Lymphatic System and Lymphocytes

The lymphatic system collects fluid from tissues and returns it to the venous side of the blood.
If fluid can't be collected and returned, it leads to fluid accumulation in peripheral tissues, causing tissue swelling known as peripheral edema.
One cause of tissue swelling is a blockage in the lymphatic system.

The lymphatic system absorbs lipids, one of the three forms of nutrients (carbohydrates, proteins, and lipids).
Carbohydrates and proteins are absorbed through the circulatory system via capillaries.
Lipids are absorbed in the intestine using lacteals, lymphatic system structures.

The lymphatic system is a major component of the immune system, consisting of cells, tissues, and organs.
Lymphocytes, a type of white blood cell, are part of the lymphatic system.

Lymphatic fluid, or lymph, is the fluid collected from peripheral tissues and returned to the circulatory system.
The lymphatic system includes cells, tissues, organs, and lymph.

Tonsils are collections of lymphatic tissues in the oral cavity and pharynx.
Lymph nodes are lymphatic system nodes found throughout the body, interconnected by lymphatic vessels.
- Cervical lymph nodes are in the cervical region.
- Axillary lymph nodes are in the armpit region.
- Inguinal lymph nodes are in the groin region.
The thymus gland, located posterior to the sternum and anterior to the great vessels of the heart, is part of the immune system.
- It produces thymosin, which regulates the immune system.
The spleen is also part of the lymphatic system.

During ventricular systole, the heart pumps a stroke volume (approximately $30$ mL) of blood per contraction.
Cardiac output is calculated by counting stroke volume over $60$ seconds.
Blood travels from the heart through the ascending aorta, aortic arch, thoracic aorta, and abdominal aorta.
Fluids are collected from tissues as lymph and returned to the venous side of the blood through the lymphatic system.

Lymphatic capillaries move lymph fluid towards lymph nodes.
Lymph is ultimately drained into two major vessels: the right lymphatic duct and the thoracic duct.
- Lymph from the right side of the head, right side of the neck, right side of the chest, and right upper extremity drains into the right lymphatic duct.
- Lymph from the left side of the head, left side of the neck, left side of the thorax, left upper extremity, entire abdomen and pelvis, and both lower extremities drains into the thoracic duct (also known as the left lymphatic duct).
To summarize the areas drained by each duct:
- Right Lymphatic Duct: Right half of the head, right half of the neck, right half of the thorax, and right upper extremity.
- Thoracic Duct: The remainder of the body, including the left halves of the head, neck and thorax, the left upper extremity, the abdomen and pelvis, and both lower extremities.

The right lymphatic duct drains directly into the right subclavian vein.
The thoracic duct drains into the junction between the left internal jugular vein and the left subclavian vein.
Remember: Veins merge, arteries branch.

The thoracic duct starts in the lower aspect of the thorax, where the thorax meets the abdomen.
Between the T12 and L1 vertebrae, there is a sac called the cisterna chyli, which is the start point of the thoracic duct.
The thoracic duct empties into the junction of the left internal jugular vein and the left subclavian vein.

Pre-B cells and pre-T cells are immature cells produced in the bone marrow.
- Pre-B cells mature into B cells in the red bone marrow.
- Pre-T cells migrate to the thymus gland to mature into T cells.
Mature B cells (B lymphocytes) and T cells (T lymphocytes) are then sent to different parts of the lymphatic system (e.g., spleen, lymph nodes) to fight infections.
Surface antigens are found on normal cells, referred to as self-antigens (e.g., surface antigen A, surface antigen B, surface antigen Rh).
Non-self antigens are found on infections caused by bacteria, viruses, or fungi, which the body does not recognize as its own cells.