Histology of Bone and Cartilage Flashcards
_ is a flexible, deformable material that serves as resilient, smooth-gliding surface for the movement of our joints; cushions places where bone might rub against bone
Cartilage is a flexible, deformable material that serves as resilient, smooth-gliding surface for the movement of our joints; cushions places where bone might rub against bone
Bone is the rigid structural framework of our body but also serves to _, _ , _, _
Bone is the rigid structural framework of our body but also serves to
1. Store calcium
2. House bone marrow
3. Synthesize blood cells
4. Aid in the removal of toxins
Bones are divided into three regions:
- Diaphysis: center component
- Epiphysis: outer components
- Metaphysis: boarders the diaphysis
The _ functions as the main shaft of the bone; it is hollow and contains _ and _
The diaphysis functions as the main shaft of the bone
* It is hollow and contains nutrient arteries and yellow bone marrow (within the medullary cavity)
We have a distal and proximal _ at each end of the bone; the articular surface of these is covered with cartilage
We have a distal and proximal epiphysis at each end of the bone; the articular surface of these is covered with cartilage
The _ section of bone contains the cartilage growth plate in children, where bones will lengthen through adolescence
The metaphysis section of bone contains the cartilage growth plate in children, where bones will lengthen through adolescence
* The metaphysis is the interphase btwn epiphyses and diaphysis
The _ and _ regions of bone contain extensive networks of spongy bone
The epiphysis and metaphysis regions of bone contain extensive networks of spongy bone
The hard outer surface of the bone is covered by a dense membrane called _
The hard outer surface of the bone is covered by a dense membrane called periosteum
The interior surface of the bone is covered by a thin vascular layer called _
The interior surface of the bone is covered by a thin vascular layer called endosteum
Red bone marrow is the location of _
Red bone marrow is the location of blood cell production
Yellow bone marrow is the site for _
Yellow bone marrow is the site for fat storage and mesenchymal cells
* Mesenchymal cells are the precursors to bone, fat, cartilage, muscle cells
At birth, the whole skeleton is filled with only _ marrow
At birth, the whole skeleton is filled with only red bone marrow; as we age some of this gets converted to yellow marrow
In adults the red bone marrow is in _ and the yellow marrow is in _
In adults:
* Red marrow: epiphysis and metaphysis
* Yellow marrow: diaphysis
By the time we turn 25, red marrow is mostly in the axial skeleton and yellow marrow is in the diaphysis of long bones like the femur
Cartilage has a low metabolic rate and diminished healing ability; why?
Cartilage is avascular and receives most of its nutrients through diffusion
How is cartilage formed?
Mesenchymal cells differentiate into chondroblasts –> chondroblasts secrete the cartilage matrix and get trapped in lucunae –> once trapped they are now chondrocytes
What is the perichondrium?
Perichondrium is a dense outer layer surrounding the cartilage; it contains collagen and gives cartilage the ability to grow/repair
Recall that the three types of cartilage are _, _ , _
Recall that the three types of cartilage are hyaline, elastic, fibrocartilage
* Hyaline cartilage is most abundant
Hyaline cartilage is strong; its matrix consists of _ and _
Hyaline cartilage is strong; its matrix consists of chondroitin sulfate and type II collagen
Where do we find hyaline cartilage?
Hyaline cartilage
* Articular surfaces of joints = articular cartilage
* Trachea
* Bronchi
What does hyaline cartilage look like?
Hyaline cartilage has a glassy, smooth appearance
The matrix of elastic cartilage is composed of _ and _
The matrix of elastic cartilage is composed of type II collagen and chondroitin sulfate
* (Like hyaline cartilage) but also contains elastic fibers!
* Give it elasticity
Where do we find elastic cartilage?
Elastic cartilage:
* Pinnae of ear
* Epiglottis
* Nose
Fibrocartilage is specialized to resist _ and _ forces
Fibrocartilage is specialized to resist compressive and pulling forces
* Found in the meniscus, annulus fibrosis, pubic symphysis
What does fibrocartilage look like?
Fibrocartilage has abundant type I collagen –> fibrous appearance
* The chondrocytes in their lucunae seem to line up in distinct rows, interspersed with fibers
Our compact bone is known as _
Our compact bone is known as cortical bone
Our spongy or cancellous bone is known as _
Our spongy or cancellous bone is known as trabecular bone
Cortical bone lies in _ region of the bone
Cortical bone lies in outer regions and surface of the bone
* Makes up about 80% of bone mass
Trabecular bone can be found in _ region
Trabecular bone can be found as porous network of bone in the interior
* 20% bone mass
* Larger surface area than cortical bone
* Specialized functions; bone marrow occupies the spae between porous network
Where do we find osteoblasts, the cells that synthesize and mineralize bone?
Osteoblasts line the surface of bony trabeculae ; they are here to synthesize and mineralize bone
They also signal to the osteocytes to break down bone
Osteoblasts secrete components of the bony matrix, including _, _, _
Osteoblasts secrete components of the bony matrix, including:
1. Type I collagen
2. Osteopontin
3. Osteocalcin
When osteoblasts become entrapped in the bony matrix, they become _
When osteoblasts become entrapped in the bony matrix, they become osteocytes
* Osteocytes are the most numerous cell type
* They sit in the lacunae within bone
* Involved in the maintanance of bone
The osteoclasts break down and digest the bony matrix; they are found in _ region
The osteoclasts break down and digest the bony matrix; they are found on the surface of bone in little indentations called Howship lacunae
Howship lacunae house _ type cells
Howship lacunae house the osteoclasts
What do osteoclasts look like?
Osteoclasts are huge, multi-nucleated cells, found on the surface of bone
* Look for howship lacunae
After osteoclasts move around inside the bone and get stimulated to resorb bone by the osteoblasts, what do they do next?
- After osteoclasts move around inside the bone and get stimulated to resorb bone by the osteoblasts
- They seal off an area of bone surface –> secrete enzymes to dissolve that bone –> ingest remnants by phagocytosis
The functional unit of cortical bone is called the _
The functional unit of cortical bone is called the osteon
Osteons are several layers of _
Osteons are several layers of osteocytes that form a tree ring-like structure with intervening layers of bone matrix called lamellae
Lamellae wrap around the _ , a central canal that contains one-two capillaries
Lamellae wrap around the Haversian canal , a central canal that contains one-two capillaries
Haversian canals communicate with periosteal vessels via a perforating channel called _
Haversian canals communicate with periosteal vessels via a perforating channel called Volkmann canals
The bone matrix gets its tensile strength from _
It gets compressive strength through _
- The bone matrix gets its tensile strength from type I collagen (organic)
- It gets compressive strength through inorganic compounds like hydroxyapatite
_ are tiny “canals” where the cytoplasmic extensions of the osteocytes spread; they allow osteocytes to send chemical messages to each other
Canaliculi are tiny “canals” where the cytoplasmic extensions of the osteocytes spread; they allow osteocytes to send chemical messages to each other
What role do canaliculi play during remodeling?
During remodeling canaliculi enable the chemical messages from damaged tissue to lead osteoclasts to the site of damage
The general scheme of bone formation is an initial formation of _ , which forms the network for the deposition of _ to form the final bone
The general scheme of bone formation is an initial formation of extracellular matrix , which forms the network for the deposition of minerals (calcium, phosphate, magnesium) to form the final bone
* The ECM is made of type I collagen + other proteins like sialoprotein, osteocalcin, decorin
* Noncollagen proteins are essential for mineralization
Endochondral ossification is _
Endochondral ossification is formation of bone within cartilage
* It is how most long bones form
Intramembranous ossification is _
Intramembranous ossification is formation of bone directly from mesenchymal tissue
* How most cranial and flat bones form
What are the general steps of endochondral ossification?
Endochondral ossification:
1. Blood vessels in the perichondrium surround the cartilage model –> they bring osteoblasts in –> osteoblasts deposit the bone collar
2. The bone collar causes the chondrocytes to die (nutrients can’t diffuse) –> blood vessels penetrate the space + osteoblasts to form the primary ossification center; the perichondrium is now the periosteum
3. Bone invades the diaphysis –> cartilage between the diaphysis and epiphysis lengthens the bone
4. Secondary ossification centers form on the epiphyses
5. Remaining cartilage becomes articular cartilage; epiphyseal growth plate closes eventually (late adolescence)
Achondroplasia is an autosomal dominant inherited disorder that leads to abnormal _
Achondroplasia is an autosomal dominant inherited disorder that leads to abnormal endochondral ossification
* Long bones don’t develop properly
* Intramembranous ossification is normal –> head normal size
The primary ossification center forms in the _ region
The primary ossification center forms in the diaphysis region
The secondary ossification center forms in the _ region
The secondary ossification center forms in the epiphyses
_ are multipotent cells that can differentiate into several connective tissue types (osteoblasts, chondrocytes, myocytes, adipocytes)
Mesenchymal stem cells are multipotent cells that can differentiate into several connective tissue types (osteoblasts, chondrocytes, myocytes, adipocytes)
Most mesenchymal cells in adults are found in the _
Most mesenchymal cells in adults are found in the bone marrow and adipose tissue
What are the steps of intramembranous ossification?
Intramembranous ossification
1. Some mesenchymal cells differentiate into osteogenic cells (and capillaries) –> differentiate into osteoblasts and form clusters called ossification centers
2. Osteoblasts secrete osteoid and become entrapped –> now they are osteocytes
3. Clusters of osteoid unite to form a trabecular network around the capillaries; the superficial surface of trabecular bone forms periosteal layer containing osteoblasts
4. Periosteal layer creates compact bone layer
Osteoclasts come in to remodel bone; they will attach to the _ and secrete a variety of _
Osteoclasts come in to remodel bone; they will attach to the osteon and secrete a variety of collagenases
* Collagenases release calcium, phosphate, magnesium into the blood
_ is the hormone regulating osteoclast activity
Parathyroid hormone is the hormone regulating osteoclast activity
* Main stimulator of bone resorption
* Indirect stimulation (through osteoblasts)
PTH first stimulates _ to release signaling molecules called _ that will stimulate osteoclast activity
PTH first stimulates osteoblasts to release signaling molecules called RANK ligand that will stimulate osteoclast activity
Aside from RANK ligand, osteoclasts are also directly stimulated by _
Aside from RANK ligand, osteoclasts are also directly stimulated by interleukin 6 (IL-6)
* Important in osteoporosis pathology in women
Osteoclasts are repressed by _ and _
Osteoclasts are repressed by calcitonin and calcitriol
Primary hyperparathyroidism can lead to _
Primary hyperthyroidism is caused by overactive parathyroid gland that can lead to
* Hypercalcemia
* Bone fractures
