Human Circulatory and Respiratory Systems: Functions & Anatomy

Posted on Feb 24, 2025 in Biology

The Circulatory System

The circulatory system is responsible for transporting substances throughout the body. It consists of:

  • A pump (the heart)
  • A liquid (blood)
  • A series of ducts (blood vessels)

The heart pumps blood throughout the body, delivering oxygen and nutrients to cells while collecting tissue debris and carbon dioxide.

Composition of Blood

Blood consists of:

  • Plasma: A thick, yellowish liquid primarily composed of water and other substances.
  • Blood cells:
    • Red blood cells: Cells that have lost their nucleus and are responsible for oxygen transport.
    • White blood cells (leukocytes): Responsible for defending the body against infections.
    • Platelets (thrombocytes): Help in blood coagulation and stop bleeding.

Other Functions of Blood

Besides transport, blood performs other crucial functions:

  • Distributes body heat.
  • White blood cells defend the body against infections.
  • Platelets coagulate blood in wounds, helping to stop bleeding.

The Respiratory System

The role of the respiratory system is to supply the body with oxygen, enabling cells to “burn” nutrients and release energy. This process produces carbon dioxide as waste, which is then expelled from the body through exhalation.

Organs of the Respiratory System: Anatomy and Function

  • Nose

    The nose has two openings called nares. Inside the nares are cilia, which aid in smelling. The function of the nose is to moisten, heat, and purify inhaled air.

  • Trachea

    Located in the first six cervical vertebrae, the trachea is a common passage for both the digestive and respiratory systems. It directs food from the mouth to the esophagus and air from the nostrils to the larynx.

  • Larynx

    A tube with walls reinforced by cartilage. Inside are the vocal cords, making the larynx the organ responsible for sound production. It moves during phonation, voice modulation, and swallowing.

  • Bronchi

    These are the various branches within the lungs, ending in pulmonary alveoli. These alveoli are surrounded by capillaries, facilitating gas exchange and blood purification.

  • Alveoli

    Small sacs where hematosis occurs, a process in which red blood cells absorb oxygen and release carbon dioxide.

  • Lungs

    Two spongy masses of reddish color, surrounded by the pleura, located in the chest on either side of the heart. The right lung has three lobes, while the left has two. They contain approximately 300 million alveoli.

  • Diaphragm

    A muscle that separates the chest cavity from the abdominal cavity. Its contraction allows air to enter the lungs.