1. The Skeletal System 5-1

2. Copyright 2008 John Wiley & Sons, Inc. The Skeletal System is a Dynamic Living System The skeletal system provides many essential functions including: The skeletal system provides many essential functions including: Providing support Providing support Anchoring skeletal muscles Anchoring skeletal muscles Protecting soft tissues and organs Protecting soft tissues and organs Producing blood cells (hematopoiesis) Producing blood cells (hematopoiesis) Storing and releasing minerals (calcium and phosphorus) Storing and releasing minerals (calcium and phosphorus) Moving with the help of joints Moving with the help of joints 5-2

3. Copyright 2008 John Wiley & Sons, Inc. The Skeletal System is a Dynamic Living System Bones look stable and static, but they change throughout life. Bones look stable and static, but they change throughout life. The entire calcium content of your femur is replaced approximately every five to seven years. The entire calcium content of your femur is replaced approximately every five to seven years. There are 206 named bones in the adult human skeletal system. There are 206 named bones in the adult human skeletal system. The skeleton is divided into the axial skeleton (the central axis of the body) and the appendicular skeleton (the appendages and girdles holding them to the central axis). The skeleton is divided into the axial skeleton (the central axis of the body) and the appendicular skeleton (the appendages and girdles holding them to the central axis). 5-3

4. Copyright 2008 John Wiley & Sons, Inc. The Skeleton Figure 5.2 The skeleton 5-4Copyright 2008 John Wiley & Sons, Inc.

5. Classification of bone We classify the bones according to shape: We classify the bones according to shape: Long bones – longer than wide Long bones – longer than wide Short bones – comparable to small cubes Short bones – comparable to small cubes Flat bones – thin in one dimension Flat bones – thin in one dimension Irregular bones – odd shaped Irregular bones – odd shaped Sesamoid bones – form inside tendons Sesamoid bones – form inside tendons Wormian bones – embedded in the sutures between the main skull bones Wormian bones – embedded in the sutures between the main skull bones 5-5Copyright 2008 John Wiley & Sons, Inc.

6. Classification of Bone Figure 5.3 Classification of bone 5-6

7. Copyright 2008 John Wiley & Sons, Inc. Classification of Bone Figure 5.3 Classification of bone 5-7

8. Copyright 2008 John Wiley & Sons, Inc. Classification of Bone Figure 5.3 Classification of bone 5-8

9. Copyright 2008 John Wiley & Sons, Inc. Classification of Bone Figure 5.3 Classification of bone 5-9

10. Copyright 2008 John Wiley & Sons, Inc. Figure 5.3 Classification of bone 5-10 Classification of Bone

11. Copyright 2008 John Wiley & Sons, Inc. Figure 5.3 Classification of bone 5-11 Classification of Bone

12. Copyright 2008 John Wiley & Sons, Inc. Form follows function Every bone is designed to perform a specific task. Every bone is designed to perform a specific task. Example: The femur must be strong and have a slight curve to bear the weight of the upper torso. Example: The femur must be strong and have a slight curve to bear the weight of the upper torso. Bones are composed of compact or spongy mineralized tissue that is structured for maximum strength and minimum weight. Bones are composed of compact or spongy mineralized tissue that is structured for maximum strength and minimum weight. 5-12

13. Copyright 2008 John Wiley & Sons, Inc. Ossification forms bone and remodeling continues to shape it Bones are connective tissue produced by immature bones cells called osteoblasts. Bones are connective tissue produced by immature bones cells called osteoblasts. Where is bone formed in the body? Where is bone formed in the body? Endochondral – within cartilage Endochondral – within cartilageor Intramembranous – between membranes Intramembranous – between membranes Which occurs more often? Which occurs more often? Endochondral Endochondral 5-13

14. Copyright 2008 John Wiley & Sons, Inc. Enochondral Ossification 5-14 Figure 5.4 Endochondral ossification

15. Copyright 2008 John Wiley & Sons, Inc. Bone growth Appositional growth occurs at the outer surface of the bone. Appositional growth occurs at the outer surface of the bone. The periosteum is the membrane that covers the bone. The periosteum is the membrane that covers the bone. The innermost cellular layer of the periosteum differentiates into osteoblasts and begins to add matrix to the exterior. The innermost cellular layer of the periosteum differentiates into osteoblasts and begins to add matrix to the exterior. The osteoblasts become trapped in the matrix and mature into osteocytes, which creates new bone tissue around the exterior of the bone. The osteoblasts become trapped in the matrix and mature into osteocytes, which creates new bone tissue around the exterior of the bone. 5-15

16. Copyright 2008 John Wiley & Sons, Inc. Intramembranous ossification Bone is made within embryonic connective tissue, surrounded by developing periosteum. Bone is made within embryonic connective tissue, surrounded by developing periosteum. These bones form deep in the dermis of the skin and are often called dermal bones. These bones form deep in the dermis of the skin and are often called dermal bones. This process forms the flat bones of the skull, clavicle, and mandible. This process forms the flat bones of the skull, clavicle, and mandible. 5-16

17. Copyright 2008 John Wiley & Sons, Inc. Intramembranous ossification 5-17 Figure 5.5 Intramembranous ossification

18. Copyright 2008 John Wiley & Sons, Inc. Bony tissue comes in two forms: Compact (dense) or spongy. Compact (dense) or spongy. Compact bone occurs on the outside of the bone and is composed of many individual Haversian systems. Compact bone occurs on the outside of the bone and is composed of many individual Haversian systems. Spongy bone comprises the inner support and is less organized. Spongy bone comprises the inner support and is less organized. Both forms are held inside the periosteum. Both forms are held inside the periosteum. 5-18

19. Copyright 2008 John Wiley & Sons, Inc. Compact bone Haversian systems Concentric rings of matrix laid by osteocytes and formed surrounding a central canal. Concentric rings of matrix laid by osteocytes and formed surrounding a central canal. An osteon is one complete Haversian system. An osteon is one complete Haversian system. The osteocytes must receive a constant supply of nutrients and dispose of wastes. The osteocytes must receive a constant supply of nutrients and dispose of wastes. The central cavity of the osteon houses the blood and nerve supply for the bone tissue. The central cavity of the osteon houses the blood and nerve supply for the bone tissue. Individual cells lie within small holes in the matrix called lacunae. Individual cells lie within small holes in the matrix called lacunae. 5-19

20. Copyright 2008 John Wiley & Sons, Inc. Compact bone Haversian systems Bone cells communicate with each other via small canals cut in the matrix called canaliculi. Bone cells communicate with each other via small canals cut in the matrix called canaliculi. These canals allow fluid carrying vital nutrients and signaling chemicals to pass between cells. These canals allow fluid carrying vital nutrients and signaling chemicals to pass between cells. 5-20

21. Copyright 2008 John Wiley & Sons, Inc. Havarsian system 5-21 Figure 5.6a Haversian system

22. Copyright 2008 John Wiley & Sons, Inc. Spongy bone Spongy bone has trabeculae, or struts, that form in response to stress. Spongy bone has trabeculae, or struts, that form in response to stress. The struts are composed of osteocytes surrounded by matrix. The struts are composed of osteocytes surrounded by matrix. 5-22 Figure 5.6b Spongy bone

23. Copyright 2008 John Wiley & Sons, Inc. The shaft of the long bone, or diaphysis, is composed of dense bone surrounding a central canal. The shaft of the long bone, or diaphysis, is composed of dense bone surrounding a central canal. The central canal houses the marrow. The central canal houses the marrow. Red marrow is where blood cells are formed. Red marrow is where blood cells are formed. Yellow marrow is where energy is stored. Yellow marrow is where energy is stored. 5-23 Figure 5.7 Long bone with parts identified

24. Copyright 2008 John Wiley & Sons, Inc. The ends of the bones, or epiphyses, include the epiphyseal plate. The ends of the bones, or epiphyses, include the epiphyseal plate. This is an area of cartilage where long bones continue to grow during childhood and adolescence. This is an area of cartilage where long bones continue to grow during childhood and adolescence. When bones cease growing, the cartilage is replaced by bone, leaving the epiphyseal line. When bones cease growing, the cartilage is replaced by bone, leaving the epiphyseal line. Articulating cartilage is a layer of hyaline cartilage found between two bones to prevent bones from grinding at the joints. Articulating cartilage is a layer of hyaline cartilage found between two bones to prevent bones from grinding at the joints. 5-24 Figure 5.7 Long bone with parts identified

25. Copyright 2008 John Wiley & Sons, Inc. The Axial Skeleton is the Center of Things The axial skeleton includes the 8 cranial and 14 facial bones, the hyoid, ribs and vertebra. The axial skeleton includes the 8 cranial and 14 facial bones, the hyoid, ribs and vertebra. The 8 cranial bones surround and protect the brain. The 8 cranial bones surround and protect the brain. How are the 8 cranial bones held together? How are the 8 cranial bones held together? by fixed joints called sutures by fixed joints called sutures To articulate means to join. What is an articulation? To articulate means to join. What is an articulation? a joint holding two bones together a joint holding two bones together 5-25

26. Copyright 2008 John Wiley & Sons, Inc. 8 cranial bones 1 Frontal bone 1 Frontal bone 2 Parietal bones 2 Parietal bones 2 Temporal bones 2 Temporal bones 1 Occipital bone 1 Occipital bone 1 Ethmoid bone 1 Ethmoid bone 1 Sphenoid bone 1 Sphenoid bone 5-26 Figure 5.8 Skull

27. Copyright 2008 John Wiley & Sons, Inc. 14 facial bones support the distinctive facial features of humans. 2 Maxillae bones 2 Maxillae bones 2 Palatine bones 2 Palatine bones 2 Nasal bones 2 Nasal bones 2 Lacrimal bones 2 Lacrimal bones 2 Zygomatic bones 2 Zygomatic bones 2 Inferior nasal conchae 2 Inferior nasal conchae 1 Mandible 1 Mandible 1 Vomer 1 Vomer 5-27

28. Copyright 2008 John Wiley & Sons, Inc.5-28 Figure 5.9 Facial bones

29. Copyright 2008 John Wiley & Sons, Inc. The bony orbital complex of the eye is composed of seven bones (three cranial and four facial). This provides the support for the eye. The bony orbital complex of the eye is composed of seven bones (three cranial and four facial). This provides the support for the eye. 5-29 Figure 5.11 Orbital complex

30. Copyright 2008 John Wiley & Sons, Inc. The nasal complex includes bones that encase the nasal cavities and the paranasal sinuses. The nasal complex includes bones that encase the nasal cavities and the paranasal sinuses. 5-30 Figure 5.12 Nasal complex

31. Copyright 2008 John Wiley & Sons, Inc. Hyoid, ribs and vertebrae The hyoid bone, which lies below the tongue, is the only bone in the skeleton that is not attached to another bony structure. The hyoid bone, which lies below the tongue, is the only bone in the skeleton that is not attached to another bony structure. The vertebrae, ribs and sternum allow upright posture and protect vital organs of the thoracic cavity. The vertebrae, ribs and sternum allow upright posture and protect vital organs of the thoracic cavity. Figure 5.14 Thoracic cage 5-31

32. Copyright 2008 John Wiley & Sons, Inc. Vertebral column 24 vertebrae 24 vertebrae 1 sacrum 1 sacrum 3-5 coccyx bones 3-5 coccyx bones 5-32 Figure 5.13 Vertebrae

33. Copyright 2008 John Wiley & Sons, Inc. Vertebral column A typical vertebra consists of 3 parts: A typical vertebra consists of 3 parts: Vertebral body Vertebral body Vertebral arch Vertebral arch Vertebral articular Vertebral articular processes processes 5-33 Figure 5.13 Vertebrae

34. Copyright 2008 John Wiley & Sons, Inc. Your limbs comprise your Appendicular Skeleton The appendicular skeleton includes all bones that are attached to the axial skeleton. The appendicular skeleton includes all bones that are attached to the axial skeleton. Pectoral girdle Pectoral girdle shoulder bones shoulder bones Upper appendages Upper appendages arms and hands arms and hands Pelvic girdle Pelvic girdle Lower appendages Lower appendages legs and feet legs and feet 5-34 Figure 5.15 Appendicular skeleton

35. Copyright 2008 John Wiley & Sons, Inc. Pectoral girdle Clavicle Clavicle 5-35 Figure 5.16 The clavicle

36. Copyright 2008 John Wiley & Sons, Inc. Pectoral girdle Scapulae Scapulae 5-36 Figure 5.17 The scapulae

37. Copyright 2008 John Wiley & Sons, Inc. Upper Appendages Humerus Humerus Carpals Carpals 2 rows of 4 short bones 2 rows of 4 short bones Scaphoid bone Scaphoid bone Lunate bone Lunate bone Triquetrum Triquetrum Pisiform bone Pisiform bone 5-37 Figure 5.18 The humerus and carpals Trapezium Trapezoid bone Capitate bone Hamate bone

38. Copyright 2008 John Wiley & Sons, Inc. Upper Appendages Metacarpals Metacarpals Phalanges Phalanges 5-38 Figure 5.19 The metacarpels and phalanges

39. Copyright 2008 John Wiley & Sons, Inc. Pelvic girdle Os coxa (hip bone) Os coxa (hip bone) The sacrum and coccyx The sacrum and coccyx Emerges from 3 bones that fuse in early puberty: Emerges from 3 bones that fuse in early puberty: Ilium, ischium, and pubic bone Ilium, ischium, and pubic bone Male and female hip bones are visibly different: Male and female hip bones are visibly different: Female - shallower, broader, enlarged pelvic outlet, wider pelvic inlet and broader pubic angle. Female - shallower, broader, enlarged pelvic outlet, wider pelvic inlet and broader pubic angle. 5-39

40. Copyright 2008 John Wiley & Sons, Inc. Pelvic girdle 5-40 Figure 5.20 Pelvis

41. Copyright 2008 John Wiley & Sons, Inc. Lower Appendages Femur Femur 5-41 Figure 5.22 Femur

42. Copyright 2008 John Wiley & Sons, Inc. Lower Appendages Patella (knee cap) Patella (knee cap) 5-42 Figure 5.24 Patella

43. Copyright 2008 John Wiley & Sons, Inc. Lower Appendages Tibia Tibia Fibula 5-43 Figure 5.25 The fibulaFigure 5.26 The tibia

44. Copyright 2008 John Wiley & Sons, Inc. Lower Appendages Ankle Ankle 7 tarsal bones 7 tarsal bones Calcaneous (heel bone) Calcaneous (heel bone) Talus Talus Navicular Navicular Cuboid Cuboid Lateral cuneiform Lateral cuneiform Intermediate cuneiform Intermediate cuneiform Medial cuneiform Medial cuneiform 5-44 Figure 5.27 The ankle—superior

45. Copyright 2008 John Wiley & Sons, Inc. Lower Appendages Ankle Ankle 7 tarsal bones 7 tarsal bones Calcaneous (heel bone) Calcaneous (heel bone) Talus Talus Navicular Navicular Cuboid Cuboid Lateral cuneiform Lateral cuneiform Intermediate cuneiform Intermediate cuneiform Medial cuneiform Medial cuneiform 5-45 Figure 5.28 The ankle—inferior

46. Copyright 2008 John Wiley & Sons, Inc. Lower Appendages Foot Foot Metatarsal bones Metatarsal bones Phalanges Phalanges 5-46 Figure 5.29 Arches of the foot The arches of the foot are maintained by ligaments and tendons. The arches of the foot are maintained by ligaments and tendons.

47. Copyright 2008 John Wiley & Sons, Inc. Joints Link the Skeletal System Together Joints occur wherever two bones meet. Joints occur wherever two bones meet. Joints can be classified by function or structure. Joints can be classified by function or structure. Functionally: Functionally: Synarthrotic – immovable Synarthrotic – immovable Amphiarthrotic – semimovable Amphiarthrotic – semimovable Diarthrotic – freely movable Diarthrotic – freely movable 5-47

48. Copyright 2008 John Wiley & Sons, Inc. Synarthrotic Joints Bones are fused together, so movement is impossible. Bones are fused together, so movement is impossible. Examples: Examples: Fibrous connections Fibrous connections holding teeth in jaws holding teeth in jaws Coronal suture Coronal suture Sagittal suture Sagittal suture Lamboidal suture Lamboidal suture Squamous suture Squamous suture 5-48 Figure 5.30 Synarthrotic joint

49. Copyright 2008 John Wiley & Sons, Inc. Bones are fused together, so movement is impossible. Bones are fused together, so movement is impossible. Examples: Examples: Fibrous connections Fibrous connections holding teeth in jaws holding teeth in jaws Coronal suture Coronal suture Sagittal suture Sagittal suture Lamboidal suture Lamboidal suture Squamous suture Squamous suture Synarthrotic Joints 5-49 Figure 5.30 Synarthrotic joint

50. Copyright 2008 John Wiley & Sons, Inc. Amphiarthrotic Joints Some movement is possible. Some movement is possible. Examples: Examples: Between adjacent vertebrae Between adjacent vertebrae Between the tibia and fibula (connected by tight ligaments) Between the tibia and fibula (connected by tight ligaments) 5-50 Figure 5.31 Amphiarthrotic joint

51. Copyright 2008 John Wiley & Sons, Inc. Diarthrotic or Synovial Joints Allow free movement between two bones. Allow free movement between two bones. These are the most common joints in the body. These are the most common joints in the body. Supporting structures: Supporting structures: Tendons Tendons Ligaments Ligaments Bursae Bursae Menisci Menisci 5-51 Figure 5.32 Typical Synovial joint

52. Copyright 2008 John Wiley & Sons, Inc. Summary The skeletal system is composed of the axial and appendicular skeleton. The skeletal system is composed of the axial and appendicular skeleton. The adult skeleton contains 206 bones. The adult skeleton contains 206 bones. The skeletal system provides support, protection, allows movement and stores calcium. The skeletal system provides support, protection, allows movement and stores calcium. The skeleton, together with all of its sophisticated joints, provides a framework for movement, but it does not guarantee movement on its own. The skeleton, together with all of its sophisticated joints, provides a framework for movement, but it does not guarantee movement on its own. 5-52