According to Jiusong Health Network, hl is the long axis of fetal humerus and upper carpal bone, which is used to infer the number of weeks of pregnancy in the second and third trimester. Hl4 1mm indicates that the fetal humerus length is 14 1mm, which is equivalent to the size range of 24 weeks of pregnancy.
The humerus is the strongest bone in the upper limb. The upper end forms shoulder joint with scapula, and the lower end forms elbow joint with radius and ulna. The upper end of humerus consists of humeral head, humeral neck, large tubercle and small tubercle. Spherical humeral head and glenoid joint of scapula. The annular shallow groove around the humeral head separates the slightly thinner part between the humeral head and the large and small tubercles, which is called the anatomical neck of humerus. The joints of the head, neck and humerus are large and small nodules, which provide attachment points and levers for some scapular humerus muscles. The greater tubercle is located outside the humerus, and the smaller tubercle is located in front of the humerus. Internodular sulcus (biceps brachii sulcus) separates large and small nodules. The surgical neck of humerus is a slightly thinner part of the distal end of the large and small nodules, which serves as the ridge of the large and small nodules under the two nodules and connects with the intertubercular groove on the side. Surgical neck is a common fracture site of humerus.