Backbone Basics: The Spinal Column and Thoracic Cage

Dr. Stephen Flanagan

Welcome to the Flanatomy podcast. I’m your host, Dr. Stephen Flanagan. We’re diving into the wild world of anatomy with a side of crazy stories from my bizarre life. Let’s explore what makes you, you!

Keshia Rayna

And I’m Keshia Rayna, your co-host, keeping it one hundred and making sure Doc doesn’t get lost in his wild tales. I’m locked and loaded with my phone to fact-check and break down the nerdy stuff so y’all can vibe with the science.

Keshia Rayna

I am really excited for this episode Flan! Back in my physiology lab days, I spent hours piecing together skeletons and tracing spinal curves—it was like playing 3D Jenga with bones.

Dr. Stephen Flanagan

Awesome! So folks if you haven't pieced it together yet we are working through the central axis of the body and the bony cage that keeps your heart and lungs from getting squished. We’re going to talk about the vertebral column, its curves, regions, special features, and then the ribs and sternum that form your thoracic cage. We’ll cover the bones, markings, joints, and why this structure is basically the body’s shock-absorbing skyscraper.

Dr. Stephen Flanagan

Starting with the spinal column, also called the vertebral column or spine. In the adult, the vertebral column is formed from 26 bones. That’s because some fuse during development. At birth there are 33 vertebrae, but the sacral and coccygeal regions consolidate. The breakdown is: 7 cervical vertebrae in the neck region, 12 thoracic vertebrae in the chest, 5 lumbar vertebrae in the lower back, the sacrum — five fused bones inferior to the lumbar vertebrae — and the coccyx — four fused bones inferior to the sacrum. Here’s a super easy way to remember the numbers of the unfused regions: think of your daily meals. 7 a.m. cereal — that’s the 7 cervical vertebrae (neck bones — you wake up and move your head first thing). 12 o’clock turkey sandwich — the 12 thoracic vertebrae (midday, chest level, where your lungs and heart are busy). 5 p.m. lasagna — the 5 lumbar vertebrae (dinner time, lower back, where you carry the weight of the day). Sacrum and coccyx are fused, so they don’t get a meal slot — they’re the “leftovers” that stick together. Or, you might have desert at 5:54 where the 50 is 5 bones of the sacrum and the 4 min part is the fused bones of the coccyx but I find that that overdoes the mnemonic a bit.

Keshia Rayna

Cereal at 7, turkey sandwich at 12, lasagna at 5 — that’s the classic Mnemonic devise. Breakfast neck, lunch chest, dinner low back. So simple! The sacral five fuse into one sacrum — inferior to the lumbar vertebrae, forming the back of the pelvis. The coccygeal four fuse into the coccyx — inferior to the sacrum, your little tailbone remnant. I am not sure I like the "desert a 5:54 thing...

Dr. Stephen Flanagan

Yeah. I had a student tell me that one awhile back and I am not sure if it is useful but it does work, kind of. Now, let’s zoom in on the basic parts of a single vertebra. Each vertebra has a body — the thick, disc-shaped front part that bears weight. The vertebral arch is the bony loop behind it, formed by two pedicles (short pillars, from Latin pes which means foot) and two laminae (flat plates, from Latin lamina which means layer). The vertebral foramen — say “for amen” — is the hole in the middle, formed by the arch and body, where the spinal cord passes. Stacked up, these foramina make the vertebral canal. Jutting out are the transverse processes — lateral wings for muscle attachment, from Latin transversus which means across. The spinous process — the backward spike you can feel on your back, from Latin spina which means thorn. The superior articular process and facet — upward-facing joints that link to the vertebra above, with smooth cartilage facets (from Latin facetus which means polished).In lab, you can ID these on models or cadavers — body’s the chunky front, pedicles are the sides of the arch, laminae the roof, transverse processes the side arms, spinous process the back hook, superior articular process the upper knuckles. I always tell students to imagine a vertebra as a weird chair — body’s the seat, arch the backrest, processes the armrests and legs.

Keshia Rayna

Weird chair? That’s a new one. It is a little better than the 5:54 thing. So those parts let the spine stack, protect, and move. Let’s break down the regions, starting with cervical.

Dr. Stephen Flanagan

The seven cervical vertebrae (C1–C7) are the smallest and lightest — neck mobility over load-bearing. C3–C7 are typical cervical — body wider laterally for stability, spinous processes short and bifid (split, like a fork, from Latin bifidus which means split in two) except C7. All have transverse foramina — holes in transverse processes for the vertebral artery and veins. C7’s spinous process is the vertebra prominens — easy to palpate at the neck base, visible when bending forward. I use it to count vertebrae in lab — feel for that bump!

Keshia Rayna

Bifid processes like a fork? And transverse foramina for arteries — smart. So C3–C7 are the standard neck bones. What about the special ones — C1 and C2?

Dr. Stephen Flanagan

C1 is the atlas, named after the Greek myth where Atlas holds up the globe — here, it holds up your skull. No body, just anterior and posterior arches, with superior facets articulating with occipital condyles for “yes” nodding. C2 is the axis, with the odontoid process or dens (tooth-like peg, from Latin dens which means tooth) that the atlas pivots on for “no” rotation. No transverse foramen on the dens. The axis rotates the globe — meaning the skull and atlas spin around C2’s dens like a door hinge. So yes — the atlas rotates with the globe when you turn your head. In cadavers, you can twist the atlas on the axis — creepy but cool.

Keshia Rayna

Atlas holding the globe, axis spinning it — mythology meets anatomy. And the atlas rotates with the skull on that dens peg. What’s C7’s deal?

Dr. Stephen Flanagan

C7, the vertebra prominens, has a long, non-bifid spinous process — palpate it at the neck base, see it poke out when bending forward. It’s a landmark for counting vertebrae downward. In lab, students always find it first — feels like a knob.

Keshia Rayna

Knob landmark? Handy. Thoracic next?

Dr. Stephen Flanagan

Thoracic vertebrae (T1–T12) — all articulate with ribs. From a superior view, their bodies are heart-shaped — great for load distribution and rib attachment. Now, here’s where it gets interesting: each side of the body of T1–T10 bears demifacets for articulation with ribs. And speaking of “demi,” you know who was a famous demigod? Hercules! Son of Zeus and a mortal woman — half god, half human. The word “demi” means half, just like demifacets are half-facets — each rib head sits in a shared socket formed by the inferior demifacet of one vertebra and the superior demifacet of the next. So rib 2, for example, has its head resting half on T1’s inferior demifacet and half on T2’s superior demifacet. It’s a two-bone handshake for every rib — strong, stable, and perfectly balanced. Hercules would approve — half divine, half mortal, just like those demifacets are half on one bone, half on the next.

Keshia Rayna

Hercules as a demigod with demifacets? Doc, that’s the most mythological anatomy pun I’ve ever heard. So the rib heads are literally split between two vertebrae — half and half. What else do the ribs attach to?

Dr. Stephen Flanagan

Besides the demifacets on the bodies, each rib’s tubercle has an articular facet that hooks onto the transverse process of the corresponding thoracic vertebra. So it’s a three-point lock — two demifacets on the body, one on the transverse process. Tight ligaments between the neck of the rib and the transverse process keep it locked in place. In lab, we’d use pipe cleaners to thread through the costal facets and show how everything lines up — it’s like a bony puzzle.

Keshia Rayna

Three-point lock — sounds sturdy. So demifacets split the load, tubercle locks on the transverse process, ligaments tighten the deal. No wonder the thoracic cage is so solid. Lumbar?

Dr. Stephen Flanagan

Lumbar vertebrae (L1–L5) — thick, robust bodies for weight-bearing. Transverse processes thin, tapered. Spinous processes thick, blunt, point posteriorly. No rib facets, no transverse foramina. Lumbar look like moose heads — wide body “face,” transverse processes “antlers.” Thoracic like giraffes — long spinous processes “neck.” Cervical have bifid spinous processes — split like antlers.

Keshia Rayna

Moose, giraffe, antlers? Mnemonic magic! Sacrum?

Dr. Stephen Flanagan

Sacrum (S1–S5) — five fused bones, inferior to lumbar, triangular. Medial sacral crest (fused spinous processes), lateral sacral crest (fused transverse processes), posterior sacral foramina (for-ah-min-uh) for dorsal rami, anterior sacral foramina (for-ah-min-uh) for ventral rami. Sacral canal for cauda equina.

Keshia Rayna

For-ah-min-uh — got it. Fused for pelvic strength. Coccyx?

Dr. Stephen Flanagan

Coccyx — four fused bones, inferior to sacrum, tailbone remnant. Attaches pelvic floor muscles.

Dr. Stephen Flanagan

Sounds like the Tailbone is sort of like Evolution’s leftover. Spinal curves?

Dr. Stephen Flanagan

Yeah. that is about right. But there are some important muscle attachemnt points in the tailbone. There are Four curves: cervical/lumbar lordosis (inward), thoracic/sacral kyphosis (outward) — S-shape for balance, shock absorption.

Keshia Rayna

S-shape buffer. What about all the Joints?

Dr. Stephen Flanagan

Mostly cushioned by Intervertebral discs, fibrocartilage, nucleus pulposus jelly, annulus fibrosus ring. Facet joints are synovial and allow for some movement. then the stabilizing Ligaments are the anterior/posterior longitudinal, ligamentum flavum, interspinous, supraspinous.

Keshia Rayna

Discs cushion, facets glide, ligaments stabilize.

Dr. Stephen Flanagan

Yes! The spine has several key ligaments. The anterior longitudinal ligament runs along the front of the vertebral bodies, preventing hyperextension. The posterior longitudinal ligament is on the back side, inside the vertebral canal, stopping hyperflexion. Then there’s the ligamentum flavum — say fla-vuum — from Latin flavus which means yellow, ‘cause it’s yellowish from elastic fibers. It connects the laminae of adjacent vertebrae, elastic like a rubber band to snap the spine back after bending. The interspinous ligaments connect spinous processes, and the supraspinous ligament runs along the tips of the spinous processes from C7 down.

Keshia Rayna

Ligamentum flavum — that yellow elastic one? Oh, Doc, that takes me back to my son’s birth. I opted for an epidural to manage the pain, and the anesthesiologist walked me through the whole process. I’m sitting on the edge of the bed, hunched forward with my back arched, hubby holding my hand. They numb the skin with lidocaine first — cold sting, no big deal. Then comes the big needle, about 3-4 inches long, sliding between my lumbar vertebrae, probably L3-L4 or L4-L5. The doc says, “You’ll feel some pressure,” and pushes through the supraspinous and interspinous ligaments — like a dull poke. But then — pop! — the needle hits the ligamentum flavum, that thick, rubbery yellow band between the laminae. It’s got so much elastic tension, the needle breaks through with this audible “thunk,” like popping a champagne cork. My husband’s watching the whole thing, eyes wide, and when he hears that pop and sees the needle sink in, his face goes white, knees buckle, and boom — he faints right there on the hospital floor. Nurses rush over, laughing, “Happens all the time to the dads!” Meanwhile, I’m like, “Honey, I’m the one in labor here!” The doc threads the catheter through the needle into the epidural space, tapes it down, and starts the meds — sweet relief. But that pop through the ligamentum flavum? Unforgettable. It’s why epidurals work — the space just beyond is where the anesthetic spreads to numb the nerves.

Dr. Stephen Flanagan

Whoa, Keshia — your hubby fainting at the flavum pop? That’s classic! And yeah, that elastic “thunk” is the sign the needle’s in the right spot — the ligamentum flavum’s toughness is like nature’s gatekeeper to the epidural space. Glad it all worked out — your son’s got a great birth story now.

Keshia Rayna

He does! And I’ve got mad respect for that yellow ligament — tough but flexible, just like labor. What’s next, the thoracic cage?

Dr. Stephen Flanagan

The thoracic cage — the rib cage we all know and love. It’s formed by the thoracic vertebrae posteriorly, the ribs wrapping around laterally, and the sternum plus costal cartilage closing it off anteriorly. Basically, it’s the bony box that protects your heart, lungs, and big vessels, while also giving attachment points for shoulder girdle muscles and upper limb stuff.

Keshia Rayna

The classic rib cage — shield mode activated. So break down the sternum first?

Dr. Stephen Flanagan

Sure. The sternum — your breastbone — is made of three parts. The manubrium is the top section, kind of trapezoid-shaped. It has clavicular notches on the sides where the clavicles (collarbones) articulate, and it connects to the first two ribs. The body is the long middle chunk — that’s the bulk of the sternum. Its sides have notches for costal cartilage from ribs 2 through 7. The xiphoid process is the small, pointy bit at the very bottom. In kids and young adults it’s mostly cartilage; it ossifies and turns bony around age 40 or so. The junction between the manubrium and body is the sternal angle — you can easily feel it on yourself. It’s a reliable landmark because it lines up with the second rib and helps you count downward.

Keshia Rayna

Manubrium top, body middle, xiphoid tip — and sternal angle as the counting checkpoint. Nice. Now ribs?

Dr. Stephen Flanagan

Ribs — 12 pairs. They all attach to the thoracic vertebrae posteriorly, but anteriorly it’s different. The true ribs are pairs 1 through 7 — they connect directly to the sternum via their own costal cartilage. The false ribs are pairs 8 through 10 — their cartilage attaches to the cartilage of the rib above instead of going straight to the sternum. The floating ribs are 11 and 12 — they have no anterior attachment at all; their front ends just float free in the muscles of the abdominal wall. Each individual rib has the same basic parts: The head — articulates with the vertebral bodies (usually two demifacets on adjacent vertebrae).The neck — narrow part right after the head. The tubercle — has an articular facet that hooks onto the transverse process of its corresponding thoracic vertebra. The angle — where the rib bends. The shaft — the long curved part. The costal groove — runs along the inferior border inside, sheltering the intercostal vessels and nerves. That groove is super useful for telling left from right on a loose rib — the groove always faces downward and backward.

Keshia Rayna

True ribs go direct, false ribs borrow cartilage, floating ribs just hang out. Head, neck, tubercle, angle, shaft, costal groove — got it. And the groove helps with left vs right. So the whole cage is like a flexible armor box?

Dr. Stephen Flanagan

Exactly. The true ribs lock everything tight, the false and floating give a little springiness so you can breathe deeply and twist without cracking bones. It’s a brilliant design — protective but not rigid.

Keshia Rayna

I’m never looking at my rib cage the same way again. Alright, Doc — stories or wrap-up?

Dr. Stephen Flanagan

Let’s wrap it with the big picture. The spinal column and thoracic cage are your body’s central pillar and protective cage. From the 26 adult bones — 7 cervical, 12 thoracic, 5 lumbar, fused sacrum and coccyx — to the rib cage shielding your vitals, it’s the scaffolding that lets you stand tall, breathe deep, and survive everyday life.

Dr. Stephen Flanagan

Keep those skeletons clean, students, and let me know your favorite spinal curve or rib fact!