IB Biology SL - Topic 6: The Blood System

Plasma

Liquid component of the blood; dissolves or carries all other components of blood, nutrients, wastes, etc

Erythrocytes

Red blood cells; transport oxygen in hemoglobin molecules

Leucocytes

White blood cells; phagocytes and lymphocytes

Phagocytes

Eat up pathogens and dead cells

Lymphocytes

B-cells and T-cells for the immune response

Platelets

Allows for the clotting of blood following damage to cells or erythrocytes

Arteries

Carry high pressure blood to the heart and to tissues that need it

Lumen

The cavity through which blood flows through veins, arteries, and capillaries

Tunica Externa

The outermost layer of arteries; the external elastic membrane allows for its elasticity

Tunica Media

Middle layer of artery walls which contain smooth muscle to contract and relax the artery

Tunica Intima

Innermost layer of arteries containing the endothelium and internal elastic membrane which allows for elasticity

Endothelium

Inner cellular lining of the blood vessels and lymphatic system which allows for contact with surrounding cells

Veins

Carry low pressure blood back to the heart using valves to ensure blood flows in the correct direction

Valves

Flaps of tissue in blood vessels which prevent the backflow of blood due to gravity

Capillaries

The smallest blood vessels which allow for gas and substance exchange from the blood

Basement Membrane

Membrane of capillaries which is permeable to many substances, allowing for easy and short diffusion

Vena Cava

Vein through which oxygen-poor blood flows to the heart

Right Atrium

Cavity through which oxygen-poor from the body arrives into the heart

Tricuspid Valve

Valve separating the right atrium and ventricle

Right Ventricle

Cavity through which oxygen-poor blood arrives from the right atrium and is sent to the pulmonary artery

Pulmonary Valve

Valve separating the right ventricle from the pulmonary artery

Pulmonary Artery

Artery through which oxygen-poor blood flows to the lungs

Pulmonary Veins

Veins from which oxygen-rich blood from the lungs flow to the heart

Left Atrium

Cavity through which oxygen-rich blood from the lungs arrives into the heart

Bicuspid Valve

Valve separating the left atrium and ventricle

Left Ventricle

Cavity through which oxygen-rich blood arrives from the left atrium and is sent to the aorta

Aortic Valve

Valve separating the left ventricle from the aorta

Aorta

Artery through which oxygen-rich blood flows to the body

Deoxygenated Blood

Blood which is low in oxygen and high in carbon dioxide; arrives at the right side of the heart

Oxygenated Blood

Blood which is high in oxygen and low in carbon dioxide; arrives at the left side of the heart

William Harvey

English physician who completely described the process of systemic circulation via a series of experiments:
1. Fish heart --> if the entrance to the atrium was tied, the heart would be emptied of blood
2. Snake heart --> if the vein is seized, the heart muscle becomes pale and it soon cannot function due to being distended
3. Dog heart --> if the aorta is tied at the base, arteries empty but veins are distended

Diastole

Arrival of blood to the heart; atria and ventricles relax, blood flows into the heart from veins, AV valves open, and SL valves close

Atrial Systole

Atria contract and ventricles relax, blood is pushed into the ventricles, AV valves open, and SL valves remain closed

Ventricular Systole

Atria are relaxed and ventricles contract, blood is pushed into the arteries, AV valves close, and SL valves open

AV Valves

Bicuspid and tricuspid valves

SL Valves

Pulmonary and aortic valves

Coronary Heart Disease

Disease which leads to heart failure due to plaque build-up; can be caused by a genetic predisposition, older age, smoking, a bad diet, a lack of exercise, obesity, stress, and is more common in males

Myogenic Muscle Contraction

The involuntary contraction of cardiac muscle which causes the heart to beat

Myocyte

Cardiac muscle cell which is the origin of contraction

Sinoatrial Node

Pacemaker; controls heart rate by sending a wave of excitation, causing the atria to contract

Atrioventricular Node

Receives the wave of excitation from the sinoatrial node and causes the ventricles to contract

Nerve Signaling

Allows the brain to alter heart rate based on the medulla oblongata

Medulla Oblongata

Region in the brain stem which detects rising CO2 blood levels

Sympathetic Nerve

Releases noradrenaline to increase the heart rate

Parasympathetic Nerve

Releases acetylcholine to decrease the heart rate

Hormone Signaling

Method by which the heart rate is modified based on hormones

Adrenaline

Hormone released in the 'fight or flight' response; increases the heart rate by activating the same chemical pathways as noradrenaline