1. Skeletal System

2. Introduction The framework of bones and cartilage that protects our organs and allows us to move is called the skeletal system. The branch of medicine that deals with the preservation and restoration of the skeletal system, articulations (joints), and associated structures is called orthopaedics.

3. The skeletal system performs the following functions: Support Protection (for internal organs) Movement Mineral storage Storage of blood cell-producing cells Storage of energy

4. Bone is very strong for its relatively light weight The major components of bone are: – Calcium carbonate – Calcium phosphate – Collagen – Water Bone Composition Cortical Bone Spongy Bone Medullary (marrow) cavity

5. Bone Composition Cont’d Calcium carbonate and calcium phosphate: – Make up 60-70% of bone weight – Provide much of the bone ’ s stiffness and resistance to pressing or squeezing forces Collagen (a protein): – Gives bone its characteristic flexibility and contributes to its ability to resist pulling and stretching forces – With aging, collagen is lost progressively and bone becomes more brittle. Water – Bone consists of much smaller proportion of water than other body parts

6. Bone Classification According to the degree of porosity, bone can be classified into two general categories: – Cortical bone (low porosity) – Spongy or cancellous bone (high porosity)

7. Cancellous boneCompact Bone Porosity High (Low mineral content and high collagen) Low (High mineral content and low collagen) Structure Honey comb Compact Characteristic Provides more flexibility but is not as stress resistant Stiffer and can resist greater stress but less flexible Function Shock absorption due to its better ability to change shape are important Withstanding stress in body areas that are subject to higher impact loads Location e.g. vertebraeLong bones (e.g. bones of the arms and legs)

8. Effect of Fitness on Bone When bones are subjected to regular physical activity and habitual loads, they tend to become denser and more mineralized – e.g. Right forearm of the right-handed tennis player is more dense than her left one from using it more frequently Inactivity works in the opposite direction, leading to a decrease in weight and strength. – e.g. Loss of bone mass has been noted in bed-ridden patients, inactive senior citizens, and astronauts

9. Types of Bones There are five principal types of bones All bones are classified based on shape

10. 1.Long bones (e.g. thighs, legs, toes, arms, forearms, and fingers) greater length than width consist of a shaft and extremities (ends) slightly curved for strength consist mostly of compact bone (dense bone with few spaces) but also contain considerable amounts of spongy bone (bone with large spaces)

11. 2.Short bones (e.g. wrist, ankle bones) Somewhat cube-shaped and nearly equal in length and width Spongy except at the surface where there is a thin layer of compact bone

12. 3.Flat bones (e.g. cranial bones, sternum, ribs, scapulas) Generally thin and composed of two more or less parallel plates of compact bone enclosing a layer of spongy bone Flat bones afford considerable protection and provide extensive areas for muscle attachment

13. 4.Irregular bones (e.g. vertebrae, and certain facial bones) Have complex shapes and cannot be grouped into any of the other three categories They vary in the amount of spongy and compact bone

14. 5.Sesamoid bones Are small bones in tendons where considerable pressure develops, for instance, the wrist Their number varies greatly from person to person All people have at least two sesamoid bones: the patella (kneecap)

15. Divisions of the Skeletal System The adult human skeleton consists of 206 bones grouped as the axial skeleton and the appendicular skeleton. The axial division consists of the bones of the skull, auditory ossicles, hyoid bone, ribs, breastbone, and the backbone. The appendicular division consists of the bones of the upper and lower extremities (limbs), plus the bones called girdles, which connect the extremities to the axial skeleton. There are 80 bones in the axial division and 126 in the appendicular. Listed below are the divisions of the skeletal system.

16. Skull Sternum Ribs Vertebral Column Axial Skeleton

17. Skull Divided into two parts: a) Calvaria b) Face

18. a) Calvaria Frontal Bone Parietal Bone Temporal Bone Occipital Bone

19. Calvaria Cont. May be fractured in blows to the skull (e.g., in hockey, being checked and hitting the skull on the ice) Temporal bone: – more fragile of the calvaria bones – overlies one of the major blood vessels – if fractured and displaced internally = medical emergency (picture)

20. b) Facial Bones Lacrimal Bone Nasal Bone Maxilla Bone Mandible Bone Zygomatic Bone

21. Vertebral Column Sacrum (mid-line region of buttocks) Coccyx (4 or 5 fused vertebrae of the tail bone) 7 Cervical Vertebrae (of the neck) 12 Thoracic Vertebrae (of the chest) 5 Lumbar Vertebrae (of the lower back) Lumbar vertebra, lateral view Lumbar vertebra, superior view

22. Vertebral Column Vertebrae are arranged in a cylindrical column interspersed with fibrocartilaginous (intervertebral) discs Function: – provides a strong and flexible support for the body and the ability to keep the body erect – the point of attachment for the muscles of the back. – protect the spinal cord and nerves – absorbs shock through the intervertebral discs without causing damage to other vertebrae

23. Ribs Twelve pairs Made up of : – bone – cartilage which strengthen the chest cage and permit it to expand. Curved and slightly twisted making it ideal to protect the chest area

24. Ribs Cont’d All 12 pairs of ribs articulate with the twelve thoracic vertebrae posteriorly Classified into three groups based on anterior attachment: (picture) – true ribs 1-7 attach to both the vertebrae and the sternum – false ribs 8-10 attach only to the sternum indirectly, through 7 th rib – floating ribs 11 and 12 only attach to the vertebral column

25. The Ribs Manubrium Sternal Body Xiphoid Process Costal Cartilages True Ribs (1-7) False Ribs (8-10) Floating Ribs (11-12)

26. Sternum Mid-line breast bone The clavicles and ribs one to seven articulate with the sternum Sternum – comprised of the manubrium, sternal body and xiphoid process

27. Consists of:  1. The pectoral gridle (chest)  2. Pelvic girdle (hip)  3. The upper limbs  4. The lower limbs Appendicular skeleton

28. 1.Pectoral Girdle Consists of: – Scapula (shoulder blade) – Clavicle (collar bone) Allows the upper limb great mobility The sternoclavicular joint is the only point of attachment between the axial skeleton and the pectoral girdle Scapula Clavicle

29. 2. Pelvic Girdle Formed by pair of os coxae (hip bones) supports the bladder and abdominal contents Attachment: – Posteriorly – join with the sacrum – Anteriorly - join to each other anteriorly – Laterally – join to the head of thigh bone through a cup-shaped acetabulum

30. 3. Upper Limb Humerus – The arm bone – shoulder to elbow Radius and Ulna – The forearm bones – elbow to wrist – the radius being located on the thumb side of the hand – when you pronate the forearm, the radius is actually crossing over the ulna - try it yourself Humerus Ulna Radius

31. Upper Limb Cont. Carpals Phalanges Metacarpals Proximal Phalanx Middle Phalanx Distal Phalanx

32. 4. Lower Limb Femur – thigh bone – from hip to knee Patella – knee cap – sesamoid bone in the tendon of the quadriceps muscles (thigh) Femur Patella

33. Lower Limb Cont’d Tibia and Fibula – leg bones – From knee to ankle – Tibia is medial and fibula is lateral Medial malleolus and Lateral malleolus – The distal ends of the tibia and fibula, respectively – commonly referred to as the "ankle bones" – can be easily palpated Fibula Tibia Lat. malleolus Med. malleolus

34. Lower Limb Cont’d Tarsals – ankle bones – calcaneus or the heel bone – talus Metatarsals – 5 bones of the foot – unite with the toes Phalanges – toe bones – three per toe except the big toe - proximal, middle and distal Calcaneus Talus Phalanges Metatarsals Tarsals

35. Skeletal Surface Markings The surfaces of bones have various structural features adapted to specific functions. These features are called surface markings. Long bones that bear a great deal of weight have large, rounded ends that can form sturdy joints, for example. Other bones have depressions that receive the rounded ends.

36. Depressions and Openings Foramenan opening through which blood vessels, nerves, or ligaments pass Example: Meatusa tubelike passageway running within a bone Example: Paranasal sinus an air-filled cavity within a bone connected to the nasal cavity Fossaa depression in or on a boneExample:

37. Processes that form Joints Condylea large, rounded articular prominence Example: Heada rounded articular projection supported on the constricted portion (neck) of a bone Example: Faceta smooth, flat surfaceExample:

38. Processes to which tendons, ligaments and other connective tissues attach Tuberositya large, rounded, usually roughened process Example: Spinous process a sharp, slender projectionExample: Trochantera large, blunt projection found only on the femur Example: Cresta prominent border or ridgeExample: