Comprehensive Study Guide on Cellular Structures and Blood Circulation

Cellular Structure and Function

  • Cytoskeletal Proteins
    • Definition: Cytoskeletal proteins are a variety of different proteins that maintain the shape of the cell.
    • Functions: These proteins provide structural support for cells, influencing their shape.
    • Types of Cells:
    • Mammalian Cells: Characterized by a plasma membrane and cytoskeleton.
    • Plant Cells: Contain a cell wall which provides structure, unlike mammalian cells that rely on the cytoskeleton.

Blood Vessel Structure and Function

  • Types of Blood Vessels

    • Arteries: Carry blood away from the heart.
    • Veins: Bring blood back to the heart.
    • Capillaries: Sites for exchange of nutrients, metabolic waste, and gases.
    • Capillaries are the smallest blood vessels and facilitate the transfer between blood and tissues.

  • Portal Systems

    • Definition: Portal systems are vascular systems where blood passes through two capillary beds before returning to the heart.
    • Example:
    • Hepatic Portal System: Involves the digestive system.
    • Specificity of portal systems will be discussed in relation to the endocrine and digestive systems.

Types of Capillaries

  • Continuous Capillaries

    • Characteristics: Most common, least permeable capillary type.
    • Structure: Few openings, cells form tight spaces with overhanging clefts.
    • Function: Allow for the selective passage of small molecules (e.g., water, gases, hormones).
    • Location: Found in most tissues due to their structural integrity preventing leakage of larger particles such as red and white blood cells.

  • Fenestrated Capillaries

    • Characteristics: Intermediate permeability.
    • Structure: Numerous pores (fenestrations) that act like windows.
    • Function: Facilitate rapid movement of small molecules (gas, nutrients, hormones).
    • Location: Common in the digestive system and kidneys where rapid exchange is crucial.

  • Sinusoid Capillaries

    • Characteristics: Most permeable capillary type, with large openings.
    • Structure: Incomplete or discontinuous, allowing cells to pass through.
    • Function: Facilitates the movement of large proteins and cells, important for tissue functions in detoxification and blood cell production.
    • Location: Present in bone marrow, liver, and spleen.

Heart Structure

  • Chambers of the Heart

    • Atria (2)
    • Function: Receive blood; are thin-walled and located at the upper part of the heart.
    • Ventricles (2)
    • Function: Pump blood; more muscular than atria.
    • Right Ventricle: Pumps blood to the pulmonary circuit (lungs).
    • Left Ventricle: Pumps blood to the systemic circuit (the rest of the body).

  • Volume Consistency

    • Both ventricles hold the same volume of blood although they exert different pressure due to muscular differences.

Blood Flow Dynamics

  • Blood flow sequence from the right atrium to the right ventricle to the lungs and from the left atrium to the left ventricle to the body.

  • Atrioventricular Valves

    • Located between the atria and ventricles (Tricuspid and Bicuspid valves).
    • Function: Prevent backflow of blood into the atria during ventricular contraction.
    • Chords of tendonate: Structure that attaches the valves to the ventricular wall.

  • Semilunar Valves

    • Located between ventricles and arteries.
    • Function: Prevent blood from returning to the ventricles during diastole (relaxation phase) after ejection.

Cardiac Muscle Function

  • Cardiomyocytes: Heart muscle cells responsible for pumping activity.

    • Contractile Cardiomyocytes
    • Make up 99% of cardiac cells.
    • Function: Responsible for the contraction of the heart muscle.
    • Autorhythmic Cardiomyocytes
    • Make up 1% of cardiac cells.
    • Role: Pacemaker cells that regulate heart rhythm and contraction frequency.

  • Action Potential

    • Definition: Electrical signals that prompt myocardial contractions.
    • Characteristics: Include phases such as depolarization, repolarization, and the refractory period (especially absolute refractory period): prolonged time during which the heart muscle cannot contract again.

Intrinsic Conduction System

  • Sinoatrial Node (SA Node)

    • Known as the heart's pacemaker, located in the right atrium.
    • Initiates electrical impulses causing atrial contraction.

  • Atrioventricular Node (AV Node)

    • Receives signals from the atria, directing them into the ventricles.
    • Provides insulation preventing direct impulse transfer from atria to ventricles without going through AV node.

  • Bundle of His and Bundle Branches

    • Encapsulates pathways that transmit electrical signals from the AV node down to the ventricles.

  • Purkinje Fibers

    • Final pathway for conduction within the ventricular walls, ensuring the muscle contracts efficiently to pump blood.

  • Diagrammatic representation of the intrinsic conduction system is crucial to visualize the flow of electrical impulses for heart contractions.