The Middle Mediastinum:The Middle Mediastinum:

Pericardium & HeartPericardium & Heart

MediastinumMediastinum

• The space between 2 lungs

Sup.: thoracic inlet

Inf.: diaphragm

Ant.: sternum & 2-6 CC

Post.: thoracic vertebrae

By Imaginary line By Imaginary line superior & inferior mediastina superior & inferior mediastina

DivisionsDivisions

Superior: Ant.: manubrium

Post.: T1-T4

Sup.: ?? Inf.: ??

Inferior:Ant.: sternal body

Post.: T5-T12

Sup.: ?? Inf.: ??

2 divisions by imaginary line: sternal angle T4-T5

3 parts:

Ant.: from sternum heart covering

(pericardium)

Middle: heart & pericardium

Post.: post. to heart

Inferior MediastinumInferior Mediastinum

PericardiumPericardium

PericardiumPericardium

• Covering fibroserous sac of 2 layers of tissues that encloses the heart

• Outer: fibrous (fibrous pericardium)

• Inner: serous (serous pericardium)

• Fxn.: 1. Protection 2. Lubrication (friction)

Fibrous PericardiumFibrous Pericardium

• Strong single layer

• Attached:

Ant.: sternum (sternopericardial lig.)

Inf.: diaphragm (central tendon)

Sup.: fuse to great vessels (t. adventitia)

• Sensory innervations by phrenic nerve

(very sensitive)

What are the cervical spinal segments of the phrenic nerve origin?

Serous PericardiumSerous Pericardium

• 2 layers of mesothelial cells that are continuous with each other

• Outer (Parietal):

lines over fibrous pericardium

reflects around the roots of large vessels

to become continuous with

• Inner (Visceral):

closely attached to the heart

Epicardium (outer heart layer)

• Sup & Inf mediastinum

• Inf middle:

pericardium & heart

Fibrous: Protection

Serous: Lubrication

visceral epicardium

ReviewReview

HeartHeartRead Your Textbook For DetailsRead Your Textbook For Details

• 3 layers

• 4 chambers

• 3 borders

(examining X-ray)

• 3 surfaces

• Apex & Root

Heart SurfacesHeart Surfaces

1. Anterior (sternocostal):

Rt. Atrium, Rt. V., Lf. V., ant. intervent. groove

2. Inferior (diaphragmatic):

Rt. & Lf. V’s, & post. interventricular groove

3. Posterior:

Lf. Atrium

Base of the heart

4. Apex:

part of Lf. V. (lf. 5th intercostal space, 9 cm from ??)

5. Root:

origin of great vessels

(aorta, pulmonary trunk, SVC)

Inferior Surface

Posterior Surface

Anterior Surface

Site for posterior surface of the heart (Base)

Site for inferior surface of the heart (Diaphragmatic)

Right AtriumRight Atrium

- Receives deO2 bld. From the body

- Forms Rt. Border of the heart

- Composed of:smooth walled chamber &rough out pouch (auricle)

Rough = pectinate muscle

- Border between:crista terminalis

Outside:sulcus terminalis

- Atrial septum (fetal remnants): Fossa ovalis Anulus ovalis

Read Your Textbook For More Details

Openings of Rt. AtriumOpenings of Rt. Atrium1. SVC:

bld. from upper body

2. IVC:

bld. From lower body / larger

3. A-V orifice:

Ant. to IVC

Guarded by tricuspid valve

4. Coronary Sinus:

Between IVC & A-V orifice

Bld form heart wall

5. ant. cardiac veins

Rt. VentricleRt. Ventricle

Crescent shaped from inside (cross-section)

3 muscular projections:

1. Papillary muscles:

Finger-like projections

Attach the cusps of A-V valve via Chordae tendineae

2. Moderator band:

inf. septal wall base of ant. Papillary muscle

contains nervous bundle to Rt. Ventricular wall

3. Trabeculae carneae:

prominent muscular ridges

Read Your Textbook For More Details

OpeningsOpenings

• A-V orifice:guarded by tricuspid valve

• Pulmonary opening:smooth funnel-shaped wall (infundibulum)

infundibulum = conus arteriosus

guarded by pulmonary valve

Lf. AtriumLf. Atrium• Most of the posterior wall

• Small lf. Auricle (muscular ridges)

• Usually 4 openings for P. V.& 1 for mitral valve

Left VentricleLeft Ventricle

• Wall 3x thicker than Rt. V.

• Circular in cross-section

• 2 large papillary m. (groups)

• Aortic vestibule:

smooth surface inf. to

aortic valve

No moderator bandNo moderator band

Heart PositionHeart Position

• Behind the sternum & slightly to the left

strong sounds = left to the sternum

• Dextrocardia:

The heart is on the right side of the chest

heart sounds = right to the sternum

- 1 in 12,000