Ch. 6 Bones and Skeletal Tissues

Hoehn - Marieb Human Anatomy & Physiology, 12th edition

Hoehn, Haynes, Abbott12th EditionMarieb Human Anatomy & PhysiologyISBN: 9780138242732Not the one you use?Change textbook

Hoehn, Haynes, Abbott 12th Edition

Ch. 6 Bones and Skeletal Tissues

Problem 10

Chapter 6, Problem 10

Describe in proper sequence the events of endochondral ossification in a long bone.

Verified step by step guidance

Begin by understanding that endochondral ossification is the process by which long bones develop from a cartilage template, specifically hyaline cartilage.

Step 1: The cartilage model grows in size, and chondrocytes (cartilage cells) in the center of the diaphysis (shaft) enlarge and then die, creating a cavity; this is called the primary ossification center formation.

Step 2: Blood vessels invade the cavity, bringing osteoblasts (bone-forming cells) that start depositing bone matrix over the remnants of calcified cartilage, forming the bone collar around the diaphysis.

Step 3: The primary ossification center expands toward the epiphyses (ends of the bone), replacing cartilage with spongy bone, while the periosteum forms on the outside.

Step 4: Secondary ossification centers develop in the epiphyses after birth, where similar processes occur but spongy bone remains inside, and the epiphyseal plate (growth plate) remains between the diaphysis and epiphysis to allow for continued lengthwise growth.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Endochondral Ossification

Endochondral ossification is the process by which growing cartilage is systematically replaced by bone to form the long bones of the body. It involves the transformation of a cartilage template into bone tissue, essential for the development and growth of the skeletal system.

Stages of Endochondral Ossification

The process occurs in a specific sequence: formation of cartilage model, development of the primary ossification center, vascular invasion, formation of the medullary cavity, development of secondary ossification centers, and finally, formation of articular cartilage and epiphyseal plate. Each stage is critical for proper bone formation.

Role of Chondrocytes and Osteoblasts

Chondrocytes initially produce the cartilage matrix and later undergo hypertrophy and apoptosis, signaling bone formation. Osteoblasts then invade the area to deposit bone matrix, replacing cartilage with bone. The coordinated activity of these cells drives the ossification process.

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Textbook Question

The disorder in which bones are porous and thin but bone composition is normal is

a. Osteomalacia

b. Osteoporosis

c. Paget's disease

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Textbook Question

A bone with approximately the same width, length, and height is most likely:

a. A long bone

b. A short bone

c. A flat bone

d. An irregular bone

Wolff's law is concerned with:

a. Calcium homeostasis of the blood

b. The shape of a bone being determined by mechanical stresses placed on it

c. The electrical charge on bone surfaces

Osteocytes residing in lacunae of osteons of healthy compact bone are located quite a distance from the blood vessels in the central canals, yet they are well nourished. How can this be explained?

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Textbook Question

Formation of the bony callus in fracture repair is followed by:

a. Hematoma formation

b. Fibrocartilaginous callus formation

c. Bone remodeling

d. Formation of granulation tissue

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Textbook Question

As we grow, our long bones increase in diameter, but the thickness of the compact bone of the shaft remains relatively constant. Explain this phenomenon.

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