Skeletal System

Function of the Skeletal System Support- framework that supports body and cradles its soft organs Protection- for delicate organs, heart, lungs, brain Movement- bones act as levers for muscles Mineral storage- calcium & phosphate Blood cell formation- hematopoiesis in flat bones

Types of Bones Long Bones- metacarples, metatarsals, phelangies, humerus, ulna, radius, tibia, fibula Short Bones- carpals, tarsals Flat Bones- rib, scapula, skull, sternum Irregular Bones- vertebrae, some facial bones Sesamoid- patella

Bone Classification

Accessory Structures Tendon: connects muscles to bones Ligaments: connect bone to bone

Anatomy of a Long Bone spongy bone Proximal compact bone epiphysis Endosteum diaphysis epiphyseal line yellow marrow Sharpey’s fibers Distal epiphysis periosteum hyaline cartilage

Structure of Bones Outside – has layer of fibrous connective tissue that helps rebuild if broken called periosteum Ends – called epiphysis. Cartilage for cushion-spongy bone-red marrow-RBC Shaft – called diaphysis. Ca / P – makes it hard, collagen makes it flexible/ compact bone / yellow marrow-fat

Red blood cells, platelets and most white blood cells arise in red marrow . * some white blood cells develop in yellow marrow. The color of yellow marrow is due to the much higher number of fat cells. Both types of bone marrow contain numerous blood vessels and capillaries. At birth, all bone marrow is red. With age, more and more of it is converted to the yellow type.

Adults have on average about 2. 6kg (5 Adults have on average about 2.6kg (5.7 lbs) of bone marrow, with about half of it being red. Red marrow is found mainly in the flat bones, and in the spongy bone at the proximal ends of the long bones called femur and humerus. In cases of severe blood loss, the body can convert yellow marrow back to red marrow in order to increase blood cell production.

Axial Skeleton The bones that extend through the center of the body.

Appendicular Skeleton The bones of your appendages and the bones that connect them to the axial skeleton.

Why do skull bones start out separate and unfused? Fetal Skull Why do skull bones start out separate and unfused?

Adult skulls have all the skull plates fused together

Sinal Cavities Frontal Sinus Ethmoid Sinus Sphenoid Sinus Maxillary Sinus Warm and moisten air Lighten the skull Enhance voice resonance

The Vertebral Column Cervical Vertebrae (7) Thoracic Vertebrae (12) Axial Skeleton The Vertebral Column Cervical Vertebrae (7) Thoracic Vertebrae (12) Lumbar Vertebrae (5) Sacrum Coccyx

Vertebrae in each region are shaped different to accommodate different ranges of motion. More movements happening at neck and head than lower in back

Sacrum & Coccyx Axial Skeleton The sacrum contains Haversian Canals. Haversian canals are holes in the bone that both blood vessels and nerves will exit the vertebral column from.

The Thoracic Cage Sternum True Ribs (7) False Ribs (3) Axial Skeleton The Thoracic Cage Sternum True Ribs (7) False Ribs (3) Floating Ribs (2)

Bones of the Pectoral Girdle Appendicular Skeleton Bones of the Pectoral Girdle

The Upper Limb (Forelimb) Appendicular Skeleton The Upper Limb (Forelimb) Humerus Ulna Radius Carpals Metacarpals Phalanges

Humerus

Ulna & Radius

Hand Bones

Appendicular Skeleton Pelvis

Appendicular Skeleton The Lower Limb (Legs) Femur Patella Tibia Fibula Tarsals Metatarsals Phalanges

Femur

Patella

Tibia & Fibula

Foot phelangies metatarsals tarsals tarsals metatarsals phelangies

Types of Joints Hinge Joint

Ball and Socket Joint

Fibrous Joints Immovable Joints suture pubis symphisis

Slightly Movable Joint Cartilagenous Joints Slightly Movable Joint

275 bones 12 weeks (6-9 inches long) Fetal Skeleton 275 bones 12 weeks (6-9 inches long)

bone cartilage calcified cartilage epiphyseal line epiphyseal plate Fetus: 1st 2 months Endochondral Ossification 2o ossification center bone cartilage calcified cartilage Just before birth epiphyseal line epiphyseal plate Childhood Adult

Broken bones Can heal on their own cause they are living cells. Once healed, usually stronger

Bone cells that aid in remodeling Osteoblast Builds new bone Mature bone cell Osteocyte OsteoblastsOsteoblasts are responsible for building new bone and lie at the centre of bone physiology. Their functions include the synthesis of collagen and the control of mineralisation. OsteoclastsOsteoclasts are specialised cells that resorb bone. They work by sealing off an area of bone surface then, when activated, they pump out hydrogen ions to produce a very acid environment, which dissolves the hydroxyapatite. OsteocytesBone adapts to applied forces by growing stronger in order to withstand them; it is known that exercise can help to improve bone strength. Osteocytes are thought to be part of the cellular feed-back mechanism which directs bone to form in the places where it is most needed. They lie within mineralised bone and it is thought that they may detect mechanical deformation and mediate the response of the osteoblasts. Osteoclast Eats bone

Repair of Fractures hematoma callus bony callus bone remodeling

Types of bone breaks Stress factures: minute breaks in bone caused by constant overuse. (Happens a lot in the feet) Break is hard to see on X-ray but becomes worse if not treated quickly.

Diseases of the Skeletal System: Osteoporosis- bone reabsorption outpaces bone deposit; bones become lighter and fracture easier Factors: age, gender (more in women) estrogen and testosterone decrease insufficient exercise (or too much) diet poor in Ca++ and protein abnormal vitamin D receptors smoking

Osteoporosis 29 40 84 92