RESPIRATORY SYSTEM PRIMARY function: BREATHING (for gas exchange): uptake oxygen needed by the cells release carbon dioxide produced by the cells (remove waste, pH balance of blood) Also used to produce SOUND

HUMAN ADAPTATIONS For efficient gas exchange to occur: Water must be present at the respiratory surface. Adaptation: Human lung located within the body cavity which contains a lot of water and air is moistened when it enters lungs. (Compare this to worm, fish, frog, insect…)

HUMAN ADAPTATIONS The respiratory surface must be large Adaptation: The human lung is made up of many branches to increase its surface area. Spread out on a flat surface it is about 90 m2 (the size of a tennis court!)

The Human Respiratory System Nasal cavity Path taken by air Path taken by food

The Human Respiratory System Part Function Special Features Nasal passages Point of entry Filter, warm, moisten air Mucus, hairs, many capillaries, sinus cavities, turbinates Oral Cavity Warm and moisten air Alternate space for gas exchange, no filtration

The Human Respiratory System Nasal Cavity Path taken by air Path taken by food Pharynx Epiglottis Esophagus

The Human Respiratory System Part Function Special Features Pharynx connects nasal and oral cavity to larynx Cilia in top portion move food towards mouth to be swallowed Epiglottis A flap that prevents food from entering the lungs by blocking the glottis (opening of trachea) Small, flexible

The Human Respiratory System Nasal Cavity Path taken by air Path taken by food Pharynx Epiglottis Esophagus Trachea Upper Respiratory Tract Larynx

The Human Respiratory System Part Function Special Features Larynx Contains the vocal cords – for sound, “voice box” “Adam’s Apple” two flaps of cartilage, vibrate when air passes through Trachea Passage of air into 2 bronchi, “windpipe” filter particles up to mouth ~12cm long -Semicircular cartilage rings to prevent collapse -Cilia and mucus

The Human Respiratory System Nasal Cavity Path taken by air Path taken by food Pharynx Epiglottis Esophagus Trachea Bronchi Bronchioles Upper Respiratory Tract Larynx

The Human Respiratory System Part Function Special Features Bronchus Each carries air into lungs and splits into many bronchioles Full cartilage rings for support Bronchiole Many branches carry air to alveoli Able to change diameter to regulate air flow Many branched tubes, Smallest passageways, to increase surface area Smooth muscle walls NO cartilage rings

The Human Respiratory System Nasal Cavity Path taken by air Path taken by food Pharynx Epiglottis Esophagus Trachea Bronchi Bronchioles Alveoli Diaphragm Upper Respiratory Tract Larynx Lower Respiratory Tract

The Human Respiratory System Part Function Special Features Alveoli (singular: alveolus) Site of external respiration (gas exchange) ~150 million very thin tiny sacs (large surface area) Single cell layer thick, surrounded by capillaries Coated with “surfactant” (a lipoprotein) to prevent sticking Diaphragm Increases and decreases volume of chest cavity Dome shaped, thin, muscular

The Human Respiratory System Part Function Special Features Pleural Membrane Surrounds lungs and lines chest cavity, reduces friction Filled with fluid that reduces friction during inhalation