Growth and Development in Biology
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Questions and Answers

What is the primary determinant of growth according to the Functional Matrix Theory?

  • The soft tissue adjacent to bone (correct)
  • The proliferation of osteoblasts
  • The presence of intersphenoidal synchondrosis
  • The activity of osteocytes

At what age does the spheno-occipital synchondrosis typically close?

  • 3-5 years
  • 18-20 years (correct)
  • Before birth
  • 5-7 years

Which of the following is NOT a characteristic of endochondral bone formation?

  • Examples include epiphyseal plates and synchondroses
  • Involves osteogenic tissue replacement
  • Primarily occurs in the cranial vault (correct)
  • Presence of bands of cartilage

What is the first step in the process of intramembranous bone formation?

<p>Change of UMCs to osteoblasts (A)</p> Signup and view all the answers

How do sutures contribute to cranial growth?

<p>Through periosteal membrane activity (C)</p> Signup and view all the answers

Which synchondrosis closes at the earliest stage?

<p>Intersphenoidal synchondrosis (C)</p> Signup and view all the answers

What does the Classical Theory of growth inaccurately suggest about the growth of sutures?

<p>Sutures are growth centers themselves (A)</p> Signup and view all the answers

What type of bones are formed by synchondroses?

<p>Endochondral bone (D)</p> Signup and view all the answers

What are the primary characteristics of the condyles at birth?

<p>They are underdeveloped and will grow by endochondral growth. (A)</p> Signup and view all the answers

What process describes the growth of the posterior border of the ramus?

<p>It grows backward through progressive addition of bone. (B)</p> Signup and view all the answers

Which of the following statements regarding the alveolar process is correct?

<p>It resorbs with tooth extraction. (A)</p> Signup and view all the answers

Which factor is crucial for timing orthodontic treatment?

<p>Various growth spurts. (D)</p> Signup and view all the answers

What is a characteristic of the growth pattern explained by the V principle?

<p>Bone deposition occurs on the inner surface while resorption happens on the outer surface of the V. (B)</p> Signup and view all the answers

Which of the following growth spurts is classified as preventive measures in orthodontic treatment?

<p>Infantile spurt. (D)</p> Signup and view all the answers

How does the coronoid process primarily grow?

<p>By drift in a posterior direction, less than the ramus. (D)</p> Signup and view all the answers

What primarily influences the overall facial skeletal pattern during cranial base growth?

<p>Spheno-occipital synchondrosis growth (A)</p> Signup and view all the answers

What happens to the alveolar process as teeth erupt?

<p>It develops and increases in width. (A)</p> Signup and view all the answers

What type of growth predominantly occurs at the cranial base?

<p>Cartilaginous (endochondral) growth (D)</p> Signup and view all the answers

Which sequence correctly describes the growth dimensions of the middle face?

<p>Width, depth, height (D)</p> Signup and view all the answers

What change occurs in the gonial angle of the mandible from childhood to adulthood?

<p>Decreases from 175° to 115° (B)</p> Signup and view all the answers

Which type of growth does the mandible undergo at the condyle?

<p>Endochondral growth (C)</p> Signup and view all the answers

What process is involved in the growth of the maxillary complex in terms of surface deposition?

<p>Intramembranous growth at sutures (B)</p> Signup and view all the answers

Which of the following is a result of vertical growth in the nasomaxillary complex?

<p>Outward and downward growth of the maxillary complex (C)</p> Signup and view all the answers

What is the primary growth mechanism for the rest of the mandible, excluding the condyle and symphysis?

<p>Intramembranous ossification (B)</p> Signup and view all the answers

What is primarily involved in drift during craniofacial bone enlargement?

<p>Resorption on one side and deposition on the opposite side (A)</p> Signup and view all the answers

Which type of displacement involves movement in the opposite direction to the growth of the bone?

<p>Primary displacement (D)</p> Signup and view all the answers

What characterizes the type of growth known as remodeling?

<p>Change in size and shape due to differential resorption and deposition (D)</p> Signup and view all the answers

During craniofacial bone growth, which structure is subjected to endochondral ossification?

<p>Cartilage structures like the epiphyseal plates (D)</p> Signup and view all the answers

Which of the following bones are included in the cranial vault?

<p>Frontal and parietal bones (D)</p> Signup and view all the answers

What is the main role of sutural growth in the craniofacial complex?

<p>Expansion of the cranial vault width (C)</p> Signup and view all the answers

What process occurs when soft tissue expansion leads to skeletal growth?

<p>Endochondral ossification (B)</p> Signup and view all the answers

Which of the following events exemplifies secondary displacement?

<p>Naso-maxillary complex moves in relation to the cranial base (A)</p> Signup and view all the answers

What is the main distinction between growth and development?

<p>Growth is a quantitative increase, whereas development refers to an increase in complexity and skills. (B)</p> Signup and view all the answers

During which period does the infantile growth spurt occur?

<p>From 6 months to 2 years (B)</p> Signup and view all the answers

Which of the following accurately describes the cephalo-caudal gradient of growth?

<p>It describes the shift in growth from head to lower extremities as a child matures. (B)</p> Signup and view all the answers

What happens to lymphatic growth after the age of 14 years?

<p>It declines after reaching its maximum size at 11-14 years. (A)</p> Signup and view all the answers

What is true about bone formation via endochondral ossification?

<p>Cartilage cells undergo hypertrophy and hyperplasia before calcification. (C)</p> Signup and view all the answers

At what age does the human brain typically reach 90% of its adult size?

<p>By 6 years (D)</p> Signup and view all the answers

Which statement about the developmental stages of the genital growth is accurate?

<p>Primary and secondary sexual organs remain small until after puberty. (A)</p> Signup and view all the answers

Which of the following best defines 'differential growth'?

<p>Differences in growth rate and timing among various organs. (D)</p> Signup and view all the answers

Flashcards

Growth

Increase in overall body size; measured in terms of increments.

Development

Development of skills and abilities; progress toward maturity.

Maturation

Series of events from fertilization to adulthood; focus on qualitative changes in tissues.

Growth Increment

The amount of growth per unit time. Think of how much a child grows each year.

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Growth Spurt

Sudden and rapid increase in growth rate.

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Differential Growth

Different parts of the body grow at different rates. Think of how a baby's head is much larger proportionally than an adult's.

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Cephalo-caudal Gradient

The axis of increased growth shifts from the head (cephalic) to the lower extremities (caudal). Think of how a baby's head is proportionally larger than an adult's.

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Scammon's Growth Curves

Describes how different tissues and organs grow at different rates. Think of how the brain grows faster than other tissues.

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Spheno-Occipital Synchondrosis

The synchondrosis present between the sphenoid and occipital bones. It plays a crucial role in the anteroposterior growth of the cranial base, influencing the overall facial skeletal pattern.

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Nasomaxillary Complex Growth

The growth of the middle face, which includes structures like the orbits, zygomatic bone, and nasal cavity.

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Vertical Growth of Nasomaxillary Complex

The growth of the nasomaxillary complex in a downward and forward direction. This growth is influenced by various factors, including 1ry displacement at the nasal cartilage, 2ry displacement at synchondrosis, and sutural growth.

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Growth of Face in Width

The growth of the nasomaxillary complex in width, this is achieved through sutural growth at the median palatine raphe and bone deposition on its lateral walls.

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Growth in Antro-posterior (Depth)

The growth of the nasomaxillary complex in depth, facilitated by 1ry displacement at nasal cartilage and tuberosity, 2ry displacement at synchondrosis, and various sutural growths.

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Modes of Growth in Nasomaxillary Complex

The nasomaxillary complex grows by both endochondral ossification (at synchondrosis and nasal cartilage) and intramembranous ossification (at sutures and surface deposition).

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Growth of the Mandible

The mandible, a key facial bone, undergoes significant postnatal growth primarily through two processes: Endochondral ossification at the condyle and symphysis, and intramembranous ossification at the remaining parts.

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Endochondral Growth of Mandible

The growth of the mandible, particularly its condylar and symphysis regions, through endochondral ossification. This process plays a vital role in its growth.

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Drift (Cortical Drift)

Movement of bone in the same direction as its own growth, involving bone resorption and deposition where deposition occurs on one side of the cortical plate and resorption on the other. Think of it like a bone pushing itself forward as it grows.

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Primary Displacement

The movement of the entire bone as a unit, in the opposite direction of its own growth. Imagine a bone being pushed from behind as it grows.

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Secondary Displacement

The movement of the entire bone as a unit, in the same direction as the growth of another adjacent or distant bone. Think of a bone being pulled along by the growth of other bones.

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Remodeling

The change in size and shape of a bone due to the difference in resorption and deposition on its inner and outer surfaces. Think of a bone being sculpted by reshaping.

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Intramembranous Growth

A type of growth occurring at the sutures where bone is added directly on existing bone. Think of adding bricks to a wall.

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Cranial Vault Growth in Width

The growth that occurs in the width of the cranial vault, facilitated by the fusion of the metopic and mid-sagittal sutures. Think of widening a room by adding more wall.

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Cranial Vault Growth in Length

The growth that occurs longitudinally within the cranial vault, primarily through the coronal suture. Think of extending a room by adding more space to the length.

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Metopic Suture

The fusion of the frontal bones by the metopic suture, contributing to the growth in width of the cranial vault.

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Endochondral Ossification

Formation of bone from cartilage, commonly seen in long bones, cartilage model is replaced by bone tissue.

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Synchondroses

Areas of cartilage that persist between bones, responsible for growth of the cranial base, and close at specific ages.

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Intramembranous Ossification

Bone formation directly from mesenchymal cells without a cartilage intermediate, seen in flat bones like the skull.

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Sutures

A fibrous joint between cranial bones that allows for growth and flexibility, gradually ossifies over time.

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Classical Theory (Sicher's)

The classical theory of bone growth that assumed sutures were the primary growth sites, later proven inaccurate.

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Functional Matrix Theory (Moss)

The currently accepted theory that emphasizes the role of surrounding soft tissues in driving cranial bone growth, sutures are secondary.

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Appositional Bone Growth

A type of bone growth that involves adding layers on the surface of existing bone.

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V principle

A growth pattern characterized by bone deposition on the inner side of a V-shaped structure and bone resorption on the outer side, resulting in an overall increase in dimension. This pattern is commonly observed in facial bones like the ramus and palate.

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Ramus growth

A process that contributes to the growth of the mandibular ramus by adding new bone to the posterior border, pushing it backward and vertically.

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Condylar growth

The downward growth of the mandibular condyle, responsible for the overall growth of the mandible in height.

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Alveolar process

The bone that surrounds the teeth and supports their sockets, which helps determine the overall shape of the jaw. It develops as teeth erupt and resorbs when teeth are extracted.

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Coronoid process growth

The bony projection on the posterior part of the mandible, which grows in a posterior direction (though slightly less than the ramus) during development.

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Alveolar process growth (in detail)

The upward and outward growth of the alveolar process, increasing the height and width of the jaw.

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Growth spurts in orthodontic treatment

The period during which orthodontic treatment is most effective and stable, as the jaw bones are actively growing in a specific direction. This period is characterized by growth spurts that occur at different stages of life.

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Growth modification in orthodontics

The ability to manipulate the growth of the jawbones by either restraining their growth or stimulating and redirecting it based on the needs of the patient during their development.

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Study Notes

Definitions

  • Growth: The normal increase in the amount of living organism. It's a quantitative aspect, measured in increments.
  • Development: An increase in skills and function, the ability of a child to perform complex tasks. It's a qualitative aspect, relating to increased tissue complexity, and immeasurable.
  • Growth Increment: The amount of growth per unit of time.
  • Growth Spurt: A sudden increase in growth rate. Three main spurts are observed: infantile, juvenile, and pubertal/adolescent (ages 11-13 in girls, 13-15 in boys).
  • Differential Growth: Variation in growth rate and time for different organs. Examples include the cephalo-caudal gradient (growth starting from the head) and Scammon's growth curves.

Growth Curve Details

  • Cephalo-Caudal Gradient: The axis of increased growth shifts from the head to the lower extremities as a child grows into an adult. This means that the head grows faster than the lower limbs.

Somatic Growth

  • Somatic (General) Growth: Overall growth in body size throughout the growth period. It's rapid in the first months after birth but gradually slows until puberty, then declines again to zero around age 20.

Neural Growth

  • Neural Growth: The central nervous system (CNS) grows rapidly prenatally and early postnatally. The human brain reaches 90% of its adult size by 6 years of age, but functional maturation continues for longer. There is no noticeable pubertal growth spurt in the CNS.

Lymphatic Growth

  • Lymphatic Growth: Lymphatic tissues grow rapidly early in life, reaching a maximum of 200% of their adult size around ages 11-14; growth then declines.

Genital Growth

  • Genital Growth: Primary and secondary sexual organs remain small until puberty, when they reach adult size.

Bone Formation (Osteogenesis)

  • Bone Formation: Bone forms within two connective tissue sites, cartilage and membranous connective tissue. This results in two paths of bone development.

Endochondral Bone Formation

  • Endochondral bone development: Original mesenchymal tissues become cartilage cells first, these hyper- and hyperplasia before their matrix calcifies. Then the cells degenerate, and the tissue gets replaced by osteogenic tissue. This will eventually form the bone.
  • Epiphyseal Plates: Important growth sites in long bones.
  • Synchondroses: Bands of cartilage in the cranial base remain between different bones.
  • Spheno-occipital synchondrosis is an important one that helps postnatal growth, closes between ages 18-20 years old(a few years earlier in girls than in boys)
  • Other cartilages: Nasal cartilage, Condylar cartilage, and Symphyseal cartilage.

Intramembranous Bone Formation

  • Intramembranous bone formation: Undifferentiated mesenchymal cells change into osteoblasts, elaborating osteoid matrix. This matrix gets calcified by osteocytes, forming bone. This process is both positional and additive in nature.

Sutures

  • Sutures: Are periosteal membranes between adjacent bones. Pressure from brain growth causes resorption of the inner surfaces, with deposition on external surfaces. This results in thickening of cranial bones. The thickness is not uniform.

Growth Theories

  • Classical Theory: Inaccurate, focuses on soft tissue proliferation at sutures as the growth center.
  • Functional Matrix Theory: Accurate, links bone separation at sutures to nearby tissue growth (e.g., brain, eyeball, nasal cartilage), not directly to factors within the suture itself.

Growth Movements

  • Growth Movements: Two types are crucial for craniofacial growth: drift and displacement.
  • Drift: Movement in the same direction of bone growth.
  • Displacement: Movement of the whole bone unit, either opposite to growth direction.
  • Primary and secondary forms exist.
  • Bone resorption and deposition: Essential for bone modeling and adaptation to other areas of growth.

Cranial Vault

  • Cranial Vault: The outer part of the skull, formed by multiple bones connected via sutures. Its growth is mainly intramembranous.

Cranial Base

  • Cranial Base: The bottom part of the skull. Grows primarily via cartilaginous (endochondral) methods in synchondroses.

Nasomaxillary Complex

  • Growth of the nasomaxillary complex: Growth occurs in width, depth, and height. Growth in width precedes growth in depth which is followed by growth in height. The face is a smaller version of the cranium in childhood but becomes more proportional in adulthood.

Mandible Growth

  • Mandible Growth: The mandible is the largest facial bone showing significant postnatal growth. Growth occurs both through endochondral (in condyles) and intramembranous methods. Condyle growth occurs in a backward and upward manner; the ramus grows backward, adding bone progressively. The coronoid process also grows; the entire mandible grows in both width, length and height.

Orthodontic Treatment and Growth

  • Timing of orthodontic treatment: Best performed during growth spurts (infantile, juvenile, etc), to maximize effects from treatments.
  • Growth modification: Orthodontic treatment techniques that either restrain or stimulate bone growth in the maxilla and/or mandible, directing it in a particular direction.

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