Anatomy and Physiology of the Heart, Nasal Cavity, and Respiratory System

Posted on May 9, 2024 in Biology

Cardiac Skeleton

The cardiac skeleton is a dense connective tissue structure that supports the attachment of muscular fibers in the atria and ventricles, as well as the bicuspid and tricuspid valves. It consists of fibrous rings surrounding the atrioventricular and arterial orifices, connected by tendons. The right and left atrioventricular orifices support the tricuspid and mitral valves, respectively, ensuring one-way blood flow from atria to ventricles. Arterial orifices, including pulmonary and aortic orifices, support the pulmonary and aortic valves, allowing blood to exit the ventricles and preventing backflow. Heart valves maintain the proper direction of blood flow.

Blood Supply to the Heart

Major Coronary Branches:

  • Right Coronary Artery:
    • Right marginal branch: Supplies the right ventricle walls.
    • Posterior interventricular branch: Supplies the posterior interventricular septum.
    • Sinoatrial branch: Supplies the right atrium and sinoatrial node.
  • Left Coronary Artery:
    • Anterior interventricular branch: Supplies the interventricular septum.
    • Circumflex branch: Supplies the left ventricle walls.

Basic Physiological Parameters:

  • Heart rate (HR): Number of heartbeats per minute.
  • Stroke volume (SV): Volume of blood pumped per beat.
  • Cardiac output (Q): Volume of blood pumped per minute (Q = HR x SV).

Nerve Supply

The autonomic nervous system controls the heart’s motor functions through the cardiac plexus, which receives input from sympathetic and vagus nerves. The glossopharyngeal and vagus nerves convey sensory information from pressure receptors. Pain sensations from the pericardium are relayed by the glossopharyngeal, vagus, and phrenic nerves.

Autonomic Motor Supply:

  • Sympathetic nerves: Increase heart rate and contraction strength, leading to increased cardiac output and vasodilation of coronary arteries.
  • Vagus nerve: Innervates the nodes and has opposite effects to sympathetic nerves.

Sympathetic and Parasympathetic Effects:

Sympathetic Activity:

  • Increases heart rate and stroke volume, leading to increased cardiac output.
  • Accelerates blood circulation and oxygen uptake.

Parasympathetic Activity:

  • Decreases heart rate and stroke volume.

Nasal Cavity

Components:

  • Vestibule: Filters large particles with vibrissae.
  • Nasal cavity proper: Contains conchae and meati, lined with ciliated pseudostratified columnar epithelium that filters, heats, and humidifies air.
  • Nasal septum: Divides the nasal cavity.
  • Choanae: Openings leading to the pharynx.

Epithelia:

  • Vestibule: Stratified squamous keratinized epithelium.
  • Lateral and septal walls and floor: Ciliated pseudostratified columnar epithelium with goblet cells producing mucus.
  • Roof: Olfactory epithelium with olfactory receptor cells.

Paranasal Sinuses:

  • Air-filled spaces within skull bones.
  • Communicate with the nasal cavity.
  • Functions: Resonance of voice, humidifying and heating inhaled air.

Respiratory System

Blood Supply

The respiratory portion of the lungs receives deoxygenated blood from the pulmonary artery and returns oxygenated blood to the heart via the pulmonary vein. The conducting portion receives oxygenated blood from the bronchial arteries and returns deoxygenated blood via the bronchial veins.

Nerve Supply to Lungs

The lungs are innervated by the anterior and posterior pulmonary plexuses, formed by branches from the sympathetic and vagus nerves. These nerves relay autonomic motor commands and sensory information.

Effects of the Autonomic System on Lung Function:

Parasympathetic (Vagus Nerve):

  • Respiratory portion: Vasoconstriction.
  • Conducting portion: Vasodilatation, bronchial constriction, increased glandular secretion.

Sympathetic (Spinal Nerves):

  • Respiratory portion: Vasodilatation.
  • Conducting portion: Vasoconstriction, bronchial dilatation, decreased glandular secretion.

Sensory Supply:

The vagus nerve conveys sensory information from pulmonary stretch receptors, mechanoreceptors, and the visceral pleura. Spinal nerves and the phrenic nerve relay sensory information from the parietal pleura.