Skeletal SystemSkeletal System

ComponentsComponents

    

- Cartilage - Bone - Joints - Ligaments (bone to bone) - Tendons (muscle to bone)

FunctionsFunctions

        - Support - Movement - Protection - Mineral storage - Blood cell synthesis -

hematopoiesis

CartilageCartilage

• Hyaline• Elastic• Fibrocartilage

Hyaline cartilage Hyaline cartilage - Articular cartilage – covers ends of bones

and moveable joints

- Costal cartilage – attach ribs to the sternum

- Respiratory cartilage – forms respiratory passages and larynx

- Nasal cartilage – forms external nose

Articular cartilageArticular cartilage

Costal cartilageCostal cartilage

Respiratory cartilageRespiratory cartilage

Nasal cartilageNasal cartilage

Elastic cartilageElastic cartilage

- Forms external ear

- Forms epiglottis

Elastic cartilageElastic cartilage

FibrocartilageFibrocartilage

Withstands heavy pressure & tensile forces

- Intervertebral disks - Knees and elbows

FibrocartilageFibrocartilage

BoneBone

• Cell, tissue, organ

• Skeleton – Greek for dried up body• Composed of 206 bones 1.  Axial skeleton – 80 bones 2.  Appendicular skeleton – 126 bones

Classification of boneClassification of bone

• Long bones

• Short bones • Sesamoid bones • Flat bones • Irregular bones

Long bonesLong bones - Diaphysis – shaft

- Epiphysis – ends of bone; contain red marrow

- Medullary cavity – contains yellow marrow

- Epiphyseal plate – found between diaphysis and epiphysis; long bone growth

Short bonesShort bones

• Roughly cuboidal in shape

Sesamoid bones Sesamoid bones

form within a tendon e.g. patella

Flat bonesFlat bones

Thin, flattened, and slightly curved

Diploe – spongy bone found between compact bone layers

DiploeDiploe

Irregular bones Irregular bones

• complicated shapes e.g. vertebrae, pelvis

Bone cellsBone cells • Osteoclast – cells which dissolve bone

(puts calcium into the blood for muscular contraction, nerve transmission, blood clotting, etc…)

• Osteoblast – cells which build bone by removing calcium and phosphates from the blood in the presence of the enzyme alkaline phosphatase secreted by osteoblasts

• Osteocyte – mature cells found within compact bone (living bone)

Bone remodelingBone remodeling

Occurs under the periosteum (White, double layered membrane) which is held to bone by Sharpey’s fibers

Osseous tissueOsseous tissue

• Compact bone (Lamellar bone) – Dense and hard; found on the external surfaces of bones

• Spongy bone - contain trabeculae (little beams) which align along lines of stress; and open spaces filled with red or yellow marrow

Compact bone = Lamellar Compact bone = Lamellar bonebone

Lamellar boneLamellar bone Osteon or Haversian System – structural

unit of compact bone (cylindrical in shape) which bear weight

- Lamella – each ring of an osteon

- Haversian canal – contains blood vessels & nerve fibers which travel vertically in bone

- Volkmann’s canal – contain blood vessels and nerve fibers which travel horizontally in bone

Lamellar boneLamellar bone- Lacuna – spaces found in compact bone

occupied by osteocytes

- Canaliculi – lateral canals which connect lacunae which allow osteocytes to diffuse nutrients and wastes into or out of bone tissue through gap junctions

Spongy bone = Spongy bone = Trabecular Trabecular bonebone

Chemical compositionChemical composition - Hydroxyapatites 60-70% of bone weight mineral salts; mainly calcium phosphates

*source of stiffness and compressive strength - Collagen fibers ~ 10% of bone weight made up of glycoproteins *source of flexibility & tensile strength Aging causes decrease in collagen & an increase in fragility - Water ~ 25-30% important contributor to bone strength

Bone markingsBone markings

Sites of tendon and ligament attachment

Projections that help form joints

Depressions and openings allowing blood vessels and nerve fibers to pass

Sites of muscle and Sites of muscle and ligament attachmentligament attachment

- Tuberosity – large rounded projection

- Crest – narrow prominent ridge

- Trochanter – large, blunt, irregularly shaped process (Only found on the femur)

Sites of muscle and Sites of muscle and ligament attachmentligament attachment

- Tubercle – small rounded projection or process

- Epicondyle – raised area above a condyle

- Spine – sharp, slender, often pointed projection

- Process – any bony prominence

TuberosityTuberosity

CrestCrest

TrochanterTrochanter

TubercleTubercle

EpicondyleEpicondyle

SpineSpine

ProcessProcess

Projections that help form Projections that help form jointsjoints

- Head – bony expansion carried on a narrow neck

- Condyle – rounded articular projection

- Ramus – arm like bar of bone

HeadHead

CondyleCondyle

RamusRamus

Depressions and openings Depressions and openings allowing blood vessels and allowing blood vessels and

nerve fibers to passnerve fibers to pass - Meatus – canal like passage way

- Sinus – Cavity within bone filled with air and lined with mucous membrane

- Fossa – shallow basin like depression in bone

Depressions and openings Depressions and openings allowing blood vessels and allowing blood vessels and

nerve fibers to passnerve fibers to pass - Fissure – narrow, slit like opening

- Foramen – round or oval opening through a bone

MeatusMeatus

SinusSinus

FossaFossa

FissureFissure

ForamenForamen

Hormone Control of Bone Hormone Control of Bone RemodelingRemodeling

• PTH (Parathyroid hormone) is released by parathyroid glands when serum calcium levels are low which increase osteoclast activity.

• Calcitonin is released by the thyroid gland when serum calcium levels are too high which stimulate osteoblast activity (causes them to release alkaline phosphatase)

Calcitonin

PTH

Homeostatic ImbalanceHomeostatic Imbalance

Fracture – a break in the bone

Open fracture – bone penetrates through the skin

Closed fracture – bone does not penetrate skin

Depressed FractureDepressed Fracture

Compression FractureCompression Fracture

Fracture treatmentFracture treatment

• Closed reduction – When a physician pulls on bone to realign bone ends

• Open reduction – When a physician surgically inserts pins or wires to realign bones

Open Reduction - Open Reduction - MandibleMandible

Fracture healingFracture healing

1. Hematoma formation2. Fibrocartilaginous callus

formation3. Bony callus formation4. Bone remodeling