Cardiovascular System

Components- blood, heart, blood vessels

1st system to become fully operational (heart beats at the end of the 3rd week of development)

Functions of Blood

Transportation of dissolved gases, nutrients, and hormones

Regulation of pH and ion composition of interstitial fluids

Restriction of fluid losses at injury sites (blood clots)

Defense against toxins and pathogens Stabilization of body temperature

Composition of Blood

Fluid connective tissue with a matrix called plasma

Formed elements- RBC transport oxygen, WBC defend body, platelets help clot the blood

Blood Facts

Blood Temperature is 38 C Blood is 5 times as viscous as water pH is slightly alkaline averaging 7.4 Body contains between 4-6 liters of

blood

Plasma

Composed of 92% water 7% plasma proteins 1% other solutes

Plasma Proteins

Albumins- most common, maintain osmotic pressure, transport fatty acids, steroid hormones, and cholesterol

Globulins- antibodies Fibrinogens- blood clotting Peptide hormones- insulin, thyroid

stimulating hormones, etc.

Formed Elements Red Blood Cells (RBC)- make-up 99% of formed

elements Hemoglobin- red pigment that binds to oxygen One drop contains 260 million RBCs, account

for 1/3 of all cells of the body Each RBC can carry more than a billion

molecules of oxygen No nuclei, mitochondria, or ribosomes Don’t divide or make proteins, life span about

120 days

RBC continued Cells of the liver, spleen, and bone marrow

monitor blood for damaged cells RBC’s are formed in the red bone marrow Biconcave shape

Provides larger SA to volume ratio, allows oxygen to be absorbed and released quicker

Allow RBC to stack on top of each other, this makes it easier to flow through narrow areas

Allows bending and flexing through very small capillaries

Blood Types Blood types are determined by the type of

antigen present on RBCs Antigens are proteins on the surface of the cell

that mark the cell as being “self” The main surface antigens of RBCs are A, B,

and Rh A person can have A, B, AB, or neither A or B and

be type O. In addition you either have a Rh (+), or not (-)

Blood type cont. Your body will produce antibodies (called

agglutinins) to combat antigens not found on your own cells. When these agglutinins attack foreign RBC they bind to them and clump in a process called agglutination

People w/out the Rh antigen (Rh-) don’t necessarily carry an antibody against Rh. This antibody is produced when a person is exposed to Rh.

White Blood Cells “leukocytes”

Have nuclei and other organelles, but lack hemoglobin

Defend body against invasion by pathogens

Circulate for only a short portion of their lifespan

Function of WBC

Neutrophils- difficult to stain, digest bacteria that have been marked by antibodies and then join w/ lysosomes that break down pathogens

Short life span- 10 hours in blood, or only 30 minutes when attacking bacteria

Eosinophils and Basophils

Stain darkly, attach object with antibodies, use endocytosis, defend against large multicellular parasites

Basophils- Stain darkly, rare 1%, release histamine, which dilates blood vessels and heparin, which prevents blood clotting

Monocytes

Circulate in the blood for only 24 hours, then enter tissues and become macrophages, which engulf debris, and microorganisms in cells

Lymphocytes

20-30% of WBCs, T cells- cell mediated immunity B cells- make antibodies to attack

foreign material in the blood NK cells- natural killer cells, immune

surveillance, important in preventing cancer

Hemostasis- cessation of bleeding Prevents loss of blood when there is

damage to vessel walls at the same time providing a framework for tissue repair

3 Phases Vascular Platelet Coagulation

Vascular Phase

As soon as there is a cut in the wall of a blood vessel, smooth muscle fibers in the wall contract, lasts for 30 minutes Decreases diameter of blood vessel,

restricting blood flow Stimulates release of chemical factors

that accelerate division of new cells to help in repair

Platelet Phase

Platelets in the blood stick to the walls of the vessel surrounding cut as well as collagen fibers exposed to the cut, 15 seconds after injury

Platelet plug Platelets release compounds that stimulate

contraction of smooth muscle and more platelets to stick to plug, positive feedback

Coagulation Phase 30 seconds after injury Complex sequence of steps, fibinogens that

circulate in blood are changed into fibrin which is an insoluble fiber

Fibrin forms over platelet plug Clotting requires Ca2+ and 11 different proteins

(clotting factors) Some of these clotting factors create a positive

feedback loop to increase rate of coagulation