EPITHELIAL TISSUE
EPITHELIAL TISSUE
Objectives:To grasp the structure of simple squamous epithelium, simple cuboidal epithelium, simple columnar epithelium, stratified squamous epithelium.
To understand the structure of transitional epithelium.
Slide 58 Simple Squamous Epithelium ( Mesothelium ) AgNO3
This is a surface view of a frog’s mesentery. Choose thinner place to observe, the cell limits are stained black with AgNO3. The individual cell has hexagonal or irregular wavy outlines, and each contains a nucleus which is not shown in this slide.
Slide 32 Simple Squamous Epithelium ( Mesothelium ) H.E.
This is the cross section of colon. In the outmost layer, mesothelium which likes a line is present. The mesothelial cells are fusiform with deep-stained ovoid nuclei in centre. The outlines of the cells are not clear.
Slide 42 Simple Cuboidal Epithelium ( Thyroid ) H.E.
In this section, there are many follicles in various sizes, which are composed of simple cuboidal epithelium. In the lumen
EPITHELIAL TISSUE
of the follicle contains red colored homogenous colloid. The epithelial cells appear as a row of square profiles with round nuclei in centre.
Slide 29 Simple Columnar Epithelium ( duodenum ) H.E.
This is a section of the duodenum. There are many intestinal villi which are finger-like projections of mucosa.
The surface of villi are covered by the simple columnar epithelium. The epithelial cells are mainly composed of columnar cells which are the tall rectangle cells with elongated nuclei occupying the base of these cells.Among the columnar cells you can find some Goblet cells with a deep-stained and triangle-shaped nucleus.
Slide 5 Pseudostratified Ciliated Columnar Epithelium
（Trachea） H.E.
This is a ring of transversally sectioned treachea with large central lumen. The thin bluish-purple colored layer lining the luminal surface is pseudostratified ciliated columnar epithelium.
This epithelium appears as multilayered because of the presence of nuclei at two levels. However all cells rest on a pink basement membrane which is located between epithelium and connective tissue, but some of them do not extend to the luminal surface.The epithelium consists of 4 type cells:
Columnar cells are tall with ovoid nuclei at high level. Their
EPITHELIAL TISSUE
free surface possesses regular cilia.
Basal cells are smallest and arranged in basal portion of this epithelium. They are pyramidal in shape，but their apices do not reach the free surface of the epithelium, their nuclei are round and situate in the basal portion of the cells.
Fusiform cells are spindle in shape with oval nuclei at the mid portion of the cells.
Goblet cells can be seen among the columnar cells. Their apical portion enlarges like a pale round vacuole due to dissolution of secretory granules during section preparation. Their narrow basal portion contains deep blue-stained nucleus which is compressed by apical secretion and become triangular in form.
Slide 4 Stratified Squamous Epithelium ( Esophagus ) H.E.
On the lumen side of the esophagus, you will be able to find nonkeratinized stratified squamous epithelium.
The epithelium sheet is thick, which consists of many layers of epithelial cells of different sizes and shapes but these epithelial cells change their shape gradually from the basal layer to the superficial layer. At the basal surface, connective tissue projects toward the epithelium, forms many pyramidal papillae. A layer of dark stained cells surrounding the papillae is the basal layer of epithelium.
Basal layer contains one layers of small, cuboid or low columnar epithelial cells which rest on the basement membrane.
EPITHELIAL TISSUE
Mid layer is composed of several layers of large polyhedral cells with clear boundary and ovoid nuclei.
Superficial layer is made of several layers of flat cells. The cells closely overlap each other. Both the cells and their nuclei are very flat.
Slide 66 Transitional Epithelium ( Bladder ) H.E.
This is a section of a contracted bladder. This special stratified epithelium typifies the lining of urinary tract. Unlike the previous stratified epithelia, however, the surface layer of cells characteristically project into the lumen, giving them the name “dome cells”. Cell outlines are less distinct in this epithelium, and the cells are variably flattened, depending on the state ofdistension. It is a layer of large, dome-shape cuboidal or rectangular cells with deep-acidophilic cytoplasm. Occasionally contains two nuclei.
The intermediate layer is composed of one to several layers of irregular polyhedral cells and pear-shaped cells located above the polyhedral cells.Pear-shaped cells are inverted-pear in shape with its broad base upward toward the domes. The deepest layer of cells consists of one layer of cuboid cells.
The full and distended bladder shows less layers of cells, and the cells are more flattened.
CONNECTIVE TISSUE PROPER
CONNECTIVE TISSUE PROPER
Objectives:To grasp the spread and section of loose connective tissue (fundus of stomach).
To understand reticular connective tissue (lymph node), dense connective tissue and adipose tissue.
Slide 6 Loose Connective ( Areolar ) Tissue
Mesenterium in Spread Preparation.
Orcein or Aldehyde Fuchsin Stain.
This preparation was made by ripping off a small portion of the mesentery spread with previous injection of trypan blue and spreading it out gently on a slide before fixation.
Choose a thin and distinct area of the tissue for observation. Two types of fibers can be distinguished:
Collagen fibers: --wavy stranded bundles of fiber of varied thickness run in all directions. They are reddish in color. These bundles of fiber branch by subdivision of the strands (i.e. by separation of small collagen fibers from one another).
Elastic fibers: --stain in purple or dark red. These normally appear straight but where breakage has occured may appear wavy due to elastic recoil. Note unlike collagen fibers, it forms single structures which branch directly at acute angles.
CONNECTIVE TISSUE PROPER
Among these fibers at least two types of cells, macrophages and mast cells can be seen:
Macrophages are irregularly shaped cells with small rounded nuclei and engulf a lot of foreign particular matter such as trypan blue granules in the cytoplasm.
Mast cells often lie along the course of the blood vessels, and run in groups. They are round or ovoid with small rounded nuclei, their cytoplasm contains a large amount of blue colour granules.
Slide 3 Loose Connective Tissue ( Stomach ) H.E.
The portion of gastric fundus stained lightly is loose connective tissue. It occupies the bluish-purple gastric mucosa above and red muscular layer below.
Find and locate the loose connective tissue area in which fibers are loosely arranged and variously sectioned, the collagenous fibers are numerous, pinkish, while elastic fibers are scant and in brilliant red but hardly distinguished. Among fibers, many cells containing bluish-purple ovoid or fusiform nuclei are fibroblasts. Ground substance is lost during preparation and only empty spaces left between fibers and cells.
Within the loose connective tissue, many vessels can be seen.
CONNECTIVE TISSUE PROPER
Slide 8 Dense Connective Tissue ( Lymph node ) H.E.
Lymph node is surrounded by a capsule of dense connective tissue.The pink-staining collagen fibers are in tightly packed bundles parallel to the longitudinal axis of the node and the cells between them are flattened to a fusiform with little cytoplasm.
Slide 19 Adipose Tissue ( Skin ) H.E.
This is the section of skin. Skin is composed of two parts, the outer epidermis and inner dermis. Beneath the dermis is the hypodermis, containing many fat cells. Fat cells are arranged in groups and appear vacuolated cytoplasm due to the drops of lipid being dissolved during section preparation. The nuclei are small flattened in periphery.
Slide 7 Reticular Tissue ( Lymph node ) AgNO3
This is the section of lymph node. The reticular fibers are stained black with AgNO3 ,showing short branches and network. The reticular cells are lightly yellow with some processes.
CARTILAGE
CARTILAGE
Objective:To grasp the morphological feature of hyaline cartilage (Trachea).
To understand the morphological feature of elastic cartilage and fibrocartilage.
Slide 5 Hyaline Cartilage ( Trachea ) H.E.
This slide is a cross-section through the trache. Locate the tracheal lumen and look at the blue-stained hyaline cartilage deep to the epithelium.
The cartilage is covered by a layer of dense connective tissue named perichondrium. The inner layer of the perichondrium is rich in cells which can differentiate directly into chondroblasts, while the outer layer of the perichondrium is rich in fibers.
The hyaline cartilage consists of a rather dense amorphous ground matrix in which are embedded groups of prominent rounded cartilage cells (chondrocytes). The cells are surrounded by a cartilagious capsule. At the periphery of hyaline cartilage, the chondrocytes have elliptic shape, with their long axis parallel to the surface. They are round and may appear in groups . The
CARTILAGE
matrix immediately around each group is rich in chondroitin sulfate and may be stained more deeply than the remainder, in
living tissue, the chondrocytes fill the lacunae completely, the cavities (lacunae) sometime appear empty since the cytoplasm of chondrocyte tends to collapse after fixation. Note that the cartilage is devoid of blood vessels.
Slide 9 Elastic Cartilage ( External Ear ) Orcein
The ear pinna is covered by skin , elastic cartilage located in
the center of the pinna. The cells are quite similar to those of hyaline cartilage. Note the dense network of blue staining elastic fibers which fill the matrix between lacunae containing the chondrocytes. The fibers are thick and rich in number in the center of cartilage, while the fibers settled peripherally are fine, sparse and continuous with those of perichondrium.
Slide 10 Fibrocartilage ( Intervertebral Disc ) Mallory
Collagen fibers are the major constituent of this matrix. They reveal as thick and compact collegenous bundles with blue colour, paralleling or interweaving with one another. The red-stained chondrocytes are ovoid in shape, small in size and arranged in column. Small amount of matrix can be seen between the collagenous bundles.
BONE
BONE
Objective:To grasp the structure of Haversian system.
Slide 11 Compact Bone ( Ground Bone ) Dialia Violet
Calcified bone is too hard to be sectioned on a microtome. This section was prepared by cutting thin slices in transverse section with a saw and grinding these down to the required thickness with abrasives. The preparation is stained and the organic material is not preserved . Such sections show the layered
calcified intercellular matrix but not the cellular structure or other organic material.
Harversian system: You should be able to see the outlines of irregular Harversian Systems. They consist of:
1) A centrally located Harversian canal in which vessels, lymphatics, nerves and connective tissue are located at living period, the empty space, which are filled with debris and dye stain appear purple.
2) A series of concentrically arranged lamellae are the Harversian lamellae. The bone lamellae are arranged in concentric layers around a central Harversian canal. The lamellae represent an alternation of dark and bright lamellae because the
BONE
fibers in different lamellae are different in orientation. The bone lamellae fluctuate from several layers to more than 10 layers.
Interstitial lamellae: They are irregular lamellae which occupy the intervals between the Harversian system.
Circumferential lamellae: At the external surface of the bone, there are the outer circumferential lamellae. These consist of several lamellae that run about the circumference of the shaft of bone. A similar but less well developed system of lamellae is present on the inner surface of the bone, the inner circumferential lamellae.
There are a lot of black ovoid lacunae between the lamellae where the osteocytes are placed. Many delicate channels radiated from the lacunae are canaliculi where the cytoplasmic
processes of the osteocytes project into. The canaliculi in the adjacent lamellae are connecting with each other.
Slide 60 Compact Bone ( Ground Bone ) Dialia Violet
This section was prepared by cutting thin slices in longitudinal section with a saw and grinding these down to the required thickness with abrasives.
Slide 12 Decalcified Bone ( Compact Bone ) H.E.
In order to obtain sections thin enough for studying the
BONE
organic constituents of bone, the tissue has to be “decalcified” by
seaking it for a long period in a dilute acid solution whichdissolve the bone salts. A bone treated in this manner retains its riginal appearance and microscopic structure but is soft, flexible and can be easily cut with a microtome knife after embedding in wax.
This is a transverse section of bone. The bone tissue appears red, because the matrix of the decalcified bone has high content of collagen. Within the Harversian cannel, the vessels connective tissue and nucleus of the osteocytes within the lacunae can be seen.
Slide 59 Decalcified Bone ( Compact Bone ) H.E.
This is a longitudinal section of decalcified bone.
DEVELOPMENT AND GROWTH OF BONE
DEVELOPMENT AND GROWTH OF BONE
Objective:To understand the development of bone.
Slide 54 Endochondrial Ossification ( Finger ) H.E.
There are 2 or 3 phalangs inside the finger, the 2 blue large ends of the phalange are epiphysis and the pinkish intermediate portion is diaphysis of long bone.
Select a typical phalange and study from epiphysis to diaphysis. Recognize the 4 zones starting from the articulate cartilage.
Resting zone: It consists of hyaline cartilage, the chondrocytes are small without morphologic difference from the ordinary hyaline cartilage.
Proliferative zone: Chondrocytes divide rapidly and form paralleled raws of flattened cells along the long axis of bone. Toward the diaphysis the chondrocytes become hypertrophy.
Calcified cartilage zone: It contains large chondrocytes, some of them are vacuolated and the diminished matrix is calcified that is stained in deep-blue.
Ossification zone: The chondrocytes undergo degeneration DEVELOPMENT AND GROWTH OF BONE
and the thin partitions of matrix between the lacunae with a raw are dissolution.The blood capillaries and undifferentiated cells origination from the periosteum invade the cavity left by the chondrocytes. These gaps are primitive marrow cavity. Farther towards the center of diaphysis the residual calcified cartilage matrix is stained in pink or substituted by osseous matrix completely. These are newly-formed osseous trabeculae.
The marrow cavity: The trabeculae are resorbed that the
primary marrow cavities are joined with each other forming a large cavity which lies in the central of the diaphysis with red marrow and blood sinuses in it.
The sequential processes of endochondrial ossification may be summarized as: cartilage model formation→cartilage proliferation →cartilage regression →cartilage destruction →bone formation.
Observe the ossification zone in detail. There are osteocytes embedded in the trabeculae. Pay special attention to the morphological features of the osteoblasts and osteoclasts.
Osteoblasts: These cells frequently lie in single row on the surface of new bone. They are cuboidal or irregular in shape with basophilic bluish-purple stained cytoplasm and large round eccentrically placed nuclei. The osteoblasts secret osseous matrix.
As soon as they are embedded in the matrix, they are no longer osteoblasts but osteocyts.
Osteoclasts: They are large, irregular, multinucleated cells
DEVELOPMENT AND GROWTH OF BONE
which usually present an acidophilic cytoplasm lying within the depressions in the bone where the bone is being resorbed.
Slide 55 Intramembranous Ossification
( Skull of Embryo ) H.E.
This is a section through the center of ossification in the skull. Move the slide and locate the parietal area, you will be able to see bone deposition within mesenchyme as a result of the transformation of mesenchymal cells into osteoblasts. Some of the osteoblasts have already been entrapped in the bone as osteocytes, the others still left on the surface of bone trabecula. Sometimes osteoblasts can be seen.
BLOOD
BLOOD
Objective:To grasp the functions and morphological
feature of erythrocytes, neutrophils, eosinophils, lymphocytes, monocytes.
To understand the function and morphology
of basophils, platelets.
Preparation and Staining of Blood Smear
(1) Method of Obtaining blood
Blood may be obtained from the free margin in lobe of an ear or finger top. Because they are less sensitive to be punctured.
(2) Preparation of the Blood Smear
Take a small drop of blood on a chemically clean and dust-free slide about 2 cm from the end, taking care that the slide does not touch the skin. Place the slide on a table or flat surface. With the thumb and forefinger of the right hand hold the end of a second slide against the surface of the first at an angle of 30 to 40 degrees.