gross- OSCE III (heart, mediastinum)

Question 1

contents of the superior mediastinum imp to know

Answer 1

mnemonic: BATS TENT

B: brachiocephalic veins
A: arch of aorta
T: thymus
S: superior vena cava
T: trachea
E: Esophagus
N: nerves (vagus & phrenic, left recurrent laryngeal nerve)
T: thoracic duct

Question 2

boundaries of the entire mediastinum

Answer 2

area between the sternum, the two pleural cavities (surround the lungs) and vertebral column

is movable partition that extends superiorly to root of neck and inferiorly to diaphragm

Question 3

how is the mediastinum divided into superior and inferior?

Answer 3

by an imaginary plane that goes across from the sternal angle anteriorly (at the border b/w the rest of sternum & manubrium sterni) to the 4th thoracic vertebrae posteriorly

Question 4

the inferior mediastinum is further divided into what & based off what?

Answer 4

further divided based off pericardium (heart)

area in front of heart (anterior) = anterior mediastinum

area that contains the heart = middle mediastinum

area behind the heart (posterior) = posterior mediastinum

Question 5

contents of the inferior mediastinum from anterior to posterior

Answer 5

1. thymus: in children (later kinda just shrinks away)
2. phrenic nerve
3. heart
4. vagus nerve (the nerves are bounded both front and back of heart- vagus is on the back)
5. Esophagus
6. Descending aorta

this is from the chart on the slides

Question 6

content of the middle mediastinum

Answer 6

• heart
• pericardium
• ascending aorta
• pulmonary trunk & branches
• superior vena cava (here & in superior both)
• phrenic nerve

Question 7

clinical correlates: deflection of the mediastinum

Answer 7

mediastinum is actually very mobile in living humans, but in cadavers it is hard bc of preserving fluids

deflection of mediastinum: mediastinum (including contents- trachea & heart too) shifts to opposite side due to increased thoracic pressure
- can be caused by many things including pneumothorax (air enters the pleural cavity and lung collapses)

Question 8

clinical correlates: mediastinitis

Answer 8

structures of mediastinum embedded in connective tissue that is continuous w/ root of neck

so possible for an infection to spread rapidly into the thorax producing mediastinitis

• also caused by penetrating wounds to the chest involving esophagus

Question 9

clinical correlates: mediastinal tumors & cysts (their effects)

Answer 9

• tumor of left lung can spread rapidly to involve mediastinal lymph nodes which can enlarge & compress left recurrent laryngeal nerve
• expanding cyst can also partially occlude the superior vena cava = severe congestion of veins of upper part of body

Question 10

clinical correlates: mediastinoscopy

Answer 10

diagnostic procedure by which specimens of tracheobronchial lymph nodes are obtained without opening the pleural cavities

• done by small incision made on the base of neck and superior mediastinum is explored
• used to determine diagnosis & degree of spread of carcinoma of bronchus

Question 11

What does the pulmonary trunk do?

Answer 11

Takes deoxygenated blood from the right ventricle to the lungs to get oxygenated

Question 12

Which artery do most MI’s occur in?

Answer 12

anterior interventricular artery (left anterior descending)

because supplies a good chunk of muscles (supplies anterior walls of ventricles on the left and right and the anterior wall of interventricular septum)

Question 13

What does the marginal artery supply?

Answer 13

Lateral walls of right ventricle

Question 14

What vein runs alongside right marginal artery?

Answer 14

Small cardiac vein

Question 15

Anastomosis around heart

Answer 15

• Circumflex artery with posterior interventricular artery
• marginal artery with posterior interventricular artery
• circumflex artery with left anterior descending artery
• marginal artery with left anterior descending artery

do show anastomosis but not enough to actually do anything in a life or death situation

Question 16

where does the aorta exit from and what does it provide?

Answer 16

exits from left ventricle

provides oxygenated blood to the body

Question 17

semilunar valves of heart

Answer 17

semilunar name comes from their half-moon shape (it doesnt even look like a half moon lowk more like a peace sign

2 semilunar valves - located at the exits of the ventricles

1. Aortic valve: located b/w left ventricle & aorta

2. Pulmonary (pulmonic) valve: located b/w right ventricle & pulmonary trunk (which branches into pulmonary arteries)

function: open during systole (contraction) to let blood out & close during diastole (relaxation) to prevent back flow of blood

Question 18

location of the pericardium

Answer 18

lies within the middle mediastinum

posterior to the body of the sternum

from 2nd to 6th costal cartilage

anterior to T5-T8 (thoracic vertebrae)

Question 19

pericardium + function

Answer 19

fibroserous sac that encloses the heart & great vessels - has 2 layers (serous & fibrous)

function: restricts excessive movement of the heart & provides well lubricated environment (absorbs friction)

Question 20

2 layers of the pericardium: fibrous pericardium

Answer 20

fibrous pericardium: strong, fibrous, outer layer of the sac

• attaches firmly below to central tendon of diaphragm (inseparable from diaphragm), fibrous layer sticks to diaphragm at base of heart
• attaches to sternum by sternopericardial ligaments
• fuses with outer coats of the great blood vessels passing through it (aorta, pulmonary trunk, superior/inferior vena cava, & pulmonary veins)

Question 21

2 layers of the pericardium: serous pericardium (2 layers + pericardial cavity)

Answer 21

inner layer of pericardium that lines the fibrous pericardium (is behind it)

divided further into 2 layers-

parietal layer: outer layer, directly lines the fibrous pericardium

visceral layer (aka epicardium): closely lines superficial surface of heart
- this layer cannot be removed & its what makes the heart shiny

space between these 2 layers is called pericardial cavity and usually contains a small amount of pericardial fluid (acts as lubricant to facilitate movements of the heart)

Question 22

pericardial sinuses (fav of anatomy dept)

Answer 22

spaces on posterior side of heart that are formed by reflection (folding back) of serous pericardium around great vessels (creates spaces) - are extensions of pericardial cavity, not separate compartments

oblique sinus: runs along long axis of heart, from apex to ascending aorta

transverse sinus: relatively short horizontal space below/around the pulmonary trunk & ascending aorta

pericardial sinus formed as consequence of way heart folds during development

clinical significance is through these is how surgeons approached large vessels

Question 23

nerve supply of pericardium

Answer 23

phrenic nerve (C3-C5): innervates fibrous pericardium & parietal later of serous pericardium

autonomic nerves (sympathetic + vagus nerves): innervate visceral layer of serous pericardium (epicardium)

Question 24

pericardium clinical conditions: pericarditis leading to cardiac tamponade, pericardial friction or rub, constrictive pericarditis, paracentesis

Answer 24

pericarditis: inflammation of the pericardium
cardiac tamponade: excessive pericardial fluid accumulates in the pericardial cavity leading to compression → interferes w/ filling of the heart during diastole → reduced stroke volume & cardiac output

pericardial friction rub: roughening of visceral & parietal layers of serous pericardium by inflammatory exudate (fluid that leaks out) in acute pericarditis
- can be felt on palpitation and heard through stethoscope

constrictive pericarditis: occurs when fibrous pericardium becomes too rigid because of inflammation
- resistance to movements of the heart and blood flow (mimics heart failure)

Paracentesis: procedure to drain fluid from the pericardial cavity using a needle
- needle inserted below xiphoid process in an upward & backward direction at an angle 45º to the skin
- pleura and lung are not damaged

Question 25

atrioventricular valves

Answer 25

separate atria from ventricles **tricuspid valve**: located b/w right atrium & right ventricle **mitral valve (bicuspid valve)**: between left atrium & left ventricle

Question 26

function of atria & ventricles + function of the 2 functional circuits of heart

Answer 26

**atria**: receive venous blood, pump only to the ventricles **ventricles**: pump blood out of the heart *2 functional circuits: right and left hearts* **right heart = pulmonary circuit**: made of right atrium & ventricle, pumps blood to the lungs and back against low peripheral resistance **left heart = systemic circulation**: left atrium & ventricle, pumps blood through the body against high peripheral resistance

Question 27

which ventricle forms apex of heart?

Answer 27

left ventricle

Question 28

surfaces of the heart (what they're formed by) + apex

Answer 28

**sterno-costal (anterior)**: mostly right atrium + right ventricle - *front (behind sternum and ribs)* **diaphragmatic (inferior)**: left ventricle (main) + part of right ventricle - *downward, rests on diaphragm* **base (posterior)**: Left atrium (main) + part of right atrium - *backward & towards spine* **apex**: points downward, forward, and to the left, located in *5th intercostal space - midclavicular line*

Question 29

pulmonary veins

Answer 29

**2 pulmonary veins** from each lung (so 4 total) carry **oxygenated blood** to the **left atrium** of the heart

Question 30

The inferior hemiazygos vein crosses to join the azygos vein at which vertebral level?

Answer 30

T8

Question 31

At which vertebral level does the azygos vein arch over the root of the right lung to join the superior vena cava?

Answer 31

T5 vertebra

Question 32

What vein in the superior mediastinum passes anterior to the major arteries and posterior to the manubrium sterni?

Answer 32

left brachiocephalic vein

Question 33

large thoracic veins: **brachiocephalic veins** (function, formation, shape)

Answer 33

**2 large veins** (right and left) that **drain blood from the head, neck, upper limbs, and upper chest** **formed by**: union of subclavian & internal jugular vein on each side **shape**: - right BCV is short and vertical (*curves and goes down more*) - left BCV is longer and runs obliquely (diagonally) from the left to the right **left BVC**: passes *in front of major arteries* (like brachiocephalic trunk, left common carotid, and left subclavian arteries) & lies behind the *manubrium of the sternum*

Question 34

large thoracic veins: **superior vena cava (SVC)** (formation, function, relationship to azygous vein)

Answer 34

**formed by**: 2 brachiocephalic veins join to form the superior vena cava, behind the lower border of the 1st right costal cartilage **function**: drains all venous blood from the upper half of the body (neck, head, & both upper limbs) into the right atrium of the heart **azygous vein** joins it from behind (**posteriorly**) right before it enters into the pericardium

Question 35

large thoracic veins: **azygos veins** (where they drain blood from, consist of, function)

Answer 35

are a **collateral venous system** on the posterior thoracic wall that **connect the SVC and IVC** (important in case of blockage) consists of: azygos vein, inferior hemiazygos vein, & superior hemiazygous vein **drain blood from**: -posterior parts of intercostal spaces - posterior abdominal wall - the pericardium - diaphragm - bronchi - esophagus

Question 36

**main azygos vein** (origin, pathway, tributaries)

Answer 36

originates from union of **right ascending lumbar vein & right subcostal vein** (from abdomen) **pathway**: ascends through aortic opening in diaphragm on right side of aorta up to T5 level → arches forward above root of right lung to *empty into posterior surface of superior vena cava* **tributaries** (*vein that empties into larger vein*): - 8 lower right intercostal veins - right superior intercostal vein - superior & inferior hemiazygos veins - mediastinal veins

Question 37

**inferior hemiazygos vein** (origin, pathway, tributaries)

Answer 37

originates from union of **left ascending lumbar vein & left subcostal vein** in the abdomen **pathway**: ascends on left side of vertebrae and crosses over to right to join azygos vein at **T8 LEVEL** **tributaries**: - lower left intercostal veins - mediastinal veins

Question 38

**superior hemiazygos vein (aka accessory hemiazygos)** (origin + when joins main azygos vein)

Answer 38

formed by union of **left superior intercostal vein & 4-8th intercostal veins** joins by **azygos vein** at level of **T7 vertebra**

Question 39

when do the inferior/superior hemiazygos veins join into the main azygos vein

Answer 39

- **Inferior hemiazygos** → joins azygos at **T8** - **Superior hemiazygos** → joins azygos at **T7** - Azygos arches forward at **T5** to drain into SVC

Question 40

clinical: **azygos veins & caval obstruction**

Answer 40

in case of **obstruction of inferior or superior vena cava,** azygos system provides an **alternative pathway** for the return of venous blood to **right atrium of heart** this is possible b/c these veins and their tributaries **connect** the superior & inferior vena cava

Question 41

3 main lymphatics trunks in the thorax

Answer 41

*right and left side for all of them* **jugular trunk**: drains lymph from head and neck **subclavian trunk**: drains lymph from upper limb & superficial thoracic wall (via axillary nodes) **bronchomediastinal trunk**: drains deep thoracic structures including: *lungs, trachea, heart, esophagus, mediastinum* - all 3 of these that come from right side → drain into **right lymphatic duct** (or directly into venous angle) - all 3 of these coming from left side → drain into the **thoracic duct** **mnemonic**: *Just Some Basic Thoracic Drainage (thoracic duct - left side)*

Question 42

lymph nodes of the thoracic wall

Answer 42

**superficial lymphatics**: drain skin and superficial fascia of chest - drain into **ant. & post. axillary lymph nodes** **deep lymphatics**: drain intercostal spaces & muscles, flow to **internal thoracic lymph nodes** (for anterior part) and **posterior intercostal nodes** (for posterior parts) on left side, lymph passes into the **thoracic duct** on right side, lymph passes into **right bronchomediastinal trunk**

Question 43

mediastinal lymph nodes + clinical significance

Answer 43

many nodes scattered throughout the mediastinum - drain lymph from mediastinal structures and empty into **bronchomediastinal trunks & thoracic duct** *disease/enlargement of these nodes can put pressure/compress on nearby important structures like trachea & superior vena cava*

Question 44

vagus nerve in thorax (course + fibers)

Answer 44

2- right and left and vagus nerves carry **preganglionic parasympathetic fibers** **course in thorax**: **right**: descends in thorax lateral to trachea, medial to terminal part of azygos vein, posterior to root of lung → forms *pulmonary plexus (around bronchi)* and *esophageal plexus (around esophagus)* **left**: descends b/w left common carotid & left subclavian arteries → crosses left side of aortic arch where passes under left phrenic nerve → turns backward behind root of left lung & assists in formation of *pulmonary plexus* → goes towards ant. surface of esophagus to form *esophageal plexus*

Question 45

vagus nerves branches in the thorax

Answer 45

branches: **right & left recurrent laryngeal nerve** (*supply trachea & esophagus + major motor/sensory supply to larynx*) **right recurrent laryngeal nerve**: arises from right vagus in the neck → hooks around *right subclavian artery* → ascends b/w trachea & esophagus **left recurrent laryngeal nerve**: arises from left vagus trunk as nerve crosses arch of aorta → hooks around *ligamentum arteriosum (prenatally ductus arteriosus)* → ascends in groove b/w trachea & esophagus on left side

Question 46

phrenic nerves (origin, supply, branches, course of branches)

Answer 46

arise in neck from **C3, C4, C5** provide **motor & sensory innervation to the diaphragm** (both efferent & afferent fibers) **right phrenic nerve**: descends in thorax along right side of **brachiocephalic vein** & superior vena cava → passes in front of root of **right lung** → runs alongside **right side of pericardium** → descends down **right side of inferior vena cava** to **diaphragm** → terminal branches supply central part of peritoneum **left phrenic nerve**: descends in thoracic along left side of **left subclavian artery** → **crosses left side of aortic arch** and here crosses **over left vagus nerve** → passes in front of root of **left lung** → descends over **surface of pericardium** → terminal branches then pierce the **diaphragm muscle** & supply the central part of the peritoneum

Question 47

clinical: diaphragm paralysis

Answer 47

if **phrenic nerve is damaged** from pressure of malignant tumors in mediastinum was used surgically to crush/section phrenic nerve in the neck as **treatment of lung tuberculosis**

Question 48

sympathetic trunk + branches in the thorax

Answer 48

**sympathetic trunk**: paired bundle of nerve fibers that are located on either side of the vertebral column - part of **autonomic nervous system (sympathetic division)** **branches**: 1. **white rami communicantes**: carry *preganglionic sympathetic fibers from the thoracic spinal nerves → sympathetic trunk* (IN) 2. **gray rami communicantes**: *carry postganglionic fibers from the sympathetic trunk → thoracic spinal nerves* 3. **thoracic splanchnic (visceral) branches**: *carry postganglionic fibers to pulmonary, cardiac, & esophageal plexuses* 4. **abdominal splanchnic (visceral) branches**: there are 3 of them: 1. **Greater splanchnic nerve** (T5–T9) 2. **Lesser splanchnic nerve** (T10–T11) 3. **Least splanchnic nerve** (T12)

Question 49

Which thoracic splanchnic nerve arises from T5–T9 and supplies abdominal organs?

Answer 49

Greater splanchnic nerve.

Question 50

Which nerve passes anterior to the root of the lung — phrenic or vagus?

Answer 50

Phrenic nerve

Question 51

blood supply of thymus

Answer 51

inferior thyroid & internal thoracic arteries

Question 52

blood supply + drainage of esophagus

Answer 52

*split into 3 parts: upper third, middle third, lower third* upper third (*cervical*): **inferior thyroid artery** - veins here drain into: **inferior thyroid veins** middle third (*thoracic*): **esophagyeal branches from the descending thoracic aorta** - veins here drain into: **azygous veins** lower third (*abdominal*): **branches of left gastric artery** - veins here drain into: **left gastric vein**

Question 53

nerve supply of esophagus

Answer 53

supplied by parasympathetic & sympathetic fibers via the **vagi & sympathetic trunks** respectively in lower part of thoracic course, surrounded by **esophageal nerve plexus**

Question 54

relations of thoracic part of esophagus

Answer 54

**anteriorly**: - trachea - left recurrent laryngeal nerve - left principal bronchus, - pericardium (*separates the esophagus from the left atrium*) **posteriorly**: - thoracic vertebrae - the thoracic duct - azygos veins - right posterior intercostal arteries - descending thoracic aorta **right side**: - mediastinal pleura - terminal part of azygos vein **left side**: - left subclavian artery - aortic arch - thoracic duct - mediastinal pleura

Question 55

pulmonary trunk + branches

Answer 55

**pulmonary trunk**: takes deoxygenated blood from right ventricle of heart to lungs - terminates in concavity of aortic arch by dividing into *right and left pulmonary arteries* *branches* **right pulmonary artery**: runs to the right behind ascending aorta & superior vena cava to enter root of right lung **left pulmonary artery**: runs to the left in front of descending aorta to enter root of left lung **ligamentum arteriosum**: fibrous band that connects pulmonary trunk & aorta - remnant of **ductus arteriosum** from fetal life (*connected blood from pulmonary trunk to aorta, bypassing the lungs*) - **left recurrent pharyngeal nerve** hooks around lower border of this ligament

Question 56

clinical: aneurysm of aorta

Answer 56

**aneurysm**: localized abnormal dilation (ballooning) of an artery due to weakness in the wall isn't able to withstand high pressure and can burst