Chapter 6: Skeletal System Flashcards
1
Q
What does the skeletal system include?
A
Bones, joints, and associated supporting tissues
2
Q
Bones
A
- Main organs of the system
- Composed of more than osseous tissue
- Also has dense regular, irregular collagenous connective tissue, and bone marrow
3
Q
Functions of the skeletal system
A
- Protection
- Mineral storage
- Acid-base homeostasis
- Blood cell formation
- Fat storage
- Movement
- Support
4
Q
Protection
A
The skeleton protects vital organs such as the brain
5
Q
Mineral storage and acid-base homeostasis
A
Bone stores minerals such as Ca2+ and PO4(3-), which are necessary for electrolyte and acid-base balance
6
Q
Blood cell formation
A
Red bone marrow is the site of blood cell formation
7
Q
Fat storage
A
Yellow bone marrow stores triglycerides
8
Q
Movement
A
Muscles produce body movement via their attachment to bones
9
Q
Support
A
The skeleton supports the weight of the body
10
Q
Bone shapes
A
- Long bone
- Flat bone
- Short bone
- Irregular bone
- Sesamoid bone
- Sutural (Worminan) bone
11
Q
Long bone
A
- Elongated shape
- Most limb bones
12
Q
Flat bone
A
- Thin, flat
- Cranium, ribs, sternum
13
Q
Short bone
A
- Cube-shaped
- Carpals, tarsals
14
Q
Irregular bone
A
- Various shapes
- Vertebra, hip, coccyx
15
Q
Sesamoid bone
A
- Small, flat, like a sesame seed
- Forms within tendons
- Patella
16
Q
Sutural (Worminan) bone
A
- Small, flat, irregular shape
- Forms between bones of the skull at sutures
17
Q
Parts of a long bone
A
- Periosteum
- Endosteum
- Diaphysis
- Metaphysis
- Epiphysis
- Epiphyseal plate
- Epiphyseal line
- Medullary cavity
18
Q
Periosteum
A
- Outer covering
- Consists of dense irregular connective tissue
- Inside is a single layer of bone cells which contain osteoblasts, nerves, blood vessels, and osteochondral progenitor cells
- Fibers of tendon become continuous with fibers of periosteum
- Sharpey’s fibers
19
Q
Sharpey’s Fibers
A
- Some periosteal fibers penetrate through the periosteum and into the bone
- This strengthens the attachment of tendon to bone
20
Q
Endosteum
A
- Lines medullary cavity
- Has a layer of osteoprogenitor cells
21
Q
Osteoprogenitor cells
A
Stem cells that produce osteoblasts
22
Q
Diaphysis
A
Shaft of bone made out of compact bone
23
Q
Metaphysis
A
Narrow zone where diaphysis connects to epiphysis
24
Q
Epiphysis
A
- End of bone
- Cancellous bone (spongy bone)
25
Epiphyseal plate
- Growth plate
- Its presence means the bone is still growing
- Hyaline cartilage
- Present until growth stops
26
Epiphyseal line
Present when bone stops growing in length
27
Medullary cavity
- Red marrow in children
- Gradually changes to yellow in limb bones and skull
- Not in long bones
- Rest of skeleton is red
28
Diploe
- Flat bones do not have a marrow cavity
| - Instead they have a diploe
29
Types of bone structure
- Compact bone
| - Cancellous (spongy) bone
30
Compact Bone
- Hard, dense outer region
| - Allows bone to resist linear compression, twisting, and other stresses
31
Cancellous Bone
- Inside cortical (compact) bone
- Honeycomb-like framework of bony struts
- Allows bones to resist forces from many directions
- Provides cavity for bone marrow
- Made of trabeculae
32
Types of bone marrow
- Red bone marrow
| - Yellow bone marrow
33
Red Bone Marrow
- Loose connective tissue
- Supports islands of blood-forming hematopoietic cells
- Decreases with age
- Only present in the pelvis with adults
34
Why do children have more bone marrow?
They need more of it to assist with growth and development
35
Yellow Bone Marrow
Composed of triglycerides, blood vessels, and adipocytes
36
Bone Matrix
-
37
Bone cells
- Osteoblasts
- Osteocytes
- Osteoclasts
- Stem cells/osteochondral progenitor cells
38
Osteoblasts
Make bone
39
Osteocytes
Mature bone cells
40
Osteoclasts
- Break down bone
41
Stem cells/osteochondral progenitor cells
Become chondroblasts or osteoblasts
42
Woven Bone
Collagen fibers are randomly oriented
43
Lamellar Bone
Mature bone in sheets
44
Ruffled border
Where cell membrane borders bone and resorption is taking place
45
How to osteoclasts reabsorb bone?
- H+ ions are pumped across the membrane
- Acid forms, eating away bone
- Enzymes are released that digest the bone
46
Osteon
- The unit of compact bone structure
- Also called a Haversian system
- Consists of concentric rings
47
Osteon Structure
- Concentric lamellae
- Interstitial lamellae
- Circumferential lamellae
- Perforating (Volkmann's) canals
48
Concentric Lamellae
- Thin layers of bone that make up the rings found in an osteon
- 4-20 in each osteon
49
Interstitial lamellae
- Fills spaces between circular osteons
| - Represent remnants of old osteons
50
Circumferential lamellae
- Outer and inner layers of lamellae just inside periosteium
- Found at the boundary with spongy bone
- Adds strength
51
Perforating (Volkmann's) canals
- Originate from blood vessels in periosteum
- Perpendicular to central canals of neighboring osteons
- Connects osteons
52
Trabeculae
- Struts or ribs of bone
- Covered with endosteum
- Usually not arranged into osteons
- Communicate through calaiculi
53
What are trabeculae made of?
Concentric lamellae with osteocytes in lacunae
54
How do trabeculae communicate?
Through canaliculi
55
How does spongy bone get blood?
- There are no central canals to supply blood
| - Obtain blood from vessels in bone marrow
56
Types of bone development
- Intramembranous ossification
- Encochondral ossification
- Both methods produce woven bone that is then remodeled
- After remodeling, bone is indistinguishable
57
Intramembranous ossification
Take place in connective tissue membrane
58
Encochondral ossification
Take place in cartilage
59
Ossification
The process of bone formation
60
When does ossification begin?
- In the embryonic period
| - Continues through childhood, with most bones completing formation by age 7
61
Mechanisms for ossification
- First bone formed is immature primary (woven) bone
| - Usually primary bone is broken down by osteoclasts and replaced with mature secondary bone
62
Immature Primary Bone
Irregularly arranged collagen bundles, osteocytes, and sparse inorganic matrix
63
Mature Secondary bone
- Lamellar bone
| - More inorganic matrix and increased strength
64
What bones does intramembranous ossification make?
Many flat bones (skull and clavicles) during fetal development
65
Fetal primary bone
- Formed within mesenchymal membrane
- Composed of embryonic connective tissue
- Rich in blood
66
Flat bone structure
2 outer layers of compact bone with layer of spongy bone in the middle
67
Order of ossification for flat bones
- Spongy middle layer first
| - Begins from primary ossification center
68
Progression of mesenchymal cells
They differentiate into osteogenic cells, then osteoblasts, at the primary ossification site
69
How many primary ossification centers do larger bones have?
- More than one
| - These lead to pieces of bone that fuse together over time
70
Which bones undergo endochondral ossification?
All bones below the head except clavicles
71
When does endochondral ossification begin?
- In the fetal stage for most bones
- Some bones (wrist and ankle) ossify much later
- Many bones complete ossification by age 7
72
Where does endochondral ossification begin?
From within a model of hyaline cartilage
73
Hyaline cartilage model
Consists of chondrocytes, collagen, and ECM surrounded by connective tissue membrane (perichondrium) and immature cartilage cells (chondroblasts)
74
What do long bones have in the epiphysis?
Secondary ossification centers
75
Steps of endochondral ossification
- Differentiate into osteogenic cells, then osteoblasts, forming periosteum
- Bone begins to form where osteoblasts have built bone collar on external surface of bone
- Internal cartilage begins to calcify at the same time
- Osteoclasts etch oping for blood vessel and bone cell entry
- Osteoblasts replace calcified cartilage with early spongy bone
- Cavities enlarge and combine, developing the medullary cavity
- Secondary ossification centers develop in epiphysis
- Remaining ossified cartilage replaced by bone
- Osteoclasts enlarge medullary cavity, fills with bone marrow
- Epiphyses finish ossifying
76
Osteoporosis
Bone disease in which bones become weak and brittle due to inadequate inorganic matrix
77
What causes osteoporosis?
- Dietary: calcium and/or vitamin D deficiency
- Female gender
- Advanced age
- Lack of exercises
- Hormones (lack of estrogen in postmenopausal women)
- Genetic factors
78
Appositional Growth
- Bone growth in width
- Does not result in immediate formation of osteons
- Forms new circumferential lamellae
79
What happens to old circumferential lamellae?
They are removed or restructured into osteons
80
Bone remodeling
Continuous process of bone formation and loss after growth in length is finished
81
Reasons for bone remodeling cycle
- Maintenance of calcium ion homeostasis
- Replacement of primary bone with secondary bone
- Bone repair
- Replacement of old brittle bone with newer bone
- Adaptation to tension and stress
82
Bone remodeling in response to compression
Bone deposition
83
Bone remodeling in response to tension
Bone deposition
84
Bone remodeling in response to continuous pressure
Bone resorption
85
How do intestines affect concentration of calcium ions in body fluids?
When calcium concentration drops below normal rate of intestinal absorption increases
86
How do the kidneys affect concentration of calcium ions in body fluids?
When calcium concentration drops below normal osteoclasts are stimulated to increase release of stored calcium ions
87
How do bones affect concentration of calcium ions in body fluids?
When calcium concentration drops below normal kidneys retain calcium ions
88
What happens when calcium is low in the body?
- Parathyroid gland will secret PTH (parathyroid Hormone)
- Kidneys and the small intestine absorb calcium and phosphate
- PTH will stimulate the kidneys to release calcitriol which will also effect the kidneys and the small intestine to absorb calcium and phosphate
- PTH will go to the bones and directly increase activity of osteoclast to break down bone and release into the blood calcium and phosphate
89
What happens when calcium is high in the body?
- Thyroid gland will secret calcitonin
- Calcitonin effect the kidneys and the small intestine to not absorb calcium and phosphate
- Calcitonin will cause the kidneys and the small intestine to not absorb calcium and phosphate
- It will go to the bones and indirectly inhibit PTH from activating osteoclast and as a result osteoblast with deposit calcium and phosphate back into the bone
90
Types of bone fractures
- Open (compound)
- Closed (simple)
- Incomplete
- Complete
- Greenstick
- Hairline
- Comminuted
91
Open (compound) fracture
- Bone break with open wound
| - Bone may be sticking out of wound
92
Closed (simple) fracture
Non perforated skin
93
Incomplete fracture
Doesn't extend across the bone
94
Complete fracture
Extends across the bone
95
Greenstick fracture
Incomplete fracture that occurs on the convex side of the curve of a bone
96
Hairline fracture
- Incomplete where two sections of bone do not separate
| - Common in skull fractures
97
Comminuted fracture
Complete with break into more than 2 pieces
98
Bone Repair
- Hematoma (blood clot) fills in gap between bone fragments
- Fibroblasts and chondroblasts form soft callus
- Osteoblasts build hard (bone) callus
- Bone callus is remodeled and primary bone is replaced with secondary bond
