Cartilage And Bone Flashcards
What are the three types of cartilage and the GENERAL properties of each
Hyaline cartilage - forms a tissue which can form an articular surface on bones and which is strong enough to form structural components of the body, such as the C-shaped cartilage of the trachea or the septal cartilage of the nose.
Elastic cartilage - its composition allows it to be distended and recoil back to its original shape.
Fibrocartilage - its strength allows it to withstand compression force, making it suitable for joints which receive the weight of the body, such as the intervertebral discs and knee joints. It can act as a shock absorber.
Explain why cartilage is classified as a connective tissue
Cartilage is thought of as a connective tissue due to its structure and function. Structurally, cartilage is made up of cells, fibres and ground substance. Functionally, it connects tissues together, protects surfaces and forms structural components of the body.
Describe the cellular components of hyaline cartilage
The only cells type present in hyaline cartilage is the chondrocyte. They are derived from mesenchymal stem cells present in the perichondrium, appearing as flattened fibroblast-like cells. They migrate through appositional growth and form isogenous groups, growing then through interstitial growth. The function of these cells is to produce and maintain the cartilage matrix through secretion of ground substance and collagen. The chondrocytes occupy lucanae, which appear as shrinkage artefacts on slide preparations. The synthetic activity of the cells is induced by mechanical pressure application to the cartilage.
Describe the fibres of hyaline cartilage
The fibres present here are type II collagen.
Describe the make up of ground substance in hyaline cartilage
The ground substance here is made up of hyaloronic proteoglycan aggregates which, due to the hyaloronic acid, is highly hydrated. As such, nutrients can diffuse through matrix to reach chondrocytes.
Describe the healing capacity of cartilage and the underlying reasons for it
Cartilage does not heal very well due to its poor blood supply. This is a particular problem in things like osteoarthritis.
Describe the distribution and functional roles of hyaline cartilage.
Hyaline cartilage is notably present in the foetal skeleton, where it forms the precursor of long bones. It persists for a short time in life as the epiphyseal growths plates. It continues throughout adult life at articulating surfaces and in the trachea/bronchi for instance. It has a structural role in the airways and a role in long bone growth.
In a general sense, what is elastic cartilage?
Elastic cartilage is one of the three main cartilage types which is similar to hyaline cartilage in its make up, however is unique in that it contains abundant elastin fibres in order to give it differing properties of recoil. It exists in areas such as the epiglottis and pinna of the ear.
What is the perichondrium?
The perichondrium is a layer of dense connective tissue which surrounds elastic and hyaline cartilage, but is absent in articulating and fibrocartilage. It consists of two layers, the outer fibrous layer contains fibroblasts to generate collagen, the inner chondrogenic layer contains the chondroblasts/messenchymal stem cells which give rise to chondrocytes.
State some locations elastic cartilage and its role at each
Pinna of the ear - allows the structure of the ear to be maintains following deformation
Epiglottis - allows the structure to be returned to its original position following swallowing in which it covers the tracheal inlet
Eusacchian tube - returns the tube to the closed position following opening, mediated by salpingiopharyngeus muscle.
How do the components of fibrocartilage differ from that of elastic and hyaline cartilage?
Fibrocartilage is made up of type I collagen, as opposed to the type II of hyaline and elastic cartilage, and also contains both chondrocytes and fibroblasts, both of which produce and maintain the extracellular matrix of the cartilage. It can be thought of as a mixture of dense regular connective tissue (as in tendons in which type I collagen is organised in rows with fibroblasts sitting in lines) and hyaline cartilage with chondrocytes).
What is the function and distribution of fibrocartilage?
Fibrocartilage functions to withstand compression force and so is found in areas where a joint takes the wait of the body. For example, fibrocartilage makes up the minisci of the knee, intervertebral discs and pubic symphysis.
In general terms, describe the two types of bone
Bone can exist in two histological and macroscopic forms; compact/corticol/hard bone, or trabecular/spongy/cancellous bone. The former is much more dense, creating a strong margin of bone. The latter is more porous, containing within it bone marrow and reducing the weight of the bone.
Describe the structure/parts of a long bone in general
A bone consists of a central shaft called the diaphysis, which is flanked at each end by the epiphyses. The outer surface is coated with periosteum and the inner surface with endosteum. In the growing bone the junction between the diaphysis and epiphyses is lined with hyaline cartilage, called the epiphyseal growth plate. The articulating surfaces are coated with hyaline cartilage also, which does not have a perichondrium.
Microscopically, how is cortical bone structured?
Cortical/hard bone is made up of multiple concentric lamellae, which surround a single Haversian’s Canal, which transmits blood vessels and nerves. The entire structure is called an osteon. Linking such canals are Volkmann’s Canals. Between the lamellae are osteocytes, which are former osteoblasts which communicate with the Haversian’s Canals through canaliculi. Between the concentric lamellae are interstitial lamellae. These lamellae are remnants of previous concentric lamellae, replaced due to the continuous turnover of bone. The outer surface is lined with periosteum, the inner surface with endosteum.
