Human Respiratory System: Anatomy and Function

Respiratory System: Nutrients and O2

The respiratory system captures oxygen from the air and transfers it into the blood. Cells use oxygen and nutrients to produce energy. Blood removes carbon dioxide (CO2), which is expelled from the body along with water vapor.

Respiratory system function: Gas exchange with the atmosphere.

Nasal Cavity

The nasal cavity is divided into two chambers. Each chamber has an external opening (nostril) and an internal opening to the pharynx (choana). A partition called the nasal septum separates the chambers. The nasal cavity is the entry point for air.

Characteristics

• Abundant capillaries with circulating blood.
• Abundant nooks that allow the air to travel further and remain inside longer, heating the air.
• Internally covered by a membrane called the pituitary, with numerous glands that keep it moist and covered with protective mucus.
• Purifies and moistens the air.

Choanae

Openings that allow the passage of air from the nostrils to the pharynx.

Pharynx

Definition: A tube belonging to two systems:

• Digestive: Communicates with the esophagus.
• Respiratory: Communicates with the larynx.

It is also connected to the ear via the Eustachian tube.

Characteristics

The tonsils are found on the side walls. They produce white blood cells that protect us from infections.

Epiglottis

A cartilaginous fold regulating the passage of substances.

Larynx

Definition: A short tube whose walls are constituted by cartilages joined by connective tissue.

Characteristics

It is the body part in charge of phonation. The side walls have four folds of tissue called vocal cords. They vibrate with the passage of air, emitting sounds that are modulated with the tongue, lips, teeth, and nose.

Trachea

Definition: A tube that runs through the neck in front of the esophagus.

Characteristics

• Approximate length: 12 cm.
• Formed by cartilage rings open on the back.
• Interior lining: Epithelial tissue layer with:
  • Goblet cells: Secrete mucus that moistens and protects the tracheal mucosa.
  • Ciliated cells: Cilia are filaments that vibrate. As they move, they move the mucus and expel possible foreign bodies (trachea > larynx > pharynx > esophagus > stomach).

Expulsion Mechanisms

• Cough: Violent and noisy expulsion of the air contained in the lungs, dragging any foreign particle that is in them.
• Sneeze: Violent and noisy expulsion from the nose and mouth of the air in the lungs by an involuntary and sudden movement of the diaphragm. Sneezing is caused by some stimulus acting on the pituitary membrane.

Bronchi

Two branches into which the trachea is divided.

Characteristics

• Formed by cartilage rings.
• Each one leads to a lung.
• The bronchi split into gradually narrower tubes inside the lungs called bronchioles.

Bronchioles

Definition: Smaller and smaller branches until they become thin tubes.

Characteristics

• The set is called the bronchial tree (due to its shape).
• They end in the pulmonary alveoli (tiny sacs with a blackberry shape, consisting of a layer of flattened cells called the endothelium).
• Coated by an abundant network of capillaries that facilitates gas exchange.

Lungs

Definition: Two organs of great elasticity (sponge-like) formed by bronchi, bronchioles, the bronchial tree, pulmonary alveoli, and a capillary network.

Characteristics

• Left lung: Formed by two lobes separated by one segment.
• Right lung: Three lobes separated by two segments.
• Located in the thoracic cavity, protected by the ribs.
• Separated from the abdomen by the diaphragm (a dome-shaped muscle).

Surrounded by the pleura, composed of two membranes:

• Visceral: Intimately attached to the surface of the lung.
• Parietal: Attached to the thorax walls.

Between them, there is a small cavity (pleural cavity) filled with liquid that:

• Keeps the two membranes together.
• Allows them to gently slide over each other.