The Skeletal System Chapter 5 Part 1

Function of Bone The main functions of the bone are: 1) Support – they support and anchor soft tissue 2) Protection – protects soft body organs EX: cranium around the brain, vertebrae around the spinal cord 3) Movement – gross and fine motor skills 4) storage – stores minerals 5) blood cell formation – white and red blood cells

Bones are classified by their physical make-up and shape

Two forms of Bone: Bone tissue comes in two forms: A) Compact Bone – dense smooth osseous tissue B) spongy bone – Small needlelike pieces with lots of spaces

Bone Shapes: Long bones – longer than wide (EX: femur, humerus) Short bones – cube shaped (EX: carpals, tarsals) Flat bones – thin, flat, curved bones (EX: sternum, ribs) Irregular bones – don’t fit any category (EX: vertebrae, hip bones) *** know bone markings from table 5.1, pg 138***

LONG SHORT FLAT IRREGULAR

Bone Markings show where muscles, tendons, and ligaments are attached Bone Markings show where muscles, tendons, and ligaments are attached. They also show where blood vessels and nerves are passed through bone. Two categories are projections and depressions. Trick to remembering some bone markings: All terms beginning with “T” are projections, the terms beginning with “F” except facet are depressions

The Structure of Bone The diaphysis makes up the length of the compact bone. It is covered with periosteum (peri- = covering). Periosteum is a strong fibrous connective tissue. The ends of the bones are known as the Epiphysis. It is made up of compact and spongy bone. The articular cartilage lines this surface to reduce friction at the joint. The growth plate (epiphyseal plate) is significantly different in a young person compared to an adult. The lining of the shaft of the bone contains adipose tissue and is called yellow marrow. Infants have red marrow in this area.

Microscopic Anatomy of the Bone Osteocytes are mature bone cells found in tiny cavities called lacunae. This cavity or lacunae is arranged in concentric circles called lamellae around each Haversian canal. These canals carry blood and nerve to all areas of the bone.

Microscopic Anatomy of the Bone The Canaliculi transports nutrients throughout the hard bone matrix. This explains why bones heal quickly. Volkman’s canals also run angles to the Haversian canals for communication. Bones are built tough. They can withstand lots of tension and force.

Bone Formation Ossification – the process of bone formation Ossification involved two major steps: 1) The hyaline cartilage is covered with bone matrix by bone forming cells called osteoblasts (baby). 2) The hyaline cartilage is digested away opening a medullary cavity in the bone.

Bone Formation Bones are remodeled in response to two factors: 1) calcium levels in the blood 2) The pull of gravity on the bones and muscles PTH controls the release of osteoclasts that control blood and calcium levels. Bone cells are laid down to become osteocytes making the bones stronger. On the other hand, the bones of elderly bed-ridden patients become brittle and break easily. SEE COMMON FRACTURES: Figure 5-5, pg 143

BONE fractures Fractures or breaks result from trauma of a twisting or smashing nature. Sports and automobile accidents top the list of caused for broken bones. Old age is also a reason. Reductions: OPEN – surgery using pins or wires to secure bones CLOSED – the bones are moved back into position by the doctor’s hands

Bone Repair Bone repair involves four major events: 1) The forming of a hematoma (blood-filled swelling) 2) The break is splinted by a fibrocartilage callus. New bone is formed and phagocytes eat up all of the dead tissue. 3) A bony callus is formed. 4) The callus is reformed to form a strong patch on the fracture.