Jon's Limb Anatomy Quiz

The major veins of the pectoral girdle are the axillary and subclavian veins. The axillary vein, formed by the convergence of the brachial and basilic veins, carries blood from the lateral thorax, armpit, and upper limb, continuing as the subclavian vein after passing the first rib. The subclavian vein drains blood from the upper extremities, neck, and upper thorax, merging with the internal jugular vein to form the brachiocephalic vein, thereby playing a crucial role in returning deoxygenated blood to the heart for reoxygenation.

Myoblasts are the correct answer. These are the precursor cells that develop into muscle fibers. During embryonic development, myoblasts proliferate and differentiate to form the skeletal muscle cells (myocytes) that make up muscle tissue. They play a crucial role in muscle growth and repair.

The carpal bones are a group of eight small bones located in the wrist, connecting the hand to the forearm. These bones are arranged in two rows: the proximal row (scaphoid, lunate, triquetrum, and pisiform) and the distal row (trapezium, trapezoid, capitate, and hamate). The carpal bones allow for the complex movements of the wrist and hand, providing both stability and flexibility.

The femoral nerve, originating from the lumbar plexus (L2-L4), innervates the muscles in the anterior compartment of the thigh. These muscles include the quadriceps femoris group (rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius), which are primarily responsible for knee extension. The femoral nerve also provides sensory innervation to the anterior and medial aspects of the thigh.

The rotator cuff refers to the group of muscles and tendons that surround the shoulder joint, providing stability and allowing for movement. The joint that is specifically associated with the rotator cuff is the glenohumeral joint, which is the main joint of the shoulder. The other options mentioned in the question, such as the sternoclavicular, acromioclavicular, and humeralclavicular joints, are not directly related to the rotator cuff.

The innervation of the shoulder is not provided by the dorsal rami of spinal nerves. Instead, the shoulder is primarily innervated by the ventral rami of spinal nerves, specifically from the brachial plexus. The brachial plexus is formed by the ventral rami of the C5 to T1 spinal nerves, and it gives rise to several important nerves that supply the muscles and skin of the shoulder and upper limb, such as the axillary nerve, which innervates the deltoid and teres minor muscles.

Endochondral ossification is the process by which long bones, such as the femur and humerus, develop from a cartilage template. During embryonic development, mesenchymal cells differentiate into chondrocytes, forming a cartilage model of the future bone. This cartilage is gradually replaced by bone as osteoblasts and blood vessels invade the cartilage, depositing bone matrix. This process continues into adolescence as the bones grow in length and strength.

The Apical Ectodermal Ridge (AER) is a critical structure in limb development. It forms at the distal tip of the limb bud and plays a key role in regulating the outgrowth and patterning of the limb by secreting growth factors that influence the underlying mesoderm. The AER ensures proper development of the limb's proximal-distal axis.

All bones of the limb girdle, including the bones of the pectoral (shoulder) and pelvic (hip) girdles, form through the process of endochondral ossification. This process involves the replacement of a cartilage template with bone. During embryonic development, the cartilaginous precursors of these bones are gradually ossified to form mature bone structures. Endochondral ossification is crucial for the formation of long bones and many other bones in the body.

Severing the ulnar nerve and the median nerve dorsally in the arm will inhibit cutaneous sensory on the dorsal surfaces of the fingertips. The ulnar nerve innervates the pinky and half of the ring finger, while the median nerve innervates the thumb, index, middle, and half of the ring finger. Therefore, cutting these nerves would result in the loss of sensation in the dorsal surfaces of the fingertips supplied by these nerves. The radial nerve does not innervate the dorsal surfaces of the fingertips, so cutting it would not have an effect on cutaneous sensory in this area.