The Lungs and Chest Wall
Chapter 2
The Lungs as Organs
• Apex: upper rounded part of lung
– apices extend above clavicles
• Base: lower concave part of lung
– Rests on the diaphragm
– Major muscle of ventilation
– Separates the thoracic and abdominal cavity
• Mediastinum contains heart, aorta, esophagus,
great veins, trachea, mainstem bronchi
Lung Topography
Lung Features
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•
•
•
Diaphragm ≈ 9th-11th rib
COPD = Lower
Rt Lung = 3 lobes
Lt Lung = 2 lobes
• Which one has less volume?
Lungs as Organs (cont’d)
• Cardiac notch—left lung’s anterior border
• Diaphragm—major muscle of ventilation
– Separates thorax from abdomen
– Dome-shaped
• Lower margin at T10
• Highest margin T8-T9
– Right hemi-diaphragm is higher than left
• Liver pushes it up; heart pushes left side down
• Hilum
– where arteries, veins, and bronchi enter and leave lungs
• Pulmonary ligament
– connects lung’s surface membrane with diaphragm
• Lingula: tongue-like anterior portion of left
upper lobe that overlaps heart
– Lingula = counterpart of right middle lobe
Pleural Membranes
• Form sealed envelope around each lung
• Visceral pleura
– attached to lung’s surface
• Parietal pleura
– attached to inner chest wall surface
• Pleural space
– potential space between visceral and parietal pleura
Pleural Membranes
• Visceral pleura
attached to lung’s
surface
• Parietal pleura
inner chest wall surface
• Pleural space
potential space between visceral and parietal pleura
Costophrenic Angles
• Where lowest margin of diaphragm meets chest
wall
• Pleural effusion
– fluid in pleural space
– fluid settles into costophrenic angles, blunting their
points on chest x-ray images
– thoracentesis — surgical removal of excess pleural
fluid via tube insertion into pleural cavity
Blood Supply to the Lungs
• Mr. Cosa’s Drawing
Rough Schematic
Pulmonary Blood Flow
Regulation of fluid in the lung:
Lymphatic System
• Lymph: clear, protein-containing fluid in interstitial spaces
(Pleura)
• Normal fluid filtration
– 30 L plasma/day filters into interstitium
– 27 L plasma/day gets reabsorbed
– 3 L in lung interstitium returns to the systemic circulation via the
lymphatic system
• If Lymphatic System does not filter the 3 L out, it can accumulate
in the alveoli and cause pulmonary edema
The Nervous System
• Central nervous system (CNS)
– Brain & Spinal cord
• Peripheral nervous system
(portion of nervous system laying outside brain and spinal cord)
– Sensory (afferent) neurons – Carry signals that are
transmitted to the brain and spinal cord
– Motor (efferent) neurons – carry signals away from CNS
– Autonomic nervous system
Non voluntary
• Parasympathetic branch
• Sympathetic branch
Somatic nervous
system
Afferent Neurons
Autonomic
Somatic Neurons
• Phrenic nerves
– Stimulation of Diaphragm
– If injury from surgery, disease, or trauma
• may paralyze diaphragm
• breathing is possible if accessory nerves are intact
• Intercostal nerves
– spinal nerves that stimulate/innervate intercostal
muscles
Autonomic Innervation
• Controls Involuntary Movements
• Example: Heart Rate… Pupil Dilation…
Salivation…
Two branches arise:
• Sympathetic
• Parasympathetic
Sympathetic (Adrenergic)
• Innervates
– adrenal medulla
• Neurotransmitter = Noradrenaline
– Aka norepinephrine
• Alpha, Beta 1, Beta 2
• Stimulation of ß2 receptors in the airway
causes bronchodilation
Which would you recommend?
• Alpha vs. Beta 2
• Upper airway swelling s/p extubation
• Lower airway wheezing/asthma
clinical Focus 2-4 pg. 36
Parasympathetic (Cholinergic)
• Innervates
– smooth airway muscle
– mucous glands
– pulmonary vasculature
• Neurotransmitter = Acetylcholine
• Overstimulation
– bronchospasm
– increased mucous production & thickness
Thoracic Anatomy
• Thorax is formed by
Thoracic Cage
• 12 ribs
– 7 attach directly to sternum anteriorly
– 3 (ribs 8-10) connect to sternum
– 2 do not attach anteriorly
• floating ribs
• Puncture – Pneumothorax
• Fracture – Flail Chest
Ventilatory Muscles
• Primary muscles used for quiet breathing
– Diaphragm (major effect)
– Scalenes (minor effect)
• Accessory muscles used for increased work of
breathing (WOB)
– scalenes (inspiration)
– sternomastoids (inspiration)
– pectoralis major (inspiration)
– abdominals (expiration)
Muscles of Ventilation
Fig. 2-13