Human embryology is the study of the development of gametes, fertilization, and of the following developmental stages from human embryo to fetus. The MCAT fundamentals for the topic include the developmental narrative from ovulation through implantation and the development of tissues and structures during approximately the first two months of embryonic and fetal development. This descriptive level should be integrated with basic understanding of processes at the molecular, cellular and tissue level such as the behavior of morphogens on signaling pathways, gene expression, and cellular differentiation and how morphogenic movements can bring cell sheets into new spatial relationships making possible new phases of signaling and response between them.
Mammalian Tissues and Histology Images
Conceptual Vocabulary Self-Test
Basic Terms Crossword Puzzle
Basic Puzzle Solution
Conceptual Vocabulary for Human Embryology
A biological tissue is a collection of interconnected cells that perform a similar function within an organism.
Epithelium is a tissue composed of layers of cells which line the cavities and surfaces of structures throughout the body. It is also the type of tissue of which many glands are formed.
Connective tissue is largely a category of exclusion rather than one with a precise definition, but most tissues in this category are involved in structure and support, derived from mesoderm, and characterized by the traits of non-living tissue.
Squamous epithelium is an epithelium characterised by its most superficial layer consisting of flat, scale-like cells.
Cuboidal epithelia are cube-shaped epithelial cells.
Simple cuboidal eplithelia are epithelial cells with a cuboidal shape arranged in a single layer.
Stratified cuboidal epithelia is epithelial tissue composed of cuboidally shaped cells arranged in multiple layers.
Columnar epithelia are epithelial cells whose heights are at least twice their width.
Simple columnar epithelium is made up of one layer of cells that are relatively thick and protective of the underlying tissues due to its elongated shape.
Stratified columnar epithelia have several layers, with columnar cells as the outermost of these.
Goblet cells are glandular simple columnar epithelial cells whose sole function is to secrete mucus.
Adipose tissue or fat is loose connective tissue composed of adipocytes.
Histology is the study of tissue sectioned as a thin slice, viewed under a microscope.
The basement membrane is a structure that supports overlying epithelial or endothelial cells.
The endothelium is the thin layer of cells that line the interior surface of blood vessels.
A gland is an organ in an animal's body that synthesizes a substance for release, often into the bloodstream (endocrine) or onto a surface (exocrine).
Histopathology refers to the microscopic examination of tissue in order to study the manifestations of disease.
Fixation is a chemical process used in the fields of histology, pathology, and cell biology by which biological tissues are preserved from decay.
Antonie van Leeuwenhoek (1632 - 1723) was a Dutch tradesman and scientist who is commonly known as the Father of Microbiology.
Transitional epithelia is a type of tissue consisting of multiple layers of epithelial cells which can contract and expand.
The basal lamina is a layer on which epithelium sits and which is secreted by the epithelial cells.
The endocardium is the innermost layer of tissue that lines the chambers of the heart.
The apical membrane of a polarized cell is the part of the plasma membrane that forms its lumenal surface, distinct from the basolateral membrane.
The basolateral membrane of a polarized cell is the part of the plasma membrane that forms its basal and lateral surfaces, distinct from the lumenal or apical surface.
Areolar connective tissue (or loose connective tissue) is the most widely distributed connective tissue type in the body. It can be found in the skin as well as in places that connect epithelium to other tissues.
The extracellular matrix is the extracellular part of animal tissue that usually provides structural support to the cells in addition to performing other functions. It is the defining feature of connective tissue in animals.
Dense connective tissue has collagen fibers as its main matrix element.
Fibrous connective tissue is a type of connective tissue which has relatively high tensile strength, due to a relatively high concentration of collagenous fibers.
Adipocytes are the cells that primarily compose adipose tissue, specialized in storing energy as fat.
White adipose tissue is one of the two types of adipose tissue found in mammals, in humans, composing as much as 20% of the body weight in men and 25% of the body weight in women.
Brown adipose tissue is present in many newborn or hibernating mammals as well as migratory birds. Its primary purpose is to generate body heat.
The optical microscope, often referred to as a light microscope, is a type of microscope which uses visible light and a system of lenses to magnify images of small samples.
The olfactory epithelium is a specialized epithelial tissue inside the nasal cavity that is involved in smell.
The lamina propria is a thin layer of loose connective tissue which lies beneath the epithelium and together with the epithelium constitutes the mucosa.
The microvilli are structures that increase the surface area of cells by approximately 600 fold, thus facilitating absorption and secretion.
Mucins are a family of large, heavily glycosylated proteins which are secreted on mucosal surfaces and in saliva.
The mesothelium is a membrane that forms the lining of several body cavities: the pleura, peritoneum and pericardium.
A fibroblast is a type of cell that synthesizes and maintains the extracellular matrix of many animal tissues.
Cell adhesion molecules are proteins located on the cell surface involved with the binding with other cells or with the extracellular matrix.
Stroma refers to the connective, non-functional supportive matrix or framework of a biological cell, tissue, or organ.
Reticular connective tissue is a type of loose irregular connective tissue which has a network of reticulated fibers that form a soft skeleton to support the lymphoid organs.
A histological section is a thin slices of tissue applied to a microscopic slide, usually around 5 to 10 micrometres thick, to be viewed under a microscope.
A pseudostratified epithelium is a type of epithelium that, though comprising only a single layer of cells, has its cell nuclei positioned in a manner suggestive of stratified epithelia.
Ground substance is a term for the non-collagenous components of the extracellular matrix.
Elastic fibers (or yellow fibers) are bundles of protein elastin found in connective tissue and produced by fibroblasts and smooth muscle cells in arteries.
Immunohistochemistry refers to the process of localizing proteins in the cells of a tissue section by exploiting the principle of the specific binding of antibodies to antigens.
Hematoxylin and eosin stain is a popular staining method in histology. It is the most widely used stain in medical diagnosis.
A counterstain is a histological stain with color contrasting to the principal stain, making the stained structure more easily visible.
Eosinophilic means loves eosin, and refers to the staining of certain tissues, cells, or organelles after they been washed with eosin, a dye.
Buccal mucosa is mucous membrane of the inside of the cheek.
The germinal epithelium of Waldeyer is a layer of columnar cells covering the surface of the ovary.
Hyaluronan, also called hyaluronic acid, is a non-sulfated glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues.
A microtome is a mechanical instrument used to cut biological specimens into very thin segments for microscopic examination.
Immunofluorescence is the labeling of antibodies or antigens with fluorescent dyes.
In situ hybridization is a type of hybridization that uses a labeled complementary DNA or RNA probe to localize a specific DNA or RNA sequence in a portion or section of tissue.
A mucocutaneous zone is a region of skin comprising both mucosa and cutaneous skin.
Selectins are a family of cell adhesion molecules that are single-chain transmembrane glycoproteins which share similar properties to C-type lectins due to a related amino terminus and calcium-dependent binding.
Fluorescein is a fluorophore commonly used in microscopy, as well as in forensics and serology to detect latent blood stains.
The green fluorescent protein is a protein of great use to fluorescence microscopy, comprised of 238 amino acids from the jellyfish Aequorea victoria that fluoresces green when exposed to blue light.
Van Gieson's Stain is a mixture of Picric Acid and Acid Fuchsin, which represents the simplest method of differential staining of Collagen and other Connective Tissue.
Periodic acid-Schiff is a staining method used in histology and pathology primarily to identify glycogen in tissues.
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