CIRCULATION SYSTEM

Blood

Composition

Plasma

  • 55%: water (90%), ions, proteins, gases, nutrients, wastes, hormones

  • Functions: transport of nutrients, hormones, and waste.

Cells (45%)

  • RBCs

    • hemoglobin structure

    • transport oxygen and CO2

  • WBCs: immunity

  • Platelets: hemostasis and clot formation

Functions

  • Transportation

  • Regulation: pH, temperature, adn fluid balance

  • Protection: clotting and immune defense

Blood Circulation pathways

  • Systemic circulation: oxygenated blood from the heart to tissues and the return of deoxygenated blood.

  • Pulmonary circulation: deoxygenated bloodto the lung for oxxygenation and return to the heart

  • Portal circulation: role of the heptic portal system in nutrient transport and metabolism.

Blood vessels

  • Arteries: thick walls, high pressure, role in distributing oxygenated blood

  • Veins: thin walls, valves, role in returning deoxygenated blood

  • Capillaries: thin walls for nutrients, gas, and waste exchange

Arteries

  • Thick walls with elastic and muscular layers that enable them to withstand and regulate the high pressure of blood pumped from the hear.

  • Transport oxygenated blood to tissues, except for the pulmonary arteries

  • At any given time, only about 10-15% of blood is in the arteries.

Veins

  • Located throughout the body

  • Collect de-oxygenated blood and return to the heart, excp. pulmonary veins

  • Hold most of the body blood, 70-75%

    • deep veins

    • superficial veins

    • perforator veins

  • Thinner walls and larger lumens compared to arteries

  • Equipped with valves to prevent backflow of blood

    • Unidirectional flow toward the heart, esp. against gravity.

Capillaries

  • One-layer tissue

    • The walls consist of only 1 single layer of endothelial cells

  • Exchange driven by pressure differences - diffusion

  • Smallest and most numerous blood vessels in the body

The Lymphatic System

  • Lymphatic vessels + Lymph nodes

  • Roles

    • Fluid balance

    • Immunity

Hemodynamics (Blood flow and Pressure)

Factors affecting blood pressure

  • Cardiac output

  • Vessel diameter

Common Disorders related to Blood and Circulation

Anemia

  • Condition whre blood lacks enough healthy RBCs or hemoglobin to carry adequate oxygen to the body’s tissues.

  • Symptoms: fatigue, weakness, pale skin, and shortness of breath.

  • Caused by:

    • nutrient deficiencies: iron, B12, folate

    • chronic diseases: kidney failure, cancer

    • blood loss: bone marrow disorders or infections

    • genetic factors: sickle cell anemia

Hypertension

Mechanism

  • Increased cardiac output: heart pumps more forcefully > rasing pressure

  • Peripheral resistance: narrow or stiff blood vessels

  • RAAS dysfunction: over activation leads to vasoconstriction and fluid retention

  • Sympathetic overeactivity

  • Endothelial dysfunction: reduced vessel relaxation from nitric oxide imbalance

  • Sodium retention

  • Hormonal imbalance: e.g. cortisol increase vascular tone and output

  • Vessel changes: thickened arteries

Impacts

  • Heart: increases risks of heart attack, heart failure, and left ventricular hypertrophy

  • Blood vessels: artery damage, atherosclerosis, and aneurysms.

  • Brain: raises the risksof stroke, cognitive failure, and dementia.

  • Kidneys: leads to chronic kidney disease and failure

  • Eyes: can cause hypertensive retinopathy, vision loss, or blindness

  • Triggers fatigue,… premature death…

Hypotension

Mechanisms

  • Low Cardiac Output: Weak heart or low blood volume reduces pressure.

  • Excessive vessel widening lowers resistance and pressure.

  • Nerve Dysfunction: Impaired signals fail to maintain tone or heart rate.

  • Fluid Loss: Dehydration or blood loss decreases blood volume.

  • Hormonal Issues: Low aldosterone or cortisol reduces fluid retention.

  • Medications: Diuretics or beta-blockers may drop pressure too much.

  • Postural Changes: Standing suddenly causes blood pooling and pressure drops.

  • Severe Illness: Conditions like sepsis or shock drastically lower pressure.

Impacts

  • Brain: Dizziness, fainting, and cognitive impairment from reduced oxygen.

  • Heart: Insufficient blood flow can cause chest pain or heart damage.

  • Kidneys: Decreased perfusion may lead to kidney damage or failure.

  • Muscles: Weakness and fatigue due to poor oxygen supply.

    Overall: Risk of shock, organ failure, or death in severe cases.

Atherosclerosis

  • Narrowing of Arteries: Plaque buildup reduces blood flow.

  • Loss of Elasticity: Stiffened arteries increase blood pressure.

  • Impaired Circulation: Decreased oxygen and nutrients to tissues.

  • Risk of Blockages: Plaque rupture can lead to clots, causing heart attack or stroke.

  • Aneurysms: Weakened arterial walls may bulge or rupture.

Clotting disorders

  • Hemophilia: máu khó đông

  • Thrombosis: huyết khối