SKELETAL SYSTEM

Prepared by

Dr.Vindya Rajakaruna M.B.B.S. (COLOMBO)

Done by

Dr.Ishara Maduka M.B.B.S.(COLOMBO)

• Composed of the body’s bones and associated ligaments, tendons, and cartilages.

• There are 206 named bones in the human body.

Functions:1. Support

• The bones of the legs, pelvic girdle, and vertebral column support the weight of the erect body.

• The mandible (jawbone) supports the teeth.

• Other bones support various organs and tissues.

2.Protection • The bones of the skull protect the brain.• Ribs and sternum (breastbone) protect

the lungs and heart.• Vertebrae protect the spinal cord

3. Movement • Skeletal muscles use the bones as levers

to move the body.

3. Reservoir for minerals and adipose tissue• 99% of the body’s calcium is stored in

bone.• 85% of the body’s phosphorous is stored

in bone.• Adipose tissue is found in the marrow of

certain bones4. Hematopoiesis

• Blood cell formation.• All blood cells are made in the marrow of

certain bones

Bone Classification

Axial skeleton• Forms long axis of the body.• Includes the bones of the skull,

vertebral column, and rib cage.• These bones are involved in

protection, support, and carrying other body parts.

Appendicular skeleton• Bones of upper & lower limbs and the

girdles (shoulder bones and hip bones) that attach them to the axial skeleton.

• Involved in locomotion and manipulation of the environment.

Bone Classification

1. Long Bones • Much longer than they are wide.• All bones of the limbs except for the

patella (kneecap), and the bones of the wrist and ankle.

• Consists of a shaft plus 2 expanded ends.• Your finger bones are long bones even

though they’re very short

2. Short Bones• Roughly cube shaped.• Bones of the wrist and the ankle.

3. Flat Bones• Thin, flattened, and usually a bit curved.• Scapulae, sternum, (shoulder blades),

ribs and most bones of the skull.

Sternum

4. Irregular Bones• Have weird shapes that fit none of the 3

previous classes.• Vertebrae, hip bones, 2 skull bones

( sphenoid and the ethmoid bones).

Sphenoid Bone

Bone Structure• Bones are organs. • Thus, they’re composed of multiple tissue

types. Bones are composed of:– Bone tissue – Fibrous connective tissue.– Cartilage.– Vascular tissue.– Lymphatic tissue.– Adipose tissue.– Nervous tissue

• All bones consist of a dense, solid outer layer known as compact bone and an inner layer of spongy bone – a honeycomb of flat, needle-like projections called trabeculae.

• The periosteum is a fibrous sheath that covers bones. It contains the blood vessels and nerves that provide nourishment and sensation to the bone.

• A thin layer of connective tissue that lines the walls of the bone marrow cavities and haversian canals of compact bone and covers the trabeculae of cancellous bone.

• Endosteum has both osteogenic and hematopoietic potencies and, like the periosteum, takes an active part in the healing of fractures.

Bone Structure• Bone tissue is a type of connective tissue, so it

must consist of cells plus a significant amount of extracellular matrix.

• Bone cells:1. Osteoblasts

• Bone-building cells.• Synthesize and secrete collagen fibers

and other organic components of bone matrix.

• Initiate the process of calcification.• Found in both the periosteum and the

endosteum

The blue arrows indicate the osteoblasts. The yellow arrows indicate the bone matrix they’ve just secreted.

2. Osteocytes• Mature bone cells.• Osteoblasts that have become trapped by

the secretion of matrix.• No longer secrete matrix.• Responsible for maintaining the bone

tissue.

The osteocyte is “trapped” within the pink matrix

3.Osteoclasts– Huge cells derived from the fusion of as many

as 50 monocytes (a type of white blood cell).– Cells that digest bone matrix – this process is

called bone resorption and is part of normal bone growth, development, maintenance, and repair.

– Concentrated in the endosteum.

Bone Matrix:– Consists of organic and inorganic

components.• Organic component consists of several

materials that are secreted by the osteoblasts:

–Collagen fibers and other organic materials

»These (particularly the collagen) provide the bone with resilience and the ability to resist stretching and twisting

• Inorganic component of bone matrix– Consists mainly of 2 salts: calcium phosphate

and calcium hydroxide.– Bone also contains smaller amounts of

magnesium, fluoride, and sodium.– These minerals give bone its characteristic

hardness and the ability to resist compression.

Long Bone Structure• Shaft plus 2 expanded ends.• Shaft is known as the

diaphysis.– Consists of a thick collar of

compact bone surrounding a central marrow cavity• In adults, the marrow

cavity contains fat - yellow bone marrow

• Expanded ends are epiphyses– Thin layer of compact bone covering an

interior of spongy bone.– Joint surface of each epiphysis is covered

with a type of hyaline cartilage known as articular cartilage. It cushions the bone ends and reduces friction during movement.

• The external surface of the entire bone except for the joint surfaces of the epiphyses is covered by a double-layered membrane known as the periosteum

• Periosteum is richly supplied with nerve fibers, lymphatic vessels and blood vessels.

• These enter the bone of the shaft via a nutrient foramen.

• Periosteum is connected to the bone matrix via strong strands of collagen

• Internal bone surfaces are covered with a delicate connective tissue membrane known as the endosteum.

• Covers the trabeculae of spongy bone in the marrow cavities and lines the canals that pass through compact bone.

• Contains both osteoblasts and osteoclasts.

Bone Marrow

• soft tissue occupying the medullary cavity of a long bone, the spaces amid the trabeculae of spongy bone, and the larger haversian canals.

• There are 2 main types: red & yellow.• Red bone marrow = blood cell forming

tissue = hematopoietic tissue

• Red bone marrow looks like blood but with a thicker consistency.

• It consists of a delicate mesh of reticular tissue saturated with immature red blood cells and scattered adipocytes

• Yellow marrow do not produce blood, although in the event of severe or chronic anemia, it can transform into red marrow

Microscopic Structure of Compact Bone• Consists of multiple cylindrical structural

units known as osteons or haversian systems

• Haversian systems are arranged parallel to one another along the long axis of a compact bone.

Osteons/ Haversian systems

• Each osteon consists of a single central canal, known as a haversian canal, surrounded by concentric layers of calcified bone matrix.

• Haversian canals allow the passage of blood vessels, lymphatic vessels, and nerve fibers.

• Each of the concentric matrix “tubes” that surrounds a haversian canal is known as a lamella.

• All the collagen fibers in a particular lamella run in a single direction, while collagen fibers in adjacent lamellae will run in the opposite direction. This allows bone to better withstand twisting forces

• Running perpendicular to the haversian canals are Volkmann’s canals.

• They connect the blood and nerve supply in the periosteum to those in the haversian canals and the medullary cavity.

• Spider-shaped osteocytes occupy small cavities known as lacunae at the junctions of the lamellae.

• Hairlike canals called canaliculi connect the lacunae to each other and to the central canal.

• Canaliculi allow the osteocytes to exchange nutrients, wastes, and chemical signals to each other via intercellular connections

Microscopic Structure of Spongy Bone

• Appears poorly organized compared to compact bone.

• Lacks osteons.• Trabeculae align along positions of stress

and exhibit extensive cross-bracing.• Trabeculae are a few cell layers thick and

contain irregularly arranged lamellae and osteocytes interconnected by canaliculi

SKELETON

Axial skeleton• skull (cranium and facial bones)• hyoid bone (anchors tongue and muscles

associated with swallowing)• vertebral column (vertebrae and disks)• thoracic cage (ribs and sternum)

Appendicular skeleton• pectoral girdle (clavicles and scapulae)• upper limbs (arms)• pelvic girdle (sacrum, coccyx)• lower limbs (legs)

22 bones in skull6 in middle ears1 hyoid bone26 in vertebral column25 in thoracic cage

4 in pectoral girdle60 in upper limbs60 in lower limbs2 in pelvic girdle

206 bones in all

Bone Surface Markings• Foramen = opening (arteries, nerves)• Fossa = shallow depression• Sulcus = shallow groove (artery or nerve)• Canal = longer, tubelike opening• Fissure = narrow, cleftlike opening• Notch = indentation at the end of a bone• Meatus = type of canal• Condyle = large, round protuberance, attachment of muscles• Epicondyle = above or upon a condyle• Facet = smooth flat articular surface• Trochanter = very large projection• Tuberosity = large, rounded, roughened projection• Tubercle = rounded eminence/elevation• Crest = roughened border or ridge• Spine = sharply pointed projection

Axial skeleton

The skull

• 8 sutured bones in cranium• Facial bones: 13 sutured bones, 1

mandible

• Cranium - encases brain - attachments for muscles - sinuses

Cranial Bones

• Parietal (2) • Temporal (2) • Frontal (1) • Occipital (1) • Sphenoid (1)• Ethmoid (1)

Sutures• Sutures are the tight connections between

skull bones• In the adult skull , the skull bones are

unable to move or separate due to this tight connections

• In infant skull this sutures are not well formed and the skull bones are mobile which facilitates the delivery of the baby

• Coronal suture – this separates the frontal from the parietal bones

• Sagittal suture - this separates the two parietal bones in the mid line

• Lambdoid suture - this separates the occipital bone the two parietal bones and the temporal bone

• Squamosal suture - this separates the temporal from the parietal bones

Fontanelles

• These are seen in new borns• At birth the junction between skull bones

covered with a membrane • This allows the expansion and growth of

the brain• Later they become ossified ( bone

formation)

Lateral view

Anterior view

Inferior view

• Warm and moisten air• Lighten the skull• Enhance voice resonance

Frontal Sinus

Ethmoid SinusSphenoid Sinus

Maxillary Sinus

Sinuses

Frontal bone– Forms the forehead– Roof of the orbit– articulates with parietal, sphenoid, lacrimal,

nasal, ethmoid, zygomatic and maxilla– Contain 2 air filled cavities. ( frontal sinuses

Parietal bones– Part of the superior and lateral surfaces of the

cranium– -articulate with each other – sagittal suture– -articulate with occipital, frontal,– temporal and sphenoid bones

Temporal bone– Forms wall of jugular foramen– Associated with ear canal– Anterior portion, fan-shaped - zygomatic process -forms cranial portion of the TMJ joint -inferior to zygo. process – mandibular

fossa (mandibular condyle)- inferior aspect – mastoid process- inferior and medial to the MP – styloid

process

Occipital bone• Part of the base of the skull• articulates with parietal, temporal and

sphenoid• Surrounds the foramen magnum• Occipital condyles articulate with Atlas

Sphenoid bone

– Contributes to floor of cranium– articulates with the frontal, ethmoid, temporal zygomatic, parietal maxillary, palatine, vomer

& occipital bones– Bridges cranial and facial bones– Optic canal allows passage of optic nerve

Ethmoid bone

– Irregularly shaped bone– Forms part of orbital wall– Forms roof of nasal cavity– articulates with: frontal, sphenoid, lacrimal

and maxillary bones– connects with the vomer

Facial Bones

Nasal (2) Maxillae (2) Zygomatic (2)Mandible (1) Lacrimal (2) Palatine (2)

Inferior nasal conchae (2) Vomer (1)

Maxillae

– Paired bone– Largest of facial bones– Form upper jaw– contains the maxillary sinuses– zygomatic process: articulates with

zygomatic bone– Teeth are fixed to this

Zygomatic Bones - Lateral wall of orbit form along with

sphenoid - Part of zygomatic arch form along with part

of temporal

Palatine bones– Small, L-shaped– link between maxilla and sphenoid– Form posterior portion of hard palate– Contribute to floor of orbit

Lacrimal bones

– Smallest bones in skull– Forms nasolacrimal groove leading to

nasolacrimal canal– Delivers tears to nasal cavity

Vomer

– Forms posterior part of nasal septum– Forms inferior portion of nasal septum– Articulates with maxillae and palatines

Nasal bones– Paired bones – forms the bridge– Articulate with frontal bone

Mandible• lower jaw carries teeth• only freely movable bone of the skull• moving articulations with temporal bone

Orbital complex– Bony recess that holds the eye– Seven bones

• Frontal bone• Lacrimal bones• Palatine bones• Zygomatic bones• Ethmoid• Sphenoid• Maxillae

Bones forming the walls of the orbit

• Roof - frontal lesser wing of sphenoid• Medial wall – maxilla lacrimal ethmoid sphenoid• Floor – maxilla zygomatic palatine

• Lateral wall - greater wing of sphenoid zygomatic

Cranial Fossae

• Depressions in cranial floor• Anterior cranial fossa

– Frontal bone, ethmoid, lesser wings of sphenoid

• Middle cranial fossa– Sphenoid, temporal bones, parietal bones

• Posterior cranial fossa– Occipital bone, temporal bones, parietal

bones

Vertebral column

• Cervical vertebrae (7) • Thoracic vertebrae (12) • Lumbar vertebrae (5) • Sacrum (5 pieces) • Coccyx (4 pieces) • Total number is 33

Typical Vertebrae• Body

– weight bearing• Vertebral arch

– pedicles– laminae

• Vertebral foramen• Seven processes

– 2 transverse– 1 spinous – 4 articular

• Vertebral notches

• Vertebral body lies anteriorly• Vertebral foramen lies posterior to

vertebral body , which allows spinal cord to pass

• Vertebral arch a curved bony structure which surrounds the foramen

• Spinous process lies posteriorly• Transverse processes lie lateraly

Atlas (C1)• ring of bone, superior facets for occipital

condyles– nodding movement at atlanto-occipital joint

signifies “yes”

Axis(C2)• dens or odontoid process is body of

atlas– movement at atlanto-axial joint signifies “no”

Cervical Vertebrae (C3-C7)

• Smaller bodies• Larger spinal canal• Transverse processes

– shorter– transverse foramen for vertebral artery

• Spinous processes of C2 to C6 often bifid

Thoracic Vertebrae(T1-T12)

• Larger and stronger bodies which carry the shape of the heart

• Longer transverse & spinous processes• Facets on body for head of rib• Facets on transverse processes (T1-T10)

for tubercle of rib

Lumbar Vertebrae

• Strongest & largest for weight baring• Body takes the shape of kidney• Short thick spinous & transverse

processes– back musculature

Sacrum and Coccyx

• Sacrum – Triangular shaped bone formed by united 5 sacral bodies

• Coccyx – Most inferior part of the vertebral column and it is made up of 4 united vertebral bodies

Spinal Canal

• Spinal canal is all vertebral foramen together

• Carries the spinal cord

Intervertebral Foramen

• These are small fenestrations on the lateral sides of the vertebral column

• These lie in between two vertebrae• The nerves which arises from the spinal

cord exit from there

The intervertebral disc

• The intervertebral disc lies between two vertebrae

• Made up of fibrous cartilage and a jelly like substance

• Function is to reduce friction between the vertebral bodies and neutralize mechanical shock

Thoracic cage

• The thoracic cage is formed by;Anteriorly – Sternum and the costal

cartilagesPosteriorly - Thoracic vertebraeSuperiorly – Thoracic inlet Inferiorly – DiaphragmLaterally – Ribs ( Rib cage)

Sternum

• A flat bone which forms the anterior part of the thoracic cage

• Consist of 3 parts - Manubrium - Body of the sternum - Xiphoid process

• Between the manubrium and the body of the sternum lies the sternal angle ( Angle of Louis)

• The second rib is attached to the sternum at the Angle of Louis

Ribs

• Thoracic cage is formed by twelve pairs of ribs

• All ribs posteriorly attached to the vertebrae

• Anteriorly upper 7 ribs directly attached to the sternum via costal cartilages

• 8th, 9th and 10th ribs are attached to the cartilage of the rib above ( False ribs)

• 11th and 12th are not attached to the sternum ( Floating ribs)

Costal Groove• Each rib has a costal groove in it’s lower

inner surface • The intercostal vein, artery and the nerve

lies in this groove

Intercostal space

• This space carries the intercostal vessels and nerves and is filled by the inercostal muscles

• The function of inercostal muscles are to facilitate inspiration and expiration

Function of the thoracic cage

• Provide protection for the internal organs – heart, lungs

• Facilitates the expansion of the lung during inspiration

Shoulder Girdle

• Formed by the Clavicle and the Scapula

The scapula• Is a triangular shaped bone which lies on

the posterior surface of the rib cage• The Acromion process projects lateraly and

attached with the clavicle to form acromio-clavicular joint

• The Glenoid cavity is a shallow cavity which attached with the head of the humerus forming shoulder joint (bowel and socket joint)

The Clavicle

• A ‘S’ shaped bone attached medially to the sternum by sterno-clavicular joint

• Laterally attached to the scapular by acromio-clavicular joint

• Commonly get fractures

Upper limb

• Arm – Humerus• Forearm – Ulnar , Radius• Wrist – 8 Carpal bones• Hand – Metacarpal bones• Fingers – Phalanges

The bones of the upper limb

Humerus

• Longest bone in the upper limb• Head of the humerus lies in the proximal

end and articulates with the glenoid cavity to form shoulder joint

• Distal end articulates with ulnar and radius forming the elbow joint

Ulnar

• Longest bone in the forearm• Lies medially• Proximally form elbow joint with the

humerus• Distally form wrist joint with carpal bones

Radius

• Shorter than ulnar• Lies lateral to ulnar• Proximally form elbow joint with humerus• Distally form wrist joint with carpal bones

Carpal bones

• Lie in 2 rows at wrist• Proximal row – Scaphoid, Lunate,

Triquatral, Pisiform• Distal row – Trapezium, Trapezoid,

Capitate, Hamate

Metacarpal bones

• 5 Metacarpal bones form the palm of the hand

Phalanges• Thumb – 2 Phalanges (Proximal, Distal)• Other 4 fingers – 3 Phalanges ( Proximal,

Middle, Distal)

Pelvic Girdle

• The pelvic girdle is formed by the bony pelvis

• The bony pelvis is made from the right and left pelvic bones which form the lateral wall, the pubic symphysis which is the junction between the two pelvic bones anteriorly and the sacrum which lie posteriorly

Pelvic bones

• Consist of 3 irregular flat bones in each which have fused completely

• Iliac bone – A large fan shaped bone. Upper edge is the iliac crest which extend from anterior superior iliac spine to posterior superior iliac spine

• Ischial bone – Irregular bone, has an ischial spine which project inward.

Ischial tuberosity lies at the most inferior edge

• Pubic bone – Consist of the body of the pubis, superior and inferior pubic rami.

The two bodies of the pubis of each pubic bone join anteriorly at the pubic symphasis

The differences between the male and the female pelvis

Female• Light and thin• Oval shape• Large pelvic outlet• Wide pubic angle• Wide sacrum

Male• Thick and heavy• Heart shape• Small pelvic outlet• Narrow pubic angle• Narrow sacrum

Lower Limb• Thigh – Femur• Leg – Tibia , Fibula• Knee – Patella• Ankle – 7 Small bones• Foot – 5 Metatarsals• Toes – Phalanges

Femur

• Largest and the strongest bone• Head of the femur joints with the

acetabulum of the pelvic bone and forms Hip joint

• Other important parts include the neck of the femur, shaft and the medial and lateral condyle which form knee joint with the combination of tibia

Patella• Small triangular bone which form the knee

cap

Tibia• Lie in the medial side of the leg• Upper end articulate with the femur to form

knee joint• Lower end of the shaft has the medial

malleolus on its medial side

Fibula

• Smaller than tibia• Lies laterally• Lower end has the lateral malleolus on its

lateral side

Ankle Bones

• The 7 ankle bones are the talus, calcaneus (heel bone), navicular, cuboid, internal cuneiform, middle cuneiform, and external cuneiform

• Talus joins with tibia and fibula forming the ankle joint

Questions

1. What is Fracture neck of femur?2. What is osteomyelitis?3. What is osteoporosis?4. What is infective arthritis?

Types of movement and examples flexion- move lower leg toward upperextension- straightening the leg

abduction- moving leg away from bodyadduction- movong leg toward the body

rotation- around its axissupination- rotation of arm to palm-up positionpronation- palm down

circumduction- swinging arms in circles

inversion- turning foot so sole is inwardeversion- sole is out

Elevation and depression- raising body part upor down