SKELETAL SYSYTEM

skeletal system useful for Bachelor of Pharmacy, Doctor of pharmacy and diploma in pharmacy students

1. S keletal System SURESH BABU EMANDI M.Pharm Vikas Institute of Pharmaceutical Sciences Near Air Port, Rajahmundry,Andhrapradesh [email protected]

2. Although bones are often thought to be static or permanent they are highly vascular living structures that are continuously being remodelled

3. Types of bones Bones are classified as Long bones Short bones Irregular bones Flat bones Sesamoid bones.

4. Long bones. These consist of a shaft and two extremities. As the name suggests the length is much greater than the width. Examples include the femur, tibia and fibula. Short, irregular, flat and sesamoid bones. These have no shafts or extremities and are diverse in shape and size. Examples include: • short bones — carpals (wrist) • irregular bones—vertebrae and some skull bones • flat bones — sternum, ribs and most skull bones • sesamoid bones — patella (knee cap).

5. Bone is a strong and durable type of connective tissue. It consists of: • water (25%) • organic constituents including osteoid (the carbon containing part of the matrix) and bone cells (25%) • inorganic constituents, mainly calcium phosphate (50 %).

6. The bones primarily give support to the appendages and protect the fragile organs of the body such as the brain, spinal cord, heart, and lungs. They also store calcium and phoshorus in the hard bone matrix, which can be released when needed elsewhere. The bumps, ridges, and grooves on the surface of bones provide attachment sites for the skeletal muscles. Additionally, many bones contain a soft tissue called marrow that produces new blood cells and stores fat

7. Bone is one of the hardest parts of the body Very lightweight Can resist tension Calcium salts make it hard Collagen fibers make it strong and flexible

8. Support Internal framework of body Ex: Legs support body trunk, rib cage supports chest wall Protection Protects soft body organs (skull protects brain, ribs protect heart and lungs, etc) Movement* Muscles use bones as levers to move body NOT a function skeletal system can do on it’s own Storage Fat storage In yellow marrow Mineral storage Calcium, phosphorus, and others. Blood cell formation Hematopoeisis Occurs in bone marrow of long bones

9. The adult human skeleton is a framework of 206 bones and is anatomically divided into two parts, The axial skeleton The appendicular skeleton Two types of bone Compact bone 🞄 Homogeneous appearance 🞄 Dense, looks smooth Spongy bone 🞄 Small needle-like pieces 🞄 Lots of open spaces 🞄 (Looks like a sponge, hence the name)

10. In embryos… Skeleton made of hyaline cartilage Gets replaced by bone with age Cartilage remains in a few places… Bridge of nose Parts of ribs Joints

11. Epiphyseal plates allow for growth of long bone during childhood New cartilage is continuously formed Older cartilage becomes ossified Cartilage is broken down Bone replaces cartilage Bones remodeled, lengthened until growth stops Bones change shape somewhat Bones grow in width

12. Osteocyte Mature bone cell Osteoblast “Bone builders” Osteoclast “Bone destroyers” Break down bone matrix to remodel and/or release calcium

13. Bone remodeling is done by osteoblasts and osteoclasts Essential for bones to keep normal proportions and strength Bones get larger/thicker when… Large muscles are attached to them Need more bone to attach the large muscle to Bones get smaller/weaker when… Physical inactivity Non-use of muscles  atrophy Small muscles don’t need large bones to attach to  Bones remodeled to become smaller

14. Long Bones Longer than wide Contain shaft with head at each end Mostly compact bone Limbs (not ankle or wrist bones) Short Bones Cube-shaped Mostly spongy bone Wrist and ankle bones Patella (kneecap) Flat Bones Thin, flat, usually curved Two layers of compact bone with spongy bone in between Skull, ribs, breastbone Irregular Bones Don’t fit into the other categories Vertebrae, hip bones

15. Diaphysis Shaft Made of compact bone Epiphyses Ends of long bone Made of compact bone surrounding spongy bone Covered with articular cartilage Smooth, glassy, decreases friction at joints

16. Epiphyseal Line Line of bone tissue that looks different from rest of bone Remnant of epiphyseal plate 🞄 Hyaline cartilage 🞄 Causes long bones to grow lengthwise

17. Periosteum Outer covering of shaft Like “skin” on chicken bone Sharpey’s fibers Attach periosteum to bone Arteries Supply nutrients to bone cells

18. Medullary Cavity In shaft Contains yellow marrow (adipose) in adults Contains red marrow in infants (for blood cell formation)

19. Osteon (Haversian system) A “unit” of bone Central (Haversian) canal Opening in center of osteon Contains blood vessels Perforating (Volkman’s) canal Perpendicular to central canal Contains blood vessels and nerves

20. Lacunae Cavities that contain osteocytes (bone cells) Arranged in concentric rings (like tree rings) Lamellae Rings around the central canal Where the lacunae can be found

21. Canaliculi Tiny canals Radiate from central canal to lacunae Transport nutrients to bone cells

22. The human skeleton can be divided into two The axial skeleton The appendicular skeleton. The axial skeleton is formed by the vertebral column, the rib cage, the skull and other associated bones. The appendicular skeleton, which is attached to the axial skeleton, is formed by the shoulder girdle, the pelvic girdle and the bones of the upper and lower limbs.

23. The core of the skeleton is referred to as the axial skeleton. It consists of the following 80 bones. The upright posture of humans is maintained by the axial skeleton, which transmits the weight from the head, the trunk, and the upper extremities down to the lower extremities at the hip joints. Skull: 22 bones Hyoid: 1 bone Vertebrae: 32 -34 bones Ribs: 24 bones Sternum: 1 bone

24. The skull consists of 22 bones and 7 associated bones. All the larger skull bones are shown in this exploded view. They fall into two main groups. One group (including the frontal, parietal, and temporal bones) surrounds the brain and is fused together to form the cranium. The remainder of the bones form the face. Sutures Interlocking, immovable joints holding most skullbones together 🞄 Mandible-only freely movable bone in skull

25. This highly flexible structure, also called the vertebral column, supports the head and body. It also protects the delicate tissues of the spinal cord. It is made up of 32-34 bones called vertebrae, separated by intervertebral discs, which act as shock absorbers. The bones of the spine are kept in place and supported by attached ligaments and muscles.

26. Hollow portions of bone around nasal cavity Named for bones they are found in Lighten skull Amplify sounds when speaking/ give resonance

27. Large in comparison to body length of infant Contains fontanelles Soft fibrous membranes connecting cranial bones 🞄 “Soft Spots” 🞄 Usually convert to bone around 24 months after birth

28. Vertebrae named for their location 7 cervical vertebrae 🞄 C1 = Atlas 🞄 C2 = Axis 12 thoracic vertebrae 5 lumbar vertebrae Sacrum 🞄 5 fused vertebrae Coccyx 🞄 4 fused vertebrae Vertebrae separated by fibrocartilage discs Cushions/absorbs shock

29. Forms a cage to protect organs Three parts Sternum 🞄 Flat bone 🞄 3 fused bones 🞄 Manubrium 🞄 Body 🞄 Xyphoid process 🞄 Attached to first 7 pair of ribs Rib Cage 🞄 12 pairs 🞄 True Ribs= 7 pair 🞄 False Ribs = 5 pair 🞄 Floating Ribs = 2 pair Thoracic vertebrae

30. The appendicular skeleton is divided into six major regions: Pectoral girdles (4 bones) – Left and right clavicle (2) Scapula (2). Arms and forearms (6 bones) – Left and right humerus (2) (arm) Ulna (2) Radius (2) (forearm). Hands (54 bones) – Left and right carpals (16) (wrist) Metacarpals (10) Proximal phalanges (10), Intermediate phalanges (8) Distal phalanges (10) Pelvis (2 bones) – Left and right hip bone (2). Thighs and legs (8 bones) – Left and right femur (2) (thigh) Patella (2) (knee) Tibia (2) Fibula (2) (leg). Feet and ankles (52 bones) Left and right tarsals (14) (ankle) Metatarsals (10) Proximal phalanges (10) Intermediate phalanges (8) Distal phalanges (10).

31. Pectoral girdles (4 bones) Left and right clavicle (2) Scapula (2).

32. Arms and forearms (6 bones) – Left and right humerus (2) (arm) Ulna (2) Radius (2) (forearm).

33. Hands (54 bones) – Left and right carpals (16) (wrist) Metacarpals (10) Proximal phalanges (10), Intermediate phalanges (8) Distal phalanges (10)

34. Three pairs of fused bones Ilium Ischium Pubic bone Carries total weight of upper body Protects Reproductive organs Bladder Part of large intestine

35. Female inlet larger/more circular Female pelvis is shallower, bones lighter/thinner Female hip bones flare wider Female sacrum is shorter/less curved Female pubic arch is more rounded/angle is greater

36. Left and right femur (2) (thigh) Patella (2) (knee) Tibia (2) Fibula (2) (leg).

37. Left and right tarsals (14) (ankle) Metatarsals (10) Proximal phalanges (10) Intermediate phalanges (8) Distal phalanges (10).

38. A joint is the site at which any two or more bones articulate or come together. Some joints have no movement (fibrous), some only slight movement (cartilaginous) and some are freely movable (synovial).

39. Articulations of bones Functions Hold bones together Mobility Classified by stru c t u r e/ f u nct i on

40. Fibrous joints or Immovable 🞄 EX: sutures of skull Cartilaginous joints OR slightly movable EX : Pubic symphysis and Vertebrae Synovial joints Freely movable

41. Fibrous /immovable/fixed Joints A fibrous joint is a fixed joint where collagenous fibrous connective tissue connects two bones . Fibrous joints ( synarthroses ) are usually immovable and have no joint cavity. They are subdivided further into sutures, gomphoses , and syndesmoses. Sutures are immobile joints found only in the cranium.

42. Fibrous/immovable/fixed joints

43. Cartilaginous or slightly movable joints There is a pad of fibrocartilage between the ends of the bones that form the joint which allows for very slight movement where the pad of cartilage is compressed. Examples include the symphysis pubis and the joints between the vertebral bodies .

44. Cartilaginous or Slightly movable joints

45. Synovial or freely movable joints Synovial joints have characteristic features that enable a wide range of movements. They are classified according to the range of movement possible or to the shape of the articulating parts of the bones involved

46. Classification of synovial joints Ball and socket Hinge joints Gliding joints Pivot joints . Condyloid Saddle joints

47. Ball and socket. The head or ball of one bone articulates with a socket of another and the shape of the bones allows for a wide range of movement. Those possible are flexion, extension, adduction, abduction, rotation and circumduction . Examples are the shoulder and hip.

48. Hinge joints . These allow the movements of flexion and extension only. They are the elbow, knee, ankle, the joints between the atlas and the occipital bone, and the interphalangeal joints of the fingers and toes.

49. Gliding joints . The articular surfaces glide over each other, e.g. sternoclavicular joints, acromioclavicular joints and joints between the carpal bones and those between the tarsal bones.

50. Pivot joints. Movement is round one axis (rotation), e.g. proximal and distal radioulnar joints and the joint between the atlas and the odontoid process of the axis

51. Condyloid and saddle joints Movements take place round two axes, permitting flexion, extension, abduction, adduction and circumduction, e.g. the wrist, temporomandibular, metacarpophalangeal and metatarsophalangeal joints .

52. Characteristics of a synovial joint All synovial joints have certain characteristics in common . Articular or hyaline cartilage The parts of the bones which are in contact are always covered with hyaline cartilage. It provides a smooth articular surface and is strong enough to absorb compression forces and bear the weight of the body .

53. The cartilage lining, which is up to 7mm thick in young people, becomes thinner and less compressible with age. This leads to increasing stress on other structures in the joint. Cartilage has no blood supply and receives its nourishment from synovial fluid.

54. Capsule or capsular ligament The joint is surrounded and enclosed by a sleeve of fibrous tissue which holds the bones together. It is sufficiently loose to allow freedom of movement but strong enough to protect it from injury.

55. Synovial membrane This is composed of epithelial cells and is found: lining the capsule covering those parts of the bones within the joint not covered by articular cartilage covering all intra-capsular structures that do not bear weight .

56. Synovial fluid This is a thick sticky fluid, of egg-white consistency, secreted by synovial membranes into the synovial cavity . Provides nutrients for the structures within the joint cavity.

57. Synovial fluid contains phagocytes, which remove microbes and cellular debris. Acts as a lubricant. Maintains joint stability. Prevents the ends of the bones from being separated, as does a little water between two glass surfaces.

58. Little sacs of synovial fluid or bursae are present in some joints , e.g. the knee. They act as cushions to prevent friction between a bone and a ligament or tendon, or skin where a bone in a joint is near the surface.

59. Other intra-capsular structures Some joints have structures within the capsule, but outside the synovial membrane, which assist in maintenance of stability, e.g. fat pads and menisci in the knee joint. When these structures do not bear weight they are covered by synovial membrane .

60. Extracapsular structures Ligaments that blend with the capsule provide additional stability at most joints. Muscles or their tendons also provide stability and stretch across the joints they move. When the muscle contracts it shortens, pulling one bone towards the other

61. Articulating bones separated by joint cavity Articular cartilage covers bone ends Joint surfaces enclosed by fibrous capsule Cavity contains synovial fluid Ligaments help reinforce the joint Associated Joint Structures Bursae 🞄 Flat fibrous sacs 🞄 Lined with synovial membrane 🞄 Contains synovial fluid 🞄 Common where ligaments, muscles, skin, tendons rub together Tendon sheath 🞄 Elongated bursa wrapping around a tendon that deals with lots of friction 🞄 Like a bun around hot dog

62. A break in a bone Types of Fractures Simple (closed) fracture 🞄 Bone breaks cleanly, does not penetrate skin Compound (open) Fracture 🞄 When bone ends penetrate through skin Treated by reduction and immobilization Realignment of bone ends

63. Hematoma forms Blood vessels rupture when bone breaks Blood filled swelling Cells without nutrients die Fibrocartilage callus forms Made of connective tissue Splints the break Phagocytes dispose of dead tissue Bony callus forms Osteoblasts/clasts move in, create callus of spongy bone Remodeling Osteoblasts/clasts remodel in response to stress on the bone Helps strengthen bone Creates a permanent “patch” at the site Often, a healed fracture can be stronger than the rest of the bone

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