CH 6- Skeletal System

1
CH 6- Skeletal System
2
Fun Bone Facts

• When you were born you had over 300 bones. Now,
  you have 206 bones.
• Over half the body's bones are in the hands and
  feet.
• Not all bones are in connection with another
  bone.
• Your bones are not all solid- store water.
• The smallest bone in the body is the stirrup
  (stapes) in the ear measuring about 3 mm in
  length.
• The longest bone in the body is the femur.

3
Functions of the Skeletal System

• Support forms the structural framework for the
  body.
• Serves as a point of attachment either directly
  or indirectly for the soft tissues of the body.
• Protection protects the vital organs of the
  body.
• Form bony boxes or cages around vital organs like
  the brain, heart and lungs.
• Assists in movement serves as a point of
  attachment for skeletal muscles.
• When a skeletal muscle contracts, it will pull on
  a bone- generating movement. Where muscles
  attach to and pull on bones, bone landmarks are
  formed.

4

• Mineral homeostasis stores minerals such as
  calcium and phosphorus.
• If the levels of these minerals in the blood
  drop, they can be released from the bone into the
  bloodstream. Calcium is essential for bone
  strength as well as muscle contraction.
• Hemopoiesis the production of blood cells.
• Includes red cells, white cells and platelets.
• Happens in the red bone marrow of bone.
• Lipid storage stores lipids for further use.

5
Types of Bones (shapes)
6

• Long bones Longer than they are wide
• Found in the arms and the legs
• Function as levers to generate movement
• Amplify the movement of muscles- 1 inch of travel
  when a skeletal muscle contracts translates to
  much more gross body movement.
• Short bones Square or cube shaped
• Found in the wrists and ankles
• Function to evenly transfer forces from the hands
  and feet to the arms and legs.
• As they receive a force, they shift, causing the
  force transfer to be even.

7

• Flat bones Thin, flat and slightly curved
  (difficult to break)
• Found on the top of the skull and on the ribcage
• Function to protect
• Irregular bones No set shape
• Found in the spine (vertebrae), face and girdles
  (shoulder and hip)
• Function in muscle attachment
• Sesamoid bones Develop inside a tendon
• Found in the kneecap
• Function to protect the tendon of a muscle during
  movement

8
Histology of Bone Tissue

• Classified as a connective tissue contains an
  abundant extracellular matrix that surrounds
  widely spaced cells.
• Composed of
• 98 matrix
• 50 inorganic minerals (mainly Ca and P)
• 25 protein fibers (mainly collagen that allows
  the bone to bend a little before it breaks)
• 23 water

9
Bone cells- 2 of bone tissue

• Osteogenic cells unspecified stem cells that are
  found within developing bone
• As they mature, they will change in structure and
  function (differentiate)
• Osteoblasts bone forming cells
• Differentiated osteogenic cells
• Responsible for removing minerals from the blood
  and placing them into the developing bone matrix
  (like brick layers). This walls them off from
  neighboring cells.

10
Bone cells- 2 of bone tissue

• Osteocytes mature bone cells
• Differentiated osteoblasts
• Maintain the matrix of an area of bone tissue
• Osteoclasts Bone destroying cells
• Contain powerful digestive enzymes that can break
  down the matrix of bone tissue
• Releases minerals into the blood
• Helps with the healing process by smoothing edges
  of a fracture so the osteoblasts can fill in the
  gap.

11
(No Transcript)
12
Types of Bone Tissue

• Compact bone tissue forms the external layer of
  all bones.
• Function
• Provides strength and rigidity to the bone
• Helps bones resist force
• Structure
• Composed of smaller columns of bone matrix held
  together by more matrix (adds to its strength)

13
Compact Bone Structure cont

• Osteons the structural unit of compact bone
  (bone columns)
• Features
• Lacunae spaces within the osteons that contain
  osteocytes.
• One osteocyte per lacuna which maintains the
  matrix around that lacuna.
• Canaliculi the small spaces extending from the
  lacunae.
• Connect neighboring lacunae so the osteocytes can
  transfer materials (oxygen nutrients) between
  one another.

14

• Perforating canals horizontal canals that pass
  through compact bone.
• These run perpendicular to the osteon and let
  blood vessels and nerves to travel transversely
  in bone.
• Haversian canals vertical canals that pass
  through compact bone.
• These are at the center of every osteon and run
  parallel to the osteon. They allow blood vessels
  and nerves to travel the length of the bone.

15
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
(No Transcript)
19
Spongy Bone (Cancellous)

• Forms the internal structure of all bones.
• Structure Hard and not solid (airy)
• Function
• Increases the strength without increasing its
  weight.
• Trabeculae an irregular lattice of thin columns
  of bone organized along stress lines within bone.
• Hollow spaces between trabeculae are filled with
  red bone marrow.
• These thin columns fracture fairly easily
  however, when they rebuild themselves, they are
  stronger and re-oriented to resist future force.

20
(No Transcript)
21
(No Transcript)
22
(No Transcript)
23
ACT-UP
24
ACT-UP

• 1) Describe the differences, if any, between the
  normal bone slide and the slide showing the bone
  affected by osteoporosis.
• 2) List at least two (2) physical signs that
  someone might be suffering from osteoporosis.
• 3) List at least two (2) potential causes of
  osteoporosis.
• 4) List at least two (2) things a person can do
  to help stop osteoporosis.

25
Compare the slides of normal bone tissue on the
left and bone affected by osteoporosis on the
right. Then answer the following questions.
Normal Bone
Bone suffering from osteoporosis
26
(No Transcript)
27
The Anatomy of a Bone

• The long bone is used as the example when
  studying the anatomy of bone because all features
  are easily identifiable.
• The features are
• Diaphysis the shaft of a long bone.
• Functions to provide the strength to the bone
  because it contains a thick layer of compact bone
  and a thin layer of spongy bone.
• Epiphyses (es is plural is is singular) the
  ends of a long bone.
• Function to form a joint and are rounded to allow
  joint formation. These are mainly composed of
  spongy bone.

28

• Proximal epiphysis
• The end of the long bone that is closest to the
  trunk of the body.
• Distal epiphysis
• The end of the long bone furthest from the trunk
  of the body.
• Metaphyses the regions found between the
  epiphyses and the diaphysis of a long bone.
• Function depends on the age of the bone.
• Epiphyseal plate the name given to the
  metaphyses in a developing bone.
• Made entirely of hyaline cartilage and allows for
  the lengthwise growth of bone.
• Called the growth plate and is not visible on
  x-rays.

29
(No Transcript)
30
(No Transcript)
31

• Epiphyseal line the name given to the metaphyses
  in a mature bone.
• Once this is formed, bone growth stops because
  the raw material (cartilage) has been converted
  to bone.
• Articular cartilage a thin layer of hyaline
  cartilage found covering the ends of bones
  (epiphyses) forming a joint.
• Functions as a shock absorber to protect the ends
  of bones.
• As we age, the cartilage breaks down and wears
  away.

32

• Periosteum a thin layer of dense irregular
  connective tissue that covers all surfaces of a
  bone not covered by articular cartilage.
• Functions to protect blood vessels and nerves and
  is a point of attachment for muscle tendons.
• Because it is dense irregular, the collagen
  fibers running in different directions can resist
  any force from muscle contraction.
• Medullary cavity a hollow space found within the
  diaphysis of a long bone.
• Function depends on the age of the bone (either
  contains red or yellow bone marrow.

33

• Red bone marrow
• Produces blood cells (hemopoiesis)
• Fills the medullary cavity of younger individuals
  because they are growing and have a higher
  metabolic need (need more oxygen so need more red
  blood cells).
• Yellow bone marrow
• Energy reserve (stores fat)
• Found in the medullary cavity of most adult bones
• Endosteum a thin layer of fibrous connective
  tissue found lining the medullary cavity that
  holds the bone marrow in place.
• Nutrient foramen small openings found throughout
  compact bone that allow blood vessels and nerves
  to enter the bone tissue.

34
(No Transcript)
35
(No Transcript)
36
Anatomy of a Long Bone
37
Bone Formation

• Ossification the process responsible for
  converting connective tissue into bone.
• There are two different types of ossification
  that occur in the body
• Intramembranous ossification the formation of
  bones from fibrous connective tissue
  (mesenchyme).
• Occurs in flat bones like the skull
• The tissue is arranged in sheets called
  ossification centers and the process starts at
  the center of the sheet and works it way
  outwards.
• Begins before birth and doesnt finish until
  mid-teens
• The reason for a babys soft spot

38
Bone Formation

• Endochondral ossification the formation of bones
  from hyaline cartilage.
• Forms all bones except flat bones.
• Begins before birth in the center of the
  diaphysis (primary ossification center).
• Continues shortly after birth in the epiphyses
  (secondary ossification center).
• The growing regions meet at the epiphyseal plate,
  forcing the bone to grow lengthwise.

39
(No Transcript)
40
Bone Surface Markings

• Depressions and openings
• Fissure Narrow slit between adjacent parts of
  bones through which blood vessels or nerves pass
• Foramen Opening through which blood vessels,
  nerves or ligaments pass
• Fossa Shallow depression
• Sulcus Furrow along a bone surface that
  accomodates blood vessels, nerves or tendons.
• Meatus Tube-like opening

41
Fissure
42
Foramen
43
Fossa
44
Sulcus
45
Meatus
46
Bone Surface Markings

• Processes that form joints
• Condyle Large, round protuberance with a smooth
  articular surface at the end of bone
• Facet Smooth, flat, slightly concave or convex
  articular surface
• Head Usually rounded articular projection
  supported by a constricted portion (neck) of the
  bone

47
Condyle
48
Facet
49
Head
50

• Processes that form points of attachment for
  connective tissues
• Crest Prominent ridge or elongated projection
• Epicondyle Typically roughened projection above
  a condyle
• Line Long narrow ridge or border that is less
  prominent than a crest
• Spinous process Sharp, slender projection
• Trochanter Large projection
• Tuberosity Variable sized projection that is
  rough and bumpy
• Tubercle Variable sized rounded projection

51
Crest
52
Epicondyle
53
Line
54
Spinous Process
55
Trochanter
Femur
56
Tuberosity
57
Tubercle
58
Bone Surface Markings Practice

1. Fissure
2. Foramen
3. Fossa
4. Sulcus
5. Meatus
6. Condyle
7. Facet
8. Head
9. Crest

• J. Epicondyle
• K. Line
• L. Spinous process
• M. Trochanter
• N. Tuberosity
• O. Tubercle