THE LYMPHATIC SYSTEM

Question 1

The lymphatic system

Answer 1

is a network of vessels that is parallel to the cardiovascular system. It is an open system, meaning: the lymphatic fluid flows only in one direction; from the tissues to the central lymph vessels, and finally into large veins.

Question 2

Structure of the Lymphatic System is made of

Answer 2

• Lymphatic fluid
• Lymphatic vessels
• Lymphocyte
• Lymphatic organs

Question 3

Lymphatic fluid

Answer 3

Composes mostly of 𝐻2𝑂, and contains also glucose and electrolytes. It is the fluid lost by the blood vessels after the exchange in the capillaries.

Question 4

Lymphatic vessels

Answer 4

• Small lymphatic vessels, which are similar in structure to the capillaries.
• Large lymphatic vessels. These are also divided into two kinds:
  • The right lymphatic duct – collects fluids from the
    right arm, the right side of the brain, the neck
    and the upper trunk. This duck drains blood into
    the right subclavian vein.
  • The thoracic duct – collect blood from the rest of
    the body. This duct drains into the left
    subclavian vein.

Question 5

lymphocyte

Answer 5

is one of the subtypes of white blood cell in the immune system. There are few main kinds of these cells:
- Natural killer cells (𝑁𝐾 cells) – 𝑁𝐾 cells are a part of the innate immune system and play
a major role in defending the host from both tumours and virally infected cells.
- 𝐵 cells (bone marrow cells) – they function in the humoral immunity component of the adaptive immune system by secreting antibodies. Additionally, 𝐵 cells present antigen.
- 𝑇 cells (thymus cells) – participate in the immune response that does not involve antibodies. There are two kinds of 𝑇 cells:
* 𝑇 helper cells – produce cytokines that direct
the immune response.
* 𝑇 cytotoxic cells – produce toxic granules that
contain powerful enzymes which induce the
death of pathogen-infected cells.

Question 6

Lymphatic organs

Answer 6

they are not necessarily connected to lymphatic vessels.
Primary lymphatic organs are organs in which white blood cells form and mature. These are the thymus and the bone marrow.
Secondary lymphatic organs are the spleen, and mucous associated lymphatic tissue (𝑀𝐴𝐿𝑇) which is found mainly in the wall of the respiratory and the digestive systems

Question 7

Functions of the lymphatic system

Answer 7

1. Fluid balance – not all the fluid that is lost from the cardiovascular system is absorbed into the
   capillaries; accesses fluid is collected by emphatic vessels and returned to the cardiovascular
   system.
2. Immune role – lymphatic organs and nodes contain lymphocytes that help the body fight
   infections.
3. Absorption of lipids – specific lymphatic vessels in the digestive system that are called lacteals
   collect fats and deliver them to the blood system.

Question 8

Lymphatic Nodes

Answer 8

Afferent lymphatic vessels enter the lymphatic nodes and efferent exit the node. This is the direction of the flow in the system. In the node there are centres of lymphocytes that can be stimulated by 𝑊𝐵𝐶
entering the lymph node and presenting information. Lymphocytes can then enter the blood circulation
through the capillary ben in the node and reach the site of infection

Question 9

𝑻 cells and 𝑩 cells

Answer 9

These are the major cellular components of the adaptive immune response. 𝑇 cells are involved in cellmediated immunity, whereas 𝐵 cells are primarily responsible for humoral immunity (relating to
antibodies).

The function of 𝑇 cells and 𝐵 cells is to recognize specific “non-self” antigens, during a process known as
antigen presentation. Once they have identified an invader, the cells generate specific responses that are
tailored to maximally eliminate specific pathogens or pathogen-infected cells.

𝐵 cells respond to pathogens by producing large quantities of antibodies which then neutralize foreign objects like bacteria and viruses. In response to pathogens some 𝑇 cells, called 𝑇 helper cells, produce cytokines that direct the immune response, while other 𝑇 cells, called cytotoxic 𝑇 cells, produce toxic granules that contain powerful enzymes which induce the death of pathogen-infected cells.

Question 10

The Spleen

Answer 10

The spleen plays a role in filtering the blood and dispose of 𝑅𝐵𝐶 It is also a storage of red and white blood.
cells and it can use them in a time of need. The spleen is similar in structure to a large lymph node. The
spleen synthesizes antibodies in its white pulp and removes antibody-coated bacteria and antibody coated blood cells by way of blood and lymph node circulation.

Question 11

Thymus

Answer 11

The thymus is a specialized primary lymphoid organ of the immune system. Within the thymus, 𝑇 cells or 𝑇 lymphocytes mature.
The thymus is composed of two identical lobes and is located anatomically in the anterior superior
mediastinum, in front of the heart and behind the sternum. Histologically, each lobe of the thymus can be
divided into a central medulla and a peripheral cortex which is surrounded by an outer capsule. The cortex and medulla play different roles in the development of 𝑇 cells.

Question 12

Bone Marrow

Answer 12

A spongey tissue that is found in the between trabecular bone and is made out of hematopoietic cells that give rise to all kinds of blood cell types.

Question 13

Pathology

Answer 13

1. Oedema – accumulation of extracellular fluid. Can be caused by the removal of lymph nodes (like in breast cancer surgery), or because of parasites – a condition called elephantiasis.
2. Enlarged lymph node – due to nearby infection or lymphoma (cancer of lymphocytes).