Skeletal system Flashcards
what are the components of the skeletal system?
Bones and joints and their associated cartilage
What is the function of the skeletal system
-Support and protection
-Surface for muscle attachment
-Aids body movement
-Houses cells that produce blood cells -Stores minerals and lipids
what is a bone? what is it composed of?
Very dense connective tissue, it is composed of water (10%), Organic tissue (30%) and inorganic salts (60%).
What is the axial skeleton and what forms it?
How many bones does it consist of?
-Bones that form the upright axis of thebody:
-Skull, hyoid bone, bones of the vertebral column, sternum and ribs
-Consists of 80 bones
what are the main 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 axialskeleton.
* Upper and lower extremities, including the shoulder and hip girdles.
* Consists of 126 bones (Note the sesamoidbones are excluded in the count with theexception of the patella and the pisiform)
what are the five classifications of bone?
- Long- not to do with the size of the bone but what it contains.
- Short
- Flat
- Irregular
- Sesamoid
In addition to the 5 classification there are variations known as Accessory ossicles
What are long bones?
-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
Short (spongy bone).
-Consist of cancellous bone covered with a thin layer of compact bone.
-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.
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
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).
-Have features that are not consistent.
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 (knee cap). 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.
-indicating protection- which is why it’s a form of flat bone.
Accessory ossicles
-These are normal variants that are unfused secondary ossification centres remaining separate from the bone.
-These can be located throughout the body.
-look for radio-opaque line surrounding it.
what are the 4 main structures of long bone
- Periosteum- outside the bone
- Cortical or Compact
- Cancellous, Spongy or Trabecular
- Endosteum- inside the bone
Periosteum
-Fibrous membrane or layer.
-Covers the external surface of bone
-The periosteum consists of two layers:
-Outer fibrous layer
-Inner vascular layer
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.
Cortical or Compact Bone
*Dense and ivory like.
*Approximately 80% of bone is of the cortical type. Mixture of strength and stability.
*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
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.
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- Red bone marrow is for haemopoiesis ie blood forming
-Yellow bone marrow- Later in life after the age of 7 haemopoietic tissue replace by fat hence 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 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
Attached to diaphysis by cartilage.
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.
Cartilage is not visible on X-ray images
