LUNGS – Detailed Anatomy (Based on Gray’s Anatomy for Students)

Nervous System 

1. Structural Division

• Central Nervous System (CNS):

• Includes brain and spinal cord

• Develops from the neural tube

• Peripheral Nervous System (PNS):

• All nerves outside the CNS

• Includes spinal nerves, cranial nerves, visceral nerves, nerve plexuses, and enteric nervous system

• Develops from neural crest cells and CNS outgrowths

2. Functional Division

• Somatic Nervous System:

• Controls voluntary movements (skeletal muscles)

• Receives sensory info from skin, joints, muscles

• Visceral (Autonomic) Nervous System:

• Controls involuntary functions (heart, glands, organs)

• Includes sympathetic and parasympathetic systems

3. Central Nervous System

Brain:

• Divided into:

• Cerebral hemispheres:

• Outer gray matter = cell bodies

• Inner white matter = axons/tracts

• Contains ventricles filled with CSF

• Cerebellum:

• Two lateral lobes and a midline part

• Brainstem:

• Includes diencephalon, midbrain, pons, medulla

• Often, “brainstem” refers to midbrain + pons + medulla

Spinal Cord:

• Located in the upper 2/3 of the vertebral canal

• Cylindrical shape, with a central canal

• Has gray matter (central) and white matter (outer)

• Connects brain to the rest of the body via spinal nerves

Additional Notes

• Cranial Nerves: Covered in Chapter 8

• Spinal Nerves & Plexuses: Covered in Chapter 2 and in region-specific chapters

• CSF (Cerebrospinal Fluid): Protects and nourishes CNS structures

LEFT LUNG 

General Anatomy

• Smaller than the right lung.

• Has 2 lobes: Superior and Inferior, separated by an oblique fissure.

• Oblique fissure is slightly more angled than on the right lung.

Fissure landmark (during quiet breathing):

• Starts between T3–T4 spinous processes.

• Crosses the 5th intercostal space.

• Follows contour of rib VI anteriorly.

Lung Surfaces

• Superior lobe:

• Contacts upper anterolateral chest wall.

• Apex projects into root of the neck.

• Inferior lobe:

• Faces posterior and inferior thoracic walls.

• Stethoscope placement must match the position of lobes on chest/back.

Unique Features

• Cardiac notch: a depression in the inferior medial surface due to the heart.

• Lingula: a tongue-like projection of the superior lobe that overlaps the heart.

Medial Relations

• Left lung lies near:

• Heart

• Aortic arch

• Thoracic aorta

• Esophagus

• Left subclavian artery/vein pass over the apex into the axilla.

BRONCHIAL TREE 

Trachea

• A flexible tube from C6 (neck) to T4/T5 (chest).

• Bifurcates into:

• Right main bronchus

• Left main bronchus

• Held open by C-shaped cartilage rings (open side faces posteriorly).

• Bottom ring has the carina: a ridge between the bronchi.

Main Bronchi

• Right main bronchus:

• Wider, more vertical

• More likely to receive inhaled foreign bodies

• Left main bronchus:

• Narrower and more horizontal

Bronchi within the lungs

• Each main bronchus enters the lung root through the hilum.

• Branches into:

• Lobar bronchi (one per lobe)

• Then into segmental bronchi (one per bronchopulmonary segment)

Pulmonary Arteries

• Origin: From the pulmonary trunk; carry deoxygenated blood from the right ventricle to the lungs.

• Pulmonary trunk bifurcation:

• Occurs left of midline, just below TIV/V, in front and slightly below the tracheal bifurcation.

Right Pulmonary Artery

• Longer than the left.

• Pathway:

• Passes horizontally across mediastinum.

• Anterior & slightly inferior to tracheal bifurcation.

• Anterior to right main bronchus.

• Posterior to ascending aorta, SVC, and upper right pulmonary vein.

• Branches:

• First branch: to superior lobe.

• Main vessel continues and gives a second (recurrent) branch to the superior lobe.

• Then divides to supply middle and inferior lobes.

Left Pulmonary Artery

• Shorter than the right.

• Pathway:

• Lies anterior to descending aorta.

• Posterior to superior pulmonary vein.

• Passes through root and hilum and branches within the lung.

Pulmonary Veins

• Each lung has a superior and inferior pulmonary vein.

• They carry oxygenated blood back to the left atrium.

• Originate at the hilum, pass through the lung root, and drain directly into the heart.

Bronchial Arteries and Veins

• Serve the nutritive function: supply the bronchi, vessel walls, glands, and visceral pleura.

Bronchial Arteries

• Arise from the thoracic aorta:

• Right side: usually one artery from the 3rd posterior intercostal artery, or from the left bronchial artery.

• Left side: two arteries from the anterior thoracic aorta:

• Superior left bronchial artery at level T5.

• Inferior one just below the left bronchus.

• Run on posterior surfaces of bronchi and branch within the lung.

Bronchial Veins

• Drain into:

• Pulmonary veins or left atrium;

• Or into azygos vein (right) or superior intercostal vein/hemiazygos vein (left).

Innervation

• Via anterior and posterior pulmonary plexuses (near tracheal bifurcation and main bronchi).

• Receive fibers from sympathetic trunks and vagus nerves.

Function:

• Parasympathetic (Vagus nerve): Constricts bronchioles.

• Sympathetic system: Dilates bronchioles.

Lymphatic Drainage

• Superficial (subpleural) and deep lymphatics.

• Drain into tracheobronchial lymph nodes (near bronchi and trachea).

• These nodes extend from the lung to the posterior mediastinum.

Efferent vessels:

• Pass up along the trachea.

• Join with vessels from parasternal and brachiocephalic nodes.

• Form bronchomediastinal trunks (right and left).

• Drain into:

• Deep veins at the base of the neck;

• Or into the right lymphatic trunk or thoracic duct.