Introduction
The digestive system is a complex part of the human body and It’s responsible for breaking down the food into simpler components so our bodies can absorb nutrients and energy necessary for our survival.
The digestive system also includes vital organs like Esophagus, Stomach, Intestine and associated glands like Liver, Gall bladder and Pancreas.
These organs work in harmony to ensure that our bodies efficiently process and utilize the food we consume.
Main physiological processes of the Digestive system
The digestive system performs several main activities to convert food into nutrients that the body can use. Here’s a brief explanation of each:
#1 Ingestion:
- The process begins with ingestion, where food enters the mouth. This is the first step in the digestive process, involving the intake of food and liquids.
#2 Propulsion:
- After ingestion, propulsion moves the food through the digestive system. It starts with swallowing, which moves food from the mouth into the esophagus.
- Subsequently, a series of rhythmic, wave-like muscle contractions, known as peristalsis, further propels the ingested materials through various sections of the digestive system, including the stomach and intestines.
#3 Mechanical Digestion:
- This involves physically breaking down food into smaller pieces without altering its chemical structure. It begins in the mouth with chewing and continues in the stomach, where food is churned, further breaking it down and mixing it with digestive juices.
#4 Chemical Digestion:
- Chemical digestion involves breaking down food into simpler nutrients that can be absorbed by the body. It starts in the mouth with saliva and continues in the stomach and intestines with the help of enzymes and acids.
- This process converts complex molecules like proteins, fats, and carbohydrates into simpler molecules like amino acids, fatty acids, and sugars.
#5 Absorption:
- The small intestine is the primary site for absorption. Here, nutrients from digested food are absorbed into the bloodstream through the intestinal walls.
- The villi and microvilli, small finger-like projections in the lining of the small intestine, increase the surface area for absorption.
#6 Elimination/Defecation:
- The final step in the digestive process is the elimination of undigested and unabsorbed food substances.
- Waste material moves into the large intestine, where water is absorbed, and the remaining material is formed into feces.
- Defecation then expels the feces from the body through the rectum and anus, completing the digestive process.
Organs of the digestive system:
The digestive system is composed of a series of organs that work together to break down, digest, and absorb nutrients from food, as well as eliminate waste.
Here’s an overview of the major organs involved in the digestive process:
#1 Mouth.
The mouth, or oral cavity, consists of several key components, each with specific anatomical features and functions. Here’s a brief overview of the main components and their anatomy:
1. Lips and Cheeks
Lips: Fleshy structures forming the opening of the mouth. They are highly sensitive and help in detecting the temperature and texture of food.
Cheeks: The sides of the mouth, consisting of muscular walls that help keep food between the teeth during chewing and assist in the formation of speech.
2. Teeth
Humans typically have two sets of teeth in their lifetime: 20 primary (baby) teeth and 32 permanent teeth. Teeth are divided into incisors (for cutting), canines (for tearing), premolars, and molars (for grinding).
Anatomy: Each tooth consists of a crown (the visible part above the gum) and a root (embedded in the jawbone). The hard, outer layer of the crown is enamel, the hardest substance in the human body.
3. Tongue
A muscular organ on the floor of the mouth. It’s covered with moist, pink tissue called mucosa, and tiny bumps called papillae, which contain taste buds.
Anatomy: The tongue is anchored to the mouth by the frenulum underneath and is highly flexible, allowing it to move food, aid in chewing and swallowing, and form words during speech.
4. Palate
Divided into the hard palate at the front and the soft palate at the back.
Hard Palate: A bony plate covered with mucous membrane, forming the roof of the mouth and separating the oral and nasal cavities.
Soft Palate: A muscular extension of the hard palate that moves during swallowing to close off the nasal passages and prevent food from entering the nasal cavity.
5. Uvula
A small, teardrop-shaped piece of soft tissue that hangs down from the soft palate at the back of the mouth. It plays a role in speech and in the gag reflex, and it helps to close off the nasopharynx during swallowing, preventing food from entering the nasal cavity.
6. Gingivae (Gums)
The soft tissue covering the jawbone around the base of the teeth. Gums provide support and protection for the teeth and the underlying bone.
Pharynx
The pharynx, commonly referred to as the throat, is a muscular tube that plays a pivotal role in both the digestive and respiratory systems.
It connects the mouth and nasal cavity to the esophagus (for digestion) and the larynx (for respiration), serving as a common pathway for both food and air.
The anatomy of the pharynx allows it to perform its dual functions effectively, distinguishing between the pathways for digestion and respiration.
The pharynx is divided into 3 regions
1. Nasopharynx:
Located behind the nasal cavity, the nasopharynx is involved in respiration.
It remains open to allow the passage of air from the nasal cavity to the lower respiratory tract. The adenoids, or pharyngeal tonsils, are located in this region and play a role in immune response.
2. Oropharynx:
This section lies behind the oral cavity, extending from the uvula to the level of the hyoid bone. It serves as a passageway for both air and food. The palatine tonsils, which are part of the body’s immune system, are located in the oropharynx.
3. Laryngopharynx (Hypopharynx):
The laryngopharynx is the lowest part of the pharynx, connecting to the esophagus and the larynx. It functions as a pathway for food and drink to enter the esophagus and for air to enter the larynx
Oesophagus
The oesophagus, is a muscular tube that connects the pharynx (throat) to the stomach, playing a crucial role in the digestive system. It serves as the pathway through which swallowed food and liquids travel from the mouth to the stomach.
Anatomy of the Esophagus
Location:
The esophagus starts at the level of the cricoid cartilage (just below the larynx) in the neck and runs down through the thoracic cavity, penetrating the diaphragm, and ending at the stomach.
Length:
It is approximately 25 cm (about 10 inches) long in adults.
Structure:
The esophagus is composed of several layers, including an inner lining (mucosa), a submucosa (containing glands that secrete mucus to moisten the esophagus), a muscular layer (which facilitates the movement of food), and an outer connective tissue layer
Functions
The primary function of the esophagus is to transport food and liquids from the mouth to the stomach
Once food enters the esophagus, rhythmic, wave-like contractions of the muscular layer propel the food downward. These contractions are involuntary and ensure that food moves in the right direction, regardless of the body’s position.