Biology: Circulatory System

Open Circulatory System

Simple organisms (such as insects) rely on diffusion to exchange oxygen. Animal movements help pump 'blood'.

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Diffusion is the absorption of oxygen through the skin, and the skin must be constantly moist.

Closed Circulatory System

Closed circulatory systems have blood stored in blood vessels. Large vessels branch to smaller ones, bringing blood to specific tisses (eg. arteries and arterioles, veins and venules).

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Mammals have a closed circulatory system due to their larger size and complexity.

Blood Components

* Plasma
* Platelets
* Red blood cells
* White blood cells

Red Blood Cell (Erythrocytes)

* A bioconcave disc which is round and flat
* There is no nucleus despite it being a cell
* It contains hemogoblin protein (protein that makes blood red)
* It is made in the bone marrow and destroyed in the spleen

White Blood Cell (Leukocytes)

* "Eats" + digests micro-organisms by changing shape
* The main divisions/types of white blood cellls are macrophages and lymphocytes

Macrophages

Breaks micro-organisms apart (digests)

Lymphocytes

Produces antibodies for immune responses

Platelets

They are bits of cells broken off larger cells. Fibrinogen fibers form a net to trap blood cells, which forms blood clots. Their primary function is to prevent and stop bleeding.

Plasma

The fluid portion of blood. It contains food nutrients, waste, hormones, vitamins, minerals, and antibodies.

Arteries

They carry blood AWAY from the heart. They have thick muscle for elastic fibers to allow stretch under pressure. They branch off into arterioles.

Arterioles

They branched from arteries to bring blood to specific tissues. They contain smooth muscle that can contract and relax.

Veins

They carry blood BACK to the heart. They are thinner-walled compared to arteries and branch off into venules. Veins contain one way valves.

Valves

Present in veins to prevent blood from flowing backwards. It is comprised of two flaps.

Capillaries

Exchanges material with cells and blood. They connect arterioles and venules. The wall of a capillary is only one cell thick.

Coronary Circulation

Oxygenated blood is pumped into the heart.

Pulmonary Circulation

Deoxygenated blood is pumped to the lungs. Oxygenated blood is carried back to the heart.

Systemic Circulation

Oxygenated blood is carried to body tissues. Deoxygenated blood is carried back to the heart.

Double Circulatory System

The right side of the heart's system deals with deoxygenated blood.

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The left side of the system deals with oxygenated blood.

Myocardium

The heart muscle

Endocardium

The inner lining of the myocardium (inner surface)

Epicardium

The outer surface of myocardium

Atria

The top 2 chambers of the heart (atrium singular), which are thin-walled.

Ventricles

The bottom 2 chambers of the heart, which are thick-walled. The left is the largest chamber of the four.

Atrioventricular Valves

* Between the ATRIA and VENTRICULARS
* Opens when the ATRIA contract
* Allows the ventricles to fill up
* Once ventricles are filled, these valves close to prevent flow of blood back into ATRIA

Semilunar Valves

* Between ARTERIES and VENTRICLES
* Opens when VENTRICLES contract
* Right ventricle sends blood to pulmonary artery
* Left ventricle sends blood to aorta
* Closes to prevent flood flow back into VENTRICLES

How does the heart work: Step 1

The heart begins when the heart muscles relax and blood flows into the atria.

How does the heart work: Step 2

The atria contract and the valves open to allow blood into the ventricles.

How does the heart work: Step 3

The valves close to stop blood flowing backwards into the atria. The ventricles contract, forcing the blood to leave the heart. At the same time, the atria are relaxing and once again filling with blood.

P Wave

Activation of the atria

QRS Complex

Activation of ventricles

T wave

Recovery wave

SA Node

Sinoatrial node; the pacemaker of the heart. Beats are regulated at around 72 BPM.

Diastole

Relaxation (dilation) of the heart, when the ventricles of the heart fill with blood (entering through tricuspid and mitral valves).

Systole

Contraction of the heart, during which blood is pushed out of the ventricles (leaving through pulmonary and aortic valve).

Systolic Pressure

When ventricles contract

Diastolic Pressure

When ventricles relax

Medulla Oblongata

Regulates blood pressure by sending signals to receptors in body

Vasoconstriction

Reduction in the diameter of the blood vessel + decreases blood flow (less oxygen).

Vasodilation

Increase in diameter of the blood vessel + increases blood flow (more oxygen).