12.3
Üst Ekstremitedeki Kemikler: Radius
Radius, humerusun capitulumu ve ulnanın radius çentikleşmesi ile dirsek eklemi oluşturarak insan antebrachium veya ön kolunu oluşturan iki kemiğin dah…
Yarıçap, ulnaya paralel uzanan ve onu radyal çentikte proksimal, ulnar çentik üzerinden distal olarak birleştiren lateral önkol kemiğidir.
Çivi şeklinde bir kafaya ve radyal stiloid işlem adı verilen sivri bir çıkıntıyla biten kıvrımlı bir şafta sahiptir.
Proksimal uçta, baş humerus kapitulum ve ulna ile birleşerek dirsek eklemini oluşturur. Radyal başlığın dönüşü, avuç içi yukarı veya aşağı çevirirken önkol hareketini sağlar. Kolun gerilmesi sırasında, baş humerusun radyal fossasına doğru hareket eder.
Radyal başın hemen altında, dar bir boyun, kolun pazı kaslarını sabitleyen kaba radyal tüberoziteye kadar uzanır.
Distal uçta, radyal stiloid süreç, radyokarpal veya bilek eklemini oluşturan bilek kemikleri ile birleşir.
Stiloid işlem, bileğin yanal rotasyonunu sınırlamak için kısa ve uzun bir radiolunat ligament yoluyla bilek eklemi hareketini stabilize eder.
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Q1: Where does the radius articulate with other bones at the elbow?
At the proximal end, the radius articulates with the capitulum of the humerus and the radial notch of the ulna to form the elbow joint. The nail-shaped radial head joins these structures, enabling the forearm to flex and rotate. This articulation allows the radial head to move into the radial fossa of the humerus during arm flexion.
Q2: What is the radial tuberosity and what attaches to it?
The radial tuberosity is a rough, oval-shaped prominence located just below the radial neck. The biceps brachii muscle attaches to this tuberosity, anchoring the bicep muscles of the arm. This attachment site is crucial for arm flexion and supination movements.
Q3: How does the radius connect to the wrist bones?
At the distal end, the radius articulates with the carpal wrist bones, specifically the scaphoid and lunate, forming the radiocarpal joint. The radial styloid process, a pointed projection at the distal end, joins with these wrist bones. Ligaments including the radiolunate ligament stabilize this joint and limit lateral wrist rotation.
Q4: What role does the interosseous membrane play in the forearm?
The interosseous membrane connects the radius to the ulna along the entire length of the shaft, providing structural support and stability between the two forearm bones. It also serves as an attachment site for multiple muscles including the pronator teres, pronator quadratus, and supinator, which facilitate pronation, supination, and other forearm movements.
Q5: How does the radius enable pronation and supination of the forearm?
During pronation, the radial head rotates and crosses over the ulna, causing the palm to face posteriorly. Supination reverses this movement, allowing the palm to face anteriorly. An annular ligament surrounding the radial head stabilizes it to the ulnar notch, enabling smooth rotation while maintaining joint integrity.
Q6: What is the relationship between the radius and ulna at the distal end?
At the distal end, the radius articulates with the ulna via the ulnar notch, forming the distal radioulnar joint. This joint allows the radius to rotate around the ulna during pronation and supination. The connection maintains forearm stability while permitting the rotational movements necessary for hand positioning.
Q7: How do structural changes in the radius occur as part of changes in the appendicular skeleton with age?
The radius, as part of the appendicular skeleton, undergoes structural changes throughout life. Understanding how bones like the radius change with age helps explain age-related changes in forearm strength, mobility, and joint stability. These changes affect pronation, supination, and overall upper limb function in aging individuals.