Question

1. discuss the relationship between the three cords of the branchial plexus and their position in relation to the axillary artery.

2.Describe the abdominal muscle involved in sitting up from a supine position.

3. describe the articulation points between the parts of the ribs and their corresponding point on the thoracic vertebrae.

Answer 1

1.The brachial plexus is divided into five roots, three trunks, six divisions (three anterior and three posterior), three cords, and five branches. Each trunk divides into two branches within the posterior triangle of the neck. One division moves anteriorly and the other posteriorly, these three anterior and three posterior nerve fibres. These divisions leave the posterior triangle and pass into the axilla. They recombine into the cords of the brachial plexus.

The cords are named by their position with respect to the axillary artery.

The lateral cord is formed by: The anterior division of the superior trunk and The anterior division of the middle trunk  (C5-C7)

The posterior cord is formed by:The posterior division of the superior trunk and The posterior division of the middle trunk (C5-C8, T1)

The medial cord is formed by: The anterior division of the inferior trunk. (C8, T1)

2. Situps are classic abdominal exercises done by lying on your back and lifting your torso, the main muscles involved in this type of activity are  rectus abdominis, transverse abdominis, and internal and external obliques, in addition it also involves iliopsoas and rectus femoris muscles.

The rectus abdominis is the wall of abdominal muscle that connects to the lower rib cage and to the hips, this muscle creates the six-pack effect.

Transverse abdominis  is a muscle layer of the anterior and lateral abdominal wall which is deep to the internal oblique muscle.

Obliques attach to the rib cage and the pelvis, but to either side of the rectus abdominis. They are the primary muscles for twisting the body back and forth and for tilting the rib cage from side to side.

The iliopsoas attaches to the lower spine and high up on the hips and to the upper front of the femur. Their function is to bend the body at the hips.

3. The rib cage or thoracic cage  consists of the 12 pairs of ribs with their costal cartilages and the sternum.The majority of the ribs have an anterior and posterior articulation. All of the twelve ribs articulate posteriorly with the vertebrae of the spine, each rib forming two joints namely Costotransverse joint and Costovertebral joint

But however anteriorly their articulation vary,

Ribs 1-7 attach independently to the sternum.

Ribs 8 – 10 attach to the costal cartilages superior to them.

Ribs 11 and 12 do not have an anterior attachment, hence known as floating rib