Fish 424 Laboratory Notes
Selected histology structures and terms
All information taken from: “Microscopic Anatomy of Salmonids: An Atlas”, US Department of the Interior, Fish and Wildlife Service
Eosinophilic - readily stains with eosin (pink)
Liver:
Hepatocytes- liver cells, dark purple with dense nucleus
Heptatic sinusoid- Spaces seen between hepatic cells.
Central Vein & or Heptatic Portal Vein - Concentration of erythrocytes within.
Bile Duct - Distinguished from blood vessels by linings of cuboidal or columnar cells and a lack of blood cells inside the lumen.
Arteriole - surrounded by connective tissue, erythrocytes seen in lumen
Glycogen vacuole - Empty spaces seen in liver.
Head kidney:
Interrenal gland- It is a cortisol producing tissue. Eosinophilic (pink), and is usually scattered throughout hematopoietic tissue. It can be found in close association with cardinal veins and chromaffin tissues that line the veins. No granules are observed in the cells and nucleus is round or oval and has a well-defined nucleolus and chromatin particles.
Chromaffin cell- Usually found lying along major blood vessels in the head kidney. Cytoplasm has no color and nucleus is lightly stained. Chromaffin cells produce epinephrine and norepinephrine. Nuclei are oval or irregular in shape and are larger than nuclei of interrenal cells. Granules seen in cells.
Postcardinal vein- Red blood cells found in concentrations in vein, surrounded by chromaffin and interrenal cells.
Hematopoietic tissue - many undifferentiated stem cells
Trunk kidney:
Nephron- Contains a renal corpuscle, a short neck segment (rare to see), proximal tube with a brush border, a distal tubule, and a collecting duct system terminating in the mesonephric duct. In freshwater fish, the major functions are conservation of salt and elimination of excess water.
Renal Corpuscle is composed of:
Glomerulus- Large and nearly fills Bowman’s capsule. Within the glomerulus, nucleated red blood cells can be observed within the capillary lumens, as can the nuclei of mesangial cells, capillary endothelial cells, and the podocytes of the visceral epithelium of Bowman’s capsule.
Basement membrane of glomerulus - lies between the mesangian and capillary endothelial cell layers
Bowman's capsule - expanded and funnel-like proximal end of the nephron
Proximal tubules- tall and columnar cells, typically intense staining basal region (cytoplasm can be bizonal), eosinophilic
Distal tubules- not as intensely staining as proximal tubule cells, shorter, oval basally located nuclei and no brush border, weakly eosinophilic
Melanocytes- diffusely located, melanin containing cells, black in color, irregular shape
Collecting duct - difficult to determine where distal tubule ends and the collecting duct begins. A collecting duct increases in size as it receives additional nephrons. The cells increase in height, the lumen size increases, and the amount of surrounding smooth muscle and connective tissue increases as the collecting duct approaches the mesonephric duct.
Mesonephric duct-Tall columnar, lightly staining cells, with elongated, basally located nuclei and large amounts of surrounding smooth muscle and connective tissue.
Connective tissue - surrounds collecting duct and mesonephric duct
Gills:
Filament- coming off the gill arch
Lamella- primary and secondary, perpendicular to filament
Epithelium - Covers entire branchial complex and is comprised of unspecialized, dark, chloride, and mucous cells. Unspecialized epithelial cells function as protection and support. The dark cells resemble unspecialized cells, and are scattered uniformly throughout the epithelium of the filaments and lamellae. These two cell types are not readily seen by light microscopy.
Goblet (or mucous) cell- appear as granule filled domes or vacuolated cells
Chloride cell -Located along entire lamellar epithelium, but more numerous at proximal end of lamellae. Nearly spherical in shape and tend to project from the gill surface.
Pillar (or pilaster) cell- lend support to lamella
Gill-filament cartilage- purple/pink center of lamella
Afferent arteriole - artery
Efferent arteriole - artery