Cartilage - Sinai University Lecture Notes PDF

Dr. Mohamed Hassany Ali Lecturer in Cytology, Histology, and Genetics sinaiuniversity.net 1  Cartilage @Sinaiunieg [email protected] www.su.edu.eg 2 Characteristics of Cartilage: Cartilage is strong and sort of r...

Dr. Mohamed Hassany Ali Lecturer in Cytology, Histology, and Genetics sinaiuniversity.net 1  Cartilage @Sinaiunieg [email protected] www.su.edu.eg 2 Characteristics of Cartilage: Cartilage is strong and sort of rigid but also flexible. It can withstand force but it can also bend. Cartilage is avascular, it receives nutrition from the perichondrium. It’s made of cells (chondrogenic, chondroblasts and chondrocytes), fibers, and extracellular matrix. Forms the template for growth and development of long bones. Shock-absorbing. Smooth sliding surface for joints (for easy bone movement). Bone development and growth before and after birth. Cartilage Cells Chondrogenic cell: gives rise to chondroblast Chondroblasts differentiate into chondrocytes. It is responsible for formation of cartilage matrix and collagen II, give rise to chondrocyte. Chondrocytes are mature cartilage cells that lie in little in a capsule or space called lacunae. They can divide in cluster of cells formed of 2, 4, or 8 cells called cell nest. responsible for maintain cartilage matrix.  Cartilage Extracellular Matrix (ECM) Cartilage ECM is composed of: Collagen and/or elastic fibers Lots of GAGs and proteoglycans These substances make the ECM firm and resistant to mechanical forces.  Perichondrium Perichondrium covers the surface of hyaline and elastic cartilage (but not fibrocartilage). Outer fibrous layer: dense connective tissue composed of fibroblasts and type I collagen fibers. Contains blood vessels. Inner cellular layer: chondrogenic and chondroblasts. Cartilage is avascular. So what? Cartilage itself has no blood vessels or nerves in its extracellular matrix (bone is a different story). Nutrients must diffuse from perichrondrium through extracellular matrix to chondrocytes. This means metabolic activity is low, the width of cartilage is limited, and cartilage heals poorly. The fibers of the extracellular matrix determine the type of cartilage. Hyaline cartilage collagen fibers Type II collagen fibers Type II Elastic cartilage and elastic fibers Fibrocartilage collagen fibers Type I Hyaline cartilage Bluish-gray, semi translucent. Most common. Sites: 1.Fetal skeleton. 2.Epiphyseal plate. 3.Costal cartilage. 4.Articulating surfaces of moving joints. 5.Respiratory passages (noses, larynx, trachea, and bronchi). Functions: support soft tissue, line joints, growth of long bones.  Elastic cartilage Yellow color. Similar to hyaline cartilage, except that its matrix and perichondrium possess elastic fibers and small cell nests (2 cells groups). Sites 1. Ear pinna. 2. Eustachian tube. 3. Epiglottis and some laryngeal cartilage. 4. External auditory canal.  Fibrocartilage unlike hyaline and elastic cartilage, does not possess a perichondrium, and its matrix is very scanty and possesses type I collagen. Located in areas subjected to pulling forces Intervertebral discs, pubic symphysis, and attachments of tendons and ligaments.  Two Methods of Cartilage Formation Interstitial growth: growth from within cartilage. Chondrocytes divide and secrete matrix. Appositional growth: growth along the outside of cartilage. Chondroblasts secrete matrix and differentiate into chondrocytes. THANK YOU For any questions feel free to contact me by mail [email protected] Dr. Mohamed Hassany Ali Lecturer in Cell, Histology, and Genetics 13