Human respiratory system includes: Nose → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Lungs. Hands, legs, skin (except in amphibians) are not part of respiratory system.
Respiration is the process of gas exchange (taking in oxygen and releasing carbon dioxide). It involves specific organs that form the respiratory system.
Organs Involved in Respiration:
Nose/Nasal Cavity:
Air enters through nostrils
Filters, warms, and moistens air
Contains hair and mucus to trap particles
Pharynx and Larynx: Passage for air to trachea
Trachea (Windpipe):
Tube carrying air to lungs
Supported by C-shaped cartilage rings
Lined with cilia and mucus
Bronchi and Bronchioles: Branches within lungs
Lungs:
Main organs of respiration
Contain millions of alveoli for gas exchange
Oxygen enters blood, carbon dioxide removed
Why Hand is Not Involved:
Hand is part of the skeletal and muscular system
Its functions: grasping, touching, feeling, performing fine motor tasks
Has no role in breathing or gas exchange
Skin of hand does not participate in respiration (unlike some amphibians)
Why Other Options are Involved:
(A) Nose: Entry point for air; filters and conditions air
(C) Lungs: Primary organs where gas exchange occurs
(D) Trachea: Air passage connecting throat to lungs
Final Answer: Hand
