Cartilage

Question 1

Cartilage composition

Answer 1

Cells - chondroblasts and chondrocytes (produced from chondroblasts - found in lacunae). In ECM. cartilages are avascular - chondrocytes get nutrients and O2 through diffusion through ECM.

Question 2

Cartilage ECM

Answer 2

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.

Question 3

Perichondrium

Answer 3

Essential for growth and maintenance of some of the cartilages. Fibroblasts are here. Blood vessels are here, nutrients diffuse from here to lacunae.

Question 4

Appositional growth

Answer 4

Growth of addition to an existing surface- generation of new chondroblasts.

Question 5

Interstitial growth

Answer 5

Growth by internal expansion - proliferation of chondrocytes and formation of isogenous groups.

Question 6

Hyaline cartilage

Answer 6

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.

Question 7

Chondrocytes

Answer 7

More rounded and in groups typically.

Question 8

Isogenous groups

Answer 8

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.

Question 9

Interterritorial matrix

Answer 9

More basophilic (more gags) between lacunae. More collagen.

Question 10

Territorial matrix

Answer 10

More basophilic (more gags) between lacunae. Between cells.

Question 11

Elastic cartilage

Answer 11

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.

Question 12

Elastic cartilage - age

Answer 12

As it ages, it shrinks and is replaced with adipose.

Question 13

Fibrocartilage

Answer 13

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.

Question 14

Mesenchymal stem cell

Answer 14

Fibroblasts, bone cells, etc.

Question 15

Bone shape

Answer 15

Long, flat, short, irregular, sesamoid.

Question 16

Sesamoid

Answer 16

Specialized short bone - form in a tendon - the patella. Alters pull of the tendon

Question 17

Spongy bone

Answer 17

has small spicules called trabeculae.

Question 18

Long bone structure

Answer 18

diaphysis, epiphysis. Red marrow - replaced by yellow marrow over time.

Question 19

Metaphysis

Answer 19

Flared portion of diaphysis - flares outward. Also, growth plate or epiphysial plate present. Hyaline cartilage growth plate allows for lengthening long bones.

Question 20

lengthening long bones.

Answer 20

Hyaline cartilage growth plate allows for lengthening long bones. Epiphesial

Question 21

Epiphyseal line

Answer 21

Formed from remnants of epiphyseal plates.

Question 22

Long bone membranes

Answer 22

Perosteum, endosteum

Question 23

Endosteum

Answer 23

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.

Question 24

Perosteum

Answer 24

outer bone - tendons connect into the bone, hence why it has a fibrous portion.

Question 25

Sharpey’s Fibers

Answer 25

Connects perosteum to bone.

Question 26

Articular cartilage

Answer 26

Hyaline.

Question 27

Irregular, short, flat, sesamoid

Answer 27

Spongy (diploe - trabeculae lined with endosteum) surrounded by compact bone. Perosteum on outside. Red marrow slowly filled with yellow marrow.

Question 28

Cells

Answer 28

Osteogenic cell, osteoblasts, osteocytes, osteoclasts.

Question 29

Osteogenic cell

Answer 29

Mesenchymal stem cells found in endosteum. Have the potential to divide by mitosis and differentiate into osteoblasts.

Question 30

Osteoblasts

Answer 30

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.

Question 31

Osteocytes

Answer 31

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

Question 32

Osteoclasts

Answer 32

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.

Question 33

Signaling for calcification

Answer 33

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.

Question 34

Canaliculi

Answer 34

Gap junctions between cells pass along nutrients through here.

Question 35

Primary bone tissue (histologically different)

Answer 35

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.

Question 36

Secondary bone tissue

Answer 36

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.

Question 37

Volkmann’s Canal

Answer 37

Haversians canal go parallel, volksmann’s canal go 90 degrees, connect blood to centers.

Question 38

Osteon gpas

Answer 38

Gaps- old lamellae are still there and fill in the gaps between haversian systems. These are called interstitial lamellae.

Question 39

Development of osteons

Answer 39

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.

Question 40

Spongy bones

Answer 40

Does not have osteons - trabeculae surround red marrow tissue. Looks lamellar - just doesn’t have haversian system.