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BIOL 235 Midterm 1 > Chapter 6 > Flashcards

Chapter 6 Flashcards

1
Q

Bone

A

An organ made up of several different tissues working together: bone (osseous) tissue, cartilage, dense connective tissue, epithelium, adipose tissue, and nervous tissue.

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2
Q

Skeletal system

A

The entire framework of bones and their cartilages.

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3
Q

What are the six basic functions of the skeletal system?

A
  1. Support
  2. Protection
  3. Assistance in movement
  4. Mineral homeostasis
  5. Blood cell production
  6. Triglyceride storage
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4
Q

Support

A

The skeleton serves as the structural framework for the body by supporting soft tissues and providing attachment points for the tendons of most skeletal muscles.

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5
Q

Protection

A

The skeleton protects the most important internal organs from injury. Eg. Cranial bones protect the brain, and the rib cage protects the heart and lungs.

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6
Q

Assistance in movement

A

Most skeletal muscles attach to bones; when they contract, they pull on bones to produce movement.

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7
Q

Mineral homeostasis (storage and release)

A

Bone tissue makes up about 18% of the weight of the human body. It stores several minerals, especially calcium and phosphorus, which contribute to the strength of bone. Bone tissue stores about 99% of the body’s calcium. On demand, bone releases minerals into the blood to maintain critical mineral balances (homeostasis) and to distribute the minerals to other parts of the body.

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8
Q

Blood cell production

A

Within certain bones, a connective tissue called red bone marrow produces red blood cells, white blood cells, and platelets, a process called hematopoiesis.

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9
Q

Triglyceride storage

A

Yellow bone marrow consists mainly of adipose cells, which store triglycerides. The stored triglycerides are a potential chemical energy reserve.

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10
Q

Long bone

A

A bone that has greater length than width.

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11
Q

What seven parts does a typical long bone consist of?

A
  1. Diaphysis
  2. Epiphyses
  3. Metaphysis
  4. Articular cartilage
  5. Periosteum
  6. Medullary cavity
  7. Endosteum
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12
Q

Diaphysis

A

Is the bone’s shaft or body – the long, cylindrical, main portion of the bone.

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13
Q

Epiphyses

A

Are the proximal and distal ends of the bone.

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14
Q

Metaphyses

A

The regions between the diaphysis and the epiphyses. In a growing bone, each metaphysis contains an epiphyseal (growth) plate. When a bone ceases to grow in length, each metaphysis contains a epiphyseal line.

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15
Q

Epiphyseal (growth) plate

A

A layer of hyaline cartilage that allows the diaphysis of the bone to grow in length; each metaphysis contains them.

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16
Q

Epiphyseal line

A

The resulting bone structure when the bone ceases to grow in length at about ages 14-24; replaces the cartilage in the epiphyseal plate.

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17
Q

Articular cartilage

A

Is a thin layer of hyaline cartilage covering the part of the epiphysis where the bone forms an articulation (joint) with another bone. Articular cartilage reduces friction and absorbs shock at freely movable joints. Because articular cartilage lacks a perichondrium and lacks blood vessels, repair of damage is limited.

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18
Q

Periosteum

A

Is a tough connective tissue sheath and its associated blood supply that surrounds the bone surface wherever it is not covered by articular cartilage; the periosteum also protects the bone, assists in fracture repair, helps nourish bone tissue, and serves as an attachment point for ligaments and tendons.

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19
Q

The periosteum is composed of an ______ of dense irregular connective tissue and an ______ that consists of cells. Some of the cells enable bone to grow in ______, but not in ______.

A

Outer fibrous layer; inner osteogenic layer; thickness; length

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20
Q

Perforating fibers (Sharpey’s fibers)

A

Thick bundles of collagen that extend from the periosteum into the bone extracellular matrix, and attach the periosteum to underlying bone.

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21
Q

Medullary cavity

A

AKA marrow cavity; is a hollow, cylindrical space within the diaphysis that contains fatty yellow bone marrow and numerous blood vessels in adults; this cavity minimizes the weight of the bone by reducing the dense bony material where it is least needed. The long bones’ tubular design provides maximum strength with minimum weight.

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22
Q

Endosteum

A

Is a thin membrane that lines the medullary cavity.

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23
Q

Why is bone tissue classified as a connective tissue?

A

Like other connective tissue, bone, or osseous tissue, contains an abundant extracellular matrix that surrounds widely separated cells. The extracellular matrix is ~15% water, ~30% collagen fibers, and ~55% crystallized mineral salts.

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24
Q

Hydroxyapatite

A

Crystals formed when calcium phosphate combines with calcium hydroxide.

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25
Calcification
When mineral salts are deposited in the framework formed by the collagen fibers of the extracellular matrix, they crystallize, and the tissue hardens.
26
What are the four types of cells present in bone tissue?
1. Osteoprogenitor cells 2. Osteoblasts 3. Osteocytes 4. Osteoclasts
27
Osteoprogenitor cells
Osteoprogenitor cells are found along the inner portion of the periosteum, in the endosteum, and in the canals within bone that contain blood vessels; develop into an osteoblast; only cells that undergo cell division.
28
Osteoblasts
Form bone extracellular matrix.
29
Osteocytes
Maintain bone tissue.
30
Osteoclasts
Main function is bone resorption (the breakdown of bone extracellular matrix).
31
Compact bone tissue
Contains few spaces and is the strongest form of bone tissue; is found beneath the periosteum of all bones and makes up the bulk of the diaphysis of long bones; provides protection and support and resists the stresses produced by weight and movement.
32
Osteons
AKA haversian systems: repeating structural units that compact bone tissue is composed of. Osteons in compact bone tissue are aligned in the same direction and are parallel to the length of the diaphysis (as a result, the shaft of a long bone resists bending or fracturing even when considerable force is applied from either end).
33
Osteonic canal
AKA haversian or central canal; surrounded by concentric lamellae; holds nerves and blood vessels.
34
Concentric lamellae
Resemble growth rings on a tree; circular plates of mineralized extracellular matrix of increasing diameter, surrounding the osteonic canal. These tubelike units of bone generally form a series of parallel cylinders that, in long bones, tend to run parallel to the long axis of the bone.
35
Lacunae
Small spaces between the concentric lamellae; contain osteocytes
36
Canaliculi
Small canals that extend from the lacunae, that connect to other lacunae in the osteonic canal. Allow for intracellular communication and a passageway for the delivery of nutrients to the osteocytes.
37
Interstitial lamellae
Areas between neighboring osteons; have lacunae with osteocytes and canaliculi; are small fragments of older osteons that have been partially destroyed during bone rebuilding or growth.
38
Interosteonic canals
AKA Volkmann’s or perforating canals; blood vessels and nerves from the periosteum that penetrate the compact bone tissues; the vessels and nerves of the interosteonic canals connect with those of medullary cavity, periosteum, and osteonic canals.
39
Circumferential lamellae
Lamellae that are arranged around the entire outer and inner circumference of the shaft of long bone; they develop during initial bone formation.
40
The circumferential lamellae directly deep to the periosteum are called ______. They are connected to the periosteum by ______. The circumferential lamellae that line the medullary cavity are called ______.
External circumferential lamellae; perforating fibers AKA Sharpey’s fibers; internal circumferential lamellae.
41
Spongy bone tissue
AKA trabecular or cancellous bone tissue; in contrast to compact bone tissue, does not contain osteons; spongy bone tissue is always located in the interior of a bone, always protected by a covering of compact bone tissue; spongy bone tissue makes up most of the interior bone tissue of short, flat, sesamoid, and irregularly shaped bones. In long bones it forms the core of the epiphyses beneath the paper-thin layer of compact bone and forms a variable narrow rim bordering the medullary cavity of the diaphysis.
42
In what two ways does spongy bone tissue differ from compact bone tissue?
1. Spongy bone tissue is light, which reduces the overall weight of the bone. This allows for the bone to move more readily when pulled by a skeletal muscle. 2. The trabeculae of spongy bone tissue support and protect the red bone marrow. Spongy bone in the hip bones, ribs, sternum (breastbone), vertebrae, and the proximal ends of the humerus and femur is the only site where red bone marrow is stored and, thus, the site where hemopoiesis (blood cell production) occurs in adults.
43
Trabeculae
Are lamellae that are arranged in an irregular pattern of thin columns; between the trabeculae are spaces that are filled with red bone marrow in bones that produce blood cells, and yellow bone marrow (adipose tissue) in other bones. Both types of bone marrow contain numerous small blood vessels that provide nourishment to the osteocytes; each trabecula consists of concentric lamellae, osteocytes that lie in lacunae, and canaliculi that radiate outward from the lacunae.
44
Blood vessels
Abundant portions of bone containing red bone marrow; pass into bones from periosteum.
45
Periosteal arteries
Small arteries accompanied by nerves, enter the diaphysis through many interosteonic canals (Volkmann’s or perforating canals) and supply the periosteum and outer part of the compact bone.
46
Nutrient arteries
Located near the center of the diaphysis; passes through a hole in compact bone called the nutrient foreman – once it enters the medullary cavity, the nutrient artery divides into proximal and distal branches that course toward each end of the bone. These branches supply both the inner part of compact bone tissue of the diaphysis and the spongy bone tissue and red bone marrow as far as the epiphyseal plates (or lines).
47
Metaphyseal arteries
Enter the metaphyses of a long bone and, together with the nutrient artery, supply the red bone marrow and bone tissue of the metaphyses.
48
Epiphyseal arteries
Enter the epiphyses of a long bone and supply the red bone marrow and bone tissue of the epiphyses.
49
Nutrient veins
Carry blood away from long bones; accompany the nutrient artery and exit through the diaphysis
50
Epiphyseal veins
Carry blood away from long bones; accompany the epiphyseal arteries and exit through the epiphyses and metaphysis.
51
Metaphyseal veins
Carry blood away from long bones; accompany the metaphyseal arteries and exit through the epiphyses and metaphysis.
52
Periosteal veins
Carry blood away from long bones; accompany the periosteal arteries and exit through the periosteum.
53
Ossification
The process by which bone forms.
54
What are the four principle situations of ossification?
1. The initial formation of bones in an embryo and fetus 2. The growth of bones during infancy, childhood, and adolescence until their adult sizes are reached 3. The remodeling of bone (replacement of old bone by new bone tissue throughout life) 4. The repair of fractures (breaks in bones) throughout life
55
What are the two patterns of bone growth in an embryo and fetus?
1. Intramembranous ossification 2. Endochondral ossification
56
Intramembranous ossification
Type of ossification where bone forms directly within mesenchyme, which is arranged in sheetlike layers that resemble membranes; is the simpler of the two methods; the flat bones of the skull, most of the facial bones, mandible (lower jawbone), and the medial part of the clavicle (collar bone) are formed in this way. Also, the “soft spots” that help the fetal skull pass through the birth canal later harden as they undergo intramembranous ossification.
57
Describe the steps of intramembranous ossification?
1. Development of the ossification center 2. Calcification 3. Formation of trabeculae 4. Development of the periosteum
58
Endochondral ossification
Type of ossification where bone forms within hyaline cartilage that develops from mesenchyme; the replacement of cartilage by bone is called endochondral ossification. Although most bones of the body are formed in this way, the process is best observed in a long bone.
59
Describe the steps of endochondral ossification?
1. Development of the cartilage model 2. Growth of the cartilage model 3. Development of the primary ossification center 4. Development of the medullary (marrow) cavity 5. Development of the secondary ossification centers 6. Formation of the articular cartilage and the epiphyseal plate (growth plate)
60
Cartilage model
Produced by cartilage extracellular matrix, that are secreted by chondroblasts.
61
Perichondrium
A covering that develops around the cartilage model.
62
Interstitial growth
AKA endogenous growth; growth from within.
63
Appositional growth
AKA exogenous growth; growth at the outer surface.
64
Periosteum
Term used once the perichondrium starts to form bone.
65
Primary ossification center
Region where bone tissue will replace most of the cartilage.
66
Secondary ossification centers
Develop after the branches of the epiphyseal artery enter the epiphyses, usually around the time of birth.
67
During infancy, childhood, and adolescence, what are the two patterns of growth for bones?
1. Growth in length 2. Growth in thickness
68
What two major events are involved in the growth in length of long bones?
1. interstitial growth of cartilage on the epiphyseal side of the epiphyseal plate. 2. Replacement of cartilage on the diaphyseal side of the epiphyseal plate with bone by endochondral ossification.
69
What four zones does the epiphyseal plate consist of?
1. Zone of resting cartilage 2. Zone of proliferating cartilage 3. Zone of hypertrophic cartilage 4. Zone of calcified cartilage
70
Zone of resting cartilage
This layer is nearest the epiphysis and consists of small, scattered chondrocytes. The term “resting” is used because the cells do not function in bone growth. Rather, they anchor the epiphyseal plate to the epiphysis of the bone.
71
Zone of proliferating cartilage
Slightly larger chondrocytes in this zone are arranged like stacks of coins. These chondrocytes undergo interstitial growth as they divide and secrete extracellular matrix. The chondrocytes in this zone divide to replace those that die at the diaphyseal side of the epiphyseal plate.
72
Zone of hypertrophic cartilage
This layer consists of large, maturing chondrocytes arranged in columns.
73
Zone of calcified cartilage
The final zone of the epiphyseal plate is only a few cells thick and consists mostly of chondrocytes that are dead because the extracellular matrix around them has calcified. Osteoclasts dissolve the calcified cartilage, and osteoblasts and capillaries from the diaphysis invade the area. The osteoblasts lay down bone extracellular matrix, replacing the calcified cartilage by the process of endochondral ossification. Recall that endochondral ossification is the replacement of cartilage with bone. As a result, the zone of calcified cartilage becomes the “new diaphysis” that is firmly cemented to the rest of the diaphysis of the bone.
74
Describe the steps in how bone can grow in thickness
1. At the bone surface, periosteal cells differentiate into osteoblasts. The osteoblasts become surrounded by extracellular matrix and develop into osteocytes. This process forms bone ridges on either side of a periosteal blood vessel. 2. Eventually, the ridges fold together and fuse, and the groove becomes a tunnel that encloses the blood vessel. The former periosteum now becomes the endosteum that lines the tunnel. 3. Osteoblasts in the endosteum deposit bone extracellular matrix, forming new concentric lamellae. A new osteon is created. 4. As an osteon is forming, osteoblasts under the periosteum deposit new circumferential lamellae, further increasing the thickness of the bone.
75
Bone remodelling
Is the ongoing replacement of old bone tissue by new bone tissue.
76
Bone resorption
The removal of minerals and collagen fibers from bone by osteoclasts, results in the destruction of bone extracellular matrix.
77
Bone deposition
The addition of minerals and collagen fibers to bone by osteoblasts; results in the formation of bone extracellular matrix.
78
What three factors affect bone growth and remodeling?
1. Minerals 2. Vitamins 3. Hormones
79
What does calcium phosphorus do (in bone)?
Make bone extracellular matrix hard.
80
What does fluoride do (in bone)?
Fluoride helps strengthen bone extracellular matrix.
81
What does manganese do (in bone)?
Activates enzymes involved in synthesis of bone extracellular matrix.
82
What does magnesium do (in bone)?
Helps form bone extracellular matrix.
83
What does vitamin A do (in bone)?
Needed for the activity of osteoblasts during remodeling of bone; deficiency stunts bone growth; toxic in high doses.
84
What does vitamin C do (in bone)?
Needed for synthesis of collagen, the main bone protein; deficiency leads to decreased collagen production, which slows down bone growth and delays repair of broken bones.
85
What does vitamin D do (in bone)?
Active form (calcitriol) is produced by the kidneys; helps build bone by increasing absorption of calcium from gastrointestinal tract into blood; deficiency causes faulty calcification and slows down bone growth; may reduce the risk of osteoporosis but is toxic if taken in high doses. People who have minimal exposure to ultraviolet rays or do not take vitamin D supplements may not have sufficient vitamin D to absorb calcium. This interferes with calcium metabolism.
86
What do vitamins K and B do (in bone)?
Needed for synthesis of bone proteins; deficiency leads to abnormal protein production in bone extracellular matrix and decreased bone density.
87
What does growth hormone (GH) do (in bone)?
Secreted by the anterior lobe of the pituitary gland; promotes general growth of all body tissues, including bone, mainly by stimulating production of insulin-like growth factors (IGFs).
88
What do insulin-like growth factors (IGFs) do (in bone)?
Secreted by the liver, bones, and other tissues on stimulation by growth hormone; promotes normal bone growth by stimulating osteoblasts and by increasing the synthesis of proteins needed to build new bone.
89
What do thyroid hormones do (in bone)?
Secreted by thyroid gland; promote normal bone growth by stimulating osteoblasts.
90
What does insulin do (in bone)?
Secreted by the pancreas; promotes normal bone growth by increasing the synthesis of bone proteins.
91
What do sex hormones do (in bone)?
Secreted by the ovaries in women (estrogens) and by the testes in men (testosterone); stimulate osteoblasts and promote the sudden “growth spurt” that occurs during the teenage years; shut down growth at the epiphyseal plates around age 18–21, causing lengthwise growth of bone to end; contribute to bone remodeling during adulthood by slowing bone resorption by osteoclasts and promoting bone deposition by osteoblasts.
92
Parathyroid hormone (PTH)
Secreted by the parathyroid glands; promotes bone resorption by osteoclasts; enhances recovery of calcium ions from urine; promotes formation of the active form of vitamin D (calcitriol).
93
Calcitonin (CT)
Secreted by the thyroid gland; inhibits bone resorption by osteoclasts.
94
Describe the importance of calcium in the body?
Bone is the body’s major calcium reservoir, storing 99% of total body calcium.
95
Describe the importance of regulation of calcium in the body
Both nerve and muscle cells depend on a stable level of calcium ions (Ca2+) in extracellular fluid to function properly. Blood clotting also requires Ca2+. Also, many enzymes require Ca2+ as a cofactor (an additional substance needed for an enzymatic reaction to occur).
96
Explain how blood calcium is regulated
By the parathyroid hormone (PTH)! PTH is secreted by the parathyroid glands; this hormone increases blood Ca2+ level; PTH secretion operates via a negative feedback system.
97
Calcitriol
The active form of vitamin D.

BIOL 235 Midterm 1 (10 decks)

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