Explains thoracic wall, Cheat Sheet of Human Genetics

Download Explains thoracic wall and more Cheat Sheet Human Genetics in PDF only on Docsity!

THORACIC WALL

- THORACIC

VERTEBRAE, RIBS,

STERNUM AND JOINTS

BETWEEN THEM

Thoracic cage Made up of sternum, 12 pairs of ribs and 12 thoracic vertebrae Sternum – manubrium, body and xiphoid process 12 pairs of ribs:

• (^) 1-7 are true ribs (vertebrosternal ribs)
• (^) 8-10 are false ribs (vertebrochondral ribs)
• (^) 11-12 are floating ribs (vertebral ribs) Functions of thoracic cage
• (^) Protects the upper abdominal viscera, heart, lungs, thymus, nerves and blood vessels
• (^) Serves for the attachment of muscles involved in respiration
• (^) Movements of pectoral girdle and upper limb

Thoracic inlet:

Clinical correlation: The thoracic inlet is called by clinicians as thoracic outlet since important arteries and T1 spinal nerve emerge from the thorax through this aperture and enter the neck and upper limbs. If these structures are compressed it will result in thoracic outlet syndrome (same as thoracic inlet syndrome) Thoracic inlet syndrome: The subclavian artery and lower trunk of the brachial plexus arch over the first rib, hence they may be stretched and pushed up by the presence of a congenitally hypertrophied scalenus anterior muscle or a cervical rib (when present). This leads to thoracic inlet syndrome ( also called scalenus anterior syndrome or cervical rib syndrome ). It presents the following clinical features:

• Numbness, tingling, and pain along the medial side of forearm and hand, and wasting of small muscles of the hand due to the involvement of lower trunk of brachial plexus (T1).
• (^) There may be ischemic symptoms in the upper limb such as pallor and coldness of the upper limb, and weak radial pulse due to compression of the subclavian artery.

Sternum or breastbone (derived from Greek, where it means chest)

Features of interest at the sternal angle:  (^) Sternal angle can be felt as a transverse ridge on sternum around 5cm below the suprasternal notch  (^) Second costal cartilage articulates, on either side with the sternum at this level, hence this level is used for counting the ribs below  (^) Sternal angle lies at the level of intervertebral disc between T4 and T  (^) Horizontal plane passing through this level separates superior mediastinum from inferior mediastinum  (^) Ascending aorta ends, arch aorta begins and ends and descending aorta begins at this level  (^) Trachea bifurcates into right and left principle bronchi at this level  (^) Pulmonary trunk divides into right and left pulmonary arteries at this level  (^) Azygos vein arches over the root of right lung to open into the superior vena cava

Ossification of sternum:

Clinical correlations Sternal puncture: Manubrium sterni is the preferred site for bone marrow aspiration ( for hematological examination ) because it is subcutaneous and readily accessible. A thick needle is inserted into the upper part of manubrium to avoid injury to arch of aorta, which lies behind the lower part. Sternal puncture is not advisable in children because in them the sternum is very thin. Mid-sternotomy: To gain access for surgical operations on heart and great blood vessels the sternum is often divided in the median plane.

Sternal foramen or cleft sternum: failure of sternebrae to fuse in the midline, as a

result defect occurs in the body of the sternum in the form of sternal foramen or cleft

sternum. The cleft sternum is often associated with ectopia cordis.

Cardiopulmonary Resuscitation (CPR) - chest compressions and rescue breaths to victims of a cardiac arrest.

• (^) Chest compressions are delivered in the center of the chest over the sternum.
• (^) CPR works by keeping oxygenated blood flowing around the body in order to keep vital organs (such as the heart and brain) alive.
• (^) Chest compressions are a vital part of CPR, the rescuer should provide 100 – 120 chest compressions a minute at a depth of 5 – 6cm.
• (^) It is common for ribs to be broken during CPR. Prevalence of rib fractures in adult victims who received CPR was over 80%. In rare cases the sternum may also gets fractured (age related).

Atypical thoracic vertebrae

Joints of the vertebral column: All the joints from C2 – S1 articulate by:

• (^) Secondary cartilaginous joint (symphysis) – between adjacent bodies of vertebrae
• (^) Synovial joints – between their articular processes
• (^) Fibrous joints – between their laminae, transverse process and spinous process
• (^) Interlaminar or Zygapophysial joints – plane variety of synovial joint Nerve supply – branch from dorsal rami of spinal nerve at the level of the joint

Ligaments of the vertebral column …..

Ribs (costae):

• (^) Flat, ribbon-like, elastic bony arches which extend from thoracic vertebrae posteriorly to the lateral border of the sternum anteriorly Normally 12 pairs of ribs Classification of ribs:

1. According to features Typical ribs : 3rd^ – 9th; typical ribs have same general features ( CAT : C urved, A ngulated and T wisted) Atypical ribs: 1 st , 2 nd , 10 th , 11 th , 12 th ; have special features, therefore differ from typical ribs and other atypical ribs 2. According to articulation with the sternum True ribs : 1st^ – 7th^ ribs; articulate with the sternum anteriorly False ribs : 8 th - 12 th ribs; do not articulate directly with the sternum anteriorly 3. According to articulation Vertebrosternal ribs : 1 st - 7 th ribs Vertebrochondral ribs : 8th^ – 10th^ ribs Vertebral ribs or floating ribs : 11 th & 12 th ribs