Digestion and Nutrition Notes

Animals cannot produce their own food like plants do.
They rely on diverse diets based on their environment.
Digestive systems vary to suit food requirements and habitat, each with its own advantages for survival.
When animals consume food, it is broken down into building blocks, like carbohydrates, which are turned into glucose.
This glucose is further processed to produce ATP, the energy needed for cellular functions, supporting the animal’s growth and survival.

Digestion is the process by which food is broken down into smaller components, like nutrients, so the body can absorb and use them for energy, growth, and repair.
Nutrition refers to the intake and utilization of nutrients from food, including carbohydrates, proteins, fats, vitamins, and minerals, which are essential for maintaining health and proper body function.

Suspension Feeders:
- Filter small organisms or food particles from water.
Substrate Feeders:
- Organisms that live on or within their food.
- They consume food as they move through it.
Fluid Feeders:
- Organisms that get their food from the blood or sap of their hosts.
Bulk Feeders:
- Animals that eat large foods.

Ingestion:
- Food is taken into the mouth.
Digestion:
- Ingested food is broken down into smaller components.
Absorption:
- Carbohydrates, fats, proteins, and nucleic acids are digested into their building blocks.
Elimination:
- Undigested materials make their way out of the digestive tract.

Compartmentalization:
- Occurs in compartments surrounded by body cells but not within the body cells in order to avoid self-digestion.
Single-celled organisms:
- Protists and sponges digest food inside food vacuoles.
- These vacuoles combine with lysosomes, which have special enzymes to break down food.
Gastrovascular cavity:
- Some animals, like cnidarians (jellyfish, corals) and flatworms, use a gastrovascular cavity for digestion.
- This cavity has only one opening, so the mouth is used to eat and remove waste.
Alimentary Canal:
- A digestive tract with two openings (a mouth and an anus).
- Most animals have this type.
- It is better because food moves in one direction, allowing different parts of the tract to handle different digestion steps.
Different structures after the esophagus:
- Crop – softens and stores food.
- Gizzard – grinds food for digestion.
- The intestine helps with chemical digestion and nutrient absorption.
- The anus removes waste from the body.

Digestion happens in a long tube called the alimentary tract, with help from other organs.
These organs produce special juices to break down food.
Digestion starts in the mouth with mechanical digestion.
Teeth break food into smaller pieces, while salivary glands make saliva.
Saliva helps lubricate food, neutralize acids, and kill bacteria.
Saliva also has an enzyme that starts breaking down starch.
The tongue shapes the food into a soft ball called a bolus, making it easier to swallow.
The bolus then moves down to the pharynx (throat) to continue digestion.
The pharynx has two openings:
1. The larynx (Adam's apple):
  - Which continues to your lungs.
2. The esophagus:
  - Leads the digested food to your stomach.
Epiglottis:
- Food can go down the wrong way and cause choking.
- To prevent this, the epiglottis (a small flap of cartilage) covers the larynx when you swallow, making sure food goes to the right place.
- When you breathe, it moves back up.
After swallowing, food moves from the pharynx to the esophagus when the esophageal sphincter opens.
This sphincter ensures that food moves in one direction only.
The esophagus, a muscular tube, pushes food down to the stomach using peristalsis, which are automatic muscle movements.

Digested food, called chyme, has a soup-like consistency that travels through the small intestine.
The small intestine then completes the digestion of food material that is partially digested in the oral cavity (starch), stomach (proteins), and other molecules (fats & nucleic acids).
Duodenum:
- The first part of the small intestine.
- It receives the secretions of the liver (bile) and pancreas (pancreatic juice) which will then join the chyme.
Emulsification:
- Bile from the liver breaks down fats to make them accessible for the digestive system.
Pancreatic juice:
- It neutralizes the acidity of chyme, together with enzymes from the wall of intestines.
- Its responsibility is to complete the digestion of food molecules.
The rest of the small intestine functions in the nutrient and water absorption.
It is critical to this function, which is said to be as large as a tennis court.
Vili:
- Finger-like projections in the intestine wall.
- Each villus is lined with thousands of tiny projections called the microvili.

Organ	Carbohydrate breakdown	Protein breakdown	Nucleic acid breakdown	Fat breakdown
Oral cavity, pharynx, esophagus	Polysaccharides → smaller polysaccharides	-	-	-
Stomach	-	Proteins → small polypeptides	-	-
Small intestines	Smaller polysaccharides → Disaccharides	Small polypeptides →small peptides	DNA, RNA → nucleotides	Fat→ glycerol, fatty acids, monoglycerides

Proteins, carbohydrates, and fats are the source of your energy and keep your body system functioning well.
Vitamins and Minerals.

Help to fight infection.
Make the healing process of wounds faster.
Make our bones stronger.
Involved in the metabolic process that enables us to get energy from the macronutrients.

Helps to visually represent how different foods and drinks can contribute towards a healthy balanced diet.

Malnutrition happens when a diet lacks calories or one or more essential nutrients.
It occurs when a diet is not enough to provide the individual with chemical energy.
It may also happen by eating carbohydrates from sodas and junk foods.

Essential nutrients are molecules which our bodies cannot make even if we have raw materials.
They are called