1. The Skeletal System

2. Copy this chart on the top 1/3 of your paper and write as many things as you can about the following terms
Skeleton
Bones
Skeletal System

3. THE SKELETAL SYSTEM - NOTES
Skeletal System Parts:
bones, cartilage, tendons, ligaments
Functions:
maintain body shape - support
protects organs
provides levers for movement
mineral and fat storage
blood cell formation

4. Skeletal System connective tissues:
living cells in a matrix
LIVING CELLS
MATRIX
bone cells
calcium, phosphorus, collagen
cartilage cells
collagen and ground tissue
tendons & ligaments
parallel collagen fibers

5. Skeletal Cartilages Hyaline Cartilage – most abundant Frosted glass
Support with flexibility and resilience
Fine collagen fibers in matrix
Articular, costal, respiratory, nasal

6. Skeletal Cartilage
Elastic – resembles hyaline but has elastic fibers. External ear and epiglottis.
Fibrocartilage – highly compressible with great strength. Seen in areas with pressure and stretch – pad like cartilages. Menisci in knee, discs between vertebrae.

7. Parts of the skeleton Axial Skeleton Appendicular Skeleton
skull, spine, rib cage
Appendicular Skeleton
upper and lower limbs and girdles (shoulders and hips)

8. Bone Classification by Shape
LONG BONE
EX: humerus

9. SHORT BONE
EX: trapezoid (bone in wrist)

10. FLAT BONE
EX: sternum

11. IRREGULAR BONE
EX: vertebra

12. SESAMOID BONE
patella (knee cap)

13. Anatomical Features of Long Bones
DIAPHYSIS
shaft
EPIPHYSIS
end of the bone
EPIPHYSEAL PLATE (or EPIPHYSEAL LINE)
site of bone growth – bones grow from their ends
epiphyseal plate
epiphysis
diaphysis

15. MEDULLARY CAVITY
location:
in diaphysis
filled with yellow marrow (adipose tissue)

16. PERIOSTEUM
outer covering of bone – tough connective tissue (dense irregular)
contains blood vessels & nerves
Inner layer – osteogenic cells

17. Anatomical Features of COMPACT BONE
location: diaphysis
solid matrix & tightly packed cells
made up of OSTEONS or HAVERSIAN SYSTEMS

19. Microscopic Anatomy of Bone
Figure 5.3a

20. Microscopic Anatomy of Bone
Figure 5.3b–c

21. OSTEOCYTES
bone cells – supplied by Haversian Canals with blood
CANALICULI
tiny canals that connect osteocytes together
thin rings of bone that serve to anchor bone cells
LAMELLAE

22. Anatomical Features of SPONGY BONE
bone is not really “spongy” or soft, it only “looks” spongy
Location:
epiphysis
made of TRABECULAE
interconnecting rods of bone

23. spaces in trabeculae filled w/red marrow
no Haversian Canals
lighter than compact bone

25. Cell Types Osteogenic cells – mitotically active cells in periosteum
Osteoblasts – bone-forming cells that secrete bone matrix.
Osteocytes – mature bone cells that occupy spaces (lacunae)
Osteoclasts – giant cells – job is bone resorption

26. BONE MARROW
cells produced from within bones
red marrow
produces blood cells
yellow marrow
adipose tissue – stores fat (energy)

28. Bone Markings Projections, depressions, and openings on the bones.
Sites of muscle, ligament
and tendon attachment.

29. Formation of the Human Skeleton
In embryos, the skeleton is primarily hyaline cartilage
During development, much of this cartilage is replaced by bone
Cartilage remains in isolated areas
Bridge of the nose
Parts of ribs
Joints

30. Developmental Aspects of the Skeletal System
At birth, the skull bones are incomplete
Bones are joined by fibrous membranes called fontanelles
Fontanelles are completely replaced with bone within two years after birth

31. Ossification Centers in a 12-week-old Fetus
Figure 5.32

32. Figure 6.17 Fetal primary ossification centers at 12 weeks.
Parietal
bone
Frontal
bone
of skull
Occipital
bone
Mandible
Clavicle
Scapula
Radius
Ulna
Humerus
Femur
Tibia
Ribs
Vertebra
Ilium
© 2013 Pearson Education, Inc.

33. Skeletal Changes Throughout Life
Fetus
Long bones are formed of hyaline cartilage
Flat bones begin as fibrous membranes
Flat and long bone models are converted to bone
Birth
Fontanels remain until around age 2

34. Skeletal Changes Throughout Life
Adolescence
Epiphyseal plates become ossified and long bone growth ends
Size of cranium in relationship to body
2 years old—skull is larger in proportion to the body compared to that of an adult
8 or 9 years old—skull is near adult size and proportion
Between ages 6 and 11, the face grows out from the skull

35. Skeletal Changes Throughout Life
Figure 5.33a

36. The Fetal Skull
The fetal skull is large compared to the infant’s total body length
Fontanels—fibrous membranes connecting the cranial bones
Allow the brain to grow
Convert to bone within 24 months after birth

37. The Fetal Skull
Figure 5.13a

38. The Fetal Skull
Figure 5.13b

39. Skeletal Changes Throughout Life
Curvatures of the spine
Primary curvatures are present at birth and are convex posteriorly
Secondary curvatures are associated with a child’s later development and are convex anteriorly
Abnormal spinal curvatures (scoliosis and lordosis) are often congenital

40. The Vertebral Column
Figure 5.15

41. Bone Growth (Ossification)
Epiphyseal plates allow for lengthwise growth of long bones during childhood
New cartilage is continuously formed
Older cartilage becomes ossified
Cartilage is broken down
Enclosed cartilage is digested away, opening up a medullary cavity
Bone replaces cartilage through the action of osteoblasts

42. Bone Growth (Ossification)
Bones are remodeled and lengthened until growth stops
Bones are remodeled in response to two factors
Blood calcium levels
Pull of gravity and muscles on the skeleton
Bones grow in width (called appositional growth)

43. Long Bone Formation and Growth
Bone starting to replace cartilage
Epiphyseal plate cartilage
Articular cartilage
Spongy bone
In a child
In a fetus
In an embryo
New bone forming
Growth in bone width
Growth in bone length
Blood vessels
Hyaline cartilage
New center of bone growth
Medullary cavity
Bone collar
Hyaline cartilage model
(a)
Figure 5.4a

44. Long Bone Formation and Growth
Bone starting to replace cartilage
In an embryo
Bone collar
Hyaline cartilage model
(a)
Figure 5.4a, step 1

45. Long Bone Formation and Growth
Bone starting to replace cartilage
In a fetus
In an embryo
Growth in bone length
Blood vessels
Hyaline cartilage
New center of bone growth
Medullary cavity
Bone collar
Hyaline cartilage model
(a)
Figure 5.4a, step 2

46. Long Bone Formation and Growth
Bone starting to replace cartilage
Epiphyseal plate cartilage
Articular cartilage
Spongy bone
In a child
In a fetus
In an embryo
New bone forming
Growth in bone width
Growth in bone length
Blood vessels
Hyaline cartilage
New center of bone growth
Medullary cavity
Bone collar
Hyaline cartilage model
(a)
Figure 5.4a, step 3

48. Cartilage cells undergo mitosis.
Figure Growth in length of a long bone occurs at the epiphyseal plate.
Resting zone
1 Proliferation zone
Cartilage cells undergo
mitosis.
2 Hypertrophic zone
Older cartilage cells
enlarge.
3 Calcification zone
Matrix calcifies; cartilage
cells die; matrix begins
deteriorating; blood
vessels invade
cavity.
Calcified
cartilage spicule
Osteoblast
depositing bone
matrix
Osseous tissue
(bone) covering
cartilage spicules
4 Ossification zone
New bone forms.
© 2013 Pearson Education, Inc.

49. Long Bone Formation and Growth
Figure 5.4b