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🧩
Everything has a job
Structure & Function
Form follows function — at every level, from organelles to organ systems.
🔬 Specialized cells
Nerve cell
Long axon → carries signals fast.
Red blood cell
Disc shape, no nucleus → packs more oxygen.
Muscle cell
Tons of mitochondria → ATP for contraction.
🫀 Body systems (know the jobs)
Circulatory▾
Heart + vessels move O₂, nutrients, hormones, and CO₂ around the body.
Respiratory▾
Lungs exchange O₂ in and CO₂ out — feeds cellular respiration.
Digestive▾
Breaks food into nutrients (small enough to enter blood).
Nervous▾
Brain + nerves sense and respond — fast electrical signaling.
Endocrine▾
Hormones — slow, body-wide chemical messengers.
Excretory▾
Kidneys filter waste from blood (urea, extra water).
Immune▾
Defends against pathogens.
Muscular / Skeletal▾
Move + support the body.
🌡️ Homeostasis
Keeping internal conditions stable despite outside changes. Think: thermostat.
1. Stimulus
Body temp rises.
2. Response
Sweat glands activate.
3. Feedback
Temp drops → sweating stops.
Other examples: blood sugar (insulin/glucagon), water balance (kidneys), pH.
🎯 Quiz yourself
Structure · QuizQ1 / 4