Lung Radiology and Histology Flashcards
Extrapleural fascia
Loose, thin layer of connective tissue that separates the parietal pleura from its overlying structures
Pulmonary ligament
Uncovered by pleura. Forms a ‘ dead - space ’ for distension of the pulmonary veins.
Since the parietal pleura is segmentally innervated by the intercostal nerves, infl ammation of the pleura results in. . .
. . . pain referred to the cutaneous distribution of these nerves (i.e. to the thoracic wall or, in the case of the lower nerves, to the anterior abdominal wall, which may mimic an acute abdominal emergency)
The trachea
Commences just below the circoid cartilage and continues until the bifurcation at the sternal angle.
What surrounds the cervical trachea on each side?
Anteriorly – the isthmus of the thyroid gland, inferior thyroid veins, sternohyoid and sternothyroid muscles.
Laterally – the lobes of the thyroid gland and the common carotid artery.
Posteriorly – the esophagus with the recurrent laryngeal nerve lying in the groove between the oesophagus and trachea
What surrounds the thoracic trachea on each side?
Anteriorly – commencement of the brachiocephalic artery and left carotid artery, both arising from the arch of the aorta, the left brachiocephalic vein and the thymus
Posteriorly – esophagus and left recurrent laryngeal nerve
To the left – arch of the aorta, left common carotid and left subclavian arteries, left recurrent laryngeal nerve and pleura
To the right – vagus, azygos vein and pleura
The interior of the trachea is lined with. . .
. . . ciliated respiratory epithelial cells and goblet cells.
Axial radiograph of the thoracic trachea
The golden rule of tracheostomy
Stick to the midline
There are many important structures flanking the trachea.
Widening and distortion of the angle between the bronchi (the carina)
a serious prognostic sign, since it usually indicates carcinomatous involvement of the tracheobronchial lymph nodes around the bifurcation of the trachea.
Dual blood supply of the lungs
Descending aorta -> bronchial arteries -> azygos vein
Pulmonary trunk -> pulmonary arteries -> superior and inferior pulmonary veins
Lymphatics of the lungs
The lymphatics of the lung drain centripetally from the pleura towards the hilum. The bronchopulmonary lymph nodes are at the hilum, and the more efferent tracheobronchial nodes are at the tracheal bifurcation, and the more efferent still paratracheal nodes along the trachea leading to the thoracic duct or right duct.
Innervation of the lungs
The pulmonary plexuses derive fibres from both the vagi and the sympathetic trunk.
They supply efferents to the bronchial musculature (sympathetic bronchodilator fibres) and receive afferents from the mucous membrane of the bronchioles and from the alveoli.
Lung lobe subdivisions
Each lobe of the lung is subdivided into a number of bronchopulmonary segments, each of which is supplied by a segmental bronchus, artery and vein. These segments are wedge - shaped with their apices at the hilum and bases at the lung surface
Named divisions of main bronchi
Transverse and oblique sinuses
Anterior heart view
Posterior heart view
Rupture of a papillary muscle
Allows prolapse of the affected cusp to occur into the atrium at each systole, with consequent acute cardiac failure
chordae tendineae
Connect the papillae to the valves
Location of the sinoatrial node
Situated in the upper part of the crista terminalis just to the right of the opening of the superior vena cava into the right atrium
Location of the atrioventricular node
Situated in the atrial septum immediately above the opening of the coronary sinus
Location of the Bundle of His
Runs from the AV node and divides at the junction of the membranous and muscular parts of the interventricular septum into its right and left branches, which run immediately beneath the endocardium to activate all parts of the ventricular musculature.
When the ventricle contracts in systole, the papillary muscles. . .
. . . shorten, the chordae tendineae are pulled upon and the tricuspid valve is prevented from prolapsing into the right atrium.
Coronary veins
The coronary sinus receives. . .
- the great cardiac vein in the anterior interventricular groove
- the middle cardiac vein in the inferior interventricular groove
- the small cardiac vein – accompanying the marginal artery along the lower border of the heart
- the oblique vein – descends obliquely on the posterior aspect of the left atrium
Innervation of the heart
The nerve supply of the heart is derived from the vagus (parasympathetic cardio - inhibitor) and the cervical and upper fi ve thoracic sympathetic ganglia (cardio - accelerator) by way of superficial and deep cardiac plexuses.
Development of the heart
Developmental heart chambers
Fetal circulation
Dextrorotation of the heart
this organ and its emerging vessels lie as a mirror - image to the normal anatomy
Closing of the foramen ovale
At birth, the septum primum and septum secundum are forced together, closing the flap valve of the foramen ovale. Fusion usually takes place approximately 3 months after birth. In approximately 10% of subjects, this fusion may be incomplete. However, usually, the two septa overlap and this patency of the foramen ovale is of no functional signifi cance.
Atrial septal defects
Ostium primum defect: When the septum primum fails to fuse with the endocardial cushions. Lies immediately above the atrioventricular boundary and may be associated with a defect of the pars membranacea septi of the ventricular septum. Both an atrial and ventricular defect.
Ostium secundum defect: Occurs if the septum secundum is too short to cover the foramen secundum in the septum primum. Allows shunting of blood from the left to the right atrium.
Trilocular heart
Result when ventricular septal defects are so pronounced that the ventricles fuse.
Congenital pulmonary stenosis
May affect the trunk of the pulmonary artery, its valve or the infundibulum of the right ventricle.
If stenosis occurs in conjunction with a septal defect, the compensatory hypertrophy of the right ventricle (developed to force blood through the pulmonary obstruction) develops a suffi ciently high pressure to shunt blood through the defect into the left heart; this mixing of the deoxygenated right heart blood with the oxygenated left - sided blood results in the child being cyanosed at birth.
Fallot’s tetralogy
The most common combination of congenital abnormalities causing congenital cyanosis.
Persistent ductus arteriosus
Relatively common congenital anatomical defect. If left uncorrected, it causes progressive work hypertrophy of the left heart and pulmonary hypertension.
Dysphagia lusoria
Abnormal development of the primitive aortic arches may result in the aortic arch being on the right or actually being double. An abnormal right subclavian artery may arise from the dorsal aorta and pass behind the oesophagus – a rare cause of difficulty in swallowing
Aorta – pulmonary window
Rarely, the division of the truncus into the aorta and pulmonary artery is incomplete. Unusual type of congenital fistula between the two sides of the heart.
Layers of the esophagus
- an outer connective tissue sheath of areolar tissue
- a muscular layer of external longitudinal and internal circular fibres which are striated in the upper two - thirds and smooth in the lower one - third
- a submucous layer containing mucous glands
- a mucosa of stratified epithelium passing abruptly into the columnar epithelium of the stomach
Aortic coarctation
Thought to be due to an abnormality of the obliterative process which normally occludes the ductus arteriosus.
There may be an extensive obstruction of the aorta from the left subclavian artery to the ductus, which is widely patent and maintains the circulation to the lower parts of the body. Circulation to the lower limb is maintained via collateral arteries around the scapula anastomosing with the intercostal arteries, and via the link - up between the internal thoracic and inferior epigastric arteries. Often, there are multiple other defects and frequently infants so afflicted die at an early age.
Alveolus up close
Nasal cavities
nasal cavities NC
nasal septum NS
paranasal sinuses PS
turbinate bones TB
orbital cavities O
anterior cranial fossa ACF
Waldeyer ring
Ring of lymphoid tissue surrounding the entrance to the pharynx. Protects the respiratory and gastrointestinal systems from anything that comes through the oral passage.
Tracheal submucosa
Lying beneath the lamina propria of the trachea, it is full of mucoserous glands which decrease in number as you go lower down the trachea to the bifurcation.
Primary bronchus wall cross section
SEM of primary bronchial wall
Distal bronchus cross section
Respiratory neuroendocrine cell position
Bronchiole cross section
Alveoli H and E
Type 1 and 2 pneumocytes on histology
EM of capillaries, endothelium, and type I pneumocytes
How to identify type II pneumocytes on histology
Their nuclei are large and plump with dispersed chromatin and prominent nucleoli. The plentiful eosinophilic cytoplasm is filled with fine unstained vacuoles representing lamellar bodies that are easily visible on TEM.
Type II pneumocyte on TEM
Lamellar bodies
Bodies are membrane bound and the lamellae within them are composed mainly of phospholipids, particularly palmitoyl phosphatidylcholine. Phospholipid is released by exocytosis, spreading out over the alveolar surface where it combines with other carbohydrate- and protein-containing secretory products (some of which are derived from bronchiolar Clara cells) to form a tubular lattice of lipoprotein described as tubular myelin.
In the event of two alveolar surfaces coming together, this overcomes the effects of surface tension which would otherwise cause them to adhere. This allows for normal inflation of the alveoli at birth and for the reinflation of alveoli which collapse after airway obstruction.
TEM of the basement membrane in an alveolus
Elastin in the alveolar wall
Alveolar walls contain a large amount of elastin, which is condensed to form a supporting ring at the margins of the openings into the alveoli.
Elastin on TEM
The elastin El appears as an amorphous, moderately electron-dense mass which is insinuated between the two cell layers.
Alveolar epithelial cells vs adenocarcinoma cells
TEM of an alveolar macrophage
Alveolar macrophages move freely in alveolar spaces and in the alveolar septa. Their function is the phagocytosis and removal of unwanted material which gains access to the air spaces, such as inhaled particulate matter and bacteria.
After phagocytosing the particles, most macrophages pass into the airways to become trapped in mucus and coughed up as sputum. Others stay in the septa whilst some gain access to the lymphatic system and pass with their phagocytosed material to the hilar lymph nodes.
Conventional radiograph labels
Distinguishing lung borders on a radiograph
Lateral radiograph orientation
Right middle lobe pneumonia with pleural effusion
Identify the fissures
