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circulatory system
In histology and embryology, the circulatory system is a continuous and closed duct system, including the cardiovascular system and the lymphatic system. Contains heart, blood vessels etc.
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circulatory system
- One Hundred Years of Solitude Character Relationship Chart
One Hundred Years of Solitude is the masterpiece of Gabriel Garcia Marquez. Reading this book begins with making sense of the characters' relationships, which are centered on the Buendía family and tells the story of the family's prosperity and decline, internal relationships and political struggles, self-mixing and rebirth over the course of a hundred years.
- One Hundred Years of Solitude Character Relationship Chart
One Hundred Years of Solitude is the masterpiece of Gabriel Garcia Marquez. Reading this book begins with making sense of the characters' relationships, which are centered on the Buendía family and tells the story of the family's prosperity and decline, internal relationships and political struggles, self-mixing and rebirth over the course of a hundred years.
- Project Management Process Template
Project management is the process of applying specialized knowledge, skills, tools, and methods to project activities so that the project can achieve or exceed the set needs and expectations within the constraints of limited resources. This diagram provides a comprehensive overview of the 8 components of the project management process and can be used as a generic template for direct application.
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circulatory system
Overview
The circulatory system is a continuous and closed duct system, including the cardiovascular system and the lymphatic system.
heart
1. The structure of the heart wall
The heart wall consists of three layers: endocardium, myocardium and epicardium from the inside to the outside.
1. Endocardium
endothelium
It is a single layer of squamous epithelium connected to the endothelium of blood vessels. The endothelium is thin and smooth, which facilitates blood flow
subendothelium
It is a fine connective tissue with a little smooth muscle inside
subendocardium
It is loose connective tissue containing small blood vessels and nerves. Purkinje fibers of the cardiac conduction system in the subendocardium of the ventricles
2. Myocardial membrane
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
3. Epicardium
The visceral layer of the pericardium, composed of mesothelium and connective tissue
4. Heart valves
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.
2. Heart conduction system
The cardiac conduction system is formed by special myocardial fibers, including the sinoatrial node, atrioventricular node, atrioventricular bundle, left and right bundle branches and branches at all levels. Its function is to generate impulses and conduct them to all parts of the heart, so that the atrial and ventricular muscles press a certain rhythmic contractions
1. Pacemaker cells
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.
2. Transitional cells
Mainly found around the sinus node and atrioventricular node and in the atrioventricular bundle, transitional cells play a role in conducting excitement
3. Purkinje fiber
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.
Blood vessel
1. Basic structure of blood vessel wall
1. Intima
①Endothelium
It is a single layer of squamous epithelium lining the lumen of blood vessels. The long axis of endothelial cells is mostly consistent with the direction of blood flow, the nucleus is in the center, and there are tight junctions and gap junctions between adjacent cells. There are abundant phagocytosis vesicles in the cytoplasm, which can transport substances inside and outside blood vessels.
W-P bodies are organelles unique to endothelial cells and are related to the synthesis and storage of antigens related to coagulation.
②Subendothelial layer
Thin layer of connective tissue located between the endothelium and internal elastic lamina
③Internal elastic membrane
Made of elastin, it is the dividing line between the intima and media of the artery.
2. Media
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.
3. adventitia
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.
2. Arteries
(1) Aorta
Features: Rich in elastic membrane and elastic fibers, also known as elastic arteries
1. Intima
The subendothelial layer is thicker and contains the internal elastic membrane, so the dividing line between the intima and the adventitia is not obvious.
2. Media
It is very thick. Under pathological conditions, the smooth muscle fibers of the media can migrate into the intima and proliferate, which is an important step in the process of atherosclerosis.
3. adventitia
thinner
(2) Middle artery
Characteristics: Because the tunica media is rich in smooth muscle, it is also called a muscular artery.
1. Intima
The cross-section of the elastic membrane is obviously wavy
2. Media
thicker
3. adventitia
Approximately the same thickness as the tunica media
(3) Arterioles
general external elastic membrane
(4) Arterioles
Intimal inelastic membrane
(5) The relationship between arterial wall structure and function
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.
3. Veins
The tube diameter is large, the tube wall is thin, and the tube lumen is irregular in shape, often flat or collapsed.
There are more connective tissue components in the wall, and the smooth muscles and elastic fibers are not as abundant as those of the arteries.
The boundaries between the inner, outer and middle membranes are not obvious
Large variation in pipe wall structure
Has a venous valve structure to prevent blood from flowing backwards
4. Capillaries
(1) Structure of capillaries
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.
(2) Classification of capillaries
1. Continuous capillaries
There are tight junctions between endothelial cells, the basement membrane is intact, and there are a large number of phagocytic vesicles in the cytoplasm (for material exchange).
Continuous capillaries are distributed in connective tissue, muscle tissue, lungs and central nervous system (places with low permeability)
2. Pore capillaries
The non-nucleated part of the endothelial cells is very thin, has many endothelial windows that penetrate the cytoplasm, and is generally closed by septa. Endothelial cells have few endocytic vesicles, intact basement membrane, and few pericytes. Endothelial windows are conducive to material exchange of medium and small molecules inside and outside blood vessels.
Mainly distributed in gastrointestinal mucosa, certain endocrine glands and renal blood vessels, etc.
3. Sinusoids (sinusoidal capillaries)
The lumen is larger and irregular in shape. The endothelial cells have fenestrations, no septa, and the basement membrane is incomplete or absent. There are large gaps between endothelial cells
Material exchange in sinusoids occurs through the fenestrations and intercellular spaces of endothelial cells.
Blood sinusoids are mainly distributed in the spleen, bone marrow and some endocrine glands (where cell exchange and material metabolism are strong). The structure of blood sinusoids in different organs has great differences.