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
Expiration
• The diaphragm and external intercostal muscles relax, and the internal intercostals contract, decreasing the intrathoracic volume (the internal intercostals pull the ribs inferiorly, and the ribs pull the sternum inferiorly and posteriorly, decreasing the AP and lateral dimensions of the thoracic cavity).
• The lungs recoil (decrease in volume).
• The pressure in the lungs increases above atmospheric pressure and air is expelled from the lungs.
• Anterior abdominal wall muscles contribute to forced expiration eg coughing or sneezing
Difference between normal, vigorous and forced breathing
• In normal, quiet breathing- inspiration active and mainly driven by diaphragm but expiration is passive
• In vigorous breathing- active expiration uses internal intercostal muscles
• in forced breathing eg exacerbation in asthma or COPD- accessory muscles of breathing (sternocleidomastoid, pectoralis major and minor, serratus anterior) contribute to movement of ribs and aid ventilation. Anterior abdominal wall muscles contribute to forced expiration
3 planes of movement of thoracic cavity during breathing
- Vertically - due to the contraction and relaxation of the diaphragm.
- Laterally - due to contraction of the intercostal muscles which move the ribs.
- Antero-posteriorly (AP) – due to movement of the sternum secondary to movement of the ribs.
Role of pleura fluid in breathing
pleural fluid creates surface tension which keeps the lung and thoracic wall together, so when thoracic cavity changes volume, lung change volume with it
• Surface tension between the two pleural membranes keeps them in contact with each other and prevents the lung from ‘collapsing’ away from the thoracic wall.
• If the surface tension is ‘broken’ (e.g. by a penetrating injury of the chest that punctures the parietal pleura and introduces air into the pleural cavity - pneumothorax) then ventilation may become dysfunctional.
Crura
The parts of the diaphragm that arise from the vertebrae are tendinous in structure, and are known as the right and left crura:
Right crus – Arises from L1-L3 and their intervertebral discs. Some fibres from the right crus surround the oesophageal opening, acting as a physiological sphincter to prevent reflux of gastric contents into the oesophagus.
Left crus – Arises from L1-L2 and their intervertebral discs.
Pathways through the diaphragm
Caval Hiatus (T8)
Inferior vena cava
Terminal branches of right phrenic nerve
Oesophageal Hiatus (T10)
Oesophagus
Right and left vagus nerves
Oesophageal branches of left gastric artery/vein
Aortic Hiatus (T12)
Aorta
Thoracic duct
Azygous vein
How many intercostal muscle pairs are there
11
Epithelium of bronchial tree
The trachea and bronchi are lined by ciliated pseudostratified columnar epithelium, interspersed by goblet cells, which produce mucus. The combination of sweeping movements by the cilia and mucus from the goblet cells forms the functional mucociliary escalator. This acts to trap inhaled particles and pathogens, moving them up out of the airways to be swallowed and destroyed.
Neurovascular supply of trachea
The trachea receives sensory innervation from the recurrent laryngeal nerve.
Arterial supply comes from the tracheal branches of the inferior thyroid artery, while venous drainage is via the brachiocephalic, azygos and accessory hemiazygos veins.
Bronchioles- club cells
produce a surfactant lipoprotein which is instrumental in preventing the walls of the small airways sticking together during expiration.
Hierarchy of bronchioles
Conducting bronchioles- transport air but lack glands and are not involved in gas exchange
Terminal bronchioles
Respiratory bronchioles- distinguishable by the presence of alveoli extending from their lumens.
Trachea is a continuation of the…
Larynx
Nerves of thorax
•Left and right phrenic nerves (C3,4 and 5) – innervate the diaphragm
•Left and right vagus nerves – complex
•Vagus is a cranial nerve (leaves the brainstem)
•Parasympathetic fibres – supply the thoracic viscera
•Somatic motor fibres – supply muscles of the pharynx and larynx
•Somatic sensory fibres – supply the larynx
•Left and right sympathetic trunks / chains – complex
•Sympathetic innervation to thoracic and abdominal viscera, smooth muscle of blood vessels and glands
Bronchoconstriction
Parasympathetic
Auscultation
Listen to lower lobe on back
Middle lobe listen to anteriorly
What organ sits under right side of diaphragm
Liver
Sternocleidomastoid
- connected to neck and lifts sternum
Pectoralis major
connects humerus to sternum. Involved in internal rotation, Adduction and flexion of arm
Serratus anterior
involved in protraction. Only muscle supplied by long thoracic nerve
Between which two layers of tissue is the intercostal neurovascular bundle located?
internal and innermost intercostal muscle layers.
The internal thoracic artery branches from which larger artery?
Subclavian
Which nerve(s) supplies the parietal pleura of the lateral chest wall
Intercostal nerves
The inferior border of the lung is located at the level of which rib posteriorly?
10th
The inferior border of the lungs anteriorly is at the level of the
6th rib
The inferior border of the lungs laterally is at the level of the
8th rib
The inferior border of the parietal pleura (which is two rib-levels lower than that of the lungs all the way around) is at the level of the
12th rib posteriorly
Which spinal nerves contribute to the phrenic nerve?
C3-C5
which muscles are used in deep inspiration to move clavicle and sternum
scalene muscles
Shape of cervical (3-7) vertebrae
Small
Wide side to side
Spinous process= Short, bifid, projects directly posteriorly
Triangular vertebral foramen
Transverse processes contain foramina
Movements allowed by cervical vertebra
Flexion
Extension
Lateral flexion
Rotation
Superior and inferior articulating processes of cervical vertebra
Superior facets directed superoposteriorly
Inferior facets directed inferoanteriorly
Shape of thoracic vertebrae
Larger than cervical
Heart-shaped
Bears 2 costal facets
Spinous process - long, sharp , projects inferiorly
Circular vertebral foramen
Transverse process bear facets for ribs (except T11 and T12)
Movements allowed by thoracic vertebra
Rotation
Lateral flexion (limited by ribs)
Flexion and extension prevented
Superior and inferior articulating processes of thoracic vertebra
Superior facets directed posteriorly
Inferior facets directed anteriorly
Shape of lumbar vertebra
Massive
Kidney shaped
Spinous process - short, blunt, projects directly posteriorly
Triangular vertebral foramen
Transverse processes - thin and tapered
Movements allowed by lumbar vertebra
Flexion
Extension
Some lateral flexion
Rotation prevented
Superior and inferior articulating processes of lumbar vertebra
Superior facets directed posteromedially (or medially)
Inferior facets directed anterolaterally (or laterally)
At what level does the trachea begin
C6
Structures found in lung hilum
Pulmonary veins
Pulmonary arteries
Main bronchi
Posteriorly, how far down the ribs does the inferior border of the lungs reach
10th rib
Anteriorly, how far down the ribs does the inferior border of the lungs reach
6th
Laterally, how far down the ribs does the inferior border of the lungs reach
8th
Posteriorly, how far down the ribs does the inferior border of the parietal pleura reach
12th
Anteriorly, how far down the ribs does the inferior border of the parietal pleura reach
8th
Laterally, how far down the ribs does the inferior border of the parietal pleura reach
10th
