lecture 13 Flashcards
Describe the major functions of the lymphatic system.
Fluid balance - The lymphatic system helps maintain fluid balance by collecting excess fluid (lymph) from tissues and returning it to the bloodstream. This prevents fluid accumulation (edema) in tissues.
Immune defense - It plays a key role in the body’s immune system. Lymph nodes and other lymphatic organs filter lymph, trapping harmful substances like bacteria, viruses, and cancer cells. They contain immune cells (e.g., lymphocytes) that help fight infections.
Absorption of fats - In the digestive system, the lymphatic system absorbs and transports fatty acids and fat-soluble vitamins (A, D, E, and K) from the intestines into the bloodstream through the lymph.
Transport of white blood cells - The lymphatic vessels carry white blood cells, particularly lymphocytes, which are essential for the immune response, throughout the body.
Filtration of lymph - Lymph nodes act as filters to remove foreign particles, pathogens, and dead cells from lymph before it is returned to the circulatory system
o Lymph
Lymph is a clear, colorless fluid that circulates through the lymphatic system, a network of vessels and organs in the body. It plays a key role in the immune system and fluid balance. Here’s a breakdown of what lymph is and its functions: immune response, fluid balance, absorption of fats, waste removal.
o Interstitial fluid
the fluid that fills the spaces between the cells of tissues in the body. It surrounds and bathes the cells, providing them with nutrients, oxygen, and a medium for waste removal. It plays a crucial role in maintaining cellular environment stability.
plasma
A yellowish liquid primarily made of water that has proteins and electrolytes, hormones, gases, nutrients, and waste products. Plasma does not have any cellular components. It is the medium for transporting nutrients, waste products, hormones, and gases.
whole blood
Whole blood is the liquid and cellular components of blood. The plasma, RBCs, WBCs, and platelets. The plasma portion makes up about 55%, the cells make up 45%.
structure and function of lymphatic vessel
primary function is to return excess fluid to the bloodstream, immune response, and fat transport. These vessels transport lymph. Have thin, muscular, more permeable walls, and have one-way valves to prevent backflow. Its flow is slow, low-pressure, relies on external movements like muscle contractions. Has no central pump and relies on muscle contractions and valves; has the presence of capillaries to absorb the interstitial fluid.
structure and function of blood vessels
primary function is to transport oxygen, nutrients, waste, and to regulate circulation. Transports blood, has thicker, muscular, elastic, varying layered walls. The arteries do not really have valves but the veins do prevent backflow. It flows fast, high-pressure and driven by the heart. It has a pump to pump blood through the circulatory system and has blood capillaries where nutrient and gas exchange occur.
path of lymph circulation
o Lymph begins in the lymphatic capillaries, then flows into the lymphatic vessels where it progressively moves from small ones to larger ones. The lymph then filters through to pass through the different lymph nodes which contain lymphocytes and immune cells to help filter things out. The lymph then flows into the larger lymphatic trunks
o then goes to either the right lymphatic duct, or the thoracic duct
o Then the lymph returns to the bloodstream
the lymphatic trunks
Jugular trunk – drains lymph from the head and neck
Subclavian trunk – drains lymph from the upper limbs
Bronchomediastinal trunk – brains lymph from the thoracic organs and trunk
intestinal trunk – drains lymph from the abdominal area, particularly the intestines
lumbar trunks – drains lymph from the lower limbs and lower abdomen
right lymphatic duct and thoracic duct
right lymphatic duct - smaller and drains lymph from the right side of the head, right arm, and right side of the chest. It empties into the right subclavian vein at the junction where the right internal jugular vein meets it.
The thoracic duct is the largest lymphatic vessel and drains lymph from the rest of the body: the left side of the head, left arm, left side of the chest, abdomen, and both lower limbs. It begins as the cisterna chyli (a dilated sac at the level of the second lumbar vertebra) and ascends along the spine. It empties into the left subclavian vein, at the junction where the left internal jugular vein meets the subclavian vein.
o Key components of lymphatic tissues and organs:
Lymph nodes, spleen, thymus, Mucosa-associated lymphoid tissue (MALTs). Also the lymphatic vessels
o Cellular composition of lymphatic tissue
Lymphocytes (T cells, helper T cells, and cytotoxic T cells; B cells, plasma cells, memory B cells), macrophages, dendritic cells, reticular cells)
correlations between lymphatic cells, tissues, and organs
Immune surveillance and responses, fluid balance, fat absorption, filtration and cleansing
The structure and cellular composition of lymphatic tissue are intricately designed to support the system’s primary functions: immune surveillance, fluid balance, and fat absorption. Lymphatic organs like lymph nodes, the spleen, and mucosal lymphoid tissue provide locations where immune cells can interact with pathogens. Lymphocytes, macrophages, dendritic cells, and reticular cells are all vital for immune responses, while lymphatic vessels ensure fluid and nutrient balance. Together, these components enable the lymphatic system to protect the body against infections, maintain fluid homeostasis, and support digestion.
structure, function, and major locations of lymph nodes
Lymph nodes are small, oval or bean-shaped structures, typically ranging from 1-25 mm in size. They are surrounded by a fibrous capsule, with trabeculae (fibrous tissue extensions) inside to give them structural support. Help with immune filtration, immune cell activation, and antibody production. Are in concentrated regions where the lymphatic vessels converge. (are in cervical nodes, axillary nodes, inguinal nodes, mesenteric nodes
structure, function, and locations of thymus
The thymus is a bilobed, flat organ located in the upper chest (mediastinum) behind the sternum. It is larger in children and shrinks in size after puberty, eventually becoming replaced with adipose tissue in older adults. Helps with T cell maturation and self-tolerance development. Is in the mediastinum.
structure, function, and location of the spleen
The spleen is a large, oval-shaped organ, typically about the size of a fist (around 12 cm long). It is in the upper left abdomen, just below the diaphragm. Helps with blood filtration, immune responses, is a blood reservoir. Is in the upper left quadrant just beneath the diaphragm and adjacent to the stomach.
structure, function, and location of lymphatic nodules
o Lymphatic nodules are small, localized clusters of lymphoid tissue, primarily composed of lymphocytes (especially B cells and T cells) and macrophages. They are typically non-encapsulated masses of lymphatic tissue that are organized around central regions known as the germinal centers (rich in B cells). The germinal center is where B cells proliferate and differentiate, particularly when they are activated by antigens. Lymphatic nodules are most abundant in mucosal areas where the body is exposed to potential pathogens. These include the respiratory, digestive, and urogenital tracts. Some nodules are discrete, while others are organized into larger aggregates, like the tonsils or Peyer’s patches in the intestines.
structure, function, and locations of MALTs
MALT refers to the collection of lymphoid tissues located in mucosal membranes, which are strategically positioned to protect the body’s surfaces from pathogens entering through mucosal barriers (e.g., in the digestive, respiratory, and urogenital systems).
MALT is composed of lymphoid nodules scattered throughout mucosal membranes. It lacks a fibrous capsule, which differentiates it from lymph nodes. MALT can be found in two forms:
Diffuse MALT: Lymphoid cells are scattered without a defined structure.
Organized MALT: Larger clusters or aggregates of lymphatic tissue (e.g., tonsils, Peyer’s patches).
Functions include: immune surveillance, acts as the first line of defense, IgA production.
- Located in Peyer’s patches (intestines), in the tonsils, bronchial-associated lymphoid tissue, urogenital associated lymphoid tissue
structure, function, and location of tonsils
Tonsils are made up of lymphoid tissue and are characterized by multiple crypts (invaginations) on their surface that help trap pathogens. Inside the crypts are germinal centers, where lymphocytes (B cells) proliferate and mature. The tonsils are encapsulated, but they have an incomplete capsule, allowing them to interact directly with the surrounding tissues.
Functions include: acting as a defense against inhaled or ingested pathogens, helping with the activation of immune responses.
We have three sets: the palatine tonsils, the pharyngeal tonsils (adenoids), and the lingual tonsils.
