Venous vessels are an essential part of the vessel-heart system of the body, closely interconnected with lymph and arteries. Thanks to the venous system , the flow of lymph and blood to the heart is ensured.
The veins of the pulmonary circulation are a closed system of vessels that collect oxygen-depleted blood from all body cells and tissues, united by the following subsystems:
- heart veins;
- superior vena cava;
- inferior vena cava.
The difference between venous and arterial blood
Venous blood is blood that flows back from all cellular systems and tissues, saturated with carbon dioxide, containing metabolic products.
Medical manipulations and studies are carried out mainly with such blood, which contains the end products of metabolism and less glucose.
Arterial blood is blood that flows to all cells and tissues from the heart muscle, saturated with oxygen and hemoglobin, containing nutrients.
Oxygenated arterial blood circulates through the arteries of the great circle and through the veins of the pulmonary circulation.
Vein structure
The walls of the venous vessels are much thinner than arterial, since the blood flow velocity in them and the pressure are lower. Veins are stretched easier, their elasticity is lower than arteries. Vascular valves are usually located opposite, which prevents the return of blood. Valve veins in the lower extremities are located in large numbers. In the veins there are also lunar valves from the folds of the inner shell, which have special elasticity. In the arms and legs there are venous vessels located between the muscles, this with muscle contraction allows blood to return back to the heart.
Blood circulation process
The large circle originates in the left ventricle of the heart, and an aorta with a diameter of up to three centimeters comes out of it. Further, the oxygenated blood of the arteries enters through the vessels decreasing in diameter to all organs. Having given all the useful substances, the blood is saturated with carbon dioxide and goes back through the venous system through the smallest vessels - venules, while the diameter gradually increases, approaching the heart. Venous blood from the right atrium is pushed out into the right ventricle, and a small circle of blood circulation begins. Entering the lungs, the blood is again filled with oxygen. Arterial blood flows through the veins into the left atrium, which is further pushed into the left ventricle of the heart, and the circle repeats again.
Arteries and veins of a large circle of blood circulation include the aorta, as well as smaller, upper and lower hollow vessels branching from it.
Small capillaries make up an area of about one and a half thousand square meters in the human body.
The veins of the pulmonary circulation carry depleted blood, except for umbilical and pulmonary, which carry arterial, oxygenated blood.
Heart vein system
These include:
- heart veins that go directly to the heart cavity;
- coronary sinus;
- large heart vein;
- left ventricular posterior vein;
- left atrial oblique vein;
- front vessels of the heart;
- medium and small veins;
- atrial and ventricular;
- smallest venous vessels of the heart;
- atrioventricular.
The driving force of the blood flow is the energy set by the heart, as well as the pressure difference in the departments of blood vessels.
Superior vena cava system
The superior vena cava takes venous blood of the upper body - the head, neck, sternum and partially the abdominal cavity and enters the right atrium. Vascular valves are absent. The process is as follows: the blood of the superior vein saturated with carbon dioxide flows into the pericardial region, lower - into the region of the right atrium. The superior vena cava system is divided into the following parts:
- The upper hollow is a small vessel, 5-8 cm long, 2.5 cm in diameter.
- Unpaired - a continuation of the right ascending lumbar vein.
- Semi-unpaired - a continuation of the left ascending lumbar vein.
- Rear intercostal - collecting veins of the back, its muscles, external and internal vertebral plexuses.
- Intravertebral venous connections - located inside the spinal canal.
- Shoulderheads are the roots of the superior hollow.
- Vertebral - location in the diametrical openings of the cervical vertebrae.
- Deep cervical - collection of venous blood of the occipital region along the carotid artery.
- Inner thoracic.
Inferior vena cava system
The lower hollow is the connection of the iliac veins from two sides in the region of 4 to 5 vertebrae of the lower back, takes venous blood of the lower parts of the body. The inferior vena cava is one of the largest veins in the body. It is about 20 cm long and up to 3.5 cm in diameter. Thus, outflow from the legs, pelvis and abdomen from the lower hollow occurs. The system is divided into the following components:
- Inferior vena cava.
- The lumbar veins are the abdominal cavity.
- Lower diaphragmatic - collection of blood from the lower diaphragm.
- The group of visceral vessels - includes the renal and adrenal, vessels of the testicles and ovaries, hepatic veins.
- Vorotnaya - combines blood from unpaired organs of the peritoneum - the stomach, liver, spleen and pancreas, as well as partially the intestines.
- Lower mesenteric - includes the upper part of the rectum, sigmoid and descending colon.
- Upper mesenteric - includes the small intestine, cecum and appendix.
Portal vein
The portal vein got its name due to the trunk entering the gate of the liver, as well as the collection of venous blood from the digestive organs - stomach, spleen, large and thin intestines. Her vessels are located behind the pancreas. The length of the vessel is 500-600 mm, in diameter - 110-180 mm.
The inflows of the visceral trunk are the superior mesenteric, inferior mesenteric and splenic vessels.
The anatomy system of the portal vein basically includes the vessels of the stomach, intestines of the large and thin sections, pancreas, gall bladder and spleen. In the liver, it is divided into right and left and further branches into smaller veins. As a result, they connect to the central veins of the liver, the sublobular veins of the liver. And in the end, three to four hepatic vessels form. Thanks to this system, the blood of the digestive system passes through the liver, entering the subsystem of the inferior vena cava.
The superior mesenteric vein accumulates blood in the roots of the mesentery of the small intestine from the ileum, pancreatic, right and middle colon, iliac colon and right ventricular-omental veins.
The inferior mesenteric vein is formed from the superior rectal, sigmoid and left colon veins.
The splenic vein combines splenic blood, blood of the stomach, duodenum and pancreas.
Jugular vein system
A jugular vein vessel passes from the base of the skull to the supraclavicular cavity. The pulmonary circulation includes these veins, which are key blood collections from the head and neck. In addition to the internal, the external jugular vein also collects blood from the head and soft tissues. The outer begins in the region of the auricle and goes down along the sternocleidomastoid muscle.
Veins coming from the external jugular:
- back ear - collection of venous blood behind the auricle;
- occipital branch - collection from the venous plexus of the head;
- suprascapular - blood intake from formations of the periosteal cavity;
- transverse veins of the neck - satellites of the transverse cervical arteries;
- the anterior jugular - consists of the chin veins, maxillary-hyoid and sternum-thyroid muscles.
The internal jugular vein begins in the jugular cavity of the skull, being a satellite of the external and internal carotid arteries.
Big Circle Functions
It is thanks to the continuous movement of blood in the arteries and veins of a large circle of blood circulation that the main functions of the system are provided:
- transportation of substances to ensure the functions of cells and tissues;
- transport of necessary chemicals for metabolic reactions in cells;
- taking metabolites of cells and tissues;
- the connection of tissues and organs with each other through blood;
- transport to cells of protective equipment;
- intake of harmful substances from the body;
- heat exchange.
The vessels of this circle of blood circulation are a branched network that provides blood to all organs, in contrast to the small circle. The optimal functioning of the system of the upper and lower vena cava leads to the competent blood supply to all organs and tissues.