IB Bio Topic 6.2 - The Blood System

Arteries

a type of blood vessel known for conveying blood at high pressures from the ventricles to the tissues of the body

Aorta

the main, largest artery of the heart, which connects it to the rest of the body

Systolic Pressure

refers to the part of the heartbeat when muscles are contracting

Diastolic Pressure

refers to the part of the heartbeat when muscles are relaxing

Arterial Walls (Walls of Arteries)

contain elastic fibers that stretch with heartbeats and recoil when the muscles relax, propelling blood forward. Also have muscular walls to help maintain blood pressure between pump cycles.

Tunica Intima

the innermost layer of the arterial wall; it is in direct contact with the blood in the lumen. The inner part that faces the lumen is lined with endothelium, which forms a smooth, friction-reducing lining

Tunica Media

the middle coat of the arterial wall. It is mainly made of smooth (involuntary) muscle cells and elastic fibers arranged in spiral layers. It is the thickest of the three layers

Tunica Adventitia

the outermost coat of the arterial wall. It is a tough layer of loosely woven collagen fibers that protect the blood vessel and anchor it to nearby structures

Vasoconstriction

the constriction of circular muscles surrounding arteries due to the constriction of the heart causing arteries to experience high pressure

Vasodilation

the relaxation of circular muscles surrounding arteries due to the relaxation of the heart causing arteries to experience low pressure

Arterioles

smaller arteries in the body that branch off to supply blood to organs, limbs, etc.

Heart Rate (Pulse)

The number of times the heart beats per minute

Stroke Volume

the volume of blood pumped out of the left ventricle of the heart during each contraction/heartbeat

Cardiac Output

the volume of blood pumped through the circulatory system in a minute

Atria

the upper tissues of the heart

Ventricles

the lower tissues of the heart

Veins

blood vessels that transport blood from the tissues of the body back to the heart (specifically the atria) at a low pressure

Plasma

the liquid portion of blood. It carries dissolved substances like CO2, hormones, vitamins, minerals, glucose, and proteins

Capillaries

very small blood vessels formed from the successive division of arterioles. They are only one cell thick and lack any other wall structure

Venules

small blood vessels that form veins when many of them fuse together

Tissue Fluid (Interstitial Fluid)

the liquid part of the blood that passes through capillary walls to bathe tissue cells

Double Circulatory System

refers to the fact that blood enters the heart twice before it is distributed to the tissues

Vena Cava

a large vein that carries blood back to the heart. There is a superior and inferior version of it.

Atrioventricular Valves

open and close to control the flow of blood from the atria to the ventricles on either side of the heart

Septum

the space separating the two sides of the heart

Pulmonary Artery

A type of artery that carries deoxygenated blood from the heart to the lungs

Pulmonary Vein

A type of vein that carries oxygenated blood from the lungs back to the heart

Sinoatrial Node (SA Node)

a group of specialized muscle cells in the wall of the right atrium of the heart. It is known as the “pacemaker” because it initiates heartbeats and sets the heart rate.

Cardiac Cycle

the complete sequence of events in the heart from the start of one beat to the beginning of the next.

Bundle of His

The signal emitted by the SA Node arrives here from the AV node. It is located in the interventricular septum.

Purkinje Fibers

The signal emitted by the SA Node passes through here to reach the ventricles.

Isovolumetric

refers to when a ventricle contracts or relaxes with no corresponding volume change. This occurs because valves are still closed

Cardiac Accelerator Nerve

a nerve located in the medulla oblongata of the brain (in a part of it called the cardiovascular center). It simulates the heart to beat faster

Vagus Nerve

another nerve located in the medulla oblongata. It stimulates the heart to beat slower

Cardiovascular Center

the part of the brain that monitors blood pressure, pH, and CO₂ concentrations to determine whether impulses to the heart should be propagated via the cardiac accelerator nerve or the vagus nerve

Epinephrine (Adrenaline)

the “fight or flight” hormone that is located in the medulla of the adrenal glands. It increases the heart rate by stimulating the SA node to initiate signals at a faster rate, as well as increasing the speed of the signals emitted by the SA and AV nodes

Atheromas

fatty deposits caused by high blood concentrations of low density lipoprotein (LDL) in the arterial walls next to endothelial cells

Thrombosis

the forming of a clot in a blood vessel that can block it entirely. These fatty deposits start as ruptures in the arterial walls, and can end up blocking the artery entirely

Coronary Artery

an artery that supplies the heart with oxygen and nutrients

Angina

medical term for the chest pain caused by the restricted flow of blood in a coronary artery (due to deprived oxygen and nutrients)