Physiology ofPhysiology of venous and lymphatic vessels venous and lymphatic vessels

MicrocirculationMicrocirculation● ● The The microcirculationmicrocirculation is the is the blood flow

through through blood vessels smaller than 100 µm smaller than 100 µm (i.e. (i.e. arterioles, , capillaries, and , and venules). ).

● ● FunctionFunction:: 1. 1. Transport of cells, oxygen and Transport of cells, oxygen and

other substancesother substances to/from the tissuesto/from the tissues 2. 2. Regulation of body temperatureRegulation of body temperature

MicrocirculationMicrocirculation consists of 3 consists of 3 components:components:

1. Haemomycrocyrculation (arterioles, 1. Haemomycrocyrculation (arterioles, precapillares, capillares, postcapillares precapillares, capillares, postcapillares venules, venules, arterioles-venules venules, venules, arterioles-venules anastomosis)anastomosis)

2. Substance2. Substance’ transport to intercticium, where ’ transport to intercticium, where some hydrostatic and oncotic pressure createssome hydrostatic and oncotic pressure creates

3. Limphatic vessels – their walls more thin 3. Limphatic vessels – their walls more thin than in arteriales and don’t contain basal than in arteriales and don’t contain basal membrane. Intercellular cracks – they are the membrane. Intercellular cracks – they are the main way of penetration of tissue fluidmain way of penetration of tissue fluid into the into the lumen of lymphatic vesselslumen of lymphatic vessels

Morpho-functional properties of venous systemMorpho-functional properties of venous system

Veins are the vessels, which are carry out Veins are the vessels, which are carry out blood from organs, tissues to heart in blood from organs, tissues to heart in right atrium. Only pulmonary vein carry right atrium. Only pulmonary vein carry out blood from lungs in left atrium. There out blood from lungs in left atrium. There are superficial (skin) and deep veins. are superficial (skin) and deep veins. They are very stretching and have a low They are very stretching and have a low elasticity. Valves are present in veins. elasticity. Valves are present in veins. Plexus venosus are storage of blood. Plexus venosus are storage of blood. Blood moving in veins under gravity.Blood moving in veins under gravity.

Mechanism of regulationMechanism of regulation Difference of pressure in venous system is a Difference of pressure in venous system is a

cause of blood moving. From the place of high cause of blood moving. From the place of high pressure blood moving to the place of low pressure blood moving to the place of low pressure. pressure.

Negative pressure in chest is a cause of blood Negative pressure in chest is a cause of blood moving. moving.

Contraction of skeletal muscles, diaphragm Contraction of skeletal muscles, diaphragm pump, peristaltic movement of veins walls are the pump, peristaltic movement of veins walls are the causes of moving.causes of moving.

Blood flow in veinsBlood flow in veins Blood flows through the blood vessels, Blood flows through the blood vessels,

including the veins, primarily, because of the including the veins, primarily, because of the pumping action of the heart, although venous pumping action of the heart, although venous flow is aided by the heartbeat, the increase in flow is aided by the heartbeat, the increase in the negative intrathoracic pressure during the negative intrathoracic pressure during each inspiration, and contractions of skeletal each inspiration, and contractions of skeletal muscles that compress the veins (muscle muscles that compress the veins (muscle pump).pump).

Venous pressureVenous pressure Venous pressure is pressure of blood, which Venous pressure is pressure of blood, which

are circulated in veins. are circulated in veins. Venous pressure in healthy person is from 50 Venous pressure in healthy person is from 50

to 100 mm H2O. to 100 mm H2O. Increase of venous pressure in physiological Increase of venous pressure in physiological

condition may be in the action of physical condition may be in the action of physical activity. Determine of venous pressure is activity. Determine of venous pressure is called phlebotonometry and give for doctors called phlebotonometry and give for doctors information about activity of right atrium.information about activity of right atrium.

Methods for assessing blood flow in Methods for assessing blood flow in the veinsthe veins

Magnetic resonance venography of normal sinuses of the brain (posterior-lateral projection).

PhlebographyPhlebography аа –– atria waveatria wave ––contraction of contraction of

right atriumright atrium

сс –– passing of carotid artery passing of carotid artery pulse on veinpulse on vein

хх –– systole of ventriclessystole of ventricles

vv –– ventricularventricular –– filling of filling of atrium by bloodatrium by blood

yy –– passing of blood in right passing of blood in right atriaatria

Lymphatic systemLymphatic system The The lymphatic systemlymphatic system is a complex network is a complex network

of of lymphoid organslymphoid organs, , lymph nodeslymph nodes, , lymph lymph ductsducts, and , and lymph vesselslymph vessels that produce and that produce and transport lymph fluid from transport lymph fluid from tissues to the to the circulatory system. .

The lymphatic system is a major component of The lymphatic system is a major component of the the immune system. .

Morpho-functional properties of lymphatic systemMorpho-functional properties of lymphatic system

Lymph systemLymph system has capillaries, vessels, where present has capillaries, vessels, where present valves, lymphvalves, lymphaticatic nodes. In lymphatic nodes are nodes. In lymphatic nodes are lymphopoiesis, depo of lymph, their function is barrier-lymphopoiesis, depo of lymph, their function is barrier-filter. Lymph flow in vein system through the chest filter. Lymph flow in vein system through the chest lymph ductus. lymph ductus.

Functions of lymph:Functions of lymph: 1. support of constant level of volume and components 1. support of constant level of volume and components

of tissue fluid; of tissue fluid; 2. transport of nutritive substances from digestive tract in 2. transport of nutritive substances from digestive tract in

venous system; venous system; 3. barrier-filter function. 3. barrier-filter function. 4. 4. ttake place in immunology reactions.ake place in immunology reactions.

Lympathatic system The lymphatic system has three primary functions.

First of all, it returns excess interstitial fluid to the blood.

The second function of the lymphatic system is the absorption of fats and fat-soluble vitamins from the digestive system and the subsequent transport of these substances to the venous circulation.

The third and probably most well known function of the lymphatic system is defense against invading microorganisms and disease.

Lymphatic capillariesLymphatic capillaries

Lymphatic capillaries begin as one side Lymphatic capillaries begin as one side closed capacities, which are drained by closed capacities, which are drained by smallest lymphatic vessels. smallest lymphatic vessels.

Pressure of lymph inside the capillary Pressure of lymph inside the capillary is lower than in intracellular space, is lower than in intracellular space, which helps to lymph flow. Capillary which helps to lymph flow. Capillary wall has basal membrane and one layer wall has basal membrane and one layer of endotheliocytes.of endotheliocytes.

LymphLymph

--The lymphatic capillaries are The lymphatic capillaries are responsible for returning responsible for returning interstitial fluid and proteins to interstitial fluid and proteins to the vascular compartment.the vascular compartment.

-Lymph capillaries merge into -Lymph capillaries merge into large thoracic duct which large thoracic duct which empties into the large veins. empties into the large veins.

-Lymph vessels have smooth -Lymph vessels have smooth muscle for movement and muscle for movement and surrounding skeletal muscle surrounding skeletal muscle contractions and contain open contractions and contain open ends. ends.

LymphLymph LymphLymph originates as originates as blood plasma that leaks from the that leaks from the

capillaries of the capillaries of the circulatory system, becoming , becoming interstitial fluid, and filling the space between individual cells , and filling the space between individual cells of tissue. of tissue.

Plasma is forced out of the capillaries by Plasma is forced out of the capillaries by hydrostatic pressure, , and as it and as it mixes with the interstitial fluidmixes with the interstitial fluid, the volume of fluid , the volume of fluid accumulates slowly. accumulates slowly.

Most of the fluid is returned to the capillaries by Most of the fluid is returned to the capillaries by osmosis (about 90% of the former plasma). (about 90% of the former plasma).

The excess interstitial fluid is collected by the The excess interstitial fluid is collected by the lymphatic lymphatic systemsystem by by diffusion into into lymph lymph capillaries, and is processed , and is processed by by lymph nodeslymph nodes prior to being returned to the circulatory prior to being returned to the circulatory system. system.

Once within the lymphatic system the fluid is called Once within the lymphatic system the fluid is called lymphlymph, , and has almost the same composition and has almost the same composition as the original as the original interstitial fluid.interstitial fluid.

Lymphatic circulationLymphatic circulation The lymphatic systemThe lymphatic system acts as a acts as a secondary circulatory systemsecondary circulatory system, except , except

that it that it collaborates with white blood cells in lymph nodescollaborates with white blood cells in lymph nodes to protect to protect the body from being infected by cancer cells, fungi, viruses or the body from being infected by cancer cells, fungi, viruses or bacteria. bacteria.

Unlike the circulatory systemUnlike the circulatory system, the lymphatic system , the lymphatic system is not closedis not closed and and has no central pumphas no central pump; the lymph moves slowly and under low ; the lymph moves slowly and under low pressure due to pressure due to peristalsis, the operation of , the operation of semilunar valves in the in the lymph veins, and the milking lymph veins, and the milking action of skeletal musclesaction of skeletal muscles. .

Like veinsLike veins, , lymph vesselslymph vessels have one-way, have one-way, semilunar valvessemilunar valves and and depend mainly on the movement of depend mainly on the movement of skeletal musclesskeletal muscles to squeeze fluid to squeeze fluid through them. through them.

Rhythmic contractionRhythmic contraction of the vessel walls may also help draw fluid of the vessel walls may also help draw fluid into the lymphatic capillaries. into the lymphatic capillaries.

This fluid is then transported to progressively larger lymphatic vessels This fluid is then transported to progressively larger lymphatic vessels culminating in culminating in the right lymphatic ductthe right lymphatic duct (for lymph from the right (for lymph from the right upper body) and upper body) and the thoracic ductthe thoracic duct (for the rest of the body); these (for the rest of the body); these ducts drain into the ducts drain into the circulatory systemcirculatory system at the right and left at the right and left subclavian veins. .

Function of Limphatic nodeFunction of Limphatic node 1. Lymph nodes play role of

filtration barrier. This function possible due to the presence of macrophages and net of reticular fibers in the lumen of the sinuses.

2. Lymph nodes are organs of lymphopoiesis (B - and T-lymphocytes)

3. Lymph nodes – they are deposit of lymph.

The main drains of the lymphatic system in which lymph flows in to the venous system is the Lymphatic thoracic duct and cervical lymphatic duct, which collects lymph from the head and surrounding areas.

Ultrasound examination of lymph Ultrasound examination of lymph nodesnodes

Production of lymphProduction of lymph Fluid efflux normally exceeds influx Fluid efflux normally exceeds influx

across the capillary walls, but the extra across the capillary walls, but the extra fluid enters the lymph and drains through fluid enters the lymph and drains through them back into the blood. This keeps the them back into the blood. This keeps the interstitial fluid pressure from rising and interstitial fluid pressure from rising and promotes the turnover of tissue fluid. promotes the turnover of tissue fluid.

The normal 24-hour lymph flow is 2-4 L. The normal 24-hour lymph flow is 2-4 L.

Mechanism of lymph flowMechanism of lymph flow Lymph flow is due to movements of skeletal Lymph flow is due to movements of skeletal

muscle, the negative intrathoracic pressure during muscle, the negative intrathoracic pressure during inspiration, the suction effect of high velocity inspiration, the suction effect of high velocity flow of blood in the veins in which the lymphatic flow of blood in the veins in which the lymphatic vessels terminate, and rhythmic contractions of vessels terminate, and rhythmic contractions of the walls of the large lymph ducts.the walls of the large lymph ducts.

Since lymph vessels have valves that prevent Since lymph vessels have valves that prevent backflow, skeletal muscle contractions push the backflow, skeletal muscle contractions push the lymph toward the heart. lymph toward the heart.

Pulsations of arteries near lymphatic vessels may Pulsations of arteries near lymphatic vessels may have a similar effect. have a similar effect.

ThymusThymus The The thymusthymus is an organ located in the upper is an organ located in the upper

anterior portion of the portion of the chest cavity. . The thymus plays an important role in the The thymus plays an important role in the

development of the immune system in early life, development of the immune system in early life, and its cells form a part of the body's normal and its cells form a part of the body's normal immune system. immune system.

It is most active before puberty, after which it It is most active before puberty, after which it shrinks in size and activity in most individuals and shrinks in size and activity in most individuals and is replaced with fat. is replaced with fat.

Function:Function: Production (maturation) of T cells. Production (maturation) of T cells.

SpleenSpleen The The spleen spleen is located in the upper left part of the is located in the upper left part of the

abdomen, behind the stomach and just below the abdomen, behind the stomach and just below the diaphragm. diaphragm.

The spleen is the largest collection of lymphoid tissue in The spleen is the largest collection of lymphoid tissue in the body. the body.

It is regarded as one of the centres of activity of the It is regarded as one of the centres of activity of the reticuloendothelial system. reticuloendothelial system.

Its absence leads to a predisposition to certain infections. Its absence leads to a predisposition to certain infections. Function:Function:

– Blood reservoirBlood reservoir– Destruction of old red blood cells Destruction of old red blood cells – Immune functionsImmune functions– Blood cells production in embryogenesisBlood cells production in embryogenesis

TonsilsTonsils Tonsils are clusters of lymphatic tissue just Tonsils are clusters of lymphatic tissue just

under the mucous membranes that line the under the mucous membranes that line the nose, mouth, and throat (pharynx). nose, mouth, and throat (pharynx).

There are three groups of tonsils. There are three groups of tonsils. The pharyngeal tonsils are located near the The pharyngeal tonsils are located near the

opening of the nasal cavity into the pharynx. opening of the nasal cavity into the pharynx. When these tonsils become enlarged they When these tonsils become enlarged they may interfere with breathing and are called may interfere with breathing and are called adenoids. adenoids.

THANCK YOU!THANCK YOU!