Chapter Text
Sanji lies in bed staring blankly at the ceiling. “What’s the muscle that originates from the lateral surface of the ventral border of the latissimus dorsi?”
“Pretty sure it’s the epitrochlearis. It’s one of those muscles that inserts into the olecranon process of the ulna.” Zoro chucks the anatomy book at the blond making sure to extend his forearm with his triceps.
“How the hell am I supposed to remember all of these in time for the practical. Okay, so what supinates the hand and flexes the antibrachium?”
“Biceps brachii. It comes from the bicipital groove of the humerus and goes into the radial tuberosity near the top of your radius. You’d know if you ever used those tiny arm muscles.”
He just wants to knock the smirk off of Zoro’s face but he can’t afford it. This idiot knows his forelimbs.
“Brachioradialis. That comes from the lateral supracondylar ridge of the humerus. Where does it insert?”
“The distal styloid process of the radius. It’s another forearm flexor at the elbow. The styloid is opposite of where your wrist bone is.”
Sanji starts flexing his hands that are cramping up from all the writing he’s been doing. Zoro asks, “What muscles are you using right now?”
“Uhh, the flexor carpi radialis and ulnaris. The radialis abducts and the ulnaris adducts.”
“They both have the same origin and insertion of the medial condyle of the humerus and metacarpals-“
“But the ulnaris also originates from the olecranon process of the ulna and pistiform bones! The pisiform bones are also carpals.” Sanji smiles at him and they continue on with the extensors. “Extensors are always on the side of the arm with the arm hair, isn’t it?”
He glances at Zoro who’s slowly moving his arm out of view. He jumps off the bed and extends his wrist to catch Zoro before he can escape Sanji. “You’re hairless! How?”
“If you tell me all the extenders in the forearm, I’ll tell you.”
“Extensor carpi radialis longus, brevis, lateralis, and ulnaris. Only the longus originates from the lateral supracondylar ridge of the humerus. Everything else originates from the epicondyle. They go into the metacarpals and extend the wrist. Now tell me why you’re a hairless rat.” Sanji loosens the grip on his forearm.
“Pretty sure it’s just genetic. My parents didn’t have much body hair either. I would have been a perfect candidate for the swim team.” Zoro pulls out the stool from underneath his desk and Sanji sits himself down along with the rest of his papers. “Okay what’s next?”
“The triceps brachii, long, lateral, and medial. I know they all insert into the olecranon process of the ulna and extend the forearm. They’ve all got different origins though.”
Zoro opens up the textbook and starts to look for some figures. He’s got his fingers between a couple pages so Sanji assumes they’re looking at a couple of different spots. “Okay, the long head originates from the axilary border of the scapula which is below the glenoid fossa and the lateral head is at the proximal point of the deltoid ridge.”
“Basically it’s the upper shaft of the humerus.” Zoro nods continuing with his explanation.
“Now the medial has two heads. The dorsomedial surface of the humerus and the medial surface of the supracondylar foreman. It’s the hole that you can see in the humerus.”
“We’ve got three more and I’m gonna make dinner.” Sanji is just about ready to burn the book as fuel for their pasta later. “Brachialis is a forearm flexor. It comes from the lateral surface of the humerus and inserts medially on the ulna’s surface below the semilunar arch.”
“Did you remember that one?”
“Nah, I’m just reading it word for word from the packet he gave us. It’s behind the biceps brachii.”
“What muscle adducts the humerus?” Zoro performs the motion for added emphasis.
Sanji has to look away because he thinks he can actually fucking see the muscle. “The coracobrachialis. It comes from the coracoid process of the scapula and inserts into the medial shaft of the humerus. I think of the humerus like your dick. Medial is the inside part closer to your thigh and lateral surface is closer to your other thigh. Somehow it works.”
Zoro chokes on nothing. There’s a blush creeping across his cheeks that he turns away to hide. “Last one. The supinator that supinates the arm.”
“It originates on the supinator crest of the ulna and the lateral epicondyle of the humerus. I believe it inserts into the radial tuberosity.”
“Do you know where the supinator crest is?” Zoro brushes small strands out of his face.
“It’s where the radius kind of lies in?”
“Close enough. I’m starving. Do we have any sausage for that pasta?”
———————
Zoro likes studying with Sanji. Not just because he actually does like Sanji that way and seeing his bangs fall over his eyes is extremely sexy. They both seem to know exactly what the other doesn’t. They fill each other’s holes. Sanji’s about to teach him the leg muscles and he tends to get very physical teaching.
He almost drops his water bottle when he steps into the room. Sanji’s just got on his compression shorts. It’s gonna be a while before they can go on a run together.
Sanji sits on the desk and spreads his legs. He’s pointing at the top of his pale inner thigh. “What muscle originates from the anterior superior iliac spine of the pelvis?”
“The sartorius. It inserts into the upper tibia. Flexes, abducts and laterally rotates the hip.”
“Good now how about the muscle next to that? The one that adducts and medially rotates the hip and inserts in the same spot.”
Why does he even let Sanji tease him like this? “It’s the gracilis that comes from the ischiopubic ramus.”
“I have absolutely no clue how to demonstrate the vastus lateralis origin but it does insert into the patella.” Sanji extends his leg out and feels around for the muscle. “Just remember that it originates from the greater trochanter of the femur”
“Are you going to take off your shorts to teach me this one?” Zoro smirks. But it quickly disappears when Sanji starts pulling his waistband down over his hips. “How is this effective?”
“You’re never going to forget what my ass looks like. Now gluteus medius and maximus.” Sanji puts his lithe fingers on the pert behind.
“They both originate on the gluteal surface of the ilium. The medius inserts into the greater trochanter of the femur while the maximus is at the gluteal tuberosity.”
“When I kick someone’s ass, my medius is abducting the hip and I can rotate laterally my thigh. The maximus rotates and extends the hip.”
“Your ass can’t be real right?”
“Come to the gym on wednesdays and thursdays after 10 and you’ll know. Let’s move on.” Sanji pulls his shorts back up and just points to an area next to his maximus. “What’s this?”
“The tensor fasciae latae. It’s a triangle that comes from the iliac crest and connects into the illiobtibal tract which is a tendon of sorts.”
Sanji runs his hand up and down his outer thigh flexing his knee at the same time. “So, how about the biceps femoris?”
“It comes from the ischium tuberosity, linea aspera of the femur. And inserts into the head of the fibula.”
Zoro’s barely ready for it when Sanji holds his ankle, extends his foot, and he’s gifted with a direct view of the back of Sanji’s calf.
“Your gastrocnemius originates from both of your condyles. It’s a knee flexor that attaches to the achilles tendon. I don’t really care for the scientific name.”
“Calcaneus, marimo. You never know if they’ll ask it or not. Now what else attaches to the achilles tendon.”
After a moment’s pause he says, “The soleus. Except it originates from the lateral surface of the head and proximal point of the ventral border of the fibula. So it’s a little lower downward.”
He starts to extend his toes. “This is the extensor digitorum longus or the EDL. It’s on the lateral epicondyle of the femur. And attaches to every toe tendon but the big one.”
Sanji lets go on his ankle flexes his foot upward. “What muscle am I using?”
“The tibialis anterior. It’s on the lateral shaft of the fibula and the head of the fibula. These ones are weird. Because you could also be using your peroneus longus. Since that originates from the head and lateral surface of the shaft of the fibula.”
“You’re technically right on both accounts. Now where do they insert?”
“Into the metatarsals. But only the 1st one and the 5th one for the peroneus longus.”
Sanji stretches out on the table so that Zoro can get a better view of the actions of the deeper thigh muscles.
“This one you can’t really see even if you cut into me but imagine that you can.” Sanji’s pointing at his inner thigh and Zoro needs to take a deep breath. “Which muscle am I talking about?”
“Your pectineus. It starts at the pectineal line of the pubic bone and end at the pectinal line of the femur. It flexes the thigh. Now please close your thighs. I’m mildly turned on by this study session.”
“Too bad. You’ve still got two more adductors to go through.” Sanji opens them wider as if that was actually possible. Zoro would very much like to test how far back they can go later. “The longus and the femoris?”
“They both insert into the linea aspera of the femur. The longus is in the pubic bone and adducts your skinny hips.”
“Oi!”
Zoro narrowly avoids the kick aimed at his stomach. “The femoris is on the inferior ramus and also laterally rotates your thigh.”
“What are three muscles that insert into your patella?”
“Rectus femoris, vastus medialis, and the vastus intermedialis.”
“How about their origins in order?”
“The rectus is in the anterior inferior iliac spine, medialis is medial on the femur and intermedialis is on the anterolateral.”
“How are you going to remember their actions?”
“The rectus extends the knee and flexes the hip while both vastus extends the lower leg.”
Zoro takes advantage of Sanji’s position to run his rough fingers along the most medial part of Sanji’s thigh. “What are these muscles that extend your hip and flex your knee?”
“The semimenbranosus and semitendinosus. They’re both in the ischial tuberosity and insert into the tibia.”
“There’s a difference. Membranous medial condyle of the tibia and tendinousus is in the upper tibia.” Zoro pulls his fingers away to move back but is stopped by strong ankles.
Sanji pulls Zoro in-between his legs so that their crotches are flush against each other. He flexes his toes against the back of Zoro’s thighs. “So what muscles are turning you on?”
“Maybe your dick but how about the flexor digitorum longus and hallucis longus?”
Sanji drawls quietly in in his ear. “The digitorum comes from the head of fibula and the shaft of the tibia. And the hallucis starts in the shafts of the tibia and fibula.”
“Where do they insert?
“They insert into the tendons of each other.” Zoro completely loses it. He’s 90% sure that they’re both not going to walk out of this exam unaroused.