Skeletal system

• Bones provide a framework that supports the body and cradles its soft organs
• Bones of lower limbs act as pillars to support the body trunk when standing
• Rib cage supports the thoracic wall
• Fused bones of the skull protect the brain
• Vertebrae surround the spinal cord
• Rib cage helps protect the vital organs of the thorax
• Skeletal muscles attach to bones by tendons and use bones as levers to move the body and its parts
• We can walk, grasp objects, and breathe due to skeletal muscles using bones as levers
• The design of joints determines the types of movement possible
• Bone is a reservoir for minerals, mainly calcium and phosphate
• Stored minerals are released into the bloodstream as needed for distribution to all parts of the body
• "Deposits" and "withdrawals" of minerals to and from the bones occur almost continuously
• Mineralized bone matrix stores important growth factors such as insulin-like growth factors, transforming growth factor, bone morphogenic proteins, and others
• Most blood cell formation, or hematopoiesis, occurs in the marrow cavities of certain bones
• Ossification is the process of bone formation. Ossification begins during the sixth or seventh week of embryonic life.The two types of ossification are : intramembranous and endochondral.
• In the intramembranous ossification, bone forms directly on or within loose fibrous connective tissue membranes.

  
  

  
  

  In the second type, endochondral ossification, bone form within hyaline cartilage.
• 1. Heredity: genes contribute to genetic potential for height. b. Nutrition: part of the bone matrix includes calcium, phosphorus, and protein become; vitamin D is needed for absorption of calcium in the small intestine; vitamins C and A are needed for bone matrix production (calcification). c. Hormones: concerned with cell division, protein synthesis, calcium metabolism, and energy production. d. Exercise or stress: weight-bearing bones must bear weight or they will lose calcium and become brittle.
• 1. Osteocytes (cells) are found in the matrix of calcium phosphate, calcium carbonate, and collagen. 2. Compact bone: contains haversian systems 3. Spongy bone: without haversian systems but red bone marrow is present. 4. Articular cartilage which is smooth and found on joint surfaces. 5. Periosteum made of fibrous connective tissue membrane which anchors tendons and ligaments and contains blood vessels that enter the bone.
• diaphysis (shaft) of a long bone medullary cavity within the diaphysis endosteum a thin layer of connective tissue that lines the medullary cavity epiphysis either end of the diaphysis consisting of spongy bone surrounded by compact bone. Red bone marrow is found within the pores of the spongy bone.
• epiphyseal plate separates the diaphysis and epiphysis; a region of mitotic activity responsible for linear bone growth (elongation). epiphyseal line replaces the plate when bone growth is completed. periosteum a dense regular connective tissue covers the bone and is the site of tendon-muscle attachment and diameter bone growth (widening).
• 1. Long - arms, legs; shaft is the diaphysis (compact bone) with a marrow cavity containing yellow bone marrow (fat); ends are epiphyses (spongy bone) b. Short - wrists, ankles (spongy bone covered with compact bone). c. Flat ribs, pelvic bone, cranial bones (spongy bone covered with compact bone). d. Irregular - vertebrae, facial bones (spongy bone covered with compact bone).
• The adult human skeleton consists of 206 named bones. These bones are grouped into two principal divisions: axial skeleton ( 80 bones) and appendicular skeleton ( 126 bones).
• uThe axial skeleton forms the longitudinal axis of the body.uIts principal subdivisions are the skull, vertebral column, and bony thorax. It. provides support and protection (by enclosure).
• Skull a. Cranium The cranium forms the vault and base of the skull, which protect the brain, eyes and ears . The eight bones of the cranium include the paired parietal and temporal bones and the single frontal, occipital, ethmoid, and sphenoid bones. frontal bone : forms the forehead. parietal bone: extend to the side of skull. Occipital bones: curves to form the base of the skull. temporal: located on sides. sphenoid: complete sides and contribute to orbits. ethmoid: part of the orbital wall and contributes to nasal septum The immovable joints between these bones are called sutures.
• Sutures are joints in the cranium the names reflect the bones they unite. These are the following sutures: coronal, sagittal, lambdoid, and squamous.
• Fontanels Are soft spots in the cranium of the newborn

  There are also six large membranous area, called fontanels ("soft spots”) that permit the skull to undergo changes in shape (molding) during childbirth.

  These also permit rapid growth of the brain during infancy.

  Ossification of these fontanels is normally complete by 20 to 24 months.

  The major fontanels are the anterior, posterior, anterolateral and posterolateral.
• The facial skeleton provides openings for the respiratory and digestive passages and attachment for facial muscles. Facial bones make up the face (maxillae, palatine, mandible, zygomatic, lacrimal, vomer, nasal, and inferior nasal concha) a. mandible: the lower jaw. b. maxillae: the upper jaw and anterior portion of the hard palate c. palatine bones: posterior portion of the hard palate and floor of the nasal cavity d. zygomatic bones: cheekbones e. lacrimal bones: lies between ethmoid and maxilla bone f. nasal bones: form bridge of nose g. vomer: helps form nasal septum
• Paranasal sinuses

  -air cavities in the maxillae, frontal, sphenoid, and ethmoid bones;

  -they lighten the skull and provide resonance for voice
• Ear ossicles (malleus, incus, stapes)

  Three auditory bones in each middle ear cavity transmit vibrations for the hearing process.
• Hyoid bone -supported in the neck by ligaments

  -serves as an attachment point for tongue and neck muscles.
• Vertebral column Includes 24 movable vertebrae, 7 cervical, 12 thoracic, and 5 lumbar and the sacrum and coccyx.

  With the exception ofC; and C2, all vertebrae have a body, two transverse processes, two superior and two interior articular processes, a spinous process, and a vertebral arch.

  The vertebrae support trunk and head, encloses and protects the spinal cord in the vertebral canal.
• Discs of fibrous cartilage absorb shock between the bodies of adjacent vertebrae, also permit slight movement. Four natural curves center head over body for walking upright.

  The primary curvatures of the vertebral column are the thoracic and sacral, the secondary curvatures are the cervical and lumbar.

  Curvatures increase spine flexibility.
• The bones of the thoracic cage include the 12 rib pairs, the sternum, and the thoracic vertebrae. The thoracic cage protects the organs of the thoracic cavity and upper abdominal organs from mechanical injury and is expanded to contribute to inhalation.
• Sternum consists of manubrium, body, and xiphoid process

  All ribs articulate with thoracic vertebrae

  true ribs (first seven pairs) articulate directly with sternum by means or costal cartilages

  false ribs (next three pairs) articulate with 7th costal cartilage

  floating ribs (last two pairs) do not articulate with the sternum.
• The appendicular skeleton consists of the bones of the pectoral and pelvic girdles and the limbs (extremities). It allows mobility for manipulation and locomotion.
• Pectoral girdle consists of one clavicle and one scapula. The pectoral girdles attach the upper limbs to the axial skeleton.
• Clavicles (collarbones). The clavicles hold the scapulae laterally away from the thorax. The sternoclavicular joints are the only attachment points of the pectoral girdle to the axial skeleton.

  
  

  Scapulae (shoulder blade). The scapulae articulate with the clavicles and with the humerus bones of the arms.
• Upper extremities (upper limbs) Each upper limb consists of 30 bones and is specialized for mobility.

  Arm/forearm/hand

  composed solely of the humerus(upper arm) articulates with the scapula and the ulna (elbow).

  the forearm is composed of the radius and ulna articulate with one another and with carpals;

  the hand consists of the carpals (wrist), metacarpals(hand

  phalanges (fingers)
• Pelvic girdle It is a heavy structure specialized for weight bearing, is composed of two hip bones that secure the lower limbs to the axial skeleton.

  Together with the sacrum, the hip bones form the basin-like bony pelvis.

  Each hip bone consists of three fused bones: ilium, ischium, and pubis

  The acetabulum occurs at the point of fusion.
• Pelvic structure and childbearing. The male pelvis is deep and narrow with larger, heavier bones than those of the female. The female pelvis, which forms the birth canal, is shallow and wide.