The shaft of the humerus, the long bone of the upper arm, extends from the shoulder joint to the elbow. It is bounded by the head of the humerus at the proximal end and the trochlea and capitulum at the distal end. Along its length, the shaft exhibits a smooth, cylindrical shape and a distinct curvature, known as the humeral curvature. The lateral supracondylar ridge, a prominent ridge located just above the distal end, provides an attachment point for muscles involved in elbow flexion.
Structure of the Humeral Shaft
The humerus is the bone of the upper arm. It has a long, cylindrical shaft with a slight anterior curvature. Here’s an exploration of its structure:
Shape and Dimensions
- Length: Approximately 30 cm
- Shape: Cylindrical with an approximately circular cross-section
- Anterior Bowing: Curves anteriorly by about 10°
Surface Features
- Deltoid Tuberosity: A roughened area near the middle of the shaft where the deltoid muscle attaches.
- Radial Groove: A shallow depression that runs obliquely down the posterior aspect of the shaft.
- Nutrient Foramen: A small hole on the anterior surface through which blood vessels enter the bone.
- Medial Supracondylar Ridge: A pronounced ridge along the medial aspect of the shaft, which terminates into the medial epicondyle.
Internal Structure
- Cortical Bone: Dense, compact bone that surrounds the medullary cavity.
- Medullary Cavity: A hollow space within the shaft filled with fatty yellow bone marrow.
Table: Dimensions of the Humeral Shaft
| Measurement | Value |
|---|---|
| Length | ~30 cm |
| Diameter (proximal) | ~2.5 cm |
| Diameter (distal) | ~2 cm |
| Anterior Curvature | ~10° |
Question 1:
Describe the anatomical features of the shaft of the humerus.
Answer:
– The shaft of the humerus is a cylindrical bone that connects the proximal and distal ends of the humerus.
– It is slightly curved anteriorly and laterally.
– The anterior surface of the shaft is smooth, while the posterior surface is marked by a shallow groove called the radial groove.
– The lateral surface of the shaft is marked by the deltoid tuberosity, which is the site of attachment for the deltoid muscle.
– The medial surface of the shaft is marked by the coracobrachialis groove, which is the site of attachment for the coracobrachialis muscle.
Question 2:
What are the dimensions of the shaft of the humerus?
Answer:
– The shaft of the humerus has an average length of 30 cm.
– The diameter of the shaft is approximately 2.5 cm at its widest point.
Question 3:
How does the shaft of the humerus articulate with other bones?
Answer:
– The proximal end of the shaft articulates with the head of the humerus at the glenohumeral joint.
– The distal end of the shaft articulates with the radius and ulna at the elbow joint.
And that’s the scoop on the shaft of the humerus, folks! From its smooth curves to its sturdy resilience, this bone plays a vital role in our daily movements. Thanks for sticking with me on this humerus adventure. If you’re ever curious about other bone-related stuff, be sure to drop by again and let’s dig deeper into the fascinating world of anatomy. Until then, keep those bones strong and happy!