Dr. Kallie Mini Q2

Mast cells possess receptor molecules on their surface for IgE. IgE is an antibody that plays a key role in allergic reactions. When IgE binds to its specific receptors on mast cells, it triggers the release of inflammatory mediators such as histamine, which leads to the characteristic symptoms of allergies such as itching, redness, and swelling. This interaction between IgE and mast cells is an important part of the immune response against parasitic infections but can also result in hypersensitivity reactions in individuals with allergies.

Fibroblasts are generally regarded as the principal cell type of connective tissue. They are responsible for producing and maintaining the extracellular matrix, which provides structural support to the tissue. Fibroblasts also play a crucial role in wound healing and tissue repair by synthesizing collagen and other components of the extracellular matrix. Other cell types mentioned, such as plasma cells, mast cells, adipocytes, and osteoclast cells, have different functions and are not considered the principal cell type of connective tissue.

During the process of fertilization, enzymes released from cortical granules cause a conformational change of the zona pellucida and oocyte plasma membrane. This conformational change prevents any other sperm from penetrating the oocyte, ensuring that only one sperm is able to fertilize the egg. This mechanism is important for maintaining the genetic integrity of the resulting embryo and preventing polyspermy, which could lead to abnormal development.

Intermediate filaments are a type of cytoskeletal protein that provide mechanical stability to cells. They form a network of fibers that help to maintain the structural integrity of cells and tissues, especially under mechanical stress. Unlike microfilaments and microtubules, intermediate filaments are not involved in generating movement or producing specific cellular structures like microvilli or flagella. Instead, their main function is to provide support and stability, making them essential for maintaining the shape and strength of cells.

During the second week of development, the syncytiotrophoblast erodes the lining of the maternal blood vessels to establish the primitive uteroplacental circulation. This process allows for the exchange of nutrients, gases, and waste products between the mother and the developing embryo. The syncytiotrophoblast is a multinucleated layer of cells that forms the outermost layer of the blastocyst and plays a crucial role in the implantation and development of the placenta. By eroding the maternal blood vessels, the syncytiotrophoblast creates a connection between the maternal and fetal circulatory systems, enabling the exchange of materials necessary for the embryo's growth and development.

The trophoblast cells differentiate into syncytiotrophoblast and cytotrophoblast during embryonic development. This process occurs in the early stages of pregnancy and is essential for the formation of the placenta. The syncytiotrophoblast is responsible for implantation and invasion into the uterine wall, while the cytotrophoblast helps in the formation of the chorionic villi. Together, these two cell types play a crucial role in supporting the developing embryo and facilitating nutrient and waste exchange between the mother and the fetus.

Microvilli are finger-like projections found on the surface of certain cells, such as the cells lining the small intestine. These structures have a core of actin microfilaments, which provide support and stability. They are involved in the movement of materials over the cell surface, such as the absorption of nutrients in the small intestine. The actin microfilaments within microvilli can also undergo contraction, allowing for movement and changes in shape of the microvilli. Therefore, the correct answer is that microvilli have a core of actin microfilaments.

During the fertilization process, enzymes released from the cortical granules cause the oocyte plasma membrane and the zona pellucida to undergo a conformational change. This change in the plasma membrane and zona pellucida prevents any additional sperm from penetrating the oocyte, ensuring that only one sperm is able to fertilize the egg. This process is known as the zona reaction and is necessary for successful fertilization to occur.

Zonula adherens is a cell junction that connects adjacent cells. Cadherins are calcium-dependent proteins that are present on the plasma membrane and play a role in cell-cell adhesion. In zonula adherens, cadherins bind to actin microfilaments through the proteins vinculin and alpha actinin. This binding helps to stabilize the junction and maintain cell-cell adhesion. Therefore, the statement that cadherins bind to actin microfilaments via vinculin and alpha actinin is correct.

Monocytes are a type of white blood cell that can differentiate into macrophages. Macrophages play a crucial role in the immune system by engulfing and digesting pathogens, dead cells, and other debris. Monocytes are produced in the bone marrow and circulate in the bloodstream. When they migrate to tissues, they transform into macrophages. Therefore, monocytes are the correct answer as they have the ability to differentiate into macrophages.

Dynein arms are responsible for the movement of cilia. They use ATPase enzymes to generate the energy required for ciliary movement. If the dynein arms lack the ATPase enzyme, they will be unable to generate the necessary energy, resulting in the lack of movement of the cilia.

Type IV collagen and proteoglycans are found primarily in the lamina densa of the basement membrane. The lamina densa is the middle layer of the basement membrane and is responsible for providing structural support and filtration. Type IV collagen is the main structural component of the lamina densa, forming a mesh-like network that gives the basement membrane its strength. Proteoglycans, on the other hand, help to regulate the permeability and filtration properties of the basement membrane. Together, type IV collagen and proteoglycans play a crucial role in maintaining the integrity and function of the basement membrane.

During the 2nd week of development, the primitive uteroplacental circulation is established as a result of the activity of syncytiotrophoblast cells on maternal sinusoids. This means that the syncytiotrophoblast cells, which are part of the developing placenta, interact with the maternal sinusoids (blood vessels) to establish a circulation system that allows for the exchange of nutrients and waste products between the mother and the developing embryo. This is an important step in the development of the placenta and ensures that the growing embryo receives the necessary nutrients for its development.

Microvilli are small, finger-like projections found on the surface of certain cells. They are made up of actin microfilaments, which are thin protein fibers that provide structural support and allow the microvilli to maintain their shape. Actin microfilaments also play a role in the movement and contraction of microvilli, allowing them to increase the surface area of the cell and aid in functions such as absorption and secretion. Therefore, the correct answer is that microvilli are made of actin microfilaments.

Stereocilia are the correct answer because they are unique to the cells lining the epididymis. Stereocilia are long, nonmotile, microvilli-like projections that are found in the epididymis and are involved in the absorption and secretion of substances. Unlike cilia, which are found in many other types of cells, stereocilia are only present in the cells lining the epididymis. Therefore, stereocilia are the surface specialization that is specific to the cells of the epididymis.

Integrins are transmembrane proteins that connect the cytoskeleton of a cell to the extracellular matrix (ECM). They play a crucial role in cell adhesion and signaling. In this case, integrins are responsible for attaching the plasma membrane to the basal lamina on the basal side of the cell. This attachment is important for maintaining the structural integrity of the cell and for facilitating communication between the cell and its surrounding environment.

During an allergic reaction to bee venom, the correct statement is that IgE production from plasma cells binds to the plasma membrane of mast cells. This binding triggers the release of histamine, heparin, and leukotrienes from mast cells, causing the allergic symptoms. The other statements are incorrect as they do not accurately describe the sequence of events in an allergic reaction to bee venom.

The correct answer is "Has lots of ground substance." Loose areolar connective tissue is characterized by having a significant amount of ground substance, which is a gel-like substance that fills the space between cells and provides support and cushioning. This tissue also contains a variety of cells, such as fibroblasts, macrophages, and mast cells. It is highly vascular, meaning it has a rich blood supply. Loose areolar connective tissue is found in various parts of the body, including the skin, mucous membranes, and around organs, where it provides flexibility and support while allowing for movement.

Loose areolar connective tissue is not composed of a dense arrangement of collagen fibers. Instead, it has a loose arrangement of collagen fibers, which allows for flexibility and movement. This tissue type is characterized by its abundance of ground substance and various cell types. It is found surrounding glandular units and small blood vessels.

Vitamin C influences the hydroxylation of specific proline and lysine residues in the RER during collagen biosynthesis. Hydroxylation of these residues is essential for the proper formation and stability of collagen molecules. Vitamin C acts as a cofactor for the enzymes involved in the hydroxylation process, specifically prolyl hydroxylase and lysyl hydroxylase. Without sufficient vitamin C, the hydroxylation process is impaired, leading to defective collagen synthesis and various connective tissue disorders, such as scurvy.

Pseudostratified columnar epithelium is a type of epithelial tissue where all cells make contact with the basal lamina. This means that every cell in this tissue is in direct contact with the underlying basement membrane. The nuclei of the cells may be at different heights, giving the appearance of stratification, but all cells still maintain contact with the basal lamina. This type of epithelium is commonly found in the respiratory tract, where it helps to protect and move mucus and particles out of the airways.

Proteoglycans are composed of a core protein with attached glycosaminoglycan (GAG) chains. GAGs have a high negative charge due to the presence of sulfate or carboxyl groups. This negative charge attracts cations like sodium (Na+) and binds to water molecules, creating a hydrated gel-like substance in the extracellular matrix. This property allows proteoglycans to provide resistance to compression and act as a lubricant in tissues. Therefore, the statement that the glycosaminoglycans of proteoglycans have a high negative charge that attracts cations and binds to water molecules is correct.

By the end of the third week, the mesoderm formed from the epiblast by invagination at the primitive streak has been organized into three general regions. One of these regions, called the paraxial mesoderm, will give rise to somites. The paraxial mesoderm is responsible for the development of the axial skeleton, skeletal muscles, and dermis of the back.

The correct answer is that at around 5-6 days, the blastocyst loses its zona pellucida and implants on the endometrium as a result of the trophoblast layer. This statement accurately describes the process of implantation, which occurs during the early stages of pregnancy. The blastocyst, a hollow ball of cells, attaches to the endometrial layer of the uterus and begins to invade the tissue. This attachment is facilitated by the trophoblast layer, which helps the blastocyst to implant and establish a connection with the maternal blood supply. The loss of the zona pellucida, a protective layer surrounding the blastocyst, is necessary for this process to occur.

Proteoglycans in connective tissue contain glycosaminoglycans that possess a high negative charge due to the sulfate and carboxyl groups. This negative charge allows them to attract and bind large amounts of water molecules, contributing to the hydration and lubrication of the tissue. The proteins of proteoglycans are present in smaller amounts compared to the glycosaminoglycans. Proteoglycans are composed of a core protein and a branched carbohydrate residue. They also have binding sites for collagen type II, which allows them to interact and contribute to the structural integrity of the connective tissue.

In the absence of fertilization, the corpus luteum degenerates and forms scar tissue called the corpus albicans. This is because the corpus luteum is responsible for producing hormones that support pregnancy, such as progesterone. If fertilization does not occur, there is no need for the corpus luteum to continue producing these hormones, so it begins to break down and eventually forms scar tissue. This process prepares the body for the next menstrual cycle.

The statement that proteins can only be associated with the membrane as peripheral proteins is incorrect. Proteins can be associated with the plasma membrane in multiple ways, including as integral proteins that span the entire membrane or as peripheral proteins that are loosely attached to the membrane surface.

Epithelia are NOT normally separated by large (2 microns) intercellular spaces. Epithelial cells are tightly packed and form continuous sheets, with minimal space between them. This close arrangement allows epithelia to function as barriers and selectively regulate the movement of substances.

Receptor sites for ligands or hormones are typically located on the external side of the plasmalemma, and they are formed by the carbohydrate portions of membrane proteins. This allows for the binding of specific ligands or hormones to initiate a cellular response. FSH does not bind to receptor sites on the thyroid gland, and ACTH does not bind to receptor sites on the thyroid gland either. The lipid bilayer of the phospholipids does not act as receptor molecules for ligands. Therefore, the correct answer is that the receptor sites for ligands or hormones are due to the carbohydrate portions of membrane proteins on the external side of the plasmalemma.

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Phospholipids with unsaturated fatty acids tend to enhance fluidity of the membrane because the presence of double bonds in the fatty acid chains creates kinks in the hydrocarbon tails, preventing close packing of the phospholipids. This increases the fluidity and flexibility of the membrane, allowing for easier movement of molecules and proteins within the lipid bilayer.

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The anterior pituitary gland is derived from ectoderm. During embryonic development, the pituitary gland forms from a structure called Rathke's pouch, which is an invagination of the ectodermal tissue in the roof of the mouth. This ectodermal tissue then differentiates and gives rise to the anterior pituitary gland, which plays a crucial role in the regulation of various hormones in the body.

Pairing of homologous chromosomes occurs in prophase 1 of meiosis 1. During this phase, homologous chromosomes come together and form pairs, a process called synapsis. This pairing is essential for the exchange of genetic material between homologous chromosomes, known as crossing over, which increases genetic diversity. The other statements are incorrect: DNA duplication occurs in S phase before meiosis, the genetic material produced in each cell during meiosis is not identical due to crossing over, non-disjunction can occur in meiosis II, and separation of chromatids occurs during anaphase 2 of meiosis 2.

Lipid asymmetry refers to the uneven distribution of phospholipids in the lipid bilayer of the plasmalemma. This asymmetry is maintained by the presence of phospholipids with different fatty acid compositions, specifically saturated and unsaturated fatty acids. The presence of both types of fatty acids contributes to the asymmetry of the lipid bilayer.

Primary oocytes are indeed arrested in the diplotene stage of prophase 1 before birth. During fetal development, oogonia undergo mitotic divisions to form primary oocytes, which then enter meiosis. However, they are arrested in the diplotene stage until puberty, when they resume meiosis and complete the first meiotic division. Only a small number of primary oocytes are activated each menstrual cycle, and the rest degenerate over time. Therefore, all primary oocytes are arrested in the diplotene stage before birth.

During the first two weeks of development, the prochordal plate develops from the hypoblast layer.

The surge of luteinizing hormone (LH) initiated by high estrogen levels causes the oocyte of a mature Graafian follicle to complete the 1st meiotic division just prior to ovulation. LH surge is necessary for the release of the mature egg from the follicle. High estrogen levels stimulate the hypothalamus to release gonadotropin-releasing hormone (GnRH), which in turn triggers the release of LH from the anterior pituitary gland. LH surge also leads to the rupture of the follicle and the release of the oocyte.

The carbohydrate portion of membrane proteins act as receptor sites for ligands or hormones. This is because the carbohydrate chains attached to membrane proteins can act as recognition sites for specific molecules, allowing them to bind and initiate cellular responses. These carbohydrate chains can also contribute to the structural stability and proper folding of membrane proteins. Therefore, the statement correctly describes the role of the carbohydrate portion of membrane proteins in acting as receptor sites for ligands or hormones.

During prophase I of meiosis I, homologous chromosomes pair up and undergo a process called synapsis. This pairing is essential for the exchange of genetic material between the chromosomes, known as crossing over. Therefore, the statement that pairing of homologous chromosomes occurs in prophase I of meiosis I is correct.

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During collagen biosynthesis, specific proteases remove registration peptides, which are sequences of amino acids that serve as signals for the correct folding and assembly of the procollagen molecule. This removal of registration peptides occurs outside the cell membrane, specifically in the extracellular space. This step is crucial for the formation of mature collagen fibrils. The other statements in the options are not correct. Hydroxylation of proline residues occurs in the endoplasmic reticulum, not the Golgi Apparatus. The procollagen molecule remains soluble within the cytoplasm until it is secreted. Glycosylation of hydroxylysines occurs in the endoplasmic reticulum, not in clathrin vesicles migrating to the plasma membrane. The movement of secretory vesicles involves both actin microfilaments and microtubules.

Prophase is the stage of mitosis where the chromosomes condense and become visible. It is also during prophase that the nuclear envelope breaks down. However, the duplication of the centrioles actually occurs during the previous stage, called interphase, and not during prophase. Therefore, the statement that "Prophase - duplication of the centrioles" is incorrect.

Estrogens produced by the granulosa cells within the growing follicles stimulate the proliferation and regeneration of the endometrial lining. This is because estrogens play a crucial role in preparing the uterus for implantation and maintaining the endometrial lining during the menstrual cycle. They promote the growth and development of the endometrium, ensuring it is receptive to a fertilized egg.

Cells having basal infoldings are characteristic of ion transport. Basal infoldings are specialized membrane structures that increase the surface area of the cell, allowing for more ion channels and transporters to be present. This enables the cell to efficiently transport ions across the membrane. Therefore, the presence of basal infoldings is indicative of a cell's ability to perform ion transport.

The registration peptides in procollagen molecules make them soluble.

Pemphigus vulgaris is an autoimmune disease that affects the desmoglein of macula adherens. Desmogleins are a type of cadherin protein that are important for cell adhesion in the epidermis. In pemphigus vulgaris, autoantibodies are produced against desmogleins, leading to the breakdown of cell adhesion and the formation of blisters in the skin and mucous membranes. This is why the desmoglein of macula adherens is affected in this disease.

Laminin is a protein that is found in the extracellular matrix and is responsible for binding integral proteins to collagen type IV. Laminin forms a network of proteins that helps to support and stabilize the basement membrane, which is composed of collagen type IV. This binding between laminin and collagen type IV is crucial for maintaining the structural integrity and function of tissues and organs. Integrins, reticular fibrils (collagen type III), anchoring fibrils (collagen type VII), and proteoglycans are not directly involved in binding integral proteins to collagen type IV.

Osteoblasts are primarily involved in the synthesis of collagen type 1. Collagen type 1 is the main component of bone tissue, and osteoblasts are responsible for the formation and mineralization of bone. They produce and secrete collagen type 1, which provides the structural framework for bone and contributes to its strength and flexibility. Chondrocytes are involved in the synthesis of collagen type 2, which is found in cartilage. Osteoclast cells are responsible for bone resorption, while macrophages are involved in immune responses. Chondroblasts are immature cartilage cells and are not directly involved in the synthesis of collagen type 1.

The kinetochore is not involved in the addition of tubulin dimers during anaphase. The kinetochore is a protein structure located on the centromere of a chromosome and is responsible for attaching the chromosome to the spindle fibers during cell division. It helps in the movement of chromosomes during mitosis and meiosis, but it does not play a role in the addition of tubulin dimers to microtubules during anaphase.