General Zoology: Animal Histology, Development, and Microscopy

Comprehensive practice flashcards defining essential vocabulary across microscopy, animal cytology, mitosis, embryological development, and histology/organology.

Cytology

The branch of science that deals with the study of cells as the basic unit of structure and function in living organisms.

Parfocal Capability

A feature of a compound microscope allowing a specimen focused under low magnification to remain in fairly good focus when rotated to a higher magnification.

Resolving Power

A measure of lens quality representing the ability to deliver a clear image in fine detail.

Ocular Micrometer

A thin disc of glass or plastic etched with an unmeasured scale (usually ranging from 0 to 100) that sits in the ocular lens to measure microscopic specimens.

Stage Micrometer

A calibrated glass slide etched with a scale divided into $0.01\,\text{mm}$ graduations, used to calculate the calibration constant of an ocular micrometer.

Dissecting Microscope

A binocular microscope designed for magnifications between $5\times$ and $50\times$ that provides a three-dimensional view of specimens.

Normal Saline Solution

A $0.9\%\,\text{NaCl}$ solution utilized to disperse cheek cell scrapings when preparing a wet mount.

Interphase

The preparatory period that can comprise up to $90\%$ of the cell cycle, during which the cell grows, synthesizes microtubule proteins, and replicates its DNA.

Asters

Ray-like microtubule bodies that radiate around each centriole during prophase of cell division.

Kinetochore

A protein coat found on each sister chromatid where spindle fibers attach at the centromere.

Cleavage Furrow

A constriction of the plasma membrane along the equatorial plate that appears during early telophase to divide the cytoplasm during cytokinesis.

Ontogeny

The entire life history and individual developmental course of an organism from a fertilized egg to maturity.

Phylogeny

The evolutionary history and ancestral lineage of a species.

Blastomeres

Individual cleavage cells produced by the series of mitotic divisions of a single-celled zygote.

Morula

The solid ball of blastomeres resulting from repetitive, asynchronous mitotic divisions during early cleavage.

Blastocoel

The internal fluid-filled segmentation cavity formed by the blastomeres of the morula during blastulation.

Gastrulation

The embryonic phase involving morphogenetic movements that rearrange cells to form the primitive gut and establish the primary germ layers.

Archenteron

The primitive gut or gastrocoel formed during gastrulation that serves as the precursor to the digestive tract.

Blastopore

The external opening leading into the gastrocoel, which develops into the anus in deuterostomes and the mouth in protostomes.

Ectoderm

The outermost germ layer of the embryo that gives rise to the central nervous system, sense organs, and epidermis.

Mesoderm

The middle germ layer that gives rise to the heart, muscles, urogenital system, vertebral column, and dermis of the skin.

Endoderm

The innermost germ layer that gives rise to the epithelial lining of the intestinal tract and the lungs.

Neurulation

The process by which an ectodermal thickening (neural plate) invaginates into a neural fold and groove to form the hollow neural tube.

Notochord

A cylindrical rod of cells located immediately below the neural tube that serves as the principal axial support in vertebrate embryos.

Telolecithal Egg

An egg in which yolk is unevenly distributed and heavily concentrated at the vegetal pole opposite the animal pole.

Epimere

The most dorsal somite segment of the mesoderm positioned at the level of the notochord.

Mesomere

The intermediate segment of embryonic mesoderm that forms a longitudinal string of cells giving rise to the urogenital system.

Hypomere

The ventral-most lateral plate mesoderm that subdivides into splanchnic and somatic layers bounding the future coelom.

Organology

The scientific study of organs, which are functional units formed by combinations of different tissues.

Goblet Cells

Specialized pitcher-like mucus-secreting unicellular glands distributed among tall simple columnar epithelial cells in the intestine.

Transitional Epithelium

A stratified epithelium lining the urinary bladder whose superficial cell shapes range from round when empty to large and squamous when distended.

Ciliated Pseudostratified Columnar Epithelium

An epithelial tissue whose cells all contact the basement membrane with nuclei at differing levels, creating a false stratified appearance; lines the human trachea.

Fibroblasts

Spindle-shaped connective tissue cells with large ovoid nuclei that constitute the predominant cell type in areolar and dense regular connective tissues.

Adipocytes

Specialized fat-storing cells characterized by a thin rim of cytoplasm, a flattened peripheral nucleus, and a large lipid vacuole.

Neutrophils

The most abundant granulocytic leucocytes in blood, possessing a nucleus with 3 or more lobes.

Eosinophils

Granulocytic leucocytes with a bilobed nucleus that constitute $1\text{--}3\%$ of circulating white blood cells.

Basophils

The least numerous granulocytes ($0.5\%$ of leucocytes), recognizable by a distinct U- or J-shaped nucleus.

Lymphocytes

Small, agranular white blood cells comprising $20\text{--}25\%$ of leucocytes, having an indented nucleus and a thin rim of clear blue cytoplasm.

Monocytes

Large agranular leucocytes making up $3\text{--}8\%$ of blood white cells, possessing round, eccentric nuclei and abundant cytoplasm.

Thrombocytes

Blood platelets formed as cytoplasmic fragments pinched off from large bone marrow cells called megakaryocytes.

Chondrocytes

Mature cartilage cells that reside singly or in clusters within small extracellular fluid-filled cavities called lacunae.

Perichondrium

A dense connective tissue capsule enclosing hyaline and elastic cartilage.

Osteon

The cylindrical structural unit of compact bone (Haversian system) consisting of concentric lamellae, lacunae, and a central Haversian canal.

Canaliculi

Fine microscopic canals radiating from bone lacunae that connect osteocytes to one another and to Haversian canals.

Intercalated Disks

Darkly stained transverse lines crossing branching cardiac muscle fibers at irregular intervals.

Nissl Bodies

Bluish-staining granular clumps of material dispersed throughout the cell body and dendrites of a neuron.

Nodes of Ranvier

Regular unmyelinated gaps located along a myelinated nerve axon where the myelin sheath is absent.

Stratum Germinativum

The deep epidermal layer of actively dividing cuboidal-to-columnar cells that continuously replaces shedding cells of the stratum corneum in frog skin.

Stratum Spongiosum

The loose outer dermal layer of frog skin containing abundant blood vessels, cutaneous mucous glands, and junctional melanophores.

Tunica Intima

The innermost layer of a blood vessel composed of lining endothelium and a wavy layer of elastic tissue.