Respiratory System Nostrils Pharynx Nostrils trap and filter

Respiratory System

Nostrils & Pharynx • Nostrils trap and filter out dust and foreign particles using tiny hairs and mucus • Air is warmed up and moistened • Pharynx is where nasal and oral cavities join

Trachea • Also known as the windpipe • Contains: 1. A flap-like structure called the epiglottis – When swallowing food, it prevents it from passing into trachea 2. The larynx (also known as the voice box because it contains your vocal cords air forced up from the lungs causes these vocal cords to vibrate and produce sound) In males, the larynx increases during puberty = deeper voice

Bronchi • Singular form: Bronchus • Two air passages that move inhaled air from the trachea to the right or left lung • Rings of cartilage surround both bronchi and trachea = increases flexibility of structures Cilia (tiny hairs) line the inside of the trachea, bronchi and bronchioles and are coated with mucus = prevents bacteria, dust and pollen from entering further down the lungs. Cilia sweeps it upwards to mouth (cough reflex).

Lungs • Contains: 1. Bronchioles – air passageways throughout the bronchus that become smaller and smaller until they reach tiny air sacs called alveoli 2. Alveoli – tiny air sacs in which gas exchange occurs

Gas Exchange • O 2 -poor blood enters network of capillaries on each cluster of alveoli • O 2 gas inside alveoli diffuses into the blood (and CO 2 diffuses out of the blood and enters the lungs in reverse fashion) • O 2 -rich blood leaves capillary network

How We Breathe • Two Steps: 1. Inspiration – air is forced into lungs (inhalation) 2. Expiration – air is forced out of lungs (exhalation) Just as molecules diffuses from area of high concentration to areas of low concentrations, air moves from areas of high pressure to areas of low pressure!

• Air pressure is less in lungs compared to the outside of the body INSPIRATION (air moves into lungs) • Air pressure is greater in the lungs compared to outside of the body EXPIRATION (air moves out of lungs)

Inspiration • Diaphragm contracts and moves downward • Rib cage moves outward due to the contraction of the intercostal muscles • Result: increase in volume of chest cavity causes a decrease in air pressure air moves into the lungs (Note – when volume increases, the pressure decreases)

Expiration • Diaphragm relaxes and moves upward • Rib cage moves inward due to the relaxation of the diaphragm • Result: Decrease in the volume of chest cavity causes an increase in air pressure air moves out of lungs (Note – when volume decreases, pressure increases!)

• Diaphragm – thin sheet of muscle that separates the abdominal organs (below it) from the organs of the chest cavity (above it) • Intercostal muscles – muscles between the ribs that raises the rib cage when contracted • Pleural membranes – Thin, fluid-filled membrane that covers the outer surface of the lungs to protect it as it constantly expands and contracts

Homeostasis and Respiration You are working out on a treadmill. After 15 minutes, you feel out of breath and find yourself breathing faster. Explain briefly how homeostasis is related to this. Normal breathing involves intake of O 2 and removal of CO 2. As you work out vigorously, you need more O 2 to keep up with the energy demands. Your brain detects that there is more CO 2 in the blood than O 2. The brain adjusts this by making you breath faster, so you can take in more O 2 to try to balance it out.