Bones, Ch 6

Question 1

4 classes of bones?

Answer 1

Irregular, long, short, flat, sesamoid

Question 2

This type of bone appears white, smooth, and solid. It comprises 80% of bone mass.

Answer 2

Compact bone

Question 3

Also called cancellous or trabecular bone. Located internal to compact bone and appears porous. 20% of bone mass.

Answer 3

Spongy bone

Question 4

Bones that are greater in length than width. Most common bone shape, found in the upper and lower limbs. Vary in size. Has medullary cavity.

Answer 4

Long bones

Question 5

Bones with a length that is nearly equal to the width. Carpal bones, sesamoids, bones along the tendons of muscles.

Answer 5

Short bones

Question 6

Bones with flat, thin surfaces, that may be slightly curved. Provide surfaces for muscle attachment and protect underlying soft tissues. Roof of skull, scapulae, sternum, ribs.

Answer 6

Flat bones

Spongy bone in these is called the diploë

Question 7

Bones that have elaborate shapes. Vertebra, ossa coxae (hips), ethmoid, sphenoid, etc.

Answer 7

Irregular bones

Question 8

Elongated, usually cylindrical shaft of bone. Provides leverage and major weight support.

Answer 8

Diaphysis

Question 9

Hollow, cylindrical space within the diaphysis. Contain red bone marrow in children, yellow marrow (fat) in adults

Answer 9

Medullary cavity

Question 10

Knobby region at the ends of a long bone. Joint surface covered by thin layer of hyaline cartilage (articular cartilage)

Answer 10

Epiphysis

Proximal and distal

Question 11

Region of mature bone between the diaphysis and the epiphysis. Contains the epiphyseal plate.

Answer 11

Metaphysis

Question 12

In metaphysis. Thin layer of hyaline cartilage that provides for continued lengthwise bone growth. Remnant in adults termed the epiphyseal line.

Answer 12

Epiphyseal plate

Question 13

Tough, outer sheath covering the surface of a bone. Composed of dense irregular connective tissue. Protects bone from surrounding structures, attachment site for ligaments and tendons. Inner cellular layer contains osteoprogenitors, osteoblasts, and osteoclasts

Answer 13

Periosteum

Attached to bone by numerous collagen perforating fibers.

Question 14

Covers all internal surfaces of bone within the medullary cavity, like the bony struts if spongy bone. Incomplete layer of cells. Contains osteoprogenitors, osteoblasts, and osteoclasts.

Answer 14

Endosteum

Question 15

Blood supply of the bone?

Answer 15

Bone is highly vascularized, especially spongy bone. Vessels enter from the periosteum. Most bones have only one nutrient artery and one nutrient vein. A few bones, like the femur, have more than one of each.

Question 16

A tunnel that penetrates the diaphysis and provides access for the nutrient artery and/or vein. Branches of these large vessels supply the osteons of the compact bone before entering and supplying the medullary cavity.

Answer 16

Nutrient foramen

Question 17

Hemopoietic (blood cell forming). Contains reticular (loose) connective tissue, immature blood cells, and fat. Myeloid tissue

Answer 17

Red bone marrow

Question 18

Product of red bone marrow degeneration, blood vessels and adipocytes. May convert back to red bone marrow during severe anemia to facilitate the production of additional erythrocytes

Answer 18

Yellow bone marrow

Question 19

Stem cells derived from mesenchyme that produce cells that mature to become osteoblasts. Located in the periosteum and endosteum.

Answer 19

Osteroprogenitor cells.

Question 20

Cell that are often positioned side by side on bone surfaces. Synthesize and secrete osteoid through bone deposition. Initial semisolid form of bone matrix, later calcifies. Become entrapped in the matrix they produce. Differentiate into osteocytes.

Answer 20

Osteoblasts

Question 21

Mature bone cells derived from osteoblasts. Mostly retired but secrete chemicals to maintain the bone matrix and detect mechanical stress on the bone. If stress is detected, they may deposit new bone matrix by recruiting osteoblasts.

Answer 21

Osteocytes

Question 22

Large, multinuclear, phagocytic cells. Derived from fused bone marrow cells. Ruffled border to increase surface area exposed to bone. Often located within or adjacent to a depression or pit on the bone surface, termed resorption lacuna. Break down bones, bone reabsorption.

Answer 22

Osteoclasts.

Question 23

The unmineralized organic bone matrix produced by osteoblasts. Its organic components give bone tensile strength by resisting stretching and contribute to bone flexibility.

Answer 23

Osteoid

Question 24

To grow, bones need what?

Answer 24

Vitamin D enhances calcium absorption from the gastrointestinal tract. Vitamin C helps collagen formation. Calcium and phosphate for calcification.

Question 25

Small cylindrical structures that are the basic functional and structural unit of mature compact bone. Oriented parallel to cone diaphysis.

Answer 25

Osteons, Haversian system

Question 26

Lies at the center of the osteon and runs parallel to it. Blood vessels and nerves traveling here.

Answer 26

Central canal

Question 27

Rings of bone connective tissue that surround the central canal. Contains collagen fibers that give bone part of its strength and reliance.

Answer 27

Concentric lamellae

Question 28

Tiny interconnecting channels within bone connective tissue that extend from each lacunae and travel through the lamellae. Connect to others and central canal. House osteocyte projections

Answer 28

Canaliculi

Allows travel of nutrients, minerals, gases, and wastes between blood vessels and osteocytes.

Question 29

Run perpendicular to the central canals. They carry blood vessels, nerves from the periosteum that merge with the vessels in the central canals

Answer 29

Perforating (Volkmann) canals

Question 30

Runs the entire circumference of bone. Just inside the bone periosteum and outside the spongy bone. Adds strength to the bone as a whole.

Answer 30

Circumferential lamella

Question 31

Lamellae that are remnants of resorbed osteons

Answer 31

Interstitial lamellae

Question 32

Growth in length.

Growth from inside. Depends on the cartilage growth on the epiphyseal plate.

Answer 32

Interstitial cartilage growth

Question 33

Growth in width, growth from outside in

Thickness and remodeling of all bones by osteoblasts and osteoclasts on bone surfaces.

Answer 33

Appositional cartilage growth

Question 34

Bone develops from a thin layer of mesenchymal cells referred to as a membrane. Centrally located mesenchymal cells cluster and differentiate into osteoblasts, forming an ossification center. Osteoid is secreted within the membrane and calcifies. Woven bone and periosteum form, which turns into lamellar bone and red marrow.

Answer 34

Intramembraneous ossification.

Produces flat bones of the skull, some of the facial bones, mandible, and central part of the clavicle.

Question 35

Begins with a hyaline cartilage model, and requires breakdown of hyaline cartilage prior to ossification. Cartilage in the center of the diaphysis calcifies, with the periosteal bud and spongy bone/medullary beginning to form in cavities. Then the epiphysis ossify at the end.

Answer 35

Endochondral ossifcation
Produces most bones of the skeleton, including bones of the limbs, pelvis, vertebrae, and ends of the clavicle.
At the end, hyaline cartilage remains only in the epiphyseal plates and articular cartilages.

Question 36

First zone nearest the epiphysis, composed of small chondrocytes distributed throughout the matrix. Resembles mature hyaline cartilage and secures epiphysis to the plate.

Answer 36

Zone of resting cartilage (reserve cartilage)

Question 37

Second zone, chondrocytes undergo rapid mitotic divison, and become aligned into longitudinal columns of flattened lacunae. Columns parallel to diaphysis.

Answer 37

Zone of proliferating cartilage

Question 38

Third zone, chondrocytes cease to divide and begin to hypertrophy. Walls of the lacuna become thin.

Answer 38

Zone of hypertrophic cartilage

Question 39

Fourth zone, composed of 2-3 layers of chondrocytes. Minerals deposited between columns of lacunae. Destroys chondrocytes.

Answer 39

Zone of calcified cartilage

Question 40

Fifth zone. The walls break down between lacunae in columns and spaces invaded by capillaries and osteoprogenitor cells. New bone matrix deposited on the calcified cartilage matrix.

Answer 40

Zone of ossification

Question 41

Occurs in weight-bearing movement and exercise, required for normal bone remodeling. Detected by osteocytes and communicated to osteoblasts to increase synthesis of osteoid.

Answer 41

Mechanical stress

Causes increase in bone strength and results from skeletal contraction and gravitational forces

Question 42

Calcium is required for?

Answer 42

Initiation of muscle contraction. Exocytosis of molecules from cells, including neurons. Stimulation of the heart by pacemaker cells. Blood clotting.

Question 43

Hormones that regulate blood calcium levels?

Answer 43

Calcitriol (vit D) stimulates Ca++ absorption from the small intestine into the blood.
Parathyroid hormone (parathyroid glands)
Calcitonin (thyroid gland)

Question 44

Disease caused by Vit D deficiency in childhood. Characterized by deficient calcification of osteoid tissue. Acquires bowlegged appearance. Disturbances growth, hypocalcemia, and tetany from low blood calcium.

Answer 44

Rickets

Continues to occur in developing nations and increasing in urban US children

Question 45

Characterized by abnormal conversion of hyaline cartilage to bone. Long bones of limbs stop growing during childhood while others continue to grow normally.

Answer 45

Achondroplasia (dwarfism, most commonly)

Results from a failure of the chondrocytes in plate to grow and enlarge causing too little endochondral ossification .

Question 46

Red bone marrow transplant may be required if it’s destroyed or abnormally functioning. Harvested cells injected into bloodstream of patient, migrate to normal locations.

Answer 46

Bone marrow transplant

Question 47

Reduced bone mass sufficient to compromise normal function. Occurs in a significant percentage of older women, less men. Weakened bones due to fracture, especially at wrist, hip, vertebrae. Smoking, white people.

Answer 47

Osteoporosis
Reduced hormones with age like growth hormone, estrogen, and testosterone contributes to reduction in bone mass.
Best treatment is prevention with diet and physical activity in young adults.

Question 48

Thin break in a bone caused by increased physical activity.

Answer 48

Stress fracture

Question 49

Break in a bone that occurs because of weakening by disease

Answer 49

Pathologic fracture

Question 50

Broken bone not penetrating the skin

One of both ends piercing overlying skin

Answer 50

Simple fracture

Compound fracture

Question 51

Bone fragments into three more pieces. Particularly common in the aged, whose bones are more brittle.

Answer 51

Comminuted fracture

Question 52

Bone is crushed, common in porous bones (osteoporosis) subjected to extreme trauma, like a fall

Answer 52

Compression fracture

Question 53

Ragged break occurs when excessive twisting forces are applied to a bone. Common sports fracture.

Answer 53

Spiral fracture

Question 54

Epiphysis separates from the diaphysis along the plate. Tends to occur where cartilage cells are dying and calcification of the matrix is occurring.

Answer 54

Epiphyseal fracture

Question 55

Broken bone is depressed inward, typical of skull fracture

Bone breaks incompletely, only side of the shaft breaks. Common in children with more organic matrix.

Answer 55

Depressed fracture

Greenstick fracture

Question 56

Four steps in fracture repair? Simple fracture about 2-3 months, compound is longer. Slower with age.

Answer 56

A hematoma forms. A fibrocartilaginous callus forms. A hardy, bony callus forms. The bone is remodeled.

Question 57

Functions of the skeletal system?

Answer 57

Protection, mineral storage and acid-base homeostasis, blood cell formation, fat storage, movement, support

Question 58

Specialized bones located within tendons. Generally small, relatively flat, and oval-shaped. Give tendon a mechanical advantage, providing better leverage for muscles, and also reduce wear and tear on the tendon. Patella.

Answer 58

Sesamoid bones

Question 59

Explain the extracellular matrix of bone.

Answer 59

65% of the total weight of bone is inorganic matrix, which is composed of minerals.
35% is organic matrix, which contains the usual ECM stuff.