Chapters 6 & 7. The Skeletal System. Our bones

Transcription

1 Chapters 6 & 7 The Skeletal System Our bones The human skeleton has 206 bones, which are divided into 4 types: 1. Long 2. Short 3. Flat 4. irregular 1

2 Long bones In the arms and legs Femur Ulna Tibia Humerus Short bones In wrists and ankles Kneecap (patella) Cube-shaped 2

3 Flat bones Ribs Sternum Pelvis cranium Vertebrae sacrum Irregular bones 3

4 About 50% of our bones are in the hands and feet 2 major divisions 1) Axial skeleton -- bones of head, neck and trunk 4

5 2) Appendicular skeleton bones of limbs and bones that attach limbs to trunk Ribs We have 12 pairs of ribs The false ribs (ribs 8-12, the most inferior ribs) don t connect directly with the sternum Ribs 8,9 and 10 connect (articulate) indirectly, but ribs 11 and 12 don t connect at all. They re called floating ribs. 5

6 The vertebral column 4 divisions: 1. Cervical vertebrae (C1-C7) 2. Thoracic vertebrae (T1-T12) 3. Lumbar vertebrae (L1-L5) 4. Sacrum (S1-S5, fused into a single structure called the sacrum) 6

7 Curves of the vertebral column The vertebral column has 4 curves which act as shock absorbers. 7

8 C1 (Atlas) vertebra Holds up head Flattened area articulates (connects with) flattened area on skull, Joint allows us to nod head C2 (Axis) Has a tooth-like process (dens) which articulates with atlas, joint allows us to shake head Fatal whiplash often involves this process poking through brain stem 8

9 Features of the vertebrae Body -- Carries your weight Intervertebral disks Cartilage body with gel-like fluid center Functions: Provide cushions between bodies of vertebrae Provide flexibility to vertebral column 9

10 Intervertebral disks Can rupture or herniate Vertebral arch Surrounds and protects contents of vertebral foramen Vertebral foramen is canal containing spinal cord 10

11 Processes Spinous Transverse Spiny projections from arch Provide place to attach muscles which bend vertebral column Articular facets Superior and inferior Flat smooth place on vertebra where it articulates with (joins to) another vertebra 11

12 Costal articular facets Additional flat smooth places on thoracic vertebrae where the vertebrae articulate with ribs costal means rib Intervertebral foramen Foramen means hole Holes formed by notch on each side of inferior part of vertebral arch 12

13 The skull has 22 bones, which are fused in adults. Functions of the Skeletal System 1. Support and aid in movement 2. Protection 3. Blood cell production 4. Storage of minerals and fat 13

14 1. Support and aid in movement: bones provide attachments for muscles to pull against 2. Protection -- brain, lungs, heart, spinal column 14

15 3. Production of blood cells Known as hematopoiesis Occurs in red bone marrow 4. Storage a) In adults, marrow cavity of long bones is filled with yellow marrow which is adipose tissue (fat) 15

16 4. Storage b) Storage of inorganic salts, especially calcium and phosphorus Calcium storage The body s storage of calcium and its release into the blood are determined by the concentration of calcium ions in the blood. When this concentration is low, osteoclasts are stimulated to break down bone. When it is high, osteoblasts are stimulated to build up bone. 16

17 Bones and pregnancy This process can affect a pregnant woman who doesn t eat enough calcium because the baby s need for calcium will lower the level of calcium in her blood. Then her body will break down bone to restore the proper level. If her diet continues to be deficient in calcium, she will continue to lose bone to supply the baby s need for calcium. Phosphorus The element that helps make bones strong (so strong that they are harder to break than concrete) is phosporus, which can be dissolved by vinegar. 17

18 articulations Fancy word for joints Come in three types: Synarthroses Amphiarthroses Diarthroses synarthroses Bones unable to move Examples: skull 18

19 amphiarthroses Allow limited movement Examples: vertebrae Also synovial joints (separated by synovial space) 6 types: Gliding such as clavicle and scapula Hinge such as femur and tibia Pivot such as atlas and axis Ellipsoidal/condyloid such as radius & carpals Saddle such as metacarpal at thumb Ball and socket such as hip diarthrosis 19

20 Joints provide many movements Abduction -- move away from midline Adduction -- move toward midline Flexion -- bending joint Extension -- straightening joint Rotation -- turning head Lateral rotation turns head to side Medial rotation turns head back to the front Supination and pronation possible because of 2 bones in lower arm Supination -- turn palm up to sky Pronation -- turn palm toward ground 20

21 Joint between bones lined with cartilage Cartilage provides smooth surface Acts as shock absorber Has outer layer of connective tissue Cavity filled with synovial fluid Fluid lubricates Fluid nourishes cartilage Joint capsule 21

22 Macroscopic bone structure Epiphysis -- expanded end of long bone Covered with thin layers of dense bone Mostly filled with spongy bone Metaphysis -- where diaphysis and epiphysis meet Diaphysis -- cylinder in between epiphysis and diaphysis, straight end of long bone 22

23 Anatomy of diaphysis Walls are dense bone Cavity inside is medullary or marrow cavity, which is filled with marrow: red marrow, which produces blood cells; found in younger people yellow marrow, which replaces red as people as people age Yellow marrow STORES fat periosteum Periosteum -- membrane that covers surface of bones 2 layers: Superficial (outer) layer Glistening white Allows for attachment of ligaments and tendons to bone Deep (inner)layer Adjacent to bone tissue Provides bone with replacement osteoblasts as needed 23

24 Bone diseases at end Bone weight Bones are not solid. The medullary cavity and spongy bone hold marrow, which is less dense than dense bone. 24

25 Because of this less dense portion of the bone, bone makes up only about 15% of the average body s weight. A cylinder of dense bone with a larger diameter and with a less dense material in the middle is stronger than the same amount of dense bone made into a solid cylinder with a smaller diameter. It s alive!» That is, your bones are» alive! 25

26 3 type of bone cells: Osteoblasts Osteocytes Osteoclasts What on earth are these things?? Osteoblasts Cells that produce bone They secrete the bone matrix (a gel-like substance) in vesicles all around themselves 26

27 Osteoblasts surrounded! Gel turns into a harder substance by attracting calcium and phosphate compounds ( mineralization ) Process continues until osteoblasts are surrounded Come out with your hands up! Osteocytes Trapped osteoblasts are in cavity called lacuna ( little lake ) Can t produce any more matrix because there s nowhere to put it so differentiate into osteocytes -- the maintainers of bone 27

28 Osteoclasts Break down bone When is bone broken down? To release minerals when they re needed To rebuild and repair after recycling material in old bone ( remodeling ) Dense bone Dense bone (or compact bone) is found in the diaphyses of our long bones It makes up the outer part of the bone shafts. 28

29 Dense Bone structure Dense bone made up of cylinders (osteon or Haversian units) cemented together The center of these cylinders is called the central or Haversian canal. It contains blood vessels and nerves (No wonder it hurts to break a bone!) Structure due to osteoblasts Layers of calcified bone matrix surround the central canals. The osteoblasts produce these layers, which are called lamellae In between lamellae are lacunae ( little lakes ) which contain osteoblasts 29

30 More about bone structure The bone cells reach out to each other with cell membrane projections (like they re holding hands) The projections are threaded through tiny canals called canaliculi The canaliculi and lacuna are filled with interstitial fluid Interstitial fluid bathes the cells and allows nutrients, oxygen, and wastes to diffuse to and from the blood in the central canal Volkmann s canals Volkmann s canals (or perforating canals) connect the central canals. These carry blood vessels from the exterior of the bone to the central canals and to the medullary (marrow) cavity. 30

31 Because of these connections, materials can move back and forth quickly between the blood and bone cells. 31

32 Bone vs. cartilage Because the bone cells have such easy access to blood, bone heals much faster than cartilage. Spongy bone Spongy bone, like dense bone, contains osteocytes Spongy bone is not arranged in osteons Gets its name because it contains many tiny spaces (like a sponge) Spaces filled with red marrow which produces blood (hematopoeisis) Spaces also make bone lighter Found in epiphyses of long bones and in inner layer of flat bones 32

33 Bone matrix Bone matrix is made of: 1. Collagen fiber, which makes the bone strong and resilient 2. Mineral salts (Ca and P salts) which make the bone strong and resistant to crushing Osteogenesis Definition: Formation of bone Starts with formation of cartilage or connective tissue which is then replaced by bone 33

34 Bone Growth Growth in length occurs at epiphyseal plate (growth plate) Growth plate produces cartilage which is later replaced by bone Growth stops when plate replaced by bone (called closure of epiphyseal plate ) Growth in diameter requires osteoclasts to widen medullary cavity Remodeling See worksheet Can result in overlapping osteons (below) 34

35 Every year, >10% of our skeleton is replaced in remodeling. (The younger we are, the faster it s replaced.) Osteoclasts remove bone tissue and osteoblasts build up the bone. (Osteoblasts function is to dissolve bone.) An example of remodeling is the bones of runners, which become thicker and stronger with exercise. Types of fractures Green stick -- one side of bone broken, other is bent Spiral -- twisted Comminuted -- many fragments Compression fracture is usually comminuted Transverse -- like a transverse section Compound -- bone sticks through skin Oblique -- breaks at an angle 35

36 Healing of fractures See your book, page 98, to fill out this portion of the outline. 36

37 Carpal tunnel syndrome In carpal tunnel syndrome, there is pressure on the median nerve of the wrist. Repetitive motion of the wrist joint and bone spurs are two possible causes. scoliosis In scoliosis, the spine is curved in an unnatural manner. 37

38 Arthritis Painful inflammation and swelling of joints Scurvy Caused by lack of vitamin C Weakens collagen in tissues, bones, and blood vessels Symptoms include: Bleeding into periosteum, muscles and joints, causing pain Swollen and bleeding gums Easy bruising 38

39 Rickets Due to lack of vitamin D Leads to softening of bones Symptoms include: Bone pain or tenderness Skeletal deformities Impaired growth Increased tendency toward fractures Osteoporosis Bones are weakened by loss of bone mass, which causes spaces to form in the bones. 39

40 Herniated disk Also called prolapsed or bulging disk The elastic inner core of the disk squeezes out of a crack in the disk. The change in shape can put pressure on the spinal cord or nerves. ACL Anterior cruciate ligament (in knee) This ligament can be torn by sudden turns or by landing hard from a jump without bending the knee. Female athletes can reduce their risk by keeping their knees bent when landing or turning and by increasing their core and hamstring strength. More to come in an ACL powerpoint 40

41 Comparing the elbow and knee The elbow joint is less complicated than the knee joint because it is connected with fewer ligaments, has no cartilage menisci separating the bones, and has no patella bone covering it. (See the models in class.) Comparing the hip and shoulder The hip joint s bones are held together more tightly than the bones of the shoulder. Because of this, the hip is the stronger joint, but the shoulder is more flexible. Form follows function!! Again, see the models. 41