14-2 blood and blood vessels
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14-2 Blood and Blood Vessels
BLOOD VESSELS
Blood circulates through the body through a series of vessels
1. Arteries: blood vessels that carry blood away from the heart
Except for the pulmonary arteries, all arteries carry oxygenated blood
With each contraction the heart forcefully ejects blood into arteries
The artery’s wall expands and then returns to its original size
Blood passes from the arteries into a network of smaller arteries called arterioles
2. Capillaries
blood vessels in which gases, nutrients, hormones and other molecules are transferred from the blood to the body’s cells
No cell in your body is more than a few cell diameters away from a capillary
Capillary walls are only one cell thick—gas and nutrient molecules easily pass through their thin walls
**INTERESTING FACT: If all the capillaries of your body were laid end to end, they would extend all the way across the US!!!!
3. Veins
blood vessels that return the blood to the heart
The walls of veins consists of a much thinner layer of smooth muscle than the walls of the arteries
They are farther away from the heart pump so therefore are exposed to less pressure
The flow of blood in veins is helps by contractions of skeletal muscles
when muscles contract they squeeze against veins and help force blood toward the heart
B) BLOOD PRESSURE
Blood moves through our system because it is under pressure
This pressure is caused by the contraction of the heart and by muscles that surround blood vessels
Blood pressure: a measure of force that blood exerts against the walls of a blood vessel
Blood pressure is always highest in the two main arteries that leave the heart
Both high and low blood pressure can cause problems to our health
High blood pressure is very common in Americans—hypertension
Blood pressure is measured with two numbers
1—systolic: the pressure of the blood when the heart contracts
2—diastolic: the pressure of the blood when the heart relaxes
blood pressure is given as the systolic number over the diastolic number
C) BLOOD
“River of Life”blood: type of connective tissue containing
various substances and cells
Blood serves many functions:
collects oxygen from the lungscollects nutrients from the digestive tractcollects waste products from tissueshelps to regulate body temperaturehelps fight infectionshelps repair damaged blood vessels
Blood is made up of various components:
1. Blood Plasma Accounts for 60% of
the blood Liquid portion of the
blood—90% water and 10% solutes
The other solutes include nutrients, gases, enzymes, hormones and waste products
2. Red Blood Cells
Cells that carry oxygen
Each mL of blood contains 5 million RBCs
RBCs have a biconcave shape—this means that they are narrower in the center than along the edges
Also known as ERYTHROCYTES
Carry hemoglobin—iron-containing protein that enables RBCs to carry oxygen—it also gives RBCs their color
Since mature RBCs carry so much hemoglobin, they do not have nuclei or organelles
3) White Blood Cells
“army” of the body Also known as
LEUKOCYTES The main function of
the WBCs is to protect the body against invasion by foreign cells or substances
Outnumbered by RBCs almost 500 to 1
larger than RBCs—do contain nuclei—almost colorless
there are different types of WBCs with different functions
4) Platelets
Platelets are not cells—they are tiny fragments of cells
Play an important role in blood clotting—they clump together and form a plug at the site of the wound
D) BLOOD TYPES
Blood type is determined by the type of antigen present on the surface of RBCs
Antigen: a protein or carbohydrate that acts as a signal which cause antibodies to be made
If a person has A antigens—they are type A
if a person has B antigens—they are type B
if a person has both antigens—they are AB
if a person has neither A nor B—they are type O
Type AB is known as the universal receiver—they can receive any type of blood
Type O is known as the universal Donor, meaning they can donate blood to anyone
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