Lungs, Pleura And Diaphragm Flashcards
Pleurae
2 layers of membrane (the pleurae) cover the lungs and structures passing into and out of the lungs- pulmonary vessels and main bronchi
2 layers of pleura
Parietal pleura lines inside of thorax
• Visceral pleura covers surface of lungs and extends into the fissures
• Very thin pleural cavity lies between 2 layers
• layers are continuous with each other
Parts of parietal pleura
-cervical pleura covers apex of lung
-costal pleura lies adjacent to the ribs
-mediastinal pleura lies adjacent to heart
-diaphragmatic pleura lies adjacent to diaphragm
Costodiaphragmatic recess
gutter around the periphery of the diaphragm, where the costal pleura becomes continuous with the diaphragmatic pleura
Mediastinum
divides thoracic cavity in 2 (extends from vertebral bodies behind to sternum)- heart, great blood vessels, oesophagus and trachea contained within thickness
Which nerves innervate the parietal pleura
innervated by intercostal nerves that innervate the overlying skin of the chest wall- somatic sensory fibres carry sensation to consciousness so injury is very painful
Which nerves innervate the visceral pleura
innervated by autonomic sensory nerves (visceral afferents)
Lobes of lungs
right lung has 3 lobes (superior, middle + inferior), left lung has 2 lobes (superior + inferior) to accommodate space of heart- lingula
Fissures
lobes separated by fissures- both lungs have an oblique fissure and right lung has a horizontal fissure
Surface and borders of lungs
• Costal surface - adjacent to the ribs.
• Mediastinal surface - adjacent to the heart, marked by the hilum
• Diaphragmatic surface - the inferior surface of the lung.
• Anterior border - sharp and tapered.
• Posterior border – thick and rounded.
• Inferior border - sharp and tapered.
Alveoli
Site of gas exchange
Around 300 million per lung
Each lung served by…
one pulmonary artery, 2 pulmonary veins, one main bronchus
Hilum
the region on the mediastinal surface of the lung where the pulmonary artery, pulmonary veins and main bronchus enter and exit the lung
• At the hilum of the right lung, the pulmonary artery lies anterior to the main bronchus.
• At the hilum of the left lung, the pulmonary artery lies superior to the main bronchus.
• At both the right and left hila, the two pulmonary veins are usually the most anterior and inferior vessels.
Pleura enclosed root
root of each lung lies between the heart and the lung and comprises the pulmonary artery, pulmonary vein and main bronchus
Bronchial tree
Each main (primary) bronchus divides into lobar (secondary) bronchi; three in the right lung and two in the left lung (i.e. one lobar bronchus for each lobe).
• Each lobar bronchus divides to give rise to segmental (tertiary) bronchi.
Bronchi then divide in to bronchioles and then alveoli
How many segmental bronchi in each lung
Approx. 10 so 10 bronchopulmonary segments
Walls of trachea
walls of the trachea and bronchi contain smooth muscle and cartilage, but the walls of bronchioles only contain smooth muscle. Contraction and relaxation of the smooth muscle is under autonomic control.
Trachea
its upper end is continuous with the cricoid cartilage. The corrugated appearance of the trachea comes from the series of c-shaped cartilages that strengthen its wall and keep it open. In between them, the tracheal wall is soft, so that the trachea is highly flexible.
Right and left bronchus
Right main bronchus is shorter, wider and descends more vertically than left main bronchus- foreign body more likely to enter
Carina
trachea bifurcates (at level of T4)into left and right main bronchi at level of sternal angle- marked by a ridge of cartilage called the carina
Which arteries supply the lungs
bronchial arteries from descending aorta supply the lungs
Which veins supply the lungs
Bronchial veins return blood to the azygos system of veins
Which nerves innervate the lungs
Parasympathetic autonomic fibres stimulate construction of the bronchial smooth muscle (bronchoconstriction) and secretion of glands of bronchial tree
• Sympathetic autonomic fibres stimulate relaxation of bronchial smooth muscle (bronchodilation) and inhibit secretion from glands
• Visceral afferents relay sensory information from lungs and visceral pleura to CNS
Which ducts does lymph drain into in lung
Lymph from lungs drains into venous system via thoracic duct or right lymphatic duct
The lymphatic vessels of the lung arise from two lymphatic plexuses:
Superficial (subpleural) – drains the lung parenchyma.
Deep – drains the structures of the lung root.
Both these plexuses empty into the trachebronchial nodes – located around the bifurcation of the trachea and the main bronchi. From here, lymph passes into the right and left bronchomediastinal trunks.
Diaphragm
Broad, thin, domed sheet of skeletal muscle
• Separates thoracic and abdominal cavities
• Superior surface adjacent to parietal pleura
Central tendon
Central part of diaphragm is fibrous- fuse with fibrous pericardium
Apertures
openings in diaphragm allow passage of structures between thorax and abdomen eg aorta
What is the diaphragm attached to
Attached to xiphoid process, costal margin (and to tips of 11th and 12th ribs) and lumbar vertebrae
Which nerves innervate the diaphragm
• Phrenic somatic nerves innervate diaphragm- formed in neck by fibres from C3,C4 and C5 spinal nerves (contain motor and sensory fibres)
Inspiration
• The diaphragm and external intercostal muscles contract, increasing the intrathoracic volume (the external intercostals pull the ribs superiorly and laterally, and the ribs pull the sternum superiorly and anteriorly, increasing the AP and lateral dimensions of the thoracic cavity).
• The lungs expand (increase in volume) with the thoracic wall (due to surface tension).
• The pressure in the lungs decreases below atmospheric pressure and air is drawn into the lungs.
• Action of scalene muscles raises the first and second ribs and the manubrium in deep inspiration