior articular processes of the vertebra below.

Characteristics of Vertebrae

Cervical Thoracic Lumbar

Body Small & oval Heart-shaped with articular demifacets

Large & kidney-shaped

Spinous process

Short & bifid Long & directed down Short & thick

Transverse processes

Show a foramen transversarium

Have articular facets Long & slender

Vertebral foramen

Large & triangular Small & circular Large & circular

Foramentransversarium

Bifid spine

Cervical Vertebra

Thoracic Vertebra

Lumbar Vertebra

1st & 2nd Cervical Vertebrae

Sacrum: It is formed of 5 vertebrae that are fused together

Intervertebral foramina• These are notches in the upper and lower

borders of each pedicle of the vertebral arch

• Adjacent notches from an intervertebral foramen for the passage of spinal nerves

The sternum is composed of 3 fused pieces•manubrium sterni•body •xiphoid process

Sternal angle: is the junction between the manubrium and the body

Sternum & Ribs

• There are 12 pairs of ribs• All the ribs are attached at their posterior ends to the vertebrae.

• Anteriorly:• The upper 7 pairs (true ribs) are attached directly to the sternum by their costal cartilages

• The 8th, 9th, and 10th ribs (false ribs) are attached to the 7th costal cartilage.

• The 11th and 12th ribs (floating ribs) have no anterior attachment.

Ribs

Basic features of ribs• Head: articulates with the thoracic vertebrae• Neck: the constriction just beyond the head• Tubercle: articulates with the transverse process of its corresponding vertebra• Angle: the sharp turn in the rib• Shaft: thin and flattened, its lower border is sharp and shows a groove for intercostal nerves & vessels.