4. Mediastinum + Heart I

Question 1

Mediastinum (def)

Answer 1

Midline region between R and L pleural cavities

Houses all thoracic organs except lungs

Question 2

Mediastinum (borders, plane)

Answer 2

Superior: superior thoracic aperture

Inferior: diaphragm

Divided into superior and inferior mediastinum by horizontal plane through sternal angle

Question 3

Superior Thoracic Aperture

Answer 3

Ring of bones

T1 vertebrae, Rib 1, Manubrium

Question 4

Thymus

Answer 4

Lymphoid organ

Important in development and maintenance of immune system

Gradual involution: shrinks and replaced with fat

Question 5

Thymus (location)

Answer 5

Posterior to manubrium, body

Anterior to pericardium

Question 6

Pericardium

Answer 6

AKA Pericardial Sac

Fiberoserous membrane surrounding heart, roots of great vessels

Question 7

Phrenic Nerves

Answer 7

Motor: diaphragm

Sensory: diaphragm, parietal pleura, fibrous pericardium, parietal layer of serous pericardium

Question 8

Pericardium (layers)

Answer 8

Fibrous
Parietal Serous
Visceral Serous

Question 9

Fibrous Pericardium

Answer 9

Tough

External layer

Inelastic (prevents heart from overfilling)

Attached to central tendon of diaphragm

Question 10

Serous Pericardium

Answer 10

Parietal lines fibrous pericardium

Visceral lines heart

Continuous w/ each other

Question 11

Pericardial Cavity

Answer 11

Potential space between parietal and visceral layers of serous pericardium

Contains serous fluid

Question 12

Pericarditis

Answer 12

Inflammation of serous pericardium

Leads to roughened surfaces and pericardial friction

Auscultation sign: fabric rubbing together

Question 13

Cardiac Tamponade

Answer 13

Accumulation of fluid in pericardial cavity

This leads to compression and restriction of heart’s ability to fill to capacity

Question 14

Pericardiocentesis

Answer 14

Drains fluids from pericardial cavity

Need to avoid lungs

1. intercostal nerve block
2. subxiphoid approach or parasternal approach

Question 15

Subxiphoid Approach

Answer 15

Insert needle to the left of the xiphoid process, directly superiorly deep to costal margin

Question 16

Parasternal Approach

Answer 16

Insert needle to the left of the sternum in the left 5th or 6th intercostal space – cardiac notch!!

Question 17

Heart Chambers

Answer 17

Right Atrium
Left Atrium
Right Ventricle
Left Ventricle

Question 18

Heart Chamber (orientation)

Answer 18

R Ventricle: anterior

L Atrium: posterior

Question 19

Borders of the Heart

Answer 19

Superior: B atria
Inferior: L ventricle
Left: L ventricle
Right: R atrium

Question 20

Apex of the Heart

Answer 20

Look at a picture

Directed anteroinferiorly and to the left

Formed by L ventricle

Question 21

Base of the Heart

Answer 21

Look at a picture

Directed posteriorly

Formed by L atrium

Question 22

Great Vessels (veins)

Answer 22

Look at a picture

Internal jugular veins
Subclavian veins
Brachiocephalic veins
Superior Vena Cava (SVC)

Question 23

Brachiocephalic Veins

Answer 23

L is longer than R because it must cross midline to reach SVC

Question 24

Superior Vena Cava

Answer 24

returns oxygen poor blood to R atrium from structures superior to diaphragm (except heart)

Question 25

Inferior Vena Cava

Answer 25

returns oxygen poor blood to R atrium from structures inferior to diaphragm

Question 26

Great Vessels (Aorta)

Answer 26

Ascending Aorta (emerges from L ventricle) Arch of Aorta Descending (Thoracic) Aorta Name changes at sternal angle

Question 27

Great Vessels (Arch of the Aorta)

Answer 27

Brachiocephalic Trunk (R Subclavian, R Common Carotid) L Common Carotid L Subclavian

Question 28

Transverse Pericardial Sinus

Answer 28

Posterior to aorta and pulmonary trunk Good for ligation - allows control of arterial outflow

Question 29

Vagus Nerve

Answer 29

CN X Parasympathetic innervation Slows down heart rate, reduces force of contractions

Question 30

Vagus Nerve (pathway)

Answer 30

Pre cell bodies: brain Pre fiber: vagus nerve Post cell bodies: heart Post fiber: heart

Question 31

Right Recurrent Laryngeal Nerve

Answer 31

Branch of Vagus Courses posterior to R subclavian artery - makes a U turn back up to larynx Contributes to cardiac plexus, R pulmonary plexus, esophageal plexus

Question 32

Left Recurrent Laryngeal Nerve

Answer 32

Branch of Vagus Courses under arch of aorta - makes a U turn in mediastinum back up to larynx Contributes to cardiac plexus, esophageal plexus Clinical significance: aneurysm of aortic arch/enlargement of lymph nodes compresses nerve -> hoarseness of voice

Question 33

Sympathetic Innervation

Answer 33

Increases heart rate ``` Lateral horn Ventral root Spinal nerve Ventral ramus White ramus communicans Sympathetic trunk Paravertebral ganglia (upper thoracic, cervical) Cardiac nerves Heart ```

Question 34

Cardiac Nerves

Answer 34

Arise from upper thoracic and cervical sympathetic trunk

Question 35

Referred Cardiac Pain

Answer 35

Visceral sensory fibers follow pathway of sympathetic nerves Visceral pain (normally vague) misinterpreted as somatic pain (sharp)