Organs in Humans

Organs in Human Anatomy

Definition: An organ is a group of tissues that work together to perform a specific function in the body. Part of: Organ systems (e.g., digestive, nervous). Examples: Heart, brain, lungs, stomach, skin.

🧠 What Is an Organ?

An organ is a specialized body part made of different tissues working together to keep you healthy and functioning. For example, the heart pumps blood, the lungs take in oxygen, the stomach digests food, and the brain controls thoughts and movement. Organs form systems that run your entire body.

🧬 From Cells to Systems

Body organization: Cells → Tissues → Organs → Organ Systems → Organism.

🏛️ Major Organ Systems and Their Main Organs

System	Main Organs	What It Does
Circulatory	Heart, blood vessels	Moves blood, oxygen, nutrients
Respiratory	Lungs, trachea, diaphragm	Brings in O₂, removes CO₂
Digestive	Stomach, intestines, liver	Breaks down food, absorbs nutrients
Nervous	Brain, spinal cord, nerves	Sends messages, controls actions
Muscular	Skeletal muscles, diaphragm	Moves body, maintains posture
Skeletal	Bones, joints	Supports body, protects organs
Endocrine	Glands (pituitary, thyroid)	Sends hormones to control functions
Excretory/Urinary	Kidneys, bladder	Removes waste, controls water balance
Reproductive	Ovaries, testes, uterus	Allows reproduction and growth
Integumentary	Skin, hair, nails	Protects body, controls temperature
Immune/Lymphatic	Lymph nodes, spleen	Defends against disease

🧠 Examples of Important Human Organs

Heart: Pumps blood; part of circulatory; made of cardiac muscle.
Brain: Controls thoughts, movement, breathing, senses; part of nervous; protected by skull.
Lungs: Exchange O₂ and CO₂; part of respiratory; work with heart.
Liver: Filters toxins, stores energy, makes bile; part of digestive.
Kidneys: Filter blood, make urine; part of urinary.
Stomach: Breaks down food with acid and enzymes; part of digestive.
Skin: Largest organ; protects, cools, senses touch; part of integumentary.

⚙️ How Organs Work Together

The brain tells the lungs to breathe.
The heart sends oxygenated blood to muscles.
The stomach digests food and the liver processes nutrients.
The kidneys clean blood after nutrient use.

🌡️ Can Organs Get Sick?

Asthma affects the lungs
Heart disease affects the heart’s pump
Kidney failure stops blood filtering
Liver damage from toxins or infection
Brain disorders like epilepsy or stroke

Specialists: cardiologist (heart), neurologist (brain), etc.

✅ Keeping Your Organs Healthy

Eat a balanced diet
Drink plenty of water
Exercise regularly
Sleep 8–10 hours per night
Don’t smoke or vape
See a doctor if you feel unwell

🧠 Vocabulary Review

Word	Meaning
Organ	Group of tissues working together
Tissue	Group of similar cells
System	Group of organs with related tasks
Homeostasis	Body’s way of staying balanced
Specialist	Doctor for a specific organ or system