SKELETAL SYSTEM

• Made up of: bones, cartilage, ligaments and joints of the body (20% body weight)

• 206 bones divided into axial and appendicular skeleton

• (The pectoral and pelvic girdle attach the bones from upper and lower extremities to the axial Skeleton)

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• Axial Skeleton: 80 bones 

  • skull

  • ribs 

  • sternum 

  • vertebral column

  • Appendicular skeleton: 

  • 126 bones 

  • pectoral girdle (scapula and clavicle) (shoulder)

  • bones of the upper (ulna, humerus, radius, carpal bones, metacarpals and phalanges) 

  • lower extremities (femur, tibia, fibula,tarsal bones, metatarsals and phalanges)

• Skeleton functions:

  •  Protection of the vital organs:

    • Ribcage = surrounds heart and lungs

    • Skull = encloses brain

    • Vertebrae = surround spinal cord

  • Supports and maintenance of posture

  • Skeleton provides a framework for the body and each part bears the weight of all structures of the body above it.

  • Bones in lower extremities = larger (walk on feet not hands)

  • Providing attachment points for the muscles

  • Muscles run from one bone to another connected by tendons

  • Bones = not completely smooth (roughed areas where tendons attach)

  • When muscles and tendons contract, they pull on the bones causing movement at the joints

  • Storage and release of minerals such as calcium and phosphorus

  • Important for muscle contraction and nerve activity

  • Released into the blood to maintain mineral homeostasis and so are distributed to the rest of the body

  • Blood cell prod or haemopoiesis

  • Red & white blood cells and platelets are produced in red bone marrow (in flat bones such as ribs and sternum or in end of long bones such as femur and humerus)

  • Storage of energy

    • Lopes stored in yellow bone marrow 

    • Provides chemical energy reserves

• AXIAL SKELETON

• Function: protect ~ skull sternum, ribs and vertebral column enclose structure of the body 

  • Skull

• On top of the vertebral column divided into cranium and face 

• Protects brain bones, eyes, ears and contain the teeth

  • Vertebral column (TSCC)

• 33 vertebrae stacked on top of each other forming vertebral column

• Characteristics: very strong and flexible (bends forwards/backwards/laterally/ rotates)

• Vertebrae divided into sections and together form 40% of total height

• Vertebrae in each section have similar structure but there are some differences

• Vertebrae don’t touch -> intervertebral disc between them  (rings of fibrocartilage and soft gel)

• Function: make it more flexible and flatten and bulge out the sides when they are compressed (shock absorbers)

• Sternum and ribs

• Flat bone that starts at the bottom of the throat ->  the chest in the center

• Ribs: curved and articulate with sternum (front) thoracic (back)

  • 12 ribs

  • 1-7 = attach to sternum

  • 8-10 = false ribs (to 7)

  • 11-12 = floating ribs (lower part of the anterior rib cage)

  • Thoracic cage -> sternum, ribs and thoracic. 

  • Intercostal muscles -> essential for breathing between ribs  

  • (por eso cuando nos hacemos daño en las costillas nos afecta a la respiración)

• APPENDICULAR SKELETON: 

  • Upper body

  • Scapula / clavicles 

  • Humerus 

  • Ulna (fina)/Radius

  • Carpals (2 rows/4)

  • Metacarpals

  • Phalanges (3 each finger while thumb 2) (fine joints only specific movements)

  • Lower body

  • Pelvis (ilium, ischium and pubis)

  • Sacrum

  • Femur (long/heavy)

  • Tibia

  • Fibula

  • Patella (maintains position of tendon when knee is flexed and protects it)

• Tarsals

• Metatarsals

BONES

Location and function determines size and shape of bones. Types:

Long Bones -> most important for movement (femur, metatarsals and clavicle)

Short Bones -> articulate with more than one bone normally (carpals and tarsals)

Flat Bones -> provide protection and area for muscle attachment (sternum, scapula, ribs and pelvis)

Irregular bones -> specialized shapes and functions (vertebrae, sacrum and coccyx)

STRUCTURE OF A LONG BONE: 

Bone contains collagen, water and mineral salts

When minerals accumulate around collagen fibers they crystalize and harden tissue. 

Collagen fibers provide high tensile strength

THREE CONNECTIVE TISSUES

· Cartilage -> bone to bone {reduces friction,

 reduces shock and protects bone} (BB)

· Ligament -> bone to bone (BB)

· Tendon -> muscle to bone (MB)

JOINTS

Joint or articulation is where two or more bones come into contact or articulate with each other

FUNCTION: increase mobility of body and limbs

  Types of joints:

· Fibrous: Thin layer of fibrous tissue connecting edges of the two bones. Fixed / No movement       

· Cartilaginous: Bones separated by fibrocartilage disc or hyaline cartilage. Limited movement 

· Synovial: (has joint cavity) Complete Movement  *most important for movement*   

1. 1.  Synovial membrane:  Lines inside of the capsule and secretes synovial fluid

   2. · Synovial fluid:  🍳  Released by the synovial membrane.  Lubricates joint cavity, reduces friction and provides nutrients to the cartilage.

   3. Bursae: Small fluid sacs where 2 structures rub together (L&B, T&B, S&B) Lubricates and reduces friction

   4. Meniscus: Discs of fibrocartilage between articulating bones. Allows bones to fit together more tightly.

   5. Ligaments: Connects bone to bone and provides support.

   6.  Articular cartilage: layer of cartilage that covers articulating surfaces of the bones. Reduces friction, absorbs shock and protects bones. Varies in thickness depending on the amount of stress that it is exposed to. When wears away causes friction and pain

   7. Articular capsule:  Sleeve-like structure that surrounds a joint. Flexible and allows movement while preventing dislocation.

TYPES OF SYNOVIAL JOINTS

Gliding joint -> least movement (between tarsal and carpal bones) 

Hinge joint -> bend or straighten in 1D (elbow joint)

Pivot joint -> one forms ring where other roll/pivot (radius rotates around ulna)

Condyloid -> convex surface fits into concave surface (radius and carpal bones)

Saddle -> saddle and rider. Move in two directions (metacarpals of thumb and carpal)

Ball and socket joint -> move in all directions. (shoulder and hip joints)