HLTH1008 Chap.12 Thorax, Lungs and Heart
Thorax, Lungs and Heart
The thorax is a moving cage around the lungs and heart. This chapter classifies the ribs and their joints, compares quiet and forced breathing with the muscles each uses, and describes the diaphragm and intercostals. It contrasts the right and left lungs, defines the bronchopulmonary segment and lists the contents of the hilum, then covers the upper airway, the laryngeal cartilages, alveolar cells and the pleura.
It ends with the mediastinum, venous return to the heart, the arch of the aorta and the thoracic duct. Spotter questions here often ask for a vessel and then its next branch or tributary, so the vessels are learned as sequences. Heart and vessels are learned as sequences of names, because spotters ask for the next branch.
What this chapter covers
- 01
True, false and floating ribs
- 02
Rib joints and chest movements
- 03
Quiet and forced breathing
- 04
Diaphragm and intercostal muscles
- 05
Right and left lungs, lobes and fissures
- 06
Bronchopulmonary segments and the hilum
- 07
Pharynx, larynx and pleura
- 08
Heart, great vessels and thoracic duct
Worked example · free
Telling the right lung from the left
- +1Two lobes and one fissure, the oblique fissure, belong to the left lung.
- +1The tongue-like projection is the lingula of the left superior lobe, which overlies the heart.
- +1The right lung would show three lobes and both oblique and horizontal fissures.
- +1At the hilum expect the primary bronchus, pulmonary artery and pulmonary veins, with bronchial vessels and lymph nodes.
Key terms
- True ribs
- Ribs 1 to 7, whose cartilages reach the sternum.
- Floating ribs
- Ribs 11 and 12, which end freely in front.
- Diaphragm
- The dome-shaped muscle of inspiration, supplied by the phrenic nerve.
- Lingula
- The tongue-like part of the left superior lobe over the heart.
- Type II pneumocyte
- A cuboidal alveolar cell that secretes surfactant.
- Costodiaphragmatic recess
- The lowest part of the pleural cavity below the lung base.
- Coronary sinus
- The vein that returns blood from the heart wall to the right atrium.
- Thoracic duct
- The main lymph vessel, draining into the left venous angle.
- Horizontal fissure
- The fissure that separates the middle lobe from the upper lobe of the right lung.
- Parietal pleura
- The outer pleural layer lining the chest wall, sensitive to pain.
- Bronchopulmonary segment
- The lung unit served by a tertiary bronchus with its own artery and vein.
Thorax, Lungs and Heart FAQ
How does quiet breathing differ from forced breathing?
In quiet breathing the diaphragm and external intercostals produce inspiration and expiration is passive elastic recoil. In forced breathing accessory muscles such as sternocleidomastoid, the scalenes and pectoral muscles help inspiration, and the abdominal muscles and internal intercostals make expiration active.
What is a bronchopulmonary segment?
A part of a lung aerated by a tertiary bronchus with its own artery and vein, separated from its neighbours by connective tissue septa. The respiratory lecture counts ten in each lung and gives surgical resection of a single diseased segment as its clinical importance.
Which vessels return blood to the right atrium?
The superior vena cava, the inferior vena cava and the coronary sinus. The superior vena cava is formed by the two brachiocephalic veins, each made by the internal jugular and subclavian veins, while the pulmonary trunk carries blood out of the right ventricle.
How are the ribs classified?
Ribs 1 to 7 are true ribs whose cartilages reach the sternum, ribs 8 to 10 are false ribs whose cartilages join the cartilage above, and ribs 11 and 12 are floating ribs with free ends. The ninth rib is the most oblique, according to the respiratory lecture.
What does surfactant do and which cells make it?
Surfactant is secreted by type II pneumocytes, the cuboidal secretory cells of the alveolus. Type I pneumocytes, thin squamous cells, form about 90% of the alveolar surface and carry out gas exchange, while dust cells clear inhaled particles.
Exam move
Number the ribs on a skeleton and say true, false or floating for each. Build a two-by-two table of quiet and forced inspiration and expiration with their muscles. Draw both lungs from the side with their lobes and fissures, then list the hilum contents. Finish by tracing blood into the right atrium and out of the aortic arch on a heart model, naming each vessel and its branches aloud.
Add the pleura and the airway: list the parts of the pharynx, the laryngeal cartilages with their cartilage type and the nerve supply of parietal and visceral pleura.
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