04 Thoracic Cavity. Mediastinum. Thymus. Pleura.

cervical pleura

-extends through the superior thoracic aperture into the root of the neck -forms a cup-shaped pleural dome over the apex of the lung

anterior and posterior intercostal, superior phrenic and mediastinal arteries.

Arteries of the parietal layer

bronchial arteries

Arteries of the visceral layer

a deep infection of the neck; penetrating wounds of the chest; esophageal perforations. Air can escape into the connective tissue spaces and ascends beneath the fascia to the root of the neck, producing subcutaneous emphysema.

Causes of Mediastinitis

Median partition - the mediastinum. Lateral partitions - pleural sacs with lungs. The cavity is lined with the endothoracic fascia.

Cavities within the thoracic cavity

the cervical pleura extends up into the neck, covered by the suprapleural membrane; reaches a level 2.5 cm above the medial third of the clavicle;

Cervical pleurae boundaries and features

decreased lung expansion on the side of the effusion, with decreased breath sounds and dullness on percussion over the effusion.

Clinical signs of a pleural effusion

lines the inner surfaces of the thoracic wall, except the front of the vertebral bodies

Costal pleura boundaries

diaphragmatic pleura

Covers superior surface of diaphragm

covers the thoracic surface of the diaphragm

Diaphragmatic pleura area

Each pleural sac has a visceral and a parietal layer, separated by the slitlike pleural cavity containing 5-10ml of fluid The two layers become continuous with one another at the hilum of each lung. To allow for movement of the pulmonary vessels and large bronchi during respiration, the pleural cuff hangs down as a loose fold called the pulmonary ligament.

Features of the Pleurae including layers

in front - the body of the sternum; behind - the lower 8 thoracic vertebrae.

Inferior Mediastinum borders

thymus, heart, pericardium, phrenic nerves, esophagus, vagi nerves, thoracic duct, descending aorta, azygos and hemiazygos veins, sympathetic trunks.

Inferior mediastinum contents

receives an autonomic nerve supply from the pulmonary plexus

Innervation of the visceral pleura (stretch only)

intercostal nerves

Innervations to pain, temperature, touch and pressure of the parietal costal pleura

phrenic nerve and lower 6 intercostal nerves around the periphery

Innervations to pain, temperature, touch and pressure of the parietal diaphragmatic pleura

Phrenic nerve

Innervations to pain, temperature, touch and pressure of the parietal mediastinal pleura

parasternal and internal intercostal lymph nodes near the heads of the ribs

Lymph drainage of the parietal pleura

Lung cancer typically involves the mediastinal lymph nodes, which on enlargement may compress the left recurrent laryngeal nerve, producing paralysis of the left vocal fold. An expanding cyst or tumor can partially occlude the superior vena cava, causing severe congestion of the veins of the upper part of the body. Other pressure effects can be seen on the sympathetic trunks, phrenic nerves, and sometimes the trachea, main bronchi, and esophagus.

Mediastinal tumors or cysts presentations

costal pleura

Parietal pleura attached to ribs.

sternal angle

Ridge between manubrium and body at second rib

costomediastinal recess

Small space of the pleural cavity near heart

costomediastinal recess

Space where the left costal and mediastinal parietal pleura meet and leave a space for the cardiac notch of the left lung (occupied by the lingula during inspiration)

The mediastinum is divided into superior and inferior mediastina. The inferior mediastinum is subdivided into the middle mediastinum; the anterior mediastinum; the posterior mediastinum.

Subdivisions of the Mediastina

in front - the manubrium sterni; behind - upper 4 thoracic vertebrae.

Superior Mediastina Borders

thymus, large arteries and veins, phrenic and vagi nerves, trachea, esophagus, thoracic duct, and sympathetic trunks.

Superior Mediastinum Contents

The approach is performed by dividing the sternum down the middle of the chest. The manubrium should be completely divided and the sternotomy is carried to the level of the 3rd or 4th intercostal space. performed as a part of an access to the heart and great vessels in the neonatal period; for the treatment of thymomas, primary thymic lymphomas and myasthenia gravis. The biopsy may be necessary primary to the removal.

Thymectomy procedure overview

inferior thyroid, internal thoracic, mediastinal arteries.

Thymus blood supply

exceedingly minute branches of the vagi and sympathetic trunk reach the gland; the branches are vasomotor.

Thymus innervation

- lies in the superior and anterior inferior mediastinum within area interpleuralis superior; - in superior mediastinum it is related to the manubrium sterni in front and to the large vessels behind; - in inferior anterior mediastinum it is related to the body of sternum in front and to the pericardium behind; - has 2 lobes of pinkish-gray color, each surrounded by fibrous capsule; - the septae of the capsule separate the lobes of the gland into the lobules.

Thymus locations and relative communicating structures

In the newborn infant, it reaches its largest size relative to the size of the body; it may extend up through the superior mediastinum in front of the great vessels into the root of the neck. The thymus continues to grow until puberty but thereafter undergoes involution.

Thymus relative size at birth and development

The tube is inserted in the 4th or 5th intercostal space along the anterior axillary line. The chest tube allows for continuous, large volume drainage until the underlying pathology can be more formally addressed.

Tube thoracostomy placement and purpose

Parietal layer: anterior and posterior intercostal, superior phrenic and mediastinal veins. Visceral Layer: bronchial veins

Venous drainage of the pleurae

true thymic hyperplasia (idiopathic, associated with the use of steroids, rebound to chemotherapy, radiation, burns or other severe systemic stress); lymphoid hyperplasia (lymphoid follicular hyperplasia or autoimmune thymitis). Both manifest as diffuse symmetric enlargement of the thymus.

What are causes of and what is thymic hyperplasia?

• thymomas are found in 10-15% of patients with myasthenia gravis; • symptoms are sometimes confused with bronchitis because of compression of the recurrent laryngeal nerve; • all thymomas are potentially cancerous; • treatment of thymomas often requires complete thymectomy.

What are some of the general features associated with Thymomas

thoracic outlet and the root of the neck, the diaphragm, the sternum and the vertebral column.

What are the Mediastinum Borders

the thymus, the heart and large blood vessels, the trachea and esophagus, the thoracic duct and lymph nodes, the vagus and phrenic nerves, and the sympathetic trunks.

What are the Mediastinum contents

slitlike spaces between the costal and diaphragmatic parietal pleura.

What are the costodiaphragmatic recesses?

pleural surfaces becoming coated with inflammatory exudate, causing the surfaces to be roughened; - this produces friction; - a pleural rub can be heard with the stethoscope on inspiration and expiration; - the exudate becomes invaded by fibroblasts, which lay down collagen and bind the visceral pleura to the parietal pleura, forming pleural adhesions.

What causes pleurisy?

a collection of pus in the pleural cavity

What is Empyema

- it is a diagnostic procedure for obtaining of specimens of tracheobronchial lymph nodes; - a small incision is made in the midline just above the suprasternal notch; - the superior mediastinum is explored down to the region of the bifurcation of the trachea.

What is Mediastinoscopy and how is it performed

air in the pleural cavity associated with serous fluid.

What is a hydropneumothorax?

abnormal accumulation of serous fluid in the pleural cavity (300 ml is sufficient for its clinical detection).

What is a pleural effusion

air in the pleural cavity

What is a pneumothorax?

air enters the pleural cavity suddenly without its cause being immediately apparent

What is a spontaneous pneumothorax?

air enters on inspiration but cannot exit through the wound; air pressure builds up on the wounded side and pushes the mediastinum toward the opposite side; opposite lung is compressed by the deflected mediastinum

What is a tension pneumothorax?

Thoracocentesis (pleural puncture) is performed in purposes of diagnostics and treatment of pneumothorax and pleural effusions. For evacuation of effusion: the 7th or 8th intercostal space between midaxillary and scapular lines along the upper edge of the lower rib. For evacuation of air: the 2nd or 3rd intercostal space along midclavicular line.

What is a thoracocentesis and how is it performed for effusion? air?

pleural cavity is open to the outside air

What is an open pneumothorax?

lymph in the pleural cavity.

What is chylothorax?

air associated with blood

What is hemopneumothorax?

inflammation of the pleura, secondary to inflammation of the lung (e.g., pneumonia);

What is pleurisy (pleuritis)?

air associated with pus.

What is pyopneumothorax?

Failure of thymic development DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is the most common cause of thymic aplasia in humans. Patients may present with a profound immunodeficiency disease, due to the lack of T cells.

What is thymic aplasia and most common cause?

air was purposely injected into the pleural cavity to collapse and rest the lung (artificial pneumothorax)

What was the old treatment for tuberculosis?

mainly for myasthenia gravis treatment. A 1,5 - inch incision at the bottom of the neck, just above the sternum. No bone is divided and only the skin is cut.

When is transcervical thymectomy typically performed

situated along the anterior margins of the pleura.

Where are the costomediastinal recesses?

The formation of the fluid results from hydrostatic and osmotic pressures. It is secreted from capillaries of the parietal pleura to the pleural cavity, and, than absorbed into the capillaries of the visceral pleura.

Where does pleural fluid originate and where is it absorbed?

azygos vein

a vessel that drains blood from the chest wall and empties into the superior vena cava

anterior mediastinum

between pericardium and sternum contains loose CT, fat, lymphatic vessels, some vasculature

middle mediastinum

contains the heart, roots of great vessels, and pericardium

pulmonary ligament

continuation of the parietal and visceral pleurae that extend inferiorly from the root of the lung between the lung and mediastinum

mediastinal parietal pleura

covers lateral aspect of mediastinum and organs separating the pulmonary cavities and their pleural sacs. It is continuous with the visceral pleura at the hilum of the lung

subclavian artery

either of the arteries that carry blood into the arms

phrenic nerve

innervates the diaphragm

sympathetic trunk

lies to either side of the vertebral column

lymphatic vessels penetrate into the lung parenchyma to join the bronchial lymph vessels

lymph drainage of the visceral pleura

thymus gland

lymphoid organ in the mediastinum that conditions T cells to react to foreign cells and aids in the immune response

covers and forms the lateral boundary of the mediastinum.

mediastinal pleura boundaries

mediastinal pleura

parietal pleural lining covering the mediastinum

posterior mediastinum

posterior to the pericardium and diaphragm Contains the thoracic aorta, esophagus, veins, lymphatic structures, nerves (vagus, phrenic, thoracic sympathetic trunk)

costodiaphragmatic recess

potential space; when it abnormally fills with air or fluid, it compromises lung expansion

thyroid gland

produces hormones that regulate metabolism, body heat, and bone growth

common carotid artery

supplies right side of head and neck

posterior intercostal arteries

supply the vertebrae, spinal cord, intercostal muscles, and deep muscles of the back

visceral pleura

the inner layer of pleura that surrounds each lung

vagus nerve

the tenth cranial nerve that innervates digestive organs, heart and other areas

suprapleural membrane

thickening of endothoracic fascia over cervical pleura

pariental pleura

thin membrane covering the surface of the chest wall, medistinum, and diaphragm that is continuous with the visceral pleura around the lung hilum