Musculoskeletal System

• Bone: Connective tissue

  –       Matrix consist of cells separated with matrix.

  –       Collagen fibers and inorganic salts.
• Functions of the skeletal system


  • Support
  • Storage
  • Blood cell formation
  • Protection
  • Body movement/Leverage
• Support


  • Skeleton provides a firm framework to support the weight of the body
  • Gives shape to the body
  • Provides support eg lower limbs and pelvis hold up/support the upper body
• Storage


  • Bones store and release minerals and fats
• Storage of inorganic salts


  1. Calcium, phosphorus, sodium and potassium are stored within bone

  2. Minerals can be removed from bones when needed and distributed around the body by the circulatory system
• Storage of fats


  Fat is stored in adipose tissue in the yellow bone marrow which is found in hollow cavity in bones (particularly long bones)
• Blood cell formation


  • Red bone marrow which is found in certain bones contains stem cells
  • Stem cells can differentiate into blood cells : red blood cells, white blood cells, and platelets
  • In adults red marrow is found in spongy bone of flat bones such as skull and sternum and the ends of long bones such as the femur
• Protection


  • Bones protect delicate organs
  • Brain is encased with the skull
  • Spinal cord is contained within the spinal canal formed by the vertebrae
  • The heart and lungs are protected by the rib cage
• Body movement/Leverage


  • Bones are able to move (articulate) by the contraction and relaxation of the muscles
  • Bones act as levers, simple mechanical devices that can provide a force advantage
• Diaphysis

  •       Hollow cylinder (shaft) of compact bone surrounding a cavity (medullary/ yellow bone marrow cavity)

   

  •       Cavity used as fat storage: yellow bone marrow.

   
• Epiphysis (Epiphyses –plural)

  •       Enlarged ends of the bone

  •       Compact bone on outside.

  •       Central region: spongy/cancellous bone.

   

  ·       More porous, many large spaces filled with marrow (red bone marrow – where blood cell production takes place).

   
• Articular Cartilage

  •       Covers the end of the epiphysis 

   

  ·       layer of cartilage at the ends of the bone where it articulates with another bone
• Periosteum

  •       The dense, white, fibrous, vascularized white outer covering of the bone

   

  ·       It provides for the insertion point of tendons and ligaments

  ·       the inner membrane has bone forming cells use to shape the bone and for repair.

   
• Epiphyseal Line

  •       A line made up of two cartilage plates

  •       Located between the diaphysis and epiphysis of long bones

   
• Bone growth:

  •       Bone elongation occurs at the epiphyseal plates from birth through adolescence by producing new cells and increasing the length of the shaft

  •       At the end of adolescence the the thickness of the growth plates decreases and ossification occurs (usually finishes by the age of 25)

  •       Can be used to date the age of a corpse
• Compact Bone

  •       Found on the diaphysis of long bones

  •       Consists of many similar units called osteons or Haversian systems

  •       Osteons run parallel to long axis of bone for maximum strength

  •       Compact bone gives strength to bones and enables bones to provide strong mechanical levers
• Spongy/ Cancellous Bone

  •       Found in the epiphysis

  •       Light, porous bone

  •       enclosing numerous large spaces that give a honeycombed or spongy appearance.

  •       Matrix- organized into a three-dimensional latticework of bony processes, called trabeculae, arranged along lines of stress.

  •       The bone cells (osteocytes) occupy spaces in the trabeculae

  •       Nerve and blood vessels pass through irregular spaces in the matrix

  •       reduces the density of bone and allows the ends of long bones to compress as the result of stresses applied to the bone

   
• Chondrin –

  ·       cartilage’s extracellular matrix​

  ·       firm protein-carbohydrate complex ​

  ·       has protein fibres called collagen embedded in it
• Cartilage Connective Tissue Function:

  to support, protect and give structure to other tissues and organs
•  

   Cartilage cells

  ·       called chondroblasts produce the matrix and are eventually trapped in small spaces called lacunae​

  ·       Once this has occurred, they are referred to as chondrocytes
• Blood Supply- Perichondrium

   

  ·       Cartilage does not contain blood vessels, ​

  o   so nutrients & wastes rely on diffusion through the matrix (chondrin)​

  ·       Blood supply to the cartilage is from inner layer of perichondrium: ​

  o   fibrous membrane of connective tissue, covers external surface of cartilage​

  ·     Slow process, chondrocytes have slow metabolism and cell division. ​

  o   Injured cartilage therefore takes some time to heal
• Hyaline

  Gives strength & flexibility​

  ·       Closely packed collagenous fibers through the matrix​

   

  ·       Provides strength the cartilage​

  ·       Very fine, not distinguishable under a microscope

  ·       In adults hyaline cartilage is located:​

  ·       In the articular surface of movable joints​

  ·       The walls of the respiratory tract​

  ·       Nose, larynx, trachea and bronchi​

  ·       The epiphyseal plate of a long bone
• Elastic Cartilage

  Provides flexible support with elastic recoil​

  The most flexible cartilage as it can bounce back to its original shape, even with a strong force.

  ·       Obvious elastic fibers​

  ·       Also collagenous fibers similar to hyaline cartilage but not as closely packed​

  ·       Collagen fibers strengthen the cartilage

  Location: External ear, nasal tip
• Fibrous

  Resist the stresses to which intervertebral discs are subjected to

  ·       Intervertebral discs has a cartilage outer ring called the annulus fibrosus​

  Location: Intervertebral disks in the spine
•  

  Knee (Hyaline Cartilage)

   

  ·       contains cartilage named articular cartilage.​

  ·       Provides separation and a protective cushion between your thigh bone and tibia (bone from your knee to your ankle​

  ·       Without cartilage, your bones would rub together, creating extreme pain
•  

  Trachea (Hyaline Cartilage)

  ·       Tracheal cartilage keeps the trachea open and prevents it’s collapse from the negative pressure of the respiratory system​
• External Ear (Elastic Cartilage)

  ·       Auricular cartilage helps maintain the shape of the ear while allowing for flexibility
• The Larynx (Elastic and Hyaline Cartilage) Insert info into Respiratory System

   

  ·       Function: Phonation (making sound), Cough reflex, Protection of the lower respiratory tract
•  

  What are joints and its functions?

  ·       Site at which two or more bones come together.
• Functions of joints:​

   

  ·       Enable movement​

  ·       Allow bone growth​

  ·       Allow growth of the brain​

  ·       Allow changes in shape during childbirth​

  ·       Binds parts of the skeleton
• Factors affecting joints:​

  ·       Articular Surfaces-  When larger and fit together eg.  Ball and socket joint is more stable compared to the shallow flatter joint of the knee​

  ·       Ligaments – join bones to bones and help to direct bone movement and prevent excessive movement​

  ·       Muscle Tone – the tone of the muscles whose tendons cross the joint.  The greater their strength the more stable the joint.​
• Joint Capsule

  Outer layer is tough and fibrous connective tissue (dense fibrous connective tissue)​

   

  o   Dense CT has a high proportion of tightly packed collagen fibers providing strength

  Connects periosteum of the articulating bone. Flexibility permits movement and strength prevents dislocation​
• Synovial Membrane

  inner layer of joint capsule.  Made of loose CT and is well supplied with blood vessels​

   

  o   Loose CT provides more movement (loose CT fibers are less densely packed)

  Secretes synovial fluid, lubricating the joint to reduce friction between the two bones.
• Articular Cartilage

  Hyaline cartilage covers the ends of articulating bones

  Prevents friction by providing surface for a movement
• Cruciate Ligament

   Ligaments are fibrous connective tissue that attaches bones to bones​

  o   A band of strong, fibrous CT

  Joins bone to bone and provides stability
• Meniscus

  A wedge of tough, flexible cartilage that divides synovial cavity (space) into to two so that synovial fluid can be directed into the area of greatest function.

  Reduces wear and tear to joint surfaces and increases stability
• Tendon

  Dense CT that attaches muscles to other body parts, usually bone

  Dense fibrous CT made up of primarily collagen fibres

  Attaches muscles to bones
• H & J Bursa

  Little bags of synovial fluid​

  Reduced friction between a bone and a tendon or ligament or a bone and the skin​
• Synovial Fluid

   

  Slippery fluid like egg white which fills synovial cavity​

  Reduces friction, stops articulating bones from making contact, nourishes cartilage and contains phagocytes to get rid of microorganisms and debris​

   

  -Only a small amount is normally present but it can increase if the joint is injured which can lead to swelling and pain
• 1.)   Fibrous/Mixed Joints

   

  ·       No movement. ​

  ·       Bones held by connective tissue​

  ·       Very strong, difficult to damage.​

  ·       Skull sutures between teeth and jaw.