Chapter 7: Bone Tissue Flashcards
1
Q
What is the study of bone called?
A
Osteology
2
Q
What are your most durable remains in bone?
A
Bones and teeth
3
Q
What are the functions of the skeleton?
A
- Skeleton is living (it responds to stress in the body)
- Support
- Protection
- Movement
- Electrolyte balance (calcium and phopshate)
- calcium is usually the concern here
- Acid-base balance
- (buffers blood against pH changes by alternating carbonate and phosphate salt levels)
- Blood formation (hemopoiesis)
- makes RBC, WBC, and platelets
4
Q
What is the definition of bone?
A
Bone (osseous tissue): connective tissue with the matrix hardened by calcium phopshate and other minerals
5
Q
Define mineralization or calcification.
A
The hardening process of bone.
6
Q
What do individual bones consist of?
A
Individual bones are organs and they consist of bone tissue, bone marrow, cartilage, adipose tissue, nervous tissue, and fibrous connective tissue.
7
Q
What are the types of bones and some examples?
A
- Flat bones (sternum, skull bones)
- Long bones: bones that are longer than wide (mostly arms and legs)
- Short bones: length and width are approximately equal (carpals and tarsals)
- Sesamoid bones: bones you develop in a tedon or ligament due to high stress; unnamed (one in carpal, one in foot) (exceptions: patella)
- sutural bones: usually unnamed (e.g. back of head, lamboid formed by small cracks coming together)
- Irregular bones: everything else (e.g. vertebrae)
8
Q
What is the structure of a bone?
A
Epiphysis: the end of the bone, has proximal end and distal end
Diaphysis: shaft of bone
Epiphyseal Line (aka metaphysis): separates epiphysis from diaphysis
- this called the “growth plate” until growth is dome
Articular cartilage: white, hyaline cartilage at the ends of moveable joints
Spongy bone on the outer layer, compact bone on the inner layer, marrow cavity
9
Q
What are the general features of bone?
A
- articular cartilage (hyaline)
- nutrient foramina (holes where blood vessels come in)
- Periosteum
-
endosteum (thin layer of reticular connective tissue lining marrow cavity)
- contains osteoblasts and osteoclasts
-
epiphyseal plate (enables growth in length of bone)
- made of hyaline cartilage
- when finished, turns into epiphyseal line
10
Q
What are the general features of flat bones?
A
- Sandwich-like
- two layers of compact bone with a middle layer of spongy bone
- diploe: spongy middle layer
- absorbs shock
- marrow spaces lined with endosteum
- red, make blood here
11
Q
What are the two layers of periosteum and their general features?
A
- Outer fibrous layer made of collagen
- some fibers continuous with tendons
- perforating fibers: penetrate into bone matrix
- Inner osteogenic layer
- important to bone growth and healing of fractures
12
Q
Describe “trabeculae”
A
Trabaculae (thin plates) is calcified and hard, but it is named for its spongelike appearance. It is covered with endosteum and permeated by spaces filled with bone marrow (where blood is made).
13
Q
What are the 4 types of bone cells and their general features?
A
- Osteogenic cells
- stem cells that perform mitosis and become osteoblasts
- Osteoblasts: bone forming cells
- Osteocytes: mature bone cells
- found in pockets called lacunae
- connected to each other by gap junctions and canaliculi (cracks in bone to connect cells)
- some reabsorb bone matrix and others deposit it (regulates bone modeling)
- Osteoclasts
- the “oddball”; it is not osteogenic
- derived from fusion of WBC
- usually multinucleate
- secretes enzymes and acids for resorption (the break down of bone)
14
Q
What are the main 2 steps involved in the making of bone? How does resorption work?
A
- Secrete protein (collagen fibers)
- need lots of ATP and amino acids
- cell needs lots of Rough ER and Golgi
- Deposit calcium salts (from blood)
- process is like making rock candy
- Enzymes dissolve collagen via hydrolysis and acids dissolve salt, which returns to the blood
15
Q
What are the two portions of bone matrix and their general features?
A
- Organic portion (1/3 of bone)
- Collagen, carbohydrate-protein complexes
- synthesized by osteoblasts
- responsible for the flexibility of bone
- Inorganic portion (2/3 of bone)
- 85% hydroxyapatite (calcium phosphate)
- 10% calcium carbonate
- 5% other minerals (floride, sodium, etc.)
- Responsible for the hardness of bone
16
Q
What happens to bone under the following conditions: mineral deficiency and defect in collagen deposition?
A
Mineral deficiency: soft bones (in adults causes pain, in children causes deformity as seen in Rickets)
Collagen: no flexibility (brittle bone disease), bones snap easily
17
Q
What are the components of a Haversian System or an Osteon?
A
- Lamella
- columns of the matrix (mainly collagen) that are weight bearing
- concentric, circumferential, and interstitial lamella
- Central (Haversian) canal)
- contains blood vessels and nerves
- Perforating (Volkmann’s) canals
- channels that connect blood and nerves from periosteum to the central (Haversian) canal
18
Q
What is the structure of spongy bone?
A
- Lattice of bone covered with endosteum
- trabeculae (thin plates of bone)–develop along the bone’s line of stress
- spicules (slivers of bone)
- spaces filled with red bone marrow
- few osteons, no central canals
- provides strength with minimal weight
- will crush first if depleted calcium (like in osteoperosis)
19
Q
What is the definition of bone marrow, its two types, and their general structures?
A
Bone marrow: soft tissue in marrow cavities of long bones and small spaces of spongy bone.
- Red marrow (myeloid tissue): contains hemopoetic tissue (makes blood cells)
- Yellow marrow
- only in adults
- stores triglycerides
- can transform into red marrow in the event of anemia
20
Q
Where is red marrow (hematopoietic tissue) located in children and in adults?
A
Children: medullary cavity and all areas of spongy bone (much will be converted to yellow marrow over time)
Adults: head of the femur and the humerus, diploe (spongy bone) of flat bones, some irregular bones (e.g. hip and vertebrae)
21
Q
What is ossification / osteogenesis and its two types?
A
Ossification is the formation of bone.
- Intramembranous ossification: bone develops within fibrous connective tissue membrane
- Endochondrial ossification: start with mesenchyme, then cartilage, and then bone (bone forms by replacing Hyaline cartilage)
22
Q
How does intramembranous ossification work and what are soem examples of it?
A
- mesenchymal cells turn to osteoblasts turn to osteocytes, which form spongy bone
- This forms the flat bones of the skull, clavicles, and ossifies the fontanels
- Most of these bones are remodeled (destroyed and reformed) as we grow to adult size
23
Q
How does endochondrial ossification work and what are some examples of it?
A
- Bone forms by replacing hyaline cartilage
- Forms most of the body below the skull (except the clavicle)
- Mesenchyme turns to chondroblasts, which die and are replaced by osteoblasts turn to spongy bone and finally turn to compact bone
24
Q
What are the two types of endochondrial ossification and how do they work?
A
- Primary ossification: works on the diaphysis (shaft) of bone
- this is the first part to be destroyed and turned into bone
- Secondary ossification: works on epiphysis (ends of bones)
- this turns cartilage into bone from the center outward
- cartilage cells undergo mitosis and push the epiphysis away from the diaphysis
- cartilage cells die and are replaced by bone
- When plate is finished, no more cartilage plate: now epiphyseal line
- bone can no longer grow in length; plate is closed
- articular cartilage should stay for life
25
What are the two types of dwarfism and how do they work?
* Achondroplastic Dwarfism
* long bones stop growing in childhood
* Individual has normal torso, but abnormally short arms and legs
* growth plates close early (cartilage is not multiplying)
* spotaneous mutation produces dominant allele
* Pituitary Dwarfism
* rare, usually only seen in very poor countries
* lack of growth hormone (can be fixed by taking the hormone)
* normal proportions with short stature.
* lack of hormone messes with CNS
26
\*\*\*\*How does appositional growth (bones widening and thickening) work in the bones?
* Appositional growth occurs at the bones's surface
* Continual growth in diameter and thickness
* Intramembranous ossification
* Osteoblasts of periosteum deposit osteoid tissue
* lay down matrix: circumferential lamella
* Become trapped as tissue calcifies
* Osteoclasts of endosteum enlarge marrow cavity
27
What is the general process of bone remodeling in adults?
* 10% of skeleton is remodeled per year
* Remodeled by osteoblasts (bone deposition) and osteoclasts (resportion)
* Wolff's law
* bone grows or remodels based on the demands placed on it
* Exercise promotes bone growth, lack of exercise atrophies bone (and therefore muscle)
28
Desribe the mineral deposition and mineral resorption processes that occur in bone.
* Mineral deposition
* osteoblasts produce collagen fibers
* fibers become encrusted with minerals
* first few crystal act as seed crystals that attract more calcium and phosphate
* Abnormal calcification is called a calculus
* can form in lung, brain, eye, muscle, tendon, artery
* Mineral Resorption
* Osteoclasts pump hydrogen to ECF (chloride follows)
* Hydrochloric acid (pH 4) dissolves minerals
* enzyme (acid phosphatase) digests collagen
* Released minerals enter blood
29
What are the two conditions presented in lack of calcium homeostasis and why are they problems?
* Hypocalcemia: low blood calcium
* causes overly excitable nervous system and muscle spasms
* caused by Vitamin D deficiency, diarrhea, thyroid tumors, underactive parathyroid glands
* Pregnancy and lactation increase risk
* Test: Chvostek's sign (poke facial nerve, facial nerves will pull unnaturally.
* Hypercalcemia: high blood calcium
* very rare
* nerve and muscles less excitable
* Muscle weakness, sluggish reflexes, paralysis
* Test: Trousseau's sign (bleed pressure test, fingers curl in)
30
Why is calcium homeostasis important?
* Calcium needed in neuron communication, muscle contraction, blood clotting, and exocytosis
* MInerals are deposited into skeleton and withdrawn when they are needed for other purposes
* Bone is the bank
* Body will sacrifice bone to save pH of blood, which is more critical
31
What factors and hormones can regulate Calcium homeostasis?
* loss: uriary and fecal losses
* intake: diet
* balance maintained by exchange with osseous tissue
* 3 hormones:
* calcitrol (Vitamin D absorption, digestive system), calcitonin, parathyroid hormone (both are skeletal system).
32
What calcitrol? How is it made and what does it do?
* Calcitrol is a hormone that regulates calcium homeostasis.
* It is the most active form of Vitamin D (Vitamin D3) and it is produced by actions of the skin, liver, and kidneys.
* It is a hormonse that raises blood calcium level.
* Increases absorption by small intensine, reabsorption by skeleton, less lost in urine
* It is necessary for bone deposition
* lack of calcitrol results in Rickets for children and ostemalacia for adults
33
What is Calcitonin? What does it do?
* It is a calcium homeostasis hormone
* It is produced by the thyroid gland
* Its release is trigged by high blood calcium
* It will lower blood calcium
* inhibits osteoclasts (resorption)
* stimulates osteoblasts (grow bone)
* Important in children, weak effect in adults except pregnant/lactating woman
34
What is parathyroid hormone and what does it do?
* It is a calcium homeostasis hormone
* It is released by the parathyroid glands
* It is trigged by low blood calcium
* It increases blood calcium
* increase number of osteoclasts
* promote calcium reabsorption of kidneys (doesn't excrete in urine)
* promotes final step of calcitrol synthesis
* inhibits collagen synthesis by osteoblasts
35
What is the process of bone development from childhood to early adulthood?
* Infancy and childhood
* Epiphyseal plate activity is stimulated by Human Growth Hormone (HGH)
* Adolescence: testosterone and estrogens
* promote adolescent growth spurts
* differentiates the male/female skeleton
* induces epiphyseal plate closure
* Early Adulthood: bone growth ends 18-21 years
* some outliers exist
* Adulthood
* prevent osteoperosis
* build bones up ages 25-40
36
What factors affect bone growth?
* Estrogen
* Estrogen has a stronger affect on bone growth than testosterone
* Girls grow faster than boys and reach full height earlier
* Males grow for a longer time and taller
* Anabolic steroids cause growth to stop
* epiphyseal plates close prematurely
* results in abnormally short adult stature
37
What are bone fractures and their classifications?
* Stress fracture: break caused by abnormal trauma to a bone
* Pathological fracture: break in a bone weakened by disease (cancer or osteoperosis)
* Classified by structural characteristics
* displaced v. nondisplaced
* pulled out of normal alignment / not
* open v. closed / simple v. compound
* Open = open to skin, closed = closed to skin
38
How do fractures heal?
* The fracture in bone creates a hematoma and the bone bleeds a lot
* The bone deposits collagen and forms both a soft callus and fibrocartilage
* The bone forms a hard callus and spongy bone
* The bone remodels into compact bone and is healed
39
What are the treatment types for bone fractures?
* Closed reduction: surgery
* Open reduction: no surgery
* Casts
40
What is osteoperosis and what problems does it cause?
* Osteoperosis is the most common bone disease
* It affects spongy bone the most
* (spongy bone is most metabolically active)
* Trabiculae get crushed and the bone heals that way
* Inhibits resorption of estrogen by osteoclasts
* estrogen highly important for bone density
* Individuals are subject to fractures of hip, wrist, and vertebral column
* Most affected
* post menopausal women and underweight, young female athletes
* Example:
* Widow's hump (deformity of spine due to vertebral bone loss)
41
What are the most durable remains of a dead body?
Bones and teeth
42
What is the skeletal system made of?
Bones, cartilages and ligaments
43
What is a cartilage?
* Forerunner of most bones
* Covers many joint surfaces of mature bones
44
What is a ligament?
Holds bones together at joints
45
What are tendons?
Attach muscles to bones
46
What are the functions of the skeleton?
* Support
* Protection
* Movement
* Electrolyte balance
* Acid-base balance
* Blood formation
47
What is skeletal support?
48
What is skeletal protection?
Protection of the brain, spinal cord, heart, lungs, and more
49
What is skeletal movement?
limb movements, breathing, and other movements depend on bone
50
What is skeletal electrolyte balance?
calcium and phosphate levels
51
What is skeletal acid-base balance
buffers blood against large pH changes by altering phosphate and carbonate salt levels
52
What is skeletal blood formation?
red bone marrow is the chief producer of blood cells
53
What's the definition of bone (osseous tissue)?
connective tissue with the matrix hardened by calcium phosphate and other minerals
54
What is mineralization (calcification)?
the hardening process of bone
55
What do all individual bones consist of?
Bone tissue, bone marrow, cartilage, adipose tissue, nervous tissue, and fibrous connective tissue
56
What are flat bones?
* Thin, curved plates
* Protect soft organs
57
What are long bones?
* Longer than wide
* Rigid levers acted upon by muscles; crucial for movement
58
What are short bones?
Approximately equal in length and width
Glide across one another in multiple directions
59
What are irregular bones?
Elaborate shapes that do not fit into other categories
60
What is a compact bone?
Dense outer shell of bone
61
What is a spongy(cancellous) bone?
loosely organized bone tissue
Found in center of ends and center of shafts of long bones and in middle of nearly all others
Covered by more durable compact bone
62
What's the compact/spongy weight of the skeleton?
Three-fourths compact and one-fourth spongy bone by weight
63
What is the meaning of diaphysis(long bone)?
Shaft that provides leverage
64
What is the medullary(marrow cavity) cavity?
space in the diaphysis of a long bone that contains bone marrow
65
What is the epiphysis?
* enlarged ends of a long bone
* Strengthen joint and anchor ligaments and tendons
66
What is articular cartilage?
layer of hyaline cartilage that covers joint surface; allows joint to move more freely
67
What is nutrient foramina?
minute holes in bone surface that allows blood vessels to penetrate
68
What is the periosteum?
* External sheath covering most of bone
* Outer fibrous layer of collagen
* Some fibers continuous with tendons
69
What are perforating fibers?
* Penetrate into bone matrix
* Inner osteogenic layer of bone-forming cells
* Important to bone growth and healing of fractures
70
What's the meaning of endosteum?
* Thin layer of reticular connective tissue lining marrow cavity
* Has cells that dissolve osseous tissue and others that deposit it
71
What is the epiphyseal(growth plate) plate?
* Area of hyaline cartilage that separates epiphyses and diaphyses of children’s bones
* Enables growth in length
72
What is the epiphyseal line?
in adults, a bony scar that marks where growth plate used to be
73
What's a flat bone?
* Sandwich-like construction
* Two layers of compact bone enclosing a middle layer of spongy bone
* Both surfaces covered with periosteum
74
What is a diploe(spongy bone)?
* Spongy middle layer
* Absorbs shock
* Marrow spaces lined with endosteum
75
Bone is connective tissue that consists of?
cells, fibers, and ground substance
76
What are the four principal types of bone cells?
Osteogenic cells; osteoblasts; osteocytes; osteoclasts
77
What are osteogenic cells?
stem cells found in endosteum and inner layer of periosteum
78
What are osteoblasts?
* Bone-forming cells
* Form single layer of cells under endosteum and periosteum
* Nonmitotic
* Synthesize soft organic matter of matrix which then hardens by mineral deposition
* Stress stimulates osteogenic cells to multiply rapidly and increase the number of osteoblasts which reinforce bon
79
What are osteocytes?
former osteoblasts that have become trapped in the matrix they deposited
80
What are lacunae?
tiny cavities where osteocytes reside
81
What are canaliculi?
little channels that connect lacunae
82
What do cytoplasmic processes of osteocytes do?
Reach into canaliculi and contact processes of neighboring cells
83
What do gap junctions do?
allow for passage of nutrients, wastes, signals
84
What are osteoclasts?
bone-dissolving cells found on bone surface
85
How do osteoclasts develop?
* From same bone marrow stem cells that give rise to blood cells (different origin from other bone cells)
* Very large cells formed from fusion of several stem cells
86
What are some features of osteoclasts?
* Have multiple nuclei in each cell
* Ruffled border (large surface area) faces bone
* Cells often reside in resorption bays (pits in bone surface)
* Dissolving bone is part of bone remodeling
87
How heavy is the matrix of osseous tissue?
by dry weight, about one-third organic and two-thirds inorganic matter
88
What is organic matter in bones?
* Synthesized by osteoblasts
* Collagen, carbohydrate–protein complexes, such as glycosaminoglycans, proteoglycans, and glycoproteins
89
What is in organic matter in bones?
* 85% hydroxyapatite (crystallized calcium phosphate salt)
* 10% calcium carbonate
* Other minerals (fluoride, sodium, potassium, magnesium)
90
Bone is a composite material and?
a combination of a ceramic and a polymer
* Hydroxyapatite and other minerals are the ceramic and collagen (protein) is the polymer
* Ceramic portion allows the bone to support body weight without sagging
91
What disease causes mineral deficiency and results in soft, deformed bones?
Rickets
92
What does polymer (protein) gives our bones?
* Flexibility
* Osteogenesis imperfecta (brittle bone disease) results from a defect in collagen deposition
93
What surrounds a central (haversian) canal running longitudinally?
Concentric lamellae
94
What are perforating canals?
transverse or diagonal passages
95
What fills the outer region of dense bones?
Circumferential lamellae
96
What fills irregular regions between osteons?
Interstitial lamellae
97
What does spongy bones consist of?
* Lattice of bone covered with endosteum
* Slivers of bone called spicules
* Thin plates of bone called trabeculae
* Spaces filled with red bone marrow
* Few osteons and no central canals
* All osteocytes close to bone marrow
* Provides strength with minimal weight
* Trabeculae develop along bone’s lines of stress
98
What is bone marrow?
soft tissue occupying marrow cavities of long bones and small spaces of spongy bone
99
What is red marrow(myeloid tissue)?
* Contains hemopoietic tissue—produces blood cells
* In nearly every bone in a child
* In adults, found in skull, vertebrae, ribs, sternum, part of pelvic girdle, and proximal heads of humerus and femur
100
What is yellow marrow (found in adults)?
* Fatty marrow that does not produce blood
* Can transform back to red marrow in the event of chronic anemia
101
What is the meaning of ossification or osteogenesis?
The formation of bones
102
What are the two methods in which human fetus and infant bones are developed?
* Intramembranous ossification
* Produces flat bones of skull and clavicle in fetus
* Thickens long bones throughout life
* Endochondral ossification
103
What's the meaning of achondroplastic dwarfism?
* Long bones stop growing in childhood
* Normal torso, short limbs
* Failure of cartilage growth in metaphysis
* Spontaneous mutation produces mutant dominant allele
104
What is pituitary dwarfism?
* Lack of growth hormone
* Normal proportions with short stature
105
Why does a mature bone remain a metabolically active organ?
* Involved in its own maintenance of growth and remodeling
* Exerts a profound influence over the rest of the body by exchanging minerals with tissue fluid
* Disturbance of calcium homeostasis in skeleton disrupts function of other organ systems
106
What is mineral deposition (mineralization)?
process in which calcium, phosphate, and other ions are taken from blood and deposited in bone
107
What do osteoblasts produce?
collagen fibers that spiral the length of the osteon
108
What do fibers become encrusted with?
* Minerals
* Hydroxyapatite crystals form at solubility product—critical level of calcium times phosphate concentration
* First few crystals act as seed crystals that attract more calcium and phosphate from solution
109
What is abnormal calcification (ectopic ossification)?
formation of a calculus (calcified mass) in an otherwise soft organ such as a lung, brain, eye, muscle, tendon, or artery (arteriosclerosis)
110
What is closed reduction (in treatment of fractions)?
procedure in which bone fragments are manipulated into their normal positions without surgery
111
What is open reduction(in treatment of fractions)?
involves surgical exposure of the bone and the use of plates, screws, or pins to realign the fragments
112
What is a cast(in treatment of fractures)?
normally used to stabilize and immobilize healing bone
113
How are femur fractures in children treated?
* With traction
* Aligns bone fragments by overriding force of the strong thigh muscles
114
How are hip fractures in older adults treated?
* Usually pinned and early walking is encouraged
* Fractures taking more than 2 months to heal may be treated with electrical stimulation which suppresses effects of parathyroid hormone
115
What is osteoporosis?
* The most common bone disease
* Severe loss of bone density
116
Why do bones lose mass and become brittle?
Loss of organic matrix and minerals
* Affects spongy bone the most since it is the most metabolically active
* Subject to pathological fractures of hip, wrist, and vertebral column
* Kyphosis (widow’s hump)—deformity of spine due to vertebral bone loss
* Complications of loss of mobility are pneumonia and thrombosis
117
What hormone maintains bone density in both sexes(also inhibits resorption by osteoclasts)?
Estrogen
118
Postmenopausal white women at greatest risk of?
Osteoporosis
* Ovaries cease to secrete estrogen
* White women begin to lose bone mass as early as age 35
* By age 70, average loss is 30% of bone mass
* Risk factors: race, age, gender, smoking, diabetes mellitus, diets poor which are poor in: calcium, protein, vitamins C and D
119
Why are young female athletes at risk of osteoporosis?
low body fat causing them to stop ovulating and decrease estrogen secretion
120
What is estrogen replacement therapy?
slows bone resorption, but increases risk of breast cancer, stroke, and heart disease
121
What are drug treatments for osteoporosis?
* Drugs- Fosamax, Actonel destroy osteoclasts
* PTH slows bone loss if given as daily injection
* Forteo (PTH derivative) increases density by 10% in 1 year
* May promote bone cancer so use is limited to 2 years
122
What is the best way to prevent osteoporosis?
Exercise and a good bone-building diet between ages 25 and 40
