Chapter 18-Blood-

Blood Composition

• Blood Composition Overview

  • Fluid connective tissue

  • Composed of:

    • Plasma: non-living fluid matrix

    • Formed elements: living blood cells suspended in plasma

      • Erythrocytes (Red Blood Cells)

      • Leukocytes (White Blood Cells)

      • Platelets

Spun Blood Sample

• Three Layers Obtained by Centrifugation:

  • Plasma on top (~55%)

  • Erythrocytes on bottom (~45%)

  • WBCs and Platelets in Buffy Coat (< 1%)

• Hematocrit:

  • Percentage of blood volume that is RBCs

  • Males: 47% ± 5%; Females: 42% ± 5%

Physical Characteristics of Blood

• Properties:

  • Sticky, opaque fluid with metallic taste

  • Color varies with O2 content:

    • High O2: scarlet

    • Low O2: dark red

  • pH: 7.35–7.45

  • ~8% of body weight

  • Average volume: 5–6 L for males; 4–5 L for females

Functions of Blood

• Distribution Functions:

  • Delivery of O2 and nutrients to cells

  • Transport of metabolic wastes to lungs/kidneys

  • Transport of hormones from glands to targets

• Regulatory Functions:

  • Maintenance of body temperature

  • Regulation of pH levels

  • Maintenance of adequate fluid volume

• Protection Functions:

  • Preventing blood loss via clot formation

  • Preventing infection through WBCs and antibodies

Blood Plasma Composition

• Water: 90% of plasma

• Solutes:

  • Electrolytes, nutrients, gases, wastes, hormones

  • Proteins:

    • 60% Albumin (main contributor to osmotic pressure)

    • 36% Globulins (transport proteins)

    • 4% Fibrinogen (key to clotting)

Formed Elements Overview

• Composition:

  • Only WBCs are complete cells; RBCs lack nuclei and organelles

  • Most blood cells arise in red bone marrow

Erythrocytes Structure

• Characteristics:

  • Biconcave shape; anucleate

  • Filled with Hemoglobin for gas transport

• Gas Transport:

  • High surface area aids in gas exchange

  • No mitochondria; uses anaerobic ATP production

Erythropoiesis

• Production Stages:

  • Myeloid stem cell transforms into proerythroblast

  • Development stages:

    • Basophilic -> Polychromatic -> Orthochromatic erythroblasts -> Reticulocytes

Regulation of Erythropoiesis

• Hormonal Control:

  • Erythropoietin (EPO) stimulates RBC production

  • Essential nutrients: iron, amino acids, B vitamins

Hemostasis

• Process:

  • Vascular spasm, platelet plug formation, coagulation

  • Requires clotting factors and platelet chemicals

Blood Groups

• ABO and Rh Blood Groups:

  • RBC antigens and antibodies dictate blood types

  • Mismatched transfusions can lead to agglutination and catastrophic reactions

Common Blood Disorders

• Anemia:

  • Low O2-carrying capacity; causes: blood loss, low production, high destruction

• Leukemia:

  • Overproduction of abnormal WBCs, requiring treatment

• Platelet Disorders:

  • Thrombocytopenia: low platelet count leading to bleeding issues

Blood Composition

Blood Composition Overview

Blood is a vital fluid connective tissue that performs numerous functions crucial for sustaining life. It is composed of two primary components:

1. Plasma: This is a non-living fluid matrix, making up about 55% of blood volume. Plasma is primarily composed of water (90%), with solutes such as electrolytes, nutrients, hormones, gases, and waste products dissolved in it. The proteins in plasma also play significant roles, including:

   • Albumin (60%): A protein that helps maintain osmotic pressure and blood volume.

   • Globulins (36%): These serve as transport proteins and play a role in immune function as antibodies.

   • Fibrinogen (4%): This is crucial for blood clotting.

2. Formed Elements: These include living blood cells suspended in plasma which consist of:

   • Erythrocytes (Red Blood Cells): Responsible for the transport of oxygen (O2) and carbon dioxide (CO2) due to the presence of hemoglobin.

   • Leukocytes (White Blood Cells): These are key components of the immune system and help protect the body against infections and foreign invaders.

   • Platelets: Cell fragments essential for clotting and wound healing.

Spun Blood Sample

A spun blood sample, obtained through centrifugation, reveals three distinct layers:

• Plasma: Situated on top (~55% of the sample)

• Erythrocytes: Located at the bottom (~45% of the sample)

• WBCs and Platelets: Found in the buffy coat, which comprises less than 1% of the blood sample.

• Hematocrit: This term refers to the percentage of blood volume that is made up of erythrocytes. Typical values for hematocrit are approximately 47% ± 5% for males and 42% ± 5% for females.

Physical Characteristics of Blood

Blood possesses several distinct physical characteristics:

• It is a sticky, opaque fluid that has a metallic taste.

• The color of blood varies according to its oxygen content; it appears scarlet when oxygen-rich and dark red when oxygen-poor.

• The pH of blood typically ranges from 7.35 to 7.45, which is slightly alkaline.

• Blood constitutes about 8% of total body weight, with an average volume of approximately 5-6 liters in males and 4-5 liters in females.

Functions of Blood

Blood performs several critical functions, which can be categorized into:

1. Distribution Functions:

   • Delivery of oxygen (O2) and essential nutrients to the body's cells.

   • Transport of metabolic wastes (like carbon dioxide) to lungs and kidneys for removal.

   • Conveyance of hormones from endocrine glands to target organs.

2. Regulatory Functions:

   • Maintenance of body temperature through heat distribution.

   • Regulation of the pH levels in body tissues to maintain homeostasis.

   • Maintenance of adequate fluid volume within the circulatory system.

3. Protection Functions:

   • Prevention of blood loss through the creation of blood clots to seal wounds (hemostasis).

   • Defense against infection, utilizing white blood cells and antibodies to combat pathogens.

Blood Groups

The human blood system can be categorized based on the presence of specific antigens on the surface of erythrocytes, which define ABO and Rh blood groups. Understanding blood types is crucial, especially for blood transfusions, as mismatched transfusions can lead to agglutination and potentially fatal reactions.

Common Blood Disorders

Several blood disorders can affect general health, including:

• Anemia: Characterized by reduced oxygen-carrying capacity, which may result from blood loss, low erythrocyte production, or high destruction of red blood cells.

• Leukemia: A type of cancer marked by the overproduction of abnormal white blood cells, requiring medical intervention and treatment.

• Platelet Disorders: Such as thrombocytopenia, which involves a low platelet count that can lead to excessive bleeding and challenges in blood clotting.