Biology 30SDigestion and Nutrition

Unit 3Unit Outcomes:

Identify major structures and functions of the human digestive system from a diagram, model, or specimen.

Describe the processes of mechanical digestion that take place at various sites along the alimentary canal.

Identify functions of secretions along the digestive tract. Identify sites of chemical digestion along the alimentary canal, as well as the type of

nutrient being digested. Explain the role of enzymes in the chemical digestion of nutrients and identify factors

that influence their action. Describe the processes of absorption that take place at various sites along the

alimentary canal. Describe the homeostatic role of the liver with respect to the regulation of nutrient

levels in the blood and nutrient storage. Identify dietary sources for each of the six basic types of nutrients— carbohydrates,

lipids, proteins, vitamins, minerals, and water. Evaluate personal food intake and related food decisions. Investigate and describe conditions/disorders that affect the digestive process. Use the decision-making process to investigate an issue related

to digestion and nutrition.

Introduction – The Process of Digestion

Digestionhttps://www.youtube.com/watch?v=Og5xAdC8EUI

A basic definition for Digestion is: the process of changing food into a form that the cells in our body can use.

The above definition is a very simple one. Digestion is a complex process involving specialized anatomical and physiological adaptations for the absorption of nutrients.

The purpose of digestion is to prepare food and make it usable for the cells and organs throughout the body. Because large food particles cannot reach cells, the process of digestion breaks the food down into nutrients that can be absorbed into the blood stream and carried to any cell in the body.

The methods of digestion are mechanical and chemical. Each segment of the digestive system has a special design in order to perform a unique function that is an essential part of the digestive process.

Digestion begins in the mouth and is completed at the anus. As food moves through the digestive tract, it passes through several compartments.

Accessory organs that produce digestive enzymes drain their contents into the main compartments at different points along the way. Each compartment and accessory organ serves a specific function.

At each stage, the food is transformed into a slightly different form that allows it to be passed along to the next compartment. As it moves through the digestive tract, nutrients and water are extracted, producing waste. The waste products are eventually eliminated.

Nutrition

Nutrition is the process by which organisms obtain and utilize their food. There are four stages of food processing, they are as follows:

1. Ingestion – the act of eating food or drinking. Food first enters our bodies through our mouths.

2. Digestion – breaking food down into smaller pieces (mechanical digestion) or smaller molecules (chemical digestion).

3. Absorption – the uptake of small nutrient molecules into the body to aid cells in growth and maintenance.

4. Elimination – the passage of undigested waste from the body. Riding the body of whatever is left over after the body takes what it needs.

Nutrients

There are two categories of nutrients:A) MicronutrientsB) Macronutrients

A. Macronutrients (proteins, lipids, carbohydrates)

Macronutrients are considered the classes of chemical compounds humans consume in the largest quantities and which provide bulk energy.

Carbohydrates

Carbohydrates are our bodies’ preferred source of energy, so this macronutrient should make up a lot of our diet.

Breads, rice, pasta, oats, quinoa, couscous Starchy vegetables (potatoes, corn and pumpkin) All other vegetables (broccoli, lettuce, tomato, carrot, peas) Beans and pulses (chickpeas, baked beans, lentils) Some dairy foods such as milk and yoghurt Fruit Sugar and honey

Protein

Protein is mostly used in our body to build and repair muscle and tissue, but has many other important functions as well.

Meat and meat products (beef, chicken, lamb, pork or kangaroo) Fish and seafood Eggs Dairy food such as milk and yoghurt (also carbohydrate) Beans and pulses (also carbohydrates) Nuts (also fats) Soy and tofu products

Fat

Fats have been given a bad name, but they too are an important part of our diet. They’re used by the body as energy, storage for vitamins, for production of hormones and as protection for our organs.

There are different types of fats:

SaturatedThese should be limited, but not necessarily avoided. If eaten in large amounts they can be bad for your heart health. They are found in:

Meat fat Butter Full fat dairy products Coconut oil and products Peanut oil, palm oil and cottonseed oil Our occasional foods such as chips, biscuits and cake

Swapping to reduced-fat dairy, and trimming the fat off your meat before cooking it are good ways to reduce your saturated fat intake.

UnsaturatedWe should aim to include more of these fats in our diet, as they have the opposite effect to saturated fats, and can be beneficial for your heart health. They are found in:

Fish Nuts Avocados Vegetable oils (olive, canola, sunflower, rice bran)

B. Micronutrients (vitamins, minerals, & water)

Micronutrients are nutrients required by humans and other organisms throughout life in small quantities to conduct a wide range of physiological functions. For people, they include minerals in amounts generally less than 100 milligrams per day.

Micro minerals or trace elements include: o iron,cobalt, chromium, copper, iodine, manganese,

seleneium, zinc and molybdenum.

Micronutrients also include vitamins, which are organic compounds required as nutrients in tiny amounts by an organism.

Vitamins and minerals make people's bodies work properly. Although you get vitamins and minerals from the foods you eat every day, some foods have more vitamins and minerals than others.

Vitamins fall into two categories:

fat soluble and water soluble.

The fat-soluble vitamins A, D, E, and K Dissolve in fat and can be stored in your body

The water-soluble vitamins C and the B-complex vitamins (such as vitamins B6, B12, niacin,

riboflavin, and folate) Need to dissolve in water before your body can absorb them Your body can't store these vitamins Any vitamin C or B that your body doesn't use is lost (mostly when

you pee)

Whereas vitamins are organic substances (made by plants or animals), minerals are inorganic elements that come from the soil and water and are absorbed by plants or eaten by animals. Your body needs larger amounts of some minerals, such as calcium, to grow and stay healthy. Other minerals like chromium, copper, iodine, iron, selenium, and zinc are called trace minerals because you only need very small amounts of them each day.

Common Concerns about Vitamins and Minerals

Lots of teens wonder if they should take vitamin or mineral supplements. If your diet includes a wide variety of foods, including whole-grain products, fresh fruits and vegetables, dairy products, nuts, seeds, eggs, and meats, then you are probably getting the vitamins and minerals your body needs.

If you're skipping meals, dieting, or if you're concerned that you're not eating enough items from a particular category, such as vegetables or dairy products, then talk to your doctor or to a registered dietitian. These professionals can help you create an eating plan that includes the nutrients your body needs.

Check with your doctor before taking vitamin or mineral supplements. Some people think that if something is good for you, then the more you take in, the healthier you'll be. But that's not necessarily true when it comes to vitamins and minerals. For example, fat-soluble vitamins or minerals, which the body stores and excretes more slowly, can build up in your system to levels where they could cause problems.

Your best bet for getting the vitamins and minerals you need is to eat a wide variety of healthy foods and skip the vitamin pills, drinks, and other supplements. You'll feel better overall and won't run the risk of overdoing your vitamin and mineral intake.

Be aware of the following terms when trying to understand how much of a vitamin or mineral to take…

RDA (Recommended Dietary Allowance) and the AI (Adequate Intake) are the amounts of a vitamin or mineral you need to stay healthy and avoid nutritional deficiencies. They are tailored to women, men, and specific age groups.

UL (Tolerable Upper Intake Level) is the maximum amount of daily vitamins and minerals that you can safely take without risking an overdose or serious side effects. For certain nutrients, the higher you go above the UL, the greater the chance of having problems.

DV (Daily Value) is the only measurement you’ll find on food and supplement labels. That’s because space is limited, and there’s a need for one single reference number. That number is the amount of a vitamin or nutrient that a person should get for optimum health from a 2,000 calories-a-day diet. The DV is sometimes the same as the RDA and sometimes not.

How do Vitamins Work?https://www.youtube.com/watch?v=ISZLTJH5lYg

Try this: Identify the following food items as micronutrients or macronutrients by placing a check mark in the correct box:

Food Item Micronutrient MacronutrientChewable Vitamin D pill

Bagel

Margarine

Iron pills

Vitamin E

Potato Chips

Green Beans

Apple Sauce

Chicken Breast

French Fries

Food Item Micronutrient MacronutrientChewable Vitamin D

pill

Bagel (carbs)Margarine (lipid)Iron pills Vitamin E

Potato Chips (carbs/lipids)Green Beans (protein)Apple Sauce (carbs)

Chicken Breast (protein)French Fries (carbs/fat)

Three forms of Digestion

1. Physical Digestion – (Mechanical) Part of the digestive process which breaks down the food

you eat into the small, soluble molecules you need is physical. This involves breaking the food down into smaller pieces which are easier to move along your digestive tract. The physical breakdown of the food also increases the available surface area for the action of the digestive enzymes. 

2. Chemical Digestion – The process by which food is broken down into simple

chemical compounds that can be absorbed and used as nutrients or eliminated by the body. In most animals, nutrients are obtained from food by the action of digestive enzymes. In humans and other higher vertebrates, digestion takes place mainly in the small intestine.

3. Absorption – Absorption in the digestive system refers to the typical

absorption of products by certain tissues. It can also be defined as the process of taking in nutrients into the body after digestion has taken place.

What exactly does absorption mean in the digestive process?

• Absorption is the movement of nutrients through membranes into the cytoplasm of cells

• It is the ultimate purpose of digestion-once nutrients are broken down into a form usable by our body’s cells, they are absorbed and provide nourishment for those cells

• Absorption takes place in the small and large intestines, and nutrients are transported by both the circulatory and lymphatic systems to all of the cells in the body

• Nutrients are absorbed by both diffusion and active transport• A thin walled capillary network extends through the core of the

villi (finger-like projections on the folds of the small intestine) and most dissolved nutrients are absorbed by the epithelial cells and then passed into the capillaries (part of the circulatory system)

• Digested fats cannot pass into the capillaries and must enter a vessel called a lacteal- part of the lymphatic system- they are then transported to adipose (fat) tissue where they are stored

• The large intestine mainly reabsorbs water

Video – Digestion: https://www.youtube.com/watch?v=MnnfN5BIX7E

Side note…

• The Circulatory system deals with the blood stream.

• The Lymphatic system is part of the circulatory system, consisting of a network of lymphatic vessels that carry a clear fluid called lymph directionally towards the heart.

o The human circulatory system processes an average of 20 litres of blood per day through capillary filtration which removes plasma while leaving the blood cells. Roughly 17 litres of the filtered plasma get reabsorbed directly into the blood vessels, while the remaining 3 litres are left behind in the interstitial fluid. One of the main functions of the lymph system is to provide an accessory return route to the blood for the surplus 3 litres.

End Products of Digestion

Simple Sugars

Amino Acids

Fatty Acids

Glycerol

Phosphates

Nitrogen Bases

These end products must be sufficiently small in size to pass through the submicroscopic pores in membranes, and be absorbed into the body without further change.