Cartilage Flashcards
Cartilage composition
Cells - chondroblasts and chondrocytes (produced from chondroblasts - found in lacunae). In ECM. cartilages are avascular - chondrocytes get nutrients and O2 through diffusion through ECM.
Cartilage ECM
95%+ volume of cartilage. Lots of water in ECM, water binds to negatively charged glycoaminoglycans and proteoglycans. This allows for withstanding mechanical forces, and diffusion of nutrients and 02. This also limits the size that cartilage can grow.
Perichondrium
Essential for growth and maintenance of some of the cartilages. Fibroblasts are here. Blood vessels are here, nutrients diffuse from here to lacunae.
Appositional growth
Growth of addition to an existing surface- generation of new chondroblasts.
Interstitial growth
Growth by internal expansion - proliferation of chondrocytes and formation of isogenous groups.
Hyaline cartilage
Most common cart in human body. In fresh dissection, has a bluish white appearance. In histological sections, is purpleish (basophilic). 75% water, proteoglycans, hyaluronic acid, type II cartilage.
Located on articular surfaces - nose, larynx, tracheal rings, epiphyseal plates, fetal bone models.
Has perichondrium present - except for not around articular cartilage (too much pressure and friction on these surfaces).
Because high concentration of sulfated GAGs, binds basophilic hematoxylin, appearing basophilic. NOTE: Staining is not consistent. Collagen is not discernible here, collagen fibers have same refractive index as the surrounding structures, making them impossible to see.
Chondrocytes
More rounded and in groups typically.
Isogenous groups
When chondrocytes are growing, they go through mitosis, and form these. They are the clusters of cells. Overtime through interstitial growth, they get pushed further and further away from each other. Isogenous groups are early chondrocytes.
Interterritorial matrix
More basophilic (more gags) between lacunae. More collagen.
Territorial matrix
More basophilic (more gags) between lacunae. Between cells.
Elastic cartilage
Essentially the same as hyaline- type II collagen, but has elastin fibers as well. This makes the tissue more pliable. Sometimes the fibers get into lamellae. you can stain for elastic fibers.
Located: auricle, auditory cannal, auditory tube, epiglottis.
It has a perichondrium, and appears yellow in fresh dissection.
Tend to make VERY small isogneous groups.
Elastic cartilage - age
As it ages, it shrinks and is replaced with adipose.
Fibrocartilage
ECM composition - type I collagen, less proteoglycans.
Located in intervertebral discs, pubic symph, major tendon-bone anchorages. Places that undergo a lot of pulling forces. Good intermediate between dense connective tissue and cartilage. Classified as cartilage because their cells are chondrocytes (fewer amounts) sitting in lacunae. Tend to line up between collagen fibers.
NO perichondrium
Appearance - tissue intermediate between dense regular connective tissue and hyaline cartilage- chondrocytes arranged in long rows separated by coarse-collagen fibers. Acidophilic matrix.
Mesenchymal stem cell
Fibroblasts, bone cells, etc.
Bone shape
Long, flat, short, irregular, sesamoid.
Sesamoid
Specialized short bone - form in a tendon - the patella. Alters pull of the tendon
Spongy bone
has small spicules called trabeculae.
Long bone structure
diaphysis, epiphysis. Red marrow - replaced by yellow marrow over time.
Metaphysis
Flared portion of diaphysis - flares outward. Also, growth plate or epiphysial plate present. Hyaline cartilage growth plate allows for lengthening long bones.
lengthening long bones.
Hyaline cartilage growth plate allows for lengthening long bones. Epiphesial
Epiphyseal line
Formed from remnants of epiphyseal plates.
Long bone membranes
Perosteum, endosteum
Endosteum
Much thinner than perosteum. Lining inside of marrow cavity. LIned with osteoprogenitor cells, which bring about osteoblasts. You can also see osteoclasts (break down bone). This is very important for bone remodeling.
Perosteum
outer bone - tendons connect into the bone, hence why it has a fibrous portion.
Sharpey’s Fibers
Connects perosteum to bone.
Articular cartilage
Hyaline.
Irregular, short, flat, sesamoid
Spongy (diploe - trabeculae lined with endosteum) surrounded by compact bone. Perosteum on outside. Red marrow slowly filled with yellow marrow.
Cells
Osteogenic cell, osteoblasts, osteocytes, osteoclasts.
Osteogenic cell
Mesenchymal stem cells found in endosteum. Have the potential to divide by mitosis and differentiate into osteoblasts.
Osteoblasts
Lay down osteoid (type I collagen, inroganic portion of bone, and bnps - GAGs, hyaluronic acid). OSteocalcin - inportant in signalling for calcification of osteoid. Inorganic portion represents 50% of dry weight. Hydroxyapatite crystals a main part.
Responsible for synth and secretion of osteoid. Their activity signals for calcification of bone (inorganic portion). Found along surface of bone matrix. Will line up in a row, almost looking like a simple epithelium.
Osteocytes
Maintains bone tissue, sit in lacunae. They can live for many years. Has cytoplasmic extensions that go through canaliculi. Howshifts lacunae - not yet in haversian canal
Osteoclasts
Break down bone. Large, multinucleated mobile cell. Derived from same stem cells that produce macrophages. Formed from fusion of many monocytes. Has a ruffled border that approaches bone. Creates acidic environment near bone, breaking it down.
Signaling for calcification
Osteoblasts along surface- secrete type I collagen, glycoproteins, proteoglycans. They also secrete osteocalcin and glycoproteins that bind calcium (they start to bring in calcium). Also, release small matrix vesicles that contain alkaline phosphatase that hydrolyze phosphate ions from various macromolecules.
so, calcium goes up, phosphate goes up, these two get together around collagen fibers.
Canaliculi
Gap junctions between cells pass along nutrients through here.
Primary bone tissue (histologically different)
Woven bone or immature bone. First bone to develop. IT develops during embryonic dev, or during fracture repair. Lots of osteocytes here, random collagen fibers, lower mineral content, primary bone is temporary. Kinda random.
Secondary bone tissue
Lamellar bone or mature bone. Very well organized, because it is made up of osteons/haversions systems. Around each canal, there are lamellae. This is made up of bone matrix highly organized around central canal. Between each lamellae, we can find osteocytes sitting in lacunae.
Volkmann’s Canal
Haversians canal go parallel, volksmann’s canal go 90 degrees, connect blood to centers.
Osteon gpas
Gaps- old lamellae are still there and fill in the gaps between haversian systems. These are called interstitial lamellae.
Development of osteons
Perforating canal - osteoclasts that line endosteum start cutting through an offshoot of the perforating canal. This creates a space that the new osteon can fit in. Behind boring cone of osteoclasts are osteoprogender cells (give osteoblasts). These start lining outside, and start laying down one lamellae after the next. Occasionally, one gets stuck and becomes an osteocyte. Vascularization soon follows. Soon this space fills in.
Spongy bones
Does not have osteons - trabeculae surround red marrow tissue. Looks lamellar - just doesn’t have haversian system.