Histología (HS) MCQ Questions

Histology Study Guide

Quiz

What is the stroma of a gland, and what are its key characteristics? The stroma is the supporting tissue of a gland. It is composed of connective tissue that is vascularised and innervated, providing structural support and facilitating the supply of nutrients and removal of waste products for the glandular parenchyma.
Differentiate between exocrine and endocrine glands, providing an example of each from the source material. Exocrine glands secrete their products into ducts that lead to an external or internal epithelial surface, such as the salivary glands releasing saliva into the oral cavity. Endocrine glands, like the thyroid, secrete hormones directly into the bloodstream or lymphatic vessels, lacking a duct system.
Describe the main components and functions of the basal lamina found beneath epithelial tissues. The basal lamina consists of the lamina lucida and the lamina densa, produced by epithelial cells, and the lamina reticularis, produced by connective tissue. Its functions include providing structural support, acting as a molecular filter, influencing cell polarity, and guiding cell migration during tissue repair.
What are the key structural features and functional roles of simple columnar epithelium? Where can this type of epithelium be found? Simple columnar epithelium is composed of a single layer of tall, rectangular cells with nuclei typically located in the basal half. It is often found in mucous membranes like the lining of the intestine and stomach, where it functions in secretion (if goblet cells are present) and absorption (if microvilli are present).
Explain the process of tissue dehydration and why it is a crucial step in histological sample preparation for paraffin embedding. Tissue dehydration involves the gradual removal of water from a tissue sample by immersing it in a series of increasing concentrations of dehydrating agents like alcohol or acetone. This step is essential for paraffin embedding because paraffin is hydrophobic and will not infiltrate tissue containing water, thus preventing proper support for sectioning.
Briefly describe the principles behind haematoxylin and eosin (H&E) staining and what cellular components each dye typically stains. Haematoxylin is a basic dye that stains acidic structures, such as the nucleus (DNA and RNA), in shades of blue to violet, making them basophilic or acidophilic. Eosin is an acidic dye that stains basic structures, like the cytoplasm and collagen, in shades of pink, making them eosinophilic or basophilic.
What are the main characteristics of stratified squamous epithelium, and how does its structure relate to its functions? Stratified squamous epithelium consists of multiple layers of cells, with the superficial layer composed of flattened (squamous) cells. This multi-layered structure provides protection against abrasion and penetration. In the keratinised form (like the epidermis), the addition of keratin provides further waterproofing and resistance to friction.
Compare and contrast the mechanisms of secretion in merocrine, apocrine, and holocrine glands, giving an example of a gland that uses each mechanism. Merocrine glands secrete their products via exocytosis without loss of cytoplasm (e.g., pancreatic acinar glands). Apocrine glands release secretions by pinching off a portion of the apical cytoplasm containing the secretory product (e.g., active mammary glands). Holocrine glands accumulate their secretion within the cytoplasm until the cell ruptures and is released as the secretion (e.g., sebaceous glands).
Describe the major components of the extracellular matrix (ECM) in connective tissue and their primary roles. The ECM in connective tissue consists of ground substance (containing glycosaminoglycans and proteoglycans) and fibres (collagen, elastic, and reticular fibres). The ground substance provides hydration and resistance to compression, while collagen fibres provide tensile strength, elastic fibres allow for stretch and recoil, and reticular fibres form a supportive network.
What are the key distinctions between white (unilocular) and brown (multilocular) adipose tissue in terms of their structure and primary function? White adipose tissue consists of adipocytes with a single large lipid droplet, primarily functioning in long-term energy storage. Brown adipose tissue contains adipocytes with multiple small lipid droplets and numerous mitochondria rich in thermogenin, its main function being the generation of heat.

Answer Key

The stroma of a gland is the supporting tissue, primarily composed of vascularised and innervated connective tissue. It provides structural integrity to the gland, supports the secretory parenchyma (epithelial tissue), and facilitates the transport of nutrients and waste products.
Exocrine glands secrete into ducts leading to a surface; an example from the text is the salivary glands, which release saliva via ducts into the mouth. Endocrine glands secrete hormones directly into the bloodstream without ducts; the thyroid gland is an example that releases hormones into the circulation.
The basal lamina is composed of the lamina lucida (containing glycoproteins like laminin and integrins), the lamina densa (formed by collagen type IV), and the lamina reticularis (containing collagen type III). It provides structural support, acts as a selective barrier for molecule passage, influences cell behaviour and polarity, and aids in tissue repair by guiding cell migration.
Simple columnar epithelium features a single layer of tall, rectangular cells with basally located nuclei. Its functions include secretion (often with goblet cells secreting mucus for lubrication and protection) and absorption (enhanced by microvilli in some locations). This epithelium is found lining the stomach, intestines, and uterine tubes.
Tissue dehydration is the process of gradually removing water from a tissue sample using increasing concentrations of dehydrating agents. It is crucial for paraffin embedding because paraffin, a hydrophobic embedding medium, cannot properly infiltrate and support water-containing tissue. Effective dehydration allows for the subsequent infiltration of paraffin, providing the necessary rigidity for thin sectioning.
Haematoxylin is a basic dye that stains acidic cellular components, such as nucleic acids in the nucleus, a blue-violet colour. Eosin is an acidic dye that stains basic components, primarily proteins in the cytoplasm and extracellular matrix like collagen, a pink colour. This differential staining allows for the visualisation of various cellular and tissue structures under a microscope.
Stratified squamous epithelium is characterised by multiple layers of cells, with the apical layer consisting of flattened squamous cells. This thickness provides a protective barrier against mechanical abrasion, chemical insults, and microbial invasion. In keratinised stratified squamous epithelium (epidermis), the surface layer is composed of dead, keratin-filled cells, enhancing its protective and waterproofing properties.
Merocrine secretion involves the release of secretory products via exocytosis from vesicles at the apical surface of the cell, without any loss of cellular material; the pancreas uses this method to secrete digestive enzymes. Apocrine secretion involves the release of a portion of the apical cytoplasm containing the secretory product; active mammary glands are an example. Holocrine secretion involves the accumulation of secretory product within the cell, followed by the rupture and destruction of the entire cell to release the product; sebaceous glands employ this mechanism to secrete sebum.
The major components of the ECM are glycosaminoglycans (GAGs) and proteoglycans (which form the hydrated ground substance providing resistance to compression and facilitating diffusion), collagen fibres (providing high tensile strength and structural support), elastic fibres (allowing tissues to stretch and recoil), and adhesive glycoproteins like fibronectin (linking cells to the ECM and maintaining tissue organisation).
White adipose tissue is composed of large adipocytes containing a single, large lipid droplet that fills most of the cytoplasm, with the nucleus pushed to the periphery; its primary role is the long-term storage of energy in the form of triglycerides. Brown adipose tissue consists of smaller adipocytes containing multiple small lipid droplets and a high number of mitochondria with thermogenin; its main function is to generate heat through the uncoupling of oxidative phosphorylation.

Essay Format Questions

Discuss the structure and function of the epithelial lining of the small intestine, highlighting the specialisations of its apical domain and the role of the underlying basal lamina in nutrient absorption.
Compare and contrast the formation and functional roles of the different types of glands (exocrine vs. endocrine; unicellular vs. multicellular; based on secretion mechanism), providing specific examples from the source material to illustrate your points.
Explain the process of preparing a histological slide from tissue fixation to staining, emphasising the importance of each step in preserving tissue morphology and allowing for effective microscopic examination.
Describe the composition and organisation of the extracellular matrix in connective tissue, and discuss how variations in its components contribute to the diverse properties and functions of different connective tissue types.
Analyse the structure and function of stratified squamous epithelium in different locations (e.g., epidermis, oral cavity), focusing on how its variations (keratinised vs. non-keratinised) are adapted to the specific challenges faced by these tissues.

Glossary of Key Terms

Acinus (plural Acini): A sac-like cluster of secretory cells in a gland, typically with a narrow lumen.
Adipocyte: A fat cell specialised for the storage of triglycerides.
Apical Domain: The surface of an epithelial cell that faces the lumen or external environment, often containing specialisations like microvilli or cilia.
Basal Lamina: A thin, acellular layer of extracellular matrix located beneath the basal surface of epithelial cells, providing support and acting as a filter.
Basolateral Domain: The surfaces of an epithelial cell that face adjacent cells and the underlying connective tissue.
Collagen: A family of fibrous proteins that provide structural support and tensile strength to connective tissues.
Desmosome: A type of intercellular junction that provides strong adhesion between adjacent cells.
Elastin: A protein that forms elastic fibres in connective tissues, allowing them to stretch and recoil.
Endocrine Gland: A ductless gland that secretes hormones directly into the bloodstream or lymphatic vessels.
Epithelium: A sheet of tightly packed cells that covers body surfaces, lines body cavities, and forms glands.
Exocrine Gland: A gland that secretes its products through ducts onto an epithelial surface.
Extracellular Matrix (ECM): A complex network of proteins and polysaccharides secreted by cells that provides structural and biochemical support to the surrounding cells.
Fibroblast: A type of connective tissue cell that produces and maintains the extracellular matrix, including collagen and elastic fibres.
Gland: An organ or cell that secretes substances.
Glycosaminoglycans (GAGs): Long, unbranched polysaccharides found in the ground substance of the extracellular matrix, often highly hydrated and negatively charged.
Goblet Cell: A unicellular exocrine gland found in the epithelial lining of mucous membranes, specialised for secreting mucus.
Haematoxylin: A basic dye used in histology that stains acidic components (like nucleic acids) blue or violet.
Holocrine Secretion: A mode of secretion where the entire secretory cell is destroyed and released as part of the secretory product.
Lumen: The cavity or channel within a tube or hollow organ.
Macroscopic: Visible to the naked eye, without the aid of a microscope.
Merocrine Secretion: A mode of secretion where secretory products are released from cells via exocytosis without loss of cytoplasm.
Microscopic: Visible only with the aid of a microscope.
Microvilli: Small, finger-like projections of the apical plasma membrane of some epithelial cells that increase surface area for absorption.
Mucin: A glycoprotein found in mucus, responsible for its viscous nature.
Mucus: A viscous fluid secreted by mucous membranes, composed of mucin, water, and other substances, serving to protect and lubricate surfaces.
Paraffin Embedding: A common technique in histology where tissue samples are infiltrated and surrounded by molten paraffin wax, which then solidifies to provide support for thin sectioning.
Parenchyma: The functional tissue of an organ, as opposed to the supporting connective tissue (stroma).
Polarity (Cellular): The structural and functional differences between the apical and basolateral domains of an epithelial cell.
Proteoglycan: A molecule consisting of one or more glycosaminoglycan (GAG) chains covalently attached to a core protein, found in the extracellular matrix.
Reticular Fibres: Fine, branching collagen fibres (type III) that form a supportive network in some tissues.
Stroma: The supporting structural tissue (usually connective tissue) of an organ, as distinguished from the functional parenchyma.
Stratified Epithelium: An epithelium consisting of two or more layers of cells.
Simple Epithelium: An epithelium consisting of a single layer of cells.
Tissue: A group of similar cells and their extracellular matrix that work together to perform a specific function.
Zonula Adherens: A type of intercellular junction that provides adhesion between adjacent cells via actin filaments.
Zonula Occludens (Tight Junction): A type of intercellular junction that seals the space between adjacent epithelial cells, preventing the passage of molecules through the paracellular pathway.

Histología (HS)

Histology Study Guide

Quiz

Answer Key

Essay Format Questions

Glossary of Key Terms

Subtopics

Tema 1. Introducción a la Histología

Tema 2. Matriz Extracelular

Tema 3. Tejido Epitelial

Tema 4. Tejido Conjuntivo

Tema 5. Tejido Sanguíneo

Tema 6. Tejido Adiposo

Tema 7. Cartilaginoso

Tema 8. Tejido Óseo

Tema 9. Tejido Muscular

Tema 10. Tejido Nervioso

Histología (HS) Practicas II

Histología (HS) Practicas I