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Similar to 4.c.CARTILAGE&BONECT.pdf
4.c.CARTILAGE&BONECT.pdf
- 1. CARTILAGE & BONECT MUTALIFE F. MWEEMBA
- 2. Objectives By theend of this lecture, learners to be able to;
- 3. CARTILAGE is atough, flexible form of CT characterized by an extracellular matrix (ECM) with high concentrations of GAGs and proteoglycans, interact with collagen and elastic fibers. firm consistency allows it bear mechanical stress without permanent distortion
- 4. Function of cartilage It supports soft tissues Provides smooth articular surface at bone ends Structural support in special areas (trachea, pinna, Acts as shock absorber because of its resilience guides development and growth of long bones, both before and after birth
- 5. Cartilage cont.. Cells ◦Chondroblast & ◦ Chondrocytes embedded in extensive ECM ◦ Located in matrix cavities called lacuna ◦ Synthesise and maintain ECM ECM ◦ Collagen ◦ Hyaluronic acid ◦ proteoglycans
- 6. 3 types ofcartilage Hyaline -most common Elastic – more pliable and distensible Fibrocartilage - a substantial amount of collagen fibers cartilage is avascular, lack lymphatic vessels and nerves receives nutrients by diffusion from capillaries in adjacent CT (perichondrium) Perichondrium ◦ Sheath of dense CT surrounds cartilage except for articular cartilage ◦ Contains blood vessels, nerves , lymphatic vessels
- 7. Hyaline cartilage Characterisedby the presence of highly basophilic homogeneous matrix. Chondrocytes are isogenous in clusters Fresh is bluish-white and translucent has type II collagen chondrotin sulfates, keratan sulfate Found in embryo, costal cartilage, respiratory tract, articular surfaces, epiphyseal plate.
- 8. Elastic cartilage Characterisedby presence of abundant network of elastic fibres (elastin) elastic fibres are thinner at the periphery and thicker & branching in the interior of the cartilage collagen type II
- 9. Elastic Cartilage cont.. Sites; Auricle of ear cuneiform cartilage in the larynx Auditory (Eustachian) canal Epiglottis Similar to hyaline but abundant elastic fibers Yellowish in colour Has perichondrium No degeneration
- 10. Fibrocartilage Characterised bydense bundles of type 1 collagen fibers oriented in the direction of functional stress with rows of chondrocytes between the bundles. No perichondrium found in intervertebral discs, and in the pubic symphysis
- 11. Cartilage formation Allcartilage forms from embryonic mesenchyme in the process of chondrogenesis. The first indication of cell differentiation is the rounding up of the mesenchymal cells, which retract their extensions, multiply rapidly, and become more densely packed together. The dividing cells are typically called chondroblasts chondrocytes when proliferation has ceased both have basophilic cytoplasm rich in RER for collagen synthesis
- 12. Cartilage repair damagedcartilage undergoes slow and often incomplete repair, primarily by activity of cells in the perichondrium, which invade the injured area and produce new cartilage. In extensively damaged areas the perichondrium produces a scar of dense CT instead of forming new cartilage. The poor capacity of cartilage for repair or regeneration is due in part to the avascularity and low metabolic rate hyaline cartilage is susceptible to calcification during aging
- 13. Cartilage growth Uses2 processes 1. Interstitial growth the cartilage tissue enlarges both by, resulting from the mitotic division of deeply placed chondrocytes Interstitial growth in the articular cartilage and epiphyseal plates of long bones is important in increasing the length of long bones
- 15. Cont… 2. Appositional growthwhich involves differentiation of new chondroblasts from the perichondrium Appositional growth of cartilage is more important during postnatal development
- 16. BONETISSUE is aspecialized CT composed of mineralised (calcified) extracellular material, the bone matrix , and Has 3 major cell types It is highly vascular Metabolically very active It is not static but highly dynamic
- 17. Components the greatmajority of its cells are embedded in an extracellular matrix composed of organic materials (about 40% dry weight in mature bone) and inorganic salts rich in calcium and phosphate. ◦ confer the hardness and much of the rigidity of bone, and are the main reason that bone is easily seen on radiographs
- 18. Functions Mechanical support Protects vital organs Locomotion Metabolic reservoir –calcium, phosphates Bone marrow for haematopoiesis
- 19. Composition Supporting cells Organic component - collagen and GAGs Inorganic component - salt deposits ◦ Calcium hydroxyapatite, magnesium, sodium Remodeling cells
- 20. Supporting cells Osteoblasts Osteocytes Osteoclasts
- 22. Osteoblasts deposit collagentype I, proteoglycans and glycoproteins deposition of the inorganic component depends on the presence of viable osteoblasts Located on the surface of bone side by side like an simple epithelium Active cells are cuboidal or columnar with basophilic cytoplasm Reduced activity cells are flattened and less basophilic
- 23. Cont… Osteoblast thatget surrounded by matrix become osteocytes Found in cavities called lacuna Have cytoplasmic extensions extending into small channels called canaliculi Newly formed bone not yet calcified is known as osteoid Bone turnover more in children
- 24. Osteoid and bonematrix 90% collagen Defects in collagen may cause bone fragility Bone proteins osteocalcin, osteonectin have affinity for calcium Deposition may be regular pattern or haphazard Excess osteoid is seen in pathological conditions
- 25. osteocytes Derived from osteoblasts Found in lacuna One cell per lacuna Cytoplasmic extensions in canaliculi Contacts other cells by gap junctions Function: maintenance of bone matrix
- 26. osteoclasts Large multinucleatedcells 5 – 50 nuclei Found in areas of bone undergoing resorption, osteoclasts lie within enzymatically etched depressions or cavities in the matrix known as resorption cavities (Howship lacuna). Osteoclast stimulating factor are hormones from thyroid gland and parathyroid
- 28. Periosteum & Endosteum External and internal surfaces of bone are covered by tissue layers with bone forming cells, called periosteum & endosteum respectively. The outer layer is dense CT, with small blood vessels, collagen bundles, and fibroblasts. Bundles of periosteal collagen fibers, called perforating (Sharpey) fibers, penetrate the bone matrix, binding the periosteum to bone.
- 29. The innerregion of periosteum is a more cellular layer containing bone lining cells, osteoblasts, and mesenchymal stem cells called osteoprogenitor cells. With the potential to proliferate and differentiate into osteoblasts
- 30. Diseases of CT Osteogenesis imperfect: Mutation in gene responsible for collagen synthesis Ehlers Danlos syndrome genetic CT disorders characterised by hypermobility of joints Marfan’s syndrome: associated with mutation of gene responsible for fibrilin synthesis. Oedema is the excessive accumulation of water in the extracellular spaces of connective tissue
- 31. Marfan Syndrome Aninherited disorder caused by a defective gene for the glycoprotein fibrilin resulting in abnormal development of elastic fibers. This causes tissues that contain many elastic fibers to be malformed or weak including the covering of bone, ligament that suspends the lens of the eye, and the walls of large arteries People with Marfan syndrome are often tall, have long arms, legs, fingers and toes, blurred vision, and weakened aortic walls that may burst.
- 33. Activity Outline thetypes of CT. Differentiate between the types of CT Analyse the appearances of the CT Describe the functions of CT State the components of CT
- 34.