Pet First Aid Instructor Level 3 (VTQ) - Online Blended Part 1

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Circulatory system

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The Circulatory System: Blood, Heart, and Blood Vessels

1. Blood Composition

Blood Components: Blood is composed of cells suspended in plasma, consisting of four components: red blood cells, white blood cells, platelets, and plasma.

Red Blood Cells: Approximately 242 to 270 million per drop, containing hemoglobin to carry oxygen.

White Blood Cells: Fewer in number, transparent, part of the immune system to fight infections.

Platelets: Cell fragments that assist in preventing blood loss and promote clotting.

Plasma: Straw-colored liquid, 91.5% water, 8.5% solutes (proteins, electrolytes, nutrients, gases, hormones, enzymes, vitamins, and waste products).

2. The Heart

Function: A muscular pump that circulates oxygen and nutrients throughout the body.

Structure: Divided into two halves (left and right), each with two chambers (atrium and ventricle).

Flow of Blood: Atria receive blood from veins, ventricles provide the force to push blood to various destinations.

Valves: Different valves perform specific tasks within the heart.

3. Blood Circulation

Venous Return: Deoxygenated blood returns from the body to the right atrium via the inferior and superior vena cava, then is sent to the lungs via the pulmonary artery.

Oxygenation: Blood in the lungs absorbs oxygen and becomes bright red, entering the left atrium via the pulmonary vein.

Systemic Circulation: Left ventricle ejects oxygenated blood into the systemic circulation via the aorta.

Direction of Blood Flow: Arteries carry blood away from the heart, while veins carry blood to the heart.

4. Cardiac Function

Pacemaker: The Sinoatrial node in the right atrium initiates cardiac muscle contraction.

Stimulation: The autonomic nervous system stimulates the myocardium to contract.

5. Blood Vessels

Vasoconstriction & Vasodilation: Blood vessels can narrow (vasoconstrict) or widen (vasodilate) due to smooth muscle in their walls.

Regulation: This ability directs blood flow to different tissues based on oxygen and nutrient requirements.

Blood Pressure: Blood vessel regulation also plays a role in blood pressure control.

Considerations: Eating close to exercise or during shock can impact blood flow distribution.