The Skeletal System Flashcards
5 Categories of Bone
- Long
- Short
- Flat
- Irregular
- Sesamoid
5 Functions of the skeleton
- Support
- Assistance in movement
- Protection
- Mineral homeostasis
- Blood cell production
Name 7 Long Bones
Femur Tibia Fibula Phalanx Humerus Ulna Radius
Describe Long Bones
- Long bones have both compact (dense) and spongy (latticework) bone tissue.
- They are slightly curved for strength, have greater length than width, consist of a shaft & a variable number of extremities (ends).
Name 2 Short Bones
Carpals
Tarsals
Describe Short Bones
- Short bones are somewhat curved in shape and nearly equal in length & width.
- They are spongy bone, except at the surface where there is a thin layer of compact bone.
Name 4 Flat Bones
Cranial bones
Sternum
Ribs
Scapulae
Describe Flat Bones
- They are generally thin and composed of two nearly parallel plates of compact bones enclosing a layer of spongy bone.
- Flat bones afford considerable protection & provide extensive areas for muscle attachment.
Name 2 Irregular Bones
Vertebrae
Some facial bones
Describe Irregular Bones
- They have complex shapes & cannot be grouped into any of the other bone categories.
- They vary in the amount of spongy & compact bone they are made up of.
Name the Sesamoid bone
Patella
Describe the Sesamoid bone
- Shaped like a Sesame seed - are small bones that are bedded in tendons where considerable pressure develops.
- They can change the direction of pull of a tendon.
Shape Variations
• Genetic code • Diet • Mechanical stresses/gravity • Exercise versus activity • Bones surface markings - depressions & openings - processes that form joints - processes to which tendons, ligaments & other connective tissues attach
STRUCTURE OF BONE
Describe
Mature bone is about 25% water, 25% protein fibres (organic material) and 50% mineral salts (inorganic material).
The matrix of bone, unlike that of other connective tissues, contains abundant mineral salts. These salts are deposited in the framework by the collagen fibres of the matrix, crystallisation occurs and the tissue hardens.
If all the organic material (collagen fibres) and water were removed from bone, the remaining structure would crumble. If all the inorganic material (mineral salts) were removed, the remaining bone could be twisted and bent in all directions.
TYPES OF BONE TISSUE
Two
Compact bone
Spongy or cancellous bone
TYPE OF BONE TISSUE
Compact bone
(Describe)
It forms the external layer of all bones and the bulk of the diaphyses of long bones.
Compact bone tissue provides protection and support and helps the long bones resist the stress of weight placed on them.
The shafts of long bones and short bones are hollow, forming the medullary canal, which is filled with yellow bone marrow (a form of fat). Irregular and flat bones do not have a medullary canal.
TYPE OF BONE TISSUE
Spongy or cancellous bone
(Describe)
Spongy or cancellous bone
It is loosely packed giving the tissue a porous texture with a ‘latticework’ appearance.
Spongy bone makes up most of the bone tissue of short, flat, and irregular shaped bones, and most of the epiphyses of long bones.
At the ends of some long bones are the sites of red bone marrow storage and thus haemopoiesis in adults.
BLOOD SUPPLY TO BONY TISSUE
Bony tissue contains cells called osteocytes – mature bone cells that maintain the daily activities of bone tissues.
The extreme outer layer of bony cells receives nourishment from the rich capillary supply of the periosteum. This consists of two layers of tough skin which line the entire surface of the bone, except for the articulating surfaces at the joints, which are covered in hyaline cartilage.
The outermost layer is tough, connective tissue, the fibres of which grow into the underlying compact bone forming a strong inseparable union. The thin inner layer contains specialised cells which are vitally important in the growth, repair and remodelling of bones.
Four functions of the periosteum
1 To protect the bone
2 For the attachment of muscles
3 To nourish the bone
4 For the formation of bone tissue
BLOOD SUPPLY TO BONY TISSUE
Small vessels pierce through the thin layer of compact bone at various places on irregular bones and at the ends of the long bones to nourish the spongy bone within. Once the blood vessels pierce through the outer layer of the compact bone they branch into numerous capillaries which tranverse the porous latticework of the spongy bone.
The shaft of each long bone has a prominent hole called the nutrient foramen. Blood vessels which pass through this foramen enter the medullary canal and nourish the compact bone of the shaft.
As compact bone is so dense, a special network of microscopic canals is required to transport the nutrients. These are:
- Vertical or Haversian canals
- Horizontal or Volkmann canals
BONE GROWTH
Throughout the body bones enlarge by appositional growth, and long bones lengthen by the addition of bone material at the epiphyseal plate.
Appositional bone growth
The bone lining the medullary cavity is destroyed by osteoclasts in the endosteum so that the cavity increases in diameter. At the same time, osteoblasts from the periosteum add new bone tissue to the outer surface. Initially, diaphyseal and epiphyseal ossification produces only spongy bone. Later, the outer region of spongy bone is reorganised into compact bone.
