Human Body Systems: Digestive and Respiratory Organs Explained

Digestive System Organs

Esophagus

• Tube approximately 25 cm long.
• Located behind the trachea and in front of the spinal cord.
• Drives the food bolus from the pharynx to the stomach.
• Its muscles produce peristaltic movements to ensure food reaches the stomach.
• Produces mucus, which favors food transit.

Pylorus

• A sphincter that communicates with the small intestine (duodenum).

Shared & Digestive System Components

Pharynx

• A duct located behind the mouth.
• Contains lumps called tonsils.
• Communicates the mouth with:
  • Esophagus
  • Back of the nostrils
  • Larynx
  • Middle ear

Epiglottis

• A flap located in the lower part of the pharynx.
• Closes the entrance to the larynx during swallowing.
• Prevents food from entering the respiratory tract.

Cardia (Cardiac Sphincter)

• A sphincter that connects the esophagus to the stomach.

Respiratory System Organs

Nasal Cavity

Characteristics & Functions:

• Contains abundant capillaries with circulating blood, which heats the inhaled air.
• Features numerous folds (conchae or turbinates) that increase surface area, allowing air more travel time inside.
• Internally covered by a mucous membrane with numerous glands that keep it moist and covered with protective mucus. This membrane purifies and moistens the air.

Lungs

Characteristics:

• Surrounded by the pleura, which is composed of two membranes:
  • Visceral Pleura: Intimately attached to the surface of the lungs.
  • Parietal Pleura: Attached to the thoracic walls.
• Between these two membranes, there is a small pleural cavity filled with fluid that allows:
  • Keeps the two membranes together.
  • Allows them to gently slide one over the other during breathing.

Bronchioles

Characteristics:

• Their branching network is called the bronchial tree.
• They terminate in pulmonary alveoli:
  • Tiny sacs, often described as grape-like clusters.
  • Consisting of a single layer of flattened cells (endothelium).
  • Coated by an abundant network of capillaries that facilitates gas exchange.

Trachea

Respiratory Reflexes

Cough

• Violent and noisy expulsion of air from the lungs.
• Aims to expel any foreign particle present in the airways.

Sneeze

• Violent and noisy expulsion of air from the nose and mouth.
• Caused by an involuntary and sudden movement of the diaphragm.
• Triggered by a stimulus acting on the nasal mucous membrane.