Circulation And Circulatory System
The Physiological process, by which digested food materials, oxygen, etc., are distributed throughout the body and hormones, enzymes, waste products, etc., are taken to their target sites through a particular fluid known as circulation.
The circulatory system is the organ system found in multicellular organisms that are concerned with the circulation of blood and consist of blood vessels and the heart.
Significance of animals do circulation: Multicellular not have most of their cells in contact with the external environment. Hence, they have developed oxygen, important metabolic substances and metabolic wastes. In the circulatory system, a fluid (blood) is driven through tubes (arteries, veins and capillaries) by a muscular pump (heart).
Transportation of useful substances to cells: Circulatory systems transport nutrients, waste products, hormones, respiratory gases, blood cells, antibodies and cells involved in the immune system in order to maintain homeostasis.
” human circulatory system”
Transportation of respiratory gases: Circulation helps in the transportation of respiratory gases between the lungs and all the cells of the body.
When deoxygenated blood passes through the respiratory surfaces of the lungs, gaseous exchange takes place, i.e., carbon dioxide leaves the blood and oxygen enters into the blood.
The oxygen-rich blood goes back to the heart and is pumped from the heart into the blood vessels, that transport blood throughout the body. Oxygen reaches all the cells of the body through blood.
Transportation of excretory substances: It transports all the excretory substances like carbon dioxide, and non-protein nitrogenous waste materials and helps in their elimination from the body.
Transportation of hormones: Some cells synthesise substances like hormones which regulate different metabolic processes. The circulatory system transports these substances to their target cells.
Transportation of nutrients or other materials to storage organs: It helps to transport substances from the site of production to organs where they are stored.
Maintenance of internal equilibrium: It regulates internal temperature and contributes to thermal regulation by distributing heat from heat-producing sites
to areas of the body that cannot keep themselves warm.
Types of circulatory system: Depending upon the type of circulating fluid, there are two types of circulatory system— blood circulatory system and lymphatic system. These are discussed under separate heads.
Blood Circulatory System
The blood circulatory system is of two types—open and closed circulatory system.
Open blood circulatory system
The blood circulatory system in which the heart pumps blood (haemolymph) Into the Haemocoel (body cavity) So That Blood Directly Bathes The Living Cells, Is Called an Open Blood Circulatory System.
” human circulatory system diagram”
Examples: Open circulatory systems are found in animals such as arthropods, molluscs, and some other invertebrate groups.
Advantages of an open circulatory system:
- Direct exchange of gases, nutrients, and waste products takes place between the living cells of the organiser Hence, less amount of energy is required.
- Animals with an open circulatory system (with the exception of insects that carry out gaseous exchange independently from the circulation) are generally slower and have a low metabolic rate.
- Blood pressure remains low.
Disadvantage of open circulatory system
This system is not very effective, because fluid is pumped under low pressure, so it circulates slower than in a closed circulatory system.
Closed Blood Circulatory System
The circulatory system in which the heart pumps the blood in the vessels, is called a closed blood circulatory system.
“human cardiovascular system diagram “
Lymphatic system
The lymphatic system is a network of tubular vessels or ducts and nodes through which lymph flows.
The lymphatic system is made up of the following structures—
Lymphatic capillaries: Lymphatic capillaries are tube-like structures. They have thin walls made of only a single layer of endothelial cells resting on a basement membrane.
They are closed at one end (blind end). They remain interwoven with blood capillaries but are not connected to them. They are wider than blood capillaries.
The lumens of these capillaries are filled with lymph and walls are permeable to interstitial fluid constituents, including protein Lymph vessels or lymph ducts Lymphatic capillaries join to form lymphatic vessels.
These vessels are structurally similar to the cardiovascular veins, though they have thinner walls and more valves. These valves prevent the backward flow of lymph as lymph flows toward the thoracic cavity.
Smaller lymphatic vessels unite to form larger lymphatic vessels. These larger vessels unite to form the two main lymphatic vessels or trunks.
They are called the thoracic duct and the right lymphatic duct.
The thoracic duct receives lymph from the entire body The thoracic duct receives lymph from the entire body The thoracic duct receives lymph from the entire body lymphatic duct.
This duct joins to the left subclavian vein near the left side of the heart. The right lymphatic duct is present on the right side of the thoracic region. It collects lymph from the right hand, throat and thorax.
This duct opens into the right subclavian vein Cistema chyli: A small, dilated sac found near the lower area of the thoracic duct in the lumbar region of the body is called the cistema chyli or receptaculum chyli. It is part of the lymphatic system into which lymph from the intestinal trunk and two lumbar lymphatic trunks flow.
” cardiovascular system notes”
Lymph glands or lymph nodes: The lymph nodes are small bean-shaped structures that look like tiny bulbs and are found at intervals along the lymph vessels. They are masses of collagen and elastin fibres surrounded by a capsule made of fibrous tissue.
The afferent lymphatic vessels enter and efferent lymphatic vessels leave the lymphatic nodes.
Lymph nodes are especially abundant in specific regions such as armpits, neck and groins.
Axillary nodes, intercostal nodes, and inguinal nodes are some of the lymphatic nodes.
Besides these, some other glands such as the spleen, tonsils, etc., also consist of lymphatic tissues. The spleen is considered to be the largest lymphatic gland in the human body
“transportation in humans “
Function Of Lymph Nodes
- Lymph nodes filter different foreign particles such as bacteria, etc., from the lymph.
- Lymphocytes are produced from the lymphoid cells present in the lymph glands. These lymphocytes are transported to the blood vessels through lymphatic vessels. They develop the immunity power of the body by producing antibodies.
- Several antitoxins and antibiotics are produced from lymph nodes. These substances destroy the toxins that enter our body.
Spleen
- It is the largest lymph gland present in our body. Some part of it is composed of lymphoid tissues.
- It is located between the diaphragm and the fundus region of the stomach.
“circulatory system function “
Function of spleen
- Spleen is the graveyard of RBCs. The worn-out RBCs are phagocytised by the macrophages present in the spleen.
- It works as a blood reservoir as it can store some amount of RBCs during rest.
- Lymphocytes originate in the spleen.
- It produces antibodies and antitoxins.