Comprehensive Lymphatic and Cardiovascular System: Structure, Function, and Immunity

What is the lymphatic system?

A collection of cells and biochemicals traveling in lymphatic vessels, closely associated with the cardiovascular system.

What are the three main functions of the lymphatic system?

1. Transport excess interstitial fluid back to the bloodstream. 2. Absorb lipids from the digestive system and transport them to the bloodstream. 3. Defend the body against disease.

What does the term 'immune system' refer to?

It refers to the many cells of the lymphatic system that provide defense against disease and permanent immunity against future infections.

What is the pathway of lymphatic fluid?

Lymphatic capillaries -> afferent lymphatic vessels -> lymph nodes -> efferent larger lymphatic vessels -> lymphatic trunks -> lymphatic collecting ducts -> subclavian veins in thorax.

What are lymphatic capillaries?

Microscopic, closed-end tubes that are networks parallel to blood capillaries, allowing tissue fluid to enter and become lymph.

What are the three layers of lymphatic vessels?

1. Inner layer: endothelial lining. 2. Middle layer: smooth muscle and elastic fibers. 3. Outer layer: connective tissue.

What is the function of semilunar valves in lymphatic vessels?

They allow one-way flow of lymph through the vessels.

What are the two types of lymphatic collecting ducts?

1. Thoracic duct (large) - drains the majority of the body. 2. Right lymphatic duct (small) - drains the upper right portion of the body.

What is the thoracic duct?

The longer and wider of the two ducts, beginning as cisterna chyli and draining into the left subclavian vein.

What is the role of tissue fluid in the lymphatic system?

Tissue fluid, formed from capillary blood pressure, enters lymphatic capillaries and is transformed into lymph.

How does lymph formation occur?

Filtration from plasma exceeds reabsorption, increasing hydrostatic pressure in interstitial spaces, forcing fluid into lymphatic capillaries.

What mechanisms aid lymph flow?

1. Muscle activity compresses lymphatic vessels. 2. Respiratory processes create pressure changes. 3. Smooth muscle contractions in larger vessels. 4. Valves prevent backflow.

What is mucosa-associated lymphoid tissue (MALT)?

Unencapsulated lymphatic tissue found in the digestive, respiratory, urinary, and reproductive tracts.

What are lymph nodes?

Encapsulated lymphatic organs that filter pathogens from lymph and contain lymphocytes and macrophages.

Where are lymph nodes commonly located?

Cervical region, axillary region, supratochlear region, inguinal region, pelvic cavity, abdominal cavity, thoracic cavity.

What are the primary functions of lymph nodes?

1. Filter potentially harmful particles from lymph. 2. Immune surveillance by macrophages and lymphocytes.

What is the composition of tissue fluid?

Similar to blood plasma, containing water, dissolved nutrients, gases, and hormones, but lacking large plasma proteins.

What prevents the accumulation of excess tissue fluid?

The formation of lymph from tissue fluid entering lymphatic capillaries prevents edema.

What is the role of skeletal muscle contraction in lymphatic flow?

It compresses lymphatic vessels, facilitating the movement of lymph.

What is the effect of physical exercise on lymphatic flow?

Lymphatic flow is highest during physical exercise.

What activates monocytes in the immune system?

Macrophages activate the monocytes.

What is produced by red bone marrow and lymph nodes?

Lymphocytes are produced.

How do lymphocytes respond to pathogens?

They attack pathogens in lymph nodes.

What is the function of macrophages?

Macrophages engulf foreign substances, damaged cells, and debris.

Where is the thymus located?

In the mediastinum.

What is the structure of the thymus?

It is a soft, bilobed gland divided into lobules.

What do the lobules of the thymus contain?

Lymphocytes made from progenitor cells in red bone marrow.

What are thymocytes?

Inactive cells in the thymus that may mature into T lymphocytes.

What hormone is produced in the thymus to aid T cell maturation?

Thymosin.

What happens to the thymus during puberty?

It shrinks and becomes smaller in adults.

What replaces lymphatic tissue in the elderly?

Adipose and connective tissue.

What is the largest lymphatic organ?

The spleen.

What are the two types of tissues found in the spleen?

White pulp (lymphocytes) and red pulp (red blood cells, lymphocytes, and macrophages).

What is one function of the spleen?

It filters blood and breaks down old red blood cells.

What are pathogens?

Disease-causing agents such as bacteria, viruses, protozoa, and fungi spores.

What is immunity?

The ability to prevent pathogen entry or destroy pathogens that enter the body.

What are the two immune mechanisms?

Innate (nonspecific) defenses and adaptive (specific) defenses.

What characterizes innate defenses?

They are general defenses that protect against many types of pathogens.

What characterizes adaptive defenses?

They are acquired over time and target specific antigens.

What is a mechanical barrier in the immune system?

Skin and mucous membranes that prevent the entrance of pathogens.

What is the first line of defense in the immune system?

Mechanical barriers such as skin and mucous membranes.

What are the signs of inflammation?

Local redness, swelling, heat, and pain.

What causes redness during inflammation?

Vasodilation.

What is the role of enzymes in body fluids regarding pathogens?

They provide a chemical barrier to pathogens.

What do interferons do?

Block viral replication, act against tumor growth, and stimulate phagocytosis.

What are defensins?

Peptides produced by neutrophils that cripple microbes by making openings in cell membranes.

What are collectins?

Proteins that protect against many bacteria, yeast, and some viruses.

What is the function of complement proteins?

Stimulate inflammation, attract phagocytes, and enhance phagocytosis.

What type of cells are natural killer (NK) cells?

A small population of lymphocytes that defend against viruses and cancer cells.

How do NK cells attack infected or cancerous cells?

By secreting cytolytic substances called perforins that lyse cell membranes.

What is phagocytosis?

The process by which phagocytic cells remove particles from blood and tissues.

Which cells are the most active phagocytes?

Neutrophils and monocytes.

What is chemotaxis in the context of phagocytosis?

The attraction of phagocytic cells to injury sites by chemicals from damaged tissue.

What do monocytes become when they leave the blood?

Macrophages, which can be free or fixed in tissues.

What is the mononuclear phagocytic system?

A system consisting of monocytes and macrophages in the body.

What triggers a fever in the immune response?

Lymphocytes proliferate and secrete interleukin-1 (IL-1) in response to infection.

What is the role of IL-1 in fever?

It raises the thermoregulatory set point, causing an increase in body temperature.

How does elevated body temperature affect microbial growth?

It inhibits microbial growth and makes iron unavailable for bacteria and fungi.

What are the two types of adaptive immune responses?

Cellular immune response and humoral immune response.

What are antigens?

Non-self molecules that can evoke an immune response.

What distinguishes self from non-self in the immune system?

The ability of the immune system to recognize molecules that are part of the body versus foreign molecules.

What are haptens?

Small molecules that are not antigenic by themselves but can evoke an immune response when combined with a larger molecule.

Where are T lymphocytes produced?

In the red bone marrow and then mature in the thymus.

What percentage of circulating lymphocytes are T cells?

70-80%.

What is required for T cell activation?

Antigenic fragments must be attached to antigen-presenting cells (APCs).

What are the two classes of MHC antigens?

Class 1 MHC antigens are on all body cells except RBCs, and Class 2 MHC antigens are on APCs and activated T cells.

What are the types of specialized T cells?

Helper T cells, cytotoxic T cells, and memory T cells.

What do B cells produce in response to antigen activation?

Antibodies or immunoglobulins.

What is the humoral immune response?

An antibody-mediated immune response where antibodies are carried by blood to the infection site.

What are the three ways antibodies respond to antigens?

Direct attack, activation of complement, and stimulation of inflammation.

What is the primary immune response?

The response produced by the first encounter with an antigen, with antibodies appearing in 5 to 10 days.

What is the secondary immune response?

The response to subsequent exposure to an antigen, producing high concentrations of antibodies in 1 to 2 days.

What is the difference between passive and active immunity?

Passive immunity is temporary and does not involve antigen exposure, while active immunity is permanent and involves an immune response.

What is naturally acquired immunity?

Immunity that occurs naturally, such as recovering from a disease or receiving antibodies from the mother during pregnancy or breastfeeding.

What is artificially acquired immunity?

Immunity that occurs through medical intervention, such as receiving a vaccine or injection.

What is passive immunity?

Temporary immunity gained from receiving antibodies without direct exposure to the disease, resulting in no long-term immune response.

What is active immunity?

Permanent immunity that results from direct exposure to a disease, leading the body to create a strong immune response and memory cells.

What are the four types of hypersensitivity reactions?

Type I (immediate-reaction), Type II (antibody-dependent cytotoxic reaction), Type III (immune-complex reaction), and Type IV (delayed-reaction hypersensitivity).

What characterizes Type I hypersensitivity?

It involves an immediate allergic reaction where IgE antibodies are produced against a specific allergen, leading to histamine release.

What is an example of a Type II hypersensitivity reaction?

A transfusion reaction, where antibodies bind to specific cell antigens, causing phagocytosis and complement lysis of the antigen.

What occurs during a Type III hypersensitivity reaction?

Antigen-antibody complexes form and deposit in tissues, causing damage via phagocytosis and complement-binding, as seen in rheumatoid arthritis.

What is Type IV hypersensitivity?

A delayed reaction that occurs after repeated skin exposure to an allergen, activating T cells that release chemicals causing eruptions and inflammation.

What tissues and organs can be transplanted?

Bone marrow, cornea, kidney, liver, pancreas, heart, skin, and lungs.

What happens during a tissue rejection reaction?

The recipient's immune system recognizes the donor's tissues as foreign and attempts to destroy them, resembling a cellular immune response.

Why is matching MHC antigens important in transplantation?

The greater the antigenic difference between donor and recipient, the stronger and faster the rejection reaction will occur.

What role do immunosuppressive drugs play in transplantation?

They are used to prevent the rejection of transplanted tissues or organs.

What is autoimmunity?

An attack by the immune system against its own tissues, where the body produces autoantibodies and cytotoxic T cells attack its own cells.

What are some changes in the immune system as one ages?

The thymus gland shrinks, T cell numbers decrease, antibody responses slow, and there is a higher risk for infection and cancer.

What is HIV?

A virus that breaks down immune system function, potentially remaining silent for years before progressing to AIDS and leading to opportunistic infections.

How does HIV affect the immune system?

HIV attacks macrophages and Helper T cells, compromising the immune response.

What are the main components of the cardiovascular system?

The heart and blood vessels.

What is the function of the heart?

It is a muscular pump that generates force to transport respiratory gases, nutrients, and waste throughout the body.

What is the role of arteries in the cardiovascular system?

Arteries transport blood away from the heart.

What is the role of veins in the cardiovascular system?

Veins transport blood back to the heart.

What is the function of capillaries?

Capillaries perform the exchange of nutrients, gases, and waste between blood and tissues.

What are the two main circuits of the cardiovascular system?

The pulmonary circuit and the systemic circuit.

What does the pulmonary circuit do?

It carries oxygen-poor blood from the heart to the lungs to drop off carbon dioxide and pick up oxygen.

What does the systemic circuit do?

It transports oxygen-rich blood and nutrients to body cells and removes waste, returning blood to the heart.

What is the average size and location of the heart?

The heart is about the size of a fist, approximately 14 cm long and 9 cm wide, located in the thoracic cavity behind the sternum.

What are the three layers of the heart wall?

Epicardium, myocardium, and endocardium.