HUMAN NUTRITION AND DIGESTIVE SYSTEM

[Audio] Welcome everyone. Today, we are going to learn about the human nutrition and digestive system. Our unit will focus on how food is broken down and how essential nutrients are absorbed. We will be discussing the structure and functions of the digestive system and the major food groups in a balanced diet. Let's get started..

[Audio] In this presentation, we will be discussing the structure and functions of the human digestive system and how it relates to digestion. We'll also be discussing the process of mechanical and chemical digestion, including the optimum conditions for the enzymes involved. We'll also be detailing the food groups that make up a balanced diet, with examples of their sources. To begin, let's start with the structure and functions of the human digestive system..

[Audio] Digestive system is a complex network of organs and structures with the primary objective of breaking down food into its elementary components and permitting their absorption into the bloodstream. The process of digestion is made up of both mechanical, through mastication, and chemical actions, utilizing enzymes and water. As well as receiving nutrients, the digestive system is also responsible for expelling undigested and unused waste from the body. In summary, the digestive system is a primary factor in the body's capability to receive nourishment and eliminate waste..

[Audio] Structure of the digestive system is a complex process of breakdown and absorption of the food we consume. G I tract, consisting of various organs, begins in the mouth and ends at the anus and has a length of up to 30 meters in adults. Organs work in coordination to pass the food through different stages of digestion from ingestion to defecation. This intricate process is essential for absorbing essential nutrients from our food..

[Audio] The digestive system is made up of several parts working together to break down and process food. In the mouth, food is chewed and mixed with saliva containing an enzyme called amylase to start digestion. It then heads to the oropharynx, followed by the oesophagus, controlled by constrictor muscles. Through peristalsis, the rhythmic wave-like contractions of muscles, the food is propelled further down the oesophagus and to the stomach..

[Audio] Starting from the top left, the mouth mechanically breaks down food through chewing and the application of saliva. This is followed by the esophagus which transports the food from the mouth to the stomach. The stomach stores the food and initiates chemical digestion. The small intestine is the primary site for nutrient absorption while the large intestine is responsible for absorbing water and producing feces. Lastly, the rectum stores the feces until it exits the body..

[Audio] In the digestive system, the stomach receives food boluses and churns them with the help of hydrochloric acid, forming chime, a thick semi-fluid mass. Chyme mixes with gastric juices and enzymes for further digestion. Pepsin is a protein-degrading enzyme responsible for the breakdown of proteins into smaller peptides and the eventual absorbable amino acids. The digested food is then transferred to the duodenum and ileum, the two sections of the small intestine. In the duodenum, bile and pancreatic juices meet to combine with chyme and aid the final stages of digestion. Bile produced by the liver contains bile salts, cholesterol, bilirubin, water and body salts and helps breakdown fats into fatty acids and triglycerol. From the duodenum, the semi-fluid contents leave the small intestine into the colon in liquid form, and nutrients are absorbed into the bloodstream through the villi..

[Audio] The large intestines, often referred to as the colon, is a muscular tube of about 1.5 metres in length with the primary role of absorbing water and salts from chyme. It is made up of the cecum, ascending, transverse, descending, and sigmoid colon, rectum and anus. This tube is instrumental in finishing digestion and absorption of nutrients, with the remaining material stored in the sigmoid colon and rectum until it is ready for excretion through the anal canal. The anal sphincter, a muscular ring, maintains the anus closed until it is triggered by our parasympathetic nervous system for bowel movements..

[Audio] Small and large intestines are main components of the digestive system. Small intestine, the longest part of the digestive tract, absorbs majority of the nutrients from food and is divided into three sections, duodenum, jejunum, and ileum. Large intestine is the last part of the digestive tract and responsible for the absorption of water from the wastes and the formation of feces..

[Audio] Mastication, the process of chewing food, starts mechanical digestion in the oral cavity. Enzymes like amylase break down the bonds between particles to form boluses. Peristalsis then propels the boluses through the digestive system via the involuntary contractions of the oesophageal, stomach, and intestinal muscles. This combination of processes is what allows us to consume and digest food in the gastrointestinal tract..

[Audio] The process of chemical digestion is essential for the breakdown of food particles so that they can be absorbed into the bloodstream. In the mouth, saliva is produced and contains the enzymes lipase and amylase which break down starch and fat respectively. In the stomach, the enzyme pepsin further breaks down proteins while gastric lipase breaks down triglycerides. The small intestine is where a majority of the chemical digestion processes take place, with many digestive enzymes being secreted here. For example, lactase and sucrose digest lactose and sucrose into absorbable sugars. This essential process of chemical digestion ensures that the body receives the nutrients it needs for proper functioning..

[Audio] Mastication, the ripping, tearing, and chewing of food, is the first step in mechanical digestion. After forming a bolus, amylase, a digestive enzyme, turns starch into sugars. Pepsin, another enzyme, is an important part of the digestive process that takes place in the stomach and jejunum and ileum. The large intestine is where the final stages of digestion occur, divided into the cecum and colon. Chemical digestion is the other critical process that takes place in the human digestive system..

[Audio] Enzymes are specialized proteins that speed up the chemical reactions necessary to break down the food we eat into the nutrients our bodies need and are essential to our digestion. There are three main types of enzymes - lipases, amylases, and proteases - that target specific nutrients. For enzymes to function effectively, they need to be at our body temperature and in a particular pH balance depending on where they are located in the body. Temperature and pH changes can affect the enzyme's structure and function, leading to an impaired metabolism. Enzymes have active sites on which chemical reactions occur. These sites are specific in shape and only certain molecules can fit them. When the reactions are complete, the products leave the active sites and the enzyme is ready for another reaction..

[Audio] Pepsin and Lactase are both essential enzymes for the digestive system. Pepsin is released in the stomach and works to break down proteins as well as fight off harmful microorganisms. It also separates vitamin B12 from proteins. Lactase is found in the small intestine and is responsible for breaking down lactose, a sugar found in dairy products. Those who are lactose intolerant produce too little lactase, leaving the sugar unable to be properly broken down. The optimal pH for pepsin is around 2, while lactase works best in a pH range between 2-7, with 6 being ideal..

[Audio] A healthy lifestyle requires a balanced diet. This diet should include from all five food groups, and the daily recommended intake of calories should be taken into account. Fruits and vegetables are packed with vitamins and minerals necessary for supporting the immune system and metabolism. Carbohydrates like cereals, potatoes and pasta are important for cellular respiration and energy production. Fiber from vegetables, fruits, and whole grains regulates blood sugar and supports regular bowel movements. Not following a balanced diet can lead to diseases, fatigue and weakness. Therefore, it is important to adhere to the dietary guidelines for maintaining a healthy lifestyle..

[Audio] Fats are a key part of a balanced diet, providing energy, vitamins, and minerals like Vitamin E, and aiding healthy bones and teeth. Protein is a must, found in meats, eggs, and fish and important for muscle building, cellular repair, and forming essential elements. Dairy products are a good source of protein, minerals, vitamins, and calcium..

[Audio] A balanced diet is essential for our overall health and wellbeing. Figure 5 shows that a balanced diet should comprise Meat and fish, carbohydrates, fruits and vegetables, dairy, and oils and spreads. Each of these food groups has its own health benefits and combining them creates a balanced mix for a healthier lifestyle..

[Audio] Reference list contains three sources of information about digestive system anatomy, physiology, nutrition, and diet therapy. The first source is an article titled “Digestive System Anatomy and Physiology” by Maria Belleza on Nurseslabs. The second source is a textbook called “Nutrition & Diet Therapy” by Le-Ann DeBruyne and Kathy Pinna. The third source is a book titled “Anatomy Physiology: The Unity of Form and Function” by Kenneth Saladin, Sandra Sullivan, and Charles Gan. All sources provide detailed information on the structure, function, and relevance of the human digestive system..

[Audio] Figures in this slide demonstrate components of the human digestive system, from organs used for mechanical and chemical digestion to food groups needed for a balanced diet. Figure 1 presents the digestive system, specifically the mouth, esophagus, stomach, small intestine, large intestine and rectum. Figure 2 focuses on the small and large intestines, which facilitate absorption and waste removal. Further, Figures 3 and 4 illustrate the mechanical and chemical processes of digestion, with Figure 3 demonstrating how enzymes break down food into smaller particles, and Figure 4 displaying muscles in the mouth, stomach and small intestine move food along. Finally, Figure 5 symbolizes a balanced diet of proteins, carbohydrates, fats, vitamins and minerals - essential for digestion. Attention is appreciated..