Cardiovascular system

Blood vascular system

A closed supply and drainage system, a continuous loop

Lymphatic vascular system

An open-entry drainage system (a one-way system)

Three main types of blood vessels

Arteries (supply), capillaries (exchange), and veins (drainage).

Heart structure

Shape: blunt and cone shaped

Pointed end - Apex

Broad end - Base

What is the position of the heart in the body?

The heart sits rotated to the left.

Where does the superior border of the heart sit?

Between the 2nd and 3rd ribs.

Where does the inferior border of the heart sit?

Between the 5th and 6th ribs.

What is the PMI in relation to the heart?

The point of maximal impulse, or apex beat, produces the loudest heart sound.

Three places where the right atrium receives deoxygenated blood

Superior vena cava, inferior vena cava, coronary sinus

What are the 3 Layers of the heart wall?

Endocardium, Myocardium, Epicardium

What is the pericardium?

Outer bag/pocket that the heart sits in

Atrioventricular (AV) valves function

Prevent backflow of blood into the atria during ventricular contraction.

Atrioventricular (AV) valves location

Located between the atria and ventricles.

Tricuspid valve location

Between the right atrium and right ventricle.

Bicuspid (mitral) valve location

Between the left atrium and left ventricle.

Semilunar (SL) valves function

Prevent backflow of blood into the ventricles during ventricular relaxation.

Semilunar (SL) valves location

Located at the connections between the ventricles and major arteries.

Pulmonary semilunar valve location

Between the right ventricle and the pulmonary trunk.

Aortic semilunar valve location

Between the left ventricle and the aorta.

Myocardium location in heart wall

The thick middle layer located between the endocardium and epicardium.

Cardiomyocyte structure

Short, branched, striated cells containing a single central nucleus.

Intercalated disks role

Specialized cell junctions connecting adjacent cardiomyocytes for synchronized contraction.

Gap junctions in intercalated discs function

Allow electrical impulses to pass rapidly between cells.

Why is the left ventricular myocardium thickest?

Must generate enough pressure to pump blood through the entire systemic circulation.

Atrioventricular (AV) valves function

Prevent backflow of blood into the atria during ventricular contraction.

The layers of blood vessels

tunica intima, tunica media, tunica adventitia (externa)

Tunica intima

Very thin layer that provides a non-stick environment for blood to run through

Internal elastic laminate- a condensed sheet of elastic tissue

What is the tunica intima primarily composed of?

Endothelium - a simple squamous layer that lines all vessels

What is the sub-endothelium?

A spouse pad of loose FCT cushioning the endothelium in the tunica intima

What is the internal elastic lamina (IEL)?

A condensed sheet of elastic tissue

Tunica media

Smooth muscle, connective tissue fibres mainly elastin and collagen. Thickness of media is proportional to both vessel diameter and blood pressure. (Arteries with thick tunica media tend to have blood of higher pressure, with artery of thin tunica media having blood of lower pressure)

Tunica adventitia

Loose FCT (fibrous connective tissue) with high content of collagen and some elastin. Lymphatics and autonomic nerves are also found in this region

Arteriole

Resistance vessels of the circulation - determines the blood pressure

Capillaries

Site of exchange between blood and tisssues

Venules

small vessels that drain from the capillaries into the veins. Direction of flow right to left.

What type of pressure do veins operate under?

Low pressure

What is the flow direction in veins?

One-way (unidirectional) flow

What are veins referred to as due to their ability to hold extra blood volume?

Capacitance vessels

What is the shape and structure of veins?

Irregular, flattened shape with large lumen & thin wall

Which layer is often the thickest in veins?

Adventitia

How does the media layer of veins compare to that of arteries?

The media is much thinner than that of arteries

Continuous capillaries

A type of capillary characterized by a continuous endothelial lining, allowing for the diffusion of small molecules while preventing the passage of larger ones.

Fenestrated capillaries

A type of capillary with small pores in its endothelial cells, allowing for increased permeability for filtration of small molecules and fluids. (Leaky)

Sinusoidal capillaries

A type of capillary that is larger and more irregularly shaped than typical capillaries, allowing for a greater exchange of materials between blood and surrounding tissues. (Very leaky)