Organisation Basics & Digestive System

Think of your body like a massive corporation - it's all about organisation. Cells are your basic workers, tissues are departments of similar cells, organs are entire divisions, and organ systems are the company divisions working together.

Your digestive system is basically a food processing factory that turns your lunch into fuel your cells can actually use. It starts in your mouth where teeth mash everything up and saliva adds enzymes to begin breaking down food. From there, food travels down the oesophagus to your stomach - a muscular bag that churns food with acid.

Your liver produces bile to break down fats and neutralise stomach acid, whilst your pancreas releases powerful enzymes to tackle carbohydrates, proteins, and lipids. This whole system transforms insoluble food into soluble nutrients your body can absorb.

Quick Tip: Remember the digestive system as a disassembly line - each organ has a specific job in breaking food down further!

Digestion Continues & Enzymes

The small intestine is where the magic really happens - nutrients get absorbed into your bloodstream here. Whatever's left heads to the large intestine where water gets absorbed, and finally waste reaches the rectum and anus for elimination.

Enzymes are your body's molecular scissors - they're biological catalysts that speed up chemical reactions. Each enzyme has an active site that perfectly fits its substrate (the molecule it breaks down), like a lock and key.

Three key digestive enzymes you need to know: carbohydrase (found in mouth and small intestine) breaks carbohydrates into simple sugars, protease (stomach and small intestine) chops proteins into amino acids, and lipase (small intestine) splits lipids into fatty acids.

Your blood consists of plasma (the liquid that transports everything), red blood cells with haemoglobin for oxygen transport, white blood cells for fighting disease, and platelets for clotting wounds.

Memory Trick: Think "CPL" - Carbohydrase for Carbs, Protease for Proteins, Lipase for Lipids!

Blood Vessels & Heart Structure

Your circulatory system has three types of blood vessels, each perfectly designed for their job. Arteries carry oxygenated blood away from your heart under high pressure - they've got thick, muscular walls to handle this. Veins bring deoxygenated blood back to your heart at low pressure, so they're wider with thinner walls and have valves to prevent backflow.

Capillaries are the tiny connectors between arteries and veins - they're incredibly thin to allow easy diffusion of oxygen and nutrients to your cells. Blood plasma passes through capillary walls, delivering oxygen and glucose whilst collecting waste products.

Your heart is essentially two pumps working side by side. The right side deals with deoxygenated blood: the vena cava brings blood to the right atrium, which passes it to the right ventricle, then pumps it through the pulmonary artery to your lungs.

The pulmonary artery is unusual because it's the only artery carrying deoxygenated blood - remember this exception!

Heart Hack: Right side = deoxygenated blood going TO lungs, left side = oxygenated blood going TO body!

Heart Function & Coronary Heart Disease

The left side of your heart handles oxygenated blood: pulmonary veins bring oxygen-rich blood from lungs to the left atrium, then to the left ventricle, which pumps it through the aorta to your entire body.

Coronary heart disease happens when fatty deposits build up in the arteries supplying your heart muscle. This narrows the arteries, reducing oxygen supply to heart cells, which can lead to cell death and heart attacks. It's a non-communicable disease, meaning you can't catch it from someone else.

Treatments include stents (tiny mesh devices that keep arteries open) and statins (drugs that reduce cholesterol and slow fatty deposits). Risk factors split into medical ones you can't control (genetics, age, sex, ethnicity) and lifestyle ones you can (smoking, alcohol, diet, stress).

Faulty heart valves can become leaky or stiff, making your heart less efficient. This causes breathlessness and can be fatal. Replacement valves come in two types: mechanical valves $long-lasting but require blood-thinning medication$ and biological valves $no medication needed but only last 12-15 years$.

Remember: Your heart's natural pacemaker should beat around 70 times per minute - artificial pacemakers can step in when it fails!

Lungs & Gas Exchange

Your lungs are incredible gas-exchange machines. Air enters through the trachea (a flexible tube that stays open), travels through bronchi (which add moisture), then smaller bronchioles, and finally reaches alveoli - tiny air sacs where the real action happens.

Gas exchange occurs at the alveoli through diffusion. Oxygen moves from air into blood whilst carbon dioxide moves from blood into air to be exhaled. Capillaries surround each alveolus, collecting oxygen and dropping off carbon dioxide.

Diffusion in lungs is incredibly fast because of several factors: there's a short diffusion pathway (thin alveoli walls), a massive surface area from millions of alveoli, a rich blood supply constantly moving gases around, and air constantly moving in and out.

Your intercostal muscles and diaphragm work together to move air in and out of your lungs, creating the pressure changes needed for breathing.

Lung Logic: Think of alveoli like millions of tiny balloons covered in blood vessels - maximum surface area for gas swap!

Plant Organisation & Transport Systems

Plants have their own organisation system too! Epidermal tissues form protective outer layers that are transparent to let light through for photosynthesis. Palisade mesophyll cells are packed with chloroplasts and arranged to maximise light capture, whilst spongy mesophyll has gaps for gas diffusion.

Plants have two main transport systems: xylem and phloem. Xylem consists of hollow tubes strengthened with lignin that transport water and mineral ions from roots to leaves. Mature xylem cells are actually dead - they're like biological water pipes.

Phloem transports sugars made during photosynthesis from leaves to the rest of the plant through translocation. These are living tubes of elongated cells with pores allowing cell sap to move between them.

Meristem tissue contains stem cells that can divide rapidly and become any type of plant cell - it's how plants grow. In trees, xylem makes up most of the wood whilst phloem sits in a ring under the bark.

Plant Tip: Remember "X for eXport water up, P for Phloem sugars around" - xylem goes up, phloem goes everywhere!

Plant Transport Details

Translocation is the movement of sugars from leaves to storage areas where plants keep food for winter energy. This process is so vital that aphids and greenfly can actually kill plants by tapping into phloem tubes and stealing all the sugar transport.

In woody plants like trees, you can see this organisation clearly - the xylem forms the bulk of the wood (the dead water transport system), whilst the living phloem sits just underneath the protective bark layer.

The phloem is particularly important because it connects photosynthetic leaves to storage cells throughout the plant. Without this sugar highway, plants couldn't store energy for growth, reproduction, or surviving winter months.

Understanding plant transport helps explain why ring-barking (removing bark around a tree's circumference) kills trees - you're cutting through the phloem and stopping sugar transport, even though the xylem water system remains intact.

Garden Wisdom: This is why gardeners protect tree bark from damage - it's not just protection, it's the plant's food delivery system!

Cancer & Disease

Cancer occurs when DNA in cells mutates, causing them to multiply rapidly and uncontrollably. It's another non-communicable disease that can't be spread from person to person, but understanding its causes helps with prevention.

Cancer risk factors include things you can't change $genetics - some cancers are inherited$ and things you can control. Lifestyle factors include smoking (contains carcinogens), alcohol (also contains carcinogens), obesity and poor diet (damages DNA), and UV exposure from sun or radiation.

Tumours come in two types: benign tumours are not cancerous, grow slowly, stay contained within a membrane in one area, and don't spread. Malignant tumours are cancerous, grow rapidly, break through membranes, spread to other body parts through blood, and form secondary tumours.

The key difference is that malignant tumours can metastasise - break off pieces that travel through your bloodstream to start new tumours elsewhere in your body. This spreading ability is what makes cancer so dangerous.

Cancer Key: Benign = Basically harmless and stays put; Malignant = Moves around and causes Major problems!