Structure of Nose – Class 11 | Chapter – 21 | Biology Short Notes Series PDF
Structure of Nose: The nose is the primary organ of smell and functions as an important respiratory organ in the body. Besides this, it is also involved in functions such as tasting. The air that we breathe is filtered through the nasal hair. The inhaled air is warmed and humidified before it enters the lungs.
What is the function of your nose?
Your nose is involved in several important bodily functions:
- Allows air to enter your body.
- Contributes to how you look and how you sound when you speak.
- Filters and cleans air to remove particles and allergens.
- Provides a sense of smell.
- Warms and moistens air so it can move comfortably into your respiratory system.
Structure of Nose
- Bone: The hard bridge at the top of your nose is made of bone.
- Hair and cilia: Hair and cilia (tiny, hairlike structures) inside your nose trap dirt and particles. Then they move those particles toward your nostrils, where they can be sneezed out or wiped away.
- Lateral walls (outer walls): The outer walls of your nose are made of cartilage and covered in skin. The walls form your nasal cavities and your nostrils.
- Nasal cavities: Your nose has two nasal cavities, hollow spaces where air flows in and out. They are lined with mucous membranes.
- Nerve cells: These cells communicate with your brain to provide a sense of smell.
- Nostrils (nares): These are the openings to the nasal cavities that are on the face.
- Septum: The septum is made of bone and firm cartilage. It runs down the center of your nose and separates the two nasal cavities.
- Sinuses: You have four pairs of sinuses. These air-filled pockets are connected to your nasal cavities. They produce the mucus that keeps your nose moist.
- Turbinates (conchae): There are three pairs of turbinates located along the sides of both nasal cavities. These folds inside your nose help warm and moisten air after you breathe it in and help with nasal drainage.
What’s the Trachea Do?
When you inhale air through your nostrils, the air enters the nasal passages and travels into your nasal cavity. The air then passes down the back of your throat into the trachea (say: TRAY-kee-uh), or windpipe, on its way to the lungs.
Your nose is also a two-way street. When you exhale the old air from your lungs, the nose is the main way for the air to leave your body. But your nose is more than a passageway for air. The nose also warms, moistens, and filters the air before it goes to the lungs.
What’s the Mucous Membrane?
The inside of your nose is lined with a moist, thin layer of tissue called a mucous membrane (say: MYOO-kus MEM-brayne). This membrane warms up the air and moistens it. The mucous membrane makes mucus, that sticky stuff in your nose you might call snot. Mucus captures dust, germs, and other small particles that could irritate your lungs. If you look inside your nose, you will also see hairs that can trap large particles, like dirt or pollen.
If something does get trapped in there, you can probably guess what happens next. You sneeze. Sneezes can send those unwelcome particles speeding out of your nose at 100 mph!
Further back in your nose are even smaller hairs called cilia (say: SILL-ee-uh) that you can see only with a microscope. The cilia move back and forth to move the mucus out of the sinuses and back of the nose. Cilia can also be found lining the air passages, where they help move mucus out of the lungs.
How Does Smelling Work?
The nose allows you to make scents of what’s going on in the world around you. Just as your eyes give you information by seeing and your ears help you out by hearing, the nose lets you figure out what’s happening by smelling. It does this with help from many parts hidden deep inside your nasal cavity and head.
Up on the roof of the nasal cavity (the space behind your nose) is the olfactory epithelium (say: ol-FAK-tuh-ree eh-puh-THEE-lee-um). Olfactory is a fancy word that has to do with smelling. The olfactory epithelium contains special receptors that are sensitive to odor molecules that travel through the air.
These receptors are very small — there are about 10 million of them in your nose! There are hundreds of different odor receptors, each with the ability to sense certain odor molecules. Research has shown that an odor can stimulate several different kinds of receptors. The brain interprets the combination of receptors to recognize any one of about 10,000 different smells.
How Does the Brain Recognize Smells?
When the smell receptors are stimulated, signals travel along the olfactory nerve to the olfactory bulb. The olfactory bulb is underneath the front of your brain just above the nasal cavity. Signals are sent from the olfactory bulb to other parts of the brain to be interpreted as a smell you may recognize, like apple pie fresh from the oven
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