Thoracic Wall; Pleural Cavities and Lungs

Question 1

What are the body wall layers of the thorax, superficial to deep?

Answer 1

• Skin
• Superficial Fascia
• Muscles of the upper limb
• Intercostal muscles
• Endothoracic fascia (areolar CT)
• Paretal Pleura
• Thoracic Cavity

Question 2

Intercostal Muscles

Answer 2

• Muscles of respiration
• From superifical to deep:
  
  • External Intercostals
  • Internal Intercostals
  • Innermost Intercostals and Transversus Thoracis
• Contents of Intercostal Spaces (Costal Groove of Inferior Rib):
  
  • Vein
  • Artery
  • Nerve

Question 3

Transversus Thoracis Muscle

Answer 3

• At the same “depth” as the innermost intercostals
• On anterior thoracic wall
• Attaches from sternum to 2nd-6th costal cartilages

Question 4

Innervation of Thoracic Wall

Answer 4

• Anterior rami of intercostal nerves (T1-T11)
  
  • **T12 is the subcostal nerve and doesn’t innervate thoracic wall, it innervates the abdominal wall

Question 5

Thoracic Wall Blood Supply Overview

Answer 5

• Intercostal vessels (anastomose with one another to form vessel arc)
  
  • 9 Anterior Intercostal Vessels
  • 11 Posterior Intercostal Vessels (more as a result of floating ribs)

Question 6

Internal Thoracic Artery

Answer 6

• Branch of subclavian a.
• Runs along the lateral sternum
• Branches:
  
  • First 6 anterior intercostal aa.
  • Musculophrenic a. (follows line of ribcage)
    
    • 7-9th intercostal aa.
  • Superior Epigastric a.
    
    • Continuation of internal thoracic a.
    • Anastomoses with inferior epigastric a.

Question 7

Posterior Intercostal Arteries

Answer 7

• Superior Intercostal Artery
  
  • ​Gives rise to 1st and 2nd posterior intercostal aa.
• Descending Thoracic Aorta
  
  • ​Gives rise to 3rd-11th posterior intercostal aa.

Posterior intercostal aa. give rise to radicular aa. to inferior spinal cord

Question 8

Veins of Thoracic Wall

Answer 8

• Anterior intercostal vv. drain into internal thoracic v.
• Posterior intercostal vv. drain into:
  
  • Azygos v. (right side)
  • Hemiazygous v. (left side)

Question 9

Boundaries of the Thorax

Answer 9

• Boundaries:
  
  • Superior Thoracic Aperture
  • Diaphgram
  • Sternum/Costal Cartilages
  • Thoracic Vertebral Bodies
• Central mediastinum
• Lateral pleural cavities

Question 10

Thoracic Diaphgram

Answer 10

• Separates thorax and abdomen
• Muscular and tendinous components
• Primary Muscle of Respiration

Openings:

• Aortic Opening (T12)
  
  • ​Descending Aorta
  • Thoracic Duct
  • Azygos Vein
• Esophageal Opening (T10)
  
  • ​Esophagus
  • Left and right vagus n.
• Caval Opening (T8)
  
  • ​Inferior vena cava

Innervation:

• L/R Phrenic nn. (C3, C4, C5)

Question 11

Movements of Respiration

Answer 11

Inspiration:

• Expand thoracic cavity in all three dimensions
  
  • Superior to Inferior: Diaphgram
    
    • Moves from dome shape to flat to increase space in thoracic cavity
  • Laterally: Ribs
  • Anterior to Posterior: Sternum

Expiration:

• Compress thoracic cavity
  
  • ​Superior to Inferior: Diaphragm
  • Laterally: Ribs
  • Anterior to Posterior: Sternum

Question 12

Flail Chest

Answer 12

• Multiple rib fractures in multiple places produce separate wall segment
• Will show paradoxical breathing movements (opposite of regular breathing movements)

Question 13

Pleural Cavities

Answer 13

Pleura: a serous “sac” that consists of 2 continuous membranes

• Parietal Pleura: lines the thoracic wall
  
  • Blood Supply: intercostal vessels
  • Innervation: intercostal nerves
• Visceral Pleura: covers the lung
  
  • Blood Supply: pulmonary and bronchial vessels
  • Innervation: autonomic nervous system

Pleural Cavity:

• Between parietal and visceral pleura “potential space”
• Contains serous fluid

Question 14

Pleural Effusion

Answer 14

• Fluid inside pleural cavity
• Use thoracocentesis to remove fluid (above rib)

Question 15

Lungs

Answer 15

Right Lung

• 3 Lobes (Superior, Middle, Inferior)
• Separated by horizontal (b/w superior and middle) and oblique fissures (b/w middle and inferior)

Left Lung

• 2 Lobes (Superior and Inferior)
• Separated by oblique fissure
• Lingula is homologous to middle lobe of R lung (doesn’t develop due to heart)

Question 16

Surfaces of Lungs

Answer 16

• Costal (in contact with ribs)
• Diaphragmatic (in contact with diaphragm)
• Mediastinal (in contact with mediastinum)

Costadiaphragmatic Recess**

Costamediastinal Recess**

**Where fluid can accumuluate. Location of thoracocentesis

Question 17

Conducting Portion of Respiratory System

Answer 17

• Larger tube, passageways
• Transport respiratory gases
• No gas exchange occurs

1. Trachea
2. Left and Right Primary Bronchi (one to each lung)
3. Lobar Bronchi (one to each lobe)
4. Segmental Bronchi (one to each bronchopulmonary segment)
5. Bronchi
6. Bronchioles
7. Terminal Bronchioles

Question 18

Trachea

Answer 18

• Connects to Larynx Superiorly
• Travels from the neck into thorax
• Splits into left/right primary bronchi at Carina
• C-Shaped rings of hyaline cartilage

Question 19

Primary Bronchi

Answer 19

• Left and right
  
  • One goes to each lung
  • Irregular plates of cartilage
  • Divide into secondary bronchi after entering lung

Question 20

Lobar Bronchi

Answer 20

• Go to one lobe each
• Cartilage plates

Question 21

Segmental Bronchi

Answer 21

• Each supply one bronchopulmonary segment of the lung
  
  • Each segment supplied by own tertiary bronchi, branch of pulmonary a., v., lymphatic vessels and autonomic nerves
  • Each surrounded by CT
• Have some cartilage
• Divide into smaller bronchi, which divide into smaller bronchioles (no cartilage)

Question 22

Respiratory Portion of Respiratory System

Answer 22

• Smallest tubes and air sacs
  
  • ​Alveoli
• Site of gas exchange

Question 23

Respiratory Diverticulum

Answer 23

• In earyl 4th week, ventral projection occurs off of the foregut (pharynx) called the respiratory diverticulum
  
  • ​Endoderm
• Esophagotracheal septum forms dividing future trachea from foregut

Question 24

Tracheoesophageal Fistula

Answer 24

• Abnormal communication b/w trachea and esophagus

Esophageal Atresia:

• Where esophagus ends in blind pouch
• Prenatal indicator: polyhydramnios (too much amniotic fluid, normally the fetal circulation requires “swallowing” this fluid)

Question 25

Embryology of Respiratory System

Answer 25

• Late 4th Week: lung bud bifurcates, divides into right and left primary bronchial buds
• 5th Week: primary bronchial buds branch into secondary bronchial buds
• Weeks 6-16: more branching
  
  • By week 16, terminal bronchioles formed and conducting portion is complete
• Weeks 16-28:
  
  • terminal bronchioles divide into respiratory bronchioles
• Weeks 28-Birth:
  
  • ​Primitive Alveoli form
  • Surfactant produced (lack of leads to respiratory distress syndrome, rapid, labored breathing)
• Birth to 8 Years:
  
  • ​More alveoli form

Question 26

Lung Vascular Supply

Answer 26

• Pulmonary System:
  
  • ​Arteries and veins that transport blood to/from lungs for reoxygenation
• Bronchial System:
  
  • Supply bronchi and larger bronchioles
  • 3-4 Bronchial Arteries branch from descending thoracic aorita
  • Bronchial Veins: drain into azygos vein or accesory hemizygos vein; sometimes into pulmonary veins

Question 27

Innervation of Lungs

Answer 27

• Supplied soley by Autonomic Nervous System
  
  • Pulmonary Plexus:
    
    • ​Sympathetic Axons
      
      • ​T1-T5
      • Bronchodilation
    • Parasympathetic Axons
      
      • ​Vagus CN X
      • Bronchoconstriction

Question 28

Lung Lymphatics

Answer 28

• Lymph from bronchopulmonary lymph nodes goes to:
  
  • Tracheobronchial lymph nodes (near carina), then to:
    
    • Left/Right Bronchomediastinal Lymph Trunks:
      
      • Right Lymphatic Duct** or **Thoracic Duct