Sections 5.1 - 5.2

Which of the following accounts for almost two-thirds the weight of bone?

Calcium phosphate

Which of the following is a function of the skeletal system?

- Protection - support - leverage

Which of the following is found at the ends of bones?

Epiphysis

Put the steps in endochondral ossification in order from beginning to end of the process. 1. Capillaries and osteoblasts penetrate the cartilage and invade the central region; osteoblasts begin producing spongy bone at the primary center of ossification; bone formation then spreads along the shaft toward both ends of the cartilaginous model. 2. As the cartilage enlarges, chondrocytes near the center of the shaft increase greatly in size, the matrix is reduced to a series of small struts that soon begin to calcify, and the enlarged chondrocytes die and disintegrate, leaving cavities within the cartilage. 3. Capillaries and osteoblasts migrate into the epiphysis, creating secondary ossification centers. 4. Blood vessels grow around the edges of the cartilage, and the cells of the perichondrium convert to osteoblasts. The shaft of the cartilage then becomes ensheathed in a superficial layer of bone. 5. Epiphyses are filled with spongy bone. Articular cartilage remains exposed to the joint cavity; over time it will be reduced to a thin superficial layer. At each metaphysis, an epiphyseal cartilage separates the epiphysis from the diaphysis. 6. Remodeling occurs as growth continues, and osteoclasts erode the central portion, creating a medullary cavity. The bone of the shaft becomes thicker, and the cartilage near each epiphysis is replaced by shafts of bone.

2. As the cartilage enlarges, chondrocytes near the center of the shaft increase greatly in size, the matrix is reduced to a series of small struts that soon begin to calcify, and the enlarged chondrocytes die and disintegrate, leaving cavities within the cartilage. 4. Blood vessels grow around the edges of the cartilage, and the cells of the perichondrium convert to osteoblasts. The shaft of the cartilage then becomes ensheathed in a superficial layer of bone. 1. Capillaries and osteoblasts penetrate the cartilage and invade the central region; osteoblasts begin producing spongy bone at the primary center of ossification; bone formation then spreads along the shaft toward both ends of the cartilaginous model. 6. Remodeling occurs as growth continues, and osteoclasts erode the central portion, creating a medullary cavity. The bone of the shaft becomes thicker, and the cartilage near each epiphysis is replaced by shafts of bone. 3. Capillaries and osteoblasts migrate into the epiphysis, creating secondary ossification centers. 5. Epiphyses are filled with spongy bone. Articular cartilage remains exposed to the joint cavity; over time it will be reduced to a thin superficial layer. At each metaphysis, an epiphyseal cartilage separates the epiphysis from the diaphysis.

Put the steps of intramembranous ossification in the correct order: 1. Entrapment of blood vessels within the bone 2. Differentiation of osteoblasts within the mesenchyme 3. Formation of spongy bone 4. Formation of bony spicules

2. Differentiation of osteoblasts within the mesenchyme 4. Formation of bony spicules 1. Entrapment of blood vessels within the bone 3. Formation of spongy bone

Place the steps of appositional bone growth in order. 1. The osteon is complete with new central canal around blood vessel. Second blood vessel becomes enclosed. 2. Ridges meet and fuse, trapping the vessel inside the bone. 3. Additional circumferential lamellae are deposited, and the bone continues to increase in diameter. 4. Bone formation at the surface of the bone produces ridges that parallel a blood vessel. 5. Ridges enlarge and create a deep pocket. 6. Bone deposition proceeds inward toward the vessel, beginning the creation of a typical osteon.

4. Bone formation at the surface of the bone produces ridges that parallel a blood vessel. 5. Ridges enlarge and create a deep pocket. 2. Ridges meet and fuse, trapping the vessel inside the bone. 6. Bone deposition proceeds inward toward the vessel, beginning the creation of a typical osteon. 3. Additional circumferential lamellae are deposited, and the bone continues to increase in diameter. 1. The osteon is complete with new central canal around blood vessel. Second blood

Which of the following is the correct description of the congenital disorder of the skeleton called achondroplasia?

Due to unusually slow growth of the epiphyseal cartilages in a child, affected adults have short, stocky limbs and abnormal proportions. Most cases result from spontaneous mutation.

Concerning the hormonal regulation of bone growth, which of the following statements is not true?

In children and pregnant women, calcitonin inhibits osteoblasts, and decreases the rate of calcium loss in the urine.

Which type of lamellae fill in the spaces between the osteons in compact bone?

Interstitial lamellae

Which of the following congenital disorders of the skeleton involves excessive cartilage formation at the epiphyseal cartilages, resulting in extremely long and slender limbs?

Marfan's syndrome

In the formation of blood and lymphatic supply, which vessels supply blood to the diaphyseal surface of each epiphyseal cartilage, where bone is replacing cartilage?

Metaphyseal vessels

Which vessels form as blood vessels invade the cartilage model at the start of endochondral ossification?

Nutrient artery and vein

Which cells in bone are considered "bone-forming" because they secrete the organic components of the bone matrix?

Osteoblasts

Which cell population of mature bone directs both the release of calcium from bone to blood and the deposition of calcium salts in the surrounding matrix?

Osteocytes

Which of the following statements about the skeletal system is FALSE?

Red blood cells, white blood cells, and platelets are produced in the yellow marrow, which fills the internal cavities of many bones

Which of the following accurately states a difference between compact bone and spongy bone?

Spongy bone is arranged into trabeculae.

Which of the following statements regarding factors that regulate bone growth is FALSE?

The active form of vitamin C, calcitriol, must be obtained from the diet.

Which vitamins are essential for normal bone growth and remodeling?

Vitamins A and C

After the perichondrium is converted to a periosteum, the inner osteogenic layer produces a thin layer of compact bone around the shaft of the cartilage known as __________.

bone collar

Which anatomical structures of the skeleton are complex, dynamic organs that contain osseous tissue, other connective tissue, smooth muscle, and neural tissue?

bones

Which of the following statements about intramembranous ossification is FALSE?

it begins when mesenchymal cells differentiate into osteoclasts within embryonic or fibrous connective tissue

Which of the following statements about the periosteum is FALSE?

it is an incomplete layer, with the thickness of one cell and with bone matrix occasionally exposed

Which function of the skeletal system changes the magnitude and direction of the forces generated by skeletal muscles?

leverage

Bone growth occurs when osteoblasts are creating more bone matrix than __________ are removing.

osteoclasts

Which bone structure isolates and protects the bone from surrounding tissues, provides a route and a place of attachment for circulatory and nervous supply, actively participates in bone growth and repair, and attaches the bone to the connective tissue network of the deep fascia?

periosteum

During the process of endochondral ossification, a major step occurs when the centers of the epiphyses begin to calcify. Capillaries and osteoblasts migrate into these areas, creating sites called __________.

secondary ossification centers