Skeletal system Flashcards
Skeletal system: components and functions
Components
- Bones and joints of the body and their associated cartilage
Function
- Support and protection
- Surface for muscle attachment
- Aids body movement
- Houses cells that produce blood cells
- Stores minerals and lipids
What is bone?
-is a very dense connective tissue;
- is one of the hardest structures in the human body;
-contributes to approximately 60% of the bodies weight;
-is composed of:
Water 10%;
Organic tissue 30%;
Inorganic salts 60%.
-Although bone is one of the hardest structures, it maintains a degree of elasticity due to structure and composition.
What is the axial skeleton?
- Bones that form the upright axis of the body:
Skull, hyoid bone, bones of the vertebral column, sternum and ribs - Consists of 80 bones.
- Form the central region of the skeleton that is the axis. Some are single, others are paired.
Bones of the axial skeleton
- Skull: Cranial bones, Facial bones
- Spine: Cervical, Thoracic, Lumbar, Sacral, Coccygeal
- Ribs
- Sternum
What is the appendicular skeleton?
- Bones that are appended to the axial skeleton.
- Upper and lower extremities, including the shoulder and hip girdles.
- Consists of 126 bones (Note the sesamoid bones are excluded in the count with the exception of the patella and the pisiform)
Bones of the appendicular skeleton: upper limb
- Clavicle
- Scapula
- Humerus
- Radius
- Ulna
- Carpal bones
- Metacarpal bones
- Phalanges
Bones of the appendicular skeleton: Lower limb
- Innominate bone
- Femur
- Patella
- Tibia
- Fibula
- Tarsal bones
- Metatarsals
- Phalanges
What are the 5 classification of bone?
- Long
- Short
- Flat
- Irregular
- Sesamoid
Describe Long and which bones are classified as long
- Consist of a cylindrical diaphysis (shaft) of compact bone with two expanded ends (epiphyses).
- These bones provide a large surface area for attachment of muscle to enable articulation.
- Bones that are classified as long are:
Humerus, femur, radius, ulna, tibia, fibula, phalanges, metacarpals, metatarsals, clavicles
Describe short and which bones are classified as short
- Consist of cancellous bone (spongy bone) covered with a thin layer of compact bone. These are found at sites where strength but limited movement is required. These bones vary considerably in shape, but are many considered to be cuboidal.
- Bones that are classified as short are:
The tarsal and carpal bones - The exception is the pisiform which is a carpal bone and is a sesamoid bone.
Describe flat and which bones are classified as flat
- Consist of a thin layer of compact bone enclosing a layer of cancellous bone. Found where protection of underlying organs or the need for space for muscle attachment is the greatest need. These bones have a large surface area compared to their depth.
- Bones that are classified as flat are:
Vault of the skull, scapula, ribs and sternum
Describe irregular and which bones are classified as irregular
- Consist of cancellous bone surrounded by a layer of compact bone. Bones in this classification vary considerably in their size and shape.
- Bones that are classified as irregular are:
Vertebrae, facial bones, Sphenoid, Ethmoid, mandible, Auditory ossicles, Hyoid bone, and hip bones (innominate).
Describe sesamoid and which bones are classified as sesamoid
- Nodules of bone that ossify within a tendon at a point of friction. The purpose of sesamoid bones is to protect muscle and tendons from wear and provide a channel for their movement as they glide over the bony surface.
- Main sesamoid bone is the patella.
- Other sesamoid bones exist in the foot and hand, mainly related to the great toe and thumb, but others can be located within the hand and foot also pisiform.
what are accessory ossicles?
- These are normal variants that are unfused secondary ossification centres remaining separate from the bone.
- These can be located throughout the body.
Structure of long bone
- Periosteum
- Cortical or Compact
- Cancellous, Spongy or Trabecular
- Endosteum
What is periosteum and its function?
- Fibrous membrane or layer.
- Covers the external surface of bone
- The periosteum consists of two layers:
Outer fibrous layer
Inner vascular layer - Sharpey’s fibres are tufts of collagen fibres that extend from the fibrous layer into the bone matrix.
- Contains nutrient foramina
Function:
- Protective outer covering of bone
- Provides attachment for muscles, tendons and ligaments.
- Contains blood vessels, that provide blood supply to the bone
- Forms new bone by means of osteoblasts found in the inner layer of the periosteum.
What is cortical or compact bone?
- Dense and ivory like.
- Approximately 80% of bone is of the cortical type.
- Has strength, present in the cortex of diaphysis. Covers the cancellous bone.
- Cortical bone consists of irregularly spaced overlapping cylindrical units these are microscopic and known as Haversian systems or osteons
Cancellous, Spongy or Trabecular
- similar in structure to compact bone
- bone marrow is found between trabeculea.
- generally found at the ends of long bones, vertebral bodies and flat bone.
- Trabeculea form the internal support structure of the bone. Approximately 20% of bone is of the trabecular type.
- site of greatest bone turnover
- Cancellous bone has a spongy texture
- Provides large spaces for blood forming cells to occupy.
- bone is used where lightness, strength and area are required
What is endosteum?
- Connective tissue
- covers the trabeculae of spongy bone in the marrow cavities and lines the canals that pass through compact bone.
- Like the periosteum the endosteum contains osteoblasts and osteoclasts.
What is bone marrow?
- Soft pulpy substance, composed of connective tissue and cells. Located in the cavity of long bones and in spaces between the trabaculae of all bones.
- Two kinds:
Red bone marrow
Yellow bone marrow
Bone development: Ossification
- Cartilagenous or membranous precursors are later changed to bone through the process of Ossification
- Ossification can occur in:
Hyaline cartilage (intracartilaginous or endochondral ossification)
or
Membrane (intramembranous ossification). - Most bones ossify in cartilage but some do ossify in membrane. Processes are identical to one another.
Primary and secondary ossification
Primary ossification centre:
area where bone development starts. In long bone this is the shaft and is termed the diaphysis
Secondary ossification centres:
occur later in bone development and are usually related to features of bone. In long bone occur at the ends. This is termed the epiphysis
What is metaphysis?
The epiphysis is separated from the diaphysis by the metaphysis. The is the a cartilaginous part and remains until growth cease through the union of the diaphysis and the epiphysis. Known as the growth plate.
