1. They Lymphatic System & Body Defenses
Human Anatomy & Physiology
Unit 6

2. Lymphatic Vessels
The function of lymphatic vessels is to pick up the excess tissue fluid (called lymph = clear water) and return it to the blood stream
These vessels form a one-way system and only flow towards the heart
Lymph capillaries spider web through the body tissues to collected leaked fluid

3. Lymphatic Vessels
Like veins, lymphatic vessels have valves to prevent the fluid from flowing backwards
While, blood stays relatively free of bacteria, viruses and cancer – they can easily enter the lymphatic vessels
This creates a problem because bacteria, viruses and cancer can then easily travel to other parts of the body
To solve this lymph nodes are throughout the body to “examine” and cleanse (if needed) by the immune system

4. Lymph Nodes They work along with the immune system to protect the body
As the lymph is transported to the heart it makes several stops through lymph nodes to be “checked” before it reaches the heart
A collection of lymphocytes are located in lymph nodes to respond if a foreign substance is detected
This is why most of us will get swollen glands during an active infection

5. Lymph Nodes
Most lymph nodes are kidney shaped and less than one inch long
There are two regions of lymph nodes in the body the right lymphatic duct and the thoracic duct
The neck and head drain into the right duct and the rest of the body goes through the thoracic duct (within these regions are thousands of lymph nodes)

6. Other Lymphoid Organs
Spleen – helps to filter the blood and destroy worn- out red blood cells to they can be reabsorbed by the liver
The thymus gland – functions at peak performance during youth; produces thymosin a hormone to create certain lymphocytes to heighten their protective roles
Tonsils – their job is to trap foreign pathogens before they enter the body

7. Body Defenses
Every second of everyday hostile bacteria, viruses and fungi are trying to invade our system
There are two approaches to body defenses: nonspecific and specific defense system

8. Nonspecific Defense System
This system responds immediately to ALL foreign substances
First line of defense is the skin, mucous membranes and secretions of the skin
The second line is phagocytic cells, antimicrobial proteins and an inflammatory response

9. Nonspecific Body Defenses
Examples of Surface Membrane Barriers:
Skin is a physical barrier
Mucous membranes line all body cavities to act as a physical barrier
Vaginal secretions of adult females are very acidic
The stomach produces HCl to kill pathogens
Saliva can kill some pathogens
Tiny hairs in the nasal cavity trap inhaled

10. Nonspecific Body Defenses
Examples of Cells and Chemical Defenses:
A fever will help increase the rate at which defense cells work
Phagocytes will engulf a foreign particle
Natural killer cells will target any foreign particle and attack the cell's membrane (the cell will then shortly disintegrate)
Inflammatory response will trigger redness, heat, swelling and pain
The redness and heat is caused by the increase of blood to the site, the swelling and pain is caused by the body’s attempt to prevent movement and promote healing

11. Specific Defense System
This is commonly called the immune system
The most important immune cells are they lymphocytes and macrophages
A proper working immune system will protect the body from bacteria, viruses, transplanted organ or blood and even our own cells that have turned against us

12. Specific Body Defenses
The two main types of immune cells are B- cells and t-cells
Within the B-cell family and T-cell family there are several types and each have their own job
Memory B-cells
Memory T-cells
Helper T-cells
Plasma cells
Suppressor T-cell

13. Specific Body Defenses
Active immunity can occur two ways naturally or artificially through immunizations
The immune system has the ability to “remember” some diseases
Passive immunity occurs when the protection is “borrowed”
For example, a mother to fetus or through breast milk (the immune system does not “remember” using passive immunity)

14. Disorders of Immunity Allergies
The body fights off a perceived threat that would otherwise be harmless (basically, the immune system overreacts)
Allergies are rarely fatal; however, when the reaction enters the blood stream it circulates rapidly through the body
This is call anaphylactic shock and can be fatal

15. Disorders of Immunity Immunodeficiency (both congenital and acquired)
Basically, there is little to no immune response
Severe combined immunodeficiency disease (SCID) – congenital
Acquired immune deficiency syndrome (AIDS)

16. Disorders of Immunity Autoimmune Diseases Multiple sclerosis (MS)
Myasthenia gravis
Graves’ disease
Type 1 diabetes mellitus
Systemic lupus erythematosus (commonly called lupus)
Rheumatoid arthritis