Skeletal system

• Characteristics of Bone:

  • composed of proteinaceous organic matrix and largely collagen as well as inorganic matrix which is calcium phosphate salt known as "hydroxyapatite"
• Function of Skeletal System:

  • For protection: the rib cage protects the heart, lungs, and other organs of the thorax
  • For support: cartilage provides firm yet flexible support within structures like the nose, external ear, thoracic cage, and trachea
  • Movement: contraction of skeletal muscles moves the bones, producing body movements
  • For storage: some minerals in the blood are taken into the bone and stored
  • For blood cell production: many bones contain cavities filled with bone marrow that gives rise to blood cells and platelets
• 4 Types of Bone Cells:

  • Osteoblasts
  • Osteocytes
  • Osteoclasts
  • Bone lining cells
• Type of Bone as to Texture:

  • Compact bone: found in the shafts of long bones (diaphyses), making up 80% of all bone
  • Spongy (cancellous) bone: found at the ends of long bones (epiphysis), making up 20% of all bone, contains red bone marrow and a network of bony trabeculae
• Bone Development:

  • Intramembranous Ossification: bone formation in connective tissue membranes, forming cranial bones and clavicles
  • Endochondral Ossification: bone formation in cartilage models, such as short and long bones
• Factors Affecting Bone Growth:

  • Vitamin D: necessary for normal absorption of calcium from intestines
  • Vitamin C: necessary for collagen synthesis by osteoblasts
  • Growth Hormone: from anterior pituitary, stimulates overall bone growth by stimulating interstitial cartilage growth & appositional growth.
  • Thyroid Hormone: normal growth of all tissues, including cartilage; therefore a decrease in this hormone result in decrease size of the individual
  • Sex Hormones: Estrogen & Progesterone initially stimulate bone growth, w/c accounts for the burst of growth at the time of puberty.
• Bone Remodeling:

  • Replacement of old bone tissue by new bone tissue, mainly occurs in the adult skeleton to maintain bone mass
  • 5 Phases of Bone Remodeling: bone reversal, bone formation, bone quiescence, bone resorption, bone activation
• Fractures:

  • Breaking of bone or cartilage
  • Factors determining fractures: energy of the event and strength of the bone.
• Bone Repair:

  • Hematoma formation
  • Callus formation
  • Callus ossification
  • Bone remodeling
• Osteoporosis: Condition characterized by progressive loss of bone density, thinning of bone tissue, and increased vulnerability to fractures; Joint pain & tenderness, Swelling , Warmth over the affected joint

  • Osteoporotic bones are more porous and therefore more vulnerable to fracture.
• Osteoarthritis:

  • Chronic disease of joint cartilage and bone, often resulting from "wear and tear" on the joint (“degenerative arthritis“)
  • Other causes include congenital defects, trauma, and metabolic disorders
• Osteomyelitis:

  • Bone inflammation resulting from bacterial infection like Staphylococcus aureus
• Microcephaly:

  • Characterized by head circumference less than the 3rd percentile
  • Often occurs due to failure of the brain to grow at a normal rate
• Diaphysis shaft: Site of hemopoiesis in the adult; Scientific name for bone shaft
• Epiphyseal plate: Site of longitudinal growth.
• Marrow cavity: Site of fat storage
• Periosteum: protective layer, for attachment of ligaments & tendons.
• Compact bone: Hard, dense bone, gives strength to the hollow part of the bone.
• Epiphysis head: Site of spongy bone
• Hyaline cartilage: Growth in length of bones & bone repair followed by its replacement with bone.
• Hyaline Cartilage: most intimately associated with bones; most of the bones in the body develop from it.
• Appositional Growth: The formation of

  new bone on the surface of older bone or cartilage.
• Intervertebral Disks: The disk becomes more compressed with increasing age so that the distance between vertebrae & over-all height of individual decreases.

  • The annulus fibrosus also becomes weaker

  with age & more susceptible to herniation.
• Wrist: Relatively short region between the forearm and hand, composed of 8 carpal bones arranged into two rows of four each.
• Carpal tunnel syndrome: Irritation of the median nerve causing tingling burning & numbness of the hand such as of the thumb, index, and the middle fingers. Occurs frequently among people who use their hands a lot.
• Radius fractures: resulting from an outstretched hand.
• Cleft Palate/Lip: when the palatine processes of the maxillae don’t fuse with one another; produces an opening between nasal & oral cavities, making it difficult to eat or drink or to speak distinctly.
• Osteoporosis: may result from disease, dietary or hormonal deficiency or advanced age.
• Rickets: insufficient vitamin D resulting from reduced mineralization of the bone matrix; bowed bones & inflamed joints.
• Osteomalacia: weak, soft or brittle bones in adults.
• Scurvy: Vitamin C deficiency; Marked by ulceration & hemorrhage in almost any area of the body because of the lack of collagen synthesis in connective tissue.
• Dwarfism: abnormally short.
• Pituitary dwarfism: abnormally low level of pituitary

  growth hormone affect the whole body, thus, producing a small person.
• Achondroplastic dwarfism: nearly normal sized trunk & head but shorter than normal limbs.
• Giantism: abnormally increased height that usually results from excessive cartilage & bone formation at the epiphyseal plate.
• Acromegaly: Caused by excess pituitary GH secretion; increased in the diameter of all bones strikingly apparent in the face & hands
• Growth hormone (GH): protein hormone released from the anterior pituitary gland under the control of the hypothalamus.