Biology Quiz: Basic Questions Of Histology Part- III

Epithelium can be found in the lining of blood vessels, kidneys, and the respiratory tract. Epithelium is a type of tissue that covers the surfaces of organs and structures in the body. It acts as a protective barrier and helps in absorption, secretion, and filtration processes. The lining of blood vessels, kidneys, and respiratory tract all require epithelial tissue to perform their respective functions. Therefore, the correct answer is a, b, and c.

Microvilli are small, finger-like projections found on the surface of certain cells, particularly in areas of absorption. They increase the surface area of the cell, allowing for more efficient absorption of nutrients and other substances. Microvilli are not long and rigid, but rather flexible and short. They are not found in areas with no movement, but rather in areas where absorption is necessary, such as the small intestine. While microvilli are composed of actin filaments, not microtubules, they play an important role in absorption processes.

Gap junctions permit the direct passage of inorganic ions and other water-soluble molecules from cell to cell. These junctions are formed by connexons, which are protein channels that connect the cytoplasm of adjacent cells. Through these channels, small molecules and ions can freely diffuse between cells, allowing for rapid communication and coordination between cells. Tight junctions, zonula adherens, and macula adherens are other types of intercellular junctions, but they do not allow for the direct passage of molecules between cells.

A single long cilium is reffered to as a flagellum, e.g., spermatozoon.

Tight junctions are intercellular junctions that are located on the apical side. These junctions form a barrier between cells, preventing the leakage of molecules and ions between them. They play a crucial role in maintaining the integrity and polarity of epithelial tissues. Zonula adherens, macula adherens, and gap junctions are also intercellular junctions, but they are not specifically located on the apical side.

Macula adherens, also known as desmosomes, are intercellular junctions that connect adjacent cells. They are characterized by intermediate filaments that are attached to an electron dense plaque, forming a hairpin loop. This structure provides strong adhesion between cells, allowing them to withstand mechanical stress and maintain tissue integrity. Tight junctions, zonula adherens, and gap junctions do not have the same hairpin loop structure and attachment to intermediate filaments, making them incorrect choices for this question.

The basal lamina is indeed composed of two layers. It consists of the lamina lucida, which is the upper layer closer to the epithelial cells, and the lamina densa, which is the lower layer closer to the underlying connective tissue. These two layers work together to provide support and anchorage for the epithelial cells, as well as contribute to the filtration and diffusion functions of certain tissues.

Stereocilia are not known as a brush border. Stereocilia are small hair-like structures found on the surface of certain cells in the body, such as in the inner ear. They are involved in detecting sound and are not related to the brush border, which refers to microvilli found on the surface of certain cells in the intestines and kidneys. Therefore, the statement is false.

Microvilli are not composed of microtubules. Microvilli are small, finger-like projections found on the surface of certain cells, particularly in the lining of the small intestine. They are primarily made up of actin filaments, which provide structural support and aid in absorption and secretion functions. Microtubules, on the other hand, are hollow tubular structures made up of proteins called tubulins and are involved in various cellular processes such as cell division, intracellular transport, and maintaining cell shape. Therefore, microvilli do not contain microtubules, making them the correct answer.

Gap junctions are intercellular junctions that have interlocking transmembrane proteins and can be found in cardiac muscle. These junctions allow for direct communication and exchange of ions, small molecules, and electrical signals between adjacent cells. They play a crucial role in coordinating the contraction of cardiac muscle cells, allowing them to work together as a synchronized unit. Tight junctions, zonula adherens, and macula adherens are other types of intercellular junctions, but they do not have the same interlocking transmembrane proteins as gap junctions and do not play the same role in cardiac muscle.

Macula adherens, also known as desmosomes, are intercellular junctions that contain transmembrane proteins, electron dense plaques, and filaments. These junctions provide strong adhesion between cells, allowing them to withstand mechanical stress. The transmembrane proteins in macula adherens form connections with the filaments, which are anchored to the electron dense plaques. This structure helps to maintain the integrity and stability of tissues.

Zonula adherens is an intercellular junction that contains actin filaments. It is a belt-like structure that encircles the cell, connecting adjacent cells together. Actin filaments provide structural support and help in maintaining the integrity of the junction. This junction also plays a role in cell signaling and communication between neighboring cells. Tight junctions, on the other hand, do not contain actin filaments but are responsible for sealing the space between cells to prevent the leakage of molecules. Macula adherens is another type of intercellular junction that uses intermediate filaments for cell adhesion. Gap junctions facilitate direct communication between cells through the exchange of small molecules.

Simple cuboidal epithelium can be found in the thyroid gland and collecting ducts of the kidney. In the thyroid gland, this type of epithelium forms the lining of the follicles, which are responsible for producing and storing thyroid hormones. In the collecting ducts of the kidney, simple cuboidal epithelium lines the tubules that are involved in the reabsorption and concentration of urine. This type of epithelium is well-suited for secretion and absorption due to its single layer of cube-shaped cells. It provides a protective barrier and allows for efficient exchange of substances in these specific organs.

The zonula adherens is an intercellular junction that is located on the basal membrane. It is a belt-like structure that encircles the cell and provides mechanical strength and stability to tissues. It is composed of cadherin proteins that link adjacent cells together, forming a continuous adhesion belt. This junction helps maintain the integrity of epithelial tissues and allows for the transmission of mechanical forces between cells. Tight junctions, gap junctions, and macula adherens are other types of intercellular junctions, but they are not specifically located on the basal membrane.

Simple columnar epithelium is a type of tissue that consists of a single layer of tall, elongated cells. It is specialized for absorption and secretion. The stomach, gall bladder, and intestine are all organs involved in digestion and nutrient absorption. Therefore, it is logical to find simple columnar epithelium in these organs. The tall cells allow for increased surface area, which enhances the absorption of nutrients from the digested food. The thyroid gland, blood vessels, and glomerular capsule do not have a direct role in digestion and nutrient absorption, so it is less likely to find simple columnar epithelium in these structures.

Basal lamina = lamina lucida + lamina densa

Simple squamous epithelium is a thin, single layer of flat cells that allows for easy diffusion of substances. It is found in areas where diffusion and filtration are important functions. In blood vessels, it lines the inner walls, allowing for the exchange of oxygen and nutrients with surrounding tissues. In the kidney, it forms the glomerular capsule, where filtration of blood occurs. In the pleural and peritoneal cavities, it lines the walls, reducing friction during movement. In pulmonary alveoli, it makes up the thin walls, facilitating the exchange of gases during respiration.

The basement membrane is composed of three layers: the lamina lucida, the lamina densa, and the reticular lamina. The lamina lucida is the innermost layer, located adjacent to the epithelial cells. It is composed of proteins and glycoproteins that provide a smooth surface for cell adhesion. The lamina densa is the middle layer and is made up of collagen fibers that provide strength and stability to the basement membrane. The reticular lamina is the outermost layer and consists of reticular fibers and ground substance that support and anchor the basement membrane to the underlying connective tissue.