Skeletal System Flashcards
Skeletal System: Function
- Support – gives shape and provides framework for body
- Attachment – provides points of attachment for muscles and tendons
- Movement – when these muscles contract they allow movement
- Articulation – when two bones move around each other (skeleton allows varying degrees of movement depending on bones involved). - Protection – of vital body organs. Eg. Brain encased in Cranium
- Storage – for minerals, salts, and fats. Eg. Calcium, Phosphorus, Sodium and Potassium. Can be distributed to other parts of body when needed. Eg. pregnancy
- Red blood cell production – in the red bone marrow of spongy bone.
Skeletal System Division
Our 206 bones are divided into two divisions:
Axial Skeleton:
• Bones of skull – cranium, face and mandible
• Vertebrae – cervical, thoracic, lumbar, sacrum and coccyx
• Ribs & Sternum
Appendicular Skeleton:
• Upper limbs – Humerus, Ulna, Radius, Carpals, Metacarpals & Phalanges
• Lower limb – Femur, Patella, Tibia, Fibula, Tarsals, Metatarsals & Phalanges
• Pectoral (shoulder) girdle – Clavicle & Scapula Pelvic (hip) girdle - Pelvis
Long Bone
Epiphyses (singular, epiphysis) – the ends:
Compact bone on outside:
- Very dense and rigid, filled with tiny holes that hold blood vessels
- Protects spongy bone and bone marrow
Spongy (or Cancellous) bone on inside
- More porous than compact bone and has large spaces filled with marrow.
- In flat and long bones this is Red Bone Marrow (for Red and White blood cell and platelet production)
- Diaphysis (Main Shaft) - Hollow cylinder of Compact bone surrounding a cavity.
- Medullary cavity – Filled with Yellow Bone Marrow (fat/lipid storage)
- Periosteum – Dense, white, fibrous covering on outside of bone for strength. Richly supplied with blood vessels and nerves.
- Articular cartilage – covers each epiphysis for protection and cushioning
- Epiphyseal lines – bone growth areas in children
Compact Bone
- The structural unit of compact bone is an OSTEON (sometimes known as a Haversian system)
- They run parallel to the long axis of the bone to give strength.
- CENTRAL CANAL (Haversian canal) – centre of each osteon, contains blood capillaries, and sometimes nerves and lymph
- LAMELLAE – concentric layers of bony matrix which surround canal
- LACUNAE – small spaces in in the matrix between lamellae
- CANALICULI – tiny canals that run between Lacunae
- OSTEOCYTE (a bone cell) – occupies each Lacunae, projections enter the canaliculi and make contact with other bone cells, so materials can be passed from cell to cell.
Spongy Bone
- Spongy Bone is not arranged into osteons, instead it consists of irregular, thin, bony plates called Trabeculae
- Lamellae are not arranged in concentric layers, they are irregular
- Osteocytes still found in Lacunae
- Nerves and blood vessels pass through irregular spaces in matrix
Formation of Bone
- The process of forming bone is called OSSIFICATION.
- Bone growth occurs at the diaphysis and in the two epiphyses.
- The cartilage undergoes calcification through the deposition of calcium salts.
- The cartilage cells die and are replaced with OSTEOBLASTS which promote more deposition of calcium salts.
- Osteoblasts mature into OSTEOCYTES.
- Bone formation continues until only a small band of cartilage remains. The remnants of this area are known as the EPIPHYSEAL LINES when the bone stops growing.
3 Main Types of Joints
Fibrous or Fixed:
• no movement between bones
• held by fibrous connective tissue
• Eg. Sutures of the skull
Cartilaginous or slightly moveable:
• held in place by cartilage
• allows slight movement
• Eg: Symphysis pubis, Between vertebrae, Ribs and sternum
Synovial or freely moveable:
• amount of movement only limited by ligaments, muscles, tendons and adjoining bones
• various types
• Eg. Shoulder, hip, elbow, wrist, fingers, knee, ankle and toes.
Joints: Function
• The function of joints is to allow our body to move in many ways allowing for movement. They hold the skeleton together and support movement as well.
Examples of Joints
Shoulder, hip, elbow, wrist, fingers, knee, ankle and toes.
Synovial Joint 6 Types and Examples
- Ball and Socket (Hip, Shoulder)
- Hinge (Elbow, Fingers)
- Pivot (Between radius and ulna of the forearm)
- Gliding (Tarsals Bones)
- Saddle (Thumb joins the hand)
- Condyloid (ellipsoid) (Between radius and carpal bones of the wrist)
Structure of Knee Joint
• Freely moveable joints are also called Synovial joints because of the space between them, the SYNOVIAL CAVITY. The knee joint is a typical synovial joint.
• ARTICULAR CAPSULE – surrounds and encloses joint. Made of 2 parts:
• FIBROUS CAPSULE – dense fibrous CT, attached to periosteum of articulating bones. Holds bones together. Flexible for movement and strong to resist dislocation.
• SYNOVIAL MEMBRANE – inner layer of capsule. Loose CT, well supplied with blood vessels. Lines the joint cavity (except at articular cartilage).
Secretes synovial fluid.
- SYNOVIAL FLUID – fills synovial cavity. Lubricates the joint and provides nourishment for cells of cartilage. Contains phagocytic cells that remove microorganisms and debris that could cause wear and tear. Prevents articulating surfaces from touching.
- ARTICULAR CARTILAGE – covers articulating surfaces. Provides smooth surface for movement.
- ARTICULAR DISCS – (in knee called Menisci, singular Meniscus) Made of fibrocartilage that extends inward from articular cartilage. Divide synovial cavity into two, so that synovial fluid can be directed to areas of greatest friction.
- BURSAE – little sacs of synovial fluid (not in all joints). Prevent friction between bone and ligament/tendon or bone and skin.
- ACCESSORY LIGAMENTS – hold the bones together.
Movement at a Joint
- Flexion – bending, decreases angle between articulating bones
- Extension – straightening, increases angle between articulating bones
- Abduction – movement away from midline of body
- Adduction – movement towards midline of body
- Rotation – movement of a bone around its long axis
- Circumduction – circular movement
Osteoporosis vs Osteoarthiritis
Osteoporosis:
• Decrease in bone density due to a lack of calcium and vitamin D
• Results in an increase in risk of fractures
• Treatments: Calcium and Vitamin D Supplements, more calcium in diet and going out more for vitamin D, Hormone Therapy
Osteoarthritis:
• Deterioration of articular cartilage of joints
• Results in bones becoming exposed, and through friction of movement rub together, wearing away bone (pain and inflammation)
• Or causing spurs to grow which decrease cavity space and restrict movement of the joint
• Treatments: Anti-inflammatory Medications, Surgery, Physical Therapy
