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B313-05-Lungs

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Daniel Howell

on 27 September 2018

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Transcript of B313-05-Lungs

The Lungs
Viscera of Thoracic Cavity
In transverse section, the thoracic cavity is kidney shaped.

Deep posterior indentations caused by vertebral column (vertebral gutters)
Pleura,
Lungs
& Tracheobronchial Tree
Thoracic cavity divided into three compartments
Left and right pleural (pulmonary) cavities
Mediastinum

Pleural cavities lined with visceral & parietal pleural membrane filled with pleural fluid
Tracheobronchial Tree
The trachea is held open by C-shaped cartilaginous (hyaline) rings

Trachea represents the trunk of the tracheobronchial tree

Trachea bifurcates at the level of the sternal angle to form primary (main) bronchi which enter lungs at hila

Right main bronchus is wider, shorter and more vertical than left main bronchus
Diaphragm & Base of Pleural Cavities
The Lungs
Two lungs separated by the mediastinum

Each lung
enclosed by pleural cavity
apex extending into root of neck
concave base sits upon dome of diaphragm
four surfaces (cervical, costal, mediastinal, diaghragmatic)
three borders (anterior, posterior, inferior)
fissures (2 on right, 1 on left)
The Lungs - Mediastinal Surface
Mediastinal surface of both lungs concave to allow for mediastinal structures, esp. the heart (cardiac impressions)

Left lung has deep depression (cardiac notch) for the apex of the heart and usually a lingula

Location of the lung hilum which surrounds the root of the lung

Phrenic nerve passes anterior to root; vagus nerve passes posterior to root
Tracheobronchial Tree
Right lung: three lobar bronchi

Left lung: two lobar bronchi

Lobar bronchi branch into several tertiary (segmental) bronchi
Inside the lung, each primary (main) bronchus divides into secondary (lobar) bronchi
Bronchiopulmonary Segments
The largest subdivisions of a lobe

Pyramidal-shaped segments
apices toward root
bases at the pleural surface

Separated by connective tissue septa
Supplied by independent segmental bronchus & pulmonary vessels

Usually 10 in right lung; 8-10 in left lung
Bronchioles & Alveoli
Vasculature of Lungs & Pleura
Most lung tissues get nutrients and oxygen from pulmonary circuit arteries (pulmonary arteries) arising from pulmonary trunk

Lung tissues are drained by two pulmonary veins from each lung (sup. / inf.) and carry oxygen-rich blood to systemic circuit

Bronchial arteries (systemic circuit) arise from aorta and supply lung supporting tissues (e.g., pleura)

Bronchial veins (systemic circuit) drain into SVC
Inferior left lung "quadrant" and entire right lung drain to the right side of the body
Inferior left & right "quadrants" drain into centrally-located inferior tracheobronchial lymph nodes
Superior right lung "quadrant" drains into right superior tracheobronchial lymph nodes
Lymph drainage from lung mirrors pattern of drainage for body as a whole
Superior left lung "quadrant" drains into left superior tracheobronchial lymph nodes
Surface Anatomy of Pleurae & Lungs
Pulmonary Collapse
Like a balloon, the lungs are inherently elastic

Lungs are held open by surface tension (hydrogen bonds) between visceral and parietal pleura via pleural fluid

Elastic nature of lungs keeps intrapleural pressure negative (sub-atmospheric), between -2 mm Hg and -8 mm Hg

If the surface tension is broken, the lung will collapse (secondary atelectasis)
Pneumothorax & Hemothorax
Pneumothorax = entry of air into the pleural cavity
Caused by puncture wound (knife, bullet, fractured rib, gas from infection, etc.)
Results in collapsed lung

Hemothorax = entry of blood into the pleural cavity
More commonly caused by major blood vessel injury than laceration
Thoracentesis
Thoracentesis = Penetrating the thoracic wall with a hypodermic needle to obtain a sample of pleural fluid (or remove blood, pus, etc.)

When the patient is standing upright, pleural fluid accumulates in the costodiaphragmatic recess.

Needle is angled upward and inserted in the 9th intercostal space high enough to avoid nerve/blood vessels while patient exhales
Insertion of Chest Tube
Large amounts of air/fluid are usually removed using a chest tube

Chest tube inserted at the 5th or 6th intercostal space at the midaxillary line (approximately nipple level)

The tube may be directed superiorly to remove air or inferiorly to remove fluid

Removal of air allows reinflation of a collapsed lung
Thoracoscopy
Thoracoscopy = using a thoracoscope to examine the pleural cavity, obtain a biopsy or treat some thoracic conditions (e.g., disrupting adhesions or removing plaques)

Small incisions for instruments made into pleural cavity via intercostal space
Pleuritis
Pleuritis = inflammation of the pleura

Usually no sounds are heard from the pleura during auscultation; during pleuritis inflammation makes lung surfaces rough producing sounds in a stethoscope

Sounds like a clump of hair being rolled between two fingers

Inflammed pleura may cause parietal and visceral surfaces to adhere (pleural adhesion) causing acute, sharp, stabbing pain
Percussion of the Thorax
Percussion helps establish whether underlying tissue is air-filled (resonant sound), fluid-filled (dull sound) or solid (flat sound)

Not only used to locate organs, but indicate infection (for example, fluid in the lungs from pneumonia)
Bronchoscopy
Using a bronchoscope to examine the trachea, carina, and bronchi

The mucous membrane of carina is very sensitive and associated with the cough reflex

Inverting a choking victim can also initiate cough reflex by lung secretions reaching the carina
Partial Collapse / Segmental Atelectasis
Segmental Atelectasis = partial lung collapse; collapse of a single lung segment

May be caused by aspiration of a foreign object lodged in segmental bronchus

Air in the affected segment is eventually absorbed into blood and segment collapses

Does not lead to realization of pleural space because adjacent segments expand to fill the volume of the collapsed segment
Pulmonary Embolism
Pulmonary embolus = obstruction of a pulmonary artery by a blood clot (embolus); commonly fatal

A blood clot from a leg vein after a compound fracture (for example) can pass through the right side of the heart and get lodged in pulmonary artery supplying the lung

The result of a PE is a lung or lung segment ventilated with air but not perfused with blood

In addition to oxygen deprivation, the right heart may become acutely dilated because arriving blood cannot be ejected

Oxygen deprivation to the lung may lead to pulmonary infarct; often avoided by anastomoses
Chest X-ray
The most common radiographic study of the thorax is the posteroanterior (PA) projection producing a PA radiograph
AP projections create distortions (size of heart, etc.)
Usually performed if patient too weak to stand

Used to examine thoracic respiratory and cardiovascular structures

Taken during inspiration, the lungs are filled with air and translucent, the costodiaphragmatic recess clearly visible above the dome of the diaphragm; Pleural effusions make the recess appear hazy

Lobar disease (e.g., pneumonia) appear as localized, radiodense areas

The heart, sternum, clavicles, ribs, and diaphragm are clearly visible in PA radiographs
Effects of Smoking on the Lungs
Healthy lungs are light pink; smoker lungs are dark and mottled by carbon particles

Toxins in cigarette smoke paralyze cilia and arrests mucus escalator --> smoker's cough

Trapped particles can lead to anaplasia (de-differentiation) in lung cells --> cancer
Enlarged tracheobronchial lymph nodes (from a bronchiogenic carcinoma, for example) may cause carina to be distorted, widened or immobile
Daniel Howell, PhD
Liberty University

The Pleura & Lungs
*primary atelectasis = failure to inflate lung at birth
Partial Collapse / Lobar Atelectasis
The whole lung need not collapse

One lobe, or one or several segments may collapse

Not usually caused by breach of thoracic wall
cystic fibrosis
infection
failure to produce surfactant
blocked airflow
Lymphatic Drainage of the Lungs
BIOL 313
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