LYMPHATIC SYSTEM

Associated with the Blood and Cardiovascular System

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Lymphatic-System-F11

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course-handouts

Lymphatic System

Lymph Fluid

Lymph Vessels

Lymph Nodes

Four Organs

Tonsils

Spleen

Thymus Gland

Peyer’s Patches

Functions

Drain from tissue spaces, protein-containing fluid

that escapes from the blood capillaries

Transport fats from the digestive tract to the blood

Produce lymphocytes

Develop Immunities

Interstitial Fluid

Blood pressure forces some of the blood plasma

through the single-celled capillary walls

Interstitial Fluid is in the spaces between cells

Most is reabsorbed into the capillaries

Some fluid is not and must be drained from the

tissue spaces to prevent swelling or Edema.

Lymphatic Capillaries – drain this fluid

Lymph is the fluid when it is in the vessels

Fat Absorption

Lacteals – lymphatic vessels in the villi of the small

intestine that absorb fats and transport them to the

blood.

Looks milky because of the fat content and is called

chyle.

Lymphatic Vessels

Lymph Capillaries

Larger and more permeable than blood capillaries

Closed at one end

Occur singly or in extensive plexuses

Lymphatic Capillaries

Lymphatics

Combined capillaries

Larger

Beaded appearance

Similar to veins, but thinner walls and more valves

One way valves to prevent backflow

Lymph goes in one direction only

Have lymph nodes at various intervals

All Lymphatics converge

Thoracic Duct – the main collecting channel, Left

Lymphatic Duct

Right Lymphatic Duct

Lymph Nodes or Lymph Glands

Regions of aggregations – groin, armpits, neck

Oval to bean-shaped structures found along the

length of lymphatics

1 to 25 mm in length

Look like small seeds or almonds

Framework consists of the capsule, hilum and

trabeculae

Lymph Node

Structure of a Node

Hilum - Depression on one side of the node

Efferent Lymphatic Vessels leave

Nodal artery enters

Nodal vein leaves

Covered by a Capsule of fibrous connective tissue that extends into the node

Trabeculae – divide the node internally into compartments that have lymphatic sinuses and tissue

Afferent Lymphatic Vessels – enter the node ad various sites

Lymphatic Tissue

Cortical or Lymph Nodules

6 different kinds of lymphocytes

Germinal Center – produces lymphocytes

Lymph Sinuses – spaces between the lymphatic

tissue

Network of fibers and macrophage cells

At the Node – a Sequence of Events

1. Lymph enters by an afferent lymphatic

2. Immune response is activated

3. Lymphocytes produced by germinal centers as a response to any microorganisms or foreign matter

4. Lymphocytes released into lymph

5. Eventually reach the blood and stimulate antibody production

6. Macrophages remove dead microorganisms and foreign substances by phagocytosis

Lymph Circulation

Blood to Lymph

Blood plasma is filtered by blood capillaries

Passes in-between cells to become interstitial fluid

Passes into the lymph capillaries to become lymph

Water, plasma solutes (ions & gases), nutrients, proteins, (hormones & enzymes), and waste products

Lymph drains into lymph capillaries and lymph plexuses

Drains to Lymph vessels

Heads towards Lymph Nodes

At the Node

Afferent Vessels drain lymph into the node sinuses

Microorganisms and foreign substances trigger

lymphocytes to divide and activate immune

response

Macrophages engulf foreign bodies

Efferent Vessels leave the node and go to other

nodes or join with other vessels

Unite to form Lymph Trunks

Moving the Lymph Along….

Skeletal muscle contractions compress lymph vessels

and force the lymph through the one-way vessels

Normal movement helps circulate the lymph

Breathing causes pressure changes in the thorax

that help move the lymph

Smooth muscle contraction in the lymph vessels

Swelling or edema – a blockage in the vessels

cause a back up interstitial fluid between the cells

Efferent Vessels Unite

Form Lymph Trunks

Lumbar – lower extremities, walls and viscera of pelvis, kidneys, adrenals, abdominal wall

Intestinal – stomach, intestines, pancreas, spleen, surface of liver

Bronchomediastinal – thorax, lungs, heart, diaphragm, rest of liver

Intercostal – portions of the thorax

Subclavian – upper extremities

Jugular – head and neck

Trunks to Channels to Veins

Thoracic Duct – empties into the left subclavian vein

Right Lymphatic Duct – empties into the right

subclavian vein

Completing the Cycle

Tonsils, Spleen, Thymus Gland, and Peyer’s

patches

Organs of the Lymphatic System

Tonsils – three groups

Palatine Tonsils – removed in a tonsillectomy, sides

of the oral cavity

Pharyngeal Tonsils – adenoids, near the nasal

cavity, when swollen interfere with breathing

Lingual Tonsils – back surface of the tongue at the

base

Ring of protection for the nose and oral cavity from

microorganisms

More functional in children

Spleen

Oval, 5 inches in length

Left upper corner of the abdominal cavity

Largest mass of lymphatic tissue in the body

Filters blood

Phagocytizes bacteria, worn-out platelets, and RBCs

Release hemoglobin to be recycled

Produces lymphocytes and plasma cells

Stores blood – blood reservoir

Extra blood when a hemorrhage occurs

Thymus Gland

Bi-lobed mass of tissue along the trachea behind

the sternum

Also part of the Endocrine System

Site for lymphocyte production and maturation in

the fetus and infants

Peyer’s Patches

Aggregated Lymphatic Follicles

Wall of small intestine

Similar to tonsils

Macrophages destroy bacteria to prevent infection

in the walls of the intestine

Immunity, Antigens, Antibodies, Immune Response

Cells

Resisting Infection

Immunity

The ability of the body to resist infection from disease

causing microorganisms or pathogens, damage from

foreign substances and harmful chemicals

Lymphocytes

B Lymphocytes – humoral (body fluids) immunity; produce

antibodies; circulating bacteria and viral infections; attack

the invading agents, become plasma cells in the tissues

T Lymphocytes – cellular immunity; from the thymus gland;

fungi, parasites, inside the cells viral infections, cancer cells

and foreign tissue implants

What Microorganisms ?????

Protozoans

Bacteria

Virus

Fungi

Malaria

Protozoa

Antigens and Antibodies

Antigens – foreign proteins that gain access to the

body via an opening in the skin, or through the

digestive, circulatory, urinary or reproductive

systems.

Cause immune system to produce Antibodies or

Immunoglobulins to destroy this invader

High molecular weight proteins

Active Immunity

B-Lymphocytes produce antibodies against an

antigen that they came in contact with

Naturally acquired when you come in contact with a

bacterial or viral infection

Vaccines are a killed or weakened pathogens that

stimulate antibody production

Measles, smallpox, polio, tetanus, chickenpox,

pneumonia, diphtheria, and flu

Passive Immunity

Conferred naturally when a fetus receives mother’s

antibodies through the placenta

Artificially – gamma globulin, breast milk or immune

serum

Used after exposure to hepatitis

Snakebite, botulism, or rabies

Cells of the Immune Response

B cells

Plasma Cells

Helper T Cells

Killer T Cells – kill virus invaded body cells and cancerous body cells, graft rejections

Suppressor T Cells

Memory Cells – respond to future infections with the same pathogen

Macrophages – engulf and digest antigens

Monokines and lymphokines