Skeletal System Flashcards
Name the six functions of the skeletal system.
Support
Protection
Movement
Mineral homeostasis
Blood cell production
Triglyceride storage
What are the classifications of bones based on shape? Give an example for each.
- Long bones* have an extended longitudinal axes and articular ends. (femur, humerus)
- Short bones* are cube- or box-shaped (carpals, tarsals)
- Flat bones* are broad and thin with a flattened surface (scapulae, ribs, sternum)
- Irregular bones* do not fit into other categories (patella, vertebral bones, facial bones)
What are the classifications of the skeleton?
The axial skeleton whcich is composed of the bones that lie aroud the longitudinal axis of the body
The appendicular skeleton whcih si composed of upper and lower limbs (extremities or appendages) and the bones forming the girdles that connect the limbs to the axial skeleton
What are the two classifications of bone tissue?
- Compact bone* contains few spaces and is the strongest form of bone tissue. It is dense and solid in appearance and provides protection and support against mechanical stress.
- Cancellous bone* is composed of open spaces partially filled by an assemblage of needle-like structures.
What are the four types of cells that are present in bone tissue?
- Osteogeic cells* which are unspecialised bone stem cells derived from mesenchyme.
- Osteoblasts* are bone building cells. They synthesise and secrete collagen fibres and organic components needed to build the extracellular matrix of bone tissue, and they initiate calcification. Osteoblasts surround themselves with EMC, trapping themselves in secretions and becoming osteocytes.
- Osteocytes* are mature bone cells, they are the main cell type in bone tissue and maintain its daily metabolism, such as exchange of nutrients and wastes with the blood.
- Osteoclasts* are huge cells derives from the fusion of monocytes and are concentrated in the endosteum. Osteoclasts release powerful lysosomal enzymes and acds that digest the protein and mineral components of bone ECM, a process called resorption.
What is the composition of the ECM?
- Hydroxyapatite:* a substance made up from a combination of minerals which calcifies with the aid of osteoblasts, to create the hardness of bone.
- Collagen fibres:* form the framework of the ECM, increase tensile strength.
- Water*
Why is calcium concentration in the blood tightly regulated?
Proper nerve and muscle function requires a narrow range of calcium ion concentration.
What happens when blood calcium concentration is low?
The parathyroid hormone (PTH) is released from the parathyroid gland which increases the activity of osteoclasts, breaking down bone to release calcium into the blood.
What happens when blood calcium concentration is high?
When blood calcium concentration is high, calcitonin is released from the C cells of the thyroid gland, which increases the activity of osteoblasts, forming bone which decreases the concentration of calcium in the blood.
What is a joint?
A joint is a point of contact between two bones, between bone and cartilage or between bone and teeth.
How are joints classified structurally?
The structural classification of joints is based on two criteria:
The presence or absense of space between the articulatin bones, called a synovial cavity
The type of connective tissue that binds the bones together
What are the classes of joints?
- Fibrous*: no synovial cavity, and the bones are held together by dense irregular connective tissue that is rich in collagen fibres.
- Carilaginous:* no synovial cavity, and the bones are held together by cartilage
- Synovial:* the bones forming the joint have a synovial cavity and are united by the dense, irregular connective tissue of the articular capsule, and often by accessory ligaments.
What are the terms of movement?
Flexion/tension
Abduction/adduction
Medial (internal)/lateral (external rotation)
What is the composition of cartilage?
Cartilage consists of a dense network of collagen fibres and elastic fibres firmly embedded in chondroitin sulphate.
The cells of cartilage are chondrocytes which occur singularly or in groups within spaces called lacunae. These chondrocytes are separated by the ECM which is composed of collagen fibres, proteoglycan and water. There are no blood vessels in the ECM of cartilage.
What is the strcture of a long bone?
- Diaphysis:* the bone shaft or body
- Epiphysis:* ends of the bone
- Metaphysis:* regions between diaphysis and epiphysis
- Articular cartilage:* thin layer of hyaline cartilage covering the epiphyses. Reduces friction and absorbs shock.
- Periosteum:* tough connective tissue sheath and associated blood supply that surrounds the bone surface.
- Medullary cavity:* marrow cavity in the diaphysis.
- Endosteum:* thin membrane that lies the medullary cavity. Contains a single layer of osteoblasts and small amount of CT.
Draw a long bone and label.
