Skeletal System

Bone Functions 1.support: hard framework that supports body and holds soft organs (lower limbs, ribs) 2.Protection: skull, vertebrae, ribs 3.Movement: skeletal muscles attached to bones by tendons. 4.Mineral storage: calcium, phosphate 5.Blood cell formation(RBC & WBC): “hematopoiesis” occurs in the bone marrow of certain bones.

Classification of Bone: 2 types of Osseous Tissue 1.Compact bone (dense): smooth 2. Spongy bone (cancellous): composed of flat pieces of bone with open spaces. These spaces are filled with red or yellow bone marrow.

Classification of Bones: Shape 1. Long Bones: shaft with 2 ends that are longer than they are wide (ex: humerus, femur). 2. Short bones: cube-like (ex: wrist and ankle). Sesmoid bone: type of short bone (patella) 3. Flat bones: thin, flattened, and unusually curved (ex: breastbone, ribs, most skull bones) 4. Irregular bones: complicated shapes (ex: vertebrae, hip bones)

Bone Shape

Gross Anatomy of a Long Bone

Diaphysis: bone shaft that surrounds a central medullary cavity (marrow). Epiphysis: bone ends that are covered with articular cartilage (cushions and absorbs stress). Epiphyseal Line: between the diaphysis and epiphysis (remnant of the growth plate). The growth plate is a region of hyaline cartilage that grows during childhood to lengthen the bone.

Gross Anatomy of a Long Bone Continued….. Periosteum: double layered membrane that covers the outer surface of the bone. – the outer layer is dense irregular CT – inner layer is composed of bone forming cells Osteoblasts (bone forming cells) Osteoclasts (bone destroying cells) – Rich in nerve fibers and blood vessels. – Provides an anchoring point for tendons and ligaments

Bone Marrow Red Bone Marrow: – Infants: all medullary cavities and spongy bone are filled with red bone marrow – Adult: little red marrow present in bones Mainly sternum and hip bones Yellow Bone Marrow – Adults: fat containing cavities but can convert to red if there is a homeostatic imbalance (anemia).

Long Bone Anatomy: a Closer Look

Bone Surface: bumps, holes, ridges Called Bone Markings (see page 119) Sites for attachment – Muscle – Tendons and Ligament Help to form joints The point where bones meet Canals for blood vessels and nerves to pass

Types of Fractures 1. Simple (closed): bone breaks cleanly but does not penetrate skin. 2. Compound (open): broken ends of bone protruding through skin.

Types of Fractures 3. Comminuted: bone breaks into many fragments Common in elderly people whose bones are brittle 4. Compression: bone is crushed Common in people with osteoporosis 5. Depressed: bone is pressed inward Typical of a skull fracture

Types of Fractures 6. Impacted: broken bone ends are forced into each other (ex: arm breaks a fall) 7. Spiral: ragged break occurs when excessive twisting forces are applied to a bone Common sport injury 8. Greenstick: bone breaks incompletely, much in the way a green twig breaks Common in young children

Name that Fracture!

Homeostatic Imbalances Osteoporosis: when the bone reabsorption outpaces bone deposit. – Bone mass decreases – become porous and lighter – Spine is most vulnerable – Compression fractures are common – Femur neck is also vulnerable (broken hip)

Osteoporosis Prevention: – get enough calcium as bones are developing (up to age 35). – drink fluorinated water (hardens bones) – exercise during youth and throughout life (increase mass) Statistic: ONLY 35% of adults consume the recommended daily allowance of calcium

Negative Feedback

Osteomalacia (adults) and Rickets (children) Calcium or vitamin D deficiency causing soft bones Bowed legs and deformed pelvis Growth plates can’t be calcified and the end of long bones become widened.

Paget’s Disease Excessive and abnormal bone formation leaves bones soft and weak. Rarely seen before age 40 Unknown cause (viral?)

The end or is it the beginning?