University:
Kentucky State University
Course:
BIO 301 | Human Anatomy
Academic year:

2024
Views:

418

Pages:

35
Author:

taluz6ib

Lecture title : Cartilage 1/4/2021 Cartilage Cartilage: is a specialized type of ✓ connective tissue designed to give support, bear weight and withstand tension, torsion and bending. Features of Cartilage Cartilage is avascular & is nourished by the diffusion of nutrients from capillaries in adjacent CT (perichondrium) or by synovial fluid (joint cavities). Chondrocytes exhibit low metabolic activity (as might be expected of cells in cartilage grows an avascular tissue) slowly. Cartilage has no lymphatic vessels or nerves. SHEET NOTE #1 Generally the connective tissue is vascularized tissue except : Dense regular connective tissue, as ligament tendons. Cartilage, because there is no blood vessels inside it. Cartilage and the epithelial tissue are avascular. There is two ways of cartilage nourishment : By the membrane that surround the cartilage which is called perichondrium. By the synovial fluid. The cartilage grows slowly because: It is an avascular. It cells (chondrocytes) have low metabolic activity. So when the cartilage is injured it won’t recover easily. Perichondrium Sheath of dense irregular CT surrounds cartilage in ✓ most places. It harbors the cartilage’s vascular supply, as well as ✓ nerves and lymphatic vessels. It has function in growth & repair. ✓ SHEET NOTE #2 Peri : around Chondrium : cartilage Chondrogenic : cells that produce cartilage cells. Perichondrium Outer (fibrous) layer rich in type I collagen fibers & contains numerous fibroblasts Inner (chondrogenic) layer Contain undifferentiated chondrogenic cells which can differentiate to chondroblasts SHEET NOTE #3 The inner layer of the perichondrium is called cellular layer Because it contains chondrogenic cells that form the cartilage cells. Components of Cartilage ECM Cells Chondroblasts Chondrocytes (embedded within lacunae) Fibers: Collagen & Elastic Ground substance High concentrations of GAGs and proteoglycans, which interact with collagen and elastic fibers SHEET NOTE #4 Chondroblasts are immature, active cells. Chondrocytes are mature cells, they are the inactive form of chondroblasts. Lacunae is the white space that surrounds the cartilage cells (chondrogenic). The cartilage is semi-solid. Two types of collagen are found in the cartilage: Collagen type I and type II.GAGs that are linked to proteins are called proteoglycans. Multiadhesive glycoproteins are also found in the cartilage in order to link the fibers with proteoglycans. The ECM of some cartilages is basophilic because of the high concentration of GAGs. Cells of Cartilage They are derived from undifferentiated mesenchymal cells ✓ Chondroblasts : Immature cells with branched cytoplasmic processes, they multiply to chondrocytes. Chondrocytes (older & mature cells) SHEET NOTE #5 Chondroblasts multiply to produce chondrocytes by Mitosis. The cell is called mature when: It loses the ability to divide by mitosis Its metabolic activity is low. The mature cartilage is the one that is in our bodies postnatal (after birth) , and the chondrocytes are shown clearly in it . The chondroblasts in the mature cartilage are shown on the sides of the perichondrium. Classification of Cartilage SHEET NOTE #6 NOTE : The classification of the cartilages is well explained in slides number 26,27,28. Hyaline Cartilage Most abundant type Homogeneous and semitransparent in the fresh state. Chondrocytes occur singly or in small, mitotically derived isogenous group. ECM rich in type II collagen & aggrecan complexes with bound water ✓ ✓ ✓ ✓ SHEET NOTE #7 The ECM in Hyaline cartilage is basophilic because of the high concentration of GAGs. The ECM is rich with aggrecan (proteoglycan). The most abundant component in Hyaline cartilage is : the ECM , cells. Most of Hyaline cartilages are surrounded by perichondrium cells. Territorial matrix (matrix around the cells) brighter and deep in color than other areas (rich in GAGs and poor in collagen). Isogenous aggregates groups of cells up to eight that originate from mitotic divisions of a single chondroblast Inter-territorial matrix (matrix between the cells) lightly colored matrix separated two groups of cells SHEET NOTE #8 The presence of isogenous aggregates shows the mitotic activity of a single chondroblast. Elastic Cartilage similar to hyaline cartilage ✓ except that it contains an abundant network of elastic fibers in addition to type II collagen fibers. Elastic fibers give fresh ✓ elastic cartilage a yellowish color SHEET NOTE #9 All Elastic cartilages are surrounded by perichondrium. Special stains must be used in order to see the elastic fibers. Fibrocartilage a combination of hyaline ✓ cartilage and dense CT with gradual transitions between these tissues. Chondrocytes occur singly ✓ & in aligned isogenous aggregates or they are very sparse. consists of small ✓ chondrocytes in a hyaline matrix, usually layered with larger areas of bundled type I collagen with scattered fibroblasts. SHEET NOTE #10 Fibrocartilage is mainly found in places of weight bearing. It’s the most strong cartilage (contains collagen type I). In fibrocartilage collagen type I is dominant while type II is found in few areas. There is no perichondrium surrounding the cartilage. Fibrocartilage Hyaline cartilage Elastic cartilage Main features of ECM Homogeneous, with type II collagen & aggrecan Darker elastic fibers, Type II collagen & aggrecan Large areas of dense CT, type I & II collagen Presence of perichondrium Yes (except at articular cartilage) Yes No Hyaline cartilage Elastic cartilage Fibrocartilage Major cells Chondrocytes, chondroblasts Chondrocytes, chondroblasts Chondrocytes, fibroblasts Typical arrangement of chondrocytes isolated or in small isogenous groups usually in small isogenous groups isolated or in isogenous groups arranged axially Provides flexible shape and support of soft tissues Provides cushioning, tensile strength, and resistance to tearing and compression Main functions Provides smooth, lowfriction surfaces in joints, structural support for respiratory tract Fibrocartilage Hyaline cartilage Elastic cartilage Main locations In the walls of larger .1 respiratory passages (nose, larynx, trachea, bronchi). articular ends of .2 movable joints In the ventral ends of .3 ribs, where they articulate with the sternum epiphyseal plates of .4 long bones fetal skeleton .5 1.Auricle of ear 2.external acoustic meatus 3.auditory tube (eustachian) 4.epiglottis & certain other laryngeal cartilages (cuneiforms ) intervertebral .1 discs pubic symphysis .2 3.meniscus (knee) 4.certain other joints (manubriosternal joint) 5. insertions of tendons Flexibility 2nd most flexible Most flexible Least flexible Special features Most abundant type ✓ Susceptible to ✓ calcification Strongest type ✓ SHEET NOTE #11 Most abundant type : Hyaline cartilage. Most flexible type : Elastic cartilage. Strongest type : Fibrocartilage. *some areas of Hyaline cartilage become clacified as we get older. Chondrogenesis (by which embryonic cartilage is formed) Mesenchyme is the precursor for all types of cartilage. Mitosis and early differentiation produces a tissue with condensations of rounded cells called chondroblasts. Chondroblasts are then separated from one another again by their production of various matrix components, which collectively swell with water and form the very extensive ECM. Multiplication of chondroblasts within the matrix gives rise to isogenous cell aggregates surrounded by a condensation of territorial matrix. SHEET NOTE #12 The cartilage in the embryo is formed at the center then outward. “from inner to outer area from where it was formed”. Interstitial Growth of cartilage “Growth from within” Occurs mainly in immature cartilage, limited in mature cartilage (articular cartilage & epiphyseal plate). It Rresulting from the mitotic division of preexisting chondroblasts in existing cartilage, divide & form small groups of cells “isogenous groups” which produce matrix to become separated from each other by a thin partition of matrix. Interstitial growth in the articular cartilage and epiphyseal plates of long bones is important in increasing the length of long bones during postnatal development. ✓ ✓ ✓ ✓ SHEET NOTE #13 The cartilage growth starts in embryo life and continues postnatal “after birth” life. There is two ways of cartilage growth: Interstitial growth. Appositional growth. - interstitial growth “from within”. occurs mainly in immature cartilage (as in embryo), limited in mature cartilage (postnatal life) in 2 places : articular cartilage, epiphyseal plate. This way of growth helps increasing the length of long bones from postnatal till puberty. Appositional growth of cartilage “Growth from outside” ✓ Occurs in mature & immature cartilage. ✓ it involves differentiation of new chondroblasts from the ✓ perichondrium Chondroblasts at the periphery of cartilage secrete matrix. ✓ Appositional growth of cartilage is more important during ✓ postnatal development. SHEET NOTE #14 Appositional growth “from outside”. From chondrogenic cells that are on the sides of the perichondrium. Occurs in embryo life and postnatal life , but it is more important in postnatal life. Appositional growth keeps happening even after puberty and that’s why our ears and noses keep growing as long as we’re alive.

Cartilage

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