Lymphatic & Immunity System

What is the relationship between the lymphatic system and the cardiovascular system?

The lymphatic system is closely associated with the cardiovascular system and acts as a "fix" for cardiovascular leakage by collecting excess fluid that leaks from capillaries due to high pressure.

What causes fluid to leak from capillaries in the cardiovascular system?

High pressure at the capillaries of the cardiovascular system causes fluid to leak out of the blood vessels into the surrounding tissues between cells.

What is the purpose of fluid leakage at capillaries?

The leaked fluid carries nutrients from the arterial end of capillaries to body cells and delivers oxygen to tissues.

What happens to the leaked fluid after nutrient delivery?

Much of the fluid is reabsorbed at the venous end of capillaries, but not all of it can be reabsorbed.

How much fluid is lost per day that cannot return directly to the cardiovascular system?

Approximately 3 liters of fluid per day cannot return directly to the cardiovascular system.

What are lymphatic capillaries?

Tiny microscopic blood vessels that pick up leaked fluid from the cardiovascular system.

What is edema?

Swelling caused by accumulation of excess fluid in tissue spaces.

How does the lymphatic system prevent edema?

The lymphatic vessels collect all the extra leaked fluid and return it back to the cardiovascular system, preventing fluid accumulation.

Where do lymphatic vessels ultimately drain?

Lymphatic vessels ultimately drain back into the bloodstream at the subclavian veins.

What structures do lymphatic vessels pass through before reaching the subclavian veins?

Lymphatic vessels pass through lymph nodes and other organs that filter harmful substances and defend the body.

What is the thoracic duct?

The major vessel into which lymphatic fluid is drained before returning to the cardiovascular system.

What are the three major functions of the lymphatic system?

1) Collect and return fluid that leaked from the cardiovascular system, 2) Transport large fat molecules from intestines to bloodstream, 3) Provide immune defense.

What type of fatty acids does the lymphatic system transport?

Long-chain fatty acids from the intestines to the bloodstream.

What is the structure of lymphatic capillaries?

They are dead-end vessels (cul-de-sacs) made up of simple squamous epithelium with overlapping edges that create a one-way valve system.

How do lymphatic capillaries maintain their one-way valve structure?

Tiny microscopic collagen filaments (like ligaments) hold the edges of cells and attach to the matrix of surrounding connective tissue.

What is tissue fluid called once it enters a lymphatic capillary?

It is called "lymph."

What is interstitial fluid?

Fluid found outside the lymphatic capillary in tissue spaces; also called tissue fluid.

What happens as lymphatic capillaries merge together?

Multiple capillaries join together, the diameter increases, and they become lymphatic vessels and then lymphatic ducts.

Where are lymph nodes typically found?

In groups or bunches in specific regions such as the axillary region (armpit), cervical region (neck), and other locations throughout the body.

What are lacteals?

Special lymphatic capillaries that drain the wall of the intestine.

What do lacteals collect?

Long-chain fatty acids from digested food that cannot pass through blood capillaries.

What is chyle?

The milky-white fluid within lacteals that contains fluid plus fatty molecules (long-chain fatty acids).

Can short and medium-chain fatty acids pass through intestinal walls?

Yes, they can pass through intestinal walls into blood capillaries.

What are the three layers of lymphatic vessels?

Tunica intima (innermost), tunica media (middle), and tunica externa/adventitia (outer).

What is the tunica intima composed of?

Simple squamous epithelium and contains valves.

What is the tunica media composed of?

Smooth muscle, which allows the vessel to contract.

What is the tunica externa/adventitia composed of?

Connective tissue that provides support.

Do lymphatic vessels have valves?

Yes, lymphatic vessels have valves throughout their length to prevent backflow and ensure one-way movement toward the heart.

What is the largest lymphatic vessel in the body?

The thoracic duct (also called the left lymphatic duct).

What areas does the thoracic duct drain?

The entire left side of the body, the entire lower body (both right and left below the diaphragm), and the right side except the right upper quadrant.

Where does the thoracic duct terminate?

At the junction of the left subclavian vein and left internal jugular vein.

What areas does the right lymphatic duct drain?

The right side of the face, right side of the neck, right upper limb (right arm), and right thorax (right upper chest area).

Where does the right lymphatic duct terminate?

At the junction of the right subclavian vein and right internal jugular vein.

What is the clinical significance of lymph node removal during breast cancer surgery?

There is a 99% possibility that the patient will develop swelling (edema) in the arm because lymphatic drainage has been removed while cardiovascular leakage continues.

What is mastectomy?

Surgical removal of the breast, often performed for severe breast cancer.

What are the five factors that maintain lymph flow?

1) Respiratory movements, 2) Arterial pulsations, 3) Presence of valves, 4) Skeletal muscle contractions, 5) Osmotic pressure from absorbed nutrients.

How do respiratory movements maintain lymph flow?

When the diaphragm pushes down during breathing, pressure in the abdomen increases and pressure in the thorax decreases, creating a pressure gradient that moves lymph from high to low pressure.

How do arterial pulsations help move lymph?

When arteries pulsate, they squeeze adjacent lymphatic vessels, helping move lymph forward while valves prevent backflow.

How do skeletal muscle contractions help lymph flow?

Muscular contractions squeeze lymphatic vessels that run close to arteries and veins, similar to the muscle pump mechanism for venous return.

How does osmotic pressure from absorbed nutrients maintain lymph flow?

Large particles like long-chain fatty acids increase osmotic pressure in the lymph, drawing more fluid from tissue spaces into lymphatic vessels.

Why are lymphoid tissues and organs called "lymphoid"?

Because the dominant cell type present in these structures is the lymphocyte.

What are examples of lymphoid organs?

Lymph nodes, spleen, thymus, tonsils, and other lymphoid tissues.

What is the outer protective covering of lymph nodes called?

The capsule, made of dense connective tissue.

How is the interior of a lymph node organized?

The capsule extends inward creating partitions that divide the interior into small compartments called nodules.

What are sinuses in lymph nodes?

Spaces between nodules and beneath the capsule through which lymph flows.

What is the germinal center of a nodule?

The pale-appearing center of each nodule where lymphocytes actively divide, proliferate, and mature.

What is the cortical area of a nodule?

The darker area surrounding the germinal center that contains densely packed lymphocytes.

What cell types are found in lymph nodes?

Lymphocytes (B lymphocytes and T lymphocytes) and macrophages (derived from monocytes).

What type of connective tissue is found within lymph nodes?

Reticular connective tissue containing reticular fibers that form a supportive network.

How are lymph nodes named?

Based on their region in the body (e.g., cervical lymph nodes in neck, axillary in armpit, inguinal in groin).

Can you feel normal lymph nodes?

No, normal lymph nodes should not be palpable. If they can be felt, they are enlarged.

What does it mean if lymph nodes are palpable?

It means they are enlarged, inflamed, and have been actively fighting infection or disease.

What is lymphadenopathy?

General term meaning enlarged lymph nodes; "lymphaden-" refers to lymph nodes and "-pathy" means disease or abnormality.

What is lymphadenitis?

Inflammation of lymph nodes; "lymphaden-" refers to lymph nodes and "-itis" means inflammation, resulting in enlarged, tender lymph nodes.

What is lymphangitis?

Inflammation of lymphatic vessels (not nodes); "lymphangi-" refers to lymphatic vessels and "-itis" means inflammation.

What is lymphangiectasis?

Enlargement or dilation of lymphatic vessels; "lymphangi-" refers to lymphatic vessels and "-ectasis" means dilation or expansion.

What are the two critical functions of lymph nodes?

1) Maturation of lymphocytes into immunocompetent cells, 2) Conversion of monocytes to macrophages.

What are plasma cells?

Mature lymphocytes that produce and secrete antibodies.

What are cytotoxic cells?

Mature lymphocytes that directly attack and destroy infected or abnormal cells.

What are macrophages?

Large immune cells converted from monocytes that are effective at phagocytosis (eating pathogens, bacteria, viruses, dead cells, foreign particles, and debris).

What is the hilum of a lymph node?

The indentation or concave area on one side of the lymph node where vessels enter and exit.

What vessels pass through the hilum?

Efferent lymphatic vessels (carrying lymph OUT) and blood vessels (arteries and veins).

What are afferent lymphatic vessels?

Vessels located on the outer convex surface that bring lymph TO the lymph node.

What does "afferent" mean?

"Bringing toward" - similar to afferent neurons that bring signals to the central nervous system.

What does "efferent" mean?

"Carrying away from" - efferent vessels carry lymph out of the lymph node.

Describe the flow pattern of lymph through a node.

1. Lymph enters through multiple afferent vessels on the convex surface

2. flows through sinuses within the node where it gets filtered

3. exits through fewer efferent vessels at the hilum.

What are capsular sinuses?

Spaces located under the capsule of the lymph node.

What are medullary sinuses?

Spaces located in the medulla (central region) of the lymph node.

Where is the spleen located?

In the left upper quadrant of the abdomen (left hypochondriac region), between ribs 8-11.

What is the clinical significance of left rib fractures 8-11?

If a patient has fractures to ribs 8-11 on the left side, there should be concern about possible splenic injury.

What structures are near the spleen anatomically?

Above: diaphragm; In front of: left kidney; Behind: stomach (fundus) and colon (splenic flexure).

What are the dimensions of the spleen?

12 cm × 7 cm × 4 cm.

How is the spleen described physically?

Soft, dark red, encapsulated ovoid structure with dark red color due to extensive blood supply.

What artery supplies the spleen?

The splenic artery, a branch from the celiac trunk (from the aorta).

Why is splenic laceration dangerous?

Due to the rich blood supply, a lacerated (torn) spleen can cause extensive bleeding that may be fatal without emergency intervention.

What is a splenectomy?

Surgical removal of the spleen, which can be performed via open surgery or laparoscopic surgery.

What are the two main tissue types in the spleen?

White pulp (central white ball containing lymphocytes) and red pulp (surrounding red area filled with red blood cells).

What are the functions of the spleen?

1) Hematopoiesis (RBC production), 2) Blood reservoir, 3) Lymphoid tissue functions (maturation of lymphocytes, fighting infection, converting monocytes to macrophages), 4) Destruction of aged RBCs.

What is the spleen's role as a blood reservoir?

It stores blood and constantly filters blood passing through.

What is splenomegaly?

Enlargement of the spleen.

How does splenomegaly cause anemia?

An enlarged spleen pulls more blood and RBCs into storage, potentially causing anemia. Removing the enlarged spleen returns blood counts to normal.

What is the largest lymphoid organ?

The spleen.

Where is the thymus gland located?

In the mediastinum (central chest cavity).

How does the thymus change with age?

It is present and increases in size throughout childhood, begins to atrophy (shrink) at puberty onset.

At what age would the thymus be largest?

In younger children (around age 5-12) compared to teenagers (13+) or adults.

How many lobes does the thymus have?

Two lobes.

What are Hassall's corpuscles?

Characteristic concentric layered structures found within the thymus.

What is the function of the thymus gland?

Maturation and education of T-lymphocytes (T-cells), teaching them to distinguish self from non-self, critical for cell-mediated immunity.

What are the three types of tonsils?

1) Palatine tonsils, 2) Pharyngeal tonsil (adenoid), 3) Lingual tonsils.

Where are palatine tonsils located?

On either side of the throat (what people commonly refer to as 'the tonsils').

Where is the pharyngeal tonsil located?

In the posterior nasopharynx (single tonsil).

Where are lingual tonsils located?

At the base of the tongue.

What is a tonsillectomy?

Surgical removal of palatine tonsils.

What is an adenoidectomy?

Surgical removal of the pharyngeal tonsil (adenoid).

What is T&A?

Tonsillectomy and adenoidectomy performed together.

What is the function of tonsils?

First line of defense against inhaled or ingested pathogens; part of mucosa-associated lymphoid tissue (MALT).

Where do T-lymphocytes originate and mature?

Originate in bone marrow and mature in the thymus gland.

What are the four types of T-cells?

1) Cytotoxic T-cells, 2) Helper T-cells, 3) Suppressor T-cells, 4) Memory T-cells.

What is the function of cytotoxic T-cells?

Directly attack and lyse (burst) infected cells, cancer cells, and foreign tissue.

What is the function of helper T-cells?

Activate B-cells and other T-cells; coordinate immune responses.