Cell life and death Flashcards by Ailish Kemble

What are the 10 features of a human cell?

Cell membrane
mitochondrion
ribosome
cytoplasm
golgi
centriole
lysosome
smooth endoplasmic reticulum
RER
Nucleus

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Where does it all start?

Fertilised ovum can become any kind of cell- embryonic stem cells
Adult stem cells more restricted- already in relevant organs

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What are the 3 adult cell types?

Labile
Stable
Permanent

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What are Labile cells?

Very high turnover
Bowel, skin (including epithelia of mucosal surfaces), bone marrow (mucosae= mucous membrane= where the outside touches us)

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What are Stable cells?

Good ability to regenerate but lower turnover
Hepatocytes (3 months), bone

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What are permanent cells?

Once its gone, its gone and cell loss is replaced by scarring
Nerve cells, cardiac muscle cells and skeletal muscle cells

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What are the 3 key potential cell fates?

Proliferation
Differentiation
Apoptosis

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What is Mitosis?

Process by which a cell replicates its chromosomes and then separates them, producing two identical nuclei in preparation for cell division

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What is the cell cycle?

Events that cells go through to grow, replicate their DNA and divide

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What is G1?

Cell growth

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What is S?

DNA synthesis

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What is G2?

More growth, preparation for mitosis

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What are the 4 stages in mitosis?

Prophase
Metaphase
Anaphase
Telophase

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What is DNA around histones?

Chromatin fibre

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What is supercoiled chromatin?

Chromosome

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What is Jargon?

chromatin
chromosome
chromatids

What do you have at the end of interphase?

All 46 chromosomes have been replicated ready for mitosis so you have 92 chromatids

What is M phase?

mitosis
Ends with cytokinesis

What is Meiosis?

Type of cell division that results in 4 daughter cells each with half the number of chromosomes of the parent cell
Makes sperm and egg cells which have 23 chromosomes

Why is Meiosis tricky?

Goes through PMAT twice, as chromosomes need to mix up

What is P1?

Crossing over of your bio mums + dads chromosomes makes “recombinant chromsomes”

What happens at the end of Telophase 1?

We have two cells with the same number of chromosomes in as we had at the start- but the genes in there are different. Meiosis 2 splits those two into two= four

What happens in spermatogenesis?

Spermatogonium— primary spermatocyte—- meiosis 1 so secondary spermatocyte formed— meiosis 2 forms round spermatid—— spermatozoa

When does meiosis start and how many sperm per day?

At puberty & basically never ends
50 mill sperm a day, lots will be wonky

What happens in female meiosis?

- oogonia fromed from mitosis in female embryo- germinal epithelium (where oogonium comes from) - Oogonium develops to primary oocyte- arrested in P1 - Puberty- release of FSH- completion of M1, forms a secondary oocyte (arrested @ metaphase of M2) - Ovulation- secondary released - Fertilisation completes meiosis - Only one haploid cell- other degenerate as polar bodies - One egg per month after puberty - Born with eggs - Pauses in meiosis

What is apoptosis?

Programmed cell death, that doesn't release harmful products or cause inflammation. Tidying up sculpting

What is apoptosis triggered by?

Intracellular signals e.g. DNA damage/defect detected in the cell cycle Extracellular signals e.g. signals from other cells, changes in growth factors

What is the intrinsic pathway of apoptosis?

relies on the balance between pro (Bax) and anti (Bcl-2) apoptotic proteins, which acts as a switch and leads to Caspase activation

What is the extrinsic pathway of apoptosis?

Death receptors are activated and this activates Caspases Caspases chop up the cytoskeleton, nuclear proteins and DNA As the cell shrinks its eaten by phagocytes (macrophages/ neutrophils) Little bits left= apoptotic bodies All remain cell membrane bound, so no inflammation is triggered. Tidy

What is the clinical relevance of apoptosis?

Defective apoptosis is important in tumour formation, and some viruses enhance their survival by inhibiting apoptosis of cells they infect Also syndactyly, cleft palate, spina bifida

What is Necrosis?

Unintended cell death in response to injury. People are large groups of cells, what kills cells, kills people Spillage of cell contents leads to activation of inflammatory pathways

What are the 4 parts of the inflammatory pathway?

Rubor= redness Calor= heat Tumor= swelling Dolor= pain

What are the 5 types of necrosis?

Coagulative Liquefactive Caseous "cheese like" Gangrene Fat necrosis

What is coagulative necrosis?

Ischaemia (inadequate blood supply) which invariably leads to hypoxia (lack of oxygen) to tissues. Initially cells don't look different, but once clear up cells come in (macrophages) to digest the necrotic cells, the tissues get soft BIG HEART ATTACK?= day 3-5 worry about heart wall rupture

What is Liquefactive necrosis?

the dying cells have little supporting tissue, so liquefy. Brain tissue, holes (cavities) left

What is Caseous necrosis?

Dead tissue walled off, cells break down but are not eaten by phagocytosis, so they clump together. Example= TB

What is Gangrene necrosis?

Tissue rot, go black from iron deposition from degrading haemoglobin i.e. Ischaemic limb/ "nec fasc".

What is Fat necrosis?

secondary to damage to fat from internal or external cause

What to do in cases of necrosis?

Debride and graft Support Antibiotics