Happy Star Wars Day!
Last weekend at the US Science and Engineering festival, I had the lovely honor of being part of the National Museum of Health & Medicine Booth in Washington, DC. While there, I got to paint some anatomy of the forearm on the staff (Thanks Gwen and Andrea for being awesome models!) and to the visitors who wanted hand bones painted. As someone who spent ages in the anatomy lab, I couldn’t help but lecture the visitors about what bones in the hand connects to which ones as I painted. Then I thought, “Hey! There are so many numbers found in our bodies! Cool!” 
To commemorate Star Wars Day 2014, I am sharing the 9 anatomical structures named “4th” that will always be with you (Unless you get some bones fused in surgery). Even though there are debates over midi-chlorian levels and what that really implies, here are 9 anatomical structures that are cannon in the anatomy textbooks. May the fourth be with you!
4th Cranial Nerve (CNIV)
Where is the fourth cranial nerve? 
Cranial nerve 4 or the Trochlear nerve is a motor nerve that arises directly from the brain to control the superior oblique.
4th ventricle
Where is the fourth ventricle? 
The 4th ventricle (colored dark blue) is inside your brain. As the name implies, there are total of four ventricles in the brain. The two lateral ventricles, the third ventricle, and the fourth ventricle.
4th rib
Where is the fourth rib?
The 4th rib is the fourth set of rib bones found in your thorax. The ribs protect the lungs and also move in a coordinated way to draw air into the lungs.
4th cervical vertebra and spinal nerve
Where is the fourth cervical vertebra? 
The 4th cervical (C4) is the fourth cervical vertebrae in the vertebra. There are 7 cervical vertebrae. Cervical spinal nerve 4 arises just above C4. C4 controls the movement of the diaphragm.
4th thoracic vertebra and spinal nerve
Where is the fourth thoracic vertebra? 
The 4th thoracic vertebra (T4) is found in the thoracic section of the vertebra. There are total of 12 thoracic vertebrae and each vertebra has rib attachments. The 4th ribs are attached to T4. Thoracic spinal nerve 4 arises just below T4.
4th lumbar vertebra and spinal nerve
Where is the fourth lumbar vertebra? 
The 4th lumbar vertebra (L4) is found in the lumbar section of the vertebra. There are total of 5 lumbar vertebrae. Lumbar spinal nerve 4 arises just below L4. The L4 nerve innervates muscles in the pelvic and thigh regions.
4th sacral segment and spinal nerve
Where is the 4th sacral segment? 
The most inferior part of the vertebra is the sacrum. The sacrum is a collection of fused bones. The 4th sacral spinal nerve arises from the 4th segment of the sacrum. The 4th sacral nerve innervates multiple muscles found in the pelvic region.
4th metacarpal bone
Where is the 4th metacarpal bone? 
The fourth metacarpal bone is found in the palm region of the hand that connects to the ring finger.
4th metatarsal bone
Where is the 4th metatarsal bone? 
The fourth metatarsal bone is found in the foot that connects to the fourth toe (the little piggy who had none)
Now you know about all the “fourths” in you, let them guide you and enjoy Star Wars Day!
The Takeaway: Q: Are there midi-chlorians in our bodies?
A: Maybe, but there are definitely some “fourth” structures in you. I love talking about anatomy and random stuff! What does midi-chlorians mean to you? To me it sounds like mitochondria. Please share your thoughts in the comments. Did I miss any? Let me know! Also, what are your thoughts on the upcoming Episode VII?
What are you planning to do to celebrate Star Wars Day? What other tips can you share with the readers on how to have fun on a holiday like this?
P.S. – First time reading my posts? Thanks for taking the time to stop by! Not only do I write for patch.com, but I’m also founder of the medical and scientific illustration services site, Studio Kayama, and give speaking programs and hands-on workshops that cover scientific illustration, Photoshop techniques, and more. I hope you’ll check them out!