Not all tissues give rise to pain; furthermore, each tissue must be stimulated in an appropriate way to invoke its particular sensation of pain. The skin, being the outer covering of the body, easily raises the warning of pain, but other tissues that do… Plants Bryophytes liverworts, hornworts, and mosses are nonvascular plants; i.
In connective tissues cells typically account for only a small fraction of the tissue volume. The extracellular substance consists of fibres which are embedded in ground substance containing tissue fluid. Fibres in connective tissue can be divided into three types: Extracellular Substance Collagen fibres Collagen fibres are the dominant fibre type in most connective tissues.
The primary function of collagen fibres is to add strength to the connective tissue.
Longitudinal striations may be visible in thicker fibres. These striations reveal that the fibres are composed of thinner collagen fibrils 0. Each of these fibrils is composed of microfibrils, which are only visible using electron microscopy.
Microfibrils are assemblies of tropocollagen, which, in turn, is an spiral-like assembly of three Histology muscle and connective tissue molecules triple helix. The organisation of the tropocollagen within the microfibrils is highly regular. A small gap 60 nm wide is found between the subsequent tropocollagens which form the microfibrils.
Staining solutions used in electron microscopy tend to fill in these gaps, and the alignment of the gaps gives the microfibrils a cross-striated appearance with 68 nm intervals in EM images.
Coarse collagen fibres are formed by type I tropocollagen. There are many different tropocollagen types around currently named type I to XXI. These types differ in their content of the amino acids hydroxyproline and hydroxylysine.
They also differ in the amount of carbohydrates attached to the collagen molecules. The different types of tropocollagen give the fibres the structural and functional features which are appropriate for the organ in which the fibres are found.
Tropocollagen type IV is an important structural component of the basal lamina. Reticular fibres Reticular fibres are very delicate and form fine networks instead of thick bundles. They are usually not visible in histological sections but can be demonstrated by using special stains. For example, in silver stained sections reticular fibres look like fine, black threads - coarse collagen fibres appear reddish brown in the same type of preparation.
Because of their different staining characteristics, reticular fibres were initially thought to be completely different from collagen fibres. Cross-striations with the same periodicity as in coarse collagen fibres are however visible using electron microscopy. We now know that reticular fibres consist of collagen - although the main type of tropocollagen found in reticular fibres, type III, is different from that of the coarse collagen fibres.
Reticular fibres give support to individual cells, for example, in muscle and adipose tissue. They appear as fine black lines in this silver stained preparation. The fibres surround the individual sheets of liver cells hepatocytes and are the only fibrous connective tissue component supporting the cells.
While providing support, the fine, open meshwork of reticular fibres facilitates the exchange of substances between the hepatocytes and the blood, which circulates in the irregularly shaped blood vessels sinusoids between the hepatocytes. Reticular fibres are also present in the connective tissue surrounding the larger vessels, which penetrate the parenchyma of the liver.
Draw reticular fibres as they surround a nice piece of a row of liver cells at high magnification - include a suitable scale and label your drawing. Blood will not be visible in some types of preparations and the sinusoids appear empty.
Elastic fibres Elastic fibres are coloured in fresh tissues - they are light yellow - but this colouration is only visible if large amounts of elastic fibres are present in the tissue, for example, in the elastic ligaments of the vertebral column.
Special stains are necessary to show elastic fibres in tissue sections. Resorcin fuchsin is one of these stains, which gives the elastic fibres a dark violet colour.
Light microscopy does not reveal any substructure in the elastic fibres. Electron microscopy shows that elastic fibres consist of individual microfibrils, which are embedded in an amorphous matrix. Neither the elastin nor the microfibrils are collagens.The only tissues which perhaps could be confused with smooth muscle are dense regular connective tissues and peripheral nerves.
Both the number of nuclei and their shapes clearly distinguish smooth muscle from dense regular connective tissues.
skeletal muscle. transitional epithelium. simple columnar epithelium.
elastic cartilage. connective tissue. simple cuboidal epithelium. simple columnar epithelium. goblet cell. stratified squamous epithelium. erythrocytes. leukocytes. Histology Lab Photo Quiz. terms. BIOL Axial Skeleton Bones and Bony Landmarks.
20 terms. Jan 12, · In this episode of Crash Course Anatomy & Physiology, Hank gives you a brief history of histology and introduces you to the different types and functions of your body's tissues. Table of . Oct 07, · Deeper connective tissue which supports the mucosa is called the submucosa.
In the GI tract (but not in other tubular organs), there is a thin layer of smooth muscle, the muscularis mucosae, at the boundary between mucosa and submucosa. Additional Resources. These links will open a new browser window. Large Images Search the Large Images page with these keywords: dense irregular connective tissue, dense regular connective tissue, reticular connective tissue, mesenchymal connective tissue, white adipose tissue, brown adipose tissue, macrophage, adipocyte, mast cell .
Connective tissue (CT) is one of the four basic types of animal tissue, along with epithelial tissue, muscle tissue, and nervous leslutinsduphoenix.com develops from the leslutinsduphoenix.comtive tissue is found in between other tissues everywhere in the body, including the nervous leslutinsduphoenix.com the central nervous system, the three outer .