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Where do I find standard tissue and cell names?

Where do I find standard tissue and cell names?


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I am developing specialized database on some desease microarray experiments. The initial data is retreived from NCBI and ArrayExpress databases. The problem is that sample attributes sometimes specify similar or same things but in different manners: as cell and tissue names, desease names, age, ethnicity of donor, ect. Where do I find conventions for naming experiment sample attributes?


It turns out that ArrayExpress itself uses various ontologies (dictionaries structured as trees) available at Ontology Lookup Service when it processes users' search queries. Experimental Factor Ontology is the precisely one I was searching for.

Medical Subject Headings (MeSH) dictionary turned out to be handy as well.


Learning Objectives

Slide 239 Ovary, monkey H&E View Virtual Slide
Slide 065-1 Spinal cord, cross section Masson View Virtual Slide

Due to their size and the limited resolution of light microscopy, most cellular organelles are not visible or their detailed structure can't be studies in regular stained tissue sections. The major exception is the cell nucleus of all nucleated cells. This is mainly due to its size and to its content, as nucleic acids are highly basophilic. In larger cells, such as oocytes and many neurons, additional details and substructures of nuclei can be analyzed by light microscopy. Look in the following two slides for Oocytes in the ovary: slide 239 Oocytes View Image, slide 239 Oocytes View Image and for large motor neuron cell bodies in slide 065-1 grey matter of the ventral horn View Image and in slide 065-1 dorsal root ganglia View Image . Find large nuclei and study the distribution of euchromatin and heterochromatin. Note that due to the overall size of these cells, the nucleus may not always be in the plane of sections. In some nuclei you may also be able to detect an intensely stained basophilic nucleolus.


How to graph or plot MTT assay data - (Jan/01/2013 )

I will say what I would do if I were u
for % of viability I calculate it as abs of test divide by abs of control (no treatment) X100
(get average of Abs for test repeats in ur exp / by average abs of repeats of control)
Each experiment should be repeated 2-3 times at different days or more, so I would calculate STD from my these repeats ( if I do the experiment 3 times) I would calculate % of vaibility for each time as previously mentioned then calculate standard deviation or Standard error for these 3 times,
the i guess X axis would be log conc, and Y axis would be % of viability..
This I would do if I were u

I would also appreciate some help with this. I do MTS assays to measure the activity of certain compounds. I do each trial with 4 replicates for each group and then normalize the abs of each well with the average abs of the control. After that I calculate the average and standard deviation for each group. I then repeated the experiment 2 more times for a total of three trials, but now I end up with three averages (each having a standard deviation) and I can't figure out the proper way to calculate the final average and standard deviation. I have tried various search terms in google and could not find anything that match exactly with what I need.

For example, the data that I got for drug A at a certain concentration is (data are % of control): Trial 1: mean = 90 , SD= 5 Trial 2: mean = 94, SD = 4 Trial 3: mean = 89, SD = 3. How do I calculate the overall mean and standard deviation of these values?

I was told that I can just propagate the errors of each trial. Is this OK to do?

It would be a lot easier if I could just average the abs for each treatment group, normalize to the control and calculate the average and SD of the three trials, but what happens to the error associated with the abs of the replicated wells?

Would greatly appreciate a response if anyone has any experience with this type of calculation.

Ms VV on Wed Mar 6 01:47:17 2013 said:

Arrange the data into an ANOVA table this will separate the error into within-trial and between-trial components (many text books use the term blocks to represent the different trials you performed).
Chances are that there will be no significant difference between the trials and you will be able to treat them as a single average and standard deviation as you suggested but it never hurts to check.

Hi DRT, thank you for responding! Just to clarify, your suggestion is to enter the % viability of each well for each trial and do an ANOVA to test for statistical significant differences? So I should enter the data as follows?

Trial 1 Trial 2 Trial 3
% well 1 % well 1 % well 1
% well 2 % well 2 % well 2
% well 3 % well 3 % well 3
% well 4 % well 4 % well 4

If there are no significant differences, then I can just use all the values to calculate one average and standard deviation?

That seems correct, most software will want the results in a single column with a tag denoting which trial in an adjacent column.

Ms VV on Wed Mar 6 01:47:17 2013 said:

I would also appreciate some help with this. I do MTS assays to measure the activity of certain compounds. I do each trial with 4 replicates for each group and then normalize the abs of each well with the average abs of the control. After that I calculate the average and standard deviation for each group. I then repeated the experiment 2 more times for a total of three trials, but now I end up with three averages (each having a standard deviation) and I can't figure out the proper way to calculate the final average and standard deviation. I have tried various search terms in google and could not find anything that match exactly with what I need.

For example, the data that I got for drug A at a certain concentration is (data are % of control): Trial 1: mean = 90 , SD= 5 Trial 2: mean = 94, SD = 4 Trial 3: mean = 89, SD = 3. How do I calculate the overall mean and standard deviation of these values?

I was told that I can just propagate the errors of each trial. Is this OK to do?

It would be a lot easier if I could just average the abs for each treatment group, normalize to the control and calculate the average and SD of the three trials, but what happens to the error associated with the abs of the replicated wells?

Would greatly appreciate a response if anyone has any experience with this type of calculation.

Just a quick question. When you do your MTS assay do you use 96wells plates. If yes, do you change the media everyday. I find out that in 72hrs the media only wells are almost empty. I would love any tips as this is my first time with this type of experiment. Thanks

Thanks DRT! I'll try that and see.

Hi Peniel! Yes, I use 96 well plates. I usually incubate for 48 h without replacing the medium and have no noticeable decrease in volume by looking at the wells. There is a decrease of 0.1-0.2 mL when measured. I incubated a few times for 72 h and also did not noticed a big decrease in volume. I use 0.1 mL per well. The wells could hold up to 0.3 mL, maybe you could use a higher volume if you are not already doing so. Sorry, I don't really have any suggestions other since I haven't had that issue.

Peniel on Fri Mar 8 11:01:42 2013 said:

Just a quick question. When you do your MTS assay do you use 96wells plates. If yes, do you change the media everyday. I find out that in 72hrs the media only wells are almost empty. I would love any tips as this is my first time with this type of experiment. Thanks

A problem with the humidity levels in the incubator?
Are all your media controls in a row along one side? Be wary of always running your experiments in the same direction across a plate. In theory it shouldn't make a difference and all wells are identical but there is always the potential for biasing the results.

DRT on Sun Mar 10 18:57:10 2013 said:

and keep in mind the "edge effect" (higher evaporation at the edges of well plates)


Where do I find standard tissue and cell names? - Biology

OBJECTIVES: At the end of this laboratory you should be able to:

1. Distinguish the connective tissues from all epithelial tissues on the basis of location, cell density and the presence of discrete fibers.

2. Distinguish between loose irregular (areolar), dense irregular, or dense regular connective tissues on the basis of fiber packing and orientation.

3. Identify, at the light and electron microscopic levels, collagen, reticular, and elastic fibers.

4. Identify and list the cell types found in the various kinds of general connective tissues, and describe their origins and functions.

SLIDES FOR THIS LABORATORY: 2, 13, 14, 40, 43, 47, 49, 51, 67, 68, 72, 79, 80, 89, 92 and 93.

The common fiber types include collagen, elastic, and reticular.

Slide 43 Thick Skin, Sole of the Foot

Collagen fibers (typically type I collagen) are acidophilic when stained with H & E, as seen in the dermis of skin . They tend to have a wavy appearance and may be sectioned obliquely, transversely or longitudinally. Nuclei of fibroblasts (fibrocytes) are numerous among the collagen fibers.

Again note the wavy collagen fibers of the dermis in this slide of thick skin.

Slide 47 Submaxillary Gland, Verhoeff's Hematoxylin.

Elastic fibers stain black with Verhoeff's Hematoxylin and are seen as branching black lines. In this slide, the elastic fibers are clearly visible around ducts and vessels (collagen fibers are green).

Slide 93 Connective Tissue Spread, Verhoeff Van Gieson, Toluidine Blue.

Both elastic and collagen fibers and various connective tissue cells are visible in this preparation. Verhoeff's Hematoxylin stains elastic fibers black and Van Gieson stains collagen acidophilic. In your slide the acidophilic collagen fibers may not be obvious. Mast cells are easily identified due to the metachromasia of granules with toluidine blue.

Reticular fibers (type III collagen) are thin collagen fibers not typically detected with routine H & E staining. However, these fibers stain black with silver stain and are often called argyrophilic fibers . The spleen demonstrates the supportive network of reticular fibers present in many organs. In this slide, the delicate reticular fibers are black and the thick collagen fibers are red/brown.

Slide 89 Human Liver, Acid Fuchsin (Van Gieson method) and Silver.

This slide demonstrates both collagen (red) and reticular (black) fibers.

The common cell types in connective tissue include: fibroblasts, mast cells, plasma cells, macrophages, adipocytes, and leukocytes.

Fibroblasts are the most common cell type of connective tissue. They produce both fibers and amorphous ground substance. Typically only the oval nuclei are visible. These cells are found associated with the fibers listed above. In the tendon, fibroblasts are seen as elongate nuclei found sandwiched between collagen fibers .

Mast Cells are round/oval cells that contain granules that are metachromatic because of their glycosaminoglycan content these cells are easily seen in the connective tissue spread. The toluidine blue component of the stain applied to this slide renders the mast cell granules blue-purple.

Examine the lamina propria underlying the epithelium of the pyloric stomach to find plasma cells . The cells are ovoid with basophilic cytoplasm, due to rER. The diagnostic feature of plasma cells is their eccentric round nuclei commonly described as "clock face" nuclei . This appearance is due to heterochromatin clumps. These cells are readily identified in the mucosa of the digestive tract.

In the lung, alveolar macrophages (dust cells) are found easily in the air spaces where these cells have either ingested carbon particles or erythrocytes. Some may appear as vacuolated cells. One can infer the identity of a macrophage by its indented nucleus . Macrophages are phagocytic cells that are difficult to find in normal tissues because there is not sufficient cause for them to increase in number.

Adipocytes , fat cells are large cells specialized in storage of neutral fats. Lipid is removed in routine tissue preparation. Consequently the cell appears as a thin rim of cytoplasm surrounding the vacuole of dissolved lipid. The nucleus is eccentric and flattened. Adipose tissue is a connective tissue with a predominance of adipocytes.

Slide 2 Peripheral Nerve, Osmium Tetroxide.

Lipid is preserved and stained black when the tissue is prepared using osmium tetroxide as a fixative.

Leukocytes are white blood cells that are readily found in connective tissue. Lymphocytes (similar in size to red blood cells) are the most common connective tissue leukocyte. Aggregates of lymphocytes are often found associated with the mucosal epithelium of the GI tract, such as this slide of the esophagus. They have a small amount of slightly basophilic cytoplasm and a large, darkly stained nucleus because of condensed chromatin. Use Slide 51 (pyloric stomach) to compare lymphocytes (no visible cytoplasm) to plasma cells which contain abundant cytoplasm.

Observe the eosinophils surrounding the large duct in the center of this slide. These cells are another type of leukocyte that are identified by their bilobed nucleus and refractile specific granules that are stained by eosin.

TYPES OF CONNECTIVE TISSUE

Connective tissue can be classified as either connective tissue proper or specialized connective tissue. Connective tissue proper includes: loose connective tissue (also called areolar) and dense (irregular) connective tissue. Specialized connective tissue types include: dense regular connective tissue, cartilage, bone, adipose tissue, blood, and hematopoietic tissue. The majority of specialized connective tissues will be studied in future laboratories.

Loose connective tissue (areolar) is located under the thick eosinophilic basement membrane of the respiratory epithelium in the trachea. A major component of loose connective tissue is amorphous ground substance which does not stain with routine H & E. The most numerous cell types are fibroblasts . In addition, other fibers such as collagen, elastic, and reticular fibers are present. Also, look for this type of connective tissue surrounding blood vessels and underlying the epithelium of the digestive tract.

Slide 43 Thick Skin, Sole of the Foot.

Loose connective tissue (areolar) is located directly beneath the epidermis of the skin. Dense irregular connective tissue forms most of the dermis below the loose connective tissue. Dense irregular connective tissue has similar components as loose connective tissue. However, the collagen fibers predominate and there are fewer cells and less amorphous ground substance. The collagen is arranged in bundles without any specific orientation.

Dense regular connective tissue has collagen fibers arranged in a definite pattern according to the direction of stress. The tendon clearly shows this arrangement.


Main Types of Animal Tissues


Collection of organized cells that work towards a specific function to a complete organ can be known as a tissue. There are 4 types of main animal tissues inside our bodies. They are,

However, this post will explain only the blood, muscle and epithelial tissues in detail. Here are few interesting facts about these 4 animal tissues.

  • Your blood is a liquid tissue.
  • 40% of an animal’s weight is coming from muscle tissue.
  • Muscle tissue has the ability of contraction.
  • Internal and external surface covering layer is known as epithelial tissue.
  • Nerve tissue is made by nerves or nerve cells.
  • Nerve cells carry the nervous impulses.

Cell migration: Fibroblasts find a new way to get ahead

Fibroblasts migrate on two-dimensional (2D) surfaces by forming lamellipodia—actin-rich extensions at the leading edge of the cell that have been well characterized. In this issue, Petrie et al. (2012. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201201124) show that in some 3D environments, including tissue explants, fibroblasts project different structures, termed lobopodia, at the leading edge. Lobopodia still assemble focal adhesions however, similar to membrane blebs, they are driven by actomyosin contraction and do not accumulate active Rac, Cdc42, and phosphatidylinositol 3-kinases.

In 1970, Abercrombie et al. published a series of papers on “The locomotion of fibroblasts in culture” (Abercrombie et al., 1970a,b,c Kardash et al., 2010). By filming fibroblasts migrating on serum-coated coverslips, they described the multistep model of lamellipodia-based cell migration. This work has shaped the field of cell migration for the last 40 yr, and despite many open questions, we now have a solid conceptual framework for how the lamellipodium drives cell motility: Actin filaments polymerizing below the leading plasma membrane generate the pushing force required for protrusion. As the tension of the plasma membrane opposes the free anterograde expansion of the actin network, the filaments are pushed back into the cell body, which is visible as retrograde actin flow. Through integrin-mediated adhesion complexes that couple the cytoskeleton to the substrate, these retrograde-directed forces, which are enforced by actomyosin contraction, are translated into forward locomotion of the cell body (Vicente-Manzanares et al., 2009).

A central mechanical concept of the lamellipodium is that actin polymerization drives the protrusion of the membrane. This principle also underlies other protrusions, such as filopodia, which are more explorative than force generating and invadosomes, which are responsible for invasion of tissue barriers (Ridley, 2011). There is only one known alternative to actin-driven protrusion: membrane blebs. These are anterior cellular extensions free of actin filaments. Here, intracellular hydrostatic pressure generated by actomyosin contraction causes rupture of either the actin cortex itself (Tinevez et al., 2009) or the linkage between actin and plasma membrane (Charras et al., 2006). Once the membrane loses its support, intracellular pressure inflates a membrane bleb that grows until a new actin cortex is reassembled, which eventually contracts and allows the cycle to restart (Charras and Paluch, 2008).

Studies of lamellipodial-based migration have dominated the literature, and many epithelial and mesenchymal cell types use these structures to migrate in vivo. However, blebbing is also a physiologically relevant locomotion strategy, notably in germ cells, which migrate efficiently by a directed and persistent blebbing motion (Blaser et al., 2006). Naturally, experimentally selected model systems for each migration mode tend to represent the “cleanest” and most prototypic examples. In reality, many cells are able to switch between blebbing and polymerization-driven motility depending on the environmental conditions or in response to genetic or pharmacological manipulation (Lämmermann and Sixt, 2009 Diz-Muñoz et al., 2010). In particular, malignantly transformed cells are able to adopt several poorly characterized crossover strategies in which blebs occur as leading extensions or epiphenomena at the trailing edge (Poincloux et al., 2011).

Three issues have been the focus of interest when studying blebbing versus lamellipodial locomotion strategies: (1) the role of substrate adhesion, (2) the role of substrate geometry, and (3) the signaling modules required for front–back polarization. Stabilized cell–cell or cell matrix adhesions can be involved in both blebbing and lamellipodial motility, although both types might also be functional without them (Renkawitz and Sixt, 2010). In general, the stability and physiological importance of adhesions appear to be decreased in fast and flexibly migrating amoeboid cells, which can either use the blebbing or the lamellipodial mode (Lämmermann and Sixt, 2009). Slow mesenchymal movement, which relies completely on focalized substrate adhesions, was generally considered lamellipodial and has not yet been associated with blebbing. Regarding the dimensionality of the environment, there is good evidence that all modes of movement can occur in 2D as well as in 3D environments, with the general notion that 3D but not 2D environments also allow motility under minimal adhesion forces (Friedl and Wolf, 2010). How polarity is established and maintained appears to be tightly coupled to the type of protrusion the cell employs. The key regulators are the Rho GTPases Rac, Cdc42, and RhoA. Rac is essential for lamellipodial expansion by activating the WAVE complex that in turn triggers actin nucleation by the Arp2/3 complex (Steffen et al., 2006 Wu et al., 2012). Cdc42 contributes by activating formins and the Arp2/3 complex (via the actin nucleation-promoting factor Wiskott–Aldrich syndrome protein) that stimulate actin polymerization during formation of filopodia and invadosomes. RhoA switches on actomyosin contractility by regulating myosin II and formins (Ridley, 2006). Thus, the Rho GTPases are the central signaling hubs through which diverse input signals are funneled. Depending on cell type and physiological context, completely different internally amplified or externally triggered pathways influence Rho GTPase activation levels and thereby cytoskeletal polarity. At the same time, numerous feedback loops have been identified that stabilize polarity. Best established are the phosphatidylinositol 3-kinases (PI3 kinases) that act both upstream and downstream of Rac and modulate the leading edge in many cell types (Cain and Ridley, 2009). The fact that actin polymerization (Millius et al., 2009) as well as actomyosin contractility and adhesion coupling (Vicente-Manzanares et al., 2009) can feed back on Rho GTPases further allows the cell to sense its environment and possibly to adapt the migration mode to geometry, chemical composition, and mechanical properties of its surroundings.

In their new study, Petrie et al. (in this issue) find cylindrical-shaped lobopodia, which have features of both blebs and lamellipods to be the predominant protrusion type of mesenchymal cells migrating in physiological 3D environments. Interestingly, like Abercrombie et al. (1970a,b,c) 40 yr ago, they used fibroblasts as a model. However, instead of growing the cells on coverslips they placed them in or on top of different types of 3D extracellular matrix scaffolds, including skin explants. In the tissue as well as in the cell-derived extracellular matrix the cells migrated with blunt-ended protrusions that developed multiple small lateral blebs. Unlike lamellipodia, these lobopodia accumulated neither active Rac and Cdc42 nor PI3 kinases, but the cells still formed focalized adhesions (Fig. 1). Similar to blebbing cells, lobopodia were very sensitive to perturbations of actomyosin contractility. Decreased contractility caused an instantaneous switch to the classical lamellipodial migration mode—notably without significant alterations in cell velocity. It was not only the geometry that induced lobopodia. Although the cells consistently developed lamellipodia in 2D when placed on top of different matrices, they also used lamellipodia when incorporated into gels made of noncross-linked bovine collagen. A combination of protocols to manipulate collagen fiber cross-linking and biophysical measurements led the authors to the conclusion that, once incorporated into a 3D matrix, the cells “read out” the elastic properties of the scaffold. Intuitively, one might have thought that lobopodia develop in environments of low stiffness, where actomyosin contraction might automatically squeeze the cells as the fibers to which the cells bind to give in. However, it was not simply the stiffness of the surroundings that caused a switch in protrusions but rather the shape of its stress strain curve: lobopodia only formed in linearly elastic environments, such as skin, and the cell-derived matrix but not in noncross-linked collagen gels that show strain stiffening. In the latter, lamellipodia predominated.


Descriptions

The nucleus is where the DNA is kept and RNA is transcribed. RNA is moved out of the nucleus through the nuclear pores. Proteins needed inside the nucleus are transported in through the nuclear pores. The nucleolus is usually visible as a dark spot in the nucleus, and is the location of ribosome formation.

Ribosomes are where RNA is translated into protein. This process is called protein synthesis. Protein synthesis is very important to cells, therefore large numbers of ribosomes are found in cells. Ribosomes float freely in the cytoplasm, and are also bound to the endoplasmic reticulum (ER). ER bound to ribosomes is called rough ER because the ribosomes on the ER give it a rough sandpaper like look.. These organelles are very small, made up of 50 proteins and several long RNAs bound together. Ribosomes do not have a membrane. Ribosomes fall into two seperate units while not synthesizing protein.

The endoplasmic reticulum is the transport system for molecules needed for certain changes and specific destinations, instead of molecules that float freely in the cytoplasm. There are two types of ER, rough and smooth. Rough ER has ribosomes attached to it, as mentioned before, and smooth ER does not.

The lysosome is the digestive system in the cell. It breaks down molecules into their base components digestive enzymes. This demonstrates one of the reasons for having all parts of a cell compartmentalized, the cell couldnt use the destructive enzymes if they werent sealed off from the rest of the cell.

The cell membrane functions as a semi-permeable barrier, allowing a very few molecules across it while fencing the majority of organically produced chemicals inside the cell. Electron microscopic examinations of cell membranes have led to the development of the lipid bilayer model (also referred to as the fluid-mosaic model). The most common molecule in the model is the phospholipid, which has a polar (hydrophilic) head and two nonpolar (hydrophobic) tails. These phospholipids are aligned tail to tail so the nonpolar areas form a hydrophobic region between the hydrophilic heads on the inner and outer surfaces of the membrane.

The cytoplasm was defined earlier as the material between the plasma membrane (cell membrane) and the nuclear envelope. Fibrous proteins that occur in the cytoplasm, referred to as the cytoskeleton maintain the shape of the cell as well as anchoring organelles, moving the cell and controlling internal movement of structures.

Microtubules function in cell division and serve as a "temporary scaffolding" for other organelles. Actin filaments are thin threads that function in cell division and cell motility. Intermediate filaments are between the size of the microtubules and the actin filaments.eeze-fracturing is able to split the bilayer.

Vacuoles are single-membrane organelles that are essentially part of the outside that is located within the cell. The single membrane is known in plant cells as a tonoplast. Many organisms will use vacuoles as storage areas. Vesicles are much smaller than vacuoles and function in transport within and to the outside of the cell.

The golgi bodies changes molecules and divides them into small membrane contained sacs called vesicles. These sacs can be sent to various locations in the cell.Golgi Complexes (follow the link to the MIT Hypertextbook page on Golgi) are flattened stacks of membrane-bound sacs. They function as a packaging plant, modifying vesicles from the Rough ER. New membrane material is assembled in various cisternae of the golgi.

Like mitochondria, chloroplasts have their own DNA, termed cpDNA. Chloroplasts of Green Algae (Protista) and Plants (descendants of some Green Algae) are thought to have originated by endosymbiosis of a prokaryotic alga similar to living Prochloron (Prochlorobacteria). Chloroplasts of Red Algae (Protista) are very similar biochemically to cyanobacteria (also known as blue-green bacteria [algae to chronologically enhanced folks like myself :)]). Endosymbiosis is also invoked for this similarity, perhaps indicating more than one endosymbiotic event occurred.

Mitochondria are a part of tissue cells that consists of an outer and an inner membrane. The mitochondria are the main energy source of the cell, in fact, they are often called the "power plants" of the body because this is where energy (ATP) is created. Uncoupled thermogenesis also occurs in the mitochondria any of the very tiny rodlike or stringlike structures that occur in nearly all cells of plants and animals, and that process food for energy


CBSE Class 9 Science Chapter 6 Tissues Notes (Part-I)

Get here the CBSE Class 9 Science Notes (Part-I) for Chapter 6 - Tissues. The notes are prepared by the subject expert and are according to the latest syllabus for CBSE Class 9 Science.

This article brings you the CBSE Class 9 Science notes on chapter 6 ‘Tissues’ (Part-I). These chapter notes are prepared by the subject experts and cover every important topic from the chapter. At the end of the notes, you can try the questions based on the topics discussed in these notes. With the help of these questions, you can clear your concepts and start preparation for your Science test or annual exam.

Main topics covered in this part of CBSE Class 9 Science, Tissues: Chapter Notes, are:

  • Definition of Tissues
  • Plant Tissues
  • Meristematic Tissues and Their Types
  • Permanent Tissues and Their Types

Key notes for Chapter 6 - Tissues are:

A group of cells that are specialized to perform a particular function forms a tissue.

Tissues are mainly classified into two types:
1.Plant Tissues 2. Animal Tissues

1.Plant tissues

→ Plants do not move, i.e., they are stationary.

→ Most of the tissues they have are supportive, which provides them with structural strength.

→ Most of these tissues are dead, as they can provide better mechanical strength than the live ones, and need less maintenance.

→ Some of the plant tissues keep on dividing throughout the plant life. These tissues are localised in certain regions.

Types of Plant Tissues:

Based on the dividing capacity of the tissues, various plant tissues can be classified as growing or meristematic tissue and permanent tissue which have further sub-divisions as explained below:

A. Meristematic Tissue
Meristematic tissues are responsible for growth in plants. Cells in these tissues can divide and form new cells.

Meristematic tissues are of three types:
(i) Apical Meristem: It is present at the growing tip of the stem and roots and increases the length. .

(ii) Lateral Meristem (cambium): It is present beneath the bark. It is responsible for growth in girth of trunk.

(iii) Intercalary Meristem: It is present at internodes or base of the leaves and increases the length between the nodes.

B. Permanent Tissue

→ Cells of meristematic tissues change their shape & size to get specialised in performing other functions in plants body. This process is called Differentiation.

→ Once the cells of meristematic tissue divide to a certain extent, they become specialized for a particular function.

Permanent tissues are of two types:

Simple tissues and Complex tissues

(i) Simple tissues: This type of tissue is composed of same type of cells.
These are again of four types:

(a) Parenchyma simple tissues: Cells of parenchyma tissues are live. They are oval, elongated and loosely packed with large inter-cellular space, forming basic packing of tissue and are found throughout the plant body.

→ They provide mechanical support to the plant body.

→ They store food and nutrients in vacuoles.

Chlorenchyma: Parenchyma with chlorophyll which performs photosynthesis is called as chlorenchyma.

Aerenchyma: In aquatic plants, cells of parenchyma have large air cavities to give buoyancy to the plant and is called aerenchyma .

(b) Collenchyma simple Tissues: Cells of collenchyma are live. They are oval and elongated and tighily packed with no inter-cellular spaces. They are found below epidermis in leaves and stem.

Functions of collenchymas tissues:

→ They provides mechanical support to plant.

→ They also provide flexibility to plants so that they can bend without breaking.

(c) Sclerenchyma Simple Tissues: Cells of sclerenchym are dead. They are narrow and elongated. The cell wall in sclerenchyma is composed of lignin which makes it hard. Sclerenchyma are found around vascular bundles, veins of leaves in hard covering of seeds and nuts. For example: Scalerenchyma tissues are found in coconut husk.

Functions of sclerenchyma:

→ They help to makes parts of plant hard and stiff.

→ Also provides mechanical strength.

(d) Protective tissues: They protect the plant body by forming an outer layer.

There are two types of protective tissues:

1.Epidermis Simple Tissues: Epidermis tissue covers the entire body of plant. They protect plant from injury, germs and water loss.

Cells of epidermal tissue form a continuous layer without intercellular spaces.
Stomata are small openings on epidermal layer of leaf and soft part of stem to facilitate the gaseous exchange and transperation in plants. Each stomata is composed of two guard cells which regulate the opening and closing of stomata.
In desert plants, epidermis and cutin (a water proof waxy substance secreted by epidermis) are thicker to reduce loss of water due to transpiration.

2.Cork Simple Tissues: These types of tissue consist dead cells with no intercellular spaces. They form the outer layer of old tree trunks.

Cork cells have a chemical called suberin in their walls that makes them impervious to gases and water.

Cork tissue protects plants from injuries, germs and water loss.

Cork being light in weight is used for making several products like bottle stoppers and shuttle cork.
(ii) Complex tissues: Group of different type of cells performing common task together are named as complex tissues.
Complex tissues are of two types:
(a) Xylem (b) Phloem

(a) Xylem: This is the tissue that transports water and nutrients from root to upper parts of plant. It is composed of four types of cells i.e., tracheid, vessel, xylem parenchyma and xylem sclerenchyma (fibre).

1.Trachieds are long elongated cells with tapered ending. Trachied cells are dead. Trachied transports water through pits.

2.Vessel is a pipe like structure. Vessels are dead and have lignified thick cell wall. Upper and lower portion of cell wall is absent.

3.Parenchymas are living cells. They store food and nutrients.

4.Sclerenchymas (fibres) are dead cells. They provide mechanical support to plant.

(b) Phloem: Phloem is the tissue that transports food from site of photosynthesis to different parts of plants.

It is composed of four types of cell i.e. sieve cells, companion cells, phloem parenchyma, phloem fibre or blast fibre. Al types of cells are live except phoem fibres.

1.Sieve cells are elongated and have thin cell wall. They have cytoplasm but no nucleus and other organelles. These cells are responsible for transportation of food and nutrients
2.Companion cells have cytoplasm, nucleus and other organelles. They perform the tasks required for sieve cells for living.
3.Phloem parenchyma store food.
4.Phloem fibres have thick cell wall and they provide mechanical support to plant.

Try the following questions:

Q1. Name the tissue which allows easy bending in various parts of a plant.


Connective tissue

Question 2 Enumerate various cells of connective tissue?

Question 3 What are tendons?

Question 4 What are ligaments?

Question 5 What are cartilage?

Question 6 What are the functions of blood?

Question 7 What are the functions of areolar tissues?

Question 8 What is the function of adipose tissue?

They are specialised to connect various body parts.
For Ex:Bone to bone,Muscle to bone or tissue.
The main function is binding ,supporting and packing together different organs of body.
The cells of connective tissue are living, separated from each other and are very less in number.Homogeneous gel like intercellular substance called matrix form the bulk of connective tissue.Cells are embedded in matrix.

a)Areolar: They are found between skin and muscles, around blood vessels, nerves, fill space inside organs.
1)It act as supporting and packing tissue between organs lying in body cavity.
2)it helps in repair of tissue after an injury.
3)It fixes skin to underlying muscles.

They are of 2 types:
1)Tendons:They are inelastic, cord like, strong structures that join muscle to bone.
They are made of white fibres.

2)Ligaments:They are highly elastic and has great strength but contain very little matrix.They connect bone to bone and are made of yellow and white fibres.

b)Adipose:They are basically an aggregation of fat cell.Each fat cell is rounded or oval and contain a large droplet of fat that almost fill it.
They are abundant below the skin, between internal organs, in yellow bone marrow.
it acts as an insulator(regulates body temperature, it forms shock absorbing cushion around kidney and eye ball.)

c)Skeletal tissue:They are of 2 types:
1)Bone
2)Cartilage

Bone:It is very strong, non-flexible tissue, porous, highly vascular, its matrix is made up of proteins, heavily coated with P,Ca and Mg salts.These minerals are responsible for hardness of the bone.
Function
1)It forms endoskeleton of human being and other vertebrates.
2)It provide shape and support to body.
3)It protects vital body organs.
4)It serves as a storage site of Ca and Phosphate.

2)Cartilage:It is a flexible connecting tissue connecting joints between bones, ribs cage ,ear, nose etc.It act like shock absorbent.

4)Fluid
a)Lymph
b)Blood

Blood:In this cell move in a fluid or liquid medium called plasma(55%).
The blood plasma does not contain protein fibres but contain blood cell or corpuscles.Plasma is a complex fluid which contains inorganic salts and organic compounds.
1)RBC:Red Blood Cells or erythrocytes
2)WBC:White Blood Cells or leucocytes
3)Platelets:They are non-living.

Blood occur in blood vessels(Arteries,Veins,Capillaries)

Function
1)They transport nutrients, hormones, vitamins to tissue.
2)They transport excretory products tissue to liver and kidney.
3)RBC carry oxygen to tissue for oxidation of food.
4)WBC fight diseases.
5)Platelets disintegrate at the site of injury and helps in blood clotting.


Diffusion

Particles in liquids and gases have kinetic energy, therefore they move about at speed in all directions. These particles move in a random motion. Where there is an area of high concentration some of these particles collide into one another, lose energy and slow down. Others will escape from the area of high concentration to an area of low concentration elsewhere. Very few particles travel the opposite way. The result is a concentration gradient with particles diffusing from an area of high concentration to an area of low concentration. Diffusion occurs in gases and with any substance in a solution.

Therefore we can say that the definition of diffusion is as follows:

Diffusion: The movement of particles from an area of high concentration to an area of low concentration until they spread out evenly.


Watch the video: Excel regneark (June 2022).


Comments:

  1. Dobi

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  2. Meztitaur

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  3. Dugrel

    It - is healthy!

  4. Bowyn

    It is remarkable, very valuable information



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