Color Atlas A7
Regular Connective Tissue
Tendons are also made up of collagen fibers, but here the fibers (or fiber bundles) are arranged in orderly fashion parallel to each other
Nuclei of some cells (mainly fibroblasts) are seen between the bundles of collagen. They are elongated (elliptical).
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Fig. A2.2: Regular connective tissue as seen in tendon
Adipose Tissue
Adipose tissue is made up mainly of compactly arranged fat cells
In routine sections the cells appear empty as the fat gets dissolved during preparation of the section
The cytoplasm of each cell is seen as a pink “rim”
The nucleus is flat and lies to one side.
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Fig. A2.3: Adipose tissue
A8 Textbook of Human Histology
SPECIALIZED CONNECTIVE TISSUE
CARTILAGE
Unlike connective tissue, that can be deformed easily, cartilage is a special form of connective tissue that is firm, and retains its shape.
Hyaline Cartilage
It is characterized by groups of cartilage cells (chondrocytes) surrounded by a homogeneous matrix which separates the cells widely
Near the surface of the cartilage the cells are flattened and merge with the cells of the overlying connective tissue. This connective tissue forms the perichondrium
Costal cartilage and articular cartilage of synovial joint are example of hyaline cartilage.
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Fig. A2.4: Hyaline cartilage
Elastic Cartilage
In elastic cartilage chondrocytes are surrounded by matrix containing many elastic fibers
Perichondrium covering is present over the cartilage
It is seen typically in auricle and epiglottis.
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Fig. A2.5: Elastic cartilage
Color Atlas A9
Fibrocartilage
Fibrocartilage is characterized by presence of collagen fibers arranged in bundles with rows of chondrocytes intervening between the bundles
Perichondrium is absent
Fibrocartilage is seen typically in pubic symphysis and manubrio sternal joint.
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Fig. A2.6: Fibrocartilage
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BONE
Compact Bone
A transverse section through the compact bone shows ring-like osteons (or Haversian
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systems) |
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Haversian canal is seen at the centre of each |
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osteon |
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Around the canal there are concentric lame- |
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llae of bone amongst which there are small |
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spaces called lacunae in which osteocytes |
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are present |
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Delicate canaliculi radiate from the lacunae |
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containing processes of osteocytes |
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Interstitial lamellae fill intervals between |
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Haversian systems |
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Volkmann’s canal interconnecting the adja- |
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cent haversian canal may be seen. |
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Note: The appearance of compact bone is so chara- |
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cteristic that you are not likely to confuse it with any |
Fig. A2.7: Compact bone; transverse section of ground bone |
other tissue. |
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A10 Textbook of Human Histology
Spongy (Cancellous) Bone
It is made up of a network of bony trabeculae (pink) in which the nuclei of some osteocytes can be seen
The spaces of the network are filled in by bone marrow in which numerous fat cells are present
The spaces between the fat cells are occupied by numerous blood forming cells (only nuclei of which are seen).
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Fig. A2.8: Spongy (cancellous bone)
MUSCLE
Skeletal Muscle
In a longitudinal section through skeletal muscle the fibers are easily distinguished as they show characteristic transverse striations
The fibers are long and parallel without branching.Many flat nuclei are placed at the peripheryThe muscle fibers are separated by some con-
nective tissue.
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Fig. A3.1:+
Smooth Muscle
Fig. A3.2: Longitudinal section through smooth muscle
Cardiac Muscle
Fig. A3.3: Longitudinal section through cardiac muscle
Nervous Tissue
Color Atlas A11
In a longitudinal section through smooth muscle elongated spindle shaped cells without straitions are seen
A single elongated (oval) centrally placed nucleus can be identified
Smooth muscle is present in the walls of parts of the alimentary canal, in the urogenital tract, etc.
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The fibers are made up of “cells” each of which has a centrally placed nucleus and transverse striationsAdjacent “cells” are separated from one another by
transverse lines called intercalated discsFibers show branching.
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Grey matter contains cell bodies of neurons and neuroglia
White matter contains axons of neurons and neuroglia.
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Fig. A3.4: Spinal cord. A. Panoramic view B. Grey matter
A12 Textbook of Human Histology
STRUCTURES THAT ARE USUALLY SEEN AS SINGLE TUBES
ARTERIES
The structure of an artery varies greatly with its size. Each artery shows three layers, the tunica intima, tunica media and the tunica adventitia (in internal to external order). The lumen is lined by endothelium (flattened cells).
Elastic Artery
Fig. A4.1: Elastic artery
Elastic artery is characterized by presence of
Tunica intima consisting of endothelium, subendothelial connective tissue and internal elastic laminaThe first layer of elastic fibers of tunica media is
considered the internal elastic lamina
Thick tunica media with many elastic fibers and some smooth muscle fibers
Tunica adventitia containing collagen fibers and vasa vasorum.
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Muscular Artery
In muscular arteries, the tunica intima is made of endothelium and internal elastic lamina (arrow) which is thrown into wavy folds due to contraction of smooth muscle in the media
Tunica media is composed mainly of smooth muscle fibers arranged circularly
Tunica adventitia contains collagen fibers.
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Fig. A4.2: Muscular artery
Color Atlas A13
Vein
The vein has a thinner wall and a larger lumen than
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Fig. A4.3: Large vein
VERMIFORM APPENDIX
The vermiform appendix is the narrowest part of the gastrointestinal canal and is seen as a tubular structure
The innermost layer of the mucosa, is lined by simple columnar epithelium with goblet cells.
Crypts and lymphocytes are seen in lamina propria
The next layer, the submucosa may show a variable number of lymphatic nodules
The submucosa is surrounded by smooth muscle layer (muscularis externa) followed by serosa
The longitudinal muscle coat is complete and equally thick all round. Taenia coli as seen in
colon are not present.
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Fig. A5.1: Vermiform appendix # 4 " *
A14 Textbook of Human Histology
URETER
The ureter can be recognized because it is tubular and its mucous membrane is lined by transitional epithelium
The epithelium rests on a layer of connective tissue (lamina propria)
The mucosa shows folds that give the lumen a star shaped appearance
The muscle coat has an inner layer of longitudinal fibers and an outer layer of circular fibers. This arrangement is the reverse of that in the gut
The muscle coat is surrounded by adventitia made of fibroelastic connective tissue in which
blood vessels and fat cells are present.
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Fig. A6.1: Ureter
DUCTUS DEFERENS
This is a tube that can be distinguished from the ureter by its mucous membrane which is lined by pseudostratified columnar epithelium
The muscle coat is very thick. Three layers, inner longitudinal, middle circular and outer longitudinal are seen
The muscle coat is surrounded by adventitia containing blood vessels and nerves.
Fig. A7.1: Ductus deferens
Color Atlas A15
UTERINE TUBE
Fig. A8.1: Uterine tube
The uterine tube is characterized by presence of numerous branching mucosal folds that almost fill the lumen of the tube
The mucosa is lined by ciliated columnar epithelium
The uterine tube has a muscular wall with an inner circular and outer longitudinal muscle layer.
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A16 Textbook of Human Histology
STRUCTURES MADE UP MAINLY OF LYMPHOID TISSUE
LYMPHOID TISSUE
Lymphocytes are one variety of cells of blood. Collections of them are frequently seen in many tissues. Such aggregations constitute lymphoid tissue. Such tissue is seen in the form of aggregations of dark staining nuclei. Some organs (lymph nodes, spleen) are made up almost entirely of such tissue. At some sites lymphoid tissue shows nodules where the lymphocytes are more densely packed than elsewhere. The nodule may show a central area that is lighter staining (because the cells are less densely packed)
LYMPH NODE
A lymph node has an outer cortex and an inner medulla
The cortex is packed with lymphocytes. A number of rounded lymphatic follicles (or nodules) are present. Each nodule has a pale staining germinal center surrounded by a zone of densely packed lymphocytes
Within the medulla the lymphocytes are arranged in the form of anastomosing cords. Several blood vessels can be seen in the medulla
A thin capsule surrounds the lymph node, sending trabeculae into the cortex
Beneath the capsule is a clear space called subcapsular sinus.
Fig. A9.1: Lymph node
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