Endochondral Ossification and Postnatal Growth
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Questions and Answers

What is the primary type of cartilage involved in endochondral ossification?

  • Fibrocartilage
  • Hyaline cartilage (correct)
  • Articular cartilage
  • Elastic cartilage

    • Chondrocytes die and disintegrate during the process of endochondral ossification.

    True

    Which cells convert from the perichondrium to contribute to bone formation in endochondral ossification?

    Osteoblasts

    The process of replacing cartilage with bone is known as __________ ossification.

    <p>endochondral</p> Signup and view all the answers

    Match the following steps of endochondral ossification with their descriptions:

    <p>Step 1 = Chondrocytes enlarge and die, leaving cavities Step 3 = Osteoblasts produce spongy bone at the primary ossification center Step 4 = Remodeling occurs, creating a marrow cavity Step 5 = Capillaries and osteoblasts migrate into epiphyses</p> Signup and view all the answers

    During which step of endochondral ossification do blood vessels penetrate the cartilage?

    <p>Step 3</p> Signup and view all the answers

    Secondary ossification centers are developed at the diaphysis of long bones.

    <p>False</p> Signup and view all the answers

    What structure forms the marrow cavity during endochondral ossification?

    <p>Medullary cavity</p> Signup and view all the answers

    As blood vessels grow around the edges of the cartilage, the ____________ converts to osteoblasts.

    <p>perichondrium</p> Signup and view all the answers

    What hormone is released by the parathyroid glands in response to low calcium levels in the blood?

    <p>Parathyroid hormone</p> Signup and view all the answers

    Calcitonin decreases the activity of osteoclasts when calcium levels in the blood are high.

    <p>True</p> Signup and view all the answers

    What law states that bones are remodeled in response to the forces placed on them?

    <p>Wolff's law</p> Signup and view all the answers

    Vitamin K and B12 are required for the synthesis of proteins in normal bone, particularly large amounts of _______.

    <p>collagen</p> Signup and view all the answers

    Match the following hormones with their functions:

    <p>Parathyroid hormone = Stimulates osteoclast activity Calcitonin = Inhibits osteoclast activity Osteoblasts = Builds bone Osteoclasts = Dissolves bone</p> Signup and view all the answers

    What happens to bones that are not regularly stressed?

    <p>They become weaker</p> Signup and view all the answers

    What happens to chondrocytes in the epiphyseal plate during bone growth?

    <p>They continuously divide and grow.</p> Signup and view all the answers

    Bone development from hyaline cartilage is complete after birth.

    <p>False</p> Signup and view all the answers

    What type of cells migrate towards the epiphysis to replace cartilage with bone?

    <p>Osteoblasts</p> Signup and view all the answers

    The process of replacing cartilage with bone is known as ___ during postnatal growth.

    <p>ossification</p> Signup and view all the answers

    Match the following processes with their descriptions:

    <p>Calcification = The process where cartilage matrix hardens Osteoblasts = Cells that build new bone Chondrocytes = Cartilage cells that help in growth Osteoclasts = Cells that break down old bone</p> Signup and view all the answers

    During which stage is the epiphyseal cartilage most active?

    <p>During childhood and adolescence</p> Signup and view all the answers

    Growth in bone length is primarily achieved by the breakdown of existing bone.

    <p>False</p> Signup and view all the answers

    What role do mesenchymal cells play in bone development?

    <p>They develop into chondroblasts, forming the cartilage model.</p> Signup and view all the answers

    Chondrocytes in the primary ossification site start to secrete ___ for mineral deposition.

    <p>alkaline phosphatase</p> Signup and view all the answers

    Which hormone is involved in the control of bone growth?

    <p>Growth hormone</p> Signup and view all the answers

    Which hormone is primarily responsible for promoting osteoblast activity from the pituitary gland?

    <p>Growth Hormone</p> Signup and view all the answers

    What type of cells are osteoprogenitor cells transformed into during bone formation?

    <p>Osteoblasts</p> Signup and view all the answers

    The hormone calcitriol is derived from vitamin D3 and is secreted by the thyroid gland.

    <p>False</p> Signup and view all the answers

    Mature chondrocytes can divide and regenerate.

    <p>False</p> Signup and view all the answers

    Name one vitamin required for collagen synthesis in bone growth.

    <p>Vitamin C</p> Signup and view all the answers

    What is the role of osteoblasts in bone remodeling?

    <p>To build new bone by secreting osteoid.</p> Signup and view all the answers

    ___ is responsible for the absorption of Ca++ and PO4 ions from the digestive tract during bone growth.

    <p>Calcitriol</p> Signup and view all the answers

    Which of the following nutrients is NOT essential for bone growth?

    <p>Vitamin B12</p> Signup and view all the answers

    During appositional growth, osteoblasts in the periosteum build new __________ lamellae.

    <p>circumferential</p> Signup and view all the answers

    Match the following processes to their descriptions:

    <p>Bone resorption = Breakdown of old bone Osteoid secretion = Production of bone matrix by osteoblasts Appositional growth = Increase in bone diameter Bone remodeling = Replacement of old bone with new bone</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Estrogen = Causes osteoblasts to produce bone faster Thyroxine = Stimulates cell metabolism Vitamin A = Stimulates osteoblast activity Vitamin C = Required for collagen synthesis</p> Signup and view all the answers

    Which hormones influence the replacement of cartilage at the epiphyseal plate during puberty?

    <p>Sex hormones, growth hormone, and thyroid hormone</p> Signup and view all the answers

    Sex hormones cause the epiphyseal plates to become narrower during puberty.

    <p>True</p> Signup and view all the answers

    Osteoclasts are involved in building new bone.

    <p>False</p> Signup and view all the answers

    What condition can result from a deficiency of calcium and phosphate salts in children?

    <p>Rickets</p> Signup and view all the answers

    The __ supply to the bone includes sensory nerve endings that are richly distributed throughout the bone.

    <p>nerve</p> Signup and view all the answers

    What happens to the medullary cavity during appositional growth?

    <p>It enlarges and increases in diameter.</p> Signup and view all the answers

    Which vitamin is essential for stimulating osteoblast differentiation?

    <p>Vitamin C</p> Signup and view all the answers

    Bone remodeling occurs throughout life and involves the resorption of old bone and deposition of __________ bone.

    <p>new</p> Signup and view all the answers

    Why do sharks have a skeleton made of cartilage instead of bone?

    <p>Cartilage allows for greater flexibility and buoyancy</p> Signup and view all the answers

    Study Notes

    Endochondral Ossification

    • Most bones develop via endochondral ossification.
    • Involves replacing hyaline cartilage with bone.
    • The process starts with a hyaline cartilage model.
    • The model enlarges and chondrocytes in the center of the shaft die, leaving cavities.
    • Blood vessels invade the cartilage, and the perichondrium transforms into periosteum.
    • Osteoblasts in the periosteum create a bone collar around the cartilage shaft.
    • Blood vessels penetrate the cartilage, and osteoblasts form spongy bone at the primary ossification center.
    • The bone shaft thickens, and a marrow cavity forms.
    • Capillaries and osteoblasts migrate into the epiphyses, creating secondary ossification centers.
    • Epiphyses eventually fill with spongy bone, leaving only a thin layer of articular cartilage at the joint surface.
    • An epiphyseal cartilage separates the epiphysis from the diaphysis, allowing for longitudinal growth.

    Postnatal Bone Growth

    • Continued growth in bone length occurs through the epiphyseal plate.
    • Chondrocytes in the epiphyseal plate divide and grow, adding length to the bone.
    • Chondrocytes closest to the diaphysis die, and are replaced by osteoblasts.
    • Bone growth is under hormonal control and ends after puberty.
    • Lateral bone growth occurs through appositional growth, where osteoblasts in the periosteum lay down new bone.
    • Osteoclasts in the medullary cavity break down old bone, widening the cavity.

    How Osteons Form

    • Ridges in the periosteum create a groove for a blood vessel.
    • Periosteum ridges fuse, forming a tunnel lined by endosteum.
    • Osteoblasts in the endosteum build new concentric lamellae inward, forming a new osteon.
    • Bone growth outwards occurs as osteoblasts in the periosteum build new circumferential lamellae.
    • This process of osteon formation repeats as new periosteum ridges fold over blood vessels.

    Bone Remodeling

    • Bone remodeling occurs throughout life, involving resorption of old bone and deposition of new bone.
    • Remodeling is influenced by factors like bone growth, blood calcium levels, and mechanical stress.
    • Wolff's Law describes the relationship between mechanical stress and bone remodeling.
    • Stress on the bone produces electrical currents that stimulate osteoblasts, leading to increased bone density and strength.
    • Unstressed bones become weaker due to reduced osteoblast activity.

    Repair of Fractures

    • Fracture repair involves realignment of bone fragments, immobilization to prevent movement, and a healing process.
    • Open or compound fractures occur when the broken bone pierces the skin.

    Blood Supply and Nerve Supply to Bone

    • Bones are richly supplied with blood vessels that provide nourishment and oxygen.
    • The periosteum, endosteum, and bone itself are supplied with nerves.

    Hormonal and Nutritional Requirements for Bone Growth

    Hormonal

    • Growth hormone from the pituitary gland promotes osteoblast activity at the epiphyseal plates.
    • Thyroid hormone (thyroxine) also stimulates osteoblast activity and cell metabolism.
    • Calcitriol, produced by the kidneys from Vitamin D3, helps regulate calcium and phosphate absorption from the digestive tract.
    • Sex hormones (estrogen and testosterone) enhance growth and increase bone production by osteoblasts.

    Nutritional

    • Adequate calcium and phosphate salts are essential for bone formation.
    • Deficiencies can lead to rickets (children) or osteomalacia (adults).
    • Vitamin C is vital for collagen synthesis, stimulating osteoblast differentiation.
    • Vitamin A stimulates osteoblast activity.
    • Vitamins K and B12 are required for synthesis of proteins essential for normal bone structure.

    Regulation of Bone Remodeling

    • Bone remodeling is regulated by hormones to maintain blood calcium levels within a narrow range.
    • The parathyroid glands release parathyroid hormone in response to low blood calcium levels.
    • Parathyroid hormone increases osteoclast activity, intestinal calcium absorption, and reduces calcium excretion in the kidneys.
    • The thyroid gland secretes calcitonin in response to high blood calcium levels.
    • Calcitonin inhibits osteoclast activity, increases calcium excretion in the kidneys, and reduces intestinal calcium absorption.

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    Description

    Explore the fascinating process of endochondral ossification, where hyaline cartilage is transformed into bone. This quiz covers the stages of bone development, including primary and secondary ossification centers and the implications for postnatal bone growth. Test your understanding of how bones grow and develop in the human body.

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