Which of the following is not a function of the lymphatic system?
3 Functions of Lymphatic system
The lymphatic system consists of a network of vessels and structures made up of lymphatic tissue. It plays a vital role in immunity.
- Drainage of excess fluid from the tissues
The lymphatic system is important for the distribution of fluid and nutrients in the body because it drains excess fluid from the tissues and returns to the blood protein molecules which are unable to pass back through the blood capillary walls because of their size.
- Absorbtion of products of fat digestion
The lymphatic system also plays an important part in absorbing the products of fat digestion from the villi of the small intestine. While the products of carbohydrate and protein digestion pass directly into the bloodstream, fats pass directly into the intestinal lymphatic vessels, known as lacteals.
- Fighting infection
The lymphatic nodes help to fight infection by filtering lymph and destroying invading micro-organisms.
Lymphocytes are reproduced in the lymph node and following infection they generate antibodies to protect the body against subsequent infection. Therefore, the lymphatic system plays an important part in the body’s immune system.
- prevention of oedema
- production of heat
- production of lymphocytes
- absorption of fat
Lymph is similar in composition to blood except it has a lower concentration of?
Lymph is a transparent, colourless, watery liquid which is derived from tissue fluid and is contained within lymphatic vessels. It resembles blood plasma in composition, except that it has a lower concentration of plasma proteins. This is because some large protein molecules are unable to filter through the cells forming the capillary walls so they remain in blood plasma.
Lymph contains only one type of cell and these are called lymphocytes.
The bone marrow and lymphatic glands produce lymphocytes.
Lymphocytes are leucocytes (white blood cells) that play a part in the body’s natural defenses and immunity against disease.
What is Lymph derived from?
- plasma proteins
- blood plasma
- tissue fluid
How is lymph formed?
As blood is distributed to the tissues some of the plasma escapes from the capillaries and flows around the tissue cells, delivering nutrients such as oxygen and water to the cell and picking up cellular waste such as urea and carbon dioxide. Once the plasma is outside the capillary and is bathing the tissue cells, it becomes tissue fluid. Some of the tissue fluid passes back into the capillary walls to return to the blood stream via the veins and some is collected by lymphatic vessels where it becomes lymph. Lymph is then taken through its circulatory pathway and is ultimately returned to the bloodstream.
The connection between blood and lymph
The lymphatic system is, therefore, often referred to as a secondary circulatory system as it consists of a network of vessels that assist the blood in returning fluid from the tissues back to the heart. In this way, the lymphatic system is a complementary system for the circulatory system. After draining the tissues of excess fluid, the lymphatic system returns this fluid to the cardiovascular system. This helps to maintain blood volume, blood pressure and prevent oedema.
Structure of the Lymphatic System
The lymphatic system contains the following structures:
- lymphatic capillaries
- lymphatic vessels
- lymphatic nodes
- lymphatic collecting ducts.
Lymphatic vessels commence as lymphatic capillaries in the tissue spaces of the body as minute blind-end tubes, as lymph is a one-way circulatory pathway. The walls of the lymphatic capillaries are like those of the blood capillaries in that they are a single-cell-layer thick to make it possible for tissue fluid to enter them.
However, they are permeable to substances of larger molecular size than those of the blood capillaries.
The lymphatic capillaries mirror the blood capillaries and form a network in the tissues, draining away excess fluid and waste products from the tissue spaces of the body. Once the tissue fluid enters a lymphatic capillary it becomes lymph and is gathered up into larger lymphatic vessels.
Lymphatic vessels are similar to veins in that they have thin, collapsible walls and their role is to transport lymph through its circulatory pathway. They have a considerable number of valves which help to keep the lymph flowing in the right direction and prevent backflow. Superficial lymphatic vessels tend to follow the course of veins by draining the skin, whereas the deeper lymphatic vessels tend to follow the course of arteries and drain the internal structures of the body.
Networks or plexuses of lymphatic channels exist throughout the body. These intertwined channels are found in the following areas:
Each lymphatic node receives lymph from several afferent lymphatic vessels and blood from small arterioles and capillaries. Valves of the afferent lymphatic vessels open towards the node, therefore lymph in these vessels can only move towards the mode. Lymph flows slowly through the node moving from the cortex to the medulla, and leaves through an efferent vessel which opens away from the node. The afferent vessels enter a lymphatic node and the efferent vessels drain lymph from a node.
The function of a lymphatic node is to act as a filter of lymph to remove or trap any micro-organisms, cell debris or harmful substances which may cause infection so that when lymph enters the blood, it has been cleared of any foreign matter. When lymph enters a node, it comes into contact with two specialised types of leucocytes:
From each chain of lymphatic nodes the efferent lymph vessels combine to form lymphatic trunks which empty into two main ducts – the thoracic and the right lymphatic ducts. These ducts collect lymph from the whole body and return it to the blood via the subclavian veins.
The thoracic duct is the main collecting duct of the lymphatic system. It is the largest lymphatic vessel in the body and extends from the second lumbar vertebra up through the thorax to the root of the neck. The thoracic duct collects lymph from the left side of the head and neck, left arm, lower limbs and abdomen, and drains into the left subclavian vein to return it to the bloodstream.
The right lymphatic duct is very short in length. It lies in the root of the neck and collects lymph from the right side of the head and neck and the right arm and drains into the right subclavian vein to be returned to the bloodstream.
Lymphocytes are reproduced in the lymph node and following infection they generate antibodies to protect the body against subsequent infection.
Once filtered the lymph leaves the node by one or two efferent vessels which open away from the node.
Lymphatic nodes occur in chains so that the efferent vessel of one node becomes the afferent vessel of the next node in the pathway of lymph flow. Lymph drains through at least one lymphatic node before it passes into two main collecting ducts before it is returned to the blood.
Which duct collects the majority of lymph?
Lymph passes through at least one node where it is filtered of cell debris, micro-organisms and harmful substances.
Once filtered, the lymph is collected into two main ducts – thoracic duct (the largest duct) which collects lymph from the left side of the head and neck, left arm, lower limbs and abdomen, and the right lymphatic duct which collects lymph from the right side of the head and neck and the right arm.
The collected lymph is then drained into the venous system via the right and left subclavian veins.
- cisterna chyli
- left lymphatic duct
- right lymphatic duct
- thoracic duct
Collected lymph is drained into the venous system via the:
- brachiocephalic veins
- subclavian arteries
- subclavian veins
- superior vena cava
In order to be cleansed of foreign matter lymph must pass through at least one:
The main groups of lymph nodes relating to the head and neck include deep cervical, superficial cervical, submandibular, occipital, mastoid and parotid nodes.
The main group of lymph nodes relating to the body include superficial cervical, deep cervical, axillary, suptratrochlear, thoracic, abdominal, pelvic, inguinal and popliteal nodes.
- lymphatic capillary
- lymphatic duct
- lymphatic node
- lymphatic vessel
Which of the following nodes drains lymph from the lower limbs?
Where is the axillary nodes situated in?
What effect does the lymphatic system have on the skin and muscles?
- Increases lymphatic circulation, helps remove waste and toxins from the skin and muscles so they work more efficiently
- Increases lymphatic circulation, increases waste and toxins in the skin and muscles so they work more effectively
- Decreases lymphatic circulation, helps remove waste and toxins from the skin and muscle fibres so they work more quickly
- Decreases lymphatic circulation, increases waste and toxins from the skin and muscles so they work more efficiently