Blood Functions and Composition

Blood Functions

• Blood transports oxygen from the lungs to body tissues, removes carbon dioxide, and carries nutrients, hormones, and waste products
• Blood regulates fluid and electrolyte balance, acid-base balance, and body temperature
• White blood cells in the blood defend against infections, and platelets aid in blood clotting to prevent excessive bleeding
• Blood helps maintain stable internal conditions through heat distribution and electrolyte balance

Blood Components and Percentages

• Plasma makes up 55% of total blood volume
• Erythrocytes (red blood cells) constitute 45% of total blood volume
• The buffy coat, consisting of leukocytes (white blood cells) and platelets, accounts for less than 1% of total blood volume

Blood Plasma Composition

• Blood plasma is composed mainly of water and has a pale yellow color
• Blood plasma transports nutrients, hormones, and waste, and maintains blood pressure and volume
• Water (90-92%) acts as a solvent and helps transport substances in plasma
• Proteins (7-8%) found in plasma include albumin, globulins, and fibrinogen
• Albumin maintains osmotic pressure and transports substances
• Globulins aid in immune response as antibodies
• Fibrinogen plays a role in blood clotting
• Nutrients found in plasma include glucose, amino acids, fatty acids, vitamins, and minerals
• Gases such as oxygen (O2) and carbon dioxide (CO2) are present in plasma
• Hormones found in plasma regulate body functions
• Electrolytes, including sodium (Na+), potassium (K+), calcium (Ca²+), chloride (Cl¯), and bicarbonate (HCO3¯), help maintain pH and fluid balance
• Waste products like urea, creatinine, and uric acid are metabolic wastes removed by the kidneys

Plasma Protein Functions

• Plasma proteins regulate fluid volume by albumin, protect the body from pathogens via antibodies, and prevent excess blood loss through clotting factors
• Albumin maintains osmotic pressure, regulates fluid balance, and transports hormones, fatty acids, and drugs
• Globulins are involved in immune response, transport lipids, vitamins, and iron, accounting for 35% of plasma proteins
• Fibrinogen constitutes 4% of plasma proteins and facilitates blood clot formation to stop bleeding
• Regulatory proteins, making up less than 1% of plasma proteins, include enzymes and hormones that assist in metabolic processes

Serum

• Serum defined as plasma without the clotting proteins

Blood Cell Types Comparison

• Erythrocytes (Red Blood Cells - RBCs): Originate in red bone marrow, biconcave in shape, lack a nucleus, contain hemoglobin for oxygen transport, live for 120 days, and are recycled by the spleen
• Leukocytes (White Blood Cells - WBCs): Originate in red bone marrow (some mature in lymphatic tissue), have 5 types, are nucleated and larger than RBCs, migrate into lymph tissue or sites of infection/inflammation, and protect the body from harmful invaders and infections through immune response
• Thrombocytes (Platelets): Originate in red bone marrow, small cell fragments without a nucleus, and function in blood clotting (hemostasis) to protect the body from bleeding

Red Blood Cell Life Cycle: Production (Erythropoiesis)

• Low oxygen levels (hypoxia) trigger the kidneys to release erythropoietin (EPO)
• EPO stimulates the bone marrow to produce RBCs
• Immature RBCs (reticulocytes) are released and mature within 24–48 hours

Red Blood Cell Life Cycle: Circulation

• Mature RBCs circulate in the bloodstream for about 120 days, transporting oxygen (O2) and carbon dioxide (CO2)

Red Blood Cell Life Cycle: Aging and Destruction

• Old or damaged RBCs are removed by the spleen and liver
• Hemoglobin breaks down and iron is recycled for new RBCs
• Heme is converted into bilirubin, which is excreted in bile

Red Blood Cell Life Cycle: Regulation

• As RBC levels rise, oxygen delivery improves
• The kidneys decrease EPO production, preventing an excess of RBCs

White Blood Cell Types

• Neutrophils: 55-70% of WBCs, function in phagocytosis
• Eosinophils: 1-3% of WBCs, involved in inflammatory responses, parasitic infection, and allergies
• Basophils: 0-1% of WBCs, involved in inflammatory responses and release heparin
• Lymphocytes: 25-38% of WBCs, provide immunity
• Monocytes: 3-8% of WBCs, function in phagocytosis

Hemostasis Steps

• Spasm: An injured vessel spasms, with platelets and trapped red blood cells (RBCs) at the injury site
• Platelet Plug Formation: Platelets accumulate to form a platelet plug
• Clot Formation: A clot forms with red blood cells (RBCs) enmeshed in fibrin threads

Clotting Factor Functions

• Prothrombin: Inactive enzyme that converts into thrombin by prothrombin activator (PTA)
• Thrombin: Activator enzyme that converts fibrinogen into fibrin
• Fibrinogen: Liquid protein that becomes fibrin when activated by thrombin
• Fibrin: Clot-forming net that forms a mesh to trap blood cells and stabilize the clot

Blood Clot Formation Steps

• Injury to the blood vessel leads to activation of clotting factors, forming prothrombin activator (PTA)
• PTA, calcium, and platelet chemicals convert prothrombin into thrombin
• Thrombin activates fibrinogen, turning into a fibrin net, that forms and stabilizes the clot

Rh-Positive Blood Characteristics

• Blood with the Rh (Rhesus) antigen on the surface of red blood cells
• Has the Rh (D) antigen on red blood cells, but does not produce anti-Rh antibodies
• Can receive both Rh-positive and Rh-negative blood if the ABO type is compatible
• Approximately 85% of the population is Rh-positive

ABO Blood Types and Compatibility

• Type A: A antigens on RBCs, anti-B antibodies in plasma; can receive A, O blood and donate to A, AB
• Type B: B antigens on RBCs, anti-A antibodies in plasma; can receive B, O blood and donate to B, AB
• Type AB: A and B antigens on RBCs, no antibodies in plasma; universal receiver, can receive A, B, AB, O blood and donate to AB
• Type O: No antigens on RBCs, anti-A and anti-B antibodies in plasma; universal donor, can receive O blood and donate to O, A, B, AB

Respiratory System Functions

• Provides gas exchange by delivering oxygen and removing carbon dioxide
• Filters and moistens incoming air
• Regulates pH levels
• Produces and modifies sounds, including speech
• Contains olfactory receptors for detecting odors

Pleural Membrane Roles

• Lubrication: Secretes serous fluid (about 25 mL) to reduce friction
• Smooth Movement: Membranes can slide past each other smoothly during breathing, minimizing discomfort
• Protection and Support: Protects the lungs and allows them to expand and contract efficiently without friction

Alveoli and Forces Affecting Them

• Negative intrapleural pressure favors expansion of alveoli, with pressure lower than inside the lungs helping to keep them expanded
• Elastic recoil favors collapse of alveoli, as the lungs naturally recoil or shrink
• Surfactant favors expansion of alveoli, reducing surface tension and helping keep them open
• Surface tension favors collapse of alveoli, as fluid lining alveoli tends to make them collapse, and is counteracted by surfactant

Ventilation Process Terms

• Inhalation (Inspiration): terms include Contraction of diaphragm, Increased thoracic size, Decreased thoracic pressure, and Inspiration
• Exhalation (Expiration): terms include Relaxation of diaphragm, Decreased thoracic size, Increased thoracic pressure, and Expiration

Lung Volumes

• Tidal Volume: the volume of air moved into or out of the lungs during a normal breath; about 500 mL
• Inspiratory Reserve Volume: the volume of air that can be forcefully inhaled after normal inhalation; about 3000 mL
• Expiratory Reserve Volume: the volume of air that can be forcefully exhaled after a normal exhalation; about 1100 mL
• Residual Volume: the volume of air that remains in the lungs after a forceful exhalation; about 1200 mL

Alveoli as Ideal Gas Exchange Environment

• Large Surface Area: Millions of alveoli (about 350 million per lung) create a surface area roughly half the size of a tennis court
• Thin Alveolar & Capillary Walls: Allows for easier diffusion of gases
• Close Proximity to Capillaries: Ensures a high rate of diffusion of gases

Oxygen and Carbon Dioxide Transport in Blood

• Oxygen: Almost all (98%) is transported by hemoglobin in red blood cells. The remaining 2% is dissolved in plasma. Oxygen binds to hemoglobin to form oxyhemoglobin
• Carbon dioxide: Blood carries carbon dioxide from cells to the lungs in three forms. About 70% is converted into bicarbonate ions (HCO3-), 20% combines with hemoglobin to form carbaminohemoglobin, and 10% dissolves in plasma

Effect of Increased Carbon Dioxide

• Increased carbon dioxide leads to a decrease in blood pH, stimulating chemoreceptors and leading to increased respiratory rate to expel excess carbon dioxide and maintain homeostasis

Lung Volume Definitions

• Tidal Volume: Air normally moved in one breath
• Residual Volume: Air that remains after forced exhalation
• Inspiratory Reserve Volume: Air that can be forcefully inhaled
• Expiratory Reserve Volume: Air that can be forcefully exhaled

Systemic Circulation Description

• Starts from the left side of the heart
• Blood flows through the aorta to supply oxygen to the whole body
• Deoxygenated blood returns to the right side of the heart via the superior and inferior vena cava
• Larger circulation because it covers the entire body with the exception of the lungs

Pulmonary Circulation Description

• Originates from the right side of the heart
• Blood goes through the pulmonary artery to the lungs to get oxygen and release carbon dioxide
• Oxygenated blood returns to the left side of the heart via the pulmonary veins
• Smaller circulation as it is limited to the lungs

Blood Vessel Wall Layers

• Tunica Intima (Inner Layer): Innermost layer composed of endothelium allowing smooth blood flow
• Tunica Media (Middle Layer): Thickest layer, made of elastic tissue and smooth muscle; thickness varies depending on the blood vessel type. Arterioles have more smooth muscle for contraction and relaxation
• Tunica Adventitia (Outer Layer): Outermost layer composed of tough connective tissue providing support and protection to blood vessels

Artery Function & Structure

• Carry blood away from the heart
• Large arteries branch into smaller arteries and eventually arterioles (smallest arteries)
• Most arteries carry oxygenated blood, hence they are color-coded red

Capillary Function

• Connect arterioles to venules
• Smallest and most numerous blood vessels
• Blood gives up oxygen to tissues, unoxygenated blood is bluish as it leaves the tissues. Located close to every cell to supply oxygen and nutrients
• Color changes from red to blue as blood loses oxygen

Vein Function

• Carry blood back to the heart
• Small veins are called venules that converge into larger veins
• Most veins carry unoxygenated blood, so they are color-coded blue
• Largest veins empty blood into the right atrium of the heart

Blood Vessel Function

• Arteries: Conductance vessels connect from heart to arterioles
• Arterioles: Resistance vessels; muscle contraction and relaxation changes vessel diameter, altering resistance to blood flow
• Capillaries: Exchange vessels; nutrients, gases, and wastes exchange between blood and interstitial fluid
• Veins/Venules: Capacitance vessels; collect and return blood from the tissues to the heart

Liver Blood Supply

• The liver is essential in metabolizing glucose, fats, and proteins and it receives nutrient-rich blood (from the digestive system) via the hepatic portal vein
• The liver regulates glucose (stored as glycogen or released to maintain normal blood sugar) and processes nitrogen (urea excretion).
• Hepatic Artery: Branches off the celiac trunk from the abdominal aorta, delivering blood and oxygen to the liver
• Hepatic Veins: Drain blood from the liver into the inferior vena cava
• Hepatic Portal System: Delivers venous blood, rich in digestive products (80% of the blood flow), to the liver for processing
• Portal Vein: Formed by the union of the superior mesenteric vein and the splenic vein delivering nutrient-rich blood from digestion directly to the liver

Blood Pressure Components

• Blood pressure = Cardiac Output x blood vessels (systemic vascular resistance)
• Cardiac Output (CO) Amount of blood pumped per minute determined by heart rate and stroke volume
• Peripheral Resistance (PR) Opposition to blood flow caused by resistance in smaller arteries and arterioles
• Blood Volume: Total amount of blood in the circulatory system is also a factor. An increase of this raises blood pressure, while a decrease can lower it

Cardiac Output Components

• Heart Rate (HR): Number of times the heart beats per minute, controlled by sinoatrial (SA) node (pacemaker); Normal resting HR is 60–100 beats/min, averages in at 72 beats/min, and is influenced by size, gender, age, exercise, autonomic nervous system, hormones, pathology & medications
• Stroke Volume (SV): Amount of blood pumped by the ventricle per beat and the normal resting SV is 60–80 mL/beat. The ventricles pump out about 67% of their blood per beat.

Cardiac Output Formula

• Cardiac Output (CO) = Heart Rate (HR) × Stroke Volume (SV)

Baroreceptors

• Pressure receptors located in the walls of the aortic arch and carotid sinus that sense sudden changes in blood pressure and send signals accordingly
• Activation & Signal Transmission: sensory nerves carry BP change messages to the brain via cranial nerve IX (glossopharyngeal) and cranial nerve X (vagus nerve)
• Interpretation in the Brain: The medulla oblongata (part of the brainstem) processes the sensory information
• Response & Regulation: Medulla oblongata sends signals through motor nerves to the heart and blood vessels via the autonomic nervous system, leading to an increase or decrease in blood pressure.

Lymphatic System Main Functions

• Fluid Balance: Absorbs fluid and protein from tissue spaces and returns them to the blood
• Fat Absorption: Specialized lymphatic vessels absorb fats and fat-soluble vitamins in the intestines
• Immune Defense: Lymphatic tissue helps the body defend against disease

Lymph Description

• Definition: A clear, pale yellow fluid
• Composition:
  • Water (major component)
  • Electrolytes (ions essential for cell function)
  • Waste products (from metabolizing cells)
  • Proteins (that leaked from capillaries into tissue spaces)
• Origin:
  • Blood capillaries continuously filter water and dissolved substances into the interstitial space, forming tissue fluid.
  • 85% of this tissue fluid re-enters blood capillaries and returns to circulation through venous blood
• Destination:
  • Lymphatic capillaries absorb this excess fluid, turning it into lymph
  • Lymphatic capillaries collect excess tissue fluid, flowing it through larger lymphatic vessels.
  • This eventually drains into the venous circulation; returning to the bloodstream

First Line Defenses

• Mechanical Barriers
  • Skin (physical/pathogen barrier)
  • Mucous membranes (Traps respiratory, digestive, urogenital pathogens )
  • Cilia (Hair structures move airways out)
• Chemical Barriers
  • Stomach acid (ingested pathogens)
  • Sweat and oils (skin and acidic environment)
  • Lysozyme (breakdown of bacterial cell walls)
• Reflexes
  • Coughing (Clears airway irritants)
  • Sneezing (expels respiratory pathogens)
  • Blinking protects eyes from foreign particles

Second Line Defenses

• Fever decreases pathogen ability to multiply
• Inflammation limits injury effects on body tissue
• Interferon prevents viral replication
• Complement causes bacterial cell membranes’ lysis
• Phagocytes ingest/digest pathogens
• Natural killer cells destroy virus infected/cancer cells

Cell-Mediated Immune Response

• Step 1: Origin, maturation, seeding - T cells made in bone marrow, become mature in the thymus and migrate to peripheral lymphoid organs to prepare for immune response
• Step 2: Antigen Presentation - Macrophages “present” pathogens to T cells
• Step 3: T Cell Activation - Helper T cells bind to MHC II on APC’s and release cytokines to activate other T cells; Cytotoxic T Cells bind to MHC I on infected cells, preparing to attack
• Step 4: Clone Formation - Active T Cells proliferate and differentiate into cytotoxic T cells (destroy cells), and memory T cells (stored for the future)

T Helper Cell

• Activates and regulates other immune cells by releasing cytokines to help B cells produce antibodies and cytotoxic T cells activate

T Cytotoxic Cell

• Kills infected, cancerous, or abnormal cells through cell-to-cell combat
• Releases perforin and granzymes to induce apoptosis - targets MHC I presented cells

T Suppressor Cell

• Prevents autoimmunity y suppressing immune responses
• Maintains immune system balances and prevents tissue damage
• Inactivates B/T cells

T Memory Cell

• Provides long term immunity by remaining in the body
• Responds faster/stronger and reduces severity of the infection when reinfected

Antibody-Mediated Immune Response

• Step 1: Origin, Maturation and Seeding - B cells originate/mature in the bone marrow, and await
• Step 2: Antigen Presentation the T cells recognizes the pathogen’s anitgens
• Step 3: B and Helper T-Cell Activation Helper T recognized antigens and releases cytokines activate B cell
• Step 4: Clonal Expansion - B cells proliferate and differentiate to produce memory calls or large amounts of antibodies to neutralize pathogens

Long Term Versus short term

• P wave- electrical activity associated with atrial depolarization
• QRS wave- electrical activity associated with ventricular depolarization
• T wave- ventricular repolarization