Understanding Digestion and Respiration

Understanding Digestion

What is Digestion?

Digestion is the process by which food is transformed into simpler substances (nutrients) so they can be used by our cells. It involves two main processes:

• Mechanical Process: Chewing and the muscular action of organs crush and mix foods with digestive juices.
• Chemical Process: Digestive enzymes in digestive juices cause chemical reactions that break food into simple substances.

Mechanical vs. Chemical Digestion

The digestive system employs both mechanical and chemical digestion:

• Mechanical: Mouth
• Chemical: Stomach, liver, small and large intestine

Swallowing: The Process

Swallowing allows substances to pass from the mouth to the pharynx. It involves three main stages:

1. The bolus is moved to the oral cavity as the tongue pushes against the palate.
2. Reflexes cause the palate to close the nasal passage, the larynx to rise, and the epiglottis to close its upper opening. The bolus enters the pharynx.
3. Another reflex helps the bolus pass into the esophagus.

Peristaltic Movements

Peristaltic movement is the contraction of muscle layers in the walls of the esophagus, moving the bolus downward.

It is important because it enables the bolus to move to the esophagus, where it takes place.

Digestion in the Stomach

The bolus enters the stomach, and its muscles contract and mix it with gastric juices.

Pepsin, an enzyme, starts protein digestion, breaking proteins down into smaller fragments called peptides.

Hydrochloric acid has two functions:

• Activates pepsin enzymes and aids in the disintegration of food fibers.
• Destroys bacteria in food.

After mixing with gastric juices, food transforms into chyme. The stomach's muscular layers mix the chyme. When the chyme reaches a high level of acidity, the pylorus opens, and the chyme enters the small intestine.

Digestion in the Small Intestine

Chyme travels from the stomach to the small intestine. Here, it mixes with digestive secretions from the small intestine, pancreas, and liver.

Absorption of Nutrients

Absorption is the passage of nutrients into our blood, allowing them to be distributed throughout the body.

The Large Intestine

The main parts of the large intestine include:

• Cecum: Absorbs fluids and salts remaining after intestinal digestion and mixes its contents with mucus.
• Colon: Symbiotic bacteria of the intestinal flora develop here.
• Rectum: Indigestible food ingredients are decomposed by anaerobic bacteria.

Understanding the Respiratory System

Gas Exchange Explained

Gas exchange is the exchange between the air in the environment and the blood in the organism.

It happens in the pulmonary alveoli, which are connected to the venules. These are connected to the bronchioles at the end of the bronchus, making up the lungs.

Pulmonary Ventilation

Pulmonary ventilation is the exchange of air inside the lungs with the air in the environment.

Processes Involved in Pulmonary Ventilation

Pulmonary ventilation involves two processes:

• Inspiration: Air enters the lungs, the ribcage increases in volume, and the diaphragm contracts, flattens, and lowers itself.
• Expiration: Air exits the lungs, the ribcage decreases in volume, and the diaphragm relaxes, flattens, and lowers itself.