Human Body Systems: Nutrition and Respiration

Posted on Mar 11, 2025 in Biology

Devices Involved in Nutrition

The following systems are involved in human nutrition:

  • Digestive system: Digests food and converts it into simpler substances.
  • Respiratory system: Provides for the exchange of gases, providing O2 and clearing CO2.
  • Circulatory system: Transports oxygen and usable food substances to different cells through the blood.
  • Excretory system: Eliminates waste substances from the blood.

Digestive System

The digestive system includes:

  • Intestinal tract: Made up of the mouth, esophagus, stomach, small intestine, and large intestine.
  • Digestive glands: Salivary glands, liver, and pancreas.

Digestive Functions

  • Ingestion: Commencement of food in the digestive tract through the mouth.
  • Digestion: Transformation of food into nutrients. There are two types:
    • Mechanical: Physical changes in food, caused by crushing and cutting.
    • Chemical: Food processing where nutrients pass through the gut wall to be transported by blood vessels.
  • Egestion: Elimination of undigested substances, usable or not, from food.

Diseases of the Digestive System

  • Caries: Infectious disease produced by bacteria that affects the hard tissues of the tooth.
  • Constipation: A disorder characterized by difficult evacuation of feces.
  • Ulcers: Open wounds on the inner walls of the digestive tract.
  • Gastroenteritis: Inflammation of the membranes lining the stomach and intestine.
  • Liver cirrhosis: A chronic disease characterized by progressive death of liver tissue.

Respiratory System

The respiratory system is responsible for taking the oxygen carried in the blood and eliminating carbon dioxide. It is formed by the lungs and respiratory passages: nostrils, pharynx, larynx, trachea, bronchi, bronchioles, and pulmonary alveoli.

Gas Exchange

Gas exchange occurs in the pulmonary alveoli. Process:

  1. Air enters through the nostrils.
  2. Air continues through the pharynx and larynx to the trachea.
  3. Air passes from the trachea to the bronchi, and then to the bronchioles, terminating in the alveoli.

This exchange takes place through the thin membranes of the capillaries and alveoli, by diffusion.

Diffusion: Passage of substances through the membrane of cells from a highly concentrated area to a less concentrated one.

Pulmonary Ventilation

Pulmonary ventilation is the process by which atmospheric air enters the lungs and then leaves. Two main muscles act during this process:

  • Diaphragm: Moving up or down, it varies the capacity of the ribcage, enabling breathing movements.
  • Intercostal muscles: These bind the ribs. By contracting and relaxing, they move the ribs and vary the volume of the lungs.

Inspiration and Expiration

Pulmonary ventilation is achieved by two movements:

  • Inspiration: Entry of air into the lungs.
  • Expiration: Air outlet to the outside.

Respiratory Diseases

  • Bronchitis: Inflammatory disease of the bronchi due to bacterial infection, causing breathing difficulties.
  • Asthma: Temporary narrowing of the airways, causing an oxygen deficit in the tissues and hindering respiration.
  • Tuberculosis: Infectious disease produced by bacteria that destroys lung tissue.
  • Cold and flu: Highly contagious respiratory infections caused by viruses.