Chapter 16 - Section 16.5 - Study Guide - Assess Your Learning Outcomes - Page 626: 3

The lacrimal apparatus is responsible for producing and draining tears, which help keep the eye moist and clean. Tears contain a combination of water, mucus, and various proteins that protect and nourish the eye's surface. The lacrimal apparatus consists of several components, and tears follow a specific route as they wash over the eye and ultimately drain into the nasal cavity. Here are the main components and the route taken by tears: 1. **Lacrimal Glands**: - The lacrimal glands are located above the outer corner of each eye, and they produce the watery component of tears. 2. **Accessory Lacrimal Glands**: - There are smaller accessory lacrimal glands in the eyelids and conjunctiva that also contribute to tear production. 3. **Tears' Distribution over the Eye**: - Tears are secreted by the lacrimal glands and accessory glands onto the surface of the eye. - They spread evenly over the eye's surface with the help of blinking and the smooth, curved shape of the cornea and conjunctiva. 4. **Blinking**: - Blinking helps distribute tears and remove debris from the surface of the eye. - Tears are also spread across the eye during the blink cycle. 5. **Drainage**: - Excess tears, as well as tears that have completed their function, need to be drained to prevent overflow. - The drainage begins with the puncta, small openings located in the inner corner of each eyelid. - Tears then flow into the canaliculi, small channels leading from the puncta to the lacrimal sac. 6. **Lacrimal Sac**: - The lacrimal sac is a small pouch located at the upper part of the nasal cavity. - It collects tears from the canaliculi. 7. **Nasolacrimal Duct**: - Tears then flow from the lacrimal sac into the nasolacrimal duct. - The nasolacrimal duct travels downward, carrying tears into the nasal cavity. 8. **Nasal Cavity**: - Tears, now drained of excess fluid and waste products, enter the nasal cavity through the nasolacrimal duct. - They mix with the nasal mucus and are eventually swallowed or blown out through the nose. This drainage system is why crying often leads to a runny nose, as the tears flow into the nasal passages. The connection between the lacrimal apparatus and the nasal cavity helps maintain eye moisture and provides an additional function by aiding in the removal of waste and foreign particles from the eye's surface.

The lacrimal apparatus is responsible for producing and draining tears, which help keep the eye moist and clean. Tears contain a combination of water, mucus, and various proteins that protect and nourish the eye's surface. The lacrimal apparatus consists of several components, and tears follow a specific route as they wash over the eye and ultimately drain into the nasal cavity. Here are the main components and the route taken by tears: 1. **Lacrimal Glands**: - The lacrimal glands are located above the outer corner of each eye, and they produce the watery component of tears. 2. **Accessory Lacrimal Glands**: - There are smaller accessory lacrimal glands in the eyelids and conjunctiva that also contribute to tear production. 3. **Tears' Distribution over the Eye**: - Tears are secreted by the lacrimal glands and accessory glands onto the surface of the eye. - They spread evenly over the eye's surface with the help of blinking and the smooth, curved shape of the cornea and conjunctiva. 4. **Blinking**: - Blinking helps distribute tears and remove debris from the surface of the eye. - Tears are also spread across the eye during the blink cycle. 5. **Drainage**: - Excess tears, as well as tears that have completed their function, need to be drained to prevent overflow. - The drainage begins with the puncta, small openings located in the inner corner of each eyelid. - Tears then flow into the canaliculi, small channels leading from the puncta to the lacrimal sac. 6. **Lacrimal Sac**: - The lacrimal sac is a small pouch located at the upper part of the nasal cavity. - It collects tears from the canaliculi. 7. **Nasolacrimal Duct**: - Tears then flow from the lacrimal sac into the nasolacrimal duct. - The nasolacrimal duct travels downward, carrying tears into the nasal cavity. 8. **Nasal Cavity**: - Tears, now drained of excess fluid and waste products, enter the nasal cavity through the nasolacrimal duct. - They mix with the nasal mucus and are eventually swallowed or blown out through the nose. This drainage system is why crying often leads to a runny nose, as the tears flow into the nasal passages. The connection between the lacrimal apparatus and the nasal cavity helps maintain eye moisture and provides an additional function by aiding in the removal of waste and foreign particles from the eye's surface.