Pulmonary Anatomy Flashcards
Conducting Zone Structures
- Trachea
- R and L main (primary) bronchi
- Lobar (secondary) bronchi
- Segmental (tertiary) bronchi
*Segmental bronchi divide repeatedly to form bronchioles, which are less than 1 mm in diameter
Trachea
(windpipe)
- Fibro-musculo-cartilage tube (~11 cm in length)
- Extends from the lower border of cricoid cartilage (opposite C6) to the sternal angle (lower border of T4)
- Divides into R and L principle bronchus at the sternal angle
CARINA = last tracheal rings
Relations of Trachea
Anterior Neck
- Skin, superficial and deep cervical fasciae
- Jugular venous arch (suprasternal space)
- Overlapped by sternohyoid and sternothyroid muscles
- Crossed by isthmus of the thyroid gland, opposite 2nd, 3rd, and 4th rings of the trachea
- Anastomosis between two superior thyroid arteries above the isthmus
- Inferior thyroid veins below the isthmus
Relations of Trachea
Anterior Thorax
- Crossed by the left brachiocephalic vein
- In line with the brachiocephalic trunk and left common carotid artery
- Deep cardiac plexus and the arch of the aorta are near the tracheal bifurcation
Relations of Trachea
Posterior Neck & Thorax
Neck:
- Esophagus
- Recurrent laryngeal nerve on each side, lodging in the trachea-esophageal groove
Thorax:
- Esophagus and left recurrent laryngeal nerve
Relations of Trachea
R & L Thorax
Right:
- R lung & mediastinal pleura
- R vagus nerve
- Arch of azygos vein
Left:
- L lung & mediastinal pleura
- Arch of aorta, L common carotid artery, & L subclavian arteries
Principal/Primary Bronchi
Right:
- Wider, shorter, more vertical
- Foreign body usually aspirated into the right lung through these
Left:
- Longer, narrow, more oblique
Secondary/Lobar Bronchi
- Divisions of the principal bronchus
- 3 on the right, 2 on the left
- Each supplies a lobe of the lung
Tertiary/Segmental Bronchi
- Subdivisions of the secondary bronchus
- Aerates the bronchopulmonary segments of the lung
- 10 total in each lung
Bronchopulmonary Segments
= segments that receive air through one tertiary bronchi (10 in each lung)
- Independent, wedge-shaped respiratory district (bases facing periphery & apex towards lungs)
- Separated by intersegmental areolar septa (prevents spread of infection)
- In line w/ branches of the pulmonary artery
- Branches of the pulmonary vein runs between segments
Bronchovascular segments
- Tributaries of pulmonary veins running in the intersegmental septa
- Bronchovascular segments = areas of the lung drained by an intersegmental tributary of vein
Layers of the Tracheal Wall
Mucosa:
- Ciliated, pseudostratified epithelium w/ goblet, serous, brush, clara, and argentaffin cells (of Kulchitsky)
- Catch foreign bodies entering w/ inspiration
Submucosa:
- Connective tissue w/ seromucous glands
Adventitia:
- Outermost layer; connective tissue encasing C-shaped rings of hyaline cartilage
Tracheal Structures
Trachealis Muscle:
- Connects posterior parts of the cartilage rings
- Contracts during coughing to expel mucus
Carina:
- Last tracheal cartilage rings (hyaline)
- Point of bifurcation into two bronchi
Structures of the Bronchial Tree
- Bronchi -> Bronchioles (divide 15x)
- Cartilage rings become plates (cartilage is absent in bronchioles)
- Epithelium changes from pseudostratified columnar to cuboidal
- Cilia and goblet cells become sparse
- Amount of smooth muscle increases
Respiratory Zone
- Respiratory bronchioles, alveolar duct& alveolar sacs (clusters of alveoli)
~300 million alveoli
- -> account for most of the lung’s volume
- -> main site of gas exchange
Alveoli
- Encased by fine elastic fibers
- Contain open pores that connect adjacent alveoli
- Equalize air pressure throughout the lung
Alveolar walls contain–(1) Single layer of squamous epithelium (type 1 pneumocytes) (2) Scattered type II pneumocytes (3) Alveolar phagocytes
Type 2 Pneumocytes
- Secrete surfactant & antimicrobial proteins
- Usually develops at 24 weeks gestation
- Premature babies lack this –> respiratory problems
Alveolar Phagocytes
- Derived from monocytes, phagocyte bacteria, dust particles, and extravasated RBC’s in CCF
- heart failure cells* or dust cells
- -digest RBCs that leaked from capillaries due to edema
Respiratory Membrane
~0.05 um-thick air-blood barrier
- Alveolar endothelial lining + basement membrane & capillary endothelial lining + basement membrane (fused in places)
Lungs
- Occupy all of the thoracic cavity except the mediastinum
- 10 bronchopulmonary segments per lung
- Lobules are the smallest subdivision; served by bronchioles & branches
Color:
- Rosy pink in newborns
- Dark slaty grey in adults (d/t deposition of carbonacious particles)
Lung Surfaces
- Apex: superior tip
- Base: inferior surface; rests on diaphragm
- Costal: anterior, lateral & posterior surfaces
- Medial: vertebral & mediastinal surface
- Root: site of vascular & bronchial attachments (outside the lung)
- Cardiac notch of left lung: concavity that accommodates the heart
Hilum
area on the mediastinal surface through which blood vessels, bronchi, lymphatic vessels, and nerves enter or leave the lung
A part of the lung
Pathological Processes of Lung Anatomy
- Breath sounds are more audible over the R lung b/c the trachea is closer
- Aspiration is MC in the R lung b/c the R principal bronchus is shorter, wider, & vertical
- Sub-carinal angle > 90 = enlarged
- MC site for lung abscess by aspiration = (1) apical segment of lower lobe (2) posterior segment of upper lobe b/c these segments are most dependent in the recumbent position
- Bronchial segment is more straight
- Tuberculosis is MC in the upper lobe b/c it contains more oxygen
Pulmonary circulation
Low pressure, high volume
- Pulmonary arteries deliver systemic venous blood
^ Branches profusely, along w/ bronchi
^ Feeds into pulmonary capillary networks
- Pulmonary veins carry oxygenated blood from the respiratory zones to the heart
Systemic Circulation
High pressure, low volume
- Bronchial arteries provide oxygenated blood to the lung tissue
^ Arise form aorta
^ Enter lungs at the hilum
^ Supply all lung tissue, except alveoli
- not involved in gas exchange
- Bronchial veins anastomose w/ pulmonary veins, which carry most venous blood back to the heart
Pulmonary Lymphatic Drainage
2 sets of plexus: Superficial, Deep
Broncho-pulmonary (hilar nodes) –> superior & inferior tracheo-bronchial (sub-carinal) nodes –> R and L paratracheal nodes
Superficial Plexus
Pulmonary Lymphatic Drainage
- Ramifies beneath the pulmonary pleura and around the extra-pulmonary bronchi
- Drains into the bronchi-pulmonary lymph nodes at the hilum (hilar nodes)
Deep Plexus
Pulmonary Lymphatic Drainage
- Arranged around the intrapulmonary bronchi & inter-lobular septa
- Drains into the bronchi-pulmonary lymph nodes (hilar nodes)
Nerve Supply of the Lungs
- Supplied by the anterior and posterior pulmonary plexuses, which surround the lung roots
- Sensory fibers are mostly parasympathetic
- Act as stretch receptors (j-receptors) around the lung alveoli –> reflex control of respiration (e.g. Hering-Breuer reflex)
- Irritation of the nerve endings in the bronchial mucous membrane initiates the cough reflex
Pulmonary Plexus
Parasympathetic fibers:
- Vagus nerves
- BronchoCONSTRICTORS & secretomotor to bronchial glands (increase mucus secretions)
Sympathetic fibers:
- Upper 4 or 5 thoracic ganglia of the sympathetic trunks
- BronchoDILATORS & vasomotor
Right Lung
- Shorter, wider, more capacious
- Weight – 20 oz.
- 3 lobes, separated by 2 fissures
- Base, more concave
- Absence of cardiac notch
- Absence of lingula
- Usually supplied by 1 bronchial artery
Left Lung
- Longer, narrower, less capacious
- Weight – 18 oz.
- 2 lobes, separated by 1 fissue
- Base, shallow
- Presence of cardiac notch
- Presence of lingual (superior & inferior) corresponds w/ the middle lobe of the R lung
- Usually supplied by 2 bronchial arteries
Pulmonary Pleurae
- Thin, double-layered serosa*
- Parietal pleura on thoracic wall & superior face of diaphragm
- Moves w/ thoracic cage (inspiration)
- Visceral pleura on external lung surface except at the hilum & attachment of the pulmonary ligament
- Shiny, glistening
- Pleural fluid fills the slit-like pleural cavity
- Provides lubrication & surface tension
Recess of Pleura
Costo-diaphragmatic: Cleft-like potential space b/t the lower limit of the pleural sac & the lower lung border
- Costal & diaphragmatic pleura are in apposition in quiet respiration
- Most dependent part of the pleural sac (1st place to collect fluid in pleural effusion)
Costo-mediastinal:
- Behind the sternum & the costal cartilages
Pleural Blood Supply
Arteries:
- Costovertebral pleura–intercostal & internal thoracic arteries
- Mediastinal pleura–branches of bronchial, internal thoracic, upper diaphragmatic & mediastinal arteries
- Cervical pleura–branches of subclavian arteries
Veins:
- Drain into systemic veins in the thoracic wall –> drains into the superior vena cava
Pleural Lymphatic Drainage
- Costovertebral pleura drains to the internal thoracic & intercostal chain
- Diaphragmatic pleura drains into the mediastinal, retrosternal, & coeliac axis nodes
Visceral Pleura
- Integral part of the lungs*
- Arterial supply & venous drainage provided by the bronchial vessels
Pleural Nerve Supply
- Costal & peripheral diaphragmatic parietal pleura innervated by intercostal nerves
- Mediastinal & central diaphragmatic pleura supplied by the phrenic nerve
Irritation of the parietal pleura is referred to the respective dermatomes
Pleurisy or Pleuritis
Inflammation of the pleura
- S/S: Chest pain
- If not treated, will lead to pleural effusion
Pleural Effusion
- Accumulation of a significant amount of fluid in the pleural cavity (serous, transudate, exudate-pus, blood-hemothorax)
- Causes: inflammation, trauma, congestive heart failure
Paracentesis
- Pleural Tap*
- Usually performed posterior to the mid-axilary line at 1 or more intercostal spaces below the fluid level w/ the pt in a sitting position (not below the 9th ICS)
Pneumothorax
= Air in the pleural cavity
2 types: Open & Tension
Muscles of Respiration
- Diaphragm
- Intercostalis
- Abdominal recti
- Sternocleidomastoid
- Serratus anterior
- Scaleni
Diaphragm
*Principal muscle of respiration
Origin: Inner surfact of the thoracic outlet in 3 groups-(1) sternal (2) costal (3) vertebral (e.g. lumbar)
Insertion: Into the central tendon
Diaphragm Nerve Supply
Motor–phrenic nerve
Sensory–phrenic & lower 6 or 7 intercostal nerves
*Hiccups occur when the phrenic nerve is irritating –> diaphragm contraction
Diaphragm Blood Supply
- Musculophrenic & pericardio-phrenic branches of the internal thoracic artery
- Lower 5 or 6 posterior intercostal artery
- Superior phrenic artery–last branch of descending thoracic artery
- Inferior phrenic artery–first branch of the abdominal aorta
Intercostal Muscles
- Arranged in 3 sheets
- From outside inwards:
- Intercostalis externa
- Intercostalis internus
- Intercostalis intimus
Intercostalis Externa
- Origin: lower border of upper rib
- Insertion: outer lip of the upper border of the lower rib (anteriorly it forms the anterior intercostal membrane)
- Direction: downwards, forwards, & medially in the anterior portion; downwards & laterally in the posterior portion
Intercostalis Internus
- Origin: costal groove of the upper rib
- Insertion: intermediate part of the upper border of the lower rib
- Posteriorly it forms the posterior intercostal membrane
- Direction: right angles to the intercostalis extern
Intercostalis Intimus
- Absent in upper 2 ICS
- Origin: upper lip of the costal groove of the rib above
- Insertion: inner lip of the upper border of the rib below
- Direction: right angles to the intercostalis extern
Intercostal Muscle Nerve Supply
Ventral ramus of a thoracic nerve (corresponding to the intercostal nerves)
Anterior Intercostal Muscle Blood Supply
- Anterior intercostal arteries*
- Upper 6 spaces: branches of the internal thoracic arteries
- Succeeding 3 spaces: branches of the musculo-phrenic artery
Last 2 spaces are devoid of anterior intercostal arteries
Posterior Intercostal Muscle Blood Supply
- Posterior intercostal arteries*
- Upper 2 spaces receive from superior intercostal arteries (branch of the costocervical trunk of the subclavian artery)
- Lower 9 spaces derived from the descending thoracic aorta
