Download F. Q. How do we control and coordinate our body functions?

Topic: Third Line of Defense
Biology Buzz
I. BLOOD… a fluid tissue that serves three
important functions:
1. Responsible for transport of materials
throughout the body.
“Materials” include enzymes, lipids,
hormones, CO2, O2, urea, nutrients such as simple
sugars and amino acids.
2. Regulates pH, body temperature,
and water content of cells.
3. Protects against disease causing
microorganisms known as pathogens.
Blood is made up of four components:
a) Plasma- liquid part of blood mostly made up of
water with dissolved materials.
b) Red Blood Cells (RBC’s)Carries O2 and CO2 to and away from cells of the
body.
Contains hemoglobin (a protein on the surface of
RBC’s)
c) PlateletsResponsible for clotting blood.
d) White Blood Cells (WBC)- Leukocytes
 Protects body against infection.
 Made in bone marrow and lymph nodes.
 Carried in blood but can also move out of
blood vessels to tissues of body.
There are two main types of WBC’s:
1. Phagocytic WBC
Fight microorganisms
by phagocytosis
(to engulf)
2. Lymphocytes (B and T
cells)
Produces antibodies
that recognize foreign
substances (B cells)
Kill foreign/infected
cells directly (T cells)
Third Line of Defense- Activation of the
Immune System (Immune Response)
 Lymphocytes (WBCs) recognize, attack,
and then destroy pathogens.
This is done in two ways:
1. B cells produce antibodies which
recognize specific antigens to inactivate
them (Antibody/antigen relationship is
very specific.
2. T cells known as cytolytic T cells
physically bind with a pathogen and
destroy the pathogen or infected cell.
Antigen vs. Antibody
 ANTIGEN- proteins found on the surface of pathogens
that cause an immune response
activation of B and T cells (WBCs)
 ANTIBODY- a Y shaped protein made by B cells and
helps to destroy pathogens in a couple of ways:
1. Marks pathogens for identification.
2. Binds to antigens and covers surface of
pathogen to inactivate it.
*An antibody recognizes a specific antigen!
Now answer Questions 2 and 3!