Blood and Cardiovascular System: Structure, Function, and Regulation

Chapter 17: Blood

Components of Whole Blood

Blood is a specialized connective tissue composed of plasma and formed elements. It serves as the transport medium for nutrients, gases, hormones, and waste products throughout the body.

• Plasma: The liquid matrix of blood, mostly water, containing dissolved proteins, nutrients, and waste.

• Formed Elements: Includes erythrocytes (RBCs), leukocytes (WBCs), and platelets.

Key Terms:

• Hematopoiesis: Formation of blood cells.

• Hematocrit: Proportion of blood volume occupied by RBCs.

Physical and Chemical Properties of Blood

• pH: 7.35–7.45 (slightly basic)

• Temperature: ~38°C (higher than body temperature)

• Volume: 5–6 L for males, 4–5 L for females

Blood Functions

• Distribution: Transports oxygen, nutrients, waste, and hormones.

• Regulation: Maintains body temperature, pH, and fluid volume.

• Protection: Prevents blood loss (clotting) and infection (immune cells).

Plasma Composition

• Water: 90% of plasma

• Proteins: Albumin (osmotic balance), globulins (immune function), fibrinogen (clotting)

• Other solutes: Nutrients, electrolytes, gases, hormones

Formed Elements

• Erythrocytes (RBCs): Biconcave discs, lack nuclei, filled with hemoglobin for oxygen transport

• Leukocytes (WBCs): Immune defense

• Platelets: Cell fragments involved in clotting

Hemoglobin Structure and Function

• Structure: 4 polypeptide chains (2 alpha, 2 beta), each with a heme group

• Function: Binds oxygen (as oxyhemoglobin) and carbon dioxide (as carbaminohemoglobin)

Equation:

• $\text{O}_2 + \text{Hemoglobin} \rightarrow \text{Oxyhemoglobin}$

• $\text{CO}_2 + \text{Hemoglobin} \rightarrow \text{Carbaminohemoglobin}$

Red Blood Cell Production (Erythropoiesis)

• Stimulated by: Erythropoietin (EPO) from kidneys in response to low oxygen

• Process: Stem cells in bone marrow differentiate into erythrocytes

• Regulation: Negative feedback based on oxygen levels

Fate and Breakdown of RBCs

• Aged RBCs are engulfed by macrophages in spleen and liver

• Hemoglobin is broken down: heme converted to bilirubin (excreted in bile), iron recycled

Blood Disorders

• Anemia: Decreased RBCs or hemoglobin (causes: hemorrhage, iron deficiency, B12 deficiency, etc.)

• Sickle Cell Disease: Abnormal hemoglobin, confers malaria resistance

• Thalassemias: Missing hemoglobin chains, fragile RBCs

Blood Groups and Transfusion

• ABO System: Based on presence of A and B antigens on RBCs

• Rh Factor: Presence of D antigen determines Rh+ or Rh- blood type

• Transfusion Reactions: Occur if incompatible blood is transfused

Blood Type	Antigen(s)	Antibody(ies)
A	A	Anti-B
B	B	Anti-A
AB	A, B	None
O	None	Anti-A, Anti-B

Chapter 18: The Cardiovascular System – The Heart

Heart Structure and Function

The heart is a muscular organ that pumps blood through the pulmonary and systemic circuits. It consists of four chambers: two atria and two ventricles.

• Right side: Pumps blood to the lungs (pulmonary circuit)

• Left side: Pumps blood to the body (systemic circuit)

• Valves: Ensure unidirectional blood flow (AV valves, semilunar valves)

Layers of the Heart Wall

• Epicardium: Outer layer

• Myocardium: Middle, muscular layer (cardiac myocytes)

• Endocardium: Inner endothelial layer

Cardiac Muscle Physiology

• Striated muscle: Contains sarcomeres, actin, and myosin

• Intercalated discs: Connect cells, allow electrical coupling

• Autorhythmicity: Cardiac cells can generate action potentials without external stimuli

Heart Valves

• AV Valves: Separate atria from ventricles (tricuspid, bicuspid/mitral)

• Semilunar Valves: Separate ventricles from arteries (pulmonary, aortic)

Cardiac Cycle

• Systole: Contraction phase, blood ejected from ventricles

• Diastole: Relaxation phase, ventricles fill with blood

Key Equations:

• Stroke Volume (SV): $SV = EDV - ESV$

• Ejection Fraction: $\text{Ejection Fraction} = \frac{SV}{EDV} \times 100\%$

• Cardiac Output (CO): $CO = \text{Heart Rate} \times SV$

Electrical Conduction System

• SA Node: Pacemaker, initiates action potentials

• AV Node: Delays impulse, allows atria to contract before ventricles

• Bundle of His, bundle branches, Purkinje fibers: Distribute impulse through ventricles

Electrocardiography (ECG)

• P wave: Atrial depolarization

• QRS complex: Ventricular depolarization

• T wave: Ventricular repolarization

Regulation of Heart Rate

• Autonomic Nervous System: Sympathetic increases HR, parasympathetic decreases HR

• Hormonal Regulation: Epinephrine, norepinephrine increase HR

Chapter 19: The Cardiovascular System – Blood Vessels

Generalized Structure of Blood Vessels

Blood vessels are composed of three layers (tunics):

Layer	Composition	Function
Tunica intima	Endothelium	Lines lumen, reduces friction
Tunica media	Smooth muscle, elastic fibers	Controls diameter, regulates blood flow and pressure
Tunica externa	Collagen fibers	Protects and anchors vessel

Types of Blood Vessels

• Arteries: Carry blood away from the heart; high pressure, thick walls

• Capillaries: Exchange nutrients and waste; thin walls, single cell layer

• Veins: Carry blood toward the heart; low pressure, valves prevent backflow

Blood Vessel Classification

• Elastic (Conducting) Arteries: Largest arteries, near heart, stretch to accommodate pressure fluctuations

• Muscular (Distributing) Arteries: Deliver blood to organs, more smooth muscle

• Arterioles: Smallest arteries, regulate blood flow into capillary beds

• Capillaries: Site of exchange; types include continuous, fenestrated, and sinusoidal

• Veins: Thinner walls, larger lumens, contain valves

Types of Capillaries

Type	Structure	Location
Continuous	Uninterrupted lining	Skin, muscle, blood-brain barrier
Fenestrated	Pores for filtration	Kidneys, intestines, endocrine glands
Sinusoidal	Large gaps, incomplete basement membrane	Liver, bone marrow, spleen

Venous System and Venous Return

• Valves: Prevent backflow of blood

• Varicose veins: Result from valve failure

• Factors aiding venous return: Muscle contraction, breathing, pressure changes

Blood Flow, Pressure, and Resistance

• Blood flow: Volume of blood moving through vessel per unit time

• Blood pressure: Force exerted by blood on vessel wall

• Resistance: Opposition to flow, mainly due to vessel diameter

Poiseuille’s Law:

• $Q = \frac{\Delta P \cdot \pi \cdot r^4}{8 \cdot \eta \cdot l}$

• Where $Q$ = flow, $\Delta P$ = pressure difference, $r$ = radius, $\eta$ = viscosity, $l$ = length

Regulation of Blood Pressure

• Short-term: Neural and hormonal controls (baroreceptors, chemoreceptors, catecholamines)

• Long-term: Renal regulation of blood volume

Summary Table: Blood Vessel Types

Vessel Type	Wall Thickness	Pressure	Valves
Artery	Thick	High	No
Capillary	Very thin	Low	No
Vein	Thin	Low	Yes

Additional info:

• Some context and definitions have been expanded for clarity and completeness.

• Tables have been recreated and summarized for study purposes.