Anatomy & Physiology: Blood (Chapter 17) Study Notes

Blood: Anatomy and Physiology Overview

Introduction

Blood is a vital connective tissue that plays essential roles in transport, regulation, and protection within the human body. Understanding its anatomy and physiology is crucial for clinical practice, including advising patients on activities to prevent blood clots during hospital stays.

Blood Terminology

Key Terms and Definitions

• Agglutination: Clumping of blood cells due to an antigen-antibody reaction. This is important in blood transfusions and immune responses.

• Albumin: The most abundant plasma protein, responsible for maintaining osmotic pressure and transporting substances.

• Antibody: A protein produced by plasma cells in response to an antigen; essential for immune defense.

• Anticoagulant: A substance that delays, suppresses, or prevents blood clotting (e.g., heparin, warfarin).

• Basophil: A type of white blood cell (WBC) with a pale nucleus and large granules that stain blue; involved in inflammatory responses.

• Bilirubin: An orange pigment, end product of hemoglobin breakdown in hepatocytes, excreted in bile as waste.

• Colony-Stimulating Factor (CSF): Molecules that stimulate the development of WBCs.

• Eosinophil: WBC with granules that stain pink; involved in combating parasites and allergic reactions.

• Erythrocyte: Mature red blood cell (RBC) responsible for oxygen and carbon dioxide transport.

• Erythropoietin: Hormone released by kidney cells to stimulate RBC production in bone marrow.

• Fibrinogen: Plasma glycoprotein that is converted to fibrin during blood clotting.

• Hematocrit: Percentage of blood volume made up of RBCs; a key indicator of oxygen-carrying capacity.

• Hemoglobin: Red pigment in RBCs, consisting of protein globin and iron-containing heme, transports O2 and CO2.

• Hematopoiesis: (Also called hemopoiesis) Blood cell production occurring in bone marrow after birth.

• Leukocyte: White blood cell (WBC); Leukopenia = low WBC count, Leukocytosis = high WBC count.

• Bone Marrow: Soft, sponge-like tissue in bone cavities that produces blood cells.

• Myeloid: Any WBC in bone marrow that is not a lymphocyte.

• Monocyte: Largest WBC, agranular, involved in phagocytosis.

• Neutrophil: WBC with pale purple granules; most abundant type, first responders to infection.

• Plasma: Liquid component of blood, containing water, proteins, nutrients, and waste products.

• Plasma Cell: B cell lymphocyte that produces antibodies.

• Platelet (Thrombocyte): Blood component essential for clotting.

• Pluripotent Stem Cell: Immature cell in bone marrow that gives rise to all blood cell precursors.

• Prothrombin: Inactive blood clotting factor made in the liver; converted to thrombin during clotting.

• Reticulocyte: Immature RBC, indicator of erythropoietic activity.

• Rh Factor: Inherited antigen on the surface of RBCs in Rh-positive individuals.

• Serum: Blood plasma minus clotting proteins.

• Emigration (Diapedesis): Process by which WBCs leave the bloodstream to enter tissues.

• Hemostasis: Sequence of responses that stops bleeding after vascular injury.

Blood Composition

Blood as a Connective Tissue

• Blood consists of an extracellular matrix called blood plasma that dissolves and suspends various cells and cell fragments.

• Interstitial fluid bathes body cells and is constantly renewed by blood, facilitating exchange of nutrients and wastes.

Functions of Blood

Major Roles in the Body

• Transport:

  • Oxygen from lungs to tissues

  • Nutrients from gastrointestinal tract to cells

  • Carbon dioxide and metabolic wastes from cells to lungs/kidneys for elimination

• Regulation:

  • Maintains pH through buffers

  • Regulates water content of cells via osmotic pressure

• Protection:

  • Prevents excessive blood loss via clotting mechanisms

  • Defends against disease through WBCs and plasma proteins (e.g., antibodies, complement)

Characteristics of Blood

Physical and Chemical Properties

• Density: Blood is denser and more viscous than water.

• pH: Slightly alkaline, with a normal range of 7.35–7.45.

• Color: Dark red indicates low oxygen content; bright red indicates high oxygen content.

• Volume: Average adult male: 5–6 L; average adult female: ~5 L.

Blood Plasma

Composition of Plasma

• Plasma makes up about 55% of total blood volume.

• Composed of approximately 91.5% water and 8.5% solutes (proteins and other substances).

• Main Plasma Proteins:

  • Albumin: Maintains osmotic pressure, transports substances.

  • Globulins: Include antibodies (immunoglobulins) for immune defense.

  • Fibrinogen: Precursor to fibrin, essential for blood clotting.

• Other Solutes: Electrolytes, nutrients, enzymes, hormones, gases, and waste products.

Formed Elements of Blood

Blood Cells and Platelets

• Red Blood Cells (Erythrocytes): Transport oxygen and carbon dioxide.

• White Blood Cells (Leukocytes): Defend against infection and disease. Types include:

  • Neutrophils: Phagocytize bacteria; most abundant WBC.

  • Eosinophils: Combat parasites and modulate allergic responses.

  • Basophils: Release histamine in allergic reactions.

  • Lymphocytes: B cells (produce antibodies), T cells (cell-mediated immunity).

  • Monocytes: Differentiate into macrophages for phagocytosis.

• Platelets (Thrombocytes): Cell fragments essential for blood clotting.

Summary Table: Main Components of Blood

Component	Percentage	Main Function
Plasma	~55%	Transport of nutrients, wastes, hormones, proteins
Red Blood Cells	~45%	Oxygen and carbon dioxide transport
White Blood Cells	<1%	Immune defense
Platelets	<1%	Blood clotting

Additional info:

• Blood cell formation (hematopoiesis) occurs in red bone marrow, with pluripotent stem cells differentiating into various blood cell types.

• Hemostasis involves three main steps: vascular spasm, platelet plug formation, and coagulation (clotting).

• Normal hematocrit values: males ~40–54%, females ~38–46%.

• Key equation for oxygen transport: $\text{O}_2 + \text{Hb} \rightleftharpoons \text{HbO}_2$ (where Hb = hemoglobin).