1. Skeletal System Chapter 7

2. Types of Bones (by shape)
Long-arm and leg bones
Short-”cubelike”-carpals, tarsals
Flat-ribs, scapula, some skull
Irregular-vertebrae, facial
Sesamoid-round- embedded in tendon or ligament-kneecap

4. Parts of a Long Bone Epiphysis-knob at each end Diaphysis-shaft
Articular Cartilage-hyaline cartilage covering end of epiphyses
Periosteum-fibrous CT covering bone-has blood vessels
Medullary Cavity-opening which runs length of diaphysis-filled with yellow marrow

5. Compact Bone Tissue-surrounds medullary cavity
Spongy Bone (Cancellous) Tissue-has spaces filled with red marrow-located in epiphyses
Endosteum-squamous tissue lining medullary cavity and spaces in spongy bone

9. Microscopic Structure of Bone
Compact Bone
osteonic systems
Haversian (osteonic canals)
lacunae with osteocytes
lamellae
canaliculi
Cancellous Bone
no osteonic systems
plates of bone called TRABECULAE
lacunae with osteocytes
canaliculi

11. Bone Growth and Development
Bones form by replacing existing connective tissue in one of two ways;
1. Intramembranous ossification - bones begin as sheetlike layers of fibrous c. t. .-see steps in Table 7.1, pg 198
2. Endochondral ossification - bones begin as models of hyaline cartilage

13. Endochondral Ossification
Primary Center of Ossification (in middle of diaphysis)-osteoblasts and blood vessels invade disintegrating cartilage - osteoblasts lay down spongy bone
Osteoblasts from periosteum lay down compact bone around primary center (thick)

14. Osteoclasts carve out medullary cavity
Cartilage disintegrates in secondary centers of ossification (in epiphyses) and osteoblasts lay down spongy bone there
The area of cartilage between primary and secondary centers of oss. is called the epiphyseal plate/disk (as long as it is present, the bone grows in length) When centers meet, growth in length stops
Bone thickness is due to laying down of compact bone under the periosteum

17. Figure 07.11

18. Osteoporosis animation

19. Factors affecting bone growth and development
Vitamin D(some is stored in skin and activated by sunlight) - necessary for absorption of calcium from small intestine- a deficiency in children results in rickets; deficiency in adults-->osteomalacea (bone softening)
Vitamin A - for bone resorption (osteoclast activity) - deficiency results in retardation of bone development

20. Ossification video

21. Vitamin C - needed for collagen synthesis-deficiency results in too little collagen in bone matrix-->thin, fragile bones
Thyroid hormone-stimulates replacement of cartilage by bone-too much in child--->stunted growth (premature ossification of epiphyseal plates)
Growth hormone-(pituitary gland) stimulates mitotic division of cartilage in epi. plates-deficiency in child-->pituitary dwarfism;too much in child-->giantism; too much in adult--> acromegaly

23. Sex hormones (estrogens and androgens) - increase bone growth and stimulate ossification of epi. plates (especially estrogens)
Physical stress - pull from muscles- stimulates bone tissue to thicken and strengthen (hypertrophy)---lack of exercise causes bone atrophy (become thinner and weaker)

25. Bone Functions Support & protection Lever System (with muscles)
Blood cell formation (hematopoiesis) -
in early embryo-yolk sac, then liver & spleen, then red marrow
in infant- red marrow (found in most places in bone) Later, some red marrow is replaced by yellow marrow which is for fat storage
in adult-red marrow (mostly in spongy bone of skull, ribs, clavicle, scapula, vertebrae, hip)

26. Storage of salts - most stored as crystals of CaPO4 called hydroxyapetite (Ca++ is important not only in bone hardness, but also in blood clotting, nerve impulse, muscle contraction
Low blood Ca++ triggers osteoclast activity
High blood Ca++ triggers osteoblast activity
Other salts contain Mg, Na, K,
Abnormal storage-lead, strontium, radium

27. Skeletal Organization
Axial skeleton-skull, vertebral column, hyoid, ribs, sternum
Appendicular skeleton-pectoral and pelvic girdles, limbs

29. Differences in Male and Female Skeletons
Male-heavier, more dense, with more muscle attachments; pelvis is narrower, angle of pubic arch is smaller
Female-lighter, less dense, fewer muscle attachments; pelvis is more flared, with larger opening and bigger pubic arch angle

31. Vertebral Column
Normal curvatures: cervical, thoracic, lumbar, and pelvic

32. Abnormal Curvatures
Kyphosis (hunchback) - excessive thoracic curvature
Scoliosis - lateral curvature
Lordosis (swayback) - excessive lumbar curvature

33. Other Vertebral Column Disorders
Ruptured (herniated) disk - can occur when outer part of intervertebral disk becomes thinner, and inner mass loses firmness - crack occurs in outer, and inner mass oozes out, pressing on nerve
Degenerative disk-disks become smaller, more rigid and weaker with age--person becomes shorter--fractures occur more easily