Vascular systems in animals and plants

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Circulation in protozoans

the protozoans are heterotrophic cells that generally consume other cells or food particles; the word protozoa means "first animal"; with respect to the vascular system, the movement of gases and nutrients is accomplished by simple diffusion within the cell

Circulation in Cnidarians

hydras and other cnidarians have body walls that are two cells thick; all cells are in direct contact with either the internal or external environment so there is no need for a specialized circulatory system

Circulation in arthropods

have open circulatory systems in which blood (interstitial fluid) is in direct contact with the body tissues; the blood is circulated primarily by body movements; blood flows through a dorsal vessel and into spaces called sinuses where exchange occurs

Arthropod

a segmented ecdysozoan with a hard exoskeleton and joined appendages; familiar examples include insects, spiders, millipedes, and crabs

Interstitial fluid

(or tissue fluid) is a solution that bathes and surrounds the cells of multicellular animals. It is the main component of the extracellular fluid, which also includes plasma and transcellular fluid.

Circulation in annelids

the earthworm (annelida) uses a closed circulatory system to deliver materials to cell that are not in direct contact with the external environment; in a closed circulatory system, blood is confined to blood vessels; blood moves towards teh ehad in teh dorsal vessel, which functions as teh main heart by coordinated contractions; five pairs of vessels called aortic loops connect the dorsal vessel to the ventral vessel and function as additional pumps; earthworm blood lacks any red blood cells; a hemoglobin-like pigment is dissolved in teh aqueous solution

Closed circulatory system

a circulatory system in which blood is confined to vessels and is kept separate from teh interstitial fluid

Open circulatory system

a circulatory system in which fluid called hemolymph bathes the tissues and organs directly and there is no distinction between teh circulating fluid and the interstitial fluid

Circulation in humans

the human cardiovascular system is composed of a muscular, four-chambered heart, a network of blood vessels, and the blood itself; blood is pumped into the aorta, which branches into a series of arteries; the arteries branch into arterioles and then into microscopic capillaries; exchange of gases, nutrients, and cellular waste products occurs via diffusion across capillary walls; the capillaries then converge into venules and eventually into veins, leading deoxygenated blood back toward the heart

Single circulation

a circulatory system consisting of a single pump and circuit, in which blood passes from the sites of gas exchange to teh rest of the body before returning to the heart

Double circulation

a circulatory system consisting of separate pulmonary and systemic circuits, in which blood passes through the heart after completing each circuit

Systemic circuit

(throughout the body) the branch of the circulatory system that supplies all body organs except those involved in gas exchange

Pulmonary circuit

(toward the lungs) the branch of the ciruclatory system that supplies the lungs

Hemolymph

in invertebrates with an open circulatory system, teh body fluid that bathes tissues

Artery

a vessel that carries blood away from teh heart to organs throughout the body

Arteriole

a vessel that conveys blood between an artery and a capillary bed

Capillary

a microscopic blood vessel that penetrates the tissues and consists of a single layer of endothelial cells that allows exchange between the blood and interstitial fluid

Capillary bed

a net work of capillaries in a tissue or organ

Atrium

a chamber of the vertebrate heart that receives blood from the veins and transfers blood to a ventricle

Vein

in animals, a vessel taht carries blood toward teh heart; in plants, a vascular bundle in a leaf

Ventricle

a heart chamber that pumps blood out of a heart; the left ventricle is more muscular than the right ventricle because it is responsible for generating the force that propels the systemic circulation and because it pumps against a higher resistance

Venules

a vessel that conveys blood between a capillary bed and a vein

Mammalian circulation pt. 1

contraction of the right ventricle pumps blood to the lungs via the pulmonnary arteries; as the blood flows through the capillary beds in the left and right lungs, it loads O2 and unloads CO2; oxygen-rich blood returns from the lungs via the pulmonary veins to the left atrium of the heart; next, the oxygen-rich blood flows into the left ventricle, which pumps the oxygen-rich blood out to body tissues through the systemic circuit; blood leaves the left ventricle via the aorta, which conveys blood to arteries leading throughout the body; the first branches from teh aorta are the coronary arteries, which supply blood to the heart muscle itself; the branches lead to capillary beds in the head and arms; the aorta then descends into the abdomen, suplying oxygen-rich blood to arteries leading to capillary beds in the abdominal organs and legs (hind limbs); within the capillaries, there is a net diffusion of O2 from the blood to the tissues and of CO2 produced by cellular respiration into the blood

Mammalia circulation pt. 2

capillaries rejoin, forming venules, which convey blood to veins; oxygen-poor blood from the head, neck, and forelimbs is channeled into a large vein, the superior vena cava; anotehr large vein, the inferior vena cava, drains blood from the trunk and hind limbs; the two venae cavae empty their blood into the right atrium, from which the oxygen-poor blood flows into the right ventricle

Right side of the heart

pumps deoxygenated blood into pulmonary circulation (toward the lungs)

Left site of the heart

pumps oxygenated blood into systemic circulation (throughout the body)

Cardiac cycle

the alternating contractions and relaxations of the heart

Atrioventricular (AV) valve

a heart valve located between each atrium and ventricle that prevents a backflow of blood when the ventricle contracts

Semilunar valve

a valve located at each exit of the heart, where the aorta elaves the left ventricle and the pulmonary artery leaves teh right ventricle

Systole

the stage of the cardiac cycle in which a heart chamber contracts and pumps blood

Diastole

the stage of teh cardiac cycle in which a heart chamber is relaxed and fills with blood

Cardiac output

the volume of blood pumped per minute by each ventricle of the heart

Heart rate

the frequency of heart contraction

Stroke volume

the volume of blood pumped by a heart ventricle in a single contraction

Cardian cycle examined

for an adult human at rest with a heart rate of about 72 beats per minute, one complete cardiac cycle takes about 0.8 second; during a relaxation phase (atria and ventricle in diastole), blood returning from the large veins flows into the atria and ventricles through the atrioventricular valves; a brief period of atrial systole then forces all blood remaining in the atria into the ventricles; during the remainder of the cycle, ventricular systole pumps blood into the large arteries through the semilunar valves; note that during all but 0.1 seconds of the cardiac cycle, the atria are relaxed and aire filling up with blood returning from the veins

Contraction

the heart's pumping cycle is divided into two alternating phases, systole and diastole, which together makes up the heartbeat; systole is the period during which the ventricles contract; diastole is the period of cardiact muscle relaxation during which blood drains into all four chambers; cardiac output is defined as the total volume of blood the left ventricle pumps out per minute; cardiac output = heart rate (number of beats per minute) * stroke volume (volume of blood pumped out of the left ventricle per contraction)

Valves

the atrioventricular valves, located between the atria and ventricles on both sides of the heart, prevent backflow of blood into the atria; the valve on teh right side of the heart has three cusps and is called the tricuspid valve; the valve on teh left side has two cusps and is called the mitral valve; the semilunar valves have three cusps and are located between the left ventricle and teh aorta (the aortic valve) and between the right ventricle and the pulmonary artery (the pulmonic valve)

Sinoatrial (SA) node

a region in the right atrium of the heart that sets the rate and timing at which all cardiac muscle cells contract; the pacemaker

Atrioventricular (AV) node

a region of specialized heart muscle tissue between the left and right atria where electrical impulses are delayed for about 0.1 seconds before spreading to both ventricles and causing them to contract

Mechanism of contraction

cardiac muscle contracts rhythmically without stimulation from the nervous sytem, producing impulses that spread through its internal conducting system; an ordinary cardiac contraction originates in, and is regulated by, the sinoatrial (SA) node (the pacemaker), a small mass of specialized tissue located in the wall of the right atrium; the SA node spreads impulses through both atria, stimulating them to contract simultaneously; the impluse arrives at the atrioventricular (AV) node, which conducts slowly, allowing enough time for atrial contraction and for the ventricles to fill with blood; the impulse is then carried by the bundle of His (AV bundle), which branches into the right and left bundle branches, and through the Purkinje fibers in the walls of both ventricles, generating a strong contraction

Bundle of His

also known as the AV bundle or atrioventricular bundle, is a collection of heart muscle cells specialized for electrical conduction that transmits the electrical impulses from the AV node (located between the atria and the ventricles) to the point of the apex of the fascicular branches. The fascicular branches then lead to the Purkinje fibers which innervate the ventricles, causing the cardiac muscle of the ventricles to contract at a paced interval.

Purkinje fibers

(Purkyne tissue or Subendocardial branches) are located in the inner ventricular walls of the heart, just beneath the endocardium. These fibers are specialized myocardial fibers that conduct an electrical stimulus or impulse that enables the heart to contract in a coordinated fashion.

Control of contraction

the autonomic nervous system modifies the rate of heart contraction; the paraympathetic system innervates the heart via the vagus nerve and causes a decrease in heart rate; the sympathetic system innervates the heart via the cervical and upper thoracic ganglia and causes an incrases in the heart rate; the adrenal medulla exerts hormonal control via epinephrine (adrenaline) secretion, which causes an increase in heart rate

Blood vessels

the three types of blood vessels are arteries, veins, and capillaries; arteries are thick-walled, muscular, elastic vessels that transport oxygenated blood away from the heart...except for teh pulmonary arteries which transport deoxygenated blood from the heart to the lungs; veins are relatively thinly walled, inelastic vessels that conduct deoxygenated blood towards the heart....except for the pulmonary veins, which carry oxygenated blood from the lungs to the heart; much of the blood flow in veins depend on their compression by skeletal muscles during movement, rather than on the pumping of the heart; venous circulation is ofen at odds with gravity; thus larger veins, especially those in teh legs, have valves that prevent backflow; capillaries have very thin walls composed of a single layer of endothelial cells, across which respiratory gases, nutrients, enzymes, hormones, and wastes can readily diffuse; capillaries have the smallest diameter of all three types of vessels; red blood cells must ofen travel through them single file

Lymph vessels

the lymphatic system is a secondary circulatory system distinct from the cardiovascular circulation; its vessels transport excess interstitial fluid, called lymph, to the cardiovascular system, thereby keeping fluid levels in the body constant; lymph nodes are swellings along lymph vessels containing phagocytic cells (leukocytes) that filter the lymph, removing and destroying foreign particules and pathogens

Lymph

the colorless fluid, derived from instertitial fluid, in teh lymphatic system of vertebrates

Lymphatic system

a system of vessels and nodes, separate from the circulatory system, that returns fluid, proteins, and cells to the blood

Lymph node

an organ located along a lymph vessel; filter lymph and contain cells that attack viruses and bacteria

Blood

on the average, the human body contains four to six liters of blood; blood has both liquid (55%) and cellular components (45%); plasma is the liquid portion of the blood; it is an aqueous mixture of nutrients, salts, respiratory gases, wastes, hormones, and blood proteins (e.g. immunoglobulins, albumin, and fibrinogen); the cellular components of teh blood are erythrocytes, leukocytes and platelets

Plasma

the liquid matrix of blood in which the cells are suspended; contains water (solvent for carrying other substances), ions (osmotic balance, pH buffering, and regulation of membrane permeability), plasma proteins (osmotic balance, pH buffering, clotting, defense), and substances transported by blood (nutrients, waste products, respiratory gases, hormones)

Erythrocytes overview

(red blood cells, RBCs) are the oxygen-carrying components of blood; an erythrocyte contains approximately 250 million molecules of hemoglobin, each of which can bind up to four molecules of oxygen; when hemoglobin binds oxygen, it is called oxyhemoglobin; this is the primary form of oxygen transport in the blood; erythrocytes have a distinct biconcave, disklike shape, which gives them both increased surface area for gas exchange and greater flexibility for movement through those tiny capillaries; erythrocytes are formed from stem cells in the bone marrow where they lose their nuclei, mitochondria, and membranous organelles; once mature, RBCs circulate the blood for about 120 days, after which they are phagocytized by special cells in the spleen and liver

Erythrocyte

a blood cell that contains hemoglobin, which transports oxygen; also called a red blood cell

Hemoglobin

an iron-containing protein in red blood cells that reversibly bind oxygen

Lymphocyte

a type of white blood cell that mediates acquired immunity; the two main classes are B cells and T cells

Leukocytes overview

are larger than erythrocytes and serve protective functions; some white blood cells (WBCs) phagocytize foreign matter and organism such as bacteria; others migrate from teh blood to tissue, where they mature into stationary cells called macrophages; other WBCs, called lymphocytes, are involved in immune response and the production of antibodies (B cells) or cytolysis of infected cells (T cells)

Blood clotting

the clotting process begins when the endothelium of a vessel is damaged, exposing connective tissue in the vessel wall to blood; platelets adhere to collagen fibers in teh connective tissue and release a substance that makes nearby platelets sticky; the platelets form a plug that provides emergency protection against blood loss; this seal is reinforced by a clot of fibrin when vessel damage is severe; fibrin is formed via a multistep process: clotting factors released from the clumped platelets or damaged cells mix with clotting factors in teh plasma, forming an activation cascade that converts a plasma protein called prothrombin to its active form, thrombin; thrombin itself is an enzyme that catalyzes the final step of the clotting process, the conversion of fibrinogen to fibrin; the threads of fibrin become interwoven into a clot

Platelet

pinched-off cytoplasmic fragments of specialized bone marrow cells, have no nuclei, serve both structural and molecular functions in blood clotting

Fibrin

the activated form of teh blood-clotting protein fibrinogen; fibrin aggregates into threads that form the fabric of the clot

Leukocyte

a blood cell that functions in fighting infections; also called a white blood cell

Sickle-cell disease

a human genetic disease caused by a recessive allele that results in the substitution of a single amino acid in a globin polypeptide that is part of teh hemoglobin protein; characterized by deformed red blood cells (due to protein aggregation) that can lead to numerous symptoms

Fuctions of the circulatory system

blood transports nutrients and O2 to tissue and wastes and CO2 from tissue; platelets are involved in injury repair; leukocytes are teh main component of the immune system

Transport of gases

erythrocytes transport O2 throughout the circulatory system; actually, the hemoglobin molecules in erythrocytes bind to O2; each hemoglobin is capable of binding to four molecules of O2; hemoglobins also bind to CO2

Transport of nutrients and waste

amino acids and simple sugars are absorbed into the bloodstream at the intestinal capillaries and, after processing, are transported throughout the body; throughout the body, metabolic waste products (e.g. water, urea, and carbon dioxide) diffuse into capillaries from surrounding cells; these wastes are then delivered to teh appropriate excretory organs

Human immunity system

teh body has the ability to distinguish between "self" and "nonself" and to "remember" nonself entities (antigens) that it has previously encountered; these defense mechanisms are an integral part of the immune system; the immune system is composed of nonspecific and specific defense mechanisms; the specific immune system comprises humoral immunity, which involves the production of antibodies, and cell-mediated immunity, which involves cells that combat fungal and viral infection; lymphocytes are responsible for both of these immune mechanisms; the body also has a number of nonspecific defense mechanisms

Antigen

a macromolecule that elicits an immune response by binding to receptors of B cells or T cells

Skin and defense

skin is a physical barrier against bacterial invasion; in addition, pores on teh skin's surface secrete sweat, which contains an enzyme that attacks bacterial cell walls

Passages and defense

(e.g. the respiratory tract) are lined with ciliated mucous-coated epithelia, which filter and trap foreing particles

Macrophages

a phagocytotic cell present in many tissues that functions in innate immunity by destroying microbes and in acquired immunity as an antigen-presenting cell

Inflammatory response

is initiated by the body in response to physical damage; injured cells release histamine, which causes blood vessels to dilate, thereby incrasing blood flow to the damage region; granulocytes attracted to teh injury site phagocytize antigenic material; an inflammatory response is often accompanied by a fever

Interferons

proteins produced by cells under viral attack; they diffuse to other cells, where they help prevent the spread of the virus

Nonspecific defense mechanisms

the body uses a number of nonspecific defense mechanisms; skin, passages, macrophages, the inflammatory response, interferons; inappropriate response to certain foods and pollen can cause the body to form antibodies and release histamine; these response are called allergic reactions

Histamine

a substance released by mast cells that cause blood vessels to dilate and become more permeable in inflammatory and allergic responses

Antibody

a protein secreted by plasma cells (differentiated B cells) that binds to a partucular antigen; also called immunoglobulin; all antibody molecules have the same Y-shaped structure and in their monomer form consist of two identical heavy chains and two identical light chains

Mast cell

a vertebrate body cell that produces histamine and other molecules that trigger inflammation in response to infection and in allergic reactions

T cell

the class of lymphocytes that mature in the thymus and that includes both effector cells for the cell-mediated immune response and helper cells required for both branches of adaptive immunity

B cell

the lymphocytes that complete their development in the bone marrow and become effector cells for the humoral immune response

Humoral immune response

the branch of acquired immunity that involves the activation of B cells and that leads to teh production of antibodies, which defend against bacteria and viruses in body fluids

Cell-mediated immune response

the branch of acquired immunity that involves teh activation of cytotoxic T cells, which defend against infected cells

Humoral immunity

one of the body's defense mechanisms is the production of antibodies; these responses are very specific to teh antigen involved; humoral immunity is responsible for teh proliferation of antibodies after exposure to antigens; antibodies, also called immunoglobulins, are complex proteins that recognize and bind to specific antigens and trigger the immune system to remove them; antibodies eitehr attract other cells (such as leukocytes) to phagocytize the antigen or cause the antigen to clump together (allutinate) and form large insoluble complexes, facilitating their removal by phagocytic cells

Immunoglobulin

any of the class of proteins that function as antibodies; are divided into five major classes that differ in their distribution in the body and antigen disposal activities

Active immunity

refers to the production of antibodies during an immune response; can be conferred by vaccination; an individual is injected with a weakened, inactive, or related form of a particular antigen, which stimulates the immune system to produce specific antibodies against it; active immunity may require weeks to build up

Passive immunity

involves teh transfer of antibodies produced by another individual or organism; passive immunity is acquired either passively or by injection; for example, during pregnancy, some maternal antibodies cross the placenta and enter fetal circulation, conferring passive immunity upon teh fetus; although passive immunity is acuired immediately, it is very short-lived, lasting only as long as the antibodies circulate in the blood system; passive immunity is usually not very specific; gamma globulin, the fraction of blood containing a wide variety of antibodies, can be used to confer temporary protection against hepatitis and other diseases by passive immunity

Rejection of transplants

transplanted tissues or organs are detected as foreign bodies by the recipient's immune system; the resulting immune response can cause teh transplant to be rejected; immunosuppressing drugs can be used to lower the immune resonse to transplants and decrease the likelihood of rejection

ABO blood types

erythrocytes have characteristic cell-surface (antigens); antigens are macromolecules that are foreign to the host organism and trigger an immune response; the two major groups of red blood cell antigens are ABO group and teh Rh factor; type A blood has the A antigen present; it is extremely important during blood transfusions that donor and recipient blood types be appropriately matched; the aim is to avoid transfusion of red blood cells that will be clumped ("rejected") by antibodies (proteins in the immune system that bind specifically to antigens) present in teh recipient's plasma; the rule of blood is matching is as follows: if the donor's antigens are already in the recipient's blood, no clumping occurs; type AB blood is termed the "universal recipient", as it has neither anti-A nor anti-B antibodies; type O blood is considered to be the "universal donor"; it will not elicit a response from teh recipient's immune system because it does not possess any surface antigens

Rh factor

the Rh factor is another antigen that may be present on the surface of red blood cells; individuals may be RH+, possessing the Rh antigen, or RH-, lacking the Rh antigen; consideration of the Rh factor is particularly important during pregnancy; an Rh- woman can be sensitized by an Rh+ fetus if fetal red blood cells (which will have the Rh factor) enter maternal circulation during birth; if this woman subsequently carries another Rh+ fetus, the anti-Rh antibodies she produced when sensitized by the first birth may cross the placenta and destroy fetal red blood cells; this result in a severe anemia for the fetus, known as the erythroblastosis fetalis; erythroblastosis is not caused by ABO blood-type mismatches between mother and fetus because anti-A and anti-B cannot cross the placenta

Transport system in plants

transport system in plants must suply plant cells with nutrients and remove waste products; in plants, circulation is called translocation; the plant stem is the primary organ of transport in the plant; vascular bundles run up and down teh stem; the vascular bundle at the center of the stem contains sylem, phloem and cambium cells

Xylem

thick-walled, often hollow cells located on teh inside of teh vascular bundle (towards teh center of the stem); they carry water and minerals up the plant, and their thick walls give the plant its rigid support; older xylem cells die and form the heartwood used for lumber; the outer layer of xylem is alive and is called teh sapwood; two types of dylem cells ahve been differentiated: vessel cells and tracheids; the rise of water in teh xylem is explained by transpiration pull (as water evaporates from teh leaves of plants, a vacuum is created that pulls water up the stem), capillary action (any liquid in a thin tube will rise because of the surface tensionof teh liquid and interactions between the liquid and the tube), and root pressure (water entering the root hairs exerts a pressure that pushes water up teh stem)

Phloem

phloem cells are thin-walled cells on the outside of teh vascular bundle; they usually transport nutrients (especially carbohydrates produced in teh leaves) down the stem; the phloem cells are living and include sive tube cells and companion cells; if a tree is girdled by removing a strip of bark around the trunk, the phloem connections are severed and the tree will die

Cambium

(two layers thick) are the actively dividind, undifferentiated cells that give rise to xylem and phloem; they are found between the xylem and phloem cell layers; as they divide, the cells near the phloem differentiate into phloem cells, and the cells near the the xylem differentiate into xylem cells

Gas structure of a woody stem

proceeding from the outside inwards, teh following layers occur: epidermis (outer-bark), cortex, phloem, cambium, xylem, and pith (tissue involved in storage of nutrients and plant support); the phloem, cambium, and xylem layers are known as the fibrovascular bundle

Root

functions to absorb materials through the root hairs and anchor the plant; some roots provide storage for energy reserve (such as turnips and carrots); root haris are specialized cells of the root epidermis with thin-walled projections; they increase teh surface area for absoption of water and minerals from the soil; like the stem, the root has the following layers: epidermis, cortex, phloem, xylem, and cambium; the epidermis contains the root hair cells

Regions of growth in the plant

meristem refers to the actively dividing, undifferentiated cells of a plant; cambium, lying between teh phloem and xylem, is a type of meristem called lateral meristem; it provides for lateral growth of the stem by adding to the phloem or xylem (i.e., growth in diameter); apical meristem is also located at the tips of roots and stems where divisions lead to increase in lenght; after actively dividing, the new cells elongate (zone of elongation) and finally differentiate into one of the many specialized cells of the plants

Cortex

in plants, ground tissue that is between the vascular tissue and dermal tissue

Cortex

in plants, ground tissue that is between the vascular tissue and dermal tissue in a root or eudicot stem

Epidermis

the dermal tissue system of nonwoody plants, usually consisting of a single layer of tightly packed cells

Vascular tissue

plant tissue consisting of cells joined into tubes that transport water and nutrients throughout the plant body

Vascular tissue system

a transport system formed by xylem and phloem throughout a vascular plant; xylem transports water and minerals; phloem transports sugars, the product of photosynthesis

Vascular plant

a plant with vascular tissue; include all living plant species except mosses, liverworts and hornworts

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