Cardiovascular System:

Putting the Heart into

Histo

Mesothelium

Lecture 9, Slide 1

3 Layers3 LayersEndocardiumEndocardiumMyocardiumMyocardiumEpicardiumEpicardium

L9, S2

Fibrous TrigoneFibrous Trigone Forms the base of Forms the base of

tissue from which tissue from which the valves are the valves are anchoredanchored

Separates atria Separates atria from ventriclesfrom ventricles

Atria and ventricle Atria and ventricle only communicate only communicate through the AV through the AV bundlebundleL9, S2

EpicardiumEpicardium

DFIACTDFIACT AdiposeAdipose Coronary vessels Coronary vessels

and cardiac nervesand cardiac nerves Externally lined by Externally lined by

mesotheliummesothelium Simple squamous Simple squamous

cellscells Secrete serous fluid Secrete serous fluid

at visceral and at visceral and parietal pericardiumparietal pericardium

L9, S3

Z

I

M

A H

L9, S5

MyocardiumMyocardium L9, S6L9, S4

Masson’s Trichrome

EndocardiumEndocardium Inner layerInner layer

Simple squamous Simple squamous epithelium and CTepithelium and CT

Elastic laminaElastic lamina Middle layerMiddle layer

LACT with smooth LACT with smooth musclemuscle

Subendocardial Subendocardial layerlayer Purkinje fibersPurkinje fibers Continuous with Continuous with

myocardiummyocardium

L9, S7

Purkinje FibersPurkinje Fibers Branches of the Branches of the

AV bundle of HisAV bundle of His Cardiac muscle Cardiac muscle

modified for modified for conducting conducting impulsesimpulses

Located in the Located in the subendotheliumsubendothelium

L9, S11

Hypertrophied cardiac muscle Hypertrophied cardiac muscle fibersfibers

One or two nuclei centrally situatedOne or two nuclei centrally situated Rich in glycogen and mitochondriaRich in glycogen and mitochondria

L9, S12

1

2

3

Tunica IntimaTunica Intima Internal Elastic Internal Elastic

Membrane Tunica Membrane Tunica MediaMedia

External Elastic External Elastic MembraneMembrane

Tunica AdventitiaTunica Adventitia

L9, S13

The Aorta: An Elastic The Aorta: An Elastic ArteryArtery

Tunica IntimaTunica Intima Endothelium and BMEndothelium and BM

Internal Elastic MembraneInternal Elastic Membrane Tunica MediaTunica Media

Reticular or Elastic fibersReticular or Elastic fibers SMCs connecting elastic SMCs connecting elastic

fibersfibers External Elastic External Elastic

MembraneMembrane Tunica AdventitiaTunica Adventitia

DiffuseDiffuse Vasa vasorumVasa vasorum Nervi vascularusNervi vascularus

L9, S16

L9, S15

A

B

C

D

E

F

G

A = AortaA = Aorta B = VeinB = Vein C = ArteryC = Artery D = NerveD = Nerve E = Brown adiposeE = Brown adipose F = White adiposeF = White adipose G = CTG = CT

L9, S17

AortaAorta

Weigert Stain of Weigert Stain of the Elastic laminathe Elastic lamina

L9, S19

A

B

C

D

E. None of the above Q1

L9, S6L9, S4

A B

Q2 and Q3

L9, S12