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 Diaphragm ≈ 9th-11th rib COPD = Lower Rt Lung = 3 lobes Lt Lung = 2 lobes Which one has less volume? Left side… Because of the heart

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 Pulmonary ligament 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 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 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 Parietal pleura Pleural space attached to lung’s surface Parietal pleura inner chest wall surface Pleural space potential space between visceral and parietal pleura 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

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

Somatic nervous system 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 Affarent – Signals that are transmitted to the brain and spinal cord Somatic Neurons send motor signals… Motor signals are those signals that tell the body to lift, walk, or breath… In order for you to manipulate and stop these neurons, you have to induce paralysis… Those drugs are called “neuromuscular” blocking agents… Autonomic Nervous System controls the involuntary movements of the body… For example – Heart Rate… Pupil Dilation… Salivation… And from here you can break it up into two categories… The parasympathetic and sympathetic branches. Somatic nervous system

Autonomic Afferent Neurons Somatic Neurons So again, you have the affarent neurons… They send signals regarding what you see, feel, hear… They send signals back to the brain and spinal cord The Somatic motor neurons are voluntary control of the skeletal muscle… Your brain sends signals whenever you want to lift, walk, or run… And then the Autonomic are the signals that are sent that you have no control over… They are called “involuntary” control… heart beat.. Eye dilation… adrenaline pumping… etc.. Table 2-1 (pg. 29) shows you the function of the Somatic And Autonomic System. Ach = Acetylcholine NE = Norepinephrine Both of these are what we call “neurotransmitters”… These are chemicals your body produces and shoots from the end of the nerves… It’s like “wifi” transmission… but chemicals… with no nerve attached…

Phrenic nerves Intercostal 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 Phrenic Nerves Originate from C3 – C5 of the cervical (head) nerves

Autonomic Innervation Controls Involuntary Movements Example: Heart Rate… Pupil Dilation… Salivation… Two branches arise: Sympathetic Parasympathetic Autonomic Nervous System controls the involuntary movements of the body… For example – Heart Rate… Pupil Dilation… Salivation…

Sympathetic (Adrenergic) Innervates adrenal medulla Neurotransmitter = Noradrenaline Aka norepinephrine Alpha, Beta 1, Beta 2 Stimulation of ß2 receptors in the airway causes bronchodilation Draw both sides of the system

Which would you recommend? Alpha vs. Beta 2 Upper airway swelling s/p extubation Lower airway wheezing/asthma clinical Focus 2-4 pg. 36 This question is in clinical Focus 2-4 pg. 36

Parasympathetic (Cholinergic) Innervates smooth airway muscle mucous glands pulmonary vasculature Neurotransmitter = Acetylcholine Overstimulation bronchospasm increased mucous production & thickness Innervates = excites

Thoracic Anatomy Thorax is formed by rib cage and intercostal muscles vertebrae sternum diaphragm

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) Diaphragm (major effect) parasternal intercostals (minor effect) Scalenes (minor effect) scalenes (inspiration) sternomastoids (inspiration) pectoralis major (inspiration) abdominals (expiration)

Muscles of Ventilation Diaphragm (major effect) Scalenes (minor effect) scalenes (inspiration) sternomastoids (inspiration) pectoralis major (inspiration) abdominals (expiration) Fig. 2-13