Histology - Mitosis (Whitefish Blastula)

Summary

Mitosis, the shortest part of the cell cycle, is explored through detailed histo micrographs provided by Digital Histology and Virginia Commonwealth University. The video breaks down the phases of the cell cycle, emphasizing the critical stages of mitosis including prophase, metaphase, anaphase, and telophase, highlighted by variations seen in Whitefish blastula slides. Practical advice for biology students preparing for exams is given, such as examining multiple slides to account for quality variance. The video underscores the importance of understanding interphase artifacts and concludes by acknowledging Digital Histology's contribution to these educational resources, inviting support for future content.

Highlights

• Understanding mitosis and its phases through detailed micrograph study. 🧬
• Prophase marks the beginning of visibility for thread-like chromosomes. 🧵
• Metaphase is notable for the metaphase plate and spindle fiber alignment. 📏
• Anaphase involves chromosome separation to opposite poles. ↔️
• Telophase sees the reformation of the nuclear envelope around chromosomes. 🧪

Key Takeaways

• Mitosis is the fastest part of the cell cycle and involves visible, thread-like chromosomes. 🧵
• Digital Histology provides high-quality micrographs for educational use. 📸
• Practical exams require students to apply conceptual knowledge to real-life specimens and slides. 📚
• Slide quality may vary; examine multiple slides for the best observation. 🔍
• Cytokinesis, the division of cytoplasm, is crucial during telophase for cell separation. ⚛️

Overview

The video by Dr. Bob highlights mitosis, the end of the cell cycle where cells divide and chromosomes become thread-like. With micrographs courtesy of Digital Histology, Dr. Bob guides viewers through each phase, from prophase to telophase, emphasizing mitosis' role in cell cycles. The Whitefish blastula is particularly useful for observing these rapid divisions, aiding biology students in understanding the practical aspects of cellular functions.

Students are advised to examine multiple histological slides for quality assurance as part of their practical exam preparations. Only a few slides might provide the clear view required, given variations due to preparation techniques and staining differences. This practical advice is vital for exams focused on applying classroom knowledge to real-world biological specimens.

The final stages of mitosis, such as telophase and cytokinesis, are underscored as key moments when the cell's cytoplasm splits to form two new cells. Dr. Bob ends with expressions of gratitude to Digital Histology for their resources and encourages viewer support to continue creating more educational content. He shares a link to additional study materials and quizzes for further learning.

Chapters

• 00:00 - 01:00: Introduction and Acknowledgements The chapter begins with an introduction and acknowledgements. The narrator expresses gratitude to the source of histo micrographs that will be used in this and future videos. The mentioned resource is the Digital Histology website, which is affiliated with Virginia Commonwealth University. A link to this website is provided.
• 01:00 - 03:00: Cell Cycle Overview This chapter provides an overview of the cell cycle, highlighting its role as an alternation between growth or function and cell division. It includes a schematic representation of the cycle, particularly focusing on the phase of mitosis.
• 03:00 - 05:00: Whitefish Blastula and Practical Advice The chapter discusses the concept of mitosis, emphasizing its brevity compared to the rest of the cell cycle. It explains that the term 'mitosis' is derived from the Greek word 'mitos,' meaning 'thread,' due to the appearance of chromosomes during this phase. The chapter also introduces the phase between mitosis, referred to as the 'in-between phase' of the cell cycle.
• 05:00 - 06:30: Histological Slide Examination This chapter discusses the examination of histological slides, focusing on the interphase of cells. It highlights that interphase cannot be divided into distinct histological phases, meaning they cannot be seen visually under a microscope. Instead, interphase is divided into functional phases based on cellular activity. The first of these is the G1 phase, considered the first growth phase following cell division.
• 06:30 - 09:00: Interphase Interphase is a preparatory phase prior to cell division. It includes growth to ensure the cell does not get smaller with each division. Following this is the S phase, where chromosome duplication occurs. Before mitosis begins, a shorter, second growth phase prepares the cell for division. Mitosis observation is also mentioned.
• 09:00 - 11:00: Mitosis Phases: Prophase The chapter titled 'Mitosis Phases: Prophase' focuses on the observation of cells undergoing rapid cell division. It highlights the use of the Whitefish blastula, an early embryonic stage of the organism, which is frequently utilized in biology courses to study cell division. The text also notes the high quality of images found in digital histology and offers practical advice for biology students.
• 11:00 - 15:00: Mitosis Phases: Metaphase The chapter discusses the importance of practical exams for students, which require demonstrating the application of conceptual knowledge to practical materials like models, preserved organic material, and microscope slides. The speaker emphasizes the necessity of examining various slides thoroughly for better preparation.
• 15:00 - 18:00: Mitosis Phases: Anaphase The chapter focuses on the process of mitosis, specifically the anaphase stage. It begins by discussing the quality concerns related to slide preparation, using the example of slides from white fish blastula tissue. Despite having about 30 slides, often only a small number, typically around six, are deemed useful due to poor quality assurance during manufacturing. This underscores challenges faced in observing and studying mitosis effectively through prepared slides, highlighting the importance of quality in biological study tools.
• 18:00 - 21:00: Mitosis Phases: Telophase and Cytokinesis The chapter titled 'Mitosis Phases: Telophase and Cytokinesis' discusses the final stages of mitosis. It highlights how visual representations, such as slides, vary in appearance due to differences in staining techniques, offering a close examination of these variations. The chapter encourages observing multiple examples to understand these phases better, though it suggests that some sections might not be essential for everyone.
• 21:00 - 24:00: Conclusion and Credits The chapter titled 'Conclusion and Credits' discusses the process involved in making histological slides, noting that it often involves some distortion such as shrinkage. The panel of images presented shows interphase with a particular focus on one cell where the shrinkage is evident. It highlights the irregular outlines of the nuclear envelope and cell membrane, which illustrate these distortions.

Histology - Mitosis (Whitefish Blastula) Transcription

• 00:00 - 00:30 [Music] foreign [Music] first I like to begin by gratefully acknowledging the source of the histo micrographs I will be using in this video and in future videos the website is digital histology and the website is under the auspices of Virginia Commonwealth University I provide the link to the website in the
• 00:30 - 01:00 description below here is the official attribution and Creative Commons license mitosis is part of the cell cycle which is basically the alternation of growth and or function with cell division here the cell cycle is schematically represented with the phases shown by arrows
• 01:00 - 01:30 no matter how fast or frequent this cycle mitosis is the shortest part of the cycle the term mitosis comes from a Greek word mitos which means thread this reflects the fact that during mitosis the chromosomes become visible and thread-like the remainder of the cell cycle is taken up by the phase between mitosis this in between phase is called
• 01:30 - 02:00 interphase interphase cannot be divided into histologically distinct phases in other words something that you can see or that can be seen however the activity in the Cell between mitosis can be divided into functional phases first we have the G1 phase which you can interpret as the first growth phase after cell division the cell needs to
• 02:00 - 02:30 grow before its next division otherwise it would just get smaller with each division the next phase is the S phase this is the phase of synthesis the chromosomes are duplicated during this phase finally before mitosis there is a second shorter growth phase in preparation for mitosis the easiest way to observe mitosis is to
• 02:30 - 03:00 find tissue where cells are undergoing rapid cell division the Whitefish blastula which is an early embryonic stage of the organism is commonly used in biology courses this panel of histomicrographs represents the excellent quality of the images found in digital histology but now I want to step aside for a second to give biology students some practical advice
• 03:00 - 03:30 practical advice is a bit of a pun because most of the people who view my videos are students who are preparing for a practical exam a practical exam is a type of exam where you demonstrate how well you can transfer conceptual knowledge to practical material including models preserved organic material and microscope slides when I was teaching I always told students that it was important to look at as many different slides as they
• 03:30 - 04:00 could the reason for this is that in a box of 30 or so slides on the same tissue like the white fish blastly only six at the most would be useful the rest of the slides would be kind of crappy the reason for this is that quality assurance of the slides that were manufactured left a lot to be desired so in short if your slide doesn't look
• 04:00 - 04:30 like the ones I'm going to show try looking at another one and as many as you can I'll stop now and you can skip over this segment of preaching in the future if you wish so here is a panel of excellent images but notice even with these excellent slides there is considerable variation in the staining again difference lines have different looks
• 04:30 - 05:00 so get familiar with the variation we begin with a panel of images that show interphase the process of making histological slides always involves some degree of distortion like shrinkage for example in the cell in the middle we see evidence of this shrinkage if we outline the nuclear envelope of the nucleus also notice that the cell membrane is irregular in outline again reflecting
• 05:00 - 05:30 shrinkage if we look closer at the material in the nucleus and the cytoplasm of the cell notice the coagulation of the macromolecules even to the extent that you see a gap between the cell membrane and what were the contents of the cytoplasm again this is Distortion these distortions are also referred to as artifacts
• 05:30 - 06:00 with all this unavoidable Distortion the cell and interphase has a nucleus with a clearly delineated nuclear envelope the material within the nucleus appears granular the granularity of this material reflects the fact that the chromosomes are Unwound or uncondensed so that the nuclear material is clumped in this fine granular pattern
• 06:00 - 06:30 the chromosomal material in this form in the nucleus is called chromatin in mitosis the equal division of the duplicated chromosomes can be divided into four phases the first phase is called prophase the prefix pro implies this because it means first or foremost this panel shows prophase from the earlier to the later stages
• 06:30 - 07:00 the earlier stages are on the left notice that the nuclear envelope is beginning to disintegrate and disappear and the chromatin has condensed as the chromosomes become more tightly wound upon themselves the nuclear envelope is practically gone in this cell and the chromosomal threads are further condensed and are picking up more of the blue hematoxylin stain
• 07:00 - 07:30 in this cell there is definitely an absence of a nuclear envelope and the thread-like nature of the chromosomes is apparent the cell no longer has its chromosomes in the form of Chromatin the first phase is imperceptibly followed by the phase that comes after or Beyond the prefix meta means after or Beyond
• 07:30 - 08:00 this phase is metaphase on the left again there is an earlier stage of metaphase now the threads are clearly visible also apparent in this cell or the locations of the centrosomes or centrioles which are also called the microtubule organizing centers the microtubules radiate outward from these centers like the Rays of a star and for this reason they are also called
• 08:00 - 08:30 astral fibers the cadets duplicated chromosomes remain attached to each other at a protein structure called a centromere each duplicated chromosome is called a chromatid when they are attached to each other in this way attach to the central mayor there is another protein structure called a kinetochore some of the microtubules that extend in the direction of these
• 08:30 - 09:00 paired chromatids will attach to the kinetochorus which now act as a kind of handle on the chromatids these microtubules are called kinetochore fibers or microcubules this is a cell at a later stage of metaphase note that this chromosomes are diametrically opposed and the fiber is
• 09:00 - 09:30 extending from each form an ellipsoid shape in between as they extend to the chromatids this configuration of fibers is called the spindle apparatus at this point the attached chromatids have moved to the center of the cell and are arranged like a disc or flat plate this is called the metaphase plate and
• 09:30 - 10:00 is characteristic of metaphase because it occupies the wide center of the spindle apparatus it is also called the equatorial plate the next phase is anaphase the prefix Anna means a part as in anatomy which means to cut apart during this phase the coveted separate and move to opposite poles
• 10:00 - 10:30 when the chromatids separate they are now chromosomes here is an early stage of this separation notice that there is now a space between the duplicated sets of chromosomes the spindle apparatus now has a definite spindle shape like a shape of an American football within this spindle there are
• 10:30 - 11:00 kinetochore microtubules or fibers these fibers are pulling the chromosomes of each duplicated set to either pull there are also non-kinetochore microtubules these microtubules as their name implies go past the chromosomes and interact with the fibers from the other side in a matter that pushes the chromosomes apart here is a later stage of anaphase
• 11:00 - 11:30 and here is yet a later stage the chromosomes are closer to their respective destinations and the microtubules of the spindle apparatus are visible in the space in between the Final Phase the end phase is telophase or telophase telophase is a prefix which means end
• 11:30 - 12:00 the chromosomes of either cell have arrived at their respective poles and are concentrated near the centrosomes another separate process is now evident if mitosis is going to result in two new cells the cytoplasm has to be divided this process is called cytokinesis cyto means cell and Kinesis implies movement this process begins during anaphase when
• 12:00 - 12:30 the cell membrane around the center of the cell constricts here this constriction is evidenced by the cell membrane that has appeared to divide the center of the spindle here is another nice example of the spindle fibers appearing to cross the cell membrane here the spindle fibers are no longer
• 12:30 - 13:00 apparent but the symmetric condensation of the chromosomes in the absence of a nuclear envelope clearly indicates telophase during late telophase the nuclear envelope reforms around the respective chromosomes this brings my first histology video to an end again this video would not be possible without the generosity of digital
• 13:00 - 13:30 histology I hope to produce more histology videos in the future please support me by subscribing and liking and any kind comments that you have keep me going down below there is a link to the digital histology website where you can find more study material including quizzes there is also a link to a quiz that I made and finally because of the assistance of
• 13:30 - 14:00 my daughter Marie here is yet another cat video [Music]