Circulation and Gas Exchange - Flashcards

Components of Blood

  • Blood is a connective tissue with a fluid matrix called plasma, containing cells and formed elements.

  • Functions of blood:

    1. Transportation of materials.

    2. Regulation of body functions.

    3. Protection from injury and invasion.

Blood Components

  1. Red blood cells (erythrocytes):

    • Contain hemoglobin for oxygen transport.

    • Mature mammalian erythrocytes lack nuclei.

  2. White blood cells (leukocytes):

    • Larger than erythrocytes and have nuclei.

    • Can migrate out of capillaries. a. Granular leukocytes:

      • Neutrophils, eosinophils, and basophils (named by staining properties).
        b. Agranular leukocytes:

      • Monocytes and lymphocytes.

  3. Platelets:

    • Function in blood clot formation.

Blood Composition

  • Blood = Plasma + RBCs + WBCs + platelets

  • Plasma: Blood without cells.

  • Serum: Plasma without clotting factors.

Hematopoiesis

  • All formed elements develop from pluripotent stem cells.

  • Hematopoiesis: Blood cell production in bone marrow.

Mammalian Blood Composition

  • Plasma: 55% (water, ions, proteins like albumin and immunoglobulins, transported substances).

  • Cellular elements: 45% (leukocytes, platelets, erythrocytes).

Leukocytes

  • Number per microliter: 5,000-10,000.

  • Functions: Defense and immunity.

  • Types: Lymphocytes, basophils, neutrophils, eosinophils, monocytes.

Platelets

  • Number per microliter: 250,000-400,000.

  • Function: Blood clotting.

Erythrocytes

  • Number per microliter: 5,000,000-6,000,000.

  • Function: Transport of O2 and some CO2.

Hematopoiesis Details

  • Lymphoid stem cell -> Lymphocytes.

  • Myeloid stem cell -> All other blood cells.

  • Erythropoiesis: Red blood cell production.

    • Kidney produces erythropoietin, stimulating erythrocyte production.

    • Old cells/fragments are digested in the spleen; iron and amino acids are recycled.

Cell Division and Differentiation

  • Blastomeres: Nondifferentiated cells.

Stem Cells

  • Tissue-specific: Give rise to one tissue.

  • Pluripotent: Give rise to multiple cell types.

  • Totipotent: Give rise to any cell type.

Cell Fate

  • Determination: Cell commitment to a specific fate.

  • Differentiation: Resulting specialization in structure and function.

Mitotic Cell Division

  • Cleavage divisions: Rapid mitotic divisions increasing cell number but not size.

  • Stem cell divisions: Replenish needed cells like blood cells.

  • Patterning divisions: Daughter cells take on different fates.

Circulatory Systems

  • Link exchange surfaces with cells throughout the body.

  • Simple body plans: Cells in direct contact with the environment.

  • Most animals: Circulatory system linked to gas exchange and body cells.

Direct Exchange

  • Some animals exchange directly with the environment.

Invertebrate Circulatory Systems

  • Sponges, cnidarians, and nematodes lack a separate circulatory system.

    • Sponges: Water circulation via ostia (incurrent pores) and osculum (excurrent pore).

    • Hydra/Cnidarians: Water circulation via gastrovascular cavity (also for digestion).

    • Nematodes: Use digestive tract as circulatory system.

Larger Animals

  • Require separate circulatory system for nutrient/waste transport due to thick tissues.

Types of Circulatory Systems

  • Open circulatory system: No distinction between circulating and extracellular fluid (hemolymph).

  • Closed circulatory system: Distinct circulatory fluid enclosed in blood vessels.

Components of Circulatory System

  • Circulatory fluid.

  • Interconnecting vessels.

  • Muscular pump (heart).

Open vs. Closed

  • Open: Hemolymph bathes organs directly (insects, arthropods, some molluscs).

  • Closed: Blood confined to vessels (annelids, cephalopods, vertebrates).

Open Circulation in Insects

  • Hemolymph pumped from tubular heart into body cavities, then returns to vessels.

Closed Circulation in Earthworms

  • Blood pumped from hearts remains within vessels.

  • All vertebrates have closed circulatory systems.

Vertebrate Circulatory Systems

Single Circulation

  • Sharks, rays, bony fishes have single circulation with a two-chambered heart.

  • Blood passes through two capillary beds before returning to the heart.

Fish Heart

  • Evolved a true chamber-pump heart.

  • Four structures form two pumping chambers: Sinus venosus, atrium, ventricle, conus arteriosus.

  • Contraction sequence: sinus venosus -> atrium -> ventricle -> conus arteriosus.

  • Blood flows through gills, then to the body.

  • Electrical impulse initiates in the sinus venosus (SA node in other vertebrates).

Double Circulation

  • Amphibians: Pulmonary circulation (heart and lungs) and systemic circulation (heart and body).

  • Pulmonocutaneous circuit in amphibians sends blood to lungs and skin.

Frog Heart

  • Three-chambered heart (two atria, one ventricle).

  • Oxygenated and deoxygenated blood mix very little.

Reptile Heart

  • Septum partially subdivides the ventricle.

Mammalian, Bird, and Crocodilian Heart

  • Four-chambered heart (two atria, two ventricles).

  • Right atrium: Receives deoxygenated blood and delivers it to the right ventricle -> lungs.

  • Left atrium: Receives oxygenated blood and delivers it to the left ventricle -> rest of the body.

Evolutionary Variation

  • Four-chambered heart in mammals and birds separates oxygen-rich and oxygen-poor blood.

  • Endotherms require more energy than ectotherms.

Cardiovascular System of Vertebrates

  • Humans have a closed cardiovascular system with a heart and blood vessels.

  • Three types of blood vessels: arteries, veins, capillaries.

  • Blood flows one way.

Blood Vessel Organization

  • Arteries -> arterioles -> capillaries (chemical exchange between blood and interstitial fluid).

  • Capillaries converge into venules -> veins.

Arteries vs Veins

  • Distinguished by blood flow direction, not oxygen content.

  • Hearts have atria (blood entry) and ventricles (blood exit).

Mammalian Circulation

  • Right ventricle pumps blood to lungs via pulmonary arteries.

  • Oxygen-rich blood returns to the left atrium via pulmonary veins.

  • Left ventricle pumps blood to body tissues via the aorta.

  • Coronary arteries supply the heart muscle.

  • O2 diffuses from blood to tissues, CO2 diffuses from tissues to blood.

  • Capillaries rejoin to form venules -> veins.

  • Superior vena cava: Drains head, neck, and forelimbs.

  • Inferior vena cava: Drains trunk and hind limbs.

  • Venae cavae empty into the right atrium.

Cardiac Cycle

Two Contraction Cycles

  1. Atrial contraction.

  2. Ventricular contraction.

  • Includes resting period.

Systole and Diastole

  • Systole: Contraction or pumping phase.

  • Diastole: Relaxation or filling phase.

Heart Valves

Atrioventricular (AV) Valves

  • Between atria and ventricles.

    • Tricuspid (right).

    • Bicuspid or mitral (left).

Semilunar Valves

  • Guard exits from ventricles.

    • Pulmonary (right).

    • Aortic (left).

Lub-Dub Sounds

  • Lub: AV valves close during ventricular contraction.

  • Dub: Semilunar valves close during ventricular relaxation.

Blood Flow

  • Right and left pulmonary arteries deliver deoxygenated blood to the lungs.

  • Pulmonary veins return oxygenated blood to the left atrium.

  • Aorta and its branches (systemic arteries) carry oxygen-rich blood to the body.

  • Superior vena cava drains upper body.

  • Inferior vena cava drains lower body.

Blood Pressure Measurement

Sphygmomanometer

  • Systolic pressure: Peak pressure during ventricular contraction.

  • Diastolic pressure: Minimum pressure between heartbeats.

  • Typical blood pressure: 120/75 mm Hg.

Heartbeat Initiation

  • Autorhythmic cells initiate heart muscle contraction.

  • Sinoatrial (SA) node: Pacemaker in right atrium wall.

SA Node

  • Produces spontaneous action potentials.

  • Depolarization travels to the atrioventricular (AV) node.

  • Conducted over ventricles by atrioventricular bundle (bundle of His).

  • Relayed to Purkinje fibers stimulating myocardial cells to contract.

Electrocardiogram (ECG or EKG)

  • P wave: Atrial depolarization (atrial systole).

  • QRS complex: Ventricular depolarization (ventricular systole).

  • T wave: Ventricular repolarization (ventricular diastole).

Pacemaker Regulation

  • Sympathetic division speeds up pacemaker.

  • Parasympathetic division slows down pacemaker.

Blood Vessels

Types

Arteries

  • Carry blood away from the heart.

Arterioles

  • Microscopic branches of the arterial tree.

Capillaries

  • Where blood from arterioles enters.

Venules

  • Collect blood.

Veins

  • Carry blood back to the heart.

Structure

All Vessels

  • Endothelium-lined lumen (minimizes resistance).

Capillaries

  • Thin walls (endothelium + basal lamina).

Arteries and Veins

  • Endothelium, smooth muscle, connective tissue.

Arteries

  • Thick, elastic walls (high pressure).

Veins

  • Thinner walls, valves (unidirectional flow).

Tissue Layers

  • Endothelium, elastic fibers, smooth muscle, and connective tissue.

Capillaries

  • Single layer of endothelial cells.

Blood Pressure

Systolic Pressure

  • Pressure in arteries during ventricular systole.

Diastolic Pressure

  • Pressure in arteries during diastole.

Regulation

  • Homeostatic mechanisms alter arteriole diameter.

Vasoconstriction

  • Narrowing of arteriole walls increases blood pressure.

Vasodilation

  • Increased diameter of arterioles causes blood pressure to fall.

Veins and Venules

Characteristics

  • Thinner smooth muscle layer.

  • Return blood via skeletal muscle contractions and venous valves.

Lymphatic System

Components

  • Lymphatic capillaries, vessels, nodes, and organs.

  • Excess fluid drains into lymph capillaries -> larger vessels (one-way valves) -> subclavian veins.

  • Lymph nodes contain germinal centers (lymphocyte activation).

Cardiovascular Diseases

Heart Attacks (Myocardial Infarctions)

  • Insufficient blood supply to the heart.

Angina Pectoris

  • Chest pain (less severe than a heart attack).

Stroke

  • Interference with blood supply to the brain.

Atherosclerosis

  • Accumulation of fatty material within arteries.

Arteriosclerosis

  • Arterial hardening due to calcium deposition.

Blood Flow and Blood Pressure Regulation

Autonomic Nervous System

  • Norepinephrine (sympathetic) increases heart rate.

  • Acetylcholine (parasympathetic) decreases heart rate.

Cardiac Output (CO)

  • Volume of blood pumped per ventricle per minute.

  • Increases during exertion.

  • Arterial blood pressure (BP) = CO x Resistance (R).

  • BP = CO
    eq R

Baroreceptor Reflex

  • Negative feedback loop responding to BP changes.

  • Baroreceptors detect changes in arterial BP.

  • Decreased BP -> decreased impulses to cardiac center -> BP increase.

  • Increased BP -> increased impulses to cardiac center -> BP decrease.

Blood Volume Regulation

Hormones

  • Antidiuretic hormone (ADH).

  • Aldosterone.

  • Atrial natriuretic hormone.

  • Nitric oxide (NO).