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Histology tissue

Histology tissue


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Can anybody tell me from where is this tissue taken and in with techique is it colored please ?


I might as well be wrong, not being an histologist, but that's probably a classic: mammal liver tissue, (poorly) H&E stained, also showing Kupfer cells having phagocytosed something black (carbon particles from indian ink?).


It looks like a classic HE stain. (https://en.wikipedia.org/wiki/H%26E_stain)

Unfortunately I cannot help with identifying the source of the tissue as you have not specified a organism of origin.


Histology at the University of Michigan

The conversion of the Michigan Histology website to a Flash-independent viewer has now been completed and you should be able to use any Internet browser to open and view the virtual slides. Users will see only one link for each virtual slide, no longer two (Webscope and Imagescope). All sample and practice question pictures have been converted to still images. The new slide viewer will also work on computer tablets and smartphones. Please let us know about any problems with the new viewer and the revised pages, specifically missing or incorrect links.

Special thanks for their great work goes to the University of Michigan HITS teams as they did most of the conversation work. Specially I would like to mention Naveen Jain, Michael Blake, Brian Simko, Tara Manwaring, and Dima Tawakkol.

The Department of Cell & Developmental Biology at the University of Michigan Medical School provides this digital microscopy resource for the study of cells, tissues and organs. A full list of virtual slides and a full list of virtual EM micrographs are also available.

Please note that the material provided by this website is copyrighted and that a permission is required for any commercial use. Otherwise this material is made available under a BY-SA-NC Creative Commons license 4.0.

We appreciate that you are using the Michigan Histology Website and are honored to share our resources with students and faculty members from all over the world. Keep learning (histology)!


Animal Tissues

There are four basic tissues in humans and other animals: epithelial tissue, connective tissue, muscle tissue, and nervous tissue. The embryonic tissue (ectoderm, mesoderm, endoderm) from which they derive sometimes varies, according to species.

Epithelial Tissue

Cells of epithelial tissue form sheets that cover the body and organ surfaces. In all animals, most epithelium derives from the ectoderm and endoderm, except the epithelium, which derives from the mesoderm. Examples of epithelial tissue include the skin surface and the linings of the airways, reproductive tract, and gastrointestinal tract. There are several kinds of epithelium, including simple squamous epithelium, simple cuboidal epithelium, and columnar epithelium. Functions include protecting organs, eliminating waste, absorbing water and nutrients, and secreting hormones and enzymes.

Connective Tissue

Connective tissue consists of cells and non-living material, called the extracellular matrix. The extracellular matrix may be either fluid or solid. Examples of connective tissue include blood, bone, adipose, tendons, and ligaments. In humans, cranial bones derive from the ectoderm, but the other connective tissues come from the mesoderm. Functions of connective tissue include shaping and supporting organs and the body, allowing body movement, and providing oxygen diffusion.

Muscle Tissue

The three types of muscle tissue are skeletal muscle, cardiac muscle, and smooth (visceral) muscle. In humans, muscles develop from the mesoderm. Muscles contract and relax to allow body parts to move and blood to pump.

Nervous Tissue

Nervous tissue is divided into the central nervous system and peripheral nervous system. It includes the brain, spinal cord, and nerves. The nervous system derives from the ectoderm. The nervous system controls the body and communicates between its parts.


Epithelial Tissue

Epithelial tissue is made up of cells that line inner and outer body surfaces, such as the skin and the inner surface of the digestive tract. Epithelial tissue that lines inner body surfaces and body openings is called mucous membrane. This type of epithelial tissue produces mucus, a slimy substance that coats mucous membranes and traps pathogens, particles, and debris. Epithelial tissue protects the body and its internal organs, secretes substances (such as hormones) in addition to mucus, and absorbs substances (such as nutrients).

The key identifying feature of epithelial tissue is that it contains a free surface and a basement membrane. The free surface is not attached to any other cells and is either open to the outside of the body, or is open to the inside of a hollow organ or body tube. The basement membrane anchors the epithelial tissue to underlying cells.

Epithelial tissue is identified and named by shape and layering. Epithelial cells exist in three main shapes: squamous, cuboidal, and columnar. These specifically shaped cells can, depending on function, be layered several different ways: simple, stratified, pseudostratified, and transitional.

Epithelial tissue forms coverings and linings and is responsible for a range of functions including diffusion, absorption, secretion and protection. The shape of an epithelial cell can maximize its ability to perform a certain function. The thinner an epithelial cell is, the easier it is for substances to move through it to carry out diffusion and/or absorption. The larger an epithelial cell is, the more room it has in its cytoplasm to be able to make products for secretion, and the more protection it can provide for underlying tissues. Their are three main shapes of epithelial cells: squamous (which is shaped like a pancake- flat and oval), cuboidal (cube shaped), and columnar (tall and rectangular).

Figure 7.4.2 The shape of epithelial tissues is important.

Epithelial tissue will also organize into different layerings depending on their function. For example, multiple layers of cells provide excellent protection, but would no longer be efficient for diffusion, whereas a single layer would work very well for diffusion, but no longer be as protective a special type of layering called transitional is needed for organs that stretch, like your bladder. Your tissues exhibit the layering that makes them most efficient for the function they are supposed to perform. There are four main layerings found in epithelial tissue: simple (one layer of cells), stratified (many layers of cells), pseudostratified (appears stratified, but upon closer inspection is actually simple), and transitional (can stretch, going from many layers to fewer layers).

Figure 7.4.3 The layerings found in epithelial tissues is important.

See Table 7.4.1 for a summary of the different layering types and shapes epithelial cells can form and their related functions and locations.

Summary of Epithelial Tissue Cells

So far, we have identified epithelial tissue based on shape and layering. The representative diagrams we have seen so far are helpful for visualizing the tissue structures, but it is important to look at real examples of these cells. Since cells are too tiny to see with the naked eye, we rely on microscopes to help us study them. Histology is the study of the microscopic anatomy and cells and tissues. See Table 7.4.2 to see some examples of slides of epithelial tissues prepared for the purpose of histology.

Epithelial Tissues and Histological Samples


Careers in Histology

A person who prepares tissues for sectioning, cuts them, stains them, and images them is called a histologist. Histologists work in labs and have highly refined skills, used to determine the best way to cut a sample, how to stain sections to make important structures visible, and how to image slides using microscopy. Laboratory personnel in a histology lab include biomedical scientists, medical technicians, histology technicians (HT), and histology technologists (HTL).

The slides and images produced by histologists are examined by medical doctors called pathologists. Pathologists specialize in identifying abnormal cells and tissues. A pathologist can identify many conditions and diseases, including cancer and parasitic infection, so other doctors, veterinarians, and botanists can devise treatment plans or determine whether an abnormality led to death.

Histopathologists are specialists who study diseased tissue. A career in histopathology typically requires a medical degree or doctorate. Many scientists in this discipline have dual degrees.


Types of Plant Tissues

Vascular

Vascular tissues in plants transport substances throughout the different parts of the plant. The two types of vascular tissue are xylem and phloem. Xylem transports water and some soluble nutrients, while phloem transports organic compounds the plant uses as food, particularly sucrose. Vascular tissues are long and thin, and form cylinders that nutrients are transported through like pipes. Vascular tissue is also involved with two types of meristems, which are tissues that contain undifferentiated cells that are used during a plant’s growth. The meristems accompanying vascular tissue are the cork cambium and the vascular cambium. These meristems are associated with the growth of the plant’s vascular tissues.

Ground

Ground tissue is made up of all cells that are not vascular or dermal (having to do with the epidermis see below). There are three types of ground tissue: parenchyma, collenchyma, and sclerenchyma. Parenchyma cells form the “filler” tissue in plants, and perform many functions like photosynthesis, storage of starch, fats, oils, proteins, and water, and repairing damaged tissue. Collenchyma tissue is made up of long cells with irregularly thick walls that provide structural support to the plant. Plants that grow in windy areas have thicker walls of collenchyma tissue. Sclerenchyma is also supporting tissue, but it is made of dead cells. There are two types of sclerenchyma: fibers and sclereids. Fibers are long, slender cells, while sclereids are star-shaped with thick cell walls. Sclerenchyma fibers make up fabrics such as hemp and flax.

Epidermal

The epidermis is made up of a single layer of cells that covers a plant’s roots, stems, leaves, and flowers. (Epidermis is also the word for skin in human anatomy.) It guards the plant against water loss, regulates the exchange of carbon dioxide and oxygen, and in roots, it absorbs water and nutrients from the soil. The epidermis on a plant’s stems and leaves have pores called stomata, which carbon dioxide, water vapor, and oxygen diffuse through. Epidermal cells are themselves covered by the plant cuticle, which contains mainly cutin, a waxy substance that protects against water loss. Plants in deserts and other arid regions often have thick cuticles to help conserve water.


Histology

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Histology, branch of biology concerned with the composition and structure of plant and animal tissues in relation to their specialized functions. The terms histology and microscopic anatomy are sometimes used interchangeably, but a fine distinction can be drawn between the two studies. The fundamental aim of histology is to determine how tissues are organized at all structural levels, from cells and intercellular substances to organs. Microscopic anatomy, on the other hand, deals only with tissues as they are arranged in larger entities such as organs and organ systems (e.g., circulatory and reproductive systems).

In their investigations, histologists mainly examine quantities of tissue that have been removed from the living body these tissues are cut into very thin, almost transparent slices using a special cutting instrument known as a microtome. These thin sections, as they are called, may then be stained with various dyes to increase the contrast between their various cellular components so that the latter can be more easily resolved using an optical microscope. Details of tissue organization that are beyond the resolving power of optical microscopes can be revealed by the electron microscope. Tissues can also be kept alive after their removal from the body by placing them in a suitable culture medium. This method is useful for cultivating (and later examining) certain types of cells and for studying embryonic organ rudiments as they continue to grow and differentiate. A special branch of histology, histochemistry, involves the chemical identification of the various substances in tissues.


Lange histology and cell biology

Although a review-type book, this one suffers from a severe lack of diagrams and micrographs.

Although this might not be such a bad thing for your average review book, I simply cannot see how it measures up in such a visual field as histology.

It is not a bad book when it comes to the actual material covered, which is quite extensive. Also, It does better with regards to cell biology, which is less visual dependent.

Although not a bad book, I recommend you know what you need for your course before going for this one. You can check it out yourself by clicking this link to head over to Amazon. There you can get a preview of the book and its current pricing.


Histology tissue - Biology

HISTOLOGY BIOL-4000 LECTURE NOTES #4

intermediate filaments = tonofilaments

endoplasmic reticulum (rough, smooth)

A. There are 4 basic tissue types

1. A simple definition might be "a layer of cells with a free surface".

2. A better definition is that they are single or multiple layers of cells characterized by,

a. closely aggregated, polyhedral cells

c. very little intercellular substance between cells (know the difference between inter and intra)

d. cells that adhere strongly to each other

e. cells that form sheets that cover a surface

3. In embryonic terms we can say that epithelia are derived from all 3 major germ layers, that is ectoderm, mesoderm, endoderm.

a. The embryo starts out as a single cell called the zygote. This cell undergoes a process called cleavage that is characterized by multiple mitoses that create a hollow ball of cells in many species. These cells arrange themselves into 3 distinct germ layers that give rise to specific groups of organs.

* Ectoderm - mainly nervous system.

* Mesoderm - mainly muscle and the lining of body cavities

* Endoderm - mainly organs of digestive tract.

A. Covering and lining surfaces, e.g. skin, epithelial cells (endothelium) lining blood vessels, body cavities = coeloms = peritoneal, pleural and pericardial coeloms). For example, the entire external body is covered by an epithelium. Characteristics of epithelia differ depending on which part of the body you're talking about. (Note that food in the stomach or intestine is really still outside the body, it's just in a tunnel that goes through the body).

B. Since epithelia line cavities within the body, as well as the outside of the body, anything passing into or out of the body must pass through an epithelium.

C. Various properties that an epithelium can have:

1. absorption (tall columnar epithelium of intestine)

2. secretion (epithelia of glands)

3. sensation (sensory cells, neuroepithelium - taste buds)

4. contractility (myoepithelium - often associated with glands such as sweat and mammary glands)

BASIC CELL SHAPES FOUND IN EPITHELIA

A. squamous - flat - very thin in cross-section

B. cuboidal - square shape in cross-section

C. columnar - tall, column shaped - rectangular in cross-section

1. NOTE THAT HOW AN EPITHLIUM LOOKS IN SECTIONS DEPENDS ON ORIENTATION OF THE EPITHELIUM WHEN SECTIONS ARE CUT. A CUBOIDAL EPITHELIUM CAN LOOK "LOW" COLUMNAR, ETC.

2. ALSO NOTE THAT WHILE THE THREE SHAPES OF EPITHELIA ARE AS THEY ARE SEEN IN CROSS-SECTION, THE CELLS ARE REALLY POLYHEDRAL IN THREE DIMENSIONS.

3. There are also intermediate shapes of some epithelia that lie between the major types described above.

4. Shape of nucleus often corresponds to cell shape.

a. Cuboidal epithelial cells, nucleus – spherical (circular in cross section)

b. Squamous epithelial cells - nucleus flattened with long axis parallel to basement membrane.

c. Columnar - nucleus oblong, long axis perpendicular to basement membrane.

5. The shape of the nucleus is sometimes important in distinguishing different types of epithelia since often the cell plasmalemma is indistinct despite staining.

GENERAL CHARACTERISTICS OF EPITHELIA AND WHY EPITHELIA HAVE THESE CHARACTERISTICS.

A. An epithelium has a basal lamina (50 - 80 nm, not resolved by light microscope)

1. Found wherever an epithelium contacts connective tissue. Visible only at EM level. Consists of granular layer of thin fibrils that is composed of

b. a glycoprotein called laminin, and

c. other large molecules called proteoglycans.

2. A partial barrier (semipermeable) to diffusion between epithelia and underlying connective tissue.

3. Evidence suggests that the basal lamina is formed by the epithelial cells rather than the connective tissue.

B. Basement membrane - name for stained structure seen beneath layers of cells that is visible with the light microscope. It consists of basal lamina + reticular lamina (or lamina rara) consisting of a reticular fiber layer that is attached to basal lamina by anchoring fibers.

1. Visible under light microscope when silver impregnation or PAS (Periodic Acid Schiff stain - stains carbohydrates) method is used. Composed of basal lamina and a thicker layer of reticular fibers. Staining properties indicate high glycoprotein content.

C. Cohesion, like sticks to like

1. Epithelial cells cohere strongly to each other. In part due to binding action of surface molecules such as glycoproteins.

2. Calcium important. Evidenced by fact that cells tend to disassociate in calcium free media.

3. One of the structures that cause epithelial cells to cohere to each other is the desmosome. These can only be seen with the electron microscope.

a. Disk-shaped structures on cells that form adjacent electron dense areas seen in ultrastructural preps. Small filaments called tonofilaments insert from the cytoplasm into the electron dense regions.

b. Granular or fibrillar structures in intercellular space (e.g., cadheins called desmogleins and desmocollins).

c. Desmosomes bind cells together. Found along cell surfaces below apical ends of cells.

* septate demosome - have fibrillar structures in intercellular space.

* hemidesmosome - half a desmosome. Electron dense substance ,and tonofilaments are only found on one side. Example - binding points of epithelial cells to basal lamina.

a. Junctional complex at apical end of cells. Originally observed with light microscope. At EM level, consists of an apical tight junction that is called the zonula occludens. The zonula occludens restricts direct passage of materials from outside of epithelia to cells below. (ZONULA - LATIN, MEANS STRUCTURE COMPLETELY SURRONDS CELL AS BAND. OCCLUDENS - LATIN, REFERS TO FACT THAT CELL MEMBRANES ARE DIRECTLY OPPOSED WITH NO INTERCELLULAR SPACE BETWEEN.) Note that in 3-D the zonula occludens is circumferential, i.e. it surrounds the entire apical end of a cell.

b. zonula adherens - some similarity to desmosome, acts as anchoring point for terminal web of apical filaments found in tall columnar epithelial cells such as those of lining of intestine.

D. Surface specializations of epithelia

1. microvilli - increase surface area, may be branched and called stereocilia (not actually cilia)

2. cilia, flagella - same basic structure, differ in length. movement of materials over epithelia. Can remove debris- e.g. tracheal cilia that direct mucus carrying particulates out of trachea. probably working hard at this time of year.

CLASSIFICATION OF EPITHELIA

A. Simple - one layer of cells, endothelium of blood vessels. lining of Bowman's capsule in kidney nephrons.

B. Stratified ep[ithelium - more than one layer of cells

1. keratinized, stratified, squamous epithelium - skin. Actually, only the cells close to the free surface are squamous. Deeper cells tend to be cuboidal or irregular in shape. Surface cells are dead and heavily keratinized.

2. stratified squamous mucosal epithelium (membranes) - line wet cavities, mouth, esophagus, vagina. Often glandular.

3. stratified cuboidal epithelium – surface cells cuboidal. Deeper cells cuboidal to irregular.

4. stratified columnar epithelium – surface cells are columnar with deeper cells being cuboidal to irregular in shape.

5. transitional epithelium - intermediate form of cells, often binucleate. urinary bladder. Cells of this epithelium tend to bulge into cavity that free surface is adjacent to. When epithelium is distended due to filling of bladder, the epithelium looks like stratified squamous.

6. pseudostratified columnar epithelium - looks like more than one layer of cells due to the nuclei of the cells being at different levels in adjacent cells (e.g., ciliated pseudostratified columnar epithelium of respiratory tract). In actuality, most of the cells of the epithelium extend from the basement membrane to the free surface.

C. Glandular epithelium - secretory in function

1. endocrine – no duct, secretory product is released into nearby capillaries (e.g., Islets of Langerhans in pancreas),

2. exocrine - retain connection with the free surface of the epithelium via a duct. See lecture notes for how to classify various exocrine glands.

a. Both types (endocrine and exocrine) exist in the pancreas. Exocrine - secretions (digestive enzymes) carried through ducts to duodenum. Endocrine - Islets of Langerhans, insulin secreted directly into capillary blood. Exocrine – acinar glands with ducts.

3. Types of exocrine glands:

a. merocrine - product released by exocytosis, secretory granules

b. holocrine - whole cell shed.

c. apocrine - apical portion of cell shed.

BIOLOGY OF EPITHELIAL CELLS

A. Epithelial cells usually do not contact capillaries so nutrition depends on diffusion through tissues to epithelial cells. Similarly, excretion of wastes depends on diffusion. Secretion is sometimes accomplished by exocytosis.

B. Epithelia are often subject to high wear and tear. In such cases the cells are continuously renewed by the mitotic activity of stem cells in the epithelium.

C. Epithelia may be subject to action of hormones - glandular epithelia may increase or decrease secretion of product in response to hormonal control.

D. Since epithelial cells are often situated in organs where they are actively involved in adsorption or secretion it's not surprising that we would find active transport systems that act to maintain ionic balance within the cell.

1. e.g. Renal tubules - tight junctions prevent direct flow of ions across epithelial lining. So, ions must flow through epithelial cells. Can move in either direction. Active transport systems responsible for ion movement require ATP to function. Since cells are very active in transport of ions, lots of ATP needed, so lots of mitochondria.

2. These cells have high rates of active transport and so are very active metabolically. Thus, the presence of enzymes necessary for oxadative phosphorylation in mitochondria, as well as other enzymes in Krebs cycle and glycolysis can be demonstrated by histochemical methods.

RELATION OF STRUCTURE AND FUNCTION

A. Epithelial cells are involved in controlling movement of molecules or ions into or out of a particular part of the body. Thus, you may find active transport systems such as exocytosis and pinocytosis.

1. EXAMPLE - squamous (endothelium) epithelium lining blood vessels - transport via pinocytosis in and out of cells. The pinocytotic vesicles can be visualized with the electron microscope with ferritin.

2. ANOTHER EXAMPLE - DIFFERENT TYPE OF CELL - SECRETORY. Secretory cells such as those found in epithelium lining the exocrine portion of pancreas (pancreatic acinar cells). These cells have active Golgi bodies located near the nucleus that produce membrane bound vesicles for exocytosis of digestive enzymes that are packaged within them. These vesicles are called secretion granules. Exocytosis of the contents of these vesicles occurs at the apical end ("free surface") of the cell.

3. Glycoprotein secreting cells - goblet cells of epithelial lining of intestine – mucus – apocrine secretion

4. All these protein secretory cells have a number of structural components in common.


Lab 2: Microscopy and the Study of Tissues

Tissues are composed of similar types of cells that work in a coordinated fashion to perform a common task, and the study of the tissue level of biological organization is histology. Four basic types of tissues are found in animals.

Epithelium is a type of tissue whose main function is to cover and protect body surfaces but can also form ducts and glands or be specialized for secretion, excretion, absorption and lubrication.

Epithelial tissues are classified according to the number of cell layers that make up the tissue and the shape of the cells. Simple epithelium is composed of a single layer of cells while stratified epithelium contains several layers.

Epithelial sells can be flat (squamous = "scale-like"), cube-shaped (cuboidal) or tall (columnar). So, to correctly identify the type of tissue requires three words (e.g., simple columnar epithelium, stratified, squamous epithelium, etc.

Connective tissue performs such diverse functions as binding, support, protection, insulation and transport. Despite their diversity, all connective tissues are comprised of living cells embedded in a non-living cellular matrix consisting of extracellular fibers or some type of ground substance. Thus, what distinguishes the different connective tissues is the type of matrix. Examples of connective tissue would include bone, cartilage, tendons, ligaments, loose connective tissue, adipose (fat) tissue, and even blood (although some authorities would classify blood as a vascular tissue).

Muscle tissue is specialized for contraction. There are three kinds of muscle tissue:

  1. Smooth muscle (designed for slow, sustained, involuntary contractions) is made up of spindle-shaped cells with one nucleus per cell.
  2. Skeletal, or striated muscle, which is associated with voluntary contractions, contains cylindrical cells with many nuclei per cell arranged in bundles.
  3. Cardiac (heart) muscle is striated like skeletal muscle, but each cell contains only one nucleus.

Nervous tissue is specialized for the reception of stimuli and conduction of nerve impulses. The tissue is composed of nerve cells (neurons), each of which is made up of a cell body and cell processes that carry impulses toward (dendrites) or away from (axons) the cell body. In the following pages of this lab unit, you will have an opportunity to examine a few (of the many) types of animal tissue.

In terms of understanding the workings of the multicellular animal body, however, you should realize that tissues are but one of many connected levels of biological organization. Tissues rarely work alone but instead, they are grouped into organs. Organs are combined to form organ systems (e.g., the circulatory system, nervous system, skeletal system, muscular system, excretory system, reproductive system, etc.) that function as an integrated unit called an organism.

In subsequent units of the Zoo Lab website, you will be introduced to the diversity of animal life that results from the interaction of all of these key components.

Lab-2 01

This slide shows a thin section of frog skin. The outermost portion of this skin is composed of a single layer of irregularly-shaped, flat (squamous) cells, which gives the tissue its name. Note: You are viewing this tissue section from the top! This slide shows a thin section of frog skin. The outermost portion of this skin is composed of a single layer of irregularly-shaped, flat (squamous) cells, which gives the tissue its name. Note: You are viewing this tissue section from the top!

Lab-2 02

The red and blue arrows point to simple cuboidal epithelial tissue

This is a slide of a thin section taken from the mammalian kidney showing the many tubular ducts that make up much of this organ. The walls of these ducts (pointed to by the red arrows) are comprised of simple cuboidal epithelial cells, which are usually six-sided in shape but may appear square from a side view. Note also the thin wall of simple cuboidal epithelium (pointed to by the blue arrow) that forms the top edge of this section.

Lab-2 03

  1. Smooth muscle (long. layer)
  2. Smooth muscle (circ. layer)
  3. Simple columnar epithelium
  4. Goblet cell
  5. Lumen of the intestine

This slide is a cross section from the small intestine. Projecting into the intestinal lumen (space) are numerous finger-like projections called villi, which function to slow the passage of food and increase the surface area for the absorption of nutrients. The lining of these villi is a tissue layer called the mucosa, which is made up of simple columnar epithelial cells. Interspersed among these columnar cells are goblet cells that secrete mucus into the lumen of the intestine. During routine histological preparation, the mucus is lost, leaving a clear or lightly stained cytoplasm. Beneath a thin, outer covering of the intestine called the serosa is a thick layer of smooth muscle cells called the muscularis externa. The muscularis externa is divided into an outer longitudinal muscle layer with cells that run along the axis of the intestine and an inner, circular muscle layer whose fibers encircle the organ. Peristaltic contraction of these two muscle layers keeps food moving through the digestive tract.

1- Smooth muscle (long. layer) & 2 - Smooth muscle (circ. layer)

3 - Simple columnar epithelium & 2 - Goblet cell

Lab-2 04

  1. Goblet cell
  2. Columnar epithelial cells
  3. Epithelial cell nucleus
  4. Lumen of the intestine

Lab-2 06

This slide shows a cross section of the esophagus, the first portion of the digestive tract that leads to the stomach. Note that the organ is lined with a many layers of cells referred to collectively as stratified squamous epithelium. By convention, stratified epithelial tissues are named by the shape of their outermost cells. Thus, although the deeper and basal layers are composed of cuboidal and sometimes even columnar cells, those cells at the surface are squamous (flat) in shape, giving the tissue its name.

1 - Stratified squamous epithelium

Lab-2 07

Lab-2 08

This slide shows a thin section of loose connective tissue (sometimes called areolar tissue). This type of tissue is used extensively throughout the body for fastening down the skin, membranes, blood vessels and nerves as well as binding muscles and other tissues together. It often fills in the spaces between epithelial, muscle and nervous tissue, forming what is known as the stroma of an organ, while the term parenchyma refers to the functional components of an organ. The tissue consists of an extensive network of fibers secreted by cells called fibroblasts. The most numerous of these fibers are the thicker, lightly staining (pink) collagen fibers (1). Thinner, dark-staining elastic fibers (2) composed of the protein elastin can also be seen in the section. s is a slide of a thin section taken from the mammalian kidney showing the many tubular ducts that make up much of this organ. The walls of these ducts (pointed to by the red arrows) are comprised of simple cuboidal epithelial cells, which are usually six-sided in shape but may appear square from a side view. Note also the thin wall of simple cuboidal epithelium (pointed to by the blue arrow) that forms the top edge of this section.

Lab-2 09
  1. Lumen of the trachea
  2. Pseudostratified (ciliated)columnar epithelium
  3. Hyaline cartilage (100x)
  4. Adipose tissue

This slide showing a cross section of the mammalian trachea (wind pipe) contains examples of several different kinds of tissues. Supporting the trachea is a ring of connective tissue called hyaline cartilage. The chondrocytes (cartilage cells) that secrete this supporting matrix are located in spaces called lacunae.

3 - Hyaline cartilage (100x)

Lab-2 10

1 - Hyaline Cartilage (400x)

Lab-2 11

Lab-2 09

  1. Lumen of the trachea
  2. Pseudostratified columnar epithelium (close-up view)
  3. Hyaline cartilage
  4. Adipose tissue

2 - Pseudostratified columnar epithelium (close-up view)

Lab-2 12

Lab-2 09

  1. Lumen of the trachea
  2. Pseudostratified columnar epithelium (close-up view)
  3. Hyaline cartilage
  4. Adipose tissue (100x)

4 - Adipose tissue (100x)

Lab-2 10

2 - Adipose tissue (400x)

Lab-2 13

Lab-2 14

This slide contains a section of dried compact bone. Note that the bone matrix is deposited in concentric layers called lamellae. The basic unit of structure in compact bone is the osteon. In each osteon, the lamellae are arranged around a central Haversian canal that houses nerves and blood vessels in living bone. The osteocytes (bone cells) are located in spaces called lacunae, which are connected by slender branching tubules called canaliculi. These "little canals" radiate out from the lacunae to form an extensive network connecting bone cells to each other and to the blood supply.

Close-Up View of an Haversian System

Lab-2 15

Lab-2 16

This is a slide of a bundle of smooth muscle tissue that has been teased apart to reveal the individual cells. Each of these spindle shaped muscle cells has a single, elongated nucleus. In most animals, smooth muscle tissue is arranged in circular and longitudinal layers that act antagonistically to shorten or lengthen and constrict or expand the body or organ. For an example of such an arrangement, see the two smooth muscle layers on a cross section of mammalian gut.

Lab-2 17

  1. Stratified squamous epithelium
  2. Duct composed of simple cuboidal epithelium
  3. Skeletal muscle
  4. Adipose tissue
  5. Dense irregular connective tissue

Close-Up View of the Tongue

Lab-2 18

Lab-2 20

This slide contains a section of cardiac muscle, which is striated like skeletal muscle but adapted for involuntary, rhythmic contractions like smooth muscle. Although the myofibrils are transversely striated, each cell has only one centrally located nucleus. Note the faintly stained transverse bands, which are called intercalated disks, (indicated by the blue arrows) that mark the boundaries between the ends of the cells. These specialized junctional zones are unique to cardiac muscle.

Lab-2 19

Lab-2 21

This slide contains a longitudinal section of a tendon, which is composed of dense regular connective tissue. Note the regularly arranged bundles of closely packed collagen fibers running in the same direction, which results in flexible tissue with great resistance to pulling forces.

Lab-2 22

Because it is made up a single layer of scale-like cells, simple squamous epithelium is well suited for rapid diffusion and filtration. These cells look hexagonal in surface view but when viewed from the side (as shown in the image of the model above), they appear flat with bulges where nuclei are located. Simple squamous epithelium forms the inside walls of blood vessels (endothelium), the wall of Bowman's capsule of the kidney, the lining of the body cavity and viscera (parietal and visceral peritoneum) and the walls of the air sacs (alveoli) and respiratory ducts of the lung.

Surface view

Lab-2 23

Lab-2 24

Simple cuboidal epithelial cells are usually six-sided (cube shaped), but they appear square in side view (as shown on the above image of the model) and polygonal or hexagonal when viewed from the top. Their spherical nuclei stain darkly and often give the layer an appearance of a string of beads. This type of tissue is adapted for secretion and absorption. It can be found in such areas as the kidney tubules, the covering of the ovary and as a component of the ducts of many glands.

Viewed from the top

Lab-2 25

Lab-2 26

Simple columnar epithelium is composed of tall (columnar) cells that are closely packed together. Viewed from the surface they appear hexagonal but when viewed from the side (as shown on the image of the model above), they appear as a row of rectangles with the elongated nuclei frequently located at the same level, usually in the lower part of the cell. Simple columnar epithelial cells may be specialized for secretion (such as the goblet cells that secrete a protective layer of mucus in the small intestine), for absorption or for protection from abrasion. Columnar epithelial cells line a large part of the digestive tract, oviducts and many glands.

Viewed from the surface

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The image to the left shows a model of pseudostratified columnar epithelium. This type of tissue consists of a single layer of cells resting on a noncellular basement membrane that secures the epithelium. The tissue appears stratified (occurring in several layers) because the cells are not all the same height and because their nuclei (shown as black oval structures) are located at different levels. Pseudostratified ciliated columnar epithelium lines the trachea (windpipe) and larger respiratory passage ways.

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Skeletal muscle is the most abundant type of muscle tissue found in the vertebrate body, making up at least 40% of its mass. Although it is often activated by reflexes that function in automatically in response to an outside stimulus, skeletal muscle is also called voluntary muscle because it is the only type subject to conscious control. Because skeletal muscle fibers have obvious bands called striations that can be observed under a microscope, it is also called striated muscle. Note that skeletal muscle cells are multinucleate, that is, each cell has more than one nucleus.

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Smooth muscle is the simplest of the three kinds of muscle. It is found where slow, sustained, involuntary contractions are needed such as in the digestive tract, reproductive system and other internal organs. Smooth muscle cells are long and spindle shaped with a single, centrally located nucleus. Smooth muscle is often arranged in two layers that run perpendicular to one another, a circular layer whose fibers appear in cross section as shown on the model above and a longitudinal layer whose fibers appear like the ends of a cut cable when viewed on-end.

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Cardiac muscle is striated like skeletal muscle but adapted for involuntary, rhythmic contractions like smooth muscle. The myofibrils are transversely striated, but each cell has only one centrally located nucleus. Note the dark blue transverse bands on the model called intercalated disks that mark the boundaries between the ends of the muscle cells. These specialized junctional zones are unique to cardiac muscle.

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This model shows a cross section of compact bone. Observe that the matrix of the bone is deposited in concentric layers that are called lamellae (5). The basic unit of structure in this type of bone is the Haversian system, or osteon. In each of these osteons, the lamellae are arranged around a central Haversian canal (1) housing nerves (4) and blood vessels (2, 3) in living bone. Osteocytes or bone cells, (6) are located in spaces called lacunae (7) that are connected by slender branching tubules called canaliculi (8). These &ldquolittle canals&rdquo radiate out from the lacunae to form an extensive network, allowing bone cells to communicate with one another and to exchange metabolites.

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The image above is that of a greatly enlarged multipolar neuron, the most common type of neuron found in humans. Notice that the cell body (1) contains the nucleus (2) with its conspicuous darkly staining nucleolus (3). Branching from the cell body are cytoplasmic extensions called nerve cell processes. In motor neurons (which conduct nerve impulses toward muscle cells), these processes consist of a single, long axon (4) and many of shorter dendrites (5).

4 - Axon

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Note in this magnified view of an axon that it is surrounded by specialized cells called Schwann cells (1) whose plasma membranes form a covering of the axon called the neurilemma (2), which is shown in brown on the model. These Schwann cells secrete a fatty myelin sheath (3), which is shown in yellow on the model, that protects and insulates nerve fibers from one another and increases the speed of transmission of nerve impulses. Adjacent Schwann cells along an axon do not touch one another, leaving gaps in the sheath called nodes of Ranvier at regular intervals (4).


Watch the video: Introduction of Histology (May 2022).