The Cardiovascular System Advanced Biology Chapter 46 WAGGY

Chapter Objectives Describe the structure & function of the heart Trace the flow of blood through the heart & the body Distinguish between veins, arteries & capillaries

The Cardiovascular system The blood, heart & blood vessels make up the cardiovascular system Along with the lymphatic system, nutrients, hormones & gases are delivered to each cell & wastes are removed the Cardiovascular & lymphatic system together help to control body temperature

The Cardiovascular System The central organ of the cardiovascular system is the heart The heart beats more than 2.5 billion times in an average life span The heart is slightly larger than a fist & is located between the lungs, behind the sternum in the thoracic cavity

The Heart The heart is surrounded by a tough membrane called the pericardium which secretes a fluid that reduces friction as the heart beats The outside of the heart is covered with numerous cardiac arteries & veins that nourish the heart muscle A septum (wall) vertically separates the heart into two sides The right side pumps blood to the lungs The left side pumps blood to the rest of the body

The Heart… Each side is divided into two portions The upper portions are called atria (atrium) The lower portions are ventricles Each portion of the heart is separated by valves

The Heart… Valves are flaps of tissue that open in only ONE direction The atrioventricular valves (AV valve) allow blood to flow from the atria to the ventricles The right AV valve is the tricuspid valve & the left valve is the bicuspid valve

The Heart… The semilunar valves (SL valves) are between the ventricles & the blood vessels connected to the heart The SL valve on the right side is called the pulmonary valve & the one on the left is called the aortic valve

The Heart: blood flow Blood returning to the heart from the body contains a high concentration of CO2 & travels through the inferior vena cava This O2 poor blood enters the right atrium The right atrium contracts sending the blood through the tricuspid valve & into the right ventricle

The Heart: blood flow The right ventricle contracts & the blood is pushed through the pulmonary valve into the pulmonary artery The pulmonary artery leads to the lungs where gas exchange occurs & now the blood is O2 rich O2 rich blood returns to the heart through the pulmonary veins

The Heart: blood flow The oxygenated blood enters the left atrium & is then pushed through the bicuspid valve into the left ventricle The left ventricle contracts sending the blood through the aortic valve into the aortic artery (aorta) The left ventricle has the thickest muscle wall because it is responsible for pumping blood to the entire body

Misconception Alert! Often oxygenated blood is color coded bright red in textbooks & deoxygenated blood is color coded blue In real life, oxygenated blood is bright red, but deoxygenated blood is dark red in color The deoxygenated blood appears blue when we look at our veins - but it really is not!

The Heart: electrical control Cardiac muscles are specialized muscle tissue When it contracts, it does so in waves The heart also coordinates all of its contractions into a steady rhythm of both atria contracting & then both ventricles contracting

The Heart: electrical control The contractions begin at specific places in the heart The sinoatrial node (SA node) is a group of specialized cardiac muscle cells in the right atrium The SA node generates an electrical pulse that moves outward throughout the rest of the atrial cells

The Heart: electrical control When the electrical pulse reaches the atrioventricular node (AV node) located between the atria & ventricles, the pulse is relayed to the ventricular cells causing them to contract The ventricular contraction is a fraction of a second after the atrial contraction

The Heart: electrical control A heartbeat has two phases: 1. Systole: occurs when the ventricles contract closing the AV valves & opening the SL valves (lub) 2. Diastole: occurs when the ventricles relax closing the SL valves & opening the AV valves (dub)

The Heart: electrical control This creates the characteristic ‘lub-dub’ sound of a human heartbeat If one of the valves does not close completely, then some blood is allowed to move backwards in the heart - this is called a murmur

Blood Vessels A persons pulse is a series of pressure waves within an artery caused by the contraction of the left ventricle When the blood surges through the arteries, the elastic walls of the vessels expand and stretch The average pulse rate is 70-90 beats per minute (bpm)

The Arteries The large muscular vessels that carry blood away from the heart are called arteries The walls of the arteries have three layers: 1. A smooth endothelial layer 2. A middle layer of smooth muscle 3. Outer layer of connective tissue for strength

The Arteries As the arteries move away from the heart, they split into smaller & smaller vessels First arteries become arterioles, then capillaries A capillary is so tiny that blood cells must move through it in single file!

The Veins After gas exchange occurs between the cells & the capillaries it is time to begin the journey back to the heart The capillaries, now carrying O2 poor blood turn into veinules Several veinules will merge to become larger veins Veins continue to merge to form the very large vein, the Vena Cava

The Veins Veins & the Vena Cava have small valves inside to prevent the blood from moving backwards The blood pressure from the left ventricle is much lower in the veins & so valves are needed to ensure that the blood makes it all the way back to the heart

THE END!!