Thorax I (Anatomy of the Thorax, Lungs, & Mediastinum) Flashcards
What is the Thoracic Cage composed of?
- 12 thoracic vertebrae
- 10 ribs and costal cartilages
- Sternum
What are the functions of the Thoracic Cage?
- Protects vital organs of thoracic cavity
- Supports pectoral girdle and upper limbs
- Provides attachment sites for muscles
- Resist negative internal pressures generated by the recoil of the lungs
What is the Sternum composed of?
Three fused bones that lie in anterior midline of thorax
A. Manubrium
B. Body
C. Xiphoid process
D. Sternal angle
What does the Manubrium (of the Sternum) articulate with?
Articulates with clavicles and costal cartilages of ribs 1 and 2
What does the Body of the Sternum articulate with?
Articulates with costal cartilages of ribs 2-7
What is the Sternal angle?
- Manubrium meets body
- Vertebral level of T4/5
- Important anatomical landmark
What is apart of the Thoracic Vertebrae?
A. Heart-shaped vertebral body
B. Long spinous process
C. Costal facet of transverse process
D. Superior costal demifacet
E. Inferior costal demifacet
How many rib pairs are there and where do they attach?
12 pairs, all attach posteriorly to thoracic vertebrae
What are the 3 different types of ribs?
- True ribs
- False ribs
- Floating ribs
& Intercoastal space
What are the True ribs?
1-7
* Attach anteriorly to sternum via their costal cartilages
What are the False ribs?
8-10
* Costal cartilages fuse together and join the costal cartilage of rib 7
(don’t have own attachment to sternum)
What are the Floating ribs?
11, 12
* Do not attach to the
sternum
What is the Intercostal space?
space between adjacent ribs
What does a Typical Rib (3-9) include?
- Head
- Neck
- Tubercle
- Costal groove
- Body
- Attachment to costal cartilage
- Costovertebral joint
- Costotransverse joint
What part of a Typical Rib (3-9) articulates with demifacets of vertebral bodies?
head
What part of a Typical Rib (3-9) articulates with transverse process of vertebra?
Tubercle
What are the 2 types of the Thoracic Apertures?
- Superior thoracic aperture (thoracic outlet)
- Inferior thoracic aperture
What is included in the Superior Thoracic Aperture (thoracic outlet)?
- Esophagus
- Trachea
- Vessels and nerves of head and neck
- Vessels of upper limbs
- Apex of lung
What is included in the Inferior Thoracic Aperture?
- Closed off by diaphragm
- Esophagus
- Inferior vena cava
- Aorta
What are the Intercostal Muscles?
- Thin sheets of muscles that connect adjacent ribs
- Close off intercostal spaces
What is the Intercostal Muscles innervation?
intercostal nerves
What is the order of superficial to deep?
- External intercostal muscles
- Internal intercostal muscles
- Innermost intercostals
What are the External Intercostal Muscles?
- Superficial layer, more lateral
- Muscle fibers travel infero-medially
“HANDS IN POCKETS” - ELEVATE ribs during FORCED INSPIRATION
What are the Internal Intercostal Muscles?
- Intermediate layer, more medial
- Muscle fibers travel supero-medially
“HANDS ON CHEST” - DEPRESS ribs during FORCED EXPIRATION
What are the Innermost Intercostal Muscles?
- Deep to internal intercostal muscles
- Muscle fibers travel supero- medially (same as internal)
- Depress ribs during forced expiration
- Neurovascular bundles run between internal and innermost intercostal muscles
What is the Transversus thoracis?
- Group of 4-5 thin muscles on the inner surface of the anterior thoracic wall
- Run from sternum/xyphoid process to ribs
- Weakly depress ribs
(apart of the Innermost Intercostal Muscles)
What is the Diaphragm?
Primary muscle of inspiration
Where does the Diaphragm originate & insert?
Originates from xiphoid process, lumber vertebrae and inferior margin of rib cage
Inserts onto central tendon
Form right and left domes
When diaphragm contracts, domes depress, increases the height of thoracic cavity
What is the Diaphragms innervation?
phrenic nerves
What structures do the openings of the Diaphragm allow structures to pass through?
- CAVAL OPENING for inferior vena cava
- ESOPHAGEAL HIATUS for esophagus
- AORTIC HIATUS for aorta
What is respiration?
Change dimensions of thoracic cavity
→ change intrathoracic pressure
→ move air
What is inspiration?
- Intrathoracic volume ↑
- ↓ Intrathoracic pressure
- Brings air into lungs
Quiet Breathing Inspiration
Diaphragm contracts & descends
↑ Height of thoracic cavity
Forced Breathing Inspiration
Diaphragm contracts
External intercostal and accessory respiratory muscles contract
Elevate ribs and sternum
↑ AP and lateral dimensions
What is expiration?
- Intrathoracic volume ↓
- ↑ Intrathoracic pressure
- Expel air out of lungs
Quiet Breathing Expiration
Diaphragm and other inspiratory muscles relax
Elastic recoil of lungs
↓ Intrathoracic volume
Forced Breathing Expiration
Internal intercoastal and abdominal muscles contract
Depress ribs
↓ AP and lateral dimensions
What is apart of the Arterial Supply to the Thoracic Wall?
- Subclavian a.
- Internal Thoracic a.
- Anterior Intercostal a.
- Posterior Intercostal a.
- Aorta
What is apart of the Venous Drainage of the Thoracic Wall?
- Accessory hemiazygos v.
- Azygos v.
- Posterior intercostal v.
- Hemiazygos v.
- SVC
- Internal thoracic v.
- Anterior intercostal v.
What is the innervation of the Thoracic Wall?
Intercostal nerves
* Anterior rami of T1-T11
* Innervate intercostal muscles
* Cutaneous sensory
Where does the Intercostal Neurovascular Bundle run between?
Run between INTERNAL and INNERMOST intercostal muscles
What is apart of the Thoracic Cavity & what do they contain?
Pulmonary cavities (right and left)
* Contains lungs and pleurae
Mediastinum
* Contains heart, great vessels, trachea, esophagus, thymus
What is the Pleura & its parts?
Serous epithelium with subepithelial connective tissue; 2 continuous parts:
* Parietal pleura (outside layer)
* Visceral pleura
Where does the Parietal Pleura adhere & what are the subdivisions?
Adheres to the inner surface of the wall of pulmonary cavity
Subdivisions
* Costal parietal pleura
* Cervical parietal pleura
* Mediastinal parietal pleura
* Diaphragmatic parietal pleura
What is the innervation of the Parietal Pleura?
intercostal and phrenic nerves
Where does the Visceral Pleura adhere?
- Adheres to LUNG SURFACE
- Continuous with the parietal pleura at the hilum of lungs
What is the innervation of the Visceral Pleura?
sensory fibers accompanying sympathetic fibers
What is the Pleural Cavity?
Potential space between visceral and parietal pleurae
* Left and right pleural cavities are completely separate
What is the Pleural Fluid?
- Secreted by pleurae
- Reduces friction
- Provides surface tension to keep the pleural layers adherent
What is the Pleural recess?
- Pleura cavity between pleural reflection and lung border
What is Pleural Cavity & Respiration?
The negative pressure of the pleural cavity and surface tension of the pleural fluid are crucial for keeping the lung moving with the thoracic wall and diaphragm
What are the lungs?
Within the pulmonary cavities, surrounded by pleural cavities
APEX through the superior thoracic aperture
Both lungs have what?
Oblique fissures but the right lung has a Horizontal fissure as well
What are the root of the lung?
structures that enter and exit the lung
What is the Hilum?
location where structures of the root enter and exit
Where are the Pulmonary arteries?
superior & anterior
heart –> lungs
Where are the Primary bronchi?
central & posterior
air tube
Where are the Pulmonary veins?
inferior & anterior
lungs –> heart
What are the additional root structures at Hilum?
- Bronchial arteries & veins
- Lymph nodes & lymphatic vessels
- Nerves
What is the Trachea?
- Begins at C6 vertebral level, inferior to the cricoid cartilage
- Bifurcates at carina (@T4/T5) into right and left primary bronchi
- Wall contains 16-20 C-shaped cartilaginous rings
- Posteriorly connected by trachealis muscle
What are the Primary Bronchi?
Right primary bronchus
* Shorter, broader,
more vertical
* 3 branches
Left primary bronchus
* Longer, narrower,
more horizontal
* 2 branches
* Inferior to aortic arch, anterior to esophagus and thoracic aorta
What is the Bronchial Tree?
- Primary (1°) bronchus: supply a lung
- Lobar (2°) bronchus: supply a lobe
- Segmental (3°) bronchus: supply a bronchopulmonary segment
What is the Bronchopulmonary Segment?
- Right lung has 10
- Left lung has 8-10
- Each segment is supplied independently by a segmental bronchus and its own pulmonary artery – surgically resectable
What is important about the Bronchial Tree?
loose cartilage plates as they get smaller
What is the Mediastinum & its boundaries?
“Middle space” between pulmonary cavities
Boundaries:
* Superior thoracic
aperture
* Diaphragm
* Pulmonary cavities
* Sternum
* Thoracic vertebrae
What are the different Mediastinum’s?
Superior mediastinum
* Superior to transverse thoracic plane
(sternal angle, T4/T5)
Inferior mediastinum
* Anterior mediastinum
- Between sternum and pericardium
* Middle mediastinum
- Pericardial sac and content
* Posterior mediastinum
- Between pericardium and thoracic vertebrae
What are the main organs in the Mediastinum?
- *Thymus (go away around adolescence - helps mature T cells & then goes away)
- Esophagus
- Heart in pericardium
- Trachea
What are the nerves in the Mediastinum?
- Recurrent laryngeal n.
- Vagus n.
- Phrenic n.
- Recurrent laryngeal n.
- Vagus n.
- Phrenic n.
What is the Phrenic Nerve’s origin & where does it go?
Origin: cervical plexus (C3,4,5) (keeps diaphragm alive!)
Descends ANTERIOR TO THE ROOT OF
THE LUNG
* Between fibrous pericardium and mediastinal parietal pleura
(formed on top of anterior scalene)
What is the Phrenic Nerve’s motor/sensory?
Motor to diaphragm
Sensory from:
* Pericardium
* Parietal pleura (mediastinal, diaphragmatic)
* Parietal peritoneum (inferior surface of diaphragm)
What is the Vagus Nerve (CN X)?
- Descends in the carotid sheath of the neck
- Courses POSTERIOR TO ROOT OF LUNG and along esophagus
- Parasympathetic to autonomic nerve plexuses
- Cardiac
- Pulmonary
- Esophageal
What is the Recurrent Laryngeal Nerve?
A. Right recurrent laryngeal nerve loops under right subclavian artery
B. Left recurrent laryngeal nerve loops under aortic arch
- Motor to most muscles of the larynx
- Sensory from inferior larynx
What is the Sympathetic Trunk?
Sympathetic output originates from spinal cord T1-L2 (cell bodies of preganglionic neurons)
A. Sympathetic ganglion contains cell bodies of postganglionic neurons
B. Sympathetic trunk connects sympathetic ganglia
* Extends superiorly to the neck and inferiorly to the pelvis
C. Splanchnic nerves contain preganglionic neurons to abdomen
What are the Autonomic Nerves in the Mediastinum?
- Vagus n.
- Sympathetic trunk
- Cardiac plexus
- Esophageal plexus
- Pulmonary plexus
- Recurrent larygngeal n.
- Splanchnic n.
What is the innervation of lungs & bronchi?
Sympathetic fibers
* Bronchodilation
* Vasoconstriction
* ↓ Gland secretion
Parasympathetic fibers
* Bronchoconstriction
* Vasodilation
* ↑ Gland secretion
Sensory fibers
* Reflexive: subconscious sensations
associated with reflexes
- Accompany parasympathetic fibers
* Nociceptive: conscious pain in response to injurious stimuli
- Fibers from visceral pleura and bronchi accompany sympathetic fibers
- Fibers from parietal pleura join intercostal and phrenic nerves
What is the Lymphatics in the Mediastinum?
Right lymphatic duct drains into right venous angle
Thoracic duct drains into left venous angle
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