Bio 2032: Human Anatomy - Blood Tissue

• Human Anatomy is Bio 2032.
• Contact Cristina V. Dieni, PhD at 942-421, ext 2248 or [email protected].

Blood Tissue Type

• Blood is a fluid connective tissue.
• Circulates through the cardiovascular system.

Blood Functions

• Transports dissolved gases, nutrients, and metabolic wastes.
• Delivers enzymes and hormones.
• Stabilizes pH and electrolyte composition.
• Prevents fluid losses through damaged vessels via clotting.
• Defends against toxins and pathogens using white blood cells and antibodies.
• Stabilizes body temperature by absorbing and redistributing heat.

Blood Cell Formation (Hemopoiesis)

• Blood cells form in red bone marrow.
• Hemopoiesis is the process where hematopoietic stem cells give rise to all blood cells.
• Pluripotential stem cells differentiate into two cell lines.
• Myeloid stem cells differentiate into erythrocytes, platelets, basophils, eosinophils, neutrophils, and monocytes.
• Lymphoid stem cells migrate to the thymus and differentiate into T cells.

Major Blood Components

• Plasma is a major blood component.
• Formed elements like erythrocytes (red blood cells), leukocytes (white blood cells), and platelets are major components.

Red Blood Cells (Erythrocytes)

• Red blood cells lack a nucleus and organelles.
• The lifespan of a red blood cell is about 120 days.
• Red blood cells are flexible, which allows them to travel through blood vessels easily.
• Red blood cells allow more room for hemoglobin.
• Without mitochondria, oxygen can be transported to tissues instead of being "used" by the mitochondria.

Blood Types & Rh Factor

• Red blood cells have surface antigens that determine blood type.
• Type A blood has RBCs with surface antigen A only.
• Type B blood has RBCs with surface antigen B only.
• Type AB blood has RBCs with both A and B surface antigens.
• Type O blood lacks both A and B surface antigens.
• Plasma contains antibodies that attack foreign surface antigens.
• Universal donors have type O blood.
• Universal recipients have type AB blood.

Granulocytes

• Neutrophils contain chemicals to kill bacteria.
• Eosinophils granules release chemicals that reduce inflammation.
• Basophils granules release histamine and heparin.
• Histamine dilates blood vessels.
• Heparin prevents abnormal blood clotting.

Agranulocytes

• Monocytes are large, phagocytic.
• Lymphocytes are responsible for specific immunity.
• T cells, B cells, and NK cells can differentiate.

Platelets

• Platelets derive from megakaryocytes.
• Megakaryocytes fragment into membrane-enclosed packets.
• Platelet thromboplastin factor is the main chemical.
• Thrombocytes were formerly called platelets.
• Platelets are involved in blood clotting (hemostasis).
• They release chemicals to initiate the clotting process.
• Platelets clump together to form a platelet plug.
• They contain actin and myosin which contract the clot.

Cardiovascular System: Heart Size and Chambers

• The heart is about the size of one's loosely clenched fist.
• The heart consists of four chambers: two atria and two ventricles.
• It pumps blood in two circuits: pulmonary and systemic.

Membranes

• Parietal membranes line cavity walls.
• Visceral membranes adhere to organ surfaces.

Pericardium

• The pericardial membrane forms two layers.
• Visceral pericardium (epicardium) adheres to the heart surface.
• The parietal pericardium consists of a fibrous outer layer called the pericardial sac and a serous pericardium that lines the inside.
• The serous pericardium produces a small amount of serous fluid.

Structure of the Heart Wall

• The heart wall consists of three layers.
• The epicardium (visceral pericardium) is the external surface.
• The myocardium consists of cardiac muscle.
• The endocardium is the internal surface and is continuous with the lining of blood vessels.

Heart Orientation

• The heart lies slightly to the left of midline in the mediastinum.
• The superior portion of the heart is the base.
• The apex is the inferior portion.
• The heart sits at an oblique angle.
• The right border is formed by the right atrium.
• The inferior border is formed by the right ventricle.
• The heart is rotated slightly toward the left.
• The sternocostal surface is formed by the right atrium and right ventricle.
• The posterior surface is formed by the left atrium.

Valves

• Atrioventricular valves bicuspid & tricuspid are open.
• Semilunar valves are pulmonary and aortic.

Blood Flow Through the Heart

• The right side of the heart is filled with deoxygenated blood.

Specialized Muscle Fibers in the Heart

• Major structures include the SA Node, AV Node, AV Bundle, Bundle Branches, and Purkinje Fibers.

Cardiac Cycle

• Step 1: SA node activity and atrial activation begin (Time = 0 msec).
• Step 2: Stimulus reaches the AV node (Elapsed time = 50 msec).
• Step 3: 100 msec delay at the AV node; atrial contraction begins (Elapsed time = 150 msec).
• Step 4: Impulse travels along the interventricular septum via the AV bundle and bundle branches to the Purkinje fibers (Elapsed time = 175 msec).
• Step 5: Impulse is distributed by Purkinje fibers throughout the ventricular myocardium; atrial contraction is completed, ventricular contraction begins (Elapsed time = 225 msec).
• Diastole records relaxation.
• Systole records contraction.
• The EKG (electrocardiogram) records electrical activity of heart

Cardiac Cycle Contraction and Relaxation

• The cardiac cycle has phases of contraction (systole) and relaxation (diastole).

Coronary Blood Vessels

• Coronary blood vessels supply blood to the heart muscles.
• They branch off the ascending aorta.
• Major coronary vessels include the Right coronary artery (RCA) and Left coronary artery (LCA).
• Cardiac veins drain into the coronary sinus.

Coronary Arteries

• Branches from the RCA: Marginal artery and the Posterior interventricular artery.
• Branches from the LCA: Anterior interventricular artery, Great Cardiac vein and Circumflex artery.

Cardiac Nerve Supply

• Parasympathetic vagus nerve.
• Sympathetic nerve.