Chapter 19: Blood Vessels and Circulation

Overview of Blood Vessels

The cardiovascular system consists of arteries, veins, and capillaries, each with distinct structural and functional properties. Understanding their differences is essential for grasping blood flow dynamics and systemic circulation.

• Arteries: Thick-walled vessels that carry blood away from the heart; high in elastic and smooth muscle tissue.

• Veins: Thinner walls, less elastic tissue, and often contain valves to prevent backflow; carry blood toward the heart.

• Capillaries: Microscopic vessels where exchange of gases, nutrients, and wastes occurs.

Example: The aorta is the largest artery, while the vena cava is the largest vein.

Peripheral Resistance and Blood Pressure

Peripheral resistance is the opposition to blood flow due to friction between blood and vessel walls. It is influenced by vessel length, diameter, blood viscosity, and turbulence.

• Key Equation:

• Vasoconstriction increases resistance; vasodilation decreases resistance.

• Polycythemia (high RBC count) increases viscosity and resistance.

Additional info: Turbulence is often caused by irregular surfaces or sudden changes in vessel diameter.

Blood Flow Regulation

Blood flow is regulated by neural, hormonal, and local mechanisms. Changes in blood volume, pressure, and vessel diameter affect flow rates.

• Increased muscular activity and sympathetic stimulation raise blood pressure.

• Valves in veins help maintain unidirectional flow, especially in limbs.

Capillary Exchange and Function

Capillaries are specialized for exchange due to their thin walls and large surface area. Capillary beds are regulated by precapillary sphincters.

• Exchange occurs via diffusion, filtration, and osmosis.

• Capillary structure: single layer of endothelial cells.

Major Arteries and Veins

Understanding the branching and naming of major vessels is crucial for tracing blood flow.

Additional info: The matching of arteries and their branches is essential for anatomical orientation.

Chapter 20: The Lymphatic System and Immunity

Innate and Adaptive Immunity

The immune system protects the body from pathogens through innate (nonspecific) and adaptive (specific) defenses.

• Innate defenses: Physical barriers, phagocytes, inflammation, complement, lysozyme.

• Adaptive immunity: Involves lymphocytes (B cells and T cells) and the production of antibodies.

Example: Lysozyme is an enzyme found in tears and saliva that destroys bacterial cell walls.

Cells of the Immune System

Different cell types play specialized roles in immunity.

• Phagocytes: Engulf and digest pathogens.

• B cells: Produce antibodies (humoral immunity).

• T cells: Include helper, cytotoxic, and regulatory subtypes; involved in cell-mediated immunity.

• Natural killer (NK) cells: Destroy infected or cancerous cells.

Antibodies and Antigen Recognition

Antibodies are proteins produced by B cells that bind to specific antigens.

• Major classes: IgA, IgD, IgE, IgG, IgM.

• Antigen-presenting cells (APCs) display antigens to T cells to initiate immune responses.

Immune Responses and Disorders

Immune responses can be classified as humoral or cell-mediated. Disorders include autoimmune diseases and hypersensitivity reactions.

• Complement system promotes cell lysis and inflammation.

• Autoimmune disorders occur when the immune system attacks self-tissues.

Matching Immune Cells

Additional info: Perforins are proteins that create pores in target cell membranes, leading to cell death.

Chapter 21: The Respiratory System

Respiratory Anatomy and Physiology

The respiratory system enables gas exchange between the atmosphere and blood. It includes the lungs, airways, and associated muscles.

• Alveoli: Tiny air sacs where gas exchange occurs.

• Surfactant: Substance that reduces surface tension in alveoli, preventing collapse.

• Epiglottis: Prevents food from entering the airway during swallowing.

Mechanics of Breathing

Breathing involves inspiration and expiration, driven by changes in thoracic volume and pressure.

• Inspiration: Diaphragm contracts, thoracic cavity expands, air flows in.

• Expiration: Diaphragm relaxes, thoracic cavity contracts, air flows out.

• Key Equation: , where is the pressure gradient and is resistance.

Control of Respiration

Respiratory centers in the medulla and pons regulate breathing rate and depth.

• Central chemoreceptors respond to CO2 and pH changes.

• Peripheral chemoreceptors respond to O2 levels.

Gas Exchange and Transport

Oxygen and carbon dioxide are exchanged across the alveolar membrane and transported in blood.

• Oxygen binds to hemoglobin in red blood cells.

• CO2 is transported as bicarbonate, dissolved gas, or bound to hemoglobin.

• Key Equation:

Respiratory Disorders and Age-Related Changes

Disorders such as pneumothorax, emphysema, and asthma affect respiratory function. Aging leads to decreased elasticity and efficiency.

• Pneumothorax: Air enters pleural cavity, causing lung collapse.

• Surfactant deficiency can lead to alveolar collapse.

• Aging reduces vital capacity and gas exchange efficiency.

Example: Only one lung collapses in pneumothorax because the pleural cavities are separate.

Additional Info

• Blood pressure is typically measured in mmHg; normal adult value is around 120/80 mmHg.

• Primary immune response is slower than secondary due to memory cell activation.

• Expiration is usually passive, but can be active during forced breathing.