EEMB 7 Chapters 34-35 Flashcards: Circulation, Gas Exchange, and Immunity

Vocabulary flashcards covering circulatory systems, heart anatomy, blood components, gas exchange, breathing mechanisms, innate immunity, and adaptive immunity based on EEMB 7 Chapters 34 and 35.

Diffusion

Net movement of molecules from higher to lower concentration because of random molecular motion; effective only across short distances.

Gastrovascular cavity

Digestive compartment that also distributes nutrients through the body; it has one opening and no separate circulatory system.

Heart

Muscular pump that generates pressure to move circulatory fluid through vessels or body spaces.

Open circulatory system

The heart pumps hemolymph through vessels into body spaces, where it directly bathes organs; hemolymph is not kept separate from interstitial fluid.

Hemolymph

Circulatory fluid in an open system; it combines functions of blood and interstitial fluid.

Closed circulatory system

Blood remains inside vessels and is kept separate from interstitial fluid, allowing higher pressure and controlled delivery.

Blood

Connective tissue consisting of plasma plus formed elements: erythrocytes, leukocytes, and platelets.

Open vs. closed circulation

Open systems operate at lower pressure with less precise flow; closed systems support higher pressure, faster transport, and targeted flow.

Atria

Heart chambers that receive blood returning to the heart.

Ventricles

Heart chambers that pump blood out of the heart; their walls are thicker than atrial walls.

Single circulation

Blood passes through the heart once per complete circuit, as in fishes: heart -> gills -> body -> heart.

Double circulation

Blood passes through the heart twice per complete circuit: pulmonary and systemic circuits.

Cardiac cycle

One complete sequence of heart contraction and relaxation.

Systole

Contraction phase of a heart chamber; ventricular systole ejects blood.

Diastole

Relaxation phase during which heart chambers fill with blood.

Atrioventricular (AV) valve

Valve between an atrium and ventricle that prevents blood from flowing backward into the atrium.

Semilunar valve

Valve between a ventricle and an artery that prevents arterial blood from flowing back into the ventricle.

Heart valve opening and closing mechanism

Pressure differences cause valves to operate; valves open when pressure behind them is greater and close when pressure in front becomes greater.

Sinoatrial (SA) node

Pacemaker in the right atrium that spontaneously generates impulses and sets heart rhythm.

Electrocardiogram (ECG/EKG)

Recording of electrical activity produced during the cardiac cycle.

Atrioventricular (AV) node

Conduction tissue that briefly delays the impulse, allowing atria to finish contracting before ventricles contract.

Electrical conduction sequence

SA node -> atria contract -> AV node delay -> conducting fibers -> ventricles contract from apex upward.

Blood-flow sequence through the human heart

Body -> venae cavae -> right atrium -> right ventricle -> pulmonary artery -> lungs -> pulmonary veins -> left atrium -> left ventricle -> aorta -> body.

Pulse

Rhythmic stretching of arteries caused by pressure waves from ventricular contraction.

Vasoconstriction

Narrowing of arterioles due to smooth-muscle contraction; decreases local blood flow and increases resistance.

Vasodilation

Widening of arterioles due to smooth-muscle relaxation; increases local blood flow and decreases resistance.

Lymphatic system

Network that returns excess interstitial fluid to blood, transports absorbed fats, and contributes to immune defense.

Lymph

Interstitial fluid after it enters lymphatic vessels.

Lymph nodes

Structures along lymph vessels that filter lymph and contain immune cells.

Plasma

Liquid matrix of blood containing water, ions, proteins, nutrients, hormones, gases, and wastes.

Platelets

Cell fragments that help form blood clots and seal damaged vessels.

Stem cells

Unspecialized bone-marrow cells that self-renew and produce all blood-cell lineages.

Erythrocytes

Red blood cells specialized to transport oxygen using hemoglobin; mammalian erythrocytes lack nuclei when mature.

Hemoglobin

Iron-containing respiratory protein in erythrocytes that reversibly binds oxygen.

Sickle-cell disease

Inherited hemoglobin disorder in which low oxygen can make red blood cells sickle, block vessels, and break down.

Leukocytes

White blood cells that function in immune defense and can leave capillaries to enter tissues.

Atherosclerosis

Chronic buildup of lipid-rich plaques in artery walls, narrowing arteries and increasing clot risk.

Heart attack

Death of heart muscle caused by blocked coronary blood flow; also called myocardial infarction.

Stroke

Brain injury caused by interrupted blood flow or a ruptured vessel in the brain.

Low-density lipoprotein (LDL)

Particle that delivers cholesterol from the liver to tissues; high levels promote plaque formation, so it is often called bad cholesterol.

High-density lipoprotein (HDL)

Particle that carries excess cholesterol from tissues toward the liver; higher levels are generally protective, so it is often called good cholesterol.

Atherosclerosis complications

Plaque may narrow or rupture in an artery, triggering a clot that blocks blood flow to heart muscle or brain tissue.

Partial pressure

Pressure contributed by one gas in a mixture; gases diffuse from higher to lower partial pressure.

Ventilation

Bulk movement of the respiratory medium over a gas-exchange surface.

Countercurrent exchange

Adjacent fluids move in opposite directions, maintaining a diffusion gradient across the entire exchange surface.

Lungs

Internal respiratory organs where air exchanges $\text{O}_2$ and $\text{CO}_2$ with blood.

Larynx

Voice box between pharynx and trachea; contains vocal cords and protects the airway.

Trachea

Windpipe carrying air from the larynx toward the bronchi.

Bronchi

Two main branches of the trachea that enter the lungs and divide into smaller bronchioles.

Alveoli

Tiny lung air sacs with thin, moist walls and dense capillaries; main sites of gas exchange.

Surfactant

Substance coating alveoli that reduces surface tension and prevents collapse.

Air pathway

Nose/mouth -> pharynx -> larynx -> trachea -> bronchi -> bronchioles -> alveoli.

Breathing

Alternating inhalation and exhalation that ventilates lungs.

Positive-pressure breathing

Air is pushed into lungs because pressure in the mouth or respiratory cavity rises above atmospheric pressure.

Negative-pressure breathing

Expansion of the thoracic cavity lowers lung pressure below atmospheric pressure, pulling air inward.

Diaphragm

Dome-shaped skeletal muscle; contraction flattens it, increasing thoracic volume and drawing air into mammalian lungs.

Inhalation mechanics

Diaphragm contracts, thoracic volume increases, lung pressure falls, and air flows inward.

Exhalation mechanics at rest

Diaphragm relaxes, elastic recoil reduces thoracic volume, lung pressure rises, and air flows outward.

Tidal volume

Air inhaled or exhaled during one normal breath.

Vital capacity

Maximum air that can be expelled after a maximum inhalation.

Residual volume

Air remaining in lungs after the strongest possible exhalation; prevents complete lung collapse.

Respiratory pigments

Proteins that reversibly bind gases and greatly increase transport capacity, such as hemoglobin.

Myoglobin

Oxygen-binding protein in muscle that stores oxygen and facilitates its movement to mitochondria.

Pathogen

Disease-causing organism, virus, or other infectious agent.

Immune system

Cells, tissues, and molecules that recognize and defend against pathogens and abnormal cells.

Innate immunity

Rapid, nonspecific defenses present before infection; includes barriers, recognition receptors, phagocytes, inflammation, complement, and natural killer cells.

Adaptive immunity

Pathogen-specific defense mediated by B and T lymphocytes; develops after exposure and produces immunological memory.

Lysozyme

Antimicrobial enzyme in tears, saliva, and mucus that breaks bacterial cell walls.

Phagocytosis

Cellular engulfment and digestion of particles, microbes, or debris.

Toll-like receptor

Innate immune receptor that recognizes conserved pathogen-associated molecules and triggers defensive responses.

Neutrophils

Abundant, short-lived phagocytic leukocytes that arrive early at infection sites.

Macrophages

Large tissue phagocytes that engulf pathogens and debris, release cytokines, and can present antigens.

Natural killer cells

Innate lymphocytes that kill virus-infected and cancerous cells without prior antigen-specific activation.

Interferons

Signaling proteins released especially by virus-infected cells that help nearby cells resist viral replication.

Complement system

Set of plasma proteins activated in a cascade to enhance inflammation, coat pathogens, and sometimes lyse them.

Inflammatory response

Local innate response causing redness, heat, swelling, and pain; recruits immune cells and limits damage.

Cytokines

Small signaling proteins that coordinate immune-cell activation, movement, growth, and communication.

Histamine

Inflammatory mediator released mainly by mast cells; dilates vessels and increases capillary permeability.

Innate vs. adaptive immunity

Innate: immediate, broad recognition, little specific memory. Adaptive: slower first response, antigen-specific, strong memory.

Lymphocytes

White blood cells central to adaptive immunity, especially B cells and T cells.

Thymus

Organ where T lymphocytes mature and are selected.

T cells

Lymphocytes responsible for cell-mediated immunity; recognize antigen fragments displayed on MHC molecules.

B cells

Lymphocytes that can become antibody-secreting plasma cells and memory B cells.

Antigen

Molecule or molecular structure specifically recognized by an adaptive immune receptor.

Antigen receptor

Unique membrane receptor on a B or T cell that binds a particular antigen or antigen-MHC complex.

Epitope

Specific accessible part of an antigen recognized by an antibody or antigen receptor.

Light chains

Two smaller polypeptide chains of an antibody; with heavy chains, they form antigen-binding sites.

Antibody

Y-shaped protein secreted by plasma cells that binds a specific antigen.

Immunoglobulin

Another term for antibody; also refers to the B-cell antigen-receptor protein family.

Major histocompatibility complex (MHC)

Cell-surface proteins that display peptide fragments for recognition by T cells.

Antigen presentation

Display of antigen fragments bound to MHC molecules on a cell surface.

Effector cells

Activated lymphocytes that perform an immediate immune function, such as plasma cells or cytotoxic T cells.

Plasma cells

Effector B cells that secrete large quantities of antibodies.

Memory cells

Long-lived antigen-specific B or T cells that respond rapidly upon later exposure.

Clonal selection

An antigen activates only lymphocytes with matching receptors; those cells proliferate into effector and memory clones.

Primary immune response

Slower, smaller response after first exposure because rare matching lymphocytes must be selected and expanded.

Secondary immune response

Faster, larger, and longer response after re-exposure because memory cells are already present.

Humoral immune response

B-cell and antibody response against pathogens and toxins in body fluids.

Cell-mediated immune response

T-cell response against infected, cancerous, transplanted, or otherwise abnormal cells.

Antigen-presenting cell (APC)

Cell such as a dendritic cell, macrophage, or B cell that displays antigen on MHC to activate T cells.