Lymphatic system

What is the lymphatic system?

The cells, tissues, and organs responsible for defending the body against environmental hazards such as pathogens and internal threats such as cancer cells.

What are the general functions of the lymphatic system

-The production, maintenance, and distribution of lymphocytes that provide defense against infections and environmental hazards

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-Returns excess interstitial fluid to the blood

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-Absorption of fats and fat-soluble vitamins from the digestive tract and the subsequent transport of these substances to the venous circulation

Explain one

Lymph nodes and other lymphatic organs filter lymph to remove microbes and other foreign particles. The Lymphocytes destroy them

Returns excess interstitial fluid to the blood. explain

Lymph capillaries pick up excess interstitial fluid and proteins and return them to the venous blood. Lymph re-joins blood at the right and left subclavianveins

function 3 Absorption of fats and fat-soluble vitamins from the digestive tract

-Absorption of fats and fat-soluble vitamins from the digestive tract and the subsequent transport of these substances to the venous circulation

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-Done by blood capillaries (lacteal)

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.-The lacteals absorb the fat and fat-soluble vitamins from the intestinal tract

structure of lacteal

What are the main components of the lymphatic system?bk

Lymph; lymphatic vessels (lymphatics); lymphoid tissues and lymphoid organs; lymphocytes, phagocytes, and other immune system cells.

What is lymph?

A fluid similar to plasma that enters lymphatic capillaries after tissue fluid is formed from blood plasma; it does not have plasma proteins

How is tissue fluid related to lymph?

Tissue fluid is formed from blood plasma. When this fluid enters lymphatic capillaries, it is called lymph.

How is lymph formed?

Excess tissue fluid enters lymphatic vessels and forms lymph after most tissue fluid returns to circulation through venules.

How does the lymphatic system return excess interstitial fluid to the blood?

Lymph capillaries collect excess interstitial fluid and proteins and return them to venous blood.

Where does lymph rejoin the blood?

Lymph rejoins the blood at the right and left subclavian veins.

How does the lymphatic system absorb dietary fats?

Lacteals in the villi of the small intestine absorb fats and fat-soluble vitamins and transport them to venous circulation.

What are lymphatic vessels?

Vessels that carry lymph from peripheral tissues toward the venous system.

What is the pathway of lymph through the lymphatic system?

Lymphatic capillaries → lymphatic vessels → lymphatic trunks → lymphatic ducts.

Where are lymphatic capillaries found and where are they absent?

They are found throughout the body except the bone marrow, CNS, and epidermis.

Lymphatic capillaries

How do lymphatic capillaries differ from blood capillaries?

They have larger diameters, thinner walls, and are typically flattened or irregular in outline.

What is the function of overlapping endothelial cells in lymphatic capillaries?

They form one-way valves that allow fluid to enter the lymphatic capillary.

How are lymphatic vessels formed?

Lymphatic capillaries merge to form larger lymphatic vessels.

What are the characteristics of lymphatic vessel walls?

Their walls are similar to those of veins and contain valves visible as surface bulges.

What are the two sets of lymphatic vessels?

Superficial lymphatics and deep lymphatics.

Where are superficial lymphatics located?

In the subcutaneous layer, areolar tissues of mucous membranes, and serous membranes of the pleural, pericardial, and peritoneal cavities.

Where are deep lymphatics located?

In skeletal muscles, organs of the neck, limbs and trunk, and walls of visceral organs.

What are lymphatic trunks?

Larger tributaries formed when lymphatic vessels join together.

What are the major lymphatic trunks?

Right and left lumbar, intestinal, right and left bronchomediastinal, right and left subclavian, and right and left jugular trunks.

What areas do the lumbar trunks drain?

The lower limbs, pelvic walls and viscera, kidneys, adrenals, and abdominal wall.

What areas does the intestinal trunk drain?

The stomach, intestines, pancreas, spleen, and liver.

What areas do the bronchomediastinal trunks drain?

The trachea, bronchi, lungs, mamma, and heart.

What do the subclavian trunks drain?

The subclavian lymph nodes.

What do the jugular trunks drain?

The cervical lymph nodes of the head and neck.

What are the two major lymphatic ducts?

The right lymphatic duct and thoracic duct.

What area does the right lymphatic duct drain?

The upper right quadrant of the body.

What areas does the thoracic duct drain?

Areas inferior to the diaphragm and the left side of the body superior to the diaphragm.

What does the right lymphatic duct receive?

The right jugular, right subclavian, and right bronchomediastinal trunks.

What does the thoracic duct receive?

The right and left lumbar trunks, intestinal trunk, and left bronchomediastinal, subclavian, and jugular trunks.

Where does the thoracic duct empty?

Into the left subclavian vein near the left internal jugular vein.

Where does the right lymphatic duct empty?

Into the right subclavian vein.

What causes lymph to move through lymphatic vessels?

Skeletal muscle action, respiratory movement, and contraction of smooth muscle in vessel walls.

What is lymphedema?

An accumulation of interstitial fluid caused by blockage of lymph drainage from a limb.

What happens to a limb affected by lymphedema?

It becomes swollen and grossly distended; prolonged swelling can cause permanent loss of connective tissue elasticity.

What complications can prolonged lymphedema cause?

Stagnation of lymph may lead to accumulation of toxins and pathogens.

What are the causes of lymphedema listed in the PowerPoint?

Lymph node removal, parasitic infections such as filariasis, injury, radiation therapy, cellulitis, surgery, and tumors.

Lymphatic Filariasis

Tropical parasitic disease caused by microscopic, thread-like roundworms

What are lymphoid tissues?

Connective tissues dominated by lymphocytes.

What are lymphoid nodules?

Densely packed lymphocytes located within areas of areolar tissue.

Where do lymphoid nodules occur?

Deep to the epithelia of the respiratory, digestive, urinary, and reproductive tracts, and within lymphoid organs such as lymph nodes and spleen.

Lymph Nodules within the Wall of the Digestive Tract

What is MALT?

Mucosa-associated lymphoid tissue that protects the epithelia of the digestive, respiratory, urinary, and reproductive systems.

What are examples of MALT?

Peyer’s patches, the appendix, and tonsils.

What are tonsils?

Clusters of lymphatic tissue beneath mucous membranes lining the nose, mouth, and pharynx.

What are the three groups of tonsils?

Pharyngeal, palatine, and lingual tonsils.

Where are the pharyngeal tonsils located?

Near the opening of the nasal cavity into the pharynx.

Where are the palatine tonsils located?

Near the opening of the oral cavity into the pharynx.

Where are the lingual tonsils located?

On the posterior surface of the tongue.

How do tonsils protect the body?

Lymphocytes and macrophages in the tonsils protect against harmful substances and pathogens entering through the nose or mouth.

What characterizes lymphatic organs?

They contain clusters of lymphocytes and other cells, such as macrophages, within a framework of short branching connective tissue fibers.

What happens to lymphocytes in lymphatic organs during exposure to foreign agents?

They proliferate and are sent through the blood to the site of invasion.

What are lymph nodes?

Small, bean-shaped lymphatic organs distributed throughout the body along lymphatic pathways.

What are the three major superficial regions where lymph nodes cluster?

Inguinal, axillary, and cervical regions.

How are lymph nodes organized?

They are surrounded by a connective tissue sheath and divided into compartments containing lymph nodules separated by lymph sinuses.

What are lymph nodules within lymph nodes composed of?

Dense masses of lymphocytes and macrophages separated by lymph sinuses.

What is the difference between afferent and efferent lymphatic vessels?

Afferent vessels carry lymph into a lymph node, while an efferent vessel carries lymph away from the node at the hilum.

Where do afferent lymphatic vessels enter lymph nodes?

They enter on the convex side of the lymph node.

Where does the efferent lymphatic vessel leave a lymph node?

It leaves at the hilum.

What is the thymus?

A soft, bi-lobed lymphatic organ involved in processing and maturation of T lymphocytes.

Where is the thymus located?

Anterior to the ascending aorta and posterior to the sternum.

What happens to the thymus after puberty?

It decreases in size.

What are the main functions of the thymus?

Processing and maturation of T lymphocytes and production of thymosins.

What happens to T cells while they are in the thymus?

They mature and do not respond to pathogens and foreign agents while in the thymus.

What happens to T cells after maturation in the thymus?

They enter the blood and travel to other lymphatic organs to help defend the body.

What are thymosins?

Hormones produced by the thymus that stimulate lymphocyte maturation in other lymphatic organs.

Where is the spleen located?

In the upper left abdominal cavity, beneath the diaphragm and posterior to the stomach.

What is the spleen's relationship to lymph nodes?

It is similar in structure to lymph nodes but is much larger and is the largest lymphatic organ.

How is the spleen structurally organized?

A connective tissue capsule surrounds it and extends inward to divide it into lobules.

What are the two types of tissue in the spleen?

White pulp and red pulp.

What is white pulp?

Lymphatic tissue consisting mainly of lymphocytes located around arteries.

What is red pulp?

Venous sinuses filled with blood and cords of lymphatic cells.

What are the main functions of the spleen?

Filters blood, removes old and damaged RBCs, produces lymphocytes, and stores blood in its sinuses.

How does the spleen filter blood?

Lymphocytes respond to pathogens while macrophages engulf debris, damaged cells, and large particles.

What happens to old and damaged RBCs in the spleen?

They are removed from the blood.

When does the spleen produce lymphocytes?

Especially in response to invading pathogens.

How does the spleen act as a blood reservoir?

Blood is stored in its sinuses and can be squeezed into general circulation during an emergency.