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The Skeletal System · Chapter 5 of 7
1987, age 12: on the first day of her period, a fever — and by morning a right knee like a waterThe universal solvent essential for life. balloon, hot and tight. Gone in four days. “A sprain. Reactive arthritis, maybe.” This chapter is the other skeletal tissue: cartilageA flexible connective tissue found in joints, the ear, nose, and rib cage. Cartilage can be of three — resilient, wet, avascularTo be devoid of blood capillaries. Epithelial tissue is avascular, kind of like a cap of dead cells, three kinds — the synovial joint it caps, the membrane that weeps, and two adult entries the same tissue explains: piercings that never healed, and a disc.
The question you will answer
Cartilage is the tissue bone is built from and the tissue that caps every joint. What makes it springy, why has it no blood supply, which kind is where — and what fills a knee overnight when nothing was injured?
Opener · The Water Balloon · about 1¾ minutes
The opener is the same narrated animation you will watch in Scene 1.
Watch the opener first. It sets the question; the chapter answers it.
1
Read the chart
Patient chart · Stina
1987 · age 12 · period-day fever, swollen knee
1987 · 12
First day of her period: fever 39 °C, belly pain. By morning the right knee is hot, tight, swollen, held bent; cannot bear weight. No injury. Four days; then nothing.
Three months later
The left ankle, same story, same fever. A truant officer at the door the week after (Module 1).
The ER
“Sprain? Reactive arthritis after a virus.” An X-ray: normal. No tap, no bloods.
Hindsight · 1995 · 20
Helix and nostril piercings red, weeping and sore for months; a lip piercing healed in two weeks. “Bad piercer.” Let them close.
Hindsight · 2015 · 40
MRI: L4/L5 disc herniated — the same disc that failed for Mom in her forties (Module 9).
Chart clues this module: 1 · The first fever · 6 · this chapter · 21 · period-day fevers
Before you go on · your prediction
A hot, tight, swollen knee overnight with a fever and no injury, gone in four days, then an ankle three months later. The best first reading is…
Open the one you lean toward. Nothing is recorded and nothing is revealed — you come back to it at the end.
A sprain she did not notice
Ask whether a sprain arrives with a fever and leaves in four days without a bruise.
A septic joint — infection in the knee
Ask what a septic joint does in four days untreated, and what a tap shows.
Sterile inflammation of the joint lining — the fever and the knee are one event
Ask what the synovial membrane is, what fills a joint when it is inflamed, and what a sterile, neutrophil-rich fluid with a fever means in a child.
From Stina’s diary
2
The story
Three short movements: the case, the anatomyThe study of the structure of the human body. and physiologyThe study of how the body functions., then the tie back to Stina. Each links to the scene where you’ll see it move.
I · The water balloon
In 1987, the first day of a period brought a fever, as it had started to; this time it also brought, by morning, a right knee swollen tight as a water balloon, hot to the touch, held bent, that would not take her weight. There was no injury. In four days it was a knee again. Three months later the left ankle did the same, on the same kind of day, and the week after a truant officer stood on the porch. The ER X-rayed the ankle — normal — and offered a sprain, or reactive arthritis after some virus. Nobody put a needle in the joint. If they had, the fluid would have been cloudy with neutrophils and grown nothing: sterile, inflammatory, the pattern of an FMF attack, in which a single large joint — knee, ankle, hip — swells with the fever and empties when it breaks, in three patients out of four. Two adult entries belong to the same tissue, read here in hindsight. At twenty, helix and nostril piercings wept for months while a lip piercing healed in two weeks. At forty, an MRI found the L4/L5 disc herniated — the one that failed for her mother at the same age.
See it move: Scene 1 · The Water Balloon · Scene 4 · The Joint
II · Wet, springy and unplumbed
Cartilage resists compression and springs back because its matrix is mostly water, held by proteoglycans in a mesh of collagenA structural protein in the dermis that provides strength and elasticity.. Its chondrocytes sit in lacunae and secrete that matrix; cartilage has no vessels and no nerves, so everything a chondrocyteMature cartilage cells housed in lacunae. needs diffuses in through the wet matrix. The outside is the perichondrium, a wrapper of dense irregular connective tissue that keeps the shape, carries the vessels, and holds the cellsThe basic structural and functional units of life. that grow the cartilage appositionally from the surface, while chondrocytes inside divide and grow it interstitially from within. Articular cartilage has no perichondrium — it is fed by the joint fluid. Avascular is why cartilage heals so badly: no bleeding, no clot, no cells arriving, and IL-1β on top tells chondrocytes to stop making collagen and start making the enzymesProteins that speed up chemical reactions in the body. that dissolve it. Three kinds. Hyaline — glassy, the commonest — caps every joint, joins rib to sternumFlat bone forming the center of the chest; anchor for ribs and clavicles. Appears as a vertical dagg, holds the nose and airway, and is the model every long bone is built on. Elastic — hyaline plus elastic fibers — is the ear and the epiglottisA flap of cartilage that covers the trachea during swallowing to prevent food from entering the airw, built to bend and snap back. Fibrocartilage — thick collagen bundles in rows — is the discs between vertebrae, the menisci of the knee and the pubic symphysisCartilaginous joint connecting the two pubic bones at the midline., built to take crushing and pull at once.
See it move: Scene 2 · Cartilage Is Not Bone · Scene 3 · Three Kinds in Three Places
III · The joint, the membrane, the pierced ear and the disc
A synovial joint — knee, ankle, hip — is two bones capped with hyaline cartilageThe most abundant cartilage type, found in joints, ribs, and the nose., in a fibrous capsuleThe outer protective layer of the kidney., with a cavity lined by the synovial membrane: thin, vascular, loose, making synovial fluid, an oily dialysate of plasmaThe liquid component of blood. with hyaluronic acidA substance that releases hydrogen ions (H⁺) in solution. that lubricates the surfaces and feeds the avascular cartilage. A knee normally holds a few milliliters. Inflame the membrane — synovitis — and its vessels leak, neutrophils pour in and the cavity fills with tens of milliliters: an effusion, the water balloon. In an FMF attack the membrane answers the same IL-1β surge as the peritoneumThe membrane lining the abdominal cavity and organs. and pleuraThe double-layered membrane surrounding the lungs and lining the thoracic cavity., the fluid is sterile, and between attacks the joint is normal. Reactive arthritis follows an infection by weeks; septic arthritis destroys a joint in days; hers tracked a fever and left. The piercings are the avascular rule applied: a lip is vascular and healed; the helix is elastic cartilageA flexible cartilage type found in the ear and epiglottis. and the nostril wall hyaline, each fed by diffusionPassive movement of molecules from areas of high to low concentration., each re-injured by every cytokine surge until she let them close. The disc is fibrocartilageA tough, shock-absorbing cartilage found in intervertebral discs and menisci. around a gel core, avascular in adults, repairing nothing, failing under load in the forties — in her and in her mother. The lecture says everybody has degenerative disc disease; in a family running on IL-1β it may simply arrive on schedule.
See it move: Scene 4 · The Joint · Scene 5 · Why Cartilage Cannot Heal
3
Watch · explore · think · check
5 scenes. Each one has a short animation or a slide, something to explore, a true/false spot-check of your thinking, and a quick check. Every scene gives you an evidence card for your board.
How to read the scenes
- Animation (dark teal) — a short animated explainer, one idea each
- Slide (dark teal) — a still to study: a micrograph, a diagram or a map
- Explore (purple) — something to push on while you watch
- Game (purple) — a quick challenge
- Think (gold) — reason it out, then spot-check yourself with a few true/false questions; not graded
- Check (gold) — a quick H5P that scores itself
Scene 1 of 5
The Water Balloon
A knee that filled overnight with a fever, emptied in four days, and grew no germs.
Animation · in production · 1 min 50 s
The Water Balloon
A calendar: day one of a period, a thermometer at 39. Night: a knee in section A cut or slice of the body or an organ for study. — capsule, cartilage caps, a thin membrane — the membrane’s vessels flush, neutrophils pour into the cavity, the knee balloons. Four days; it drains. Three months: the ankle. A needle that was never used draws cloudy fluid onto a plate that grows nothing. Caption: the knee and the fever were one event.
Prefer the full lecture? 3 Types of Cartilage (original video on the site)
Explore
What is in the fluid?
A knee in section and a syringe. Predict what the needle draws before you tap, sort four joint stories by their pattern, then work out what the ankle told the ER and what a count can and cannot prove.
Text description of this explore
A culture-bench look. Step 1: a knee cut front to back, the kneecap on the left: femur and tibia capped with articular cartilage, menisci between them, a pink synovial lining around the joint cavity and its pouch above the kneecap, and a syringe whose needle enters that pouch. Below it, an empty microscope field and an empty culture plate. Choose the knee (a normal knee; her knee on the first morning, as it would have been if tapped; her knee on day five; a septic knee; a knee twisted at soccer), predict what the syringe draws (a few mL, clear and pale yellow, few cells, nothing grows; tens of mL, cloudy yellow, thousands of white cells, mostly neutrophils, nothing grows; tens of mL, thick and opaque, a huge count of neutrophils, bacteria on the stain and the plate; or tens of mL, red with blood, few white cells, nothing grows), then tap. The cavity fills or stays thin, the syringe fills with the fluid, the microscope shows the cells and the plate shows growth or none, and a readout lists volume, appearance, white cells per µL, neutrophils, Gram stain and culture (teaching values; nobody tapped her knee). Step 2: four stories, each with a timeline of what came before, fever and joint swelling over ten weeks. A, age 9: fever 39.5 °C, one knee worse every day, opaque fluid with bacteria and colonies. B, age 16: a gut infection three weeks before, then a knee and an ankle, red eyes, a low fever, cloudy sterile fluid with neutrophils, still swollen at six weeks. C, age 12 in 1987: the first day of her period, fever 39 °C and belly pain, the right knee hot and tight by morning, no tap, normal on day four, the left ankle three months later. D, age 14: twisted at soccer, swollen within an hour, no fever, blood in the fluid. For each, choose the pattern (with the fever, sterile, gone in days; an infection weeks before; germs grow; an injury, no fever) and name it (septic arthritis, reactive arthritis, an FMF attack, a sprain or torn ligament). Step 3: four months in 1987: month 0, fever 39 °C and the right knee with no doctor; months 1 and 2 empty; month 3, fever 39 °C, the left ankle and the ER. Choose what the ankle told the ER that the knee alone did not. Step 4: range bars of white cells per µL in joint fluid on a log scale (normal under 200; reactive about 2,000 to 50,000; septic about 50,000 and up; the FMF row hidden until you commit, then shown from about 2,000 to over 100,000), with a dashed line at a common cutoff of 50,000. A classmate claims a count of 60,000 would have proved an infection; support or refute.
Think · not graded
Reactive arthritis follows an infection by weeks; septic arthritis would have destroyed the knee in four days; a sprain has no fever. Which features of her knee refute each, and what one test would have shown the fluid was sterile and inflammatory?
Spot-check your thinking: true or false?
Check · Fill in the Blanks
Define synovitis and effusion.
Evidence card 1
Add it to your evidence board
One joint, a fever, sterile fluid, four days, full recovery, twice — FMF arthritis is the defining pattern, and it was called a sprain.
Scene 2 of 5
Cartilage Is Not Bone
Mostly water, no vessels, no nerves — and a wrapper that does the growing.
Slide · in production
Skeletal Cartilage
A tissue that is mostly water and has no plumbing: strong under compression, slow to grow, and almost unable to heal.
Prefer the full lecture? 3 Types of Cartilage (original video on the site) · histology page: Hyaline Cartilage · The Glider
Explore
Bone or cartilage?
Twelve properties, two tissues. Sort them before the key, place the two kinds of growth, then push a needle into bone, into cartilage, and through cartilage into bone.
Text description of this explore
A ledger look. Step 1: two of the site’s micrographs side by side: hyaline cartilage, slide 40N (a smooth, glassy lavender matrix with chondrocytes in lacunae, no vessels) and ground compact bone (osteons as concentric rings around dark central canals, with small lacunae). Twelve property tiles (vascular, avascular, innervated, aneural, water-rich, mineralized, lacunae, osteons, perichondrium, periosteum, heals well, heals poorly) are each sorted into bone, cartilage or both before the key. Step 2: a drawing of a slab of hyaline cartilage under its perichondrium: a fibrous outer layer with a blood vessel, a thin inner layer of flattened cells (badge A), and the glassy matrix with chondrocytes in lacunae, including one lacuna with a group of four cells (badge B). Four tiles (appositional growth, interstitial growth, a 12-year-old’s femur getting wider, a 12-year-old’s femur getting longer) are each placed at A, from the surface, or B, from within, and you choose whether bone tissue itself grows that way. After you commit, arrows show layers added at A and cells pushing apart at B. Step 3: three panels with needle tracks: through a block of bone with vessels in its marrow; into cartilage, stopping above the bone; and through cartilage into the bone below. For each, choose the outcome: bleeds, clots and refills with bone in weeks; no bleeding and no clot, still a hole years later; or bleeds from the bone below and fills with fibrocartilage scar. After you commit, the tracks fill or stay empty.
Think · not graded
Bone and cartilage are both supportive connective tissues with cells in lacunae. List what cartilage lacks — vessels, nerves, mineral — and derive from the first two why it can be compressed all day without complaint and why it cannot repair a hole.
Spot-check your thinking: true or false?
Check · Fill in the Blanks
The perichondrium: two jobs, one way of growing, and the gliding surface it does not cover.
Evidence card 2
Add it to your evidence board
Avascular, aneural, slow — a tissue that a cytokine can damage and nothing can repair; the reason a knee recovers (the membrane) and a pierced helix does not (the cartilage).
Scene 3 of 5
Three Kinds in Three Places
Glassy, springy, rope-like — hyaline, elastic, fibrocartilage, on the site’s own slides.
Animation · in production · 1 min 50 s
Three Kinds in Three Places
A body outline. Hyaline lights up: joint surfaces, costal cartilage, nose, trachea rings, the fetal skeleton. Elastic: the ear, the epiglottis, the auditory tube. Fibrocartilage: the discs, the menisci, the pubic symphysis. Each jumps to its slide — glassy matrix with chondrocyte pairs; a dark mesh of elastic fibers; rows of cells between collagen ropes. Caption: three answers to three loads.
Prefer the full lecture? 3 Types of Cartilage (original video on the site) · histology page: Hyaline Cartilage · Elastic Cartilage · Fibrocartilage
Game
Place the cartilage
Fourteen places, three cartilages. Pin each before the key, read three unlabeled slides by their matrix alone, then test the In-Betweeners heroes’ hints on new stains.
Text description of this game
A pin-board look. Step 1: fourteen site tiles, each placed as hyaline, elastic or fibrocartilage: knee joint surface, costal cartilage, nasal cartilage (the wall of a nostril), tracheal ring, epiphyseal plate, external ear, epiglottis, auditory tube, intervertebral disc, meniscus, pubic symphysis, larynx (the thyroid and cricoid cartilages), fetal femur, and a helix piercing. Step 2: three unlabeled micrographs from the site, all in H&E: slide A, a smooth pale lavender matrix with chondrocytes in lacunae and no visible fibers; slide B, chondrocytes in pale lacunae each wrapped in a dense red mesh of fine fibers; slide C, thick wavy pink bundles with small cells in rows between them. For each, choose the type and the clue that decided it (smooth and glassy; a dark mesh around the lacunae; thick wavy bundles with cells in rows; or the color of the stain). Step 3: three more unlabeled micrographs in other stains: slide D, a dark navy-purple field with a dark mesh of fibers around each lacuna; slide E, a pale blue-green glassy matrix; slide F, a pink glassy matrix packed with small chondrocytes. The three In-Betweeners heroes each carry a hint: the Glider (hyaline), glassy; the Bouncer (elastic), a dark mesh; the Shock Absorber (fibrocartilage), rope rows. Choose a slide each hint fits, or none of the three.
Think · not graded
Three loads: a joint surface must glide under compression; an ear must bend and spring back; a disc must take crushing and twisting at once. Match each to its matrix — glassy proteoglycan gel, elastic fibers, collagen ropes — and say which kind failed in her ear, her nose and her spineProminent ridge on the posterior scapula dividing it into supraspinous and infraspinous fossae..
Spot-check your thinking: true or false?
Check · Drag the Words
Match each cartilage to its fibers and its locations.
Evidence card 3
Add it to your evidence board
Elastic helix, hyaline nostril, fibrocartilage disc — three cartilages on her chart, none with a blood supply, none able to repair what a cytokine kept re-injuring.
Scene 4 of 5
The Joint
Two caps, a capsule, a cavity and a membrane that makes the oil — the synovial joint and its classes.
Slide · in production
The Synovial Joint
The membrane is the organ of this chapter: vascular, loose, a serosa by behavior — it leaks when the cytokine says so.
Prefer the full lecture? 3 Types of Cartilage (original video on the site)
Explore
Label the knee, class the joints
The knee in a new view, cut front to back. Name seven parts, class twelve joints by how much they move and what holds them, then decide which joints her fevers could fill.
Text description of this explore
A hardware-store look, with hinges on every step. Step 1: a drawing of a knee cut front to back, the kneecap on the left, with a small effusion: the femur and tibia with blue caps, two pale wedges between them, yellow fluid filling the cavity and bulging into a pouch above the kneecap and behind the femur, a pink lining around the cavity, a thick band wrapping the back of the joint, and a small sac in front of the kneecap. Seven numbered pins: 1 where the two blue caps face each other; 2 on the band at the back; 3 in the fluid-filled space behind the femur; 4 on the pink lining at the top of the pouch; 5 in the fluid in the pouch; 6 on the back wedge; 7 on the sac in front of the kneecap. Name each pin from a list: articular cartilage, fibrous capsule, joint cavity, synovial membrane, synovial fluid, meniscus, bursa, periosteum, ligament. Step 2: twelve joints (skull suture; tooth in its socket; intervertebral disc; pubic symphysis; tibia and fibula along the shaft; elbow; hip; atlas on axis; base of the thumb; between carpal bones; wrist; knee). For each, choose synarthrosis (immovable), amphiarthrosis (slightly movable) or diarthrosis (freely movable), and what holds it together (fibrous tissue, cartilage, or a synovial capsule and cavity). Step 3: choose which class of joint FMF arthritis can fill, and why.
Think · not graded
A suture has no cavity; a disc has fibrocartilage and no membrane; a knee has a synovium. Explain why only the third class can produce an effusion, and why the synovium behaves like the peritoneum and pleura of her other attacks.
Spot-check your thinking: true or false?
Check · Multiple Choice
Which structures make up a synovial joint?
Evidence card 4
Add it to your evidence board
Knee, ankle — diarthroses with a synovium; the only joints that can balloon overnight and empty again.
Scene 5 of 5
Why Cartilage Cannot Heal
No vessels, no clot, no cells arriving — and a cytokine that tells chondrocytes to dismantle instead of build.
Animation · in production · 1 min 55 s
Why Cartilage Cannot Heal
A needle through a lip: vessels bleed, a clot forms, cells arrive, two weeks, healed. The same needle through a helix: no bleeding, no clot, chondrocytes sitting still; IL-1β lands on them and their collagen output drops while MMPs rise; months of weeping. Then a disc: fibrocartilage, avascular, the ring tearing under load at forty, repairing nothing — Mom’s disc beside it. Caption: avascular plus inflamed equals never.
Prefer the full lecture? 3 Types of Cartilage (original video on the site)
Explore
Three piercings, one disc
Four needles on one face, a dial of IL-1β, and a disc under load. Predict before each run, then sort her chart into what recovered and what never did.
Text description of this explore
A tattoo-flash look, with bold black outlines. Step 1: a tattoo-flash head in profile with four gold studs: in the lower lip, the earlobe, the helix of the same ear, and the wall of the nostril. For each, choose what happens (bleeds, clots and cells arrive, so it closes in weeks; or it bleeds only at the skin, with no clot or cells in the core, so it takes months, or never while attacks continue) and what the needle passes through (vascular soft tissue, elastic cartilage, hyaline cartilage, fibrocartilage). After you commit the studs color by tissue. Step 2: a chondrocyte in its lacuna in the helix’s elastic cartilage, with a slider for the IL-1β each monthly attack brings, from none to attack level (red diamonds gather around the cell). Predict what the chondrocytes do during each attack (keep building at their slow pace; build faster to repair the hole; make less collagen II and proteoglycan and more matrix-dissolving enzymes; or stop everything and die), then run a year: two gauges show the matrix made and the MMPs, and a plot shows the helix channel closing over twelve months, with a tick for each attack (teaching model). Step 3: the L4/L5 disc seen from above, a ring of fibrocartilage around a gel core with the spinal canal and nerve roots behind it, and a tear running toward the back. Choose the load (lying down, standing, bending forward, lifting while bent over) and the tear (inner layers, or through to the outer edge), predict what happens and what repairs it, then load it; the gel stays centered, pushes into the tear, or squeezes out against a nerve root, and red dots show vessels only at the outer edge of the ring (teaching model). Step 4: four entries from her chart (the right knee at 12; the helix at 20; the nostril at 20; the L4/L5 disc at 40). Sort each onto the membrane recovered or the cartilage never did, and name the tissue (synovial membrane, elastic cartilage, hyaline cartilage, fibrocartilage).
Think · not graded
A lip healed in two weeks; the helix and nostril wept for months; the disc failed at forty. Explain all three with two facts — no blood supply, and IL-1β switching chondrocytes from synthesis to degradation — and say why the knee, by contrast, recovered every time.
Spot-check your thinking: true or false?
Check · Multiple Choice
Select the reasons cartilage heals poorly.
Evidence card 5
Add it to your evidence board
Piercings that would not heal at twenty and a disc that failed at forty are the same sentence as the knee at twelve: avascular cartilage under a cytokine that never switched off.
4
Your evidence board
Every scene gave you an evidence card, and the chart adds more. Sort each card into the column it supports: Sterile FMF synovitis — the membrane answering the fever, Neither on its own, or A sprain, reactive arthritis, or infection. Some cards can honestly go in more than one place — that’s allowed, and the feedback tells you which cards decide the case.
5
Your verdict
Time to decide. Look back at your bet, then build your verdict from statements that hold up — no writing needed.
Look back at your prediction
A hot, tight knee overnight with a fever and no injury, gone in four days, then an ankle — the reading that fits best is…
Find the one you chose at the top. Does the evidence support it, refute it, or revise it?
- A sprain she did not notice
- A septic joint — infection in the knee
- Sterile inflammation of the joint lining — the fever and the knee are one event
Build your verdict · no writing
Choose the statement that holds in each set. The ones you keep become your argument.
6
The finding
Finding · the knee
One Event, Not Two
1987, age 12: on period-day fevers, a knee and then an ankle that balloon overnight, hot and tight, without injury, and empty in four days — “sprain”, “reactive arthritis”, no tap. Chart entry: the synovial membrane is a vascular lining that leaks and fills with neutrophils when IL-1β surges, giving a sterile effusion that resolves — FMF’s defining joint pattern; the cartilage beside it is avascular, which is why the membrane recovered every time and the pierced helix, the nostril and the L4/L5 disc never did. Held open: the cells in bone that answer the same cytokine — and a scan at thirty-eight.
Next · Chapter 6
Five Percent a Week
The backpack years: twenty pounds on a growing spine, 1986 to 1990. Bone remodels to the loads it carries — Wolff’s law — five to seven percent a week, run by two hormones and a vitamin. And in 2013, at thirty-eight, a scan said her bones were thin for her age.
Reliable information on rare diseases
NORD · NIH GARD · Orphanet · MedlinePlus Genetics: FMF · FMF & AID Global Association · Autoinflammatory Alliance · Global Genes · Amyloidosis Foundation
Stina has one rare disease. In the United States, about 1 in 10 people live with one of the more than 7,000 known rare diseases. These organizations are where patients, families and clinicians go for trustworthy information.
Hop to:
← Familial Mediterranean Fever — case home
All pages for Module 6 — The Skeletal System
6.0 Module Overview
6.1 Growing Pains
6.2 The Fitness Test
6.3 Pillars and Trusses
6.4 She’ll Grow Out of It
6.5 The Joint That Swelled With the Fever
6.6 Five Percent a Week
6.7 Broken, Mended, Read Whole
6.8 Conclusion and Assessment
6.9 The Evidence Behind the Case
All Modules
- Anatomical Language, Membranes & Homeostasis
- Just Enough Chemistry
- The Cell & Its Transport
- Making Cells & Proteins
- The Integumentary System
- The Skeletal System
- The Muscular System
- Nervous Tissue & the Senses
- The Spinal Cord
- The Brain & the Blood–Brain Barrier
- The Autonomic Nervous System
- Special Senses (in developmentThe process of growth and differentiation.)
- The Endocrine System
- Blood
- The Heart
- Blood Vessels
- The Digestive System
- The Respiratory System
- The Urinary System
- Fluids, Electrolytes & Acid–Base Balance
- The Reproductive System
- The Immune System
List of terms
- water
- cartilage
- avascular
- anatomy
- physiology
- collagen
- chondrocyte
- cells
- enzymes
- sternum
- epiglottis
- pubic symphysis
- hyaline cartilage
- fibrous capsule
- plasma
- acid
- peritoneum
- pleura
- elastic cartilage
- diffusion
- fibrocartilage
- section
- spine
- development