BIOL 21 Midterm II: Blood, Heart, and Blood Vessels

Vocabulary practice flashcards covering cardiovascular anatomy, blood composition, formed elements, hemodynamics, and cardiovascular pathologies from the BIOL 21 Midterm II study guide.

Cardiac cycle

The sequence of events in a heartbeat consisting of diastole (relaxation; blood enters both atria), atrial systole (atria contract and fill the ventricles), and ventricular systole (ventricles contract and eject blood; atria relax).

Diastole

The relaxation phase of the cardiac cycle during which blood enters both atria.

Atrial systole

The phase of the cardiac cycle in which the atria contract to fill the ventricles.

Ventricular systole

The phase of the cardiac cycle in which the ventricles contract and eject blood while the atria relax.

Arteries

Thick, muscular blood vessels that carry blood away from the heart.

Arterioles

Small arterial vessels that serve as the prime controllers of blood pressure.

Capillaries

Extremely narrow vessels with one-cell-thick walls containing slits and pores through which red blood cells move single file, allowing exchange of gases, nutrients, and waste.

Veins

Blood vessels with thinner walls, larger lumens, and valves that return blood to the heart and serve as a reservoir for blood volume.

Capillary beds

Networks that serve as the site of exchange where $O_2$, nutrients, and raw materials exit the blood to tissue cells, while $CO_2$ and wastes enter the blood.

Precapillary sphincters

Rings of smooth muscle that regulate blood flow into the capillary bed.

Venous valves

One-way flaps that prevent the backflow of blood in low-pressure veins, especially in the legs where blood travels upward against gravity.

Pulmonary pathway

The circulatory route from the heart to the lungs and back; the right side of the heart pumps deoxygenated blood to the lungs to drop off $CO_2$ and pick up $O_2$, returning oxygenated blood to the left atrium.

Systemic pathway

The circulatory route from the heart to body tissues and back; the left side of the heart pumps oxygenated blood through the aorta to tissues, returning deoxygenated blood through the vena cavae to the right atrium.

Blood plasma

The fluid portion making up approximately $55\%$ of blood, consisting of $90\text{--}92\%$ water, $7\text{--}8\%$ plasma proteins (albumin, fibrinogen, immunoglobulins), and $<1\%$ salts.

Buffy coat

The fraction of centrifuged blood accounting for approximately $1\%$ of total volume, composed of white blood cells and platelets.

Red bone marrow

The primary tissue where all blood cells are produced from stem cells.

Neutrophils

The most abundant white blood cells ($3{,}000\text{--}7{,}000\,\text{per mm}^3$) and granular leukocytes that are the first to fight infection from bacteria and some fungi.

Eosinophils

Granular leukocytes present at $100\text{--}400\,\text{per mm}^3$ ($\sim 2\text{--}4\%$) that defend against parasites and release chemicals to reduce allergic reactions.

Basophils

The rarest white blood cells ($20\text{--}50\,\text{per mm}^3$) and granular leukocytes that secrete histamine in response to allergic reactions.

Lymphocytes

Agranular leukocytes with counts of $1{,}500\text{--}3{,}000\,\text{per mm}^3$ ($\sim 30\%$) that function in the lymphatic system, including tonsils, spleen, lymph nodes, thymus, and bloodstream.

Monocytes

The largest agranular leukocytes ($100\text{--}700\,\text{per mm}^3$; $\sim 5\%$) that differentiate into macrophages to destroy pathogens and stimulate other white blood cells.

Red blood cells (Erythrocytes)

Biconcave discs without nuclei ($7\text{--}8\,\mu\text{m}$; $4\text{--}6\times 10^6\,\text{per mm}^3$) containing hemoglobin, which binds four $O_2$ molecules to transport oxygen throughout the body and assists in transporting $CO_2$.

Platelets (Thrombocytes)

Anucleated, disk-shaped cell fragments ($2\text{--}4\,\mu\text{m}$; $150{,}000\text{--}300{,}000\,\text{per mm}^3$) derived from megakaryocytes in red bone marrow that aid in blood clotting to prevent blood loss.

Erythropoietin

A hormone released by the kidneys in response to low oxygen availability that stimulates stem cells in red bone marrow to produce red blood cells.

Systolic pressure

The arterial blood pressure during ventricular contraction, representing the top number in a blood pressure reading (normally approximately $120\,\text{mmHg}$).

Diastolic pressure

The arterial blood pressure when the ventricles are relaxed, representing the bottom number in a blood pressure reading (normally approximately $80\,\text{mmHg}$).

Heart attack

A condition in which blood supply to part of the heart muscle is severely reduced or stopped, typically from plaque buildup, causing permanent injury and death of heart muscle cells.

Stroke

A condition caused by blocked or burst arteries leading to and within the brain, depriving brain tissue of oxygen.