Dr. Archana Rani Associate Professor Department of Anatomy KGMU UP, Lucknow

CARTILAGE Modified connective tissue Forms skeletal basis of some parts of body Matrix is firm giving it the characteristic consistency Resists compression Avascular (nutrients diffuse through matrix) Perichondrium is rich in blood vessels

PERICHONDRIUM Dense irregularly arranged fibrous tissue Ensheaths the cartilage Composed of cells & matrix Matrix consists of fibres & ground substance Houses the blood vessels that nourish chondrocytes Present in most of the hyaline & elastic cartilage Absent in fibrocartilage Fibrous layer Cellular layer

CHONDROBLAST Mesenchymal (embryologically) Progenitor of chondrocytes Lines border between perichondrium and matrix Produce the intercellular matrix and collagen fibres Cells which become imprisoned within this matrix become chondrocytes.

CHONDROCYTE Mature cartilage cell Reside in a space called the lacuna Isogenous cell group Basophilic Clear areas = Golgi and lipid droplets

CHONDROCYTE Chondrocytes completely fill their lacunae RER and euchromatic nuclei Synthetically active, secrete matrix Synthesize type II collagen, proteoglycans and chondronectin. Cartilage matrix RER N

MATRIX Provides the rigidity, elasticity, & resilience FIBERS Collagenous and elastic GROUND SUBSTANCE Glycosaminoglycans (chondroitin sulfates & keratan sulfate) Proteoglycans Water Basophilic Territorial matrix Interterritorial matrix

CARTILAGE GROWTH Interstitial Newly formed cartilage grows by multiplication of cells throughout its substance. Appositional Addition of new cartilage over the surface of existing cartilage.

TYPES OF CARTILAGE HYALINE ELASTIC FIBROUS

CARTILAGE: LOCATIONS

HYALINE CARTILAGE  Sites: Tracheal rings, nasal septum, larynx, costal cartilage & articular surfaces of joints Cartilage cells: Present singly or in groups of 2 or 4 cells inside lacunae Cartilage Matrix: Collagen type II Ground substance: Homogenous, clearly basophilic Functions: supportive

ELASTIC CARTILAGE  Sites: Auricle, ext. auditory meatus, auditory tube, epiglottis, apices of arytenoid cartilage Cartilage cells: larger, more numerous, packed more closely Cartilage Matrix: elastic fibres, c ollagen type II Ground substance: Rich in elastic fibres Functions: supportive with resilience Elastic fibers stain with orcein.

FIBROCARTILAGE  Sites: intervertebral discs, arytenoid cartilage (except apices), pubic symphysis, manubriosternal joint, articular disc of TM joint.  Cartilage cells: fewer, smaller, scattered singly or in rows Cartilage Matrix: c ollagen type I & II Ground substance: acidophilic Functions: supportive with tensile strength Intervertebral disc

Clinical application Osteoarthritis Pseudoachondroplasia

bonE Modified connective tissue Highly vascular mineralized connective tissue consisting of cells and dense intercellular organic matrix impregnated with inorganic salts. Provide support & protection to the vital organs Forms skeletal framework

Articular cartilage Spongy bone Marrow cavity Compact bone (location of haversian systems) Periosteum

Composition Cells: a. Osteogenic cells b. Osteoblasts c. Osteocytes d. Osteoclasts Fibers: collagen type I Ground Substance: Proteoglycans & glycoproteins

The matrix of bone is a mixture of organic (collagen) and inorganic (calcium phosphate) 90% of bone is matrix, with the remaining 10% made of osteocytes.

Microscopic Anatomy of Bone Figure 5.3

Lamellar arrangement Slide 5.11a  Lamellae  Rings around the central canal  Sites of lacunae  Lacunae  Cavities containing bone cells (osteocytes)  Arranged in concentric rings Figure 5.3

Slide 5.11b  Canaliculi  Tiny canals  Radiate from the central canal to lacunae  Form a transport system Figure 5.3 Lamellar arrangement

compact bone The morphofunctional unit of the bone is osteon, or Haversian system. Lamellar pattern of compact bone: i. Haversian system ii. Interstitial lamellae iii. Circumferential lamellae

T.S. through compact bone ‘Haversian Systems’

Dark spots are called ‘lacunae’ and would contain osteocytes in living bone Central canal containing an artery, vein, lymph vessel and nerves

What happens when excessive bending force compresses the bone…! compressioncompression force

Clinical application Scurvy Rickets Osteomalacia Osteoporosis Osteogenesis imperfecta Pseudoachondroplasia

Save your bones

Take home message Aerobic exercises Low impact, weight bearing exercises Resistance exercises

References 1. diFiore’s Atlas of Histology with functional Correlations, 12 th Edition. 2. Essentials of Anatomy for Dentistry Students,1 st Edition. 3. Textbook of Histology, 3 rd Edition.

MCQ Fibrous cartilage is present in: 1. Auricle 2. Nose 3. Tracheal rings 4. Intervertebral discs

Label the following A B C Don’t confuse this picture with the Liver Lobule!

MCQ Elastic cartilage is present in: 1. Apices of arytenoid cartilage 2. Epiphysis 3. Tracheal rings 4. Temporomandibular joints

MCQ Hyaline cartilage is present in: 1. Tracheal rings 2. External auditory meatus 3. Semilunar cartilages of knee joint 4. Intervertebral discs

MCQ The blood vessels and nerves go inside the compact bone through: 1. Haversian canal 2. Volkman’s canal 3. Canaliculi 4. Interstitial lamellae