skeletal system

Section 1: Bone

==function: support, protection, movement, storage of minerals and fats, blood cell formation (hematopoiesis)==

at birth we are born with 300 bones, but they fuse over time; as an adult, we have 206 bones

osteocytes = bone cells

  • osteoBlasts = bone-forming cells, makes lamellae/matrix (Blasts Build Bones)
  • osteoClasts = break down lamellae/matrix for remodeling (Clasts Cut)

ossification: formation of bones

  • embryonic bones are made of hyaline cartilage; osteoblasts create the bone matrix, then cartilage is digested away
    • bones are joined by fibrous membranes, then replaced with bones within 2 years of birth (sutures)
  • ==new cartilage grows and is eventually replaced by bone== (cartilage in nose, ears, and ribs persist for life)
  • epiphyseal plates = cartilage in plate/on heads of bone grows and is then ossified to make new bone
  • to widen the bone, osteoblasts add bone tissue to the outside of the diaphysis
  • bone growth is controlled by growth and sex hormones

==calcium== is needed for neurotransmitter release, relieving blood clots, and creating/strengthening bones + muscles (stronger bones are needed to support large muscles, and vice versa)

Section 1.5: Bone Types

Long Bone

  • has a long longitudinal axis and expanded ends; supports the weight of the body
  • femur, humerus, tibia, fibula, carpals/tarsals, radius, ulna, etc

Flat Bone

  • platelike structures with broad surfaces
  • skull plates, thoracic cage, pelvis

Short Bone

  • have roughly equal widths and lengths
  • carpals, tarsals, bones of ankles

Irregular Bone

  • variety of shapes, most are connected to several other bones
  • spinal cord, some bones in the skull, ossicles, cervical vertebrae

Compact Bone

  • homogenous (smooth and solid)

Spongy Bone

  • small needle-like pieces of bone, short/irregular/flat bone

Section 2: Long / Compact Bone Anatomy (done)

 

  • diaphysis = shaft/middle, composed of compact bone

  • (distal/proximal) epiphysis = ends/heads of the bone, composed of mostly spongy bone

  • epiphyseal line = where diaphysis & epiphysis meet, made of cartilage

  • periosteum = outside lining of the diaphysis, made of fibrous connective tissue

  • perforating fibers = secure periosteum to the underlying bone

  • medullary cavity = cavity of the shaft; contains yellow marrow (mostly fat) in adults

    • the spongy bone of epiphysis contains red marrow (for hematopoiesis) in infants

  • {{osteon = a unit of bone{{

  • {{central canal = opening in the center of an osteon, carries blood vessels + nerves to bone cells{{

  • {{perforating canal = canal is perpendicular to the central canal{{

  • {{lacunae = cavity containing bone cells, arranged in rings{{

  • {{lamellae = rings around the central canal, sites of lacunae{{

  • {{canaliculi = tiny canals that radiate from the central canal to lacunae, forms a transport system for bone cells to share nutrients & information{{

Section 3: Joints

based on ==FUNCTION + STRUCTURE==:

  • {{Fibrous = generally immovable; sutures of the skull{{
    • {{united by fibrous tissue{{
  • {{Cartilaginous = immovable or slightly moveable (with fibrocartilage); ribs to sternum, pubic symphysis{{
    • {{bones connected by cartilage{{
  • {{Synovial = freely moveable; hips, knee, jaw…{{
    • {{separated by a joint cavity (lined with synovial membrane); ligaments reinforce the joint{{

based on ==SHAPE==: (all are SYNOVIAL)

  • Plane/Gliding = bones glide along each other; between carpals & tarsals
  • Hinge = open/close movement; in knees, elbows, jaw…
  • Pivot = rotational movement; radius against ulna on the proximal end
  • Condyloid = rocking motion; proximal phalanges/metacarpals
  • Saddle = flexion + extension; thumb & carpals below
  • Ball and Socket = many different types of movement; hips/shoulders

Section 4: Skeleton

largest bone = femur

smallest bone = ossicles in ear (malleus, incus, stapes)

categories: bones, joints, cartilage, ligaments, bone marrow (red, yellow)

  • ==MAJOR parts of skeletal system = bones, ligaments, cartilage==

==AXIAL (flat & irregular) – cranium, vertebral column, bony thorax==

  • skull:
    • cranium (8 large flat bones) = part that surrounds the brain
    • held together via sutures
    • 2 sets of paired bones: parietal and temporal
    • 4 single bones: frontal, occipital, sphenoid, ethmoid
    • facial bones
    • 12 sets of paired bones: maxillary, palatine, zygomatic, nasal, lacrimal
    • 2 single bones: mandible, vomer
    • paranasal sinuses: around nose cavity, hollow space
  • hyoid bone:
    • above the larynx, a moveable base for the tongue (muscles help for swallowing/speech)
    • does not join with another bone
  • vertebral column:
    • 26 irregular bones
    • intervertebral discs = made of cartilage, provides cushion + shock absorption
    • cervical (neck) = first 7, thoracic (rib cage) = next 12, lumbar (lower back) = last 5, sacrum + coccyx (tailbone) = 2 fused
  • thorax:
    • forms a cage to protect major organs
    • sternum, ribs, thoracic vertebrae
    • true ribs (bone to bone) = first 7, false ribs = next 5 (bone to cartilage to bone), floating ribs = last 2 (hanging, bone)
    • costal cartilage connects ribs to the sternum

==appendicular (long & short) – shoulder girdle, arms, pelvic girdle, legs==

  • ==pectoral girdle = bones that make up the shoulder joint==
    • clavicle and scapula = allow upper limbs to have free movement
    • upper arm = humerus (long bone, rounded head fits into scapula)
    • forearm = ==radius (thumb side), ulna (pinky side)==
    • hand = carpals (wrist), metacarpals (palm), phalanges (fingers)
    • ==carpals = short bones, metacarpals + phalanges = long bones==
  • ==pelvic girdle = bones that make up the hip joint==
    • hip bones = ilium, ischium, pubic bone - the place where all fuses = acetabulum
    • protects several organs
    • false pelvis = iliac crest to iliac crest
    • true pelvis = opening inside pelvic girdle
    • ==male pelvis < female pelvis==
    • thigh = femur (deep socket joint, several ligaments reinforce this joint)
    • lower leg = fibula, tibia
    • foot = tarsals (heel and ankle), metatarsals (sole of foot), phalanges (toes)
    • ==tarsals = short bones, metatarsals + phalanges = long bones==

Section 5: Fractures

  • Open/Compound = broken bone penetrates through the skin
  • Closed/Simple = broken bone doesn’t penetrate through the skin
  • Displaced = a gap from the pieces of the bone is formed around the fracture
  • Non-displaced = bone breaks but doesn’t move out of place
  • Pathologic = fracture due to disease
  • Stable = minimal damage done, easiest to repair
  • Transverse = bone is broken at a right angle to the bone’s axis
  • Spiral = one part of the bone has been twisted at the breaking point
  • Comminuted = bone breaks into several pieces, hardest to repair
  • Stress = hairline fracture
  • Buckled = one side of the bone bends, but the other side doesn’t break
  • Greenstick = incomplete fracture, bone is bent

fracture treatment:

  • reduction = realignment (closed = manual manipulation; open = surgery using rods/metal)
  • immobilized = allows for bone repair (cast/traction)
  • normally repairs in 6-8 weeks