Epiphysis, Metaphysis & Epiphyseal Plate: Anatomy & Clinical Importance
In a growing long bone, the epiphysis, metaphysis and epiphyseal plate are important regions involved in the structure and growth of the bone. Understanding their relationships is essential for MBBS anatomy, radiology and orthopaedics.
The epiphyseal plate is particularly important because it is the site of longitudinal growth of a growing long bone. After skeletal growth is completed, it is replaced by the epiphyseal line.
Interactive Long Bone Guide
Click the buttons below to identify the major regions and structures of a growing long bone.
What Is the Epiphysis?
The epiphysis is the expanded end of a long bone. A typical long bone has a proximal epiphysis and a distal epiphysis.
The epiphysis contributes to the formation of joints. At an articular surface, it is covered by articular cartilage, which provides a smooth surface and helps reduce friction during movement.
Structure of the Epiphysis
- The outer region contains a thin layer of compact bone.
- The interior contains predominantly cancellous or trabecular bone.
- In many bones, the spaces between trabeculae contain bone marrow.
- The articular surface is covered by hyaline articular cartilage.
Types of Epiphysis
Epiphyses can be described according to their relationship with the developing bone.
| Type | Description |
|---|---|
| Pressure epiphysis | An epiphysis that participates in forming a joint and is subjected to mechanical forces associated with weight bearing or movement. |
| Traction epiphysis | An apophyseal region associated with tendon or ligament attachment and influenced by traction forces. |
What Is the Metaphysis?
The metaphysis is the region of a long bone between the diaphysis and epiphysis.
In a growing bone, the metaphysis lies immediately adjacent to the epiphyseal plate and is an important region of active bone formation.
Important Features of the Metaphysis
- It connects the shaft with the end of the bone.
- It lies next to the epiphyseal plate in a growing long bone.
- It contains actively remodeling bone near the growth plate.
- It is an important region in several childhood bone disorders.
Epiphysis vs Metaphysis
| Feature | Epiphysis | Metaphysis |
|---|---|---|
| Location | End of a long bone | Between epiphysis and diaphysis |
| Joint relationship | Often contributes to a joint | Does not directly form the articular surface |
| Bone type | Predominantly cancellous internally | Transitioning region with active remodeling |
| Growth plate relationship | Located on the epiphyseal side | Adjacent to the metaphyseal side of the growth plate |
| Growth | Contains secondary ossification center during development | Participates in bone formation adjacent to the growth plate |
What Is the Epiphyseal Plate?
The epiphyseal plate, also called the growth plate, is a plate of hyaline cartilage found in a growing long bone.
It is responsible for longitudinal growth, allowing the bone to increase in length during childhood and adolescence.
The growth plate is located between the epiphysis and metaphysis.
Why Is the Epiphyseal Plate Made of Cartilage?
Cartilage can grow by allowing chondrocytes to proliferate and produce additional extracellular matrix. This provides a continuously expanding cartilaginous region that can subsequently be replaced by bone.
At the metaphyseal side of the growth plate, the cartilage is progressively calcified and replaced by bone.
New cartilage is produced on the epiphyseal side of the growth plate, while cartilage is progressively replaced by bone toward the metaphyseal side.
Zones of the Epiphyseal Plate
From the epiphyseal side toward the metaphyseal side, the growth plate contains characteristic zones.
| Zone | Main Features |
|---|---|
| Resting zone | Contains relatively small chondrocytes. It helps anchor the growth plate to the epiphysis. |
| Proliferative zone | Chondrocytes divide actively and are arranged in columns. |
| Hypertrophic zone | Chondrocytes enlarge and undergo further maturation. |
| Zone of calcification | The cartilage matrix becomes mineralized and the chondrocytes eventually die. |
| Zone of ossification | Bone is deposited on the remaining calcified cartilage framework. |
How Does the Epiphyseal Plate Increase Bone Length?
Longitudinal growth occurs through a coordinated sequence of cartilage proliferation, chondrocyte hypertrophy, cartilage calcification and bone formation.
- Chondrocytes proliferate in the proliferative zone.
- The newly formed chondrocytes enlarge in the hypertrophic zone.
- The cartilage matrix becomes calcified.
- Chondrocytes in the calcified region die.
- Blood vessels and osteogenic cells are present at the metaphyseal side.
- Osteoblasts deposit new bone on the remaining cartilage framework.
As this process continues, the distance between the epiphysis and diaphysis increases, resulting in longitudinal growth of the bone.
Epiphyseal Plate and Epiphyseal Line
The epiphyseal plate is present while the long bone is still growing.
When longitudinal growth is complete, the cartilage of the growth plate is replaced by bone. The remaining bony remnant is called the epiphyseal line.
| Epiphyseal Plate | Epiphyseal Line |
|---|---|
| Present in a growing bone | Present after growth plate closure |
| Made of hyaline cartilage | Bone |
| Allows longitudinal growth | Does not function as an active growth plate |
Diaphysis, Metaphysis and Epiphysis
A typical long bone can therefore be divided into three major longitudinal regions.
| Region | Meaning | Main Characteristics |
|---|---|---|
| Diaphysis | Shaft | Long central portion, composed mainly of compact bone surrounding the medullary cavity. |
| Metaphysis | Transition region | Located between the diaphysis and epiphysis; closely related to the growth plate in growing bones. |
| Epiphysis | End of bone | Expanded end, containing predominantly cancellous bone and contributing to joint formation. |
Blood Supply Around the Growth Plate
The vascular arrangement around the epiphyseal plate changes during skeletal development.
Blood vessels supplying the metaphyseal region and epiphyseal region are important for the metabolically active tissues associated with bone growth.
The growth plate itself is avascular cartilage, while the adjacent metaphyseal and epiphyseal regions have their own vascular supply.
Clinical Importance
1. Growth Plate Injury
Injury to the epiphyseal plate can interfere with normal longitudinal growth. Depending on the site and severity of injury, growth disturbance may affect the length or shape of the developing bone.
2. Fractures in Children
Because the growth plate is present in children and adolescents, fractures that involve this region require particular attention.
3. Rickets
Rickets affects growing bone and can produce abnormalities around the growth plate because of defective mineralization.
4. Metaphyseal Changes
Several pediatric skeletal disorders can produce characteristic metaphyseal abnormalities. The metaphysis is therefore an important region when evaluating pediatric radiographs.
5. Growth Disturbance
Damage to one part of a growth plate may produce asymmetric growth and, in some situations, angular deformity.
Epiphyseal Plate: Important Facts
- The epiphyseal plate is made of hyaline cartilage.
- It is responsible for longitudinal growth of a growing long bone.
- The plate lies between the epiphysis and metaphysis.
- Chondrocytes proliferate and enlarge within the growth plate.
- The cartilage matrix becomes calcified toward the metaphyseal side.
- Osteoblasts deposit bone at the metaphyseal side of the growth plate.
- After growth is complete, the epiphyseal plate becomes the epiphyseal line.
High-Yield MBBS Points
- Epiphysis: expanded end of a long bone.
- Metaphysis: region between epiphysis and diaphysis.
- Epiphyseal plate: cartilaginous growth plate of a growing long bone.
- Epiphyseal line: bony remnant of the growth plate after growth has ceased.
- Longitudinal growth occurs at the epiphyseal plate.
- The growth plate contains resting, proliferative, hypertrophic, calcification and ossification regions.
- The epiphyseal plate is avascular cartilage.
- Growth plate injury can lead to growth disturbance.
Quick Revision
| Term | Remember |
|---|---|
| Epiphysis | End of a long bone |
| Metaphysis | Transition between epiphysis and diaphysis |
| Diaphysis | Shaft of the long bone |
| Epiphyseal plate | Cartilage responsible for longitudinal growth |
| Epiphyseal line | Remnant after growth plate closure |
| Proliferative zone | Chondrocyte division |
| Hypertrophic zone | Chondrocyte enlargement |
| Calcification zone | Cartilage matrix mineralization |
| Ossification zone | New bone deposition |
Summary
The epiphysis forms the expanded end of a long bone, while the metaphysis is the transitional region between the epiphysis and diaphysis.
In a growing bone, the epiphyseal plate lies between the epiphysis and metaphysis. It is composed of hyaline cartilage and is the site of longitudinal bone growth.
The growth plate contains several zones in which chondrocytes proliferate, enlarge and undergo calcification before the cartilage is replaced by bone. When growth is complete, the epiphyseal plate becomes the epiphyseal line.
Image Credits & Licenses
1. Anatomy of a Long Bone:
OpenStax Anatomy and Physiology,
603 Anatomy of a Long Bone.jpg.
Licensed under CC BY 4.0.
Wikimedia Commons
2. Longitudinal Bone Growth:
OpenStax College,
622 Longitudinal Bone Growth.jpg.
Licensed under CC BY 3.0.
Wikimedia Commons
3. Epiphyseal Plate and Epiphyseal Line:
OpenStax College,
623 Epiphyseal Plate-Line.jpg.
Licensed under CC BY 3.0.
Wikimedia Commons
4. Epiphyseal Growth Plate:
Veronika Šromová, Dinara Sobola and Pavel Kaspar,
Epiphyseal growth plate.jpg.
Licensed under CC BY 4.0.
Wikimedia Commons
Medical Disclaimer: The information provided in this article is strictly for educational, study, and exam-preparation purposes. It does not constitute professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider for clinical decisions.