BIO 004 · Human Anatomy
Bone Histology
Block 2 · Module 1: Bone Histology
A reference for the bone histology video and lab. Bone and cartilage are the supportive connective tissues. This page covers cartilage, the structure of a bone from the whole organ down to the osteon, the bone cells, and how bone forms and grows.
How to use this sheet Toggle the toolbar above. Notes prints the full reference for review. Study prints as a fill-in-the-blank worksheet. Print it, then write each answer while you watch the video or read your book. Quiz me is on-screen practice: type the term or click Reveal to check yourself. The grids and the sequence respond to Study and Quiz too.
The Foundations video gives you a complete foundational understanding of this topic, enough on its own for a foundational course. Learn it first, then move on to the Deep dive, which adds the majors-level material: the osteon, the bone cells, and the growth plate and its zones.
- Describe the three types of cartilage and the cells and matrix that make up cartilage.
- Classify bones by shape and identify the gross parts of a long bone.
- Describe the microanatomy of compact bone, centered on the osteon, and contrast it with spongy bone.
- Identify the four bone cell types and what each one does.
- Outline how bones form and grow, using the growth plate and its zones in order.
Your pre-work
Work through these the evening before class. None of it is turned in. It is how you learn the material and build your spaced recall.
This is more than a checklist. Ticking these boxes is the start, not the finish. Committing this material to memory and being able to apply it takes considerable time and repeated effort. You are not done when the boxes are checked. Put in the real hours, and keep coming back for frequent recall and review until the material is genuinely yours.
Long bone anatomy
Add a labeled longitudinal section of a long bone.
The osteon
Add a labeled cross-section of compact bone showing one osteon.
The growth plate
Add a labeled view of the epiphyseal plate and its zones.
Cartilage
Cartilage is a firm, flexible connective tissue. It has no blood vessels of its own, so it heals slowly.
The cartilage tissue
- Chondrocytesthe cartilage cells, each one sits in a small space called a lacuna
- Lacunaethe cavities in the matrix that house the chondrocytes
- Matrixa firm gel of ground substance with collagen, and in some types elastic fibers
- Perichondriumthe connective tissue sheath wrapped around most cartilage
The three types of cartilage
| Type | Fibers and texture | Where it is found |
|---|---|---|
| Hyaline cartilage | fine collagen, glassy and smooth, the most common type | ends of long bones, the nose, the airways, the costal cartilages |
| Elastic cartilage | many elastic fibers, flexible and springy | the external ear and the epiglottis |
| Fibrocartilage | thick bundles of collagen, tough and shock-absorbing | the intervertebral discs, the knee menisci, the pubic symphysis |
How cartilage grows
| Type of growth | What happens | Where it starts |
|---|---|---|
| Appositional | new cartilage is added at the outer surface | from the perichondrium |
| Interstitial | the cartilage expands from within | chondrocytes divide inside the matrix |
Bone Classification and the Long Bone
Bones by shape
| Shape | Description | Examples |
|---|---|---|
| Long | longer than they are wide, a shaft with two ends | femur, humerus |
| Short | roughly cube-shaped | carpals, tarsals |
| Flat | thin and often curved | sternum, ribs, most skull bones |
| Irregular | complex shapes that fit no other group | vertebrae, hip bones |
| Sesamoid | small bones formed within a tendon | patella |
Gross anatomy of a long bone
- Diaphysisthe shaft, a tube of compact bone around the medullary cavity
- Epiphysiseach expanded end, spongy bone under a thin compact shell
- Metaphysisthe region between diaphysis and epiphysis, holds the growth plate or its remnant
- Medullary cavitythe hollow core of the diaphysis, holds marrow
- Articular cartilagehyaline cartilage capping the epiphysis where it meets another bone
- Periosteumthe connective tissue membrane covering the outer bone surface
- Endosteumthe thin membrane lining the internal bone surfaces
- Epiphyseal linethe remnant of the growth plate after growth in length ends
Bone Microanatomy
Compact bone
- Osteonthe Haversian system, the structural unit of compact bone, a set of tubes around a canal
- Central canalthe Haversian canal at the core of the osteon, carries blood vessels and nerves
- Perforating canalthe Volkmann canal that runs crosswise and links central canals
- Lamellaethe concentric rings of bony matrix around the central canal
- Lacunaesmall cavities between the lamellae, each holds one osteocyte
- Canaliculitiny channels that connect lacunae and let osteocytes exchange materials
Spongy bone
- Trabeculaethe open lattice of bony struts that forms spongy bone, aligned along lines of stress
- No osteonsspongy bone has no osteons, its spaces hold red marrow
The four bone cells
| Cell | What it does | Origin or fate |
|---|---|---|
| Osteogenic cell | divides to produce new osteoblasts | the stem cell of bone tissue |
| Osteoblast | builds and secretes new bone matrix | becomes an osteocyte once surrounded by matrix |
| Osteocyte | maintains the bone matrix day to day | a mature osteoblast, sitting in a lacuna |
| Osteoclast | breaks down and resorbs bone matrix | a large multinucleated cell from a blood-cell line, unlike the other three |
Bone Growth and Formation
This section follows the structures and the sequence: the two ways bone forms, the two ways it grows, and the ordered zones of the growth plate. The chemistry belongs to physiology and is not covered here.
Ossification, the two routes that form bone
| Route | What it builds | In brief |
|---|---|---|
| Intramembranous | the flat bones of the skull | bone forms directly within a connective tissue membrane |
| Endochondral | most bones of the body | bone replaces a hyaline cartilage model |
The two ways a long bone grows
The epiphyseal plate is the disc of hyaline cartilage where lengthening happens. When growth ends, the plate closes and leaves the epiphyseal line.
| Type of growth | Direction | Where it happens |
|---|---|---|
| Interstitial growth | the bone grows longer | at the epiphyseal plate |
| Appositional growth | the bone grows wider | at the outer surface, beneath the periosteum |
Zones of the growth plate
The five zones in order, from the epiphysis at the top to the diaphysis at the bottom.
- Zone of resting cartilageanchors the growth plate to the epiphysis
- Zone of proliferationchondrocytes divide and stack into columns
- Zone of hypertrophythe chondrocytes enlarge
- Zone of calcificationthe cartilage matrix calcifies
- Zone of ossificationcartilage is replaced by bone next to the diaphysis
See also: Histology: The Four Tissue Types, where bone and cartilage are introduced as connective tissues.
Study questions
Work on answering these in writing, in your own words. They are the questions to bring to class, and good practice for the reasoning the exams ask for.
- Use the parts of an osteon to explain how compact bone is organized.
- Compare compact and spongy bone by structure and where each is found in a long bone.
- Name the bone cell types and the job of each.
- Compare intramembranous and endochondral ossification by the tissue each starts from.
Step 2 . Retrieval check
Now explain it back, in your own words.
In 60 words or more, pull together what the video just taught you. Include the key concepts. This is the point where the learning actually sticks. After you submit, your spaced-recall cards for this topic unlock.