Anatomy of the Lungs and the Bronchial Tree Major Vessels and Nerves of the Thorax

Lungs (General)

main organ of respiration

part of respiratory system with

• nose

• nasal cavities+sinuses

• pharynx

• bronchial tree

Respiration

gas exchange between environment+circulatory system

facilitates

• oxygenation of blood

• removal of CO2

Position of the Lungs

location→thorax

inferior boundary→respiratory diaphragm

• separates thoracic+abdominal caivities

• role/function→respiration

thoracic cavity→L+R lungs

• surrounded by→pleura+pleural cavity

• separated by→mediastinum→houses the heart

anchored to mediastinum via

• bronchi

• pulmonary A+V

• nerves

Pleura+Pleural Cavities (General)

surrounded by: pleura→in a double membrane

serous membrane

• fluid-filled space

• subdivided into two portions

portions of pleura

• parietal layer (superficial)

• visceral layer (deep)

Pleura

two types of pleura

• parietal layer→closest to thoracic wall (superficial)

• visceral layer→adheres to lung (deep)

two layers continuous with eachother→at root of lung as a reflection

separated by pleural cavity

potential space enclosed by:

• visceral pleura (superficial)

• parietal pleura (deep)

separated by pleural cavity→the potential space enclosed between the visceral+parietal pleurae

serous fluid

• between visceral+parietal layers

• surface of lung+visceral layer→slide freely over parietal pleura attached to the wall

• “fist in a balloon” model

Pleural Cavities

fluid-filled space

between visceral+parietal portions of pleura

lined with

• single layer of cells→mesothelium

• supportive connective tissue

Parietal Pleura

portions named for areas of thoracic wall they are close to

costal part→ribs+intercostal spaces

diaphragmatic part→diaphragm

mediastinal part→mediastinum

Clinical Importance of Pleural Cavity

very small→will not see it

air introduced into pleural cavity→lung collapses→pneumothorax

fill with fluid→pleural effusion

fill with blood→hemopneumothorax

tx→remove air/fluid/blood

Pleural Recesses (General)

lungs→don’t fill anterior/posterior regions of pleural cavities→recesses

• two layers of parietal pleura opposed to eachother

• exampnsion of lungs into recesses→only on forced inspiration

• clinical→collection of fluid→sites for fluid

Comstmediastinal Recess Location

anteriorly

where costal pleura opposed to mediastinal pleura→larger on left slide→overlying heart

Costodiaphragmatic Recess Location

largest

clinically important→fluid aspiration

1 per side

location

• between costal+diaphragmatic pleurae

• between inferior margin of lungs+inferior margin of pleural cavities

• inspiration→smaller

• expiration→larger

Pulmonary Ventilation

process of respiration

inspiration→gas flows into lungs

expiration→gas flows out of lungs

dependent on changes in volume of thoracic cavity

• inverse relationship between volume+pressure

• change in volume→change in pressure

• flow of gases to equalize pressure gradients

Volume Changes (General)

volume of thorax change→muscle contraction

• respiratory diaphragm→domed to flat→increases volume of thoracic cavity+decreases pressure of thoracic cavity

• external intercostal muscles→cause rib cage to rise→decreases volume of thoracic cavity+increases pressure of thoracic cavity

pleura firmly attached to walls of rib cage+lungs

• lungs→expand with ribcage

• volume→increases

• pressure in lungs (in relation to outside of body)→decreases

• movement of air→into lungs

Volume Changes: Inspiration

1. inspiratory muscles contract
   -diaphragm→descends
   -rib cage→rises

2. thoracic cavity volume increases

3. lungs stretched+intrapulmonary volume increases

4. intrapulmonary pressure drops→-1mmHg

5. air/gases flows into lungs down its pressure gradient→until intrapulmonary pressure is 0 (equal to atmospheric pressure)

Volume Changes: Expiration

1. inspriatory muscles relax
   -diaphragm→rises
   -rib cage→recoil of costal cartilages→descends

2. thoracic cavity volume decreases

3. elastic lungs recoil passively+intrapulmoanry volume decreases

4. intrapulmonary pressure rises→_1mmHg

5. air/gases flows out of lugns down its pressure gradient→until intrapulmonary pressure is 0

Forced Expiration

passive→muscles relax→quiet expiration

active→contraction of other muscles
-internal+innermost intercostals
-abdominal muscles

Comparison of Anatomy of Left+Right Muscles

differ from eachother in terms of

• number of lobes

• fissues separating lobes

• size

• other morphological differences

similarities

• apex

• diaphragmatic surface
  -concave
  -contracts diaphragm

• superior lobe

• inferior lobe

• oblique fissure→separates superior+inferior lobes

differences

• right lobe→middle lobe

• right lobe→horizontal fissure→separates superior+middle lobes

• left lobe→cardia notch
  -heart→buldges more to left
  -left lung smaller than right lung

• lingula
  -tongue-like extension
  -over buldge of heart

Left Lung Fissures

olique fissure→separates superior+inferior lobes

Right Lung Fissures

oblique fissure→separates superior+inferior lobes

horizontal fissure→separates superior+middle lobes

Root

on both L+R lungs

collection of structures

attach lung to mediastinum

components

• bronchus

• pulmonary A+V

landmark for nerves

• just posterior to root→vagus N

• anterior to root→phrenic N

Hilum

on both L+R lungs→central on medial border

area of entrance+exit of main vessels of lung

• pulmonary A+V

• bronchus

Pulmonary Arteries

RV of heart→pulmonary trunk A→L+R pulmonary As

deoxygenated blood: heart→lungs
-carries blood away from heart→artery (“artery=away”)

location

• usually superiorly placed in hilum

• cut close to lung→might appear as 2 arteries

L+R Pulmonary Veins

carry oxygenated blood→from lungs→LA of heart

superior+inferior pulmonary Vs→for both L+R lung

2 veins per lung

• superior pulmonary vein

• inferior pulmonary vein

Bronchi

each lung→1 main bronchus

how air enters+exits lungs

posteriorly placed

part of bronchial tree→branch off of trachea

Bronchial Tree Pathway

1. trachea (single)

2. bifurcates→2 main bronchi

3. carina

4. enter lungs

5. main bronchus

6. lobar bronchi

7. segmental bronchi

8. divisions of bronchopulmonary segment

9. bronchioles

10. alveoli

Bronchial Tree: Trachea

single structure

• vertebral c6-t4/5

• flexible tube

• c-shaped cartilaginous rings→strengthen
  -c-shape→

Bronchial Tree: Main/Primary Bronchi

enter the lungs

last tracheal ring before bifurcation→carina→hook-shaped (pair of underwear)

right main bronchus

• wider

• more vertically oriented

• clinical→m/c for inhaled objects

Bronchial Tree: Lobar/Secondary Bronchi

division from main bronchus→occurs within the lung

each supplies a lobe→3 in right lung
-superior lobe lobar bronchi→emerges within root of lung

Bronchial Tree: Segmental/Tertiary Bronchi

divison from lobar bronchi

each supply a bronchiopulmonary segment

give rise to many smaller divisions

Bronchioles

divides from segmental bronchi

no cartilage

Alveoli

branches off of bronchioles

primary site of gas exchange in the lung

Bronchopulmonary Segments

smallest functionally independent region of a lung

each supplied by segmental bronchus+branch of pulmonary A
-10 segments per lung (left lung→can fuse together)

clinical importance→smalles area in lung that can be isolated+removed

Surface Anatomy of Lungs: Counting Ribs

1. use palpable landmarks
   -jugular notch of manubrium

2. move down sternum until you feel a ridge
   -ridge between manubrium+body of sternum

3. move laterally to find costal cartilage of rib 2
   -rib 1→not palpable

4. continue counting working down sternum

Surface Anatomy of Lungs: Right Lung Placement

anterior view

superior lobe extent

superior to clavicle→inferior to rib 3

horizontal fissure

• superior to rib 4

• intercostal space between ribs 3+4

middle lobe

• level of ribs 4+5

• superior portion of costal cartilage of rib 6

inferior lobe

• laterally

• at level of bony ribs 6+7

Surface Anatomy of Lungs: Left Lung Placement

anterior view

superior lobe

• superior to clavicle→rib 5

• costal cartilage of rib 6

inferior lobe

• laterally (safe to say)

• at level of rib 6

Surface Anatomy of Lungs: Visualizing L+R Lungs in Posterior View

same for both lungs

superior lobe→t2-t4

oblique fissures→follow curve of rib 6

inferior lobe→t5-t10

oblique fissure

• medial border of rotated scapula→overlies oblique fissure

• superior to it→superior lobe

• inferior to it→inferior lobe

Stethoscope Placement: Anterior Surface of L+R Lungs

apex→superior to clavicle

superior lobe→between ribs 2+3

middle lobe of right lung→between ribs 4+5

inferior lobe

• laterally

• inferior to rib 6

Stethoscope Placement: Posterior Surface of L+R Lungs

apex→rib 1

superior lobe→between ribs 3+4

inferior lobe

• laterally

• inferior to rib 8

Aorta Pathway

1. in thorax→emerges from heart (ascending aorta A)

2. curves→aortic arch A

branches off aortic arch A

• brachiocephalic trunk A
  -R common carotid A
  -R subclavian A

• L common carotid A

• L subclavian A
  -internal thoracic A→under transversus thoracis A

3. continues down thorax→descending aorta A

4. through diaphragm

5. into abdomen→abdominal aorta A

Branches off Internal Thoracic Artery

multiple anterior intercostal As

ends around→6th intercostal space

divides into

• superior epigastric A
  -supplies anterior abdomnial wall

• musculophrenic A
  -passes through diaphragm

Intercostal Arteries (Anterior+Posterior

between ribs→emerge from different As

supplies→thoracic wall

Posterior Intercostal Artery

intercostal As 1+2→different pathway

branch off supreme intercostal A
costocervical trunk A→off of subclavian A

remaining 9 pairs
branch off of aorta

Anterior Intercostal Artery

upper anterior intercostal A→branches off of internal thoracic A

after bifurcation of internal thoracic A→lower anterior intercostal A→branches off of musculophrenic A

Arterial Supply to Breast

supply from vessels in upper limb+thoracic wall

• laterally→axillary A vessels

• medially→internal thoracic A branches

• intercostal As 2-4

Anterior+Posterior Intercostal Arteries Location

protected by costal groove

intermediate between intercostal V+N

important to think of for (clinical)

• perforating wounds

• chest tubes

• etc.

Veins of the Thorax

1. internal jugular V

2. merges with subclavian V

3. forms brachiocephalic V

4. R+L brachiocephalic Vs

5. superior vena cava V

6. RA of heart

between ribs (in intercostal spaces)→intercostal Vs

L+R intercostal V drainages=different

• superiorly-placed L intercostal Vs→accessory hemiazygos V

• inferiorly-placed L intercostal Vs→hemiazygos V

• R intercostal Vs 2-12+accessory hemiazygos V+hemiazygos V→azygos V

Azygos V

posterior intercostal Vs 2-12→drain into azygos v→superior vena cava V

right side of body

Left Intercostal Veins (Hemiazygos+Accessory Hemiazygos Veins)

accessory hemiazygos vein

superiorly-placed intercostal veins→crosses over vertebral bodies→azygos v

hemiazygos vein

inferiorly-placed intercostal veins→crosses over vertebral bodies→azygos v

Intercostal Nerves (General)

innervation of thoracic wall→anterior rami of T1-T11

lie in intercostal spaces→not protected by bony rib

Intercostal Nerves Somatic Innervations (Sensory+Motor)

sensory

• skin

• pleura

motor

• intercostal

• subcostal

• transversus thoracis

Phrenic Nerve (General)

L+R sides

arises from

• anterior rami of spinal nerves c3-c5

• major contributor→c4

innervations

sensory+motor→responsible for innervating respiratory diaphragm

somatic afferent fibers:

• fibrous pericardium

• serous pericardium→parietal layer

Phrenic Nerve Pathway

1. descends down neck

2. through thorax

3. L+R sides of pericaridium

4. diaphragm

5. meidal to lung+anterior to root

6. passes through thorax

7. arises from atnerior rami of spinal nerves

Phrenic Nerve Clinical Significance

spinal cord damage

below level of phrenic→diaphragm not effected

at level of phrenic/above→ventilator for life

Vagus Nerve (CN X) (General)

longest cranial N
pass through superior+posterior division of mediastinum→abdominal cavity

posterior to roots of lungs

innervations

• parasympathetic→thoracic viscera

• visceral afferents→from thoracic viscera

Right Vagus Nerve (CN X) (Branches+Pathway)

branches

• esophagus

• cardiac plexus

• pulmonary plexus

pathway

1. passes through superior mediastinum

2. descends towards trachea

3. crosses lateral surface of trachea

4. posterior to right foot of lung→esophagus

Left Vagus Nerve (CN X) (Branches+Pathway)

branches

• esophagus

• cardiac plexus

• pulmonary plexus

pathway

1. passes through superior mediastinum

2. crosses left side of aortic arch A

3. posterior to root of left lung→esophagus

Recurrent Laryngeal N

arises off vagus Ns→ascends up neck

supplies→larynx

different paths for L+R Ns

R→loops under subclavian A

L→loops under aortic arch A

Pulmonary Plexus+Branches+Innervations

lung+visceral pleura→supplied by visceral afferents+efferents via 2 interconnected plexuses

• anterior pulmonary plexus

• posterior pulmonary plexus

lie near→bifurcation of trachea

branches

• airways

• vessels

on plexuses:

• sympathetic trunk

• vagus Ns

visceral efferents

• vagus N→constricts bronchioles

• sympathetic system→dilates bronchioles