Blood The only fluid tissue in the human

Blood • The only fluid tissue in the human body • Classified as a connective tissue • Components of blood • Living cells • Formed elements • Non-living matrix • Plasma

Blood • If blood is centrifuged • Erythrocytes sink to the bottom (45 percent of blood, a percentage known as the hematocrit) • Buffy coat contains leukocytes and platelets (less than 1 percent of blood) • Buffy coat is a thin, whitish layer between the erythrocytes and plasma • Plasma rises to the top (55 percent of blood)serum, that is used for blood chemistry

Figure 10. 1 (1 of 2)

Figure 10. 1 (2 of 2)

Physical Characteristics of Blood • Color range • Oxygen-rich blood is scarlet red • Oxygen-poor blood is dull red(cyanosis) • p. H must remain between 7. 35– 7. 45 • Blood temperature is slightly higher than body temperature at 100. 4°F • In a healthy man, blood volume is about 5– 6 liters or about 6 quarts • Blood makes up 8 percent of body weight

Blood Plasma • Acidosis • Blood becomes too acidic • Alkalosis • Blood becomes too basic • In each scenario, the(buffer systems): a. respiratory system(H 2 CO 3) b. kidneys(amonia) c. hemoglobin • Help restore blood p. H to normal

Formed Elements • Erythrocytes • Red blood cells (RBCs) • Leukocytes • White blood cells (WBCs) • Platelets(Thrombocytes) • Cell fragments

Formed Elements • Erythrocytes (red blood cells or RBCs) • Main function is to carry oxygen • Anatomy of circulating erythrocytes • Biconcave disks • Essentially bags of hemoglobin • Anucleate (no nucleus) • Contain very few organelles • 5 million RBCs per cubic millimeter of blood

Lymphocyte Erythrocytes Platelets Neutrophils Figure 10. 2

Formed Elements • Hemoglobin • Iron-containing protein • Binds strongly, but reversibly, to oxygen • Each hemoglobin molecule has four oxygen binding sites • Each erythrocyte has 250 million hemoglobin molecules • Normal blood contains 12– 18 g of hemoglobin per 100 m. L blood, less than 10 g is anaemia

Formed Elements • Homeostatic imbalance of RBCs • Anaemia is a decrease in the oxygencarrying ability of the blood& not decrease # of RBC • Iron deficiency anaemia • Sickle cell anaemia (SCA) results from abnormally shaped heamoglobine, comes in crisis in young black children on eating fava beans • Polycythemia is an excessive or abnormal increase in the number of erythrocytes

Figure 10. 3

Formed Elements • Polcythemia • Disorder resulting from excessive or abnormal increase of RBC • May be caused by bone marrow cancer (polycythemia vera) • May be a response to life at higher altitudes (secondary polycythemia) • Increased RBC slows blood flow and increases blood viscosity , lead to thrombosis

Formed Elements • Leukocytes (white blood cells or WBCs) • Crucial in the body’s defense against disease • These are complete cells, with a nucleus and organelles(segmented nucleus) • Able to move into and out of blood vessels (diapedesis) • Can move by ameboid motion • Can respond to chemicals released by damaged tissues • 5, 000 to 11, 000 WBC per cubic millimeter of blood

Formed Elements • Abnormal numbers of leukocytes • Leukocytosis • WBC count above 11, 000 leukocytes/mm 3 • Generally indicates an infection • Leukopenia • Abnormally low leukocyte level • Commonly caused by certain drugs such as corticosteroids and anticancer agents • Leukemia • Bone marrow becomes cancerous, turns out excess WBC, over 200, 000, immature WBC, s

Formed Elements • Types of leukocytes • Granules in their cytoplasm can be stained • Possess lobed nuclei • Include neutrophils, eosinophils, and basophils • Agranulocytes • Lack visible cytoplasmic granules • Nuclei are spherical, oval, or kidney-shaped • Include lymphocytes and monocytes

Formed Elements • List of the WBCs from most to least abundant • Neutrophils • Lymphocytes • Monocytes • Eosinophils • Basophils • Easy way to remember this list • Never • Let • Monkeys • Eat • Bananas

Figure 10. 4

Formed Elements • Types of granulocytes • Neutrophils • Cytoplasm stains pale pink and contains fine granules • Deep purple nucleus contains three to seven lobes • Function : phagocytosis at active sites of infection • Numbers increase during acute infections • 3, 000– 7, 000 neutrophils in a cubic millimeter of blood (40– 70% of WBCs)

Formed Elements • Types of granulocytes (continued) • Eosinophils • Red, coarse cytoplasmic granules • Figure-8 or bilobed nucleus stains blue-red • Function to kill parasitic worms and play a role in allergy attacks • 100– 400 eosinophils in a cubic millimeter of blood (1– 4% of WBCs)

Formed Elements • Types of granulocytes (continued) • Basophils • Sparse but large blue-purple granules • U- or S-shaped nucleus stains dark blue • Release histamine (vasodilator) at sites of inflammation, increasd in allergic conditions • Contain heparin (anticoagulant) • 20– 50 basophils in a cubic millimeter of blood (0– 1% of WBCs)

Formed Elements • Types of agranulocytes • Lymphocytes • Dark purple-blue nucleus • Functions as part of the immune response • B lymphocytes produce antibodies • T lymphocytes are involved in graft rejection, fighting tumors and viruses • 1, 500– 3, 000 lymphocytes in a cubic millimeter of blood (20– 45% of WBCs)

Formed Elements • Types of agranulocytes (continued) • Monocytes • Largest of the white blood cells • Gray-blue cytoplasm • Dark blue-purple nucleus is often kidney shaped • Function as macrophages • Important in fighting chronic infection • 100– 700 monocytes per cubic millimeter of blood (4– 8% of WBCs)

Formed Elements • Platelets • Needed for the clotting process, by activating 12 clotting factors contained inside • Platelet count ranges from 150, 000 to 400, 000 per cubic millimeter of blood • 300, 000 is considered a normal number of platelets per cubic millimeter of blood

Hematopoiesis • Blood cell formation • Occurs in red bone marrow • All blood cells are derived from a common stem cell (hemocytoblast) • Hemocytoblast differentiation • Lymphoid stem cell produces lymphocytes • Myeloid stem cell produces all other formed elements

Figure 10. 4

Formation of Erythrocytes • Unable to divide • Wear out in 100 to 120 days • When worn out, RBCs are eliminated by phagocytes in the spleen or liver • Lost cells are replaced by division of hemocytoblasts in the red bone marrow

Control of Erythrocyte Production • Rate is controlled by a hormone (erythropoietin) • Kidneys produce most erythropoietin as a response to reduced oxygen levels in the blood, that will stim. red bone marrow

Formation of White Blood Cells and Platelets • Controlled by hormones • Colony stimulating factors (CSFs) and interleukins prompt bone marrow to generate leukocytes • Thrombopoietin stimulates production of platelets

Hemostasis • Stoppage of bleeding resulting from a break in a blood vessel • Hemostasis involves three phases • Vascular spasms • Platelet plug formation • Coagulation (blood clotting) • Clotting time 2 -4 minutes

Undesirable Clotting • Thrombus • A clot in an unbroken blood vessel • Can be deadly in areas like the heart &deep veins of leg • Embolus • A thrombus that breaks away and floats freely in the bloodstream • Can later clog vessels in critical areas such as the brain, heart &lung

Bleeding Disorders • Thrombocytopenia • Platelet deficiency • Even minor truma can cause bleeding from small blood vessels that require platelets for clotting • Hemophilia • Hereditary bleeding disorder • Normal clotting factors are missing

Blood Groups and Transfusions • Large losses of blood have serious consequences • Loss of 15 to 30 percent causes weakness • Loss of over 30 percent causes shock, which can be fatal • Transfusions are the only way to replace blood quickly • Transfused blood must be of the same blood group

ABO Blood Groups • The presence of both antigens A and B is called type AB • The presence of antigen A is called type A • The presence of antigen B is called type B • The lack of both antigens A and B is called type O

ABO Blood Groups Blood Group RBC Antigens Plasma antibodies Blood that can be received AB A, B None A, B, AB, O Universal recipient B B Anti-A B, O A A Anti-B A, O O None Anti-A, Anti-B O Universal donor

Rh Blood Groups • Named because of the presence or absence of Rh antigens (agglutinogen D) that was originally defined in Rhesus monkeys • Most Americans are Rh+ (Rh positive) • Problems can occur in mixing Rh+ blood into a body with Rh– (Rh negative) blood

Rh Dangers During Pregnancy • Danger occurs only when the mother is Rh– and the father is Rh+, and the child inherits the Rh+ factor • Rho. GAM shot can prevent buildup of anti-Rh+ antibodies in mother’s blood

Rh Dangers During Pregnancy • The mismatch of an Rh– mother carrying an Rh+ baby can cause problems for the unborn child • The first pregnancy usually proceeds without problems • The immune system is sensitized after the first pregnancy • In a second pregnancy, the mother’s immune system produces antibodies to attack the Rh+ blood (hemolytic disease of the newborn)

Blood typing can be done by adding anti A or anti B • Coagulation or no coagulation leads to determining blood type • Typing for ABO and Rh factors is done in the same manner • Cross matching—testing for agglutination of donor RBCs by the recipient’s serum, and vice versa. A

Blood being tested Serum Anti-B Anti-A Type AB (contains antigens A and B; agglutinates with both sera) Agglutinated RBCs Type B (contains antigen B; agglutinates with anti-B serum) Type A (contains antigen A; agglutinates with anti-A serum) Type O (contains no antigens; does not agglutinate with either serum) Figure 10. 8

The heart & blood vessels • The heart pumps blood • Blood vessels allow blood to circulate to all parts of the body • The functions of the cardiovascular system • To deliver oxygen and nutrients to cells and tissues • To remove carbon dioxide and other waste products from cells and tissues

The Heart • Location • Thorax between the lungs in the inferior mediastinum • Orientation • Pointed apex directed toward left hip • Base points toward right shoulder • About the size of your fist

Midsternal line 2 nd rib Sternum Diaphragm Point of maximal intensity (PMI) (a) Figure 11. 1 a

Superior vena cava Pulmonary trunk Diaphragm Aorta Parietal pleura (cut) Left lung Pericardium (cut) Apex of heart (c) Figure 11. 1 c

Brachiocephalic trunk Left common carotid artery Superior vena cava Left subclavian artery y Right pulmonary artery Aortic arch Ascending aorta Ligamentum arteriosum Left pulmonary artery Pulmonary trunk Left pulmonary veins Right pulmonary veins Left atrium Right coronary artery in coronary sulcus (right atrioventricular groove) Anterior cardiac vein Right ventricle Marginal artery Small cardiac vein Inferior vena cava (a) Auricle of left atrium Circumflex artery Left coronary artery in coronary sulcus (left atrioventricular groove) Left ventricle Great cardiac vein Anterior interventricular artery (in anterior interventricular sulcus) Apex Figure 11. 3 a

The Heart: Coverings • Pericardium—a double-walled composed of two layers • Visceral pericardium • Next to heart; also known as the epicardium • Parietal pericardium • Outside layer that lines chest cavity from inside • Serous fluid fills the space between the layers of pericardium

Pulmonary trunk Pericardium Myocardium Fibrous pericardium Parietal layer of serous pericardium Pericardial cavity Epicardium (visceral layer of serous Heart pericardium) wall Heart wall Myocardium Endocardium Heart chamber Figure 11. 2

The Heart: Heart Wall • Three layers • Epicardium • Outside layer • This layer is the visceral pericardium • Connective tissue layer • Myocardium • Middle layer • Mostly cardiac muscle • Endocardium • Inner layer • Endothelium

Superior vena cava Aorta Left pulmonary artery Right pulmonary artery Left atrium Right atrium Left pulmonary veins Right pulmonary veins Pulmonary semilunar valve Fossa ovalis Right atrioventricular valve (tricuspid valve) Right ventricle Chordae tendineae Inferior vena cava Left atrioventricular valve (bicuspid valve) Aortic semilunar valve Left ventricle Interventricular septum Myocardium Visceral pericardium (b) Frontal section showing interior chambers and valves. Figure 11. 3 b

The Heart: Chambers • Right and left side act as separate pumps • Four chambers • Atria • Receiving chambers • Right atrium • Left atrium • Ventricles • Discharging chambers • Right ventricle • Left ventricle

The Heart: Septa • Interventricular septum • Separates the two ventricles • Interatrial septum • Separates the two atria

The Heart’s Role in Blood Circulation • 1. Systemic circulation • Blood flows from the left side of the heart through the body tissues and back to the right side of the heart • 2. Pulmonary circulation • Blood flows from the right side of the heart to the lungs and back to the left side of the heart

Capillary beds of lungs where gas exchange occurs Pulmonary Circuit Pulmonary arteries Pulmonary veins Aorta and branches Venae cavae Left atrium Left ventricle Right atrium Heart Right ventricle Systemic Circuit KEY: Oxygen-rich, CO 2 -poor blood Oxygen-poor, CO 2 -rich blood Capillary beds of all body tissues where gas exchange occurs Figure 11. 4

The Heart: Valves • Allow blood to flow in only one direction to prevent backflow • Four valves • Atrioventricular (AV) valves—between atria and ventricles • Bicuspid (mitral) valve (left side of heart) • Tricuspid valve (right side of heart) • Semilunar valves—between ventricle and artery • Pulmonary semilunar valve • Aortic semilunar valve

The Heart: Valves • AV valves • Anchored in place by chordae tendineae attached to papillary muscles • Open during heart relaxation and closed during ventricular contraction • Semilunar valves • Closed during heart relaxation but open during ventricular contraction • Heart Sounds are due closure of: AV valves, in first sound & semiular valves in second sound.

Coronary Circulation • The heart has its own nourishing circulatory system consisting of • Coronary arteries—branch from the aorta to supply the heart muscle with oxygenated blood • Cardiac veins—drain the myocardium of blood • Coronary sinus—a large vein on the posterior of the heart, receives blood from cardiac veins & empties into the right atrium.

Brachiocephalic trunk Left common carotid artery Superior vena cava Left subclavian artery Right pulmonary artery Aortic arch Ascending aorta Ligamentum arteriosum Left pulmonary artery Pulmonary trunk Left pulmonary veins Right pulmonary veins Left atrium Right coronary artery in coronary sulcus (right atrioventricular groove) Anterior cardiac vein Right ventricle Marginal artery Small cardiac vein Inferior vena cava (a) Auricle of left atrium Circumflex artery Left coronary artery in coronary sulcus (left atrioventricular groove) Left ventricle Great cardiac vein Anterior interventricular artery (in anterior interventricular sulcus) Apex Figure 11. 3 a

The Heart: Associated Great Vessels • Arteries • Aorta • Leaves left ventricle • Pulmonary arteries • Leave right ventricle

The Heart: Associated Great Vessels • Veins • Superior and inferior venae cavae • Enter right atrium • Pulmonary veins (four) • Enter left atrium

The Heart: Conduction System • Special tissue sets the pace • Sinoatrial node = SA node (“pacemaker”), is in the right atrium • Atrioventricular node = AV node, is at the junction of the atria and ventricles • Atrioventricular bundle = AV bundle (bundle of His), is in the interventricular septum • Bundle branches are in the interventricular septum • Purkinje fibers spread within the ventricle wall muscles

Superior vena cava Sinoatrial (SA) node (pacemaker) Left atrium Atrioventricular (AV) node Right atrium Bundle branches Atrioventricular (AV) bundle (bundle of His) Purkinje fibers Interventricular septum Figure 11. 7

Heart Contractions • Once SA node starts the heartbeat • Impulse spreads to the AV node • Then the atria contract • At the AV node, the impulse passes through the AV bundle, bundle branches, and Purkinje fibers, then ventricles contract • Blood is ejected from the ventricles to the aorta and pulmonary trunk as the ventricles contract

Heart Contractions • Homeostatic imbalance • Heart block—damaged AV node releases them from control of the SA node; result is in a slower heart rate as ventricles contract at their own rate • Arrythemias are disturbance in heart rhythm • Fibrillation—a rapid, uncoordinated shuddering of the heart muscle, it may be atrial (150 b/m) or ventricular(250 b/m)or more , is fatal

Heart Contractions • Homeostatic imbalance (continued) • Tachycardia—rapid heart rate over 100 beats per minute • Bradycardia—slow heart rate less than 60 beats per minutes

The Heart: Cardiac Cycle & Heart Sounds • Atria contract simultaneously • Atria relax, then ventricles contract • Systole = contraction • Diastole = relaxation

The Heart: Cardiac Output • Cardiac output (CO) • Amount of blood pumped by each side (ventricle) of the heart in one minute • Stroke volume (SV) • Volume of blood pumped by each ventricle in one contraction (each heartbeat) • Usually remains relatively constant • About 70 m. L of blood is pumped out of the left ventricle with each heartbeat • Heart rate (HR) • Typically 75 beats per minute

The Heart: Regulation of Heart Rate • Increased heart rate • Sympathetic nervous system • Crisis • Low blood pressure, shock. • Hormones • Epinephrine • Thyroxine • Exercise • Decreased blood volume, in sever bleeding, shock may result

The Heart: Regulation of Heart Rate • Decreased heart rate • Parasympathetic nervous system • High blood pressure or blood volume • Decreased venous return

Blood Vessels: The Vascular System • Transport blood to the tissues and back • Carry blood away from the heart • Arteries • Arterioles • Exchanges between tissues and blood • Capillary beds • Return blood toward the heart • Venules • Veins

(a) Artery Vein Figure 11. 10 a

Blood Vessels: Microscopic Anatomy • Three layers (tunics) • Tunic intima • Endothelium • Tunic media • Smooth muscle • Controlled by sympathetic nervous system • Tunic externa • Mostly fibrous connective tissue

Valve Tunica intima • Endothelium • Loose connective tissue Internal elastic lamina Tunica media • Smooth muscle • Elastic fibers External elastic lamina Tunica externa • Collagen fibers Lumen Artery Venule Arteriole Capillary network Lumen Vein Basement membrane Endothelial cells (b) Capillary Figure 11. 10 b

Structural Differences Among Blood Vessels • Arteries have a thicker tunica media than veins • Capillaries are only one cell layer (tunica intima) to allow for exchanges between blood and tissue • Veins have a thinner tunica media than arteries • Veins also have valves to prevent backflow of blood • Lumen of veins are larger than arteries

Venous Aids for the Return of Blood to the Heart • Veins: • Have a thinner tunica media • Operate under low pressure • Have a larger lumen than arteries • To assist in the movement of blood back to the heart: • Larger veins have valves to prevent backflow • Skeletal muscle “milks” blood in veins toward the heart, as in calf muscles.

Valve (open) Contracted skeletal muscle Valve (closed) Vein Direction of blood flow Figure 11. 11

Capillary Beds • Capillary beds consist of two types of vessels • Vascular shunt—vessel directly connecting an arteriole to a venule • True capillaries—exchange vessels • Oxygen and nutrients cross to cells • Carbon dioxide and metabolic waste products cross into blood

Vascular shunt Precapillary sphincters True capillaries Terminal arteriole Postcapillary venule (a) Sphincters open; blood flows through true capillaries. Figure 11. 12 a

Figure 11. 12 b

Major Arteries of System Circulation • Aorta • Largest artery in the body • Leaves from the left ventricle of the heart • Regions • Ascending aorta—leaves the left ventricle • Aortic arch—arches to the left • Thoracic aorta—travels downward through the thorax • Abdominal aorta—passes through the diaphragm into the abdominopelvic cavity

Major Arteries of System Circulation • Arterial branches of the ascending aorta • Right and left coronary arteries serve the heart

Major Arteries of Systemic Circulation • Arterial branches of the aortia arch (BCS) • Brachiocephalic trunk splits into the • Right common carotid artery • Right subclavian artery • Left common carotid artery splits into the • Left internal and external carotid arteries • Left subclavian artery branches into the • Vertebral artery • In the axilla, the subclavian artery becomes the axillary artery brachial artery radial and ulnar arteries

Major Veins of Systemic Circulation • Superior and inferior vena cava enter the right atrium of the heart • Superior vena cava drains the head and arms • Inferior vena cava drains the lower body

3. Fetal Circulation • Fetus receives exchanges of gases, nutrients, and wastes through the placenta • Umbilical cord contains three vessels • Umbilical vein—carries blood rich in nutrients and oxygen to the fetus • Umbilical arteries (2)—carry carbon dioxide and debris-laden blood from fetus to placenta

Superior vena cava Ductus arteriosus Pulmonary artery Pulmonary veins Foramen ovale Inferior vena cava Hepatic vein Ductus venosus Inferior vena cava Hepatic portal vein Umbilical vein Fetal umbilicus Umbilical cord Umbilical arteries KEY: High oxygenation Moderate oxygenation Low oxygenation Very low oxygenation Aorta Common iliac artery External iliac artery Internal iliac artery Urinary bladder Placenta Figure 11. 16

Fetal Circulation • Blood flow bypasses the liver through the ductus venosus and enters the inferior vena cava right atrium of heart • Blood flow bypasses the lungs • Blood entering right atrium is shunted directly into the left atrium through the foramen ovale • Ductus arteriosus connects the aorta and pulmonary trunk (becomes ligamentum arteriosum at birth)

4. Hepatic Portal Circulation 4. • Veins of hepatic portal circulation drain • Digestive organs • Spleen • Pancreas • Portal vein carries this blood to the liver • Liver helps maintain proper glucose, fat, and protein concentrations in blood, & remove toxins from blood.

Hepatic Portal Circulation • Major vessels of hepatic portal circulation • Inferior and superior mesenteric veins(small & large intestine) • Splenic vein(spleen) • Left gastric vein(stomach) • Then blood returns to IVC via hepatic vein.

Inferior vena cava (not part of hepatic portal system) Gastric veins Liver Spleen Stomach Hepatic portal vein Splenic vein Inferior mesenteric vein Superior mesenteric vein Small intestine Large intestine Figure 11. 18

Pulse • Pressure wave of blood • Monitored at “pressure points” in arteries where pulse is easily palpated • Pulse averages 70 to 76 beats per minute at rest

Superficial temporal artery Facial artery Common carotid artery Brachial artery Radial artery Femoral artery Popliteal artery Posterior tibial artery Dorsalis pedis artery Figure 11. 19

Blood Pressure • Measurements by health professionals are made on the pressure in large arteries • Systolic—pressure at the peak of ventricular contraction • Diastolic—pressure when ventricles relax • Write systolic pressure first and diastolic last (120/80 mm Hg) • Pressure in blood vessels decreases as distance from the heart increases

Variations in Blood Pressure • Normal human range is variable • Normal • 140 to 110 mm Hg systolic • 80 to 75 mm Hg diastolic • Hypotension • Low systolic (below 110 mm Hg) • Often associated with illness • Hypertension • High systolic (above 140 mm Hg) • Can be dangerous if it is chronic

The Lymphatic System • Consists of two semi-independent parts • Lymphatic vessels • Lymphoid tissues and organs • Lymphatic system functions • Transports escaped fluids back to the blood • Plays essential roles in body defense and resistance to disease

Lymphatic Characteristics • Lymph—excess tissue fluid carried by lymphatic vessels • Properties of lymphatic vessels • One way system toward the heart • No pump • Lymph moves toward the heart • Milking action of skeletal muscle • Rhythmic contraction of smooth muscle in vessel walls

Lymphatic Vessels • Lymph capillaries • Fluid leaks into lymph capillaries • Fluid is forced along the vessel

Tissue fluid Tissue cell Lymphatic capillary Blood capillaries Arteriole Venule (a) Figure 12. 2 a

Lymphatic Vessels • Lymphatic collecting vessels • Collect lymph from lymph capillaries • Carry lymph to and away from lymph nodes • Return fluid to circulatory veins near the heart • Right lymphatic duct • Thoracic duct

Regional lymph nodes: Entrance of right lymphatic duct into right subclavian vein Cervical nodes Axillary nodes Internal jugular vein Thoracic duct entry into left subclavian vein Thoracic duct Aorta Spleen Inguinal nodes Cisterna chyli (receives lymph drainage from digestive organs) Lymphatics KEY: Drained by the right lymphatic duct Drained by the thoracic duct Figure 12. 3

Lymph • Harmful materials that enter lymph vessels • Bacteria • Viruses • Cancer cells • Cell debris

Lymph Nodes • Filter lymph before it is returned to the blood • Defense cells within lymph nodes • Macrophages—engulf and destroy foreign substances • Lymphocytes—provide immune response to antigens

Lymph Node Structure • Most are kidney-shaped and less than 1 inch long • Cortex • Outer part • Contains follicles—collections of lymphocytes(white pulps) • Medulla • Inner part(red Pulps) • Contains phagocytic macrophages

Afferent lymphatic vessels Germinal center in follicle Capsule Subcapsular sinus Trabecula Afferent lymphatic vessels Cortex Follicle Efferent lymphatic vessels Hilum Medullary sinus Medullary cord Figure 12. 4

Flow of Lymph Through Nodes • Lymph enters the convex side through afferent lymphatic vessels(5 -7) • Lymph flows through a number of sinuses inside the node • Lymph exits through efferent lymphatic vessels(1 -2) • Fewer efferent than afferent vessels causes flow to be slowed

Other Lymphoid Organs • Several other organs contribute to lymphatic function • Spleen • Thymus • Tonsils • Peyer’s patches

Tonsils (in pharyngeal region) Thymus (in thorax; most active during youth) Spleen (curves around left side of stomach) Peyer’s patches (in intestine) Appendix Figure 12. 5

Spleen • Located on the left side of the abdomen • Filters blood • Destroys worn out blood cells • Forms blood cells in the foetus • Acts as a blood reservoir • Has structure similar to lymph nodes

Thymus Gland • Located low in the throat, overlying the heart • Functions at peak levels only during childhood • Produces hormones (like thymosin) to program lymphocytes(T cells)

Tonsils • Small masses of lymphoid tissue around the pharynx • Trap and remove bacteria and other foreign materials • Tonsillitis is caused by congestion with bacteria • Palatine, pharyngeal(adenoids), lingual & tubal

Peyer’s Patches • Found in the wall of the small intestine • Resemble tonsils in structure • Capture and destroy bacteria in the intestine

Body Defenses • The body is constantly in contact with bacteria, fungi, and viruses • The body has two defense systems foreign materials • Innate (nonspecific) defense system • Adaptive (specific) defense system • Immunity—specific resistance to disease

Figure 12. 6

1. Innate (Nonspecific) Body Defences • Innate body defenses are mechanical barriers to pathogens such as • Body surface coverings • Intact skin • Mucous membranes • Specialized human cells • Chemicals produced by the body

Surface Membrane Barriers: A)First Line of Defence • Skin and mucous membranes • Physical barrier to foreign materials • Also provide protective secretions • p. H of the skin is acidic to inhibit bacterial growth • Sebum is toxic to bacteria • Vaginal secretions are very acidic

Surface Membrane Barriers: First Line of Defense • Stomach mucosa • Secretes hydrochloric acid • Has protein-digesting enzymes • Saliva and lacrimal fluid contain lysozymes, an enzyme that destroy bacteria • Mucus traps microogranisms in digestive and respiratory pathways

Innate (Nonspecific) Defense System Cells and Chemicals: B)Second Line of Defense • a. Natural killer cells • b. Inflammatory response • c. Phagocytes • d. Antimicrobial proteins • e. Fever

Innate (Nonspecific) Defense System Cells and Chemicals: Second Line of Defense • a. Natural killer (NK) cells • Can lyse (disintegrate or dissolve) and kill cancer cells • Can destroy virus-infected cells& bacteria.

Innate (Nonspecific) Defense System Cells and Chemicals: Second Line of Defense • b. Inflammatory response • Triggered when body tissues are injured • Four most common S&S of acute inflammation • Redness • Hotness • Terndenss • Edema

Innate (Nonspecific) Defense System Cells and Chemicals: Second Line of Defense • Functions of the inflammatory response • Prevents spread of damaging agents • Disposes of cell debris and pathogens through phagocytosis • Sets the stage for repair

Innate (Nonspecific) Defense System Cells and Chemicals: Second Line of Defense • Process of the inflammatory response: • Neutrophils migrate to the area of inflammation by rolling along the vessel wall • They squeeze through the capillary walls by diapedesis to sites of inflammation • Neutrophils gather in the site of tissue injury (positive chemotaxis) and consume any foreign material present.

Innate (Nonspecific) Defense System Cells and Chemicals: Second Line of Defense • c. Phagocytes • Cells such as neutrophils and macrophages • Engulf foreign material into a vacuole • Enzymes from lysosomes digest the material

Innate (Nonspecific) Defense System Cells and Chemicals: Second Line of Defense • Phagocytosis • Neutrophils move by diapedesis to clean up damaged tissue and/or pathogens • Monocytes become macrophages and complete disposal of cell debris

Figure 12. 9 a

1 Phagocyte adheres to pathogens. Phagosome (phagocytic vesicle) Lysosome Acid hydrolase enzymes (b) Events of phagocytosis 2 Phagocyte engulfs the particles, forming a phagosome. 3 Lysosome fuses with the phagocytic vesicle, forming a phagolysosome. 4 Lysosomal enzymes digest the pathogens or debris, leaving a residual body. 5 Exocytosis of the vesicle removes indigestible and residual material. Figure 12. 9 b

Cells and Chemicals: Second Line of Defense • d. Antimicrobial proteins • Attack microorganisms • Hinder reproduction of microorganisms • Most important • Complement proteins • Interferon, used now in treatment of Hip. B

Cells and Chemicals: Second Line of Defense • Complement proteins • A group of at least 20 plasma proteins • Activated when they encounter and attach to cells (complement fixation) • Damage foreign cell surfaces • Release vasodilators and chemotaxis chemicals, cause opsonization

Membrane attack complex forming Antibodies attached to pathogen’s membrane Pore Activated complement proteins attach to pathogen’s membrane in step-by-step sequence, forming a membrane attack complex (a MAC attack). MAC pores in the membrane lead to fluid flows that cause cell lysis. Figure 12. 10

Cells and Chemicals: Second Line of Defense • Interferon • Proteins secreted by virus-infected cells • Bind to healthy cell surfaces to interfere with the ability of viruses to multiply

Cells and Chemicals: Second Line of Defense • e. Fever • Abnormally high body temperature • Hypothalamus heat regulation can be reset by pyrogens (secreted by white blood cells) • High temperatures inhibit the release of iron and zinc from the liver and spleen needed by bacteria • Fever also increases the speed of tissue repair, through vasodilation

Adaptive Defence System : C. Third Line of Defence • Immune response is the immune system’s response to a threat • Immunology is the study of immunity • Antibodies are proteins that protect from pathogens

Adaptive Defense System: Third Line of Defense • Types of Immunity • Humoral immunity = antibody-mediated immunity • Provided by antibodies present in body fluids, made by B lymphocytes • Cellular immunity = cell-mediated immunity • Targets virus-infected cells, cancer cells, and cells of foreign grafts • Made by T lymphocytes

Adaptive Defense System: Third Line of Defense • Antigens • Any substance capable of exciting the immune system and provoking an immune response • Examples of common antigens • Foreign proteins (strongest) • Nucleic acids • Large carbohydrates • Some lipids • Pollen grains • Microorganisms

Humoral Immune Response • Most B cells become plasma cells • Produce antibodies to destroy antigens • Activity lasts for 4 or 5 days • Some B cells become long-lived memory cells (secondary humoral response)

Humoral Immune Response • Memory B- cells are long-lived • A second exposure causes a rapid response • The secondary response is stronger and longer lasting

Primary Response (initial encounter with antigen) Activated B cells Proliferation to form a clone Plasma cells Antigen binding to a receptor on a specific B cell (B cells with non-complementary receptors remain inactive) Memory B cell Secreted antibody molecules Secondary Response (can be years later) Clone of cells identical to ancestral cells Subsequent challenge by same antigen results in more rapid response Plasma cells Secreted antibody molecules Memory B cells Figure 12. 12

Relative antibody concentration in blood plasma Secondary response Primary response 0 1 2 3 4 5 6 Time (weeks) Antigen injected Figure 12. 13

Active Immunity • Occurs when B cells encounter antigens and produce antibodies • Active immunity can be • Naturally acquired during bacterial and viral infections as in measles & chicken pox • Artificially acquired from vaccines as in flue shots by injecting weak bact. Or virus

Passive Immunity • Occurs when antibodies are obtained from someone else • Conferred naturally from a mother to her featus (naturally acquired) • Conferred artificially from immune serum or gamma globulin (artificially acquired)as antetanic serum. ”

e. g. Measles & Chicken Pox e. g. Flu Shot Inherited Immunity e. g. Antetetanic Serum, Anti. Snake Venom Figure 12. 14

Antibodies (Immunoglobulins or Igs) • Soluble proteins secreted by B cells (plasma cells) • Carried in blood plasma • Capable of binding specifically to an antigen

Figure 12. 15 a

Antibodies • Antibody classes • Antibodies of each class have slightly different roles • Five major immunoglobulin classes (MADGE) • Ig. M—can fix complement • Ig. A—found mainly in mucus • Ig. D—important in activation of B cell • Ig. G—can cross the placental barrier and fix complement • Ig. E—involved in allergies

Antibodies • Antibody function • Antibodies inactivate antigens in a number of ways • Complement fixation • Neutralization • Agglutination • Precipitation

Figure 12. 16

Cellular (Cell-Mediated) Immune Response • Antigens must be presented by macrophages to an immunocompetent T cell (antigen presentation) • T cells must recognize the antigen • After antigen binding, clones form as with B cells, but different classes of cells are produced: helper, memory & killer T cells

Antigen “Presented” antigen T cell antigen receptor Helper T cell Dendritic cell Antigen processing Selfprotein Cytokines Cytotoxic (killer) T cell Cell-mediated immunity (attack on infected cells) B cell Humoral immunity (secretion of antibodies by plasma cells) Cytokines Figure 12. 17

Cellular (Cell-Mediated) Immune Response • T cell clones 1. Cytotoxic (killer) T cells • Specialize in killing infected cells • Insert a toxic chemical (perforin) 2. Helper T cells • Help other cells( B & T cells) to fight the invaders • 3. memory T cells

Figure 12. 19

Organ Transplants and Rejection • Major types of grafts • Autografts—tissue transplanted from one site to another on the same person • Isografts—tissue grafts from an identical person (identical twin) • Allografts—tissue taken from an unrelated person , same species • Xenografts—tissue taken from a different animal species

Organ Transplants and Rejection • Autografts and isografts are ideal donors • Xenografts are never successful • Allografts are more successful with a closer tissue match

Disorders of Immunity: Allergies (Hypersensitivity) • Abnormal, vigorous immune responses • Types of allergies • 1. Immediate hypersensitivity • Triggered by release of histamine from Ig. E binding to mast cells • Reactions begin within seconds of contact with allergen • E. g. Anaphylactic shock—dangerous, systemic response, as bee stings , penicillin allergy

Disorders of Immunity: Allergies (Hypersensitivity) • Types of allergies (continued) • 2. Type II: Cytotoxic Hypersensitivity • Triggered by the release of lymphokines from activated helper T cells • Symptoms usually appear 1– 3 days after contact with antigen • Ig. M/Ig. G, are responsible • E. g. drug induced hemolytic anemia, granulocytopenia, thrombocytopenia

Disorders of Immunity: Allergies (Hypersensitivity) • 3. Type III : Immune complex hypersensitivity • Ig. G/Ig. M • E. g. : Systemic Lupus Erythematosus, Lupus Nephritis • Type IV : Cell Mediated/Delayed type hypersensitivity • Ig. A • E. g. : TB, Leprosy, Blastomycosis, toxoplasmosis, histoplasmosis

Disorders of Immunity: Immunodeficiencies • Production of immune cells is abnormal • May be congenital or acquired • Includes AIDS (Acquired Immune Deficiency Syndrome)

Disorders of Immunity: Autoimmune Diseases • The immune system does not distinguish between self and nonself • The body produces antibodies and sensitized T lymphocytes that attack its own tissues

Disorders of Immunity: Autoimmune Diseases • Examples of autoimmune diseases • Multiple sclerosis—white matter of brain and spinal cord are destroyed • Myasthenia gravis—impairs communication between nerves and skeletal muscles • Type I diabetes mellitus—destroys pancreatic beta cells that produce insulin

Disorders of Immunity: Autoimmune Diseases • Examples of autoimmune diseases • Rheumatoid arthritis—destroys joints • Systemic lupus erythematosus (SLE) • Affects kidney, heart, lung, and skin • Glomerulonephritis—impairment of renal function