Human Anatomy
General Features of Bones and Joints
General osteology and arthrology for MBBS: bone types, long bone parts, blood supply, epiphyses and joint classification, mapped to NMC codes AN2.1 to AN2.6.
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General Features of Bones and Joints
General osteology and arthrology for MBBS: bone types, long bone parts, blood supply, epiphyses and joint classification, mapped to NMC codes AN2.1 to AN2.6.
This chapter lays down the general architecture of bones and joints that every regional dissection later builds on. It covers bone types and growth, the blood supply of bone, and the classification and structure of joints along with the principles that govern their nerve supply.
High-yield: General Features of Bones and Joints
- Bones are classified by shape into long, short, flat, irregular, sesamoid and pneumatic types.
- A typical long bone has a diaphysis, two epiphyses, the intervening metaphysis and an epiphyseal growth plate.
- The epiphyseal plate is the site of longitudinal growth and closes when growth is complete.
- Compact bone forms the dense outer shell, while spongy bone with marrow spaces lies within.
- The nutrient artery is the main blood supply and usually enters directed away from the growing end of the bone.
- A pressure epiphysis takes part in weight transmission, while a traction epiphysis forms at the pull of a tendon.
- The patella is the largest sesamoid bone and develops within the quadriceps tendon.
- Fibrous joints are held by fibrous tissue and include sutures, syndesmoses and gomphoses.
- Cartilaginous joints are primary, made of hyaline cartilage, or secondary, made of fibrocartilage as at the pubic symphysis.
- Synovial joints have an articular cavity, articular cartilage, a capsule and a synovial membrane.
- Synovial joints are subclassified as hinge, pivot, saddle, condylar, ball-and-socket and plane types.
- Hilton's law states that a nerve crossing a joint supplies the muscles that move it, the joint itself and the overlying skin.
- Articular cartilage is avascular and receives nutrition from the synovial fluid.
- Ossification is intramembranous in flat bones and endochondral in long bones.
Classification of joints
- **Fibrous joints:** United by fibrous tissue; sutures of the skull, syndesmoses and gomphoses. Little or no movement.
- **Primary cartilaginous:** Bones joined by hyaline cartilage, as at an epiphyseal plate; temporary and unite in growth.
- **Secondary cartilaginous:** Joined by fibrocartilage in the median plane, as at the pubic symphysis and intervertebral discs.
- **Synovial joints:** Have a fluid-filled cavity, articular cartilage, capsule and synovial membrane; freely movable.
NMC competencies in this chapter
- **AN2.1:** Classification of bones with examples
- **AN2.2:** Parts of a young long bone and their applied anatomy
- **AN2.3:** Blood supply of a long bone
- **AN2.4:** Types of epiphyses and their significance
- **AN2.5:** Classification of joints with examples
- **AN2.6:** Structure and nerve supply of a synovial joint
Frequently Asked Questions
What is the epiphyseal plate and why does it matter?
It is the plate of cartilage between the epiphysis and metaphysis where a long bone grows in length. It closes when growth stops, and injury to it in children can disturb growth.
How are synovial joints structured?
A synovial joint has a fluid-filled cavity, articular cartilage over the bone ends, a fibrous capsule lined by synovial membrane, and often reinforcing ligaments. This design allows free movement.
What does Hilton's law state?
Hilton's law says the nerve supplying the muscles that move a joint also supplies the joint capsule and the skin over the joint. It explains referred pain patterns around joints.
How does bone get its blood supply?
A long bone is supplied mainly by a nutrient artery that enters the shaft, along with periosteal, metaphyseal and epiphyseal vessels. The nutrient artery usually points away from the growing end.
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