Blood Vessels and Our Pulse
Blood Vessels in Your Body All the blood vessels in your body joined together in a straight line would reach from St. John s, Newfoundland, to Victoria, British Columbia, and back, twice! End to end, they would span about 19 000 km Our blood vessels are a complex network of tubes that branch and re-branch The largest blood vessel in the body is about 3 cm in diameter The smallest blood vessels are about 5 μm to 10 μm in diameter, just wide enough for blood cells to pass through in single file
What are the 3 major types of blood vessels? Arteries Veins Capillaries
Review: What do arteries do? What do veins do? What do capillaries do? carry blood away from the heart to the rest of the body bring blood from body back to the heart enable exchange of water and chemicals between the blood and the tissues
Arteries A single large artery (aorta) leaves the heart and branches into major arteries that carry blood around the body Smallest branches are arterioles Walls of arteries have three layers of tissue an outer layer of connective tissue a middle layer of smooth muscle a smooth inner single layer of epithelial cells (endothelium) Ventricles of heart contract to pump blood around the body, arteries expand slightly in diameter to accommodate increased pressure of blood within them When the ventricles relax, the walls of the arteries return to their original size, pushing the blood farther into the downstream vessels The outer layer of arteries includes elastin fibres elasticity of the artery walls ensures there is a continuous flow of blood through the blood vessels, even when the heart is relaxed
Coronary Arteries
Veins Venules and veins carry deoxygenated blood containing CO2 and other waste products from the body tissues Middle layer of smooth muscle not as thick as arteries Walls are not as elastic Internal diameter of veins is greater than that of arteries Blood pressure in veins is lower than in arteries How then does blood get back to the heart, especially from the lower parts of the body? Many of the larger veins have valves that ensure the blood flows in only one direction Skeletal muscles also help the circulation of blood Muscles contract squeeze the veins increases the pressure in the veins helps push the blood back toward the heart (in conjunction with valves)
Capillaries Arterioles branch further into smaller blood vessels called capillaries when it reaches the tissues of the body Capillaries form networks of blood vessels that supply oxygen and nutrients to every cell throughout the body tissues Walls are only a single cell layer thick O2/nutrients diffuse from blood into tissue fluid that surrounds the cells CO2/waste materials diffuse into the tissue fluid and then into the capillaries. Small in diameter: blood cells move through them in single file On one side of capillary networks are arteries and arterioles carrying oxygenated blood and nutrients to the tissues. On the other side, capillaries merge into venules and veins. Blood flows slower through the capillary network provides time for the diffusion of substances into and out of the capillaries
When you are feeling for your pulse, are you feeling a vein or artery? (Explain) Think Pair - Share Heart contracts Blood is forced through artery Artery expands Felt as the pulse if the artery is fairly large, close to the skin, and in front of a bone or other firm structure
Major Arteries and Pulse Points Best places to take your pulse: at your wrist inside the elbow at the side of your neck on the top of your foot You can also take your pulse at your groin, on your temple or behind your knees
Mini Investigation: Taking a Pulse Question: What is YOUR heart rate? Purpose: To find your pulse at several different pulse points and determine your heart rate Start here: The most common point is the radial artery in the wrist Steps: Find your pulse at the radial artery (runs along the thumb side of your wrist) Count the number of beats in 15 seconds and multiply by 4 to obtain your heart rate. Record your heart rate. Refer to the figure on the right to try to find your pulse at other accessible locations
Questions: Think Pair - Share Why do you think the radial artery is the most commonly used pulse point? Did you have difficulty finding other pulse points? Why do you think it was more difficult in other locations? When police or medical personnel check for signs of life, they check the carotid pulse. Why do you think they check this pulse rather than the radial pulse?
At the doctor s The apical pulse is the pulse over the top of the heart, as typically heard through a stethoscope with the patient lying on his or her left side The normal apical pulse rate of an adult is 60 to 100 beats Other than doing an electrocardiogram (ECG), taking the apical pulse is the most accurate, noninvasive way of assessing cardiac health. The apical pulse provides information on count, rhythm, strength and quality of the heart.