Key terms
102 terms- Circulatory system§48.1
- Organ system transporting O₂ and nutrients to cells and carrying wastes away
- Open circulatory system§48.1
- Circulating fluid is not distinct from extracellular fluid; drains into a body cavity
- Closed circulatory system§48.1
- Blood stays enclosed in vessels the entire way, moving in a loop
- Hemolymph§48.1
- The circulating fluid of an open system, identical to the extracellular fluid
- Gastrovascular cavity§48.1
- Cnidarian cavity that serves both digestion and circulation
- Pseudocoelom§48.1
- Body cavity whose fluid circulates materials in roundworms and rotifers
- Dorsal vessel§48.1
- Earthworm pump that pushes blood through five connecting arteries
- Plasma§48.2
- Fluid matrix of blood; about 92% water, 55% of mammalian blood volume
- Formed elements§48.2
- Erythrocytes, leukocytes, and platelets suspended in plasma
- Serum§48.2
- Plasma with the fibrinogen removed
- Albumin§48.2
- Most abundant plasma protein (54% of plasma protein), made by the liver
- Globulins§48.2
- Plasma proteins (38%) carrying lipids and steroid hormones
- Fibrinogen§48.2
- Soluble plasma protein (7%) converted to fibrin during clotting
- Erythrocyte§48.2
- Red blood cell; ~5 million/µL; carries hemoglobin and no nucleus in mammals
- Hematocrit§48.2
- Fraction of blood volume occupied by erythrocytes; ~45% in humans
- Buffy coat§48.2
- Thin centrifuge layer of platelets and leukocytes, under 1% of blood volume
- Leukocyte§48.2
- White blood cell; larger than an RBC, has a nucleus, can leave capillaries
- Granular leukocytes§48.2
- Neutrophils, eosinophils, basophils — named for stained cytoplasmic granules
- Agranular leukocytes§48.2
- Monocytes and lymphocytes
- Neutrophil§48.2
- Most numerous leukocyte (60–70%); performs phagocytosis
- Eosinophil§48.2
- Leukocyte (2–4%) active in allergic responses and parasitic infections
- Basophil§48.2
- Rarest leukocyte (0.5–1%); releases histamine for vasodilation in inflammation
- Lymphocyte§48.2
- Leukocyte (20–25%) producing antibodies and killing foreign invaders
- Monocyte§48.2
- Leukocyte (3–8%) that becomes a large macrophage in other tissues
- Platelet§48.2
- Cell fragment ~3 µm across, pinched off a megakaryocyte; essential to clotting
- Prothrombin§48.2
- Inactive liver-made clotting factor converted to thrombin
- Thrombin§48.2
- Enzyme that converts fibrinogen to fibrin; its activation is the cascade’s last step
- Fibrin§48.2
- Insoluble protein threads that trap erythrocytes and form the clot mesh
- Hematopoiesis§48.2
- Production of blood cells in bone marrow
- Pluripotent stem cell§48.2
- Marrow cell giving rise to both myeloid and lymphoid stem cells
- Erythropoietin§48.2
- Kidney-made hormone that stimulates red blood cell production when O₂ falls
- Megakaryocyte§48.2
- Large marrow cell whose cytoplasm fragments into platelets
- Sinus venosus§48.3
- First fish heart chamber and ancestral pacemaker; becomes the SA node
- Conus arteriosus§48.3
- Last fish heart structure; absorbed into the great arteries in reptiles
- Double circulation§48.3
- Two-loop design: pulmonary circuit plus systemic circuit
- Pulmonary circuit§48.3
- Blood flow between the heart and the lungs
- Systemic circuit§48.3
- Blood flow between the heart and all other body tissues
- Pulmocutaneous circuit§48.3
- Amphibian circuit sending blood to both lungs and skin
- Septum§48.3
- Wall dividing the ventricle; partial in most reptiles, complete in crocodilians
- Tricuspid valve§48.3
- Right atrioventricular valve, between right atrium and right ventricle
- Bicuspid (mitral) valve§48.3
- Left atrioventricular valve, between left atrium and left ventricle
- Semilunar valves§48.3
- Pulmonary and aortic valves guarding the ventricular outflows
- Venae cavae§48.3
- Superior and inferior veins returning oxygen-poor blood to the right atrium
- Aorta§48.3
- Largest systemic artery, leaving the left ventricle
- Convergent evolution§48.3
- Independent origin of the same trait — e.g. bird and mammal 4-chambered hearts
- Cardiac cycle§48.4
- One full heartbeat: atrial systole, ventricular systole, then diastole
- Systole§48.4
- Contraction phase of the cardiac cycle
- Diastole§48.4
- Relaxation phase of the cardiac cycle
- Auscultation§48.4
- Listening to heart sounds with a stethoscope near the sternum
- Murmur§48.4
- Abnormal heart sound, usually from a valve that fails to seal
- Mitral valve prolapse§48.4
- A mitral cusp balloons back in systole, leaking blood into the left atrium
- Autorhythmic fibers§48.4
- Self-exciting cardiac cells that generate their own action potentials
- Intercalated disks§48.4
- Junctions with gap junctions that spread depolarization cell to cell
- Plateau phase§48.4
- Ca²⁺-driven extension of the cardiac action potential, giving a longer contraction
- SA node§48.4
- Sinoatrial node in the right atrial wall; the pacemaker that starts every beat
- AV node§48.4
- Only conduction route from atria to ventricles; delays the signal about 0.1 sec
- AV bundle (bundle of His)§48.4
- Fast fibers carrying the signal across the interventricular septum
- Purkinje fibers§48.4
- Fibers that deliver the impulse directly to ventricular muscle
- ECG§48.4
- Electrocardiogram — recording of the heart’s electrical activity from skin electrodes
- P wave§48.4
- Atrial depolarization, just before atrial systole
- QRS complex§48.4
- Ventricular depolarization; hides atrial repolarization inside it
- T wave§48.4
- Ventricular repolarization, with all four chambers in diastole
- Cardiac output (CO)§48.4
- Volume one ventricle pumps per minute; CO = stroke volume × heart rate
- Stroke volume (SV)§48.4
- Blood ejected by one ventricle per beat, about 70 mL at rest
- End-diastolic volume§48.4
- Ventricular volume just before contraction, about 160 mL
- End-systolic volume§48.4
- Ventricular volume left after ejection, about 80 mL
- Blood pressure§48.5
- Force flowing blood exerts against vessel walls; written systolic/diastolic
- Sphygmomanometer§48.5
- Cuff device that measures arterial BP over the brachial artery
- Systolic pressure§48.5
- Peak arterial pressure during ventricular contraction (~120 mm Hg)
- Diastolic pressure§48.5
- Lowest arterial pressure during ventricular relaxation (~80 mm Hg)
- Hypertension§48.5
- Chronically high BP — systolic above 140 or diastolic above 90 mm Hg
- Baroreceptors§48.5
- Stretch receptors in the aortic arch and carotid arteries that sense BP
- Renin§48.5
- Kidney enzyme released under low blood flow; activates angiotensin
- Angiotensin§48.5
- Blood protein causing vasoconstriction and triggering aldosterone release
- Aldosterone§48.5
- Adrenal cortex hormone driving Na⁺ and water retention by the kidneys
- Atrial natriuretic peptide (ANP)§48.5
- Hormone from the stretched right atrium; promotes Na⁺ excretion, lowers BP
- Nitric oxide (NO)§48.5
- Endothelium-made gas that relaxes vessel smooth muscle, causing dilation
- Endothelium§48.5
- Single-cell-layer inner lining present in every blood vessel
- Arteriole§48.5
- Smallest arterial branch; the main resistance vessel of the body
- Venule§48.5
- Smallest venous branch, collecting blood leaving the capillaries
- Fenestrated capillary§48.5
- Capillary whose wall carries pores for greater exchange
- Sinusoid§48.5
- Capillary with large gaps, found in liver, spleen, and bone marrow
- Vasoconstriction§48.5
- Smooth muscle contraction narrowing a vessel; raises resistance, cuts flow
- Vasodilation§48.5
- Smooth muscle relaxation widening a vessel; lowers resistance, raises flow
- Precapillary sphincter§48.5
- Muscular ring gating blood entry into an individual capillary bed
- Venous pump§48.5
- Skeletal muscle contractions squeezing veins to drive blood toward the heart
- Venous valves§48.5
- One-way flaps in veins that prevent backflow
- Varicose veins§48.5
- Overstretched veins whose valves no longer seal, so blood pools
- Interstitial fluid§48.6
- Fluid filtered out of capillaries into the spaces around cells
- Edema§48.6
- Tissue swelling from excess interstitial fluid
- Lymphatic system§48.6
- Open-ended, one-way network returning excess tissue fluid to the blood
- Lymph§48.6
- Interstitial fluid once it has entered the lymphatic vessels
- Lymph node§48.6
- Lymphatic organ that filters lymph and activates lymphocytes
- Lymph hearts§48.6
- Contractile pumps for lymph in amphibians, reptiles, some fish and birds
- Atherosclerosis§48.7
- Fat, cholesterol, muscle, and debris buildup narrowing the artery lumen
- Arteriosclerosis§48.7
- Calcium deposits hardening artery walls so they cannot expand
- LDL§48.7
- Lipoprotein delivering cholesterol to cells; the "bad" cholesterol carrier
- HDL§48.7
- Lipoprotein carrying cholesterol to the liver for disposal; the "good" one
- Myocardial infarction§48.7
- Heart attack — death of heart muscle from blocked blood supply
- Angina pectoris§48.7
- Chest pain from an inadequate but not fully blocked coronary supply
- Ischemic stroke§48.7
- Brain artery blocked by a clot or atherosclerosis
- Hemorrhagic stroke§48.7
- A brain vessel bursts, interrupting blood supply