Body Fluids and Blood Functions

Body Fluid

• Body fluid is a dilute watery solution present in the body
• Intracellular fluid (ICF) is found within the cell
• Extracellular fluid (ECF) is found outside the cell
• Interstitial fluid fills the narrow spaces between cells and tissues and is a part of ECF
• Intravascular fluid is found within blood vessels and is a part of ECF
• Lymph is found in lymph vessels
• Cerebrospinal fluid surrounds the spinal cord and brain
• Aqueous humor and vitreous humor are ECF of the eye

Blood & Its Function

• Blood is fluid connective tissue
• Blood is interstitial fluid
• Extracellular matrix of blood is plasma
• Cells are suspended in plasma
• Transportation function of blood includes carrying oxygen, carbon dioxide, nutrients, hormones, and waste products
• Regulation function of blood includes maintaining pH, temperature, osmotic pressure, and water balance
• Protection function of blood includes coagulation, white blood cell phagocytosis, and blood proteins (antigens, antibodies, interferons)

Blood Physical Characteristics

• Blood is denser and more viscous than water and has a slightly sticky feel
• Blood temperature is 38 degrees Celsius
• Blood pH is slightly alkaline (7.5 to 7.45)
• Red blood cell (RBC) color varies depending on oxygen level, and blood is 20% extracellular fluid and 8% of total body mass
• Average blood volume for males is 5 to 6 liters and for females is 4 to 5 liters
• When blood is centrifuged, the denser red blood cells settle at the bottom (99% formed elements)
• The middle layer is the buffy coat which contains white blood cells and platelets
• The top layer is plasma

Blood Composition

• Blood consists of approximately 55% plasma and 45% formed elements
• Plasma is primarily water (91.5%) with proteins (7%), and other solutes (1.5%)
• Key proteins in plasma: albumin, globulin, fibrinogen etc
• Formed elements are the cellular components of blood: red blood cells (RBC), white blood cells (WBC), and platelets
• RBCs carry oxygen and carbon dioxide
• WBCs are nucleated, defend against infection
• Platelets are cell fragments involved in clotting

Blood Plasma

• Blood plasma is a straw-colored liquid
• It is 91.5% water and 8.5% solutes (7% proteins and 1.5% other substances)
• Some proteins found in other body fluids are also found in blood plasma and are called plasma proteins
• Gamma globulins, known as antibodies or immunoglobulins, are crucial for the immune response to foreign substances
• Other solutes in plasma include electrolytes, hormones, gases, enzymes, nutrients, and waste products

Formed Elements

• RBCs are non-nucleated, carry oxygen and carbon dioxide throughout the body
• WBCs are nucleated cells that defend the body against infections
• Platelets are cell fragments that play a key role in blood clotting, also part of the formed elements
• RBC percentage in a sample of blood is called hematocrit
• A drop in hematocrit can indicate anemia, and a high hematocrit can indicate polycythemia

Hemopoiesis

• Hemopoiesis is the process of blood cell formation
• It starts from stem cells in red bone marrow
• It occurs in the yolk sac before birth
• After birth, it occurs in the liver, spleen, thymus, and lymph nodes of a fetus
• Hormones (hemopoietic growth factors) control proliferation and differentiation during hemopoiesis
• Erythropoietin, produced by the kidney, regulates the production of red blood cells
• Thrombopoietin, produced by the liver, stimulates white blood cell formation

RBC/Hemoglobin (Hb)

• Red blood cells (RBCs) use hemoglobin (Hb) to carry oxygen
• RBCs also carry carbon dioxide and nitric oxide
• RBCs contain carbonic anhydrase to facilitate converting carbon dioxide into bicarbonate
• RBCs typically live for 120 days and are worn out through use, causing them to break down
• The breakdown products are recycled by macrophages in the liver and spleen

WBC Function

• White blood cells (WBCs) have a far lower count than red blood cells (RBCs) in a healthy body
• WBCs live for months or years in a healthy body; a shorter duration for an infection
• Leukocytosis is an increase in the number of WBCs, often due to infection
• Leukopenia is a decrease in the number of WBCs, which could be due to radiation, shock, chemotherapy, or other medical reasons
• WBCs combat microbes that enter the body
• Leukocytes (WBCs) leave the blood and enter tissues where they combat infections

Granulocytes (WBC)

• Differentiate staining in granulocytes show three types of granules with distinct colors
• Neutrophils have smaller granules, lilac colored nucleus with 2-5 lobes connected by thin strands
• Eosinophils have large uniform size granules, red-orange colored granules and do not cover the 2-lobed nucleus and connected by thin strands
• Basophils have round variable size nucleus stained with a blue-purple color and granules covering the nucleus with a 2-lobed nucleus

Agranulocytes (WBC)

• Granules of agranulocytes are small, poor staining and are not visible under a light microscope
• Lymphocytes have dark-staining, round nuclei and light-blue cytoplasm. Classified as large or small based on size.
• Monocytes have bean-shaped nuclei and grayish-blue-foam-like cytoplasm. They migrate from blood to tissues and mature into macrophages, which engulf foreign particles

WBC Function

• Basophils leave capillaries and enter inflammation sites; secrete heparin, histamine, serotonin
• These substances intensify inflammation and allergic reactions
• Lymphocytes are major immune cells
• B lymphocytes destroy bacteria and neutralize toxins
• T lymphocytes attack infected body cells and tumor cells

Hemostasis

• Hemostasis is a sequence of events that stop bleeding
• Three mechanisms are involved: vascular spasm, platelet plug formation, and blood clotting
• Blood clotting occurs in localized regions of damage to prevent large amounts of blood loss
• Large blood vessels requiring medical intervention to stop bleeding

Blood Clotting

• Blood clotting is a process of gel formation, or coagulation
• It involves a series of chemical reactions and clotting factors
• Extrinsic pathway, Intrinsic pathway, Common pathway

Vitamin K

• Normal blood coagulation depends significantly on adequate vitamin K levels
• Vitamin K is necessary for the synthesis of four important clotting factors: II, VII, IX, and X along with protein C and S

Clotting Factors

• Blood clotting depends on the actions of various clotting factors
• Several factors are involved in the complex process of blood clotting

Homeostatic Control

• Small clots form initially on blood vessel surfaces, acting as a foundation for larger clots
• The fibrinolytic system dissolves these smaller clots
• Several anticoagulant substances prevent or delay clotting in the blood
• Combinations of factors contribute to these actions

Blood Grouping and Typing

• Blood types are categorized based on the presence or absence of specific antigens
• ABO and Rh blood types are the most common classification systems

Blood Transfusion

• Blood transfusion is the transfer of blood or blood components to a recipient.
• This is done to treat conditions like anemia or increase blood volume
• Normal antigen-antibody reaction can cause clumping of red blood cells (agglutination) and can harm the recipient, leading to potentially fatal consequences
• Donation of wrong blood type can result in significant health complication, even death if not treated immediately

Rh Factor

• Rh antigen presence on RBCs are categorized as either Rh-positive or Rh-negative
• Individuals who lack the Rh antigen are considered Rh-negative
• Rh-negative individuals lack the corresponding antibody in their plasma
• If an Rh-negative person receives Rh-positive blood, they can develop antibodies against the Rh antigen, potentially leading to complications

Hemolytic Disease of the Newborn

• If a Rh-negative mother becomes pregnant with an Rh-positive fetus, the mother's immune system can react negatively to the Rh antigens in the fetus's blood
• This reaction can cause severe problems for the fetus or newborn

Blood Group Detection

• Blood type detection is essential to determine compatibility for blood transfusions
• Test kits containing antibodies (antisera) are used to determine blood type by observing agglutination of red blood cells

Lymphatic System

• The lymphatic system is part of the immune system and supports cardiovascular function
• It drains excess interstitial fluid, transports dietary lipids, and provides an immune response
• Lymphatic vessels, tissues, and organs are involved in the function of this system

Lymphatic Organs and Tissues

• Lymphatic organs are central to the body's immune system
• Primary lymphatic organs are sites where stem cells divide and mature into immunocompetent cells
• Secondary lymphatic organs are sites where most immune responses occur

Thymus

• The thymus is a bilobed primary lymphatic organ
• It is located between the sternum and aorta in the mediastinum
• The thymus cortex and medulla contain specialized cells and tissues for T cell maturation

Lymph Nodes

• Lymph nodes are small, bean-shaped organs situated along lymphatic vessels
• They filter lymph and house immune cells for a response
• Lymph nodes are an important component of the lymphatic system
• The cortex and medulla contain immune cells

Spleen

• The spleen is a large lymphatic organ located in the upper left quadrant of the abdomen, below the diaphragm
• It contains white pulp and red pulp
• white pulp is lymphatic tissue that's important for immune responses; red pulp removes worn-out red blood cells and stores platelets
• The spleen filters blood and removes foreign particles

Innate Immunity: First Line Defense

• Physical and chemical barriers in the body provide the first line of defense against pathogens, these are important components of innate immunity
• Skin, mucous membranes, secretions provide a physical barrier limiting the entry of many microbes
• Other first line defenses include periodic shedding of skin cells, secretion of mucus, actions of cilia, enzyme lysozyme

Innate Immunity: Second Line Defense

• Immune cells work together to provide a second line of defence against many outside threats, these are important components of innate immunity.
• Antimicrobial substances in innate immunity, include interferons, complement system, transferrin, lactoferrin, ferritin, antimicrobial peptides, natural killer cells, phagocytes

Inflammation

• Inflammation is a non-specific bodily response to tissue damage, pathogens, and other harmful stimuli
• Symptoms like pain, redness, warmth, and swelling result from this response

Fever

• Fever is an abnormally high body temperature caused by reset of the hypothalamic thermostat

Phagocytosis

• Phagocytosis is a type of endocytosis employed by phagocytic cells to engulf microbes, dead or worn-out cells, debris
• Chemotaxis, adherence, ingestion, and killing are steps of the phagocytosis process

Adaptive Immunity

• Adaptive immunity is a specific type of immunity in the body's immune system involving the creation of a targeted response against a specific invader
• Adaptive immunity is triggered in response to specific antigens such as foreign agents, bacteria, toxins
• Adaptive immunity is also characterized by immunological memory

Adaptive Immunity: T and B Cells

• T cells and B cells are key components in adaptive immunity, both undergo a maturation process for immunocompetency
• Activated T cells play key roles in cell-mediated immunity (attacking infected body cells) and some types of T cells are involved in helping regulate B cells or other T cells
• B cells develop into plasma cells that produce antibodies in response to specific antigens
• Their antibody action includes neutralizing antigens, immobilizing antigens, agglutinating antigens, activating complement system, and enhancing phagocytosis

Adaptive Immunity: Clonal Selection

• Lymphocytes with complimentary antigens undergo proliferation and differentiation, giving rise to a clone of identical cells known as effector cells
• The clone of cells effectively targets the specific antigen that triggered the response.

Adaptive Immunity: Antigen Receptors

• Antigens play a critical role in provoking immune responses with characteristics such as immunogenicity and reactivity;
• Antigens are complex molecules present on the surfaces of pathogens, toxins, or other foreign substances that initiate an immune response
• This response is triggered by the ability of immune system cells, namely T and B cells, to distinguish between the organism’s own components and foreign entities

Adaptive Immunity: Cytokines

• Cytokines are important regulatory molecules in various bodily responses, including immunity
• Cytokines can regulate cell proliferation, cell differentiation, and other processes within the cell
• Cytokines are produced by various cells to regulate the overall immune response of the body

Cell Mediated Immunity

• Cell-mediated immunity is a type of adaptive immunity in which specialized cells, known as cytotoxic T cells, directly attack and destroy cells infected with pathogens, abnormal cells, or transplanted tissues

Antibody Mediated Immunity

• Antibody-mediated immunity involves the production of antibodies that bind to specific antigens, neutralizing or eliminating them
• Specific antibodies are produced in response to particular antigens
• This response includes a memory component; the body remembers a particular antigen after exposure, allowing faster and more potent subsequent responses

Immunological Memory

• The immune system remembers antigens encountered in the past through memory cells, permitting a faster and more efficient response upon subsequent exposure to the same antigen
• Memory cells are crucial for long-term immunity against specific pathogens

Self Recognition and Tolerance

• Self-recognition involves the immune system correctly identifying molecules as belonging to the body, and its cells must also not attack itself due to tolerance
• Self-tolerance mechanisms prevent the immune system from targeting its own healthy cells in a process known as negative selection

Explore the essential concepts of body fluids and the critical functions of blood in this quiz. Understand the differences between intracellular and extracellular fluids, as well as the transportation and regulatory roles of blood in the body. Test your knowledge on this vital topic in human biology.