Human Circulatory System Quiz

Circulatory System and Lymphatic System

• The circulatory system is crucial for multicellular organisms, bringing nutrients to cells and removing wastes.
• In humans, the circulatory system is vital; cessation of heartbeat for a few minutes is fatal.
• This unit explores the heart, major vessels, blood (including immunity), the lymphatic system, and related disorders.

Blood Vessels

• Blood vessels are categorized into three types: arteries, capillaries, and veins.
• Arteries carry O2-rich blood away from the heart.
• Capillaries facilitate material exchange with tissues.
• Veins return blood from capillaries to the heart.

Arteries

• The aorta is the largest artery in the body, carrying oxygenated blood from the heart to the rest.
• Arterial walls are composed of three layers: endothelium, smooth muscle, and fibrous connective tissue.
• The smooth muscle layer regulates blood flow and pressure.

Arterioles

• Arterioles are small arteries that branch off from larger arteries.
• They also have three layers: endothelium, smooth muscle (mostly), and connective tissue.
• Smooth muscle contraction increases blood pressure by constricting the vessels.
• Relaxation of smooth muscle lowers blood pressure.

Capillaries

• Microscopic blood vessels connecting arterioles to venules, facilitating material exchange with tissues.
• Single layer of epithelium with a basement membrane forms vast networks throughout the body.
• Only some capillary beds are open at any given time, regulated by sphincter muscles.

Veins

• Veins and venules return blood from the capillaries to the heart.
• Veins have similar layers to arteries, but with less smooth muscle and connective tissue.
• Veins contain valves, aiding one-way blood flow toward the heart.
• Veins act as a blood reservoir (about 70% of blood).
• The venae cavae (superior and inferior) are the largest veins in the body, returning deoxygenated blood to the heart.

Blood

• Blood is a liquid connective tissue with multiple functions: transportation of nutrients, wastes, hormones; regulation of body temperature and blood pressure; protection against disease-causing pathogens; and clotting.

Composition of Blood

• Blood separates into three layers upon centrifugation: plasma (liquid portion), leukocytes and platelets, and erythrocytes.
• Plasma is about 55% of whole blood, containing water, proteins, salts, gases, nutrients.
• Formed elements include leukocytes (<1%), platelets (<1 %), and erythrocytes (about 45%).

Red Blood Cells (Erythrocytes)

• Manufactured in red bone marrow; transport O2 and CO2.
• Biconcave shape increases flexibility to pass through capillaries, and surface area for gas diffusion.
• Contain hemoglobin, a respiratory pigment with iron that picks up oxygen in the lungs, and releases it in tissues.
• Their lifespan is about 120 days, and they are destroyed in the liver and spleen.

Anemia

• Anemia is a blood disorder marked by tiredness and a rundown feeling. It can result from decreased or lost red blood cells or destruction within the body.
• Most common type is iron-deficiency anemia.

White Blood Cells (Leukocytes)

• Larger than red blood cells, they have a nucleus and lack hemoglobin.
• They're translucent without staining; fight infection and play a role in immunity.
• Granular leukocytes include neutrophils, eosinophils, basophils.
• Agranular leukocytes include monocytes and lymphocytes (B cells and T cells).

Platelets and Blood Clotting

• Platelets (thrombocytes) fragment from megakaryocytes in the red bone marrow.
• They are crucial for blood clotting (coagulation).
• Clotting factors (like prothrombin and fibrinogen) participate in the cascade of enzymatic reactions that result in blood clot formation.

Blood Clotting Process

• Initiated when a blood vessel is damaged, with platelets forming a plug to partially seal the leak.
• Prothrombin is converted to thrombin by prothrombin activator; thrombin converts fibrinogen into fibrin threads.
• Fibrin threads trap red blood cells, forming the framework of the clot.
• Plasmin dissolves the fibrin framework when repair initiates.

Blood Clotting Disorders

• Hemophilia is a group of inherited clotting disorders.
• Hemophilia A is the most common type.

Bone Marrow Stem Cells

• Stem cells have the ability to self-renew and differentiate into specialized cell types.
• Multipotent stem cells in red bone marrow give rise to specific stem cells for blood elements.

Capillary Exchange

• Fluid movement in blood (plasma) and tissue fluid is regulated by osmotic pressure from the tissue fluid to the blood, and blood pressure from the blood to the tissue fluid.

Arterial End of Capillary

• Higher blood pressure than osmotic pressure.
• Water moves out of the capillary.

Midway Along the Capillary

• Blood pressure and osmotic pressure cancel each other out.
• No net movement of water; solutes diffuse along concentration gradients (O2 and nutrients out, and wastes and CO2 in).

Venous End of Capillary

• Osmotic pressure is greater than blood pressure.
• Water enters the capillary.
• Excess tissue fluid becomes lymph and is taken up by lymphatic capillaries.

Pulmonary Circuit

• Blood from the body enters the right atrium.
• Blood flows through the right ventricle, pulmonary trunk, pulmonary arteries, capillaries (lungs - gas exchange), pulmonary venules, pulmonary veins, and then finally to the left atrium.

Systemic Circuit

• Oxygenated blood from the left ventricle goes to the aorta and into the body.
• Blood flows to various organs (through arteries, arterioles, capillaries), and then back to the heart through venules and veins.
• Finally, blood returns to the right atrium.

Lymphatic System

• Consists of lymphatic vessels and lymphoid organs, closely associated with the circulatory system.
• Three key functions: absorption of excess tissue fluid (returning it to the bloodstream), absorbing fats from the digestive tract and transporting them to the bloodstream, and defending the body against disease (by lymphoid organs).

Lymphoid Organs

• There are primary and secondary lymphoid organs.
• Primary: red bone marrow and thymus (where lymphocytes develop).
• Secondary: lymph nodes and spleen (where lymphocytes become activated).

Innate and Adaptive Immunity

• The lymphatic system works with the immune system to protect the body from pathogens, toxins, and other invaders.
• Innate response is rapid and non-specific.
• Adaptive response is slower and specific.

Physical and Chemical Barriers

• Physical: skin, mucous membranes
• Chemical: oils, acidic pH of stomach, bacteria in the intestine

Inflammatory Response

• A series of events occurring when tissue is damaged.
• Signs of inflammation: redness, heat, swelling, pain.
• Mast cells release histamine.
• Macrophages and dendritic cells release cytokines.

Phagocytes and Natural Killer Cells

• Phagocytes engulf invaders into an endocytic vesicle; neutrophils and monocytes are examples.
• Natural killer cells (NK cells) kill some virus-infected cells and cancer cells using cell-to-cell contact.

Adaptive Immunity

• Activated when innate defenses fail.
• The adaptive immune system recognizes, responds to, and eliminates antigens.
• Antigens are molecules that stimulate an adaptive immune response.

B Cells

• Activated in lymph nodes or spleen when their receptors bind to antigens.
• Produce antibodies (the secreted form of their receptor).
• Some B cells become memory B cells, providing long-term immunity.

Antibody Structure

• Antibodies are also called immunoglobulins.
• Y-shaped molecules with heavy and light polypeptide chains.

Circulatory System Disorders

• Atherosclerosis: accumulation of fatty materials (plaque) within artery walls.
• Hypertension: abnormally high blood pressure.
• Heart valve disease: malformed or degenerated heart valves.
• Stroke: blood flow interruption in the brain.
• Heart attack (myocardial infarction): portion of the heart muscle dies due to lack of oxygen.
• Aneurysm: a ballooning of a blood vessel.

Treatment for Cardiovascular Disorders

• Coronary bypass surgery: grafting vessels to bypass obstructed coronary arteries.
• Stents: metal mesh tubes placed in arteries to keep them open.
• tPA: enzyme that dissolves blood clots.
• Aspirin: lowers platelet stickiness, decreasing clot formation.

Stem Cells

• Stem cells can be used to regenerate damaged heart muscle.
• May be used in growing "bio-artificial" hearts.

Clearing Clogged Arteries

• Angioplasty: catheter with a balloon is used to open the arteries.
• Stents: metal mesh tubes keep arteries open.

Additional Notes

• Many details about specific processes, substances, and diseases can be noted from the provided text.

Test your knowledge of the human circulatory system with this quiz. Questions cover blood components, vessel types, and their functions. Understand the intricate workings of how blood circulates through the body.