Anatomy & Physiology Chapter 14 Lymphatic System Part 1 Pages 385 - 390 Pathogen = any substance or microorganism that causes disease or damage to the tissues of the body Functions of the lymphatic system

1. Fluid balance 2. Lipid absorption 3. Defense

Location of fluid is indicated by a name change, but the fluid is similar and sometimes identical. Fluid in blood vessels is blood plasma. Fluid between cells in tissue is interstitial fluid Fluid in lymphatic vessels is lymph. Lymph contains water, ions, nutrients, gases, proteins, hormones, enzymes, waste products, and many white blood cells Lacteals = small lymphatic vessels in the small intestine that carry lipid rich substances from the small intestines and empty them into venous circulation. Chyle=the lipid-rich substance carried by lacteals Organs in the lymphatic system Lymph Lymphocytes Lymphatic vessels Lymph nodes Tonsils Spleen Thymus Lymphatic organs = tonsils, lymph nodes, spleen, thymus Lymphatic tissue = tissue made from lymphocytes and other cells such as macrophages Thoracic duct = the lymph duct that drains lymph and chyle from the lower half of the body, the left upper limb and the left side of the trunk and head. Right lymphatic duct = the lymph duct that drains lymph from the right upper limb and the right side of the trunk and head.

Subclavian vein = two large veins, one on each side of the neck into which the thoracic ducts empty Lymphatic system Open system – vessels do not make a closed loop but have a beginning & end All lymph vessels carry fluid towards the thoracic ducts, which are near the heart Lymph fluid is collected in capillaries which empty into increasingly larger vessels Lymph vessels have valves to prevent lymph fluid from flowing backwards Movement of lymph is caused by contraction of skeletal muscles, contraction of

smooth muscles in the lymphatic vessel wall and pressure changes in the trunk due to breathing.

Found in all tissues except the central nervous system, bone marrow and non- vascular tissue. Travel through lymph nodes Are more permeable than cardiovascular system capillaries

Lymphatic System Vessels vs. Cardiovascular System Vessels

Lymphatic System

Cardiovascular System

Open System (beginning and end) Closed System (continuous loop) Capillaries are porous enough to allow larger proteins, cells to leave

Capillaries are less porous so only smaller proteins can leave

Lymph fluid has many lymphocytes Plasma has fewer lymphocytes Lymph fluid movement due to skeletal muscle action and pressure changes due to breathing

Blood movement due to heart pumping as well as skeletal muscle action and pressure changes due to breathing

Not found in central nervous system, bone marrow, and non-vascular tissue

Found everywhere except non-vascular tissue

all vessels empty towards the heart Vessels empty in a continuous circle leading towards and away from the heart

All vessels have valves Only veins have valves

Tonsils Types Palatine tonsil = mass of lymphatic tissue on each side of the posterior opening of the

oral cavity Pharyngeal tonsil = mass of lymphatic tissue located near the internal opening of the

nasal cavity Lingual tonsil = mass of lymphatic tissue on the posterior surface of the tongue Purpose = to create a ring of lymphatic tissue around the openings of the nasal and oral

cavities that protect against potentially harmful material entering the nose and mouth

Adenoid = an enlarged pharyngeal tonsil Lymph Nodes = Encapsulated rounded structures distributed along lymphatic vessels through which lymph flows Lymphatic Nodules = small collection of lymphatic tissue that does not have a capsule and can be found in loose connective tissues in various parts of the body Peyer’s patches = lymphatic nodules in the small intestine Lymphatic sinuses = spaces between lymphatic tissue that contain a network of fibers and macrophages Two functions of lymph nodes

1. Activate the immune system by stimulating lymphocytes to divide, enter lymph, and Be released into the blood.

2. Remove pathogens from the lymph through the action of the fiber network and macrophages

Spleen Capsulated organ with trabeculae that divide it into compartments. White pulp = lymphatic tissue surrounding the arteries within the spleen Red Pulp = lymphatic tissue surrounding the veins in the spleen, flilled with

macrophages and red blood cells and enlarged capillaries Functions

filters blood, removing old platelets and red blood cells stores white blood cells removes microbes

Thymus Bilobed, encapsulated organ with trabeculae dividing the two lobes into lobules Function = the site for maturation of T-cell lymphocytes Large quantities of T-cells start maturing in the thymus but most degenerate Mature T cells enter the blood and help against pathogens