Chapter 6

Vitamin C is required for the synthesis of collagen. Collagen fiber synthesis decreases with inadequate vitamin C intake and bones become more brittle and shatter. Vitamin K is believed to aid in the production of calcium-ion binding glycoproteins by osteoblasts. Inadequate vitamin K may decrease bone deposition. Thus, bones may not be able to resist compression.

A digestive system disease has inhibited Mr. Sumner's ability to absorb vitamins. Explain how the bones are affected when there are inadequate levels of vitamins C and K.

Osteoclasts are active in bone resorption while osteoblasts are active in bone deposition. If osteoclast activity exceeds osteoblast activity, more bone will be resorbed then deposited.

A hypothetical drug reduces osteoblast activity, but has no effect on osteoclast activity. Predict the effects of this hypothetical drug on bone resorption and bone deposition.

The epiphyseal plates have ossified and further growth in length is not possible.

A radiograph reveals epiphyseal lines in the long bones of a 12-year-old's hand. What statement is correct?

growth in width.

Appositional growth produces:

appositional bone growth increases.

As a result of the increase of testosterone at puberty for males:

long bones.

Bone growth in length occurs at the epiphyseal plate in:

osteogenic cells.

Cells that develop into osteoblasts are:

diaphysis

Charlie has a break in the shaft of his thigh bone. He broke the

Primary bone is the first, immature bone formed by both intramembranous and endochondral ossification. Primary bone consists of irregularly arranged collagen bundles, abundant osteocytes, and little inorganic matrix. In most cases, primary bone is resorbed by osteoclasts and replaced by mature secondary bone. Secondary bone has fully formed lamellae with regularly arranged collagen bundles that are parallel to one another, which makes it much stronger than primary bone. In addition, secondary bone contains a higher percentage of inorganic matrix, which contributes to its strength.

Explain how primary bone differs from secondary bone.

Red bone marrow consists of loose connective tissue supporting islands of blood-forming, or hematopoietic, cells. Yellow bone marrow, which stores triglycerides, consists mostly of blood vessels and adipocytes.

Explain how red bone marrow and yellow bone marrow differ structurally.

bone deposition exceeds bone resorption

For a person who starts running for exercise

short bones

How are carpals and tarsals classified by shape?

An epiphyseal plate consists of five zones of hyaline cartilage that are involved in longitudinal growth of bones. By around age 18-21, the zone of ossification completely ossifies and the epiphyseal plate is said to be closed. The epiphyseal plate leaves behind a calcified remnant known as an epiphyseal line that is incapable of producing longitudinal growth.

How does an epiphyseal plate differ from an epiphyseal line?

6-8 weeks

How long does bone repair generally take?

The bone would be more flexible

How would the removal of hydroxyapatite crystals from bone matrix affect the physical properties of a bone?

epiphyseal plate

Layer of hyaline cartilage where longitudinal growth occurs in a long bone

osteoclasts are to bone resorption.

Osteoblasts are to bone deposition as:

2. A hematoma fills the gap between bone fragments. 4. Fibroblasts and chondroblasts infiltrate the hematoma and a soft callus forms. 3. Osteoblasts built a new bone callus. 1. The bone callus is remodeled and primary bone is replaced with secondary bone.

Place the following steps of bone repair in the correct sequence. 1. The bone callus is remodeled and primary bone is replaced with secondary bone. 2. A hematoma fills the gap between bone fragments. 3. Osteoblasts built a new bone callus. 4. Fibroblasts and chondroblasts infiltrate the hematoma and a soft callus forms.

diaphysis.

Primary ossification centers develop in long bones in the:

longitudinal growth

Proliferation of cells in the epiphyseal plate promotes this type of bone growth

endochondral ossification

Testosterone accelerates the closure of epiphyseal plates during this type of ossification

epiphyseal line

The appearance of this structure signals the end of bone growth

is located within tendons

The patella is classified as a sesamoid bone since it:

perforating (Sharpey's) fibers.

The periosteum is secured to underlying bone by collagen fibers called:

long bone

The presence of a diaphysis is indicative of this bone shape

lacuna

The small, fluid-filled cavity occupied by an osteocyte is called a(n):

osteons

The structural units of mature compact bone are called:

internal layer of spongy bone in flat bones

The term diploë refers to the:

articular cartilage

What persists for life?

pressure

What promotes bone resorption?

vitamin D

What vitamin deficiency causes rickets in children?

osteoblasts

Which cells participate in the process of bone deposition?

vitamin D

Which dietary requirement for bone health can be made in response to skin exposure to UV light?

The person who routinely exercises will experience a greater amount of bone deposition due to the stresses experienced by the bones. The heavier load a bone must carry, the more bone tissue is deposited to that bone. The sedentary person will experience a lesser amount of bone deposition since there is less stress applied to the bones

Who experiences a greater amount of bone deposition: a person who routinely exercises or a sedentary person? Explain your choice.

infants

Whose bone marrow is mostly red?

Derrick may not spend enough time in the sun, exposed to UV light. Vitamin D is made by the skin in response to exposure to UV light. Vitamin D increases calcium ion absorption in the intestines. Without vitamin D, Derrick may have inadequate bone deposition due to lack of calcium and thus have a lower bone mass.

Derrick has a vitamin D deficiency. Hypothesize an explanation for why he may have this deficiency.

Osteoblasts develop in the primary ossification center and secrete organic matrix, which calcifies. In a few days' time, calcification occurs and the early bone hardens. Trapped osteoblasts then become osteocytes. Osteoblasts continue to lay down new bone, forming the trabeculae of early spongy bone.

Describe the role of osteoblasts in intramembranous ossification.

Osteoblasts are bone-forming cells that perform the process of bone deposition. Osteoblasts build up the bone ECM by secreting the organic matrix and aid in the formation of the inorganic matrix. Osteoclasts are responsible for the process of bone resorption, during which they break down the bone ECM using enzymes and hydrogen ions.

Discuss how the osteoblast differs functionally from the osteoclast

Ossification is the process of converting connective tissue, such as cartilage, into bone tissue. Calcification refers to the deposition of calcium salts in any tissue, including cartilage and bone.

Discuss the difference between ossification and calcification.

primary bone

During ossification, this initial type of bone consists of irregularly arranged collagen bundles, abundant osteocytes, and little inorganic matrix

Jerry has acromegaly, a condition that arises from excessive appositional growth. His condition is due to excessive growth hormone after the closure of the epiphyseal plates. Jerry's bones will grow much wider, not longer, as bone deposition by osteoblasts will exceed bone resorption. Acromegaly also affects the growth of cartilage and soft tissue.

Jerry, a 42-year-old male, is experiencing excessive appositional growth. Determine his condition, the cause of his condition, and explain the impact on his bones.

Collagen fibers help bone resist torsion.

Why are collagen fibers a critical component of bone?

long bones

Bones with a diaphysis and epiphyses are classified as:

hematopoiesis

Blood cells are made in the red bone marrow of bones, a process known as:

calcium, vitamin C, and vitamin K.

Bone growth and remodeling depends on adequate intake of:

calcium

Bone is the most important storehouse in the body for:

osteoclasts.

Bone resorption requires the activity of:

osteoclast

Bones are constantly undergoing resorption for various reasons. Which of the following cells accomplishes this process?

trabeculae

Branching "ribs" of bone present in spongy bone are known as:

The predominant protein fibers in bone are collagen fibers. Collagen fibers form cross-links with one another and help bone to resist torsion (twisting) and tensile (pulling or stretching) forces. They also align with hydroxyapatite crystals, significantly enhancing the hardness of bone. Collagen fibers are one of the most important components of the bone ECM in terms of strength; when these fibers become inadequate or defective, bone weakens and any minor twisting force may break it.

Brittle bone disease (osteogenesis imperfecta) usually results from a collagen deficiency. Explain how a collagen deficiency affects bone structure.

increase bone deposition.

Calcitonin functions to:

No, calcification must occur before ossification is possible during longitudinal growth. During longitudinal growth, chondrocytes die and their matrix calcifies. Chondrocytes then reach the zone of calcification. Here, chondrocytes are quite far from the blood supply, which causes them to die and their ECM to accumulate calcium salt deposits. Calcified cartilage is replaced with bone. In the final zone, the zone of ossification, osteoblasts invade the calcified cartilage and begin to lay down bone on top of it.

Can ossification occur without calcification during longitudinal growth? Explain.

3. Perichondrium is invaded by blood vessels. 5. Perichondrial cells differentiate into osteogenic cells then into osteoblasts. 2. Osteoblasts build the bone collar on the external surface of the bone. 1. Chondrocytes die. 4. In the primary ossification center, osteoblasts replace calcified cartilage with early spongy bone.

Correctly order the following key steps in the process of endochondral ossification. 1. Chondrocytes die. 2. Osteoblasts build the bone collar on the external surface of the bone. 3. Perichondrium is invaded by blood vessels. 4. In the primary ossification center, osteoblasts replace calcified cartilage with early spongy bone. 5. Perichondrial cells differentiate into osteogenic cells then into osteoblasts.

by pushing the epiphysis away from the diaphysis.

In the epiphyseal plate, cartilage grows:

Short, flat, irregular, and sesamoid bones do not have diaphyses or epiphyses. Your professor must be presenting a long bone for study. Long bones possess a shaft, known as a diaphysis, and enlarged, rounded ends, known as epiphyses.

In the laboratory, your professor presents a bone for study. She explains it has a diaphysis and epiphyses. Determine the type of bone, by shape, that she has presented and explain how you came to your conclusion.

appositional growth

In this type of bone growth, new circumferential lamellae are formed

skull bones.

Intramembranous ossification occurs in:

calcitonin

Which hormone, produced by the thyroid gland, works opposite to parathyroid hormone (PTH)?

Intramembranous ossification begins when osteoblasts develop in the primary ossification center. Osteoblasts secrete organic material, which calcifies. Early spongy bone is formed, and then early compact bone is formed.

Outline the events of intramembranous ossification

Like testosterone, estrogen increases the rate of longitudinal bone growth, inhibits osteoclasts, and accelerates closure of the epiphyseal plate, although it has a much more potent effect on epiphyseal plate closure than does testosterone. Earlier closure of the epiphyseal plate stops longitudinal growth in women earlier. This is partly the reason why women are generally shorter in stature than men.

Relate puberty and increased testosterone and estrogen production to the relative heights of men and women

osteocytes

Relatively inactive bone cells that help to maintain the ECM are:

endochondral ossification.

Secondary ossification centers are characteristic of:

Four of the five zones of cells associated with the epiphyseal plate are actively involved in longitudinal growth. Most of the mitotic activity occurs in the zone of proliferation. Longitudinal growth continues at the epiphyseal plate as long as mitosis is happening in the zone of proliferation. If Matthew damaged this particular zone, he may experience impaired growth in that particular epiphyseal plate of his femur as he grows.

Six-year-old Matthew broke his femur and one of his epiphyseal plates was damaged. Explain the role of the epiphyseal plate in longitudinal growth and predict the effects of a damaged epiphyseal plate on his future longitudinal growth.

An osteon includes lamellae, a central canal, lacunae, and canaliculi. Lamellae are concentric rings of compact bone formed around a central (Haversian) canal which contains blood vessels and nerves. Lacunae are small cavities filled with extracellular fluid located between the lamellae. Osteocytes reside within lacunae. Canaliculi connect lacunae to each other. Cytoplasmic extensions of osteocytes contact other osteocytes through these canaliculi

Summarize the components of an osteon of compact bone tissue.

There are two types of ossification-intramembranous and endochondral. The bones formed by intramembranous ossification are built on a model made of a membrane of embryonic connective tissue. The bones formed by endochondral ossification are built on a model made of hyaline cartilage. Many flat bones, including the bones of the skull and the clavicles, form during fetal development by the process of intramembranous ossification. All the bones in the body below the head, except the clavicles, form by the process of endochondral ossification.

Summarize the differences between intramembranous and endochondral ossification.

Upon fracture, 1) a hematoma fills the gap between the bone fragments. 2) Fibroblasts and chondroblasts infiltrate the hematoma and a soft callus forms. 3) Osteoblasts build a new bony callus. 4) The bone callus is remodeled and primary bone is replaced with secondary bone.

Summarize the four steps of bone repair

compact bone

The diaphyses of long bones are created by a thick layer of this type of bone

triglyceride storage.

The function of yellow bone marrow is:

circumferential lamellae.

The layers of bone tissue immediately deep to the periosteum are:

appositional growth

What type of bone growth do you think a 40-year-old male experiences?

flat bones

Thin, broad bones should be classified as:

flat bone

Thin, broad bones such as the ribs and sternum

spongy bone

What type of bone is adapted to withstand stresses arriving from many directions?

spongy bone

What type of bone is illustrated?

secondary bone

This type of bone is also known as lamellar bone

spongy bone

This type of bone is characterized by the presence of trabeculae

calcium salts

What accounts for the majority of bone (osseous) tissue matrix?

lamellae canaliculi lacunae

What are the components of an osteon?

Growth hormone increases the rate of mitosis in the epiphyseal plate of growing bones. Growth hormone increases the activity of osteogenic cells. Growth hormone directly stimulates osteoblasts in the periosteum to promote appositional growth.

What are the effects of a growth hormone?

blood cell formation protection of internal organs mineral storage

What are the functions of the skeletal system?

Primary bone contains abundant osteocytes and little inorganic matrix

What best describes primary bone?

canaliculi

What canals connect lacunae together?

osteoblasts

What cells contribute to the process of calcification during intramembranous ossification?

PTH stimulates the intestines to absorb calcium ions. PTH stimulates osteoclast activity. PTH weakens the bones.

What correctly depicts the effects of parathyroid hormone (PTH)?

Fibroblasts form new collagen fibers to bridge the gap between bone fragments.

What do fibroblasts contribute to bone repair?

parathyroid hormone (PTH)

What hormone promotes an increase in the activity of osteoclasts?

hematoma formation

What is the first step of bone repair?

ossification

What is the last process to occur in the epiphyseal plate?

ossification of the zone of proliferation

What prompts the closure of the epiphyseal plate around age 18-21?

low blood calcium ion levels

What stimulates the release of parathyroid hormone (PTH)?

epiphyseal plate

What structure allows the diaphysis of the bone to increase in length?

calcification

What term implies bone deposition via osteoblasts?

hyaline cartilage

What tissue serves as the model for bones formed during endochondral ossification?

In the primary ossification center, osteoblasts replace the calcified cartilage with early spongy bone; the secondary ossification centers and medullary cavity develop. Osteoclasts etch a hole in the bone collar that allows a group of blood vessels and bone cells to enter the primary ossification center. Here, osteoblasts replace the calcified cartilage with early spongy bone while other osteoblasts continue to increase the size of the bone collar. As this happens, the cavities enlarge and combine, forming the medullary cavity.

Why does the medullary cavity develop during endochondral ossification? Explain.

Articular cartilage allows bones to rub together with reduced friction at joints

Why is articular cartilage necessary for long bones?

zone of proliferation

Within the epiphyseal plate, which zone houses actively dividing cartilage cells in their lacunae?