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