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What are the intercostal muscles?
- 3 intercostal muscles
- 1) external intercostal
- 2) internal intercostal
- 3) innermost intercostal
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What are the characteristics of the external intercostal? Attachment, fiber direction, function, & nerve supply.
- Attachment: lower borders of ribs 1-11 to upper borders of ribs 2-12
- Fibers: run down and forward at the costochondral joint, replaced by external intercostal membrane
- Function: elevate rib cage, inspiration
- Nerve: corresponding intercostal nerves
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What are the characteristics of the internal intercostal?
- attachment: lower margins of ribs, costal cartilages and grooves (same as external).
- fibers: run down and backward, the intercostal membrane is near the vertebrae.
- function: muscle of experation
- nerve: corresponding intercostal nerves
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What are the characteristics of the innermost intercostal muscle?
- It has 3 parts
- 1) innermost intercostal muscle fibers: few fibers between the ribs; mostly membrane.
- 2) subcostalis muscle: found at angle of rib only. attachment: between ribs posteriorly and may cross 1 or 2 ribs and attach to the 3rd rib. function: expiration.
- 3) sternocostalis muscle (transversus thoracis): found near sternum only. attachment: back of xiphoid process and sternum, inserts in the costal cartilages. nerve: interostal nerves. function: expiration
fibers: run down and backward
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Where is the posterior intercostal neurovascular bundle located?
between internal intercostal muscles and the innermost interostal muscles.
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Where is the subcostal space located?
space below the 12th rib
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How many intercostal spaces are there?
11
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Where is the nipple of the breast located?
Intercostal space 4
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Arterial blood supply of the thoracic cage (4)
- 1: Internal thoracic artery branched from subclavian artery.
- 2: highest intercostal artery branched from costocervical
- 3: posterior intercostal artery branched directly from thoracic aorta
- 4: subcostal artery branched directly from thoracic aiorta
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What supplies the arterial anterior aspect of the intercostal spaces?
Internal thoracic artery branched from subclavian artery.
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What supplies the arterial posterior aspect of the intercostal spaces? Differentiate between spaces 1, 2-11, and 12
- 1: highest intercostal artery
- 2-11: posterior intercostal arteries
- 12: subcostal artery
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Venous blood supply of the thoracic cage: Anterior aspect
internal thoracic vein drains into the braciocephalic vein
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venous blood supply of the thoracic cage: posterior aspect
supplied by the azygous system
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what veins supply the posterior right side of the thoracic cage?
- 1 intercostal space: highest intercostal vein drains into the brachiocephalic vein.
- 2 and 3 intercostal space: joins higher intercostal , drains into azygos
- 4-11 intercostal space: intercostal veins drain directly into the azygous vein.
- 12 intercostal space: subcostal vein drains directly into azygous vein.
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Where does the azygous vein drain?
into the superior vena cava
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what veins supply the posterior left side of the thoracic cage?
- 1 intercostal space: highest intercostal vein drains into brachiocephalic vein
- 2-4 intercostal space: intercostal veins join to give accessory hemiazygous vein.
- 5-11 intercostal space: intercostal veins and the subcostal vein (12th vein) join together to give the hemiazygous vein.
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What 2 paths can the accessory hemiazygous and hemiazygous veins take to drain?
- 1: they cross to right side independantly and drain into azygous vein
- 2: they join as a single unit and drain into azygous vein
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Where else may the accessory hemiazygous vein drain?
into the brachiocephalic vein
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how many layers of penetration are in the mid-axillary line?
12
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what are the layers of penetration?
- 1: skin
- 2: superficial fascia
- 3: deep fascia
- 4: serratus anterior
- 5: external intercostal muscle
- 6: internal intercostal muscle
- 7: innermost intercostal muscle
- 8: endothoracic fascia
- 9: parietal pleura
- 10: pleural cavity
- 11: visceral pleura
- 12: lungs
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What is the function of the endothoracic fascia?
prevent parietal pleura which surrounds the lungs from rubbing against the innermost intercostal muscles.
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What is thickening of the endothoracic fascia called?
thickening over the apex of the lung aka sibson's fascia
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Spaces of the thoracic cavity
- 1: 2 pleural cavities that are separate enclosed spaces from one another with pleural fluid.
- 2: mediastinum
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what are the structures inside the thoracic cavity
- 1:heart
- 2: lungs
- 3: trachea
- 4: esophagus
- 5: vagus and phrenic nerves
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what are the pleural reflections?
- 1: pleural cavity
- 2: pleaural fluid
- 3: pleural membranes
- 4: removal of fluid
- 5: parietal pleura
- 6: visceral pleura
- 7: cupola
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what is the pleural cavity?
enclosed space that includes fluid
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what is the function of pleural fluid?
minimize friction between parietal pleura and visceral pleura
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pleural membranes do not cover?
root of the lung
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how to remove pleura fluid?
with mid-axillary tap
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where is the parietal pleura?
lines the muscle wall
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where is the visceral pleura?
covering organs
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what is the cupola and where is it?
area of parietal pleura, it is located on the apex of the lung in the thoracic inlet
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what are the pleural recesses?
- 1: costo diaphragmatic recess
- 2: costo mediastinal recess
- 3: costo vertebral recess
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where is the costo diaphragmatic recess?
junction of costal and diaphragmatic parietal pleura near mid axillary line.
pleural cavity tap can be done here in intercostal space 9
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What is the function of recesses?
allow expansion of lung during inspiration
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what arteries supply the parietal pleura?
intercostal and internal thoracic arteries
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what artery supplies the visceral pleura?
bronchial artery which supplies the lung
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what nerves supply the parietal pleura?
intercostal nerves T1-T11 subcostal and phrenic nerve (Cn 3,4,5)
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function of the phrenic nerve?
motor nerve to the diaphragm
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what nerves supply the visceral pleura?
none. insensitive to pain, no sensory innervation
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Where is the mediastinum located?
medial region between the 2 pleural cavities.
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what does the mediastinum contain?
all structures in chest except lungs and pleural sacs
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what is the sternal angle of the mediastinum?
T4 level. line through sternal angle divides mediastinum into superior and inferior sections.
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what does the superior mediastinum contain?
arch of aorta and branches
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what are the branches of the aorta of the superior mediastinum?
- 1: brachiocephalic trunk
- 2: left common carotid artery
- 3: left subclavian vein
- 4: brachiocephalic vein
- 5: superior vena cava
- 6: thymus (children only)
- 7: esophagus
- 8: trachea
- 9: thoracic duct
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how is the brachiocephalic vein formed in the mediastinum?
joining of subclavian vein and internal jugular vein
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how is the superior vena cava formed?
joining right and left brachiocephalic veins
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what are the compartments of the inferior mediastinum?
- 1: anterior mediastinum
- 2: middle mediastinum
- 3: posterior mediastinum
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location of the anterior mediastinum?
posterior surface of the sternum to anterior surface of pericardial sac
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what is the anterior mediastinum made up of?
- 1: fatty tissue
- 2: thymus (infants)
- 3: lymph nodes
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what is the middle mediastinum made up of?
- 1: heart
- 2: pericardium
- 3: main bronchi
- 4: great vessels
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where is the posterior mediastinum located?
posterior to pericardial sac and diaphragm and anterior to thoracic vertebrae 5-12
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what is the posterior mediastinum made up of?
- 1: esophagus
- 2: thoracic aorta
- 3: azygos system
- 4: thoracic duct
- 5: vagus nerve
- 6: splanchnics nerves from sympathetic chain
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what structure is not in the posterior mediastinum?
trachea
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what does a mediastinoscopy involve?
removal of tissue from anterior and superior mediastinum to examine the lymph nodes. The inciscion is made at the jugular notch.
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physical characteristics of the trachea
- 15-20 "C" bars of cartilage
- 9-15 cm long and 2.5 cm in diameter
- begins at the neck at cv 6
- biforcates at sternal angle (tv 4) into right and left main bronchi
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what are structures anterior to trachea?
- sternum
- thymus
- arch of aorta
- origins of brachiocephalic and left common carotid arteries
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what are structures posterior to trachea?
- esophagus: right side= azygos vein and right vagus nerve
- esophagus: left side = arch of aorta, left common carotid, left subclavian artery, left vagus nerve
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what does trachea do just before it biforcates?
at the sternal angle, it deviates towards the right because of the heart.
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branches of the trachea
- right main bronchus: wider and shorter it is more vertical than the left. gives off superior lobar bronchus before entering the hilum then divides further into middle and inferior lobar bronchi.
- left main bronchus: narrower and longer it is more horizontal than the right. passes interior to the esophagus. divides in the hilum intol superior and inferior lobar bronchii
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what arteries supply the trachea?
- superior thyroid artery
- inferior thyroid artery
- bronchial arteries
- internal thoracic artery
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what nerves supply the trachea?
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what are the anatomical features of the lungs?
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what surfaces make up the base of the lung?
- costal
- medial
- diaphragmatic
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