1. Transport and Circulatory Systems

2. Why are transport and circulation different ?
Transport is the movement of one molecule from one place to another.
Circulation is the continous flow of the materials.
Why do we need?
Transport and circulation are necessary for the movement of molecules that cells need for metabolism and the molecules that are formed as a result of metabolism. Also they may help regulation of body temperature and hormonal control.

3. Simple organisms
Unicellular and simple organisms exchange materials by osmosis, diffusion and active transport .

4. Transport in plants
Primitive plants like liverworts, mosses don’t have transport systems. Ferns have primitive vascular tissues. In higher plants transport occurs in two ways. Water and minerals are taken by roots and transported to the stem and leaves by xylem. But organic molecules like glucose are transported from leaves to the roots and from roots to the leaves by phloem.
Also stomata are important for the gas exchange and for transpiration.

5. Monocotyledones
Have closed vascular bundles. There is no cambium. Vascular bundles are scattered in the stem.

6. Dicotyledones They have open vascular bundles.
Have cambium between xylem and phloem.
Vascular bundles are arranged in a circle.

7. LEAF ADAPTATIONS
Leaves are the organs where photosynthesis, transpiration and gas exchange occur. Palisade paranchyma is the most important part in the photosynthesis.
Stomata are the place where gas exchange occurs ( CO2 intake- O2 release in photosynthesis, O2 consumption - CO2 release in cellular respiration)
Epidermal cells secrete waxy substance called cuticle to prevent water loss.

8. Structure of the stoma
A pair of specialized epidermal cells, called guard cells, controls the opening and closing of each stoma. When the stomata are open, CO2 can enter the leaf by diffusion—but water vapor is lost in the same way. The inner side of the guard cell wall is thicker than the outer part. This structural detail enables the openning and closing of the stoma.
Although stoma cells are epidermis, they are the only epidermal cells with chloroplasts. When cells do photosynthesis , glucose level increases. Increase in the Glucose level increases the osmotic pressure of the cell, this causes the cell to take in water. Due to the unequal thickening of the cell wall, cell swells and stomatal openning enlarges.

9. If the stoma cells lose water ( glucose is converted to starch, water amount is increased, osmotic pressure is decreased), stomatal openning gets smaller.
K+ concentration in the guard cells also controls the openning of the stoma. The increase in the concentration of K+, increases the osmotic pressure of the cells.

10. FACTORS EFFECTING THE OPENNING OF STOMA
Light: Light causes the stomata of most plants to open, admitting CO2 for photosynthesis.
Amount of CO2: A low level favors opening of the stomata, thus allowing the uptake of more CO2. When CO2 is low the pH is basic, this encourages the conversion of starch to glucose. When glucose is high, stoma opens.
Water stress is a common problem for plants, especially on hot, sunny, windy days. Plants have a protective response to these conditions, which uses the water potential of the mesophyll cells as a cue. Even when the CO2 level is low and the sun is shining, if the mesophyll is too dehydrated— plant closes the stomata and prevent further drying of the leaf. This response reduces the rate of photosynthesis, but it protects the plant.
Temperature: Plants close the stomata above 30 C.
Wind: wind sweeps away the water vapor around the leaf and increases the transpiration.
Humidity: If there are enough water available, stomata open but transpiration is low at humid air.

11. Transpiration
Transpiration is the diffusion of the water vapor through the stomata. Transpiration:
Increases the pulling force of the leaves on the water. In that way more minerals can be taken with more water.
Increases the resistance of plant to drought.
Encourages the excretion of excess water.
Plants are adapted for different conditions.
Plants in dry conditions
Plants in humid conditions
Leaf Surface area
narrow
Large
Stomata number
Few (embedded in deep)
More (on the surface)
Cuticle
thick
thin
Leaves
With hair
Without hair
Veins
few
more
Roots
ın deep layers
on the surface

12. Water transport Water transport consists of 2 processes:
Absorption of water from roots(root pressure)
Transport of water in xylem (in vessels and tracheids)
Within living tissues, the movement of water from cell to cell follows a gradient of water potential(osmotic pressure). Over longer distances, in xylem vessels and phloem sieve tubes, the flow of water and dissolved solutes is driven by a gradient of concentration. (bulk flow)

13. ABSORPTION OF WATER
Water moves into a root because the root has a higher osmotic pressure than does the soil solution. Water moves from the cortex of the root into the stele (which is where the vascular tissues are located) because the stele has a more osmotic pressure than does the cortex.
The basis for root pressure is a higher solute concentration, and accordingly a more osmotic pressure in the xylem sap than in the soil solution.

14. There is good evidence that root pressure is important and can be observed in the phenomenon of guttation, in which liquid water is forced out through openings at the margins of leaves. Guttation occurs only under conditions of high atmospheric humidity and plentiful water in the soil, which occur most commonly at night.

15. Transport of water in xylem
The key elements of water transport in the xylem are 1. Transpiration, the evaporation of water from the leaves 2. Tension in the xylem sap resulting from transpiration 3. Cohesion in the xylem sap from the leaves to the roots

16. The concentration of water vapor in the atmosphere is lower than that in the leaf. Because of this difference, water vapor diffuses from the intercellular spaces of the leaf, through openings called stomata, to the outside air. This process is called transpiration
The force generated by the evaporation of water from the mesophyll cell walls creates a tension that draws more water into the cell walls, replacing that which was lost. The removal of water from the mesophyll and veins, establishes tension on the entire column of water within the xylem, so that the column is drawn upward all the way from the roots.

17. The ability of water to be pulled upward through tiny tubes results from the cohesion of water—the tendency of water molecules to stick to one another through hydrogen bonding. The narrower the tube, the greater the tension the water column can withstand without breaking. The integrity of the column is also maintained by the adhesion of water to the xylem walls.
Adhesion: sticking together to the different molecules
Cohesion: sticking together to the same molecules

18. This transpiration-cohesion-tension mechanism requires no work (that is, no expenditure of energy) on the part of the plant. (don’t forget that xylem cells are nonliving). At each step between soil and atmosphere, water moves passively toward a region with a more negative water potential(high osmotic pressure).
In addition to promoting the transport of minerals, transpiration contributes to temperature regulation.

19. TRANSPORT OF ORGANIC MOLECULES (glucose, amino acids) IN PHLOEM
Substances in the phloem move from sources to sinks. The flow can be in two directions. A source is an organ (such as a mature leaf or a storage root) that produces (by photosynthesis or by digestion of stored reserves) more sugars than it requires. A sink is an organ (such as a root, a flower, a developing fruit or tuber, or an imma­ture leaf) that consumes sugars for its own growth and storage needs.
Sugars (primarily sucrose), amino acids, some minerals, and a variety of other solutes are translocated between sources and sinks in the phloem. This translocation requires energy.

20. Translocation occurs by pressure flow
Translocation occurs by pressure flow. According to the pressure flow model of translocation in the phloem, sucrose is actively transported into sieve tube elements at a source, giving those cells a greater sucrose concentration than the surrounding cells. Water therefore enters the sieve tube elements by osmosis. The entry of this water causes a greater pressure potential at the source end of the sieve tube, so that the entire fluid content of the sieve tube is pushed toward the sink end of the tube— in other words, the sap moves by bulk flow in response to a pressure gradient. In the sink, the sucrose is unloaded by active transport.

21. http://www.whfreeman.com/thelifewire6e/con_index.htm?35 animasyon

22. specific sugars and amino acids are actively transported into cells of the phloem. In sink regions, the solutes are actively transported out of the sieve tube elements and into the surrounding tissues.

23. CIRCULATORY SYSTEM IN ANIMALS
The purpose of the circulatory system in animals:
Transport of food monomers and gases to the body cells.
Transport of unnecessary metabolites
Regulation of body temperature
Transport of hormones and homeostasis.

24. Open circulatory system Closed circulatory system
1. No capillaries and veins
1. Capillaries and veins are found.
2. Heart/s and artery can be found.
3. Tissue fluid(blood-endolymph) travels out of the bood vessels and mixes with the body fluid.
3. Blood never travels aout of the blood vessels.
4. In molluscs, arthropoda, insects.
4. Annelid(earthworm), cephalopods, all vertebrates.

25. ADVANTAGES OF CLOSED CIRCULATORY SYSTEM
Blood can flow more rapidly through vessels than through intercellular spaces, and can therefore transport nutrients and wastes to and from tissues more rapidly.
By changing resistance in the vessels, closed systems can be more selective in directing blood to specific tissues.
Specialized cells and large molecules that aid in the transport of hormones and nutrients can be kept within the vessels, but can drop their cargo in the tissues where it is needed.
Overall, closed circulatory systems can support higher levels of metabolic activity than open systems can, especially in larger animals. How, then, do highly active insect species achieve high levels of metabolic output with their open circulatory systems? One way is by not depending on their circulatory systems for respiratory gas exchange

26. A circulatory system is unnecessary if the cells of an organism are close enough to the external environment that nutrients, respiratory gases, and wastes can diffuse between the cells and the environment. Small aquatic invertebrates have struc­tures and body shapes that permit direct exchanges between cells and environment. Many of these animals have flattened body shapes that maximize the amount of surface area that is in contact with the external environment .

27. Large surface areas and branched internal cavities cannot satisfy the needs of larger animals with many layers of cells. The cells of such animals are surrounded by an internal environment of extracellular fluids, tissue fluids.

28. Insects have open circulatory system
Insects have open circulatory system. The contractions of the heart propel the tissue fluid through vessels(small artery) leading to different regions of the body, but the fluid leaves those vessels to move through the tissues and eventually return to the heart. The fluid returns to the heart through valved openings called ostia. In these organisms tissue fluid(blood-endolymph) only carries nutrients. Respiratory gases are carried by tracheal tubes.

29. One large blood vessel on the ventral side of the earthworm carries blood from its anterior end to its posterior end. Smaller vessels branch off and transport the blood to even smaller vessels . In the capillaries respiratory gases(mostly around skin), nutrients, and metabolic wastes diffuse between the blood and the tissue fluid. The blood then flows from these vessels into larger vessels that lead into one large vessel on the dorsal side of the worm. The dorsal vessel carries the blood from the posterior to the anterior end of the body.
Five pairs of vessels connect the large dorsal and ventral vessels in the anterior end, thus completing the circuit. The dorsal vessel and the five connecting vessels serve as hearts for the earthworm; their contractions keep the blood circulating. The direction of circulation is determined by one­way valves in the dorsal and connecting vessels.

30. Circulatory system in fish
The fish heart has two chambers. An atrium receives blood from the body(deoxygenated) and pumps it into a more muscular chamber, the ventricle. The ventricle pumps the blood to the gills, where gases are exchanged. Blood leaving the gills (oxygenated)collects in a large dorsal artery, the aorta, which distributes blood to smaller arteries and arterioles leading to all the organs and tissues of the body. In the tissues, blood flows through beds of tiny capillaries, collects in venules and veins, and eventually returns to the atrium of the heart.

31. Circulatory system in amphibia
Pulmonary and systemic circulation are partly separated in adult amphibians. A single ventricle pumps blood to the lungs and to the rest of the body. Two atria receive blood returning to the heart. One receives oxygenated blood from the lungs, and the other receives deoxygenated blood from the body. Because both atria deliver blood to the same ventricle, the oxygenated and deoxygenated blood could mix, so that blood going to the tissues would not carry a full load of oxygen.
These animals supply their oxygen need also by their skin.

32. Turtles, snakes, and lizards are commonly said to have three-chambered hearts, while crocodilians (crocodiles and alligators) are said to have four-chambered hearts. But this statement is an oversimplification. The hearts of all these animals have two separate atria and a ventricle that is divided in a complex way so that mixing of oxygenated and deoxygenated blood is minimized.
Amphibians and reptiles can not keep constant their body temperature. They are called as poikilothermic animals.

33. The four-chambered hearts of birds and mammals completely separate their pulmonary and systemic circuits. They kepp their body temp. Constant. They are called as homeothermic animals.
poikilothermic
homeothermic
Metabolic rate
Env. Temp.
homeothermic
poikilothermic
Env. Temp.
Body temperature

34. Human circulatory system
Heart always have deoxygenated blood in the right, oxygenated blood in the left side.Deoxgenated blood from the body comes first to the right atrium by veins. Blood then flows to the right ventricle through the tricuspid valve. This valve prevents backflow of the blood rom ventricle to the atrium. Right ventricle pumps the deoxygenated blood to the lung by pulmonary artery. Arteries always carry blood from the ventricles. The right heart pumps blood through the pulmonary circuit. The oxygenated blood from the lung returns back to the left atrium of the heart. The vein who carries the oxygenated blood from the lung to the heart is called as pulmonary vein.
The oxygenated blood in the left atrium then flows to the left ventricle through mitral(bicuspid) valve. Then the oxygenated blood is pumped rom the left ventricule to the aorta. The left heart pumps blood through the systemic circuit. Also the arteries coming out of the heart has valves at the beginning part. This valve helps the one directional flow of the blood.

35. Heart is composed of 3 layers
Heart is composed of 3 layers. The inner layer is endocard, it is a very thin layer which covers the inner surface of the heart. It contains epithelial cells and connective tissue. Myocard: is composed of cardiac muscle. It contains coronery blood vessels. Pericard: is the outermost layer of the heart. It covers heart as an envelope. It contains fluid inside this envelope. This layer reduces friction during contractions.

36. Pulmonary and systemic circulation
Pulmonary circulation is between the heart and the lungs. Deoxygenated blood is pumped out of the right ventricle through the pulmonary artery to the lungs and in the lung capillaries gas exchange occurs. After oxygenated blood is collected by pulmonary vein, it returns back to the left atrium.
Systemic circulation is between heart and the body organs. Blood is pumped out of the left ventricle through the aorta to the body organ arteries. Material(gas, nutrients) exchange occurs in the capillaries and blood is collected back by veins to the vena cava and flows to the right atrium.

37. Mechanism of heart contraction
The contraction of the two atria, followed by the contraction of the two ventricles and then relaxation, is called the cardiac cycle. Contraction of the ventricles is called ventricular systole, and relaxation of the ventricles called ventricular diastole.
Cardiac muscle has specific properties. First, cardiac muscle cells are in electrical contact with one another through gap junctions, which enable action potentials to spread rapidly from cell to cell. This coordinated contraction is essential for pumping blood effectively.
Second, some cardiac muscle cells are pacemaker cells. These cells have the ability to initiate action potentials without stimulation from the nervous system.(but speed of contraction can be controlled by sympathic and parasympathic nerves)The primary pacemaker of the heart is a nodule of modified cardiac muscle cells, the sinoatrial node, located at the junction of the superior vena cava and right atrium.

38. A normal heartbeat begins with an action potential in the sinoatrial node. This action potential spreads rapidly throughout the electrically coupled cells of the atria, causing them to contract. Situated at the junction of the atria and the ventricles is a nodule of modified cardiac muscle cells called the atrioventricular node, which is stimulated by the depolarization of the atria. With a slight delay, it generates action potentials that are conducted to the ventricles by bundle of His. The short delay in the spread of the action potential imposed by the atrioventricular node ensures that the atria contract before the ventricles do, so that the blood passes progressively from the atria to the ventricles to the arteries.

39. Arteries
Veins
Capillaries
Takes away the blood from the heart
Brings the blood to the heart
Material exchange occurs between blood and body cells
Large arteries have many collagen, elastic fibers and smooth muscle, which enable them to withstand the high pressures of blood flowing rapidly from the heart
Vein walls are not thick and elastic as arteries. Thier diameter is large.
Capillary wall is very thin consists of 1 layer of epithelial cells. It is semipermeable.
Blood moves by the pressure created by the beating of the heart
Blood pressure is the lowest in veins
Blood pressure is low
Blood pressure drops as it travels away from the heart.
Valves within veins and venules prevent backflow
Found between arterioles and venules.
Blood flow speed is high.
Blood flow speed is low
Blood flow speed is the lowest in the capillaries.
Contraction of skeletal muscles and absorption force of heart help blood movement in the vein

40. Factors helping the movement of blood in the arteries and arterioles.
Pressure formed by the contraction of ventricles.
Contraction of smooth muscle cells in the wall of arteries.
Pressure gradient
Pushing force of the blood
Factors helping the movement of blood in the veins and venules
One way valves
Contraction of the skeletal muscles around them
Pressure changes in the chest
Gravity *pressure gradient
Absorption force formed by the diastole of the atrium

43. Blood pressure
Blood exerts a pressure to the walls of the blood vessels. This pressure is formed by the systole of the ventricles. Blood pressure decreases as blood travels away from the heart. Blood pressure increases during systole, decreases during diastole.

44. Velocity of the blood
Velocity of the blood is affected from the diameter of the blood vessels and the blood pressure. The velocity of the fluid decreases as it passes from a narrow tube to a wide tube. The velocity is high in arteries but it decreases as arteries branch into many arterioles. The total cross-sectional area of the arterioles is bigger than the AORTA, so the velocity is low in arterioles and in capillaries.

45. Material exchange between blood and body cells
Starling suggested that water balance in capillary beds is a result of two opposing forces, which have come to be known as Starling’s forces. One force is blood pressure, which squeezes water and small solutes out of the capillaries, and the other is osmotic pressure created by the large protein molecules that cannot leave the capillaries. Starling called this second force colloidal osmotic pressure. He hypothesized that blood pressure is high at the arterial end of a capillary bed and drops steadily as blood flows to the venous end.

46. The colloidal osmotic pressure, however, is constant along the capillary. As long as the blood pressure is above the osmotic pressure, water leaves the capillary, but when blood pressure falls below the osmotic pressure, water returns to the capillary. The actual numbers for a normal capillary bed in a resting person suggest that there would be a slight net loss of water to the intercellular spaces.
Basınç
Kan basıncı
Ozmotik basınç
Doku sıvısı
Atardamar kılcalı
Toplardamar kılcalı

47. Blood and blood clotting
Functions of the blood:
Transport: brings glucose, aa, vitamin, mineral and oxygen to the cells. Takes away the formed CO2, urea and excess water.
Transport of hormones: Carries hormones to target organs.
Regulation: in homeostasis within the body. Regulation of pH, water, temperature.
Immunity: White blood cells and antibodies fight against the diseases.
Coagulation: helps to keep the blood in the vessels during an injury. )fibrinogen)
Keep the osmotic pressure of the blood constant by blood proteins like albumen, globulin.

48. Blood proteins are formed in the liver.
Red blood cells are made in the red bone marrow in spongy bones. Red blood cells don’t have nucleus, mitochondria. They live for 120 days.Old red blood cells are broken down in liver and the heme(ıron) molecules are used again in the production of RBC. The unnecessary hemes are converted into bilirubin and passes to the bile and thrown out by feces.

49. plasma
Plasma is the liquid part of the blood which has clotting proteins. But serum doesn’t have clotting proteins.
Plasma contains important proteins. Blood clotting proteins, antibody proteins, albumin proteins for osmotic pressure.

50. Blood clotting
Megakaryocytes are large cells that remain in the bone mar­row and continually break off cell fragments called platelets. A platelet is just a tiny fragment of a cell without cell organelles and function in clotting.
Blood clotting factors participate in a cascade of chemical reactions that activate other substances circulating in the blood. The cascade begins with cell damage and platelet activation and leads to the conversion of an inactive circulating enzyme, prothrombin, to its active form, thrombin. Thrombin causes molecules of a plasma protein called fibrinogen to polymer fibrin.
When thrombocytes react with O2, they form an enzyme thrombokinase. This enzyme changes Prothrombin into thrombin in the presence of Ca. Thrombin converts fibrinogen into fibrin. And fibrin fixes the injury.

52. Lymphatic circulation
Lymphatic circulation consists of lymph capillaries, lymph vesses and lymph nodules. It is a separate system of vessels—the lymphatic system—which returns tissue fluid to the blood.

53. Functions of the Lymphatic system
Functions in material exchange. Collects extra fluid.
Absorbs triglycerides(fatty acids and glycerols) .
The lymph nodes also act as filters. Particles become trapped there and are digested by phagocytes in the nodes.
Lymph nodes are a major site of lymphocyte production and of the phagocytic action that removes microorganisms and other foreign materials from the circulation

54. After entering the lymphatic vessels, the tissue fluid is called lymph
After entering the lymphatic vessels, the tissue fluid is called lymph. Fine lymphatic capillaries merge progressively into larger and larger vessels and end in two lymphatic vessels—the thoracic ducts—that empty into large veins at the base of the neck . The left thoracic duct carries most of the lymph from the lower part of the body and is much larger than the right thoracic duct. Thoracic duct mixes with blood circulation from the left subclavian vein.
Lymph, like blood, is propelled toward the heart by skeletal muscle contractions and breathing movements, and lymphatic vessels, like veins, have one-way valves that keep the lymph flowing toward the thoracic duct.

55. Emilen maddelerin izlediği yol Glikoz- aa yağ ve ADEK
Lenf damarı
Peke sarnıcı
Sol Köprücük altı toplar damarı
Üst ana toplar damar
Sağ kulakçık
İnce bağırsak toplar damarı
Kapı toplar damarı
Karaciğer
Karaciğer toplar damarı
Alt ana toplar damar
Sağ kulakçık

56. Immune system
Thymus, bone marrow, spleen, and lymph nodes, are essential parts of the defense system.
Spleen : filters blood, produces lymphocytes and monocytes. Destroy old erythrocytes.
lymph nodes : filter blood, holds microbes
tonsillite: produces lymphocytes.
Bone marrow: Produces blood cells, do phagocytosis, produces antibodies.
Thymus: activates lymphocytes.

57. Defense types
Nonspecific defenses, or innate defenses, are inherited mechanisms that protect the body from many pathogens. These can be chemical or cellular. An example is the skin
Specific defenses are adaptive mechanisms aimed at a specific target. The recognition and destruction of specific nonself substances is an important function of an animal’s immune system.
The humoral immune response, which produces antibodies,
the cellular immune response, which destroys infected cells.

59. In the humoral immune response (from the Latin humor, “fluid”), antibodies react with antigenic determinants on pathogens in blood, lymph, and tissue fluids.
Some antibodies are soluble and travel free in the blood and lymph; others exist as integral membrane proteins on B cells. The first time a specific antigen invades the body, it may be detected and bound by a B cell whose membrane antibody recognizes one of its antigenic determinants. This binding activates the B cell, which makes multiple soluble copies of an antibody with the same specificity as its membrane antibody.

61. The cellular immune response is carried out by T cells within the lymph nodes, the bloodstream, and the intercellular spaces. These cells have integral membrane proteins— T cell receptors—that recognize and bind to antigenic determinants. Once a T cell is bound to an antigenic determinant, it initiates an immune response that typically results in the total destruction of a nonself or altered self cell.

64. The first time a vertebrate animal is exposed to a particular antigen, there is a time lag (usually several days) before the number of antibody molecules and T cells slowly increases But for years afterward—sometimes for life—the immune system “remembers” that particular antigen. The secondary immune response is characterized by a shorter lag time, a greater rate of antibody production, and a larger production of total antibody or T cells than the primary response.

66. Antibodies
Antibodies are proteins called immunoglobulins. There are several types of immunoglobulins, but all contain a tetramer consisting of four polypeptide chains. In each immunoglobulin molecule, two of these polypeptides are identical light chains, and two are identical heavy chains. Disulfide bonds hold the chains together. Each polypeptide chain consists of a constant region and a variable region.

67. interferon: virüs bir canlıya girdiğinde , canlı interferon üretir ve canlıyı korur. İnterferon hücrelere bağlanarak özel enzimler üretmelerine sebep olur, bu enzimler virüs için gerekli proteinlerin yapımına engel olur.
İltihaplanma:zararı maddeler sonucu ortaya çıkan bir dizi olaydır. İltihaplanma sırasında histamin salınır ve bu madde yaralı bölgeye kan akışını hızlandırır. Kılcaldan doku sıvısına geçiş artar. Akyuvarlar bu bölgeye gelerek yabancı maddeleri fagositozla yok etmeye çalışırlar. Bu durum yaralı bölgede şiş ve kızarıklık oluşturur. Bölgede irin oluşması ise akyuvar ölüleri ve mikrop kalıntılarını içerir.

68. http://highered. mcgraw-hill
immune

69. Spesifik bağışıklık
Vücuda giren moleküller algılanarak planlı bir engelleme ise spesifik bağışıklıkla olur. Vücuda giren yabancı maddelerin(antijen) yok edilebilmesi için antikor denilen özel bir madde üretilir.
Antikor: Bu maddeler protein yapıdadır.
Değişken kısımları vardır bu bölgelerden molekülleri(antijen) tanırlar ve onlara bağlanarak onları etkisiz hale getirirler.
Antijen vücuda girdikten sonra antikorun kanda görülmesi 1 hafta süre alabilir. İkinci defa aynı antijen ile karşılaşırsa daha hızlı antikor üretilir.

70. Birinci tepki
İkinci tepki
hafta
Antikor yoğunluğu

71. Salgısal-Humoral bağışıklık
B lenfositleri tarafından oluşturulur. İnsanda barsakta lenfoid doku B lenfositlerinin olgunlaştığı yerdir.
B lenfositleri antijenle karşılaştıklarında hemen bölünürler ve plazma hücresini oluştururular. Plazma hücreleri antijene göre antikor üretmeye başlarlar. Antikorlar antijenleri etkisiz hale getirir.Bu işlem kanda veya lenfte gerçekleşir.
Bazı B hücreleri hafız hücreleri olurlar ve aynı antijen vücuda girdiğinde daha hızlı olarak cevap yaratırlar.

73. Hücresel bağışıklık:
Timüste olgunlaşan T lenfositleri görev yaparlar. Bu hücreler doğrudan antijenle savaşırlar. Antijen makrofaj tarafından tutulur. Bilgi yardımcı T hücresine aktarılır. Yardımcı T hücresi aktifleşir ve bölünür. Yardımcı T hücreleri Humoral bağışıklığı da tetiklerler. Mikropların fagositozu hızlanır.

74. AŞILAR
Aşıda amaç denetimli bir enfeksiyon yaratarak mikrobun organizma tarafından tanınmasını sağlamaktır. Aşı aktif bağışıklık sağlar etkisi uzun sürelidir.
Serum aşılarda ise hazır antikorlar bulunmaktadır