Eukaryotes - animal cells and protozoa

TASK 1: Nerve cells (neurons)

PP: the spinal cord of pig (Sus) or rat - histologic cross section, stained with haematoxylin-eosin - "mícha"

Find the neurons in the so-called grey matter in the ventral spinal horns. Observe the large (particularly in the pig), intensively pink-stained neurons with nuclei and projections (dendrits).


fig.: A – cross-section of spinal cord, B – composition of the neuron.

TASK 2: Shape and number of nuclei

PP: leucocytes - "bílé krvinky", protozoan Spirostomum - "korálkovité jádro/růžencovité jádro", protozoan Paramecium - "mikronukleus a makronukleus", protozoan Opalina ranarum (polynuclear cell) - "mnohojaderná buňka"

Using small magnification, find a place with a higher density of leucocytes (violet dots scattered among more numerous pink erythrocytes) and observe the shapes of the nuclei: round in lymphocytes, kidney- or bean-like in monocytes, lobular, segmented or polymorphic in mature forms of granulocytes, s-shaped and band shaped in younger forms. Using a meandering movement, find a pink-stained ciliate protozoan Spirostomum with a bead-shaped nucleus. Observe violet coloured macronucleus (large nucleus, vegetative nucleus) and micronucleus (small nucleus, generative nucleus) in ciliate protozoan Paramecium. Observe the numerous purple-stained nuclei within the greenish cytoplasm of protozoan Opalina ranarum (polynuclear cell) living as a commensal in the cloaca of frogs.


Fig.: Different shapes and numbers of nuclei.

TASK 3: Cell organelles - Golgi apparatus, mitochondria

PP: Golgi apparatus is in the silver stained cross section of a rat intestine - "Golgiho aparát", liver selectively stained for mitochondria after Heidenhain - "mitochondrie"

Find an intact villus projecting into the lumen (interior) of the intestine. Find the layer of cylindric epithelial cells (enterocytes) on its surface. Note the violet elongated nuclei in the basal part of enterocytes and the Golgi apparatus in the apical (peripheral, luminal) part of enterocytes (above the nuclei). It is a round-shaped cluster of brown-black dots (silver stain) or is pale-colored. Observe occasional cells with two nuclei in the liver and mitochondria as tiny blue-black points (like powder) inside the liver cells (hepatocytes).


Fig.: A – cross section of intestine with villus, B – enterocyte with Golgi apparatus (GA) and nucleus.


Fig.: Mitochondria in liver cells (stained after Heidenhain).

TASK 4: Pigment inclusions

PP: melanophores or melanin containing cells in frog skin - "melanofory"

Observe the melanin pigment granules inside the cells (melanophores) with numerous branching projections. Melanophores or, more generally, chromatophores (Greek phorein = to carry), are responsible for coloration in animals (e.g. frogs) and sometimes enable color changes (in animals such as chameleons).


Fig.: Melanophores of frog containing pigment melanin.