Human Circulatory System Quiz

Circulatory System Disorders

• The circulatory system comprises the cardiovascular and lymphatic systems. This section focuses on blood vessels, blood, and related disorders.
• Arteries carry blood away from the heart. Veins return blood to the heart. Capillaries facilitate microcirculation within tissues for gas, nutrient, and waste exchange. Systemic circulation involves tissue exchange, while pulmonary circulation handles gas exchange in the lungs.
• Arteries and veins have distinct histological layers: tunica intima (innermost endothelium), tunica media (smooth muscle-rich middle layer), and tunica adventitia (outer connective tissue).

Blood Composition and Function

• Blood functions in oxygen and nutrient delivery, waste removal, immune defense, and maintaining homeostasis.
• Blood plasma, a liquid component, contains proteins. Blood cells include erythrocytes (red blood cells), leukocytes (white blood cells), and thrombocytes (platelets).

Erythrocytes (Red Blood Cells)

• Mature red blood cells are biconcave discs without a nucleus, containing hemoglobin (globin and heme).
• Their lifespan is approximately 120 days. Erythropoietin, produced in the kidneys, regulates red blood cell production.

Blood Clotting (Hemostasis)

• Hemostasis involves three phases: vascular spasm, platelet plug formation, and coagulation.
• This process results in a fibrin mesh trapping cells, ultimately forming a blood clot. Plasmin eventually breaks down the clot.

Blood Typing

• Blood typing relies on antigens on red blood cell membranes.
• The ABO system categorizes blood based on the presence or absence of A and B antigens. Corresponding antibodies exist in the plasma.
• The Rh system classifies blood based on the presence (Rh+) or absence (Rh-) of the D antigen.

Diagnostic Tests

• Complete Blood Count (CBC) measures red blood cells, white blood cells, and platelets. Leukocytosis indicates inflammation/infection, while leukopenia suggests viral infections or treatments like chemotherapy, radiation.
• Morphology studies cell shape and size. Hematocrit measures packed cell volume, while hemoglobin assesses hemoglobin content. Mean corpuscular volume (MCV) reflects oxygen-carrying capacity.
• Reticulocyte count evaluates bone marrow function. Chemical analyses determine serum levels of components like iron, B12, folic acid, cholesterol, urea, and glucose. Bleeding time measures platelet function. Prothrombin time (PT), partial thromboplastin time (PTT), and the International Normalized Ratio (INR) assess coagulation factors and their function.

Blood Therapies

• Whole blood, packed red blood cells, and packed platelets treat anemia and thrombocytopenia.
• Plasma or colloids maintain blood volume. Artificial blood products, while functional, do not replicate all normal blood functions.
• Epoetin alpha, a synthetic erythropoietin, aids in treating certain types of anemia and before some surgical procedures.

Anemias

• Anemia reduces oxygen transport capacity, leading to decreased energy production, impaired cellular metabolism, and compensation mechanisms like tachycardia.
• Clinical signs include fatigue, pallor, dyspnea, and tachycardia. Epithelial cell regeneration issues can lead to inflammation, stomatitis, cracked lips, and dysphagia. Severe anemia can cause angina or congestive heart failure.

Iron Deficiency Anemia

• Insufficient iron hinders hemoglobin production, resulting in microcytic, hypochromic red blood cells.
• Dietary iron deficiency, chronic blood loss, impaired duodenal absorption, and severe liver damage can cause iron deficiency.

Pernicious Anemia

• Pernicious anemia results from inadequate vitamin B12 absorption, often due to lack of intrinsic factor, a stomach-secreted protein required for intestinal B12 absorption. Red blood cells are abnormally large, immature, and carry less hemoglobin.
• Genetic factors, chronic gastritis, and gastric surgery may also play a role. Primarily found in light-skinned women of northern European descent.

Vitamin B12 and Nerve Function

• Vitamin B12 is critical for neuron maintenance and function. Deficiency elicits peripheral nerve symptoms, which might be reversible.

Aplastic Anemia

• Aplastic anemia results from bone marrow impairment, which can be temporary or permanent. Possible causes include myelotoxins (radiation, chemicals, drugs), viruses (particularly hepatitis C), genetic abnormalities (like myelodysplastic syndrome and Fanconi anemia). Pancytopenia (low red blood cells, white blood cells, and platelets) is common in the blood.

Hemolytic Anemia

• Hemolytic anemia is excessive red blood cell destruction. Underlying causes include genetic defects, immune reactions and reactions to blood components, infections (like malaria), toxins, or incompatible blood transfusions. Erythroblastosis fetalis is an example of this regarding incompatibility of blood types.

Sickle Cell Anemia

• Sickle cell anemia is an inherited autosomal incomplete dominant genetic disorder. Abnormal hemoglobin (HbS) causes sickle-shaped red blood cells, especially in hypoxic states. These cells have trouble moving through the microcirculation because of their changed shape, leading to obstruction and multiple infarctions (areas of necrosis).
• Multiple infarctions impact the brain, bones, and organs. Other symptoms include hyperbilirubinemia, jaundice, gallstones, splenomegaly, and vascular occlusions. Symptoms usually appear after 12 months.

Polycythemia

• Polycythemia vera involves increased red blood cell production, while secondary polycythemia (erythrocytosis) is a response to prolonged hypoxia, characterized by increasing erythropoietin secretion as a compensatory mechanism.

Blood-Clotting Disorders

• Disorders may cause excessive bleeding (epistaxis, petechiae, purpura, ecchymosis, hemarthroses, hemoptysis, hematemesis, and blood in feces). Hemophilia A, a common inherited clotting disorder, lacks or affects Factor VIII and causes prolonged bleeding after injury. Von Willebrand disease is another common hereditary clotting disorder with varying types and severity causing various types of bleeding problems

Disseminated Intravascular Coagulation (DIC)

• DIC involves excessive bleeding and clotting, presenting a poor prognosis. It might result from obstetric complications, infections, cancers, and major trauma.

Thrombophilia

• Thrombophilia encompasses inherited or acquired disorders increasing clot risk in veins or arteries.

Myelodysplastic Syndromes

• Deficiencies in bone marrow production lead to symptoms such as anemia, dependent on the specific deficiency. Causes include idiopathic cases, chemotherapy, and radiation. Treatment varies by cause and depends on the deficiency type.

Leukemias

• Leukemias are neoplastic disorders involving uncontrolled white blood cell production in bone marrow or lymph nodes. Cells are undifferentiated, immature, non-functional, and released into the circulation, potentially accumulating in other organs.
• Acute leukemias (ALL and AML) have a high proportion of immature cells, are generally more abrupt in onset with worse symptoms. Chronic leukemias (CLL and CML) have some mature cells in the blood but have impaired function, are insidious, and have a better overall prognosis.

Arteriosclerosis and Atherosclerosis

• Arteriosclerosis refers to all arterial changes, causing loss of elasticity and lumen narrowing. Atherosclerosis is characterized by atheromas (plaque buildup), including lipids, calcium, or clots, in large arteries.
  • Lipid transport is important as LDLs deliver cholesterol to cells, contributing to atheroma formation, whereas HDLs carry cholesterol away from cells to the liver, effectively being a "good" lipoprotein.

Risk Factors for Atherosclerosis

• Nonmodifiable: age, gender, genetic factors.
• Modifiable: obesity, sedentary lifestyle, smoking, diabetes, poorly controlled hypertension, combination of oral contraceptives and smoking.

Peripheral Vascular Disease (PVD)

• Atherosclerosis impacting arteries outside the heart is known as PVD. Common in individuals with diabetes. Symptoms include leg pain associated with exercise (intermittent claudication), sensory changes (tingling, numbness), and changes in skin appearance (pallor, cyanosis, dry skin and hairless areas, thick and hard toenails).

Aortic Aneurysm

• Aortic aneurysm is a localized weakening and dilation of the arterial wall, potentially developing from defects, atherosclerosis, trauma, or infections (like syphilis). Types include saccular (bulging wall on one side), fusiform (circumferential dilation along an artery section), and dissecting (involving a tear in artery wall with dissecting tissues).

Venous Disorders

• Varicose veins are dilated, tortuous superficial veins often seen in legs due to valve or wall defects. Risks include increased body mass index, parity, and weight lifting. Thrombophlebitis is thrombus formation in an inflamed vein, while phlebothrombosis is clot formation in a vein without prior inflammation. Factors include blood stasis, endothelial damage, and increased blood coagulability.