endothelium

subendothelium

subendocardium

Mainly composed of myocardium, the atrial muscle is thin, the muscle fibers are short and thin, and there are no branches. The ventricular muscle is very thick and can be roughly divided into three layers: inner longitudinal, middle ring, and outer oblique layers; the myocardial fibers are thick, long, branched, and arranged in a spiral shape.

Special atrial granules contain atrial natriuretic peptide, referred to as atrial natriuretic peptide, which has strong diuretic, natriuretic, blood vessel dilation and blood pressure lowering effects

The visceral layer of the pericardium, composed of mesothelium and connective tissue

Located at the atrioventricular orifice and arterial orifice, including the mitral valve, tricuspid valve, aortic valve and pulmonary valve, it is a thin structure formed by the endocardium protruding into the cardiac chamber to prevent blood from flowing backward.

P cells, referred to as P cells, are located in the connective tissue in the center of the sinoatrial node and the atrioventricular node. Pacemaker cells are the pacemaker points for cardiac excitement.

Mainly found around the sinus node and atrioventricular node and in the atrioventricular bundle, transitional cells play a role in conducting excitement

It consists of the atrioventricular bundle and its branches, located in the subendocardium of the ventricle. The intercalary disc is well developed and can conduct impulses quickly.

①Endothelium

②Subendothelial layer

③Internal elastic membrane

Its thickness and composition vary depending on the type of blood vessel. Large arteries are mainly composed of elastic membrane, and medium arteries are mainly composed of smooth muscle.

It is composed of loose connective tissue. When blood vessels are damaged, fibroblasts have the function of repairing the outer membrane.

In some arteries, there is an external elastic lamina at the junction of the media and adventitia, but the external elastic lamina is not continuous.

Features: Rich in elastic membrane and elastic fibers, also known as elastic arteries

1. Intima

2. Media

3. adventitia

Characteristics: Because the tunica media is rich in smooth muscle, it is also called a muscular artery.

1. Intima

2. Media

3. adventitia

general external elastic membrane

Intimal inelastic membrane

When the heart contracts, the walls of the aorta expand, and when the heart relaxes, the walls of the aorta retract elastically and act as an auxiliary pump, so the arterial blood flow is continuous.

The smooth muscle in the media of the middle artery is well developed. The contraction and relaxation of the smooth muscle shrink and expand the diameter of the blood vessel, thus regulating the blood flow distributed to various parts of the body and various organs.

The contraction and relaxation of arterioles and arterioles can significantly regulate the blood flow of organs and tissues.

Its wall is mainly composed of a layer of endothelial cells and basement membrane

Scattered between the endothelial cells and the basement membrane are flat cells with protrusions called pericytes.

The main function of pericytes is to provide mechanical support and contractile function. When blood vessels are damaged, pericytes can also proliferate and differentiate into endothelial cells and fibroblasts to participate in tissue regeneration and are equivalent to mesenchymal cells.

1. Continuous capillaries

2. Pore capillaries

3. Sinusoids (sinusoidal capillaries)