Connective tissue proper
Ivan VARGA Institute of Histology and Embryology March 12, 2020 On-line documents for histology lectures: introductory notes Dear students, until now, it hasn´t been our custom to publish any of histology lectures in freely accessible on-line form on the website of our faculty and there has been a good reason for that. The most important elements of each one of the histology lectures are high quality schematic pictures, drawings and photomicrographs. The source of these didactic materials is commonly some internationally acceted textbooks, however, any further spread of these materials to wider public requires a consent from the publisher/copyright owner. Therefore, the lecture you will obtain is a version with significantly reduced number of figures. The only graphic materials I have been able to use come from a textbook which I co-authored, so I have the "copyright" to share them. Only other option has been to use free-access documents from the web. It is important to point out that any figure without proper commentary loses its educational value, so for the purpose of your self-study, I must refer to other textbooks we have written for you. Please feel free to contant me via an e-mail if you have any other queries. I hope, that the epidemiological situation will allow us to continue the in-person education as soon as possible, so we can get back to "classic" lectures followed by discussion, which represent the highest form of teaching and manifestation of creativity within the university education.
With best personal wishes, prof. RNDr. Ivan Varga, PhD. [email protected] www.fmed.uniba.sk/en/science/ Connective tissue
Consists of cells and extracellular matrix (fibers and ground substance), Classification : Connective tissue proper, Cartilage, Bone, Blood and lymf (as liquids) General characteristics
The cells are separated from one another, and have different types and functions, The fibers are collagen (strong and not elastic), elastic (strong and elastic), or reticular (create thin network). These fibers are products of cells Differences among types of connective tissue
Connective tissue proper: the matrix is either watery and soft, may be vascular Cartilage: the matrix is rubbery and firm, and is always avascular (without blood vessels) Bone: the matrix is hard and calcified, and is highly vascular, contain only collagen fibers Blood and lymf: liquid, no fibers Embryological basis: mesenchyme
Most originate from mesoderm (middle germ layer) In head and neck is derived from neuroectoderm (neural crest derived mesenchyme) Mesenchyme = embryonic connective tissue Eosinophil Basophil Neutrophil Osteoclast from bone Erythrocyte Osteocyte from bone Microglia from CNS Osteoblast
Chondrocyte Megakaryocyte B- lymphocyte Monocyte from cartilage Mesenchymal T- lymphocyte Mast cell stem cell Endothelial cells from blood vessel
Macrophage Plasma cell Fibroblast
Fibrocyte Multilocular and unilocular adipocytes Balko J, Tonar Z, Varga I. Memorix Histology. Prague: Triton 2018 Functions of connective tissue
Providing structural support Medium for exchange of metabolic waste, nutritionts and oxygen Defense and protection of the body (phagocytosis, antibodies, producing of pharmacological substances) Forming a site for storage of fat Structure of connective tissue proper
fixed
cells free cells connective tissue ground substance proper collagen fibers extracellular elastic fibers matrix fibers reticullar fibers Fixed cells of connective tissue
Are a resident population of long-lived cells They developed and remain in place within the connective tissue Include fibroblasts, adipose cells, reticular cells, pigment cells Fibroblasts and fibrocytes (or active and non-active form)
Most common cells in connective tissue, Irregular shape, basophilic cytoplasm with pale nucleus and prominent 2 nucleoli The old, non-active form are called fibrocytes with acidophilic cytoplasm and dark nuclei FIBROBLAST FIBROCYTE are two states of the same cells, the former being the activated state, the latter the less active state,
Non-active Active form ..
• the most common cells of connective tissue, • synthesizes the extracellular matrix and fibers, • plays a critical role in wound healing
Balko J, Tonar Z, Varga I. Memorix Histology. Prague: Triton 2018 Ultrastructure of fibroblasts
The cytoplasm is rich in organells responsible for protein synthesis (rough ER, Golgi apparatus, secretory granules, ...) The nucleus contains pale euchromatin and 1 or 2 nucleoli Ultrastructural features are indications of active protein synthesis Functions of fibroblasts -Produce all types of fibers (collagen, elastic and reticular) and the amorphous ground substance
3.5 milion molecules of tropocollagen / day Electron micrograph displaying a portion of a fibroblast and the packed collagen fibers in the dermis of skin
Boháč M et al. European Journal of Histochemistry 2018; volume 62:2873 Fibroblast cell culture
Fibroblasts grown under controlled conditions, generally outside of their natural environment – „in vitro“. Fibroblastic reticular cells Stroma of secondary lymphoid organs (spleen,lymph nodes) and hematopoietic bone marrow Manufacture reticular fibers
Balko J, Tonar Z, Varga I. Memorix Histology. Prague: Triton 2018 Spleen in scanning electron microscope Polák Š, Gálfiová P, Varga I.: Biologia. 2009; 64(2) Adipose cells (fat cells, adipocytes) - unilocular adipocytes
Fully differentiated cells Synthesis and storage of fat (lipids) Rounded in shape and full of large central droplet of fat surrounded by a very thin ring of cytoplasm Nucleus is peripheral and flattened Mesenchymal cell
Multilocular adipocytes Unilocular adipocyte Unilocular adipose cell contain single large central droplet of fat in their cytoplasm
Balko J, Tonar Z, Varga I. Memorix Histology. Prague: Triton 2018
Unilocular fat cells = white adipose tissue
„Type of apple“ „Type of pear“ Metabolic syndrome X
a disorder of energy utilization and storage, diagnosed by a co- occurrence of three out of five of the following medical conditions: • abdominal (central) obesity, • elevated blood pressure, • elevated fasting plasma glucose, • high serum triglycerides, • low high-density cholesterol (HDL) levels. Metabolic syndrome increases the Distribution of white fat risk of developing cardiovascular in male and female disease and diabetes Multilocular adipose cell contain numerous lipid droplets and abundant mitochondria
Smaller, more polygonal multiple small droplets in cytoplasm Contain more mitochondria Balko J, Tonar Z, Varga I. Memorix Histology. Only in childhood Multilocular adipose tissue (brown fat) – numerous mitochondria dispersed throughout the cell The higher number of (iron-containing) mitochondria, make it brown Distribution of brown adipose tissue
THERMOGENESIS
It is especially abundant in newborns and in hibernating mammals. Its primary function is to generate body heat in animals or newborns that do not shiver.
In newborn infants, brown fat makes up about 5% of the body mass. It is of great importance to avoid hypothermia!!! Brown adipose tissue in hibernating animals, e.g. marmot
Source: internet Free cells of connective tissue
Changing population of motile cells Enter the connective tissue from the blood and wander through its ground substance Free cells (transient or wandering)
Changing population of motile cells Enter the connective tissue from the blood and wander through its ground substance Originate mostly in the bone marow (from hemopoietic stem cell) Include mast cells, plasma cells, lymphoctes, macrophages and other leukocytes (white blood cells). leukocytes migrate from the blood stream to connective tissue - DIAPEDESIS Macrophages
Ingesting dead cells and cellular debris The first line of defense against infections Are derived from monocytes in blood
Balko J, Tonar Z, Varga I. Memorix Histology. Prague: Triton 2018 Macrophage in TEM Ilya Ilyich Mechnikov he discovered phagocytosis developed a theory that aging is caused by toxic bacteria in the gut and that lactic acid could prolong life. Based on this theory, he drank sour milk every day, Mechnikov's work on phagocytes won him the Nobel Prize in 1908. Macrophage Development and Distribution
System of phagocytic cells = mononuclear phagocyte cells Arise from common stem cell in the bone marrow, precursors are monocytes posses numerous lysosomes, are capable of phagocytosis Mononuclear phagocyte cells Stem cell in monocytes from macrophages in tissues bone marrow bloodstream or organs
Connective tissue proper – macrophages Liver – Kupffer cells Lungs – dust cells (alveolar macrophages) Placenta – Hoffbauer cells Thymus, spleen, lymphnode– different macrophages Nervous tissue, brain – microglia Bone – osteoclasts Skin – Langerhans cells Mast cells
oval or round cells, 20-30 μm in diameter, very rich in basophilic secretory granules they content heparin and histamine (contraction of smooth muscles, dilatation of blood capillaries, increase permeability of blood cappilaries - important in inflammantion) Mast cells and metachromatically staining
These granules are metachromatically stained with methylene blue (the granules stained purple) the granules changes the color of applied dye Clinical significance of mast cells Plasma cells
Rounded in shape with eccentric nucleus The condensed peripheral chromatine give the nucleus a clock-face appearance Develop from B-lymphocytes of the blood, produces antibodies (immune response) Plasma cell
Clock face nucleus
Balko J, Tonar Z, Varga I. Memorix Histology. Prague: Triton 2018 Source: internet Cooperation of cells of immune system
Monocyte Antibodies
Plasma cell Macrophage as antigen-presenting cell T- lymphocyte B- lymfocyte (helper)
Balko J, Tonar Z, Varga I. Memorix Histology. Prague: Triton 2018 Collagen fibers
Have mechanical importance They strongly resist a pulling force and they are flexible but not elastic Staining: aniline blue (part of trichrome staining) Collagen types – about 20 different types of collagen fibers are known Type I. – connective tissue proper, bone, dentin, cementum Type II. – in hyaline cartilage Type III. – reticular fibers Type IV. – lamina densa of the basal lamina Type V. – in the placenta Type VII. – attaching the basal lamina to the lamina reticularis Collagen fibers – collagen type I. (staining aniline blue) Elastic fibers :
composed of protein elastin and microfibrils, these fibers are highly elastic and may be streched up to 150% of their resting lenght, in the walls of some blood vessels we can find not only fibers, but nonfibrillar form as fenestrated membranes, elastic fibers stained brown or red with orcein staining Elastic fibers in arteries and lungs Elastic mambranes in aorta (orcein - staining) Reticular fibers
They cannot seen by H-E stain, they appear black by silver staining (impregnation methods, argyrofilic = affinity for silver salts) Are thin collagen fibers type III Form delicate network in lymphatic and endocrine organs Reticular fibers in lymph node (impregnation by silver salts) Intercellular ground substance
is highly hydrated, complex mixture of glycosaminoglycans, proteoglycans and glycoproteins, the substance is colorless and transparent Types of connective tissue proper
Loose connective tissue
Collagen regular Dense connective tissue irregular Elastic connective tissue
Reticular connective tissue
Mucous tissue White adipose tissue
Adipose tissue Brown adipose tissue Loose (areolar) connective tissue
Most common cells are fibroblasts, collagen fibers are most prominent loose connective tissue
Source: Gray´s Anatomy Dense regular connective tissue
Collagen fibers are arranged in a regular parallel pattern The cells found are tendo fibrocytes with minimal matrix Can withstand stretch in one direction
Balko J, Tonar Z, Varga I. Memorix Histology. Prague: Triton 2018 Dense irregular connective tissue
The collagen fibers are arranged in an arregular pattern There is little ground substance and the cells are mainly fibroblasts Can withstand stretch from several different directions
Balko J, Tonar Z, Varga I. Memorix Histology. Prague: Triton 2018 Mucous connective tissue
Abundant ground substance and fine collagen fibers It is found in the umbilical cord (as Wharton´s jelly)
Source: internet Adipose connective tissue
Dominated by fat cells White adipose tissue is widely distributed in the body Fat cells contain large fat droplet which occupies most of the cytoplams Primary site of fat metabolism Thank You !