Chest Anatomy and Physiology

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Chest: Radiological Anatomy and Physiology Dr. Tim Joseph Northern Health

Why does it matter?:

Why does it matter? Acquisition factors: Contrast vs. Non-Contrast Techniques Inspiration / Expiration / Prone / Supine ECG Gating Filming Factors To HRCT or not to HRCT

Why Does it Matter?:

Why Does it Matter? Oxygen is good for us.

Physiology:

Physiology The major muscle of respiration creating negative pressure within the thoracic cavity it the diaphragm (supplied by the phrenic nerves (C3-5)). Further inspiratory effort is provided by the external intercostal muscles and, during exercise and distress, the accessory muscles of respiration (sternocleidomastoid and scalene muscles).

Physiology - Respiration:

Physiology - Respiration Respiration is controlled centrally and peripherally. The brainstem contains a respiratory centre initiated automatic respiratory drive, influenced by higher (cortical) control. Central chemoreceptors in the medulla respond to CSF hydrogen ion concentration (itself determined by CO2). Peripheral receptors in the carotid bodies and aorta.

Physiology - Respiration:

Physiology - Respiration Varying degrees of excursion of the chest wall, and the rate at which it occurs allows air to be transported to the alveolus for the purpose of gas exchange.

Physiology – Gas Exchange:

Physiology – Gas Exchange

Embryology...(sleep now):

Embryology...(sleep now) At 4 weeks gestation the respiratory diverticulum (lung bud) appears at the ventral wall of the primitive foregut. The epithelium arises from the endodermal layer. The cartilaginous, muscular and connective tissue components arise from the splanchnic mesoderm. The lung bud arises in communication with the foregut. Later, two longitudinal ridges separate the two structures. These ridges from the tracheoesophageal septum.

ZZZZZZzzzzzzz.......:

ZZZZZZzzzzzzz....... The lung buds each divide in turn. On the right, three divisions occur and on the left, two divisions occur. These early divisions reflect the subsequent development of three eventual lobes on the right and two on the left. Note that the dividing bronchi invaginate the pleura. This creates a visceral and parietal layer of pleura. The dividing secondary bronchi divide dichotomously forming tertiary (or segmental ) bronchi. 10 are formed on the left and 8 are formed on the left. A further 24 (or so) divisions form in the following prenatal and postnatal months. (About 6 form in the postnatal period).

Hmmm...what? Oh....zzzzz.:

Hmmm...what? Oh....zzzzz. After multiple divisions the, now tiny, airways are known as respiratory bronchioles . These become useful when some of the cuboidal cells change into thin, flat cells. The cells lie next to many small blood vessels and lymph capillaries. The surrounding spaces are now termed terminal alveoli or primitive alveoli. At about 7 months of age there are enough of the structures to provide adequate gas exchange.

Anatomical Considerations:

Anatomical Considerations

Anatomical Considerations:

Anatomical Considerations Interstitium Pleura Airspaces Other...

Secondary Pulmonary Nodule:

Secondary Pulmonary Nodule

Secondary Pulmonary Nodule:

Secondary Pulmonary Nodule The smallest unit of the lung marginated by interlobular septa. 10-25 mm in diameter. Polyhedral in shape. Central bronchovascular bundle: The terminal bronchiole terminates at the secondary pulmonary lobule. Respiratory bronchioles branch at 1-3 mm. Pulmonary artery divisions are paired with the bronchioles. Pulmonary veins run in the periphery of the lobule. Lymphatics run both centrally , down to the terminal bronchiole level, and peripherally , along with the pulmonary veins, interlobular septa and pleura.

Secondary Pulmonary Lobule :

Secondary Pulmonary Lobule

Secondary Pulmonary Lobule:

Secondary Pulmonary Lobule Acinus: All structures distal to the terminal bronchiole. Respiratory bronchioles Alveolar ducts Alveolar sacs 5-15 acini in one secondary pulmonary lobule. Average diameter 8 mm. Not radiologically visible!

Acinus:

Acinus Surfactant- A phospholipid molecule which coats the acinus and increases compliance while preventing alveolar collapse.

Secondary Pulmonary Lobule:

Secondary Pulmonary Lobule

The Bronchial Tree:

The Bronchial Tree Conducting tubes for the transport of air to the alveoli for gas exchange. 300,000 branching airways with approximately 23 divisions. Range in size from 2-2.5 cm to < 2mm (trachea) to (small airways). Over diminishing sizes, termed trachea, bronchi, bronchiole (respiratory and terminal).

The Bronchial Tree :

The Bronchial Tree Fibrocartilgenous structures. Upper airways are lined with respiratory epithelium. Respiratory epithelium is cilated, produces mucous and provides integrity. Cartilage is not a feature of the bronchiolar divisions.

Segmental Lung Anatomy:

Segmental Lung Anatomy

Pleura:

Pleura The lungs are invested by a smooth, serous membrane. The pleura are double layered because of the outgrowth of the lung buds. As such, two layers are described: Visceral pleura Parietal pleura

Lobar Anatomy:

Lobar Anatomy

Pleura:

Pleura

Pleura:

Pleura

Pleura:

Pleura

Pleura:

Pleura

Pleura:

Pleura The pleura provide a smooth surface over which the lungs can expand. Physiologically contain a small (few ml) of fluid. The fluid also aids in creating negative pressure to help the lungs expand (and also to avoid collapse).

Mediastinum:

Mediastinum

Mediastinum:

Mediastinum Anterior Mediastinum Lymph nodes Residual Thymus +/- Thyroid

Mediastinum:

Mediastinum Middle Mediastinum Heart Great Vessels: Aorta (ascending and arch), SVC,IVC,brachio-cephalic. Trachea and main bronchi. Phrenic, vagus snd lrft recurrent laryngeal nerves. Lymph nodes.

Mediastinum:

Mediastinum Posterior Mediastinum Oesophagus Descending Aorta Azygous and hemi-azygous veins. Thoracic duct. Vagus and splanchnic n. Lymph nodes. Fat and paravertebral soft tissue.

Mediastinum:

Mediastinum Bounded laterally by the lungs.

Blood Supply:

Blood Supply The blood supply to the the lungs is dual: The pulmonary arteries (from the pulmonary trunk of the right ventricle) supply the alveoli with de-oxygenated blood. The bronchial arteries supply the pulmonary interstitium (aortic in origin).

Venous Drainage:

Venous Drainage Pulmonary veins drain to the left atrium, formed from the capillaries and venules.

The Chest Wall and Diaphragm:

The Chest Wall and Diaphragm

The Chest Wall and Diaphragm:

The Chest Wall and Diaphragm The diaphragm is parachute like in shape. It is the major muscle of respiration. It separates the thoracic and abdominal cavities. A number of important stuctures pass through various apertures.

Diaphragm:

Diaphragm IVC, Oesophageal and Aortic apertures.

Thoracic Wall and Revision:

Thoracic Wall and Revision

Thoracic Wall and Revision:

Thoracic Wall and Revision

Thoracic Wall and Revision:

Thoracic Wall and Revision

Thoracic Wall and Revision:

Thoracic Wall and Revision

Thoracic Wall and Revision:

Thoracic Wall and Revision

Thoracic Wall and Revision:

Thoracic Wall and Revision

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