BISC 227 Chapter 16-1: Lymphatic System and Immunity

Lymphatic system functions

Fluid balance, lipid absorption, and defense

Fluid balance

Returns fluid from interstitial spaces to the blood stream

Lipid absorption

Absorbs from digestive system→blood stream

Lacteals

Defense

Defend against diseases

Lymphatic capillaries

Microscopic, close ended tubes

Thin walled→simple squamous epithelium

Merge into lymphatic vessels

Lymph

Interstitial fluids→lymphatic capillaries→_____

3 layers of lymphatic vessels

Inner layer, middle layer, and outer layer

Endothelial lining

Inner layer of lymphatic vessels

Smooth muscle and elastic fibers

Middle layer of lymphatic vessels

Connective tissue

Outer layer of lymphatic vessels

Semilunar valves

One-way flow in lymphatic vessels

Lymph nodes!

Larger vessels→_____→lymphatic trunks

Lymphatic trunks

Drain lymph from vessels

Named for regions they serve

Lymphatic trunk regions

Lumbar, intestinal, intercostal, bronchomediastinal, subclavian, jugular trunk

Lymphatic collecting ducts

Thoracic duct and right lymphatic duct

Thoracic duct

Longer and wider of the two ducts

Drains majority of the body

Cisterna chyli

Thoracic duct begins as a sac called ______

L. subclavian vein

Thoracic duct empties into _____

Right lymphatic duct

Much smaller than thoracic duct

Drains upper left portion of the body

R. subclavian vein

Right lymphatic duct begins in left thorax, empties in _____

1. Lymphatic capillary

2. Afferent lymphatic vessel

3. Lymph node

4. Efferent lymphatic vessel

5. Lymphatic trunk

6. Collecting duct

7. Subclavian vein

Summary of the lymphatic pathway

Tissue fluid formation

Capillary blood pressure filters water & small molecules from the plasma

The formed tissue fluid

Same composition as blood plasma

Contains water & nutrients, gases, hormones (no plasma proteins)

Tissue fluid

_____ = blood plasma - plasma proteins

Filtration from the plasma normally exceeds reabsorption

Leads to net formation of tissue fluid

Hydrostatic pressure; lymph

Net formation of tissue fluid increases the tissue fluid _____ within interstitial spaces, forcing fluid into lymphatic capillaries→_____

Edema

The process of lymph formation prevents accumulation of excess tissue fluid or _____

Low

Lymph has _____ hydrostatic pressure

Muscle activity

Influences the movement of lymph through the lymphatic vessels

How muscles influence the movement of lymph through lymphatic vessels

Contraction of skeletal muscles

Respiratory process

Smooth muscle in the larger lymphatic vessels

Valves

Prevent backflow in lymphatic vessels

Physical exercise

Lymphatic flow is highest during _____

Lymph function

Absorption of dietary fats in small intestine→bloodstream

Return of small proteins filtered by blood capillaries→bloodstream

Collection of excess interstitial fluid→bloodstream

Delivery of foreign particles to the lymph nodes

Flap-like valves between cells of lymphatic capillaries allow easy entry of tissue fluid

Lymphatic tissues and organs

Includes lymphocytes and macrophages

Mucosa-associated lymphoid tissue (MALT)

Unencapsulated lymphatic tissue of the digestive, respiratory, urinary, and reproductive tracts

Nodules

Tonsils and appendix are composed of lymphatic _____

Peyer's patches

Aggregates of lymphatic nodules found in ileum

Lymphatic organs

Consist of encapsulated lymphatic tissue

Lymph nodes, thymus, and spleen

Major locations of lymph nodes

Cervical region, axillary region, supratrochlear region, inguinal region, pelvic cavity, abdominal cavity, thoracic cavity

2 primary functions of lymph nodes

Filter potentially harmful particles from the lymph

Immune surveillance: Monitor body fluids via macrophages and lymphocytes

Lymphocyte production

Along with the red bone marrow, the lymph nodes are centers for _____

Lymphocytes

Attack various pathogens in lymph nodes

Macrophages

Engulf and digest foreign substances, damaged cells, debris

Lymphedema

Fluid accumulation in a local area that results from disruption of the flow of lymph

Often results when lymph nodes are surgically removed due to presence of cancer

Commonly occurs in cases of breast cancer, when cancer has spread to the axillary lymph nodes

_____ from breast cancer is found in the arm on the side of the body from which the lymph nodes have been removed

Lymphedema treatment

Regular exercise, wearing a compression sleeve on the affected arm, raising the arm above the level of the heart, and using a compression pump to help drain the excess fluid

Lymph nodes

Location: In groups or chains along the paths of larger lymphatic vessels

Function: Filter foreign particles and debris from lymph; house lymphocytes that destroy foreign particles in lymph; house macrophages that engulf and destroy foreign particles and cellular debris carried in lymph

Thymus

Location: In the mediastinum posterior to the upper portion of the body of the sternum

Function: Houses lymphocytes; differentiates thymocytes into T lymphocytes

Spleen

Location: In the upper left portion of the abdominal cavity, inferior to the diaphragm and posterior and lateral to the stomach

Function: Houses macrophages that remove foreign particles, damaged red blood cells, and cellular debris from the blood; contains lymphocytes; blood reservoir

Pathogens

Lymphatic system defends body against infection by _____

Disease-causing agents

Bacteria, viruses, protozoa, and spores of organisms like fungi (which may be single-celled or multi-celled)

Viruses

Have a simpler structure than living cells

Consist of a nucleic acid (DNA or RNA) and a protein coat

Examples: Herpes (DNA) and SARS-CoV-2 (RNA, causes COVID-19)

Use host cells to produce their own proteins and reproduce

Bacteria

Single, simple cells

Cause many common infections, such as those of Staphylococcus and Streptococcus

Immunity

Ability of body to prevent pathogen entry or destroy any pathogens that enter the body

Immune mechanisms

Innate (nonspecific) defenses and adaptive (specific) defenses

Innate (nonspecific) defenses

General defenses

Protect against many types of pathogens

Adaptive (specific) defenses

More specific and precise, targeting specific antigens

Carried out by lymphocytes that recognize certain foreign molecules

Species resistance

Innate defense

Certain species are resistant to diseases that affect other species

Certain species lack receptors, temperature, or chemical environment for a particular pathogen

Mechanical barriers

Innate defense

Skin and mucous membranes form mechanical barriers

Prevent entrance of pathogens

First; second

Mechanical barriers considered the _____ line of defense (all other nonspecific defenses are part of the _____ line of defense)

Examples of mechanical barriers

As epidermis sloughs off, removes superficial bacteria

Ciliated epithelium in respiratory tract traps and sweeps away pathogens

Tears, saliva, and urine wash away microorganisms

Inflammation

1. Blood vessels dilate. Capillary permeability increases and fluid leaks into tissue spaces→tissues become red, swollen, warm, and painful

2. White blood cells invade the region→pus may form as white blood cells, bacterial cells, and cellular debris accumulate

3. Tissue fluids containing clotting factors seep into the area→a clot containing threads of fibrin may form

4. Fibroblasts arrive→a connective tissue sac may form around the injured tissues

5. Phagocytes are active→bacteria, dead cells, and other debris are removed

6. Cells divide→newly formed cells replace injured ones

Enzymes

_____ in body fluids provide a chemical barrier to pathogens

Interferons

Block viral replication, act against growth of tumors, stimulate phagocytosis

Defensins

Peptides produced by neutrophils and other granulocytes; they cripple microbes by making openings in cell membranes or walls

Collectins

Proteins that protect against many bacteria, yeast, and some viruses

Complement system

Group of inactive proteins in plasma and other body fluids that becomes activated by binding to surface of foreign cells; once activated→cascade of reactions that stimulates inflammation, attracts phagocytes, enhances phagocytosis, and causes cell lysis

Natural killer cells

A small population of lymphocytes

Very different from B-cells and T-cells that provide adaptive defenses

Defend against viruses and cancer cells by secreting cytolytic substances called perforins

Enhance inflammation

Perforins

Substance that lyses cell membrane for natural killer cells

Phagocytosis

Removes foreign particles from the lymph

Phagocytes

_____ in the blood vessels and the tissues of the spleen, liver, or bone marrow remove particles from blood

Neutrophils and monocytes

Most active phagocytic cells are _____ and _____

Chemotaxis

Chemicals from damaged tissue attract these phagocytic cells to the injury; this is called _____

Macrophages.

Monocytes that leave the blood become _____, which can be free or fixed in tissues

Mononuclear phagocytic system

Consists of monocytes and macrophages of the body

Raises thermoregulatory set point

Fever begins when a viral or bacterial infection stimulates lymphocytes to proliferate, producing cells that secrete a substance called interleukin-1 (IL-1), which _____

Endogenous pyrogen

IL-1 is also called _____ (fire maker from within)

Elevated body temperature

Indirectly inhibits microbial growth; causes liver and spleen to take up iron, making it unavailable for bacteria and fungi to use in their normal metabolism

Increases phagocytic activity