Animal Tissues
Click on the images to expand or contract.
Adipose tissue
Fat tissue, also known as adipose tissue, is easy to recognize. Each adipocyte (fat cell) is filled with a large fat globule, which is appears as empty space in our slides. Because of this large amount of fat, the adipocyte's cytoplasm and nucleus are pushed to the perimeter of the cell. These cells are large, with some over 200 μm across.
Areolar tissue
Areolar tissue is a type of loose connective tissue containing extensive protein fibers. The fibers are outside the cells, so they are part of the extracellular matrix. The cells are widely scattered, with large areas of extracellular matrix between them.
This tissue is stretchy and resilient, thanks to thick collagen fibers and thinner elastic fibers, made of a protein called elastin. I won't test you on which fiber is which; the main point is the overall tissue structure.
Reference:
Loose connective tissue on Wikipedia.
Blood smear
This picture shows human blood cells smeared onto the slide. Most of the cells are erythrocytes, which lack nuclei and have a smooth, oval shape. Various other types of blood cells are visible.
References:
Histology Photomicrographs from Karen Hart at Peninsula College.
Wright's stain on Wikipedia.
Cardiac muscle
Cardiac muscle, or heart muscle, is similar in appearance to skeletal muscle, but with a few distinct differences. Each cardiac muscle cell has a single nucleus, unlike the multinucleate skeletal muscle cells.
Reference:
Cardiac muscle from Karen Hart at Penisnula College.
Columnar Epithelium Intestine
This picture shows a low-magnification view of a cross section of intestine. The lumen is the area through which chyme (partially digested food) passes. The lining of the intestine is folded into villi, adding to the surface area of the intestine. The movement of chyme through the intestine is controlled by a layer of smooth muscle, and some loose connective tissue lies between the muscle and intestinal lining.
This is the epithelial layer lining the small intestine; the white area in the middle of the picture is the deep fold between two villi. These cells are tightly packed, forcing them into a tall, columnar shape. These cells are joined together with tight junctions that prevent leakage of materials between the cells. Behind the single layer of columnar epithelium cells is a region of loose connective tissue containing blood vessels.
The goblet cells secrete the mucus that lines the intestine.
Reference:
Compact bone decalcified
The hard, calcium-rich mineralized component of the bone has been dissolved away, leaving the bone looking more like cartilage. This low-magnification image shows a cross section of a bone filled with bone marrow, which contains stem cells that produce blood cells.
This picture shows a closer view of the marrow.
References:
Hyaline cartilage xiphisternum
Hyaline cartilage is the smooth cartilage that lines joint surfaces and reinforces many other structures, such as the trachea. This is a connective tissue, and like other connective tissues it contains widely dispersed cells with a large amount of extracellular matrix. In this case, the matrix forms a smooth, dense mass. The chondrocytes, cells that produce the cartilage, are found in lacunae, which are small holes in the extracellular matrix.
Necturus intestine simple columnar epithelium
This slide shows some very well-defined column-shaped epithelial cells from the intestinal lining of Necturus, a salamander. See the description of "Columnar epithelium intestine," above.
The brush border is the layer of microvilli which serve to increase the surface area of the intestinal epithelium.
Skeletal muscle tongue
This slide, though labeled "Skeletal muscle tongue," contains a variety of features in addition to skeletal muscle. First, you should realize that the tongue is a muscular hytrostat. This means that the tongue can be extended by one group of muscle fibers squeezing another group of fibers, creating hydrostatic pressure. In order for this to work, mammalian tongues have multiple muscle fibers crossing one another at right angles. Thus, in the same slide, you can see muscle fibers in longitudinal section and in cross section. In addition, you should also be able to find blood vessels, adipose tissue, and loose connective tissue in this slide.
Skeletal muscle is the type of muscle that you can voluntarily contract (unlike smooth muscle or cardiac muscle). Thus, the muscles in your tongue might not be connected to your skeleton, but they are skeletal muscles.
This image shows longitudinally sliced muscle fibers at higher magnification. Each muscle fiber is formed by the fusion of several cells and each fiber is multinucleate (contains multiple nuclei, which stain dark purple). The fibers are mostly filled with the proteins actin and myosin, which together form the contractile filaments of the muscle. The nuclei are pushed to the sides of the muscle fibers.
This image shows a vein in the "skeletal muscle tongue" slide. This blood vessel is filled with erythrocytes (red blood cells), and the blood plasma is visible as a smooth pink area between the cells. Erythrocytes lack nuclei, so they are pale pink in this slide. The few blood cells that do have a dark purple nucleus are not erythrocytes; see the blood slide for more information on these.
Simple cuboidal epithelium kidney
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This is a cross section of a mammalian kidney. The collecting ducts are large and round, and it's easy to see why the cells that make up the collecting duct epithelium, with their square shape, are called cuboidal epithelium.
This slide also shows a number of smaller-diameter sections of loops of Henle, as well as some blood vessels. For a more detailed explanation, see the references belowl
References:
Kidney histology at UCSD Medpics. Multiple images of different regions of the kidney.
Urinary System from a class at Yale. Excellent look at how the kidney works, including histology images.
Smooth muscle
This section of smooth muscle is from the area surrounding the intestine. Although smooth muscle contains actin and myosin protein fibers like skeletal muscle, their arrangement is fairly different.
Stratified squamous epithelium
"Stratified" means that there are multiple layers of epithelial cells, and "squamous" means that the cells are flattened (as opposed to cuboidal or columnar). This type of tissue is found in many locations where there is fairly rapid turnover of cells. New cells are produced at the bottom as old cells on top break away.
In this slide, as in most of our slides, the nuclei stain dark purple, while the rest of the cell stains pink.
Sample test question
You'll see some tissue slides on the lab exam, with questions like:
1. What type of tissue is this?
- Adipose
- Blood
- Bone
- Cartilage
- Epithelium
- Muscle
I won't ask you do differentiate more specific types such as what type of epithelium (stratified vs. pseudostratified vs. columnar, etc.).
2. Which embryonic tissue layer generates this tissue type?
- Ectoderm
- Endoderm
- Mesoderm
This question is fairly easy to answer. Epithelia are generated from either endoderm or ectoderm; since you can't easily tell which one, that wouldn't be a good test question. Muscle, bone, cartilage, adipose, and blood are derived from mesoderm.
References & further reading
Campbell Biology, Figure 40.5 provides a simple summary of animal tissues.
The Histology Guide. Excellent reference.
Histology Photomicrographs from Karen Hart at Peninsula College
Histology World. Extensive site with many photos and videos.
Medical Histology Atlas at Penn State. Very detailed and organized.
UCSD Medpics. Great kidney images (renal system), similar to the cuboidal epithelium slide we have in lab.