Histology of the CVS Flashcards
What are the layers of the cardiovascular system?
The heart and blood vessels have 3 layers of tunicas:
Tunica intima - innermost
Tunica media - middle
Tunica externa/adventitia - outer
What are the layers in the heart?
Endocardium (tunica intima) - the epithelia lining the heart, in contact with blood.
Myocardium (tunica media) - cardiac muscle.
Epicardium (tunica adventitia) - inner layer of pericardium, outer layer of heart.
What do the layers of the heart look like?
see picture
What are the layers of the heart and pericardium?
Endocardium
Myocardium
Epicardium
Pericardial space
Parietal pericardium
Fibrous pericardium
What is the pericardial space?
Pericardial space has fluid in it which acts as a lubricant, so heart doesn’t rub against fibrous pericardium when it contracts.
What is the endocardium?
Endothelium and subepithelial connective tissue
Endothelium is the simple squamous epithelium that lines the blood vessels and the heart.
What does the endocardium look like?
Endothelial layer
Underneath is dense irregular connective tissue
Then subendothelial layer, which connects it to myocardium.
See picture.
What is the myocardium?
Striated - myofibrils
Involuntary, under influence of ANS.
Central nuclei
Elongated and branched cells
Tightly connected by intercalated discs.
What are the intercalated discs?
Contain gap junctions, desmosomes, and adhering junctions.
Allows electrical and physical connecting of myocardial cells.
Rapid spread of contractile stimuli, and physical anchorage, allows cardiomyocytes to form functional syncytium.
What does the myocardium look like?
See picture
What is the epicardium?
Collection of connective tissue - adipose and collagen, and lymphatic vessels.
On the outside is the mesothelium, simple squamous epithelium, lines the pericardial cavity.
see picture
What are the valves?
Formed by thin folds of endocardium.
Covered with endothelium.
At the core is dense connective tissue - fibroelastic.
Prevent backflow of blood.
What is the pathology of heart valves?
Endocarditis infection can cause faulty valves and damages them, causes clots, which can cause strokes.
Oral microbes can cause infective endocarditis.
What is the fibrous cardiac skeleton?
Four fibrous rings of dense irregular tissue make up the fibrous core of the heart.
Insulates electrically atria above from the ventricles below.
Attachment site for the myocardium and heart valves.
What is the conductive system of the heart?
Impulses start at the SA node, then travel to AV node, then to interventricular septum via bundle of his.
Separates and forms Purkinje fibres, which spread across the ventricles.
Go into the capillary bodies, specialised to carry cardiac impulses for contraction.
What do the Purkinje fibres look like?
Specialised for conduction:
In subendocardial layer.
Bigger than fibres of cardiomyocytes, of myocardium.
Paler as fewer myofibrils are present, and mainly at cell periphery.
More glycogen.
No intercalated discs.
See picture.
What are the layers of the blood vessels?
Tunica intima - inner, continuous with endocardium.
Tunica media - middle, continuous with myocardium.
Tunica externa/adventitia - outer, continuous with pericardium.
What is the tunica intima?
Endothelium, sat on a basement membrane.
Has connective tissue - subendothelial layer.
Sometimes has internal elastic lamina - continuous layer of elastic tissue.
What is the tunica media?
Mainly concentric layers of smooth muscles and elastin.
Sometimes has external elastic lamina.
Some collagen present.
What is the tunica externa?
Collagen rich connective tissue - strength and anchor to structures.
Simple squamous epithelium - mesothelium on outer surface.
Larger vessels have lymphatics, nerves and vasa vasorum - own blood supply to the vessel walls.
How are the arteries different from veins?
More defined and broader tunica media than veins, and it has different contents depending on the specific function - muscular or elastic.
What are the elastic arteries?
The major arteries immediately off the heart -aorta, carotid and pulmonary arteries.
Very broad tunic media, with lots of elastic fibres and collagen and some smooth muscle cells.
Elastic arranged in layers.
What is the function of the elastic arteries?
Elastin allows vessels to expand to accept large volume of blood.
Elastin allows recoil, which helps maintain arteriole pressure during diastole.
What are the distinguishable features of the elastic arteries?
Many elastic lamina.
Fenestrations of elastic tissue.
Broad tunica media.