Skeletal System

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

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

Cartilage Hyaline Elastic Fibrocartilage

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 cartilage

Costal cartilage

Respiratory cartilage

Nasal cartilage

Elastic cartilage - Forms external ear - Forms epiglottis

Elastic cartilage

Fibrocartilage Withstands heavy pressure & tensile forces - Intervertebral disks - Knees and elbows

Fibrocartilage

Bone 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 bone Long bones Short bones Sesamoid bones Flat bones Irregular bones

Long 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 bones Roughly cuboidal in shape

Sesamoid bones form within a tendon e.g. patella

Flat bones Thin, flattened, and slightly curved Diploe – spongy bone found between compact bone layers

Diploe

Irregular bones complicated shapes e.g. vertebrae, pelvis

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

Osseous 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 bone

Lamellar 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 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 = Trabecular bone

Chemical 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 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 ligament attachment - Tuberosity – large rounded projection - Crest – narrow prominent ridge - Trochanter – large, blunt, irregularly shaped process (Only found on the femur)

Sites of muscle and ligament attachment -Tubercle – small rounded projection or process - Epicondyle – raised area above a condyle - Spine – sharp, slender, often pointed projection - Process – any bony prominence

Tuberosity

Crest

Trochanter

Tubercle

Epicondyle

Spine

Process

Projections that help form joints - Head – bony expansion carried on a narrow neck - Condyle – rounded articular projection - Ramus – arm like bar of bone

Head

Condyle

Ramus

Depressions and openings allowing blood vessels and nerve 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 allowing blood vessels and nerve fibers to pass - Fissure – narrow, slit like opening - Foramen – round or oval opening through a bone

Meatus

Sinus

Fossa

Fissure

Foramen

Hormone Control of Bone Remodeling 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 Imbalance Fracture – a break in the bone Open fracture – bone penetrates through the skin Closed fracture – bone does not penetrate skin

Depressed Fracture

Compression Fracture

Fracture 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 - Mandible

Fracture healing 1.Hematoma formation 2.Fibrocartilaginous callus formation 3.Bony callus formation 4.Bone remodeling