Blood and Other Bodily Fluids Overview

1. Identify a few important functions of blood

• Blood serves multiple functions:

  1. Distribution of nutrients absorbed from the digestive tract.

  2. Transport of oxygen from lungs to cells throughout the body.

  3. Transport of carbon dioxide from cells to lungs for excretion.

  4. Transport of metabolic waste to kidneys for excretion.

  5. Transport of hormones from endocrine glands to target cells.

  6. Assists in body temperature regulation by distributing heat from deeper tissues to the surface.

  7. Maintains constant pH of body fluids by providing chemical buffers.

  8. Prevents excessive blood loss by providing necessary proteins for coagulation.

  9. Defends against disease by supplying antibodies, cells, and other factors.

2. List the components of blood

• Blood comprises cells and cell-like formed elements suspended in a fluid called plasma.

• Formed elements include erythrocytes (red blood cells), leukocytes (white blood cells), and platelets.

3. Define hematopoiesis and describe the origin of blood components

• Hematopoiesis: The process of forming and developing all blood components from pluripotent stem cells in bone marrow.

• Stem cells can give rise to myeloid and lymphoid lineages, known as progenitor cells.

  • Types of Blood Stem Cells:

  • Common myeloid progenitor

  • Common lymphoid progenitor

• The proliferation and differentiation of bone marrow stem cells are regulated by various hormonal signals, generally referred to as Hematopoietin.

4. Differentiate between erythrocytes, platelets, and leukocytes

• Erythrocytes (Red Blood Cells):

  • Structure: Biconcave disks, thick circular margin, thin center, lacking nuclei and organelles.

  • Primarily responsible for oxygen transport.

  • Count: Typical count in domesticated mammals is around 7 million cells per microliter.

  • Hemoglobin: Major protein, composed of four amino acid chains, each with a heme group containing iron. Binds oxygen at the ferrous iron in heme groups, forming oxyhemoglobin ($HbO_2$), a process called oxygenation.

  • Erythropoiesis: Formation stimulated by erythropoietin (a glycoprotein hormone released from kidneys in response to low oxygen levels).

  • Degradation: Occurs in the reticuloendothelial system (spleen, liver, bone marrow), recycling components.

  • Clinical Examples: Icterus (jaundice), Hemolysis, Hemagglutination, Anemia.

• Platelets (Thrombocytes):

  • Fragments derived from megakaryocytes in the bone marrow, lacking nuclei despite containing some organelles.

  • Count: Typical range is 150,000 to 500,000 per microliter of blood.

  • Role in Hemostasis: Help prevent blood loss by adhering to vessel walls and to each other at injury sites, forming a plug to support clot formation.

• Leukocytes (White Blood Cells):

  • Contain nuclei, exhibit independent movement, and are essential for immune defense against infections.

  • Classification of Leukocytes:

  • Granulocytes: Neutrophils, eosinophils, basophils (distinguished by staining).

  • Agranulocytes: Monocytes, lymphocytes (no distinct granules).

  • Functions of Different Leukocytes:

  • Neutrophils: Phagocytosis.

  • Eosinophils: Defense against parasites.

  • Basophils: Inflammatory and allergic responses.

  • Lymphocytes: Specific immune responses (T and B lymphocytes).

5. Explain what blood plasma is and its primary functions

• Blood plasma is the fluid component of blood, part of the extracellular fluid compartment.

• Composition: Roughly 92% water and 8% other substances including proteins and electrolytes.

  • Difference between plasma and interstitial fluid: Plasma has a higher concentration of proteins which cannot easily diffuse across capillary walls.

  • The kidneys help maintain the stability of plasma components through filtration and reabsorption.

• Predominant Proteins in Plasma: Classified into albumins and globulins.

  • Albumin is the main protein, synthesized by the liver.

  • Globulins are categorized by electrophoresis into alpha, beta, and gamma classes.

6. Understand the pH range of blood and its physiological implications

• Normal pH for blood ranges from 7.35 to 7.45.

• Blood pH is regulated by kidneys and respiratory mechanisms to maintain physiological balance.

7. Describe the three basic reactions of hemostasis

• Hemostasis involves three basic reactions:

  1. Vasoconstriction of injured vessel.

  2. Platelet plug formation.

  3. Clot formation.

• Platelets adhere to collagen exposed by endothelial damage, which is crucial for hemostasis.

8. Define lymph

• Lymph is fluid taken up by lymphatic vessels after a small net loss of fluid and protein from capillaries, returning it to circulation.

• Lymphatic vessels start as blind-ending structures, merging into larger vessels resembling veins.

• Edema: Swelling caused by the abnormal accumulation of fluid due to lymphatic obstruction.