Human Respiratory and Circulatory Systems: Functions and Anatomy

Respiratory System: Anatomy and Functions

The respiratory system facilitates the exchange of oxygen and carbon dioxide in the body. Here’s a breakdown of its key components:

• Vocal Cords: Located inside the larynx, these two ring-shaped folds vibrate to produce sounds as air passes through them.
• Nostrils: The primary entry point for air, the inner walls of the nostrils warm, humidify, and filter the incoming air using mucus.
• Pharynx: Part of the digestive system, the pharynx contains the pharyngeal tonsils on its side walls, which produce white blood cells for immune defense.
• Larynx: The entrance to the larynx is regulated by a fibrous structure called the epiglottis, which closes when food is present in the pharynx, preventing it from entering the airway.
• Trachea: This canal, about 12 cm long, is reinforced with cartilage rings that are open at the back. The inner lining of the trachea contains mucus to trap foreign particles, and cells with vibrating filaments called cilia. These cilia move the mucus, laden with impurities, towards the larynx, where it is then directed to the esophagus and stomach. The body employs coughing and sneezing to expel particles from the airways.
• Bronchi and Bronchioles: The trachea divides into two bronchi, also reinforced with cartilage rings. Each bronchus enters a lung and branches into progressively smaller ducts. The final branches of the bronchioles terminate in tiny sacs called alveoli, where gas exchange occurs.
• Inspiration: This is the respiratory movement through which air enters the lungs. Since the lungs lack their own muscles, inspiration is driven by the contraction of the ribcage muscles and the diaphragm.
• Expiration: This is the movement through which air leaves the lungs. During expiration, the ribs perform the opposite movement of inspiration, and the diaphragm relaxes, curving upwards.

Circulatory System: Anatomy and Functions

The circulatory system transports blood throughout the body, delivering oxygen and nutrients while removing waste products.

Internal Environment

The cells of any living organism are immersed in an environment from which they obtain nutrients and into which they discharge waste substances from metabolic reactions. This environment is called the internal environment and consists of plasma and interstitial fluid found in the spaces between cells.

Blood

Blood is a viscous liquid with a salty taste that circulates inside the ducts of the circulatory system. It is estimated that each human being has about 5.5 liters of blood.

Functions of Blood

• Transports nutrients and oxygen to all cells.
• Collects waste products from cellular metabolism.
• Plays a vital role in the body’s defense mechanisms.
• Participates in the regulation of body temperature.

Blood Plasma

Blood plasma is a yellowish fluid composed of water in which various molecules are dissolved, including mineral salts, nutrients (vitamins, etc.), waste substances (carbon dioxide, urea), proteins, and hormones.

Blood Cells

There are three types of blood cells:

• Red blood cells
• White blood cells
• Platelets

Arteries

Arteries carry blood away from the heart. As they move away from the heart, they branch into smaller vessels that penetrate the tissues and organs, further branching into even finer vessels called arterioles.

Capillaries

Capillaries are microscopic blood vessels that branch from arterioles and are found throughout the body’s tissues. Their walls are formed by a single layer of flat cells, facilitating the easy and rapid exchange of substances between the blood flowing through them and the surrounding cells.