Dr Kallie Mini Part 3

Fibroblasts are the correct answer because they are the main cell type responsible for producing collagen, proteoglycans, and glycosaminoglycans. Collagen is the main structural protein in the extracellular matrix, while proteoglycans and glycosaminoglycans are important components of the matrix that provide support and hydration to tissues. Fibroblasts are found in connective tissues throughout the body and play a crucial role in tissue repair and remodeling. They are able to synthesize and secrete these extracellular matrix components, making them essential for maintaining tissue structure and function.

IgE is a type of antibody that is secreted from plasma cells. It binds to the IgE receptor on mast cells, triggering an immediate hypersensitivity reaction. This binding causes the mast cells to release various chemical mediators, such as histamine, which contribute to the allergic response. The other options mentioned in the question are not correct as they do not accurately describe the mechanisms involved in immediate hypersensitivity reactions.

The inner mass of cells from the blastocyst stage of development eventually gives rise to the epiblast and hypoblast. These two cell layers are responsible for the formation of the embryo proper. The epiblast gives rise to the three primary germ layers (ectoderm, mesoderm, and endoderm), which go on to form all the tissues and organs of the body. The hypoblast, on the other hand, contributes to the formation of extra-embryonic structures like the yolk sac.

Syncytiotrophoblast cells are involved in eroding maternal sinusoids to establish the primitive uteroplacental circulation. During the second week of development, the syncytiotrophoblast cells invade the maternal sinusoids in the endometrium, allowing for the establishment of the primitive uteroplacental circulation. This process is crucial for the exchange of nutrients and waste between the maternal and embryonic circulations. The other options are not correct because lacunae spaces are formed in the extraembryonic mesoderm, epiblast cells are not involved in establishing the uteroplacental circulation, the cytotrophoblast layer does not erode the maternal endometrium, and the hypoblast layer does not give rise to the amnion.

Follicular cells of the primordial follicle produce the oocyte maturation inhibitory substance. These cells surround the developing oocyte and play a crucial role in its maturation process. They release various substances, including the oocyte maturation inhibitory substance, which helps regulate the timing of oocyte maturation and prevents premature maturation. This substance ensures that the oocyte is fully developed and ready for fertilization before it is released from the ovary during ovulation.

Vitamin C is required for the hydroxylation of proline residues in the rough endoplasmic reticulum. This hydroxylation step is important for the proper folding and stability of collagen molecules. Without vitamin C, the hydroxylation process is impaired, leading to the synthesis of structurally weak collagen. This is the main reason why vitamin C deficiency can result in a disease called scurvy, which is characterized by weakened connective tissues and impaired wound healing.

The correct answer is that the released egg is a secondary oocyte arrested at metaphase II of meiosis II. During ovulation, the secondary oocyte is released from the ovary. It is in the metaphase II stage of meiosis II, which means it has already gone through the first meiotic division and is ready to be fertilized by a sperm. If fertilization occurs, the secondary oocyte will complete meiosis II and become a mature egg. If fertilization does not occur, the secondary oocyte will degenerate.

Loose areolar connective tissue is characterized by having lots of ground substance, an abundance of cell types, and scattered fibers. This tissue type provides support and flexibility to various organs and structures in the body. The presence of ground substance allows for the diffusion of nutrients and waste products, while the scattered fibers provide strength and support. The abundance of cell types, such as fibroblasts and immune cells, contributes to the tissue's ability to repair and defend against pathogens.

slide 24 and 25

When a sperm touches the oocyte plasma membrane, a zonal reaction occurs. This reaction causes a conformational change in both the oocyte membrane and the zona pellucida. This change allows the sperm to penetrate the zona pellucida and reach the oocyte for fertilization. The statement correctly describes the process of fertilization and the role of the zonal reaction in allowing sperm entrance.

The anterior pituitary gland is derived from the ectoderm. The ectoderm is one of the three primary germ layers that form during early embryonic development. It gives rise to various structures in the body, including the nervous system, skin, and some glands. The anterior pituitary gland is a major endocrine gland located in the brain that produces and releases several important hormones. Since it is derived from the ectoderm, it is the correct answer in this case.

The zonal reaction does not allow other sperms to penetrate the oocyte. Instead, it prevents additional sperms from entering the oocyte by causing the zona pellucida to harden and become impenetrable.

At the neuromuscular junction, synaptic vesicles release acetylcholine into the synaptic cleft. This is the correct process that occurs during the transmission of a nerve impulse from a motor neuron to a muscle cell. Acetylcholine is a neurotransmitter that is released from the synaptic vesicles and diffuses across the synaptic cleft to bind to receptors on the postsynaptic membrane of the muscle cell, initiating muscle contraction. The other options mentioned in the question are not accurate descriptions of the process at the neuromuscular junction.

The intraembryonic mesoderm is derived from the epiblast. During embryonic development, the epiblast differentiates into three germ layers: ectoderm, mesoderm, and endoderm. The mesoderm is located between the ectoderm and endoderm and gives rise to various structures such as muscles, bones, connective tissues, and cardiovascular system. Therefore, the correct answer is epiblast.

At the time of birth in an XX individual, the gonad will contain primordial follicles with primary oocytes of prophase I. This is because during fetal development, the oogonia (precursor cells) undergo mitotic divisions to form primary oocytes. These primary oocytes are arrested in prophase I of meiosis and are surrounded by a single layer of flattened cells, forming primordial follicles. These primordial follicles are present in the ovaries at birth and will eventually develop and mature during the reproductive years. Therefore, the presence of primordial follicles with primary oocytes of prophase I is the most appropriate answer.

Unequal cell size is not considered to be significant to meiosis because it does not directly affect the process of genetic recombination or the separation of homologous chromosomes. Meiosis is primarily concerned with the exchange of genetic information through crossing over, the pairing of homologous chromosomes, and the independent assortment of maternal and paternal chromosomes. Unequal cell size may occur as a result of meiosis, but it is not a fundamental aspect of the process itself.

During meiosis, the secondary spermatocytes have 23 chromosomes. Meiosis is the process of cell division that occurs in the reproductive cells to produce gametes (sperm or egg cells). It involves two rounds of division, resulting in four daughter cells with half the number of chromosomes as the parent cell. In humans, the parent cell (primary spermatocyte) has 46 chromosomes, and after the first division, the secondary spermatocytes are formed with 23 chromosomes. Therefore, the correct answer is 23 chromosomes.

After the secondary oocyte is fertilized, the syncytiotrophoblast cells in the developing embryo produce human chorionic gonadotropin (hCG). This hormone maintains the viability of the corpus luteum, preventing it from degenerating. The corpus luteum is responsible for producing progesterone, which is essential for maintaining the pregnancy. If the corpus luteum degenerates, progesterone levels drop and the uterine lining is shed, resulting in menstruation. Therefore, the production of hCG by the syncytiotrophoblast cells ensures the survival of the corpus luteum and the maintenance of the pregnancy.

Stratified squamous keratinized epithelium is avascular, meaning it does not have blood vessels. The other statements are correct - it is found covering the surface of the skin, the basal layer of cells may be cuboidal or columnar and rest on the basal lamina, some of its cells rest on the basal lamina, and the apical cells are squamous and dead.

During the second week of development, the embryo proper is composed of epiblast and hypoblast. These two layers are part of the inner cell mass, which is formed after the blastocyst stage. The epiblast is the upper layer and gives rise to the three primary germ layers, which eventually develop into all the tissues and organs of the body. The hypoblast is the lower layer and contributes to the formation of extraembryonic structures like the yolk sac. Together, the epiblast and hypoblast play crucial roles in the early development of the embryo.

The prochordal plate is a group of tall columnar cells that determine the future site of the mouth cavity. This means that during development, the prochordal plate plays a crucial role in establishing where the mouth will be located in the embryo. It provides important signals and cues for the formation and positioning of the mouth structures.

The posterior fontanelle is a soft spot on the back of a baby's head where the skull bones have not yet fully fused. It is typically closed by the age of 6 months. During the first few months of life, the fontanelle allows for the baby's brain to grow and provides flexibility for the skull bones to shift during delivery. As the baby grows, the fontanelle gradually closes and becomes less noticeable. By the age of 6 months, it is expected that the posterior fontanelle will be fully closed.

Classification of exocrine glands –based on :
1. Nature of cells – (unicellular versus multicellular)
2. Nature of duct system – (simple vs compound )
3. Shape of secretion unit – (tubular vs alveolar (acini)
vs tubuloalveolar )
4. Nature of secretion product – (mucus vs serous vs seromucus)
5. Mode of secretion – (holocrine vs merocrine vs apocrine )
from slide #52

Epiblast cells that enter the primitive node give rise to the notochordal rod that extends to the prochordal plate. The notochordal rod is an essential structure in early embryonic development, providing structural support and signaling cues for the formation of the neural tube. It plays a crucial role in the formation of the axial skeleton and the development of the central nervous system. The prochordal plate is a specialized region of the endoderm that is involved in the formation of the oropharyngeal membrane.

LH, or luteinizing hormone, stimulates the formation of the corpus luteum. The corpus luteum is a temporary endocrine structure that develops from the ruptured ovarian follicle after ovulation. It secretes progesterone, which is important for preparing the uterus for potential implantation of a fertilized egg. LH triggers the transformation of the follicle into the corpus luteum, ensuring the production of progesterone and supporting the early stages of pregnancy if fertilization occurs.

The correct answer is that nutrients for chondrocytes of cartilage are derived from blood capillaries found in the perichondrium. Chondrocytes are the cells that make up cartilage, and they require nutrients to survive and function properly. These nutrients are obtained from blood capillaries that are present in the perichondrium, which is the connective tissue that surrounds the cartilage. The perichondrium provides a source of oxygen and nutrients to the chondrocytes, allowing them to maintain their metabolic activities and support the health of the cartilage tissue.

FSH (follicle-stimulating hormone) plays a crucial role in the development of the follicles before ovulation. It stimulates the granulosa layer of cells, which are located inside the follicles, to secrete estrogen. Estrogen is important for the growth and maturation of the follicles. It also helps in the development of the endometrium, the lining of the uterus, in preparation for potential implantation of a fertilized egg. Therefore, FSH's stimulation of the granulosa layer to produce estrogen is a correct statement regarding the growing follicles before ovulation.

During the time of menstruation, LH (luteinizing hormone) causes the final maturation of the Graafian follicle and the release of the secondary oocyte. This is a correct statement because LH surge triggers ovulation, which is the release of the mature egg from the ovary. The Graafian follicle, which contains the mature egg, ruptures and releases the secondary oocyte into the fallopian tube where it can potentially be fertilized by sperm.

Estrogen is the correct answer because it is the hormone that primarily influences the endometrium during the proliferative phase. During this phase, the endometrium thickens and prepares for potential implantation of a fertilized egg. Estrogen stimulates the growth and development of the endometrial lining, ensuring it is ready to support a pregnancy if fertilization occurs. LH, FSH, Progesterone, and Activin also play important roles in the menstrual cycle, but they do not directly influence the endometrium during the proliferative phase.

ANSWER KEY SHOWS E AS CORRECT ANSWER BUT SLIDE 50 AND 51 MAKE C ALSO A GOOD ANSWER . THEREFORE THIS IS A STUPID QUESTION.